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Tachyarrhythmias
Kinds of Tachyarrhythmias Selected AbstractsAtrial Tachyarrhythmia: What is the Ideal Site for Successful Ablation?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2008GREGORY M. FRANCISCO M.D. No abstract is available for this article. [source] Cellular Mechanisms of Vagally Mediated Atrial Tachyarrhythmia in Isolated Arterially Perfused Canine Right AtriaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2002MASAMICHI HIROSE M.D. Mechanism of Vagally Mediated AT.Introduction: Increased vagal tone significantly enhances susceptibility to atrial fibrillation (AF); however, the cellular mechanisms responsible for vagally mediated AF are not completely understood. Methods and Results: In 12 isolated arterially perfused canine right atria, high-resolution optical mapping techniques were used to measure action potentials during control conditions, during intracardiac parasympathetic nerve stimulation (IPS; 30 to 50 Hz) as a surrogate for vagal stimulation, and during acetylcholine (ACh) infusion (10 to 30 ,M). During steady-state pacing, action potential duration was shorter during ACh infusion (43 ± 9 msec) than during IPS (78 ± 7 msec, P < 0.001) or control (129 ± 5 msec, P < 0.001). In contrast, repolarization gradients were larger during IPS (13 ± 3 msec/mm) than during ACh infusion (3 ± 1 msec/mm, P < 0.01) or control (5 ± 1 msec/mm, P < 0.01). Transmural repolarization gradients were relatively small for each intervention tested. During ACh infusion, atrial tachyarrhythmia (AT) was easily initiated with a single premature stimulus and was associated with a focal pattern of activation (84%). AT also was easily initiated by a single premature stimulus during IPS; however, when repolarization gradients were large, patterns of conduction block and incomplete macroreentry were often observed (64%). Importantly, AT initiation during IPS was associated with focal activity (36%) when repolarization gradients were small. Conclusion: In contrast to ACh infusion, IPS generally increased dispersion of repolarization and was often associated with patterns of conduction block and incomplete macroreentry, similar to that associated with in vivo cervical vagal stimulation. However, IPS also was associated with a focal pattern of initiation that was independent of local repolarization gradients. These results suggest that during vagal stimulation, AT initiation does not always depend on repolarization gradients. [source] Mechanisms of Preventive Effect of Nicorandil on Ischaemia-Induced Ventricular Tachyarrhythmia in Isolated Arterially Perfused Canine Left Ventricular WedgesBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 6 2008Masamichi Hirose We examined effects of nicorandil on the induction of VT during acute myocardial ischaemia. Optical action potentials were recorded from the entire transmural wall of arterially perfused canine left ventricular wedges. Ischaemia was produced by arterial occlusion for 20 min. During endocardial pacing, nicorandil shortened mean action potential duration (APD) in the transmural wall before ischaemia and further shortened it during ischaemia without increasing dispersion of APD. HMR1098, a selective blocker of sarcolemmal ATP-sensitive K+ channels, inhibited the shortening of APD by nicorandil before and during ischaemia. Ischaemia decreased transmural conduction velocity (CV). Nicorandil partially restored CV to a similar extent in the absence and presence of HMR1098. In contrast, HMR1098 did not suppress the ischaemic conduction slowing in the absence of nicorandil. Nicorandil suppressed the increased dispersion of local CV during ischaemia. Isochrone maps on the initiation of VT showed that reentry in the transmural surface resulted from the excitation of the epicardial region of transmural surface. Nicorandil significantly increased the size of non-excited area in the epicardial region of the transmural wall, thereby significantly reducing the incidence of VT induced during ischaemia. HMR1098 inhibited this effect of nicorandil. These results suggest that nicorandil prevents VT during acute global ischaemia primarily by augmenting the inactivation of epicardial muscle through the activation of sarcolemmal KATP channels. [source] Pulmonary Regurgitation after Tetralogy of Fallot Repair: Clinical Features, Sequelae, and Timing of Pulmonary Valve ReplacementCONGENITAL HEART DISEASE, Issue 6 2007Naser M. Ammash MD ABSTRACT Pulmonary regurgitation following repair of tetralogy of Fallot is a common postoperative sequela associated with progressive right ventricular enlargement, dysfunction, and is an important determinant of late morbidity and mortality. Although pulmonary regurgitation may be well tolerated for many years following surgery, it can be associated with progressive exercise intolerance, heart failure, tachyarrhythmia, and late sudden death. It also often necessitates re-intervention. Identifying the appropriate timing of such intervention could be very challenging given the risk of prosthetic valve degeneration and the increased risk of reoperation. Comprehensive informed and regular assessment of the postoperative patient with tetralogy of Fallot, including evaluation of pulmonary regurgitation, right heart structure and function, is crucial to the optimal care of these patients. Pulmonary valve replacement performed in an experienced tertiary referral center is associated with low operative morbidity and mortality and very good long-term results. Early results of percutaneous pulmonary valve replacement are also promising. [source] Electrosurgery, Pacemakers and ICDs: A Survey of Precautions and Complications Experienced by Cutaneous SurgeonsDERMATOLOGIC SURGERY, Issue 4 2001Hazem M. El-Gamal MD Background. Minimal information is available in the literature regarding the precautions implemented or complications experienced by cutaneous surgeons when electrosurgery is used in patients with pacemakers or implantable cardioverter-defibrillators (ICDs). The literature pertinent to dermatologists is primarily based on experiences of other surgical specialties and a generally recommended thorough perioperative evaluation. Objective. To determine what precautions are currently taken by cutaneous surgeons in patients with pacemakers or ICDs, and what types of complications have occurred due to electrosurgery in a dermatologic setting. Methods. In the winter of 2000, a survey was mailed to 419 U.S.-based members of the American College of Mohs Micrographic Surgery and Cutaneous Oncology (ACMMSCO). Results. A total of 166 (40%) surveys were returned. Routine precautions included utilizing short bursts of less than 5 seconds (71%), use of minimal power (61%), and avoiding use around the pacemaker or ICD (57%). The types of interference reported were skipped beats (eight patients), reprogramming of a pacemaker (six patients), firing of an ICD (four patients), asystole (three patients), bradycardia (two patients), depleted battery life of a pacemaker (one patient), and an unspecified tachyarrhythmia (one patient). Overall there was a low rate of complications (0.8 cases/100 years of surgical practice), with no reported significant morbidity or mortality. Bipolar forceps were utilized by 19% of respondents and were not associated with any incidences of interference. Conclusions. Significant interference to pacemakers or ICDs rarely results from office-based electrosurgery. No clear community practice standards regarding precautions was evident from this survey. The use of bipolar forceps or true electrocautery are the better options when electrosurgey is required. These two modalities may necessitate fewer perioperative precautions than generally recommended, without compromising patient safety. [source] Electrophysiological study of infant and adult rats under acute intoxication with fluoroacetamideJOURNAL OF APPLIED TOXICOLOGY, Issue 6 2007Sergey V. Kuznetsov Abstract A study was conducted of acute intoxication of infant and adult Wistar rats with fluoroacetamide (FAA), an inhibitor of oxidative metabolism. FAA was administered orally to adult rats at 1/2 LD50 and subcutaneously to infant rats at LD100 or 1/10 LD50. Electrocardiogram (ECG), respiration and motor activity were registered for 7 days. Clinical analysis of ECG and the heart rate variability (HRV) was carried out to assess the state of the vegetative nervous system. In adult rats, FAA caused marked disturbances in the activity of cardiovascular and respiratory systems, including the development of a potentially lethal acute cor pulmonale. Conversely, there were no significant changes of cardiac function and respiration in infant rats; they died because of extreme emaciation accompanied by retardation of development. In adult rats, bursts of associated cardiac and respiratory tachyarrhythmia, as well as regular high amplitude spasmodic sighs having a deca-second rhythm were observed. In both infant and adult rats, FAA caused short-term enhancement of humoral (metabolic) and sympathetic activities, followed by a gradual and stable predominance of parasympathetic influence on HRV. Under conditions of FAA inhibition of the tricarboxylic acid cycle, the observed physiological reactions may be explained by activation of alternative metabolic pathways. This is also supported by a lack of ontogenetically caused inhibition of spontaneous motor activity in infant rats poisoned with FAA, which highlights the significance of the alternative metabolic pathways for implementation of deca-second and minute rhythms and a lack of a rigid dependence of these rhythms upon activity of neuronal networks. Copyright © 2007 John Wiley & Sons, Ltd. [source] Dynamic Registration of Preablation Imaging With a Catheter Geometry to Guide Ablation in a Swine Model: Validation of Image Integration and Assessment of Catheter Navigation AccuracyJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2010J. JASON WEST M.D. Image Integration with a Catheter Mapping System.,Background: Catheter ablation of atrial and ventricular tachyarrhythmia involves anatomically based cardiac ablation strategies. CT and MRI images provide the most detailed cardiac anatomy available. Integration of these images into a mapping system should produce detailed and accurate models suitable to guide ablation. Objective: The purpose of this study was to validate and assess the accuracy of a novel CT and MRI image integration algorithm designed to facilitate catheter navigation and ablation. Methods: Using a lateral thoracotomy, markers were sutured to the epicardial surface of each cardiac chamber in 12 swine. Detailed CT/MRI anatomy was imported into the mapping system. The CT/MRI image was then integrated with a detailed catheter geometry of the relevant chamber using a new image integration algorithm. The epicardial markers, identified from the CT/MRI images, were then displayed on the surface of the integrated image. Guided only by the integrated CT/MRI, a single RF lesion was directed at the corresponding endocardial site for each epicardial marker. At autopsy, the distance from the endocardial RF lesion to the target site was assessed. Results: The mean position error (CT/MRI) for the left atrium was 2.5 ± 2.4 mm/5.1 ± 3.9 mm, for the right atrium 6.2 ± 6.5 mm/4.3 ± 2.2 mm, for the right ventricle 6.2 ± 4.3 mm/6.6 ± 5.3 mm, and for the left ventricle 4.7 ± 3.4 mm/3.1 ± 2.7 mm. There was no cardiac perforation or tamponade. Conclusion: CT and MRI images can be effectively utilized for catheter navigation when integrated into a mapping system. This novel registration module with dynamic registration provides effective guidance for ablation. (J Cardiovasc Electrophysiol, Vol. 21, pp. 81,87, January 2010) [source] Improved Arrhythmia Detection in Implantable Loop RecordersJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2008MICHELE BRIGNOLE M.D. Introduction: Implantable loop recorders (ILR) have an automatic arrhythmia detection feature that can be compromised by inappropriately detected episodes. This study evaluated a new ILR sensing and detection scheme for automatically detecting asystole, bradyarrhythmia, and tachyarrhythmia events, which is implemented in the next generation device (Reveal DX/XT). Methods and Results: The new scheme employs an automatically adjusting R-wave sensing threshold, enhanced noise rejection, and algorithms to detect asystole, bradyarrhythmia, and tachyarrhythmia. Performance of the new algorithms was evaluated using 2,613 previously recorded, automatically detected Reveal Plus episodes from 533 patients. A total of 71.9% of episodes were inappropriately detected by the original ILR, and at least 88.6% of patients had one or more inappropriate episodes, with most inappropriate detections due to R-wave amplitude reductions, amplifier saturation, and T-wave oversensing. With the new scheme, inappropriate detections were reduced by 85.2% (P < 0.001), with a small reduction in the detection of appropriate episodes (1.7%, P < 0.001). The new scheme avoided inappropriate detections in 67.4% of patients that had them with the original scheme. Conclusions: The new sensing and detection scheme is expected to substantially reduce the occurrence of inappropriately detected episodes, relative to that of the original ILR. [source] Clustering of Ventricular Tachyarrhythmias in Heart Failure Patients Implanted with a Biventricular Cardioverter DefibrillatorJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2006MAURIZIO LUNATI M.D. Background: Temporal patterns of ventricular tachyarrhythmia (VT/VF) have been studied only in patients who have received implantable cardioverter defibrillators (ICD) for secondary prevention of sudden death, and mainly in ischemic patients. The aim of this study was to evaluate VT/VF recurrence patterns in heart failure (HF) patients with biventricular ICD and to stratify results according to HF etiology and ICD indication. Methods and Results: We studied 421 patients (91% male, 66 ± 9 years). HF etiology was ischemic in 292 patients and nonischemic in 129. ICD indication was for primary prevention in 227 patients and secondary prevention in 194. Baseline left ventricular ejection fraction (LVEF) was 26 ± 7%, QRS duration 168 ± 32 msec, and NYHA class 2.9 ± 0.6. In a follow-up of 19 ± 11 months, 1,838 VT/VF in 110 patients were appropriately detected. In 59 patients who had ,4 episodes, we tried to determine whether VT/VF occurred randomly or rather tended to cluster by fitting the frequency distribution of tachycardia interdetection intervals with exponential functions: VT/VF clusters were observed in 46 patients (78% of the subgroup of patients with ,4 episodes and 11% of the overall population). On multivariate logistic analysis, VT/VF clusters were significantly (P < 0.01) associated with ICD indication for secondary prevention (odds ratio [OR]= 3.12; confidence interval [CI]= 1.56,6.92), nonischemic HF etiology (OR = 4.34; CI = 2.02,9.32), monomorphic VT (OR = 4.96; CI = 2.28,10.8), and LVEF < 25% (OR = 3.34; CI = 1.54,7.23). Cardiovascular hospitalizations and deaths occurred more frequently in cluster (21/46 [46%]) than in noncluster patients (63/375 (17%), P < 0.0001). Conclusions: In HF patients with biventricular ICDs, VT/VF clusters may be regarded as the epiphenomenon of HF deterioration or as a marker of suboptimal response to cardiac resynchronization therapy. [source] A Single Pulmonary Vein as Electrophysiological Substrate of Paroxysmal Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2006HE HUANG M.D. Introduction: It has been demonstrated that pulmonary veins (PVs) play an important role in initiation and maintenance of paroxysmal atrial fibrillation (AF). However, it is not clearly known whether a single PV acts as electrophysiological substrate for paroxysmal AF. Methods and Results: This study included five patients with paroxysmal AF. All patients underwent complete PV isolation with continuous circular lesions (CCLs) around the ipsilateral PVs guided by a three-dimensional mapping system. Irrigated radiofrequency (RF) delivery was performed during AF on the right-sided CCLs in two patients and on the left-sided CCLs in three patients. The incomplete CCLs resulted in a change from AF to atrial tachycardia (AT), which presented with an identical atrial activation sequence and P wave morphology. Complete CCLs resulted in AF termination with persistent PV tachyarrhythmias within the isolated PV in all five patients. PV tachyarrhythmia within the isolated PV was PV fibrillation from the left common PV (LCPV) in two patients, PV tachycardia from the right superior PV (RSPV) in two patients, and from the left superior PV in one patient. All sustained PV tachyarrhythmias persisted for more than 30 minutes, needed external cardioversion for termination in four patients and a focal ablation in one patient. After the initial procedure, an AT from the RSPV occurred in a patient with PV fibrillation within the LCPV, and was successfully ablated. Conclusion: In patients with paroxysmal AF, sustained PV tachyarrhythmias from a single PV can perpetuate AF. Complete isolation of all PV may provide good clinical outcome during long-term follow-up. [source] Electrocardiographic and Electrophysiologic Characteristics of Midseptal Accessory PathwaysJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2005SHIH-LING CHANG M.D. Background: The purpose of the present study was to investigate the electrocardiographic and electrophysiologic characteristics of right midseptal (RMS) and left midseptal (LMS) accessory pathways (APs), and to develop a stepwise algorithm to differentiate RMS from LMS APs. Methods and Results: From May 1989 to February 2004, 1591 patients with AP-mediated tachyarrhythmia underwent RF catheter ablation in this institution, and 38 (2.4%) patients had MS APs. The delta wave and precordial QRS transition during sinus rhythm, retrograde P wave during orthodromic tachycardia, and electrophysiologic characteristic and catheter ablation in 30 patients with RMS APs and 8 patients with LMS APs were analyzed. There was no significant difference in electrophysiologic characteristics and catheter ablation between RMS and LMS APs. The polarity of retrograde P wave during orthodromic tachycardia also showed no statistical difference between patients with RMS and LMS APs. The delta wave polarity was positive in leads I, aVL, and V3 to V6 in patients with RMS and LMS APs. Patients with LMS APs had a higher incidence of biphasic delta wave in lead V1 than patients with RMS APs (80% vs. 15%, P = 0.012). The distributions of precordial QRS transition were different between RMS APs (leads V2; n = 10, V3; n = 7 and V4; n = 3) and LMS APs (leads V1; n = 1 and V2; n = 4) (P = 0.03). The combination of a delta negative wave in lead V1 or precordial QRS transition in lead V3 or V4 had a sensitivity of 90%, specificity of 80%, positive predictive value of 95%, and negative predictive value of 66% in predicting an RMS AP. Conclusions: Delta wave polarity in lead V1 and precordial QRS transition may differentiate RMS and LMS APs. [source] Restitution Properties and Occurrence of Ventricular Arrhythmia in LQT2 Type of Long QT SyndromeJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2002SOU YAMAUCHI M.D. Mechanisms of Ventricular Arrhythmia in LQT2 Heart.Introduction: The aim of this study was to clarify the ventricular tachyarrhythmia mechanism induced by the IKr -blocking agent E4031, simulating the LQT2 form. Electrophysiologic properties were examined in 13 canines before and after administration of E4031. Method and Results: Thirty-six needle electrodes were inserted into the anterior left ventricular wall. From each needle, local unipolar electrograms were obtained from four intramural sites. Activation time (AT) and activation-recovery interval (ARI) were measured. To evaluate the susceptibility to ventricular arrhythmia, intramural ARI dispersions and the restitution relationship between ARI and diastolic interval were calculated. After E4031 administration, ARI prolonged uniformly in each myocardial layer. However, ARI dispersion was not augmented compared with control. The slope of the ARI restitution curve after E4031 was significantly steeper than control. A steep slope may result from augmented ARI alternans. In 11 of the 13 canines, ventricular tachyarrhythmia was induced by programmed stimulation after E4031, whereas no arrhythmia was induced by the same protocol in control. Conclusion: Steepness of electrical restitution may play a major role in arrhythmogenicity in LQT2 hearts. [source] Cellular Mechanisms of Vagally Mediated Atrial Tachyarrhythmia in Isolated Arterially Perfused Canine Right AtriaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2002MASAMICHI HIROSE M.D. Mechanism of Vagally Mediated AT.Introduction: Increased vagal tone significantly enhances susceptibility to atrial fibrillation (AF); however, the cellular mechanisms responsible for vagally mediated AF are not completely understood. Methods and Results: In 12 isolated arterially perfused canine right atria, high-resolution optical mapping techniques were used to measure action potentials during control conditions, during intracardiac parasympathetic nerve stimulation (IPS; 30 to 50 Hz) as a surrogate for vagal stimulation, and during acetylcholine (ACh) infusion (10 to 30 ,M). During steady-state pacing, action potential duration was shorter during ACh infusion (43 ± 9 msec) than during IPS (78 ± 7 msec, P < 0.001) or control (129 ± 5 msec, P < 0.001). In contrast, repolarization gradients were larger during IPS (13 ± 3 msec/mm) than during ACh infusion (3 ± 1 msec/mm, P < 0.01) or control (5 ± 1 msec/mm, P < 0.01). Transmural repolarization gradients were relatively small for each intervention tested. During ACh infusion, atrial tachyarrhythmia (AT) was easily initiated with a single premature stimulus and was associated with a focal pattern of activation (84%). AT also was easily initiated by a single premature stimulus during IPS; however, when repolarization gradients were large, patterns of conduction block and incomplete macroreentry were often observed (64%). Importantly, AT initiation during IPS was associated with focal activity (36%) when repolarization gradients were small. Conclusion: In contrast to ACh infusion, IPS generally increased dispersion of repolarization and was often associated with patterns of conduction block and incomplete macroreentry, similar to that associated with in vivo cervical vagal stimulation. However, IPS also was associated with a focal pattern of initiation that was independent of local repolarization gradients. These results suggest that during vagal stimulation, AT initiation does not always depend on repolarization gradients. [source] Arrhythmogenesis of T Wave Alternans Associated with Surface QRS Complex Alternans and the Role of Ventricular Prematurity: Observations from a Canine Model of LQT3 SyndromeJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2002MASAOMI CHINUSHI M.D. Intramural TWA and Its Arrhythmogenesis.Introduction: T wave alternans (TWA) is characterized by cycle-to-cycle changes in the QT interval and/or T wave morphology. It is believed to amplify the underlying dispersion of ventricular repolarization. The aim of this study was to examine the mechanisms and arrhythmogenesis of TWA accompanied by QRS complex and/or blood pressure (BP) waveform alternans, using transmural ventricular electrogram recordings in an anthopleurin-A model of long QT syndrome. Methods and Results: The cardiac cycle length was gradually shortened by interruption of vagal stimulation, and TWA was induced in six canine hearts. Transmural unipolar electrograms were recorded with plunge needle electrodes from endocardial (Endo), mid-myocardial (Mid), and epicardial (Epi) sites, along with the surface ECG and BP. The activation-recovery interval (ARI) was measured to estimate local refractoriness. During TWA, ARI alternans was greater at the Mid than the Epi/Endo sites, and it was associated with the development of marked spatial dispersion of ventricular repolarization. As TWA increased, ventricular activation of the cycles associated with shorter QT intervals displayed delayed conduction at the Mid sites as a result of a critically longer ARI of the preceding cycle and longer QT interval, while normal conduction was preserved at the Epi site. Delayed conduction at the Mid sites manifested as surface ECG QRS and BP waveform alternans, and spontaneous ventricular tachyarrhythmias developed in absence of ventricular prematurity. In other instances, in absence of delayed conduction during TWA, ventricular premature complexes infringed on a prominent spatial dispersion of ventricular repolarization of cycles with long QT intervals and initiated ventricular tachyarrhythmia. Conclusion: TWA accompanied by QRS alternans may signal a greater ventricular electrical instability, since it is associated with intramural delayed conduction, which can initiate ventricular tachyarrhythmia without ventricular premature complexes. [source] Distribution of Patients, Paroxysmal Atrial Tachyarrhythmia Episodes: Implications for Detection of Treatment EfficacyJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2001WILLIAM F. KAEMMERER Ph.D. Distribution of Paroxysmal Atrial Tachyarrhythmia Episodes.Introduction: Clinical trials of treatments for paroxysmal atrial tachyarrhythmia (pAT) often compare different treatment groups using the time to first episode recurrence. This approach assumes that the time to the first recurrence is representative of all times between successive episodes in a given patient. We subjected this assumption to an empiric test. Methods and Results: Records of pAT onsets from a chronologic series of 134 patients with dual chamber implantable defibrillators were analyzed; 14 had experienced > 10 pAT episodes, which is sufficient for meaningful statistical modeling of the time intervals between episodes. Episodes were independent and randomly distributed in 9 of 14 patients, but a fit of the data to an exponential distribution, required by the stated assumption, was rejected in 13 of 14. In contrast, a Weibull distribution yielded an adequate goodness of fit in 5 of the 9 cases with independent and randomly distributed data. Monte Carlo methods were used to determine the impact of violations of the exponential distribution assumption on clinical trials using time from cardioversion to first episode recurrence as the dependent measure. In a parallel groups design, substantial loss of power occurs with sample sizes < 500 patients per group. In a cross-over design, there is insufficient power to detect a 30% reduction in episode frequency even with 300 patients. Conclusion: Clinical trials that rely on time to first episode recurrence may be considerably less able to detect efficacious treatments than may have been supposed. Analysis of multiple episode onsets recorded over time should be used to avoid this pitfall. [source] Organophosphate poisoning complicated by a tachyarrhythmia and acute respiratory distress syndrome in a childJOURNAL OF PAEDIATRICS AND CHILD HEALTH, Issue 5 2002L Nel Abstract: A 9-year-old child presented with documented organophosphate insecticide poisoning. His course was initially complicated by a tachyarrhythmia with QT-interval prolongation that responded promptly to intravenous magnesium. However, following partial recovery, he developed progressive acute respiratory distress syndrome characterized by irreversible fibrosis and obliteration of the lung parenchyma. [source] Drug-induced block of cardiac HERG potassium channels and development of torsade de pointes arrhythmias: the case of antipsychoticsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 2 2005Vincenzo Calderone The prolongation of the cardiac repolarization process, a result of the blocking of the Human Ether-a-go-go Related Gene potassium channel, is an undesired accessory property shared by many pharmacological classes of non-cardiovascular drugs. Often the delayed cardiac repolarization process can be identified by a prolongation of the QT interval of the electrocardiograph. In these conditions, premature action potentials can trigger a dangerous polymorphic ventricular tachyarrhythmia, known as torsade de pointes, which occasionally can result in lethal ventricular fibrillation. In this work, brief descriptions of the electrophysiological basis of torsade de pointes and of the several pharmacological classes of torsadogenic drugs are given. Attention is focused on antipsychotics, with a deeper overview on the experimental and clinical reports about their torsadogenic properties. [source] Dual pulse intestinal electrical stimulation normalizes intestinal dysrhythmia and improves symptoms induced by vasopressin in fed state in dogsNEUROGASTROENTEROLOGY & MOTILITY, Issue 5 2007H. Qi Abstract, To assess effects of dual pulse intestinal electrical stimulation (DPIES) on intestinal dysrhythmia and motility, and symptoms induced by vasopressin in conscious dogs. The study was performed in three postprandial sessions (control; vasopressin; DPIES) in six dogs with two pairs of electrodes chronically implanted on the serosal surface of the proximal jejunum and with a chronic duodenal fistula. A manometric catheter was advanced into the small intestine via the intestinal cannula. Motility and intestinal slow waves were recorded. Symptoms were assessed. During vasopressin infusion, the percentage of normal intestinal slow wave frequency was decreased (P < 0.01), reflected as a significant increase in the percentage of both bradygastria and tachygastria; the motility index decreased (P < 0.01) and the symptom score increased (P < 0.01). In the session of DPIES, the percentage of normal slow wave frequency was recovered (P < 0.05 vs vasopressin), attributed to a reduction in both bradyarrhythmia and tachyarrhythmia; the symptom score was reduced (P < 0.05 vs vasopressin); the motility index was not significantly increased. These results suggest that vasopressin induces intestinal dysrhythmia and emetic symptoms and inhibits intestinal motility. Dual pulse intestinal electrical stimulation is capable of improving intestinal dysrhythmia and emetic symptoms but not impaired intestinal motility induced by vasopressin. [source] A Rare type of Ventricular Oversensing in ICD Therapy,Inappropriate ICD Shock Delivery Due to Triple CountingPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2010MICHAEL GUENTHER M.D. Irregular sensing by triple counting of wide QRS complexes resulted in inappropriate shocks in a patient with a biventricular implantable cardioverter defibrillator (ICD): A 66-year-old male patient with ischemic cardiomyopathy, left bundle branch block, and impaired left ventricular function received a biventricular ICD for optimal therapy of heart failure (CHF). Two years after implantation, the patient experienced recurrent unexpected ICD shocks without clinical symptoms of malignant tachyarrhythmia, or worsened CHF. The patient's condition rapidly worsened, with progressive cardiogenic shock and electrical,mechanical dissociation. After unsuccessful resuscitation of the patient the interrogation of the ICD showed an initial triple counting of extremely wide and fragmented QRS complexes with inappropriate shocks. (PACE 2010; 33:e17,e19) [source] Recurrent Ventricular Tachycardia in Patient with Friedreich's Ataxia in the Absence of Clinical Myocardial DiseasePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2010NIDAL ASAAD M.B.B.S. We report a 33-year-old man with recurrent loss of consciousness due to ventricular tachyarrhythmia with a history of Friedreich's ataxia. The patient's symptom was improved after implantation of a single-lead implantable cardiac defibrillator. The clinical, genetic, echocardiographic, and electrocardiographic features are discussed in brief. (PACE 2010; 33:109,112) [source] Feasibility of Magnetic Resonance Imaging in Patients with an Implantable Loop RecorderPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 3 2008JORGE A. WONG M.D. Background: The implantable loop recorder (ILR) is a useful tool in the diagnosis of syncope. Our understanding of their functional and safety profile in interfering environments such as magnetic resonance imaging (MRI) becomes increasingly important as they become more prevalent. Methods: We report four patients with an ILR who underwent MRI. The ILR memory was cleared before MRI and no changes were made to programmed settings. Device interrogation took place immediately after the scan. Patients were surveyed for device movement and heating, in addition to cardiopulmonary symptoms after their MRI. Results: Following MRI scanning, all patients were asymptomatic and no device movement or heating was observed. In addition, the functionality of the device remained unaffected. Artifacts mimicking arrhythmias were seen in all ILR patients regardless of the type of MRI scan. Conclusions: MRI scanning of ILR patients can be performed without harm to patient or device, but artifacts that could be mistaken for a tachyarrhythmia are seen frequently. [source] Ineffectiveness of Precordial Thump for Cardioversion of Malignant Ventricular TachyarrhythmiasPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2007OFFER AMIR M.D. Background:The Precordial Thump (PT) is commonly used for cardiopulmonary resuscitations both in and out of hospitals. However, the support for its efficiency relies mainly on sporadic cases. In this current prospective large study, we tested the effectiveness and safety of PT in a wide range of malignant ventricular tachyarrhythmias. Methods: The study included 80 patients who underwent electrophysiological study and/or implantation of a cardiodefibrillator device. During these procedures, once a malignant ventricular tachyarrhythmia was induced, PT was used as the first treatment option. If the PT failed, other means were used to discontinue the arrhythmia. Results: Polymorphic ventricular tachycardia occurred in 32 (40%) patients, ventricular fibrillation in 28 (35%) patients, and 20 (25%) patients had sustained monomorphic ventricular tachycardia. Except in one patient with monomorphic ventricular tachycardia, the PT was unsuccessful in terminating any of the other malignant tachyarrhythmias, and internal or external defibrillation was eventually required in all other 79 (99%) patients. The PT was not associated with any damage either to the sternal bone, ribs, or to the cardiodefibrillator device. Conclusions: PT is not effective in terminating malignant ventricular tachyarrhythmia and should be reserved to a situation in which a defibrillator is not available. [source] Temporary Disturbances of the QT Interval Precede the Onset of Ventricular Tachyarrhythmias in Patients with Structural Heart DiseasesPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2002BJÖRN HENRIK DIEM DIEM, B.H. et al.: Temporary Disturbances of the QT Interval Precede the Onset of Ventricular Tach-yarrhythmias in Patients with Structural Heart Diseases. An increase in sinus rate prior to ventricular tachyarrhythmias has been demonstrated in previous studies. There is no clear data available concerning changes in ventricular de- and repolarization prior to ventricular tachyarrhythmias, especially in patients with structural heart disease. Therefore, the aim of this study was to analyze the QT and QTc interval (Bazett's formula immediately before the onset of ventricular tachyarrhythmias in stored electrograms of patients with ICDs. The study analyzed 228 spontaneous ventricular tachyarrhythmia episodes in 52 patients (mean age 64 ± 10 years, 49 men, 3 women) and compared them with 146 electrograms of baseline rhythm recorded during regular ICD follow-up. Mean ventricular cycle length (CL), QT interval, and QTc were measured before the onset of ventricular tachyarrhythmia and during baseline rhythm. Prior to ventricular tachyarrhythmias onset, CL was significantly shorter than during baseline rhythm (714 ± 139 vs 828 ± 149 ms, P < 0.0001). By contrast, the QT interval (430 ± 67 ms) and QTc interval (518 ± 67 ms) were significantly prolonged before the onset of ventricular tachyarrhythmias as compared to baseline rhythm (QT 406 ± 67 ms, QTc 450 ± 61 ms; P < 0.0001). CL, QT, and QTc changes were independent of concomitant treatment with antiarrhythmic drugs. Ventricular tachyarrhythmias are preceded by a significant prolongation of the QT and QTc intervals. This phenomenon may represent a greater than normal disparity of repolarization recovery times possibly facilitating the development of ventricular tachyarrhythmias. [source] Automatic Mode Switching of Implantable Pacemakers: I. Principles of Instrumentation, Clinical, and Hemodynamic ConsiderationsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2002CHU-PAK LAU LAU, C.-P., et al.: Automatic Mode Switching of Implantable Pacemakers: I. Principles of Instrumentation, Clinical, and Hemodynamic Considerations. Automatic mode switching (AMS) is now a programmable function in most contemporary dual chamber pacemakers. Atrial tachyarrhythmias are detected when the sensed atrial rate exceeds a "rate-cutoff,""running average,""sensor-based physiological" rate, or using "complex" detection algorithms. AMS algorithms differ in their atrial tachyarrhythmia detection method, sensitivity, and specificity and, thus, respond differently to atrial tachyarrhythmia in terms of speed to the AMS onset, rate stability of the response, and speed to resynchronize to sinus rhythm. AMS is hemodynamically beneficial, and most patients with atrial tachyarrhythmias are symptomatically better with an AMS algorithm in their pacemakers. New diagnostic capabilities of pacemaker especially stored electrograms not only allow programming of the AMS function, but enable quantification of atrial fibrillation burden that facilitate clinical management of patients with implantable devices who have concomitant atrial tachyarrhythmia. [source] AAIR Versus DDDR Pacing in the Bradycardia Tachycardia Syndrome: A Prospective, Randomized, Double-blind, Crossover TrialPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2001BERNHARD SCHWAAB SCHWABB, B., et al.: AAIR Versus DDDR Pacing in the Bradycardia Tachycardia Syndrome: A Prospective, Randomized, Double-blind, Crossover Trial. In 19 patients paced and medicated for bradycardia tachycardia syndrome (BTS), AAIR and DDDR pacing were compared with regard to quality of life (QoL), atrial tachyarrhythmia (AFib), exercise tolerance, and left ventricular (LV) function. Patients had a PQ interval , 240 ms during sinus rhythm, no second or third degree AV block, no bundle branch block, or bifascicular block. In DDDR mode, AV delay was optimized using the aortic time velocity integral. After 3 months, QoL was assessed by questionnaires, patients were investigated by 24-hour Holter, cardiopulmonary exercise testing (CPX) was performed, and LV function was determined by echocardiography. QoL was similar in all dimensions, except dizziness, showing a significantly lower prevalence in AAIR mode. The incidence of AFib was 12 episodes in 2 patients with AAIR versus 22 episodes in 7 patients with DDDR pacing (P = 0.072). In AAIR mode, 164 events of second and third degree AV block were detected in 7 patients (37%) with pauses between 1 and 4 seconds. During CPX, exercise duration and work load were higher in AAIR than in DDDR mode (423 ± 127 vs 402 ± 102 s and 103 ± 31 vs 96 ± 27 Watt, P < 0.05). Oxygen consumption (VO2), was similar in both modes. During echocardiography, only deceleration of early diastolic flow velocity and early diastolic closure rate of the anterior mitral valve leaflet were higher in DDD than in AAI pacing (5.16 ± 1.35 vs 3.56 ± 0.95 m/s2 and 69.2 ± 23 vs 54.1 ± 26 mm/s, P < 0.05). As preferred pacing mode, 11 patients chose DDDR, 8 patients chose AAIR. Hence, AAIR and DDDR pacing seem to be equally effective in BTS patients. In view of a considerable rate of high degree AV block during AAIR pacing, DDDR mode should be preferred for safety reasons. [source] Characteristic changes in the physiological components of cybersicknessPSYCHOPHYSIOLOGY, Issue 5 2005Young Youn Kim Abstract We investigated the characteristic changes in the physiology of cybersickness when subjects were exposed to virtual reality. Sixty-one participants experienced a virtual navigation for a total of 9.5 min, and were required to detect specific virtual objects. Three questionnaires for sickness susceptibility and immersive tendency were obtained before the navigation. Sixteen electrophysiological signals were recorded before, during, and after the navigation. The severity of cybersickness experienced by participants was reported from a simulator sickness questionnaire after the navigation. The total severity of cybersickness had a significant positive correlation with gastric tachyarrhythmia, eyeblink rate, heart period, and EEG delta wave and a negative correlation with EEG beta wave. These results suggest that cybersickness accompanies the pattern changes in the activities of the central and the autonomic nervous systems. [source] Impact of QT Variables on Clinical Outcome of Genotyped Hypertrophic CardiomyopathyANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2009Katsuharu Uchiyama M.D. Background: Although QT variables such as its interval and/or dispersion can be clinical markers of ventricular tachyarrhythmia, few data exist regarding the role of QT variables in genotyped hypertrophic cardiomyopathy (HCM). Therefore, we analyzed QT variables in genotyped subjects with or without left ventricular hypertrophy (LVH). Methods: QT variables were analyzed in 111 mutation and 43 non-mutation carriers who were divided into three groups: A, those without ECG abnormalities and echocardiographically determined LVH (wall thickness ,13 mm); B, those with ECG abnormalities but LVH; and C, those with ECG abnormalities and LVH. We also examined clinical outcome of enrolled patients. Results: Maximal LV wall thickness in group C (19.0 ± 4.3 mm, mean ±SD) was significantly greater than that in group A (9.2 ± 1.8) and group B (10.4 ± 1.8). Under these conditions, maximum QTc interval and QT dispersion were significantly longer in group C than those in group A (438 ± 38 ms vs 406 ± 30 and 64 ± 31 vs 44 ± 18, respectively; P < 0.05). QTc interval and QT dispersion in group B (436 ± 50 and 64 ± 22 ms) were also significantly greater than those in group A. During follow-up periods, four sudden cardiac deaths and one ventricular fibrillation were observed in group C, and two nonlethal ventricular tachyarrhythmias were observed in group B. Conclusions: Patients with HCM-related gene mutation accompanying any ECG abnormalities frequently exhibited impaired QT variables even without LVH. We suggest that careful observation should be considered for those genotyped subjects. [source] Inflammatory Biomarkers are not Predictive of Intermediate-term Risk of Ventricular Tachyarrhythmias in Stable CHF PatientsCLINICAL CARDIOLOGY, Issue 8 2007Yuval Konstantino M.D. Abstract Background: Elevated levels of inflammatory biomarkers and brain natriuretic peptide (BNP) are associated with increased mortality in patients with heart failure (HF). Hypothesis: The aim of the current study was to assess the correlation between circulating biomarkers and ventricular tachyarrhythmias among patients with HF. Methods: Blood samples from 50 stable ambulatory HF patients with moderate to severe systolic left ventricular (LV) dysfunction and an implantable cardioverter defibrillator (ICD) were analyzed for interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-,), high-sensitivity C-reactive protein (hsCRP) and BNP. Thereafter, the patients were followed for a mean period of 152 ± 44 days, during which ventricular tachyarrhythmias were recorded by the ICDs. Results: Follow-up data were obtained from 47 patients. Of them, 45 (96%) had ischemic cardiomyopathy, 38 (81%) had New York Heart Association class I,II, 43 (91%) were males, and the mean age was 68.6 ± 11.1 years. During follow-up, 5 patients (11%) had nonsustained ventricular tachycardia (NSVT), 6 patients (13%) had sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) and 36 patients (76%) had no events. The circulating biomarkers' levels upon enrollment were not significantly different between patients who subsequently had NSVT or VT/VF and patients who were free of events. Conclusions: No correlation was found between plasma levels of IL-6, TNF-,, hsCRP and BNP and ventricular arrhythmic events among stable HF patients during an intermediate term follow-up of 5.1 months. Further studies are still required to assess the association between these biomarkers and long-term risk of ventricular tachyarrhythmia. Copyright © 2007 Wiley Periodicals, Inc. [source] Ventricular tachyarrhythmia associated with cardiac sarcoidosis: Its mechanisms and outcomeCLINICAL CARDIOLOGY, Issue 4 2004Hiroshi Furushima M.D. Abstract Background: Cardiac sarcoidosis is increasingly recognized and is associated with poor prognosis. Ventricular tachycardia (VT) associated with cardiac sarcoidosis is the most likely cause of sudden death in most patients, but the mechanism has not been well established. Hypothesis: This study investigated the mechanisms and outcome of VT associated with cardiac sarcoidosis. Methods: The study included eight consecutive patients (five men, three women, aged 54 ± 19 years) who had sustained monomorphic VT associated with cardiac sarcoidosis in our hospital. Results: The average ejection fraction was 43 ± 11%. Twenty-two VTs were observed in these patients, and mean heart rate during VT was 192 ± 29 beats/min (range 144,259). The phenomenon of transient entrainment was documented in 10 of 22 (45%) VTs by ventricular pacing (eight in the active phase). Another five (23%) VTs could not be entrained, but could be initiated by programmed stimulation and terminated by rapid pacing, reproducibly. In 3 of the 22 (14%) VTs, cardioversion was required urgently because of the fast rate, while the remaining 4 (18%) could be induced during electrophysiologic study. Conclusions: In this study, there was a high possibility that the mechanism of 15 (68%) VTs was reentry. Reentrant substrate is formed not only in association with the healing of cardiac granulomas in the inactive phase of cardiac sarcoidosis but also in the active phase. Ventricular tachycardia with cardiac sarcoidosis, even if this mechanism is reentry, has different inducibility between the active and inactive phases in an electrophysiologic study. This makes the therapy for cardiac sarcoidosis (e.g., corticosteroids, antiarrhythmic agents, and catheter ablation) difficult. The implantable cardioverter-defibrillator is an effective treatment for ventricular tachyarrythmia with cardiac sarcoidosis. [source] Familial progressive sinoatrial and atrioventricular conduction disease of adult onset with sudden death, dilated cardiomyopathy, and brachydactyly.CLINICAL GENETICS, Issue 2 2005A new type of heart-hand syndrome? We identified a family with 10 affected members in four generations suffering from adult-onset progressive sinoatrial and atrioventricular conduction disease, sudden death due to ventricular tachyarrhythmia, dilated cardiomyopathy, and a unique type of brachydactyly with mild hand involvement (short distal, middle, proximal phalanges and clinodactyly) and more severe foot involvement (short distal, proximal phalanges and metatarsal bones, short or absent middle phalanges, terminal symphalangism, duplication of the bases of the second metatarsals, extra ossicles, and syndactyly). The phenotype differences from other reported genetic abnormalities and linkage exclusion of Holt,Oram syndrome, ulnar,mammary syndrome, brachydactyly type B or Robinow syndrome, and cardiac conduction disease or Brugada syndrome loci suggest that we report on a new hereditary heart-hand syndrome. [source] | ||||||||||||||||||||||||||||||||||