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Ventricular Stimulation (ventricular + stimulation)
Selected AbstractsTemporary Epicardial Ventricular Stimulation in Patients with Atrial Fibrillation: Acute Effects of Ventricular Pacing Site on Bypass Graft FlowsJOURNAL OF CARDIAC SURGERY, Issue 4 2009Navid Madershahian M.D. This study aimed to evaluate the optimal epicardial ventricular pacing site in patients with AF following coronary artery bypass surgery (CABG). Methods: In 23 consecutive patients (mean age = 69.2 ± 1.9 years, gender = 62% male, ejection fraction [EF]= 50.4 ± 2.1%) monoventricular stimulations (VVI) were tested with a constant pacing rate of 100 bpm. The impact of ventricular pacing on bypass graft flow (transit-time flow probe) and pulsatility index (PI) were measured after lead placement on the mid paraseptal region of the right (RVPS) and the left (LVPS) ventricle, on the right inferior wall (RVIW), and on the right ventricular outflow tract (RVOT). In addition, hemodynamic parameters were measured. Patients served as their own control. Results: Comparison of all tested pacing locations revealed that RVOT stimulation provided the highest bypass grafts flows (59.9 ± 6.1 mL/min) and PI (2.2 ± 0.1) when compared with RVPS (51.3 ± 4.7 mL/min, PI = 2.6 ± 0.2), RVIW (54.0 ± 5.1 mL/m; PI = 2.4 ± 0.2), and LVPS (53.1 ± 4.5 mL/min; PI = 2.3 ± 0.1), respectively (p < 0.05). When analyzing patients according to their preoperative LV function (group I = EF > 50%; group II = EF < 50%), higher bypass graft flows were observed with RVOT pacing in patients with lower EF (p = n.s.). Conclusions: Temporary RVOT pacing facilitates optimal bypass graft flows when compared with other ventricular pacing sites and should be the preferred method of temporary pacing in cardiac surgery patients with AF. Especially in patients with low EF following CABG, RVOT pacing may improve myocardial oxygen conditions for the ischemic myocardium and enhance graft patency in the early postoperative period. [source] Sinus Node Inhibition During Ventricular StimulationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2002MAURICIO ABELLO M.D. [source] Usefulness of Nonlinear Analysis of ECG Signals for Prediction of Inducibility of Sustained Ventricular Tachycardia by Programmed Ventricular Stimulation in Patients with Complex Spontaneous Ventricular ArrhythmiasANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2008Ornella Durin M.D. Introduction: The aim of our study was to assess the effectiveness of the nonlinear analysis (NLA) of ECG in predicting the results of invasive electrophysiologic study (EPS) in patients with ventricular arrhythmias. Methods: We evaluated 25 patients with history of cardiac arrest, syncope, sustained, or nonsustained ventricular tachycardia (VT). All patients underwent electrophysiologic study (EPS) and nonlinear analysis (NLA) of ECG. The study group was compared with a control group of 25 healthy subjects, in order to define the normal range of NLA. ECG was processed in order to obtain numerical values, which were analyzed by nonlinear mathematical functions. Patients were classified through the application of a clustering procedure to the whole set of functions, and the correlation between the results of nonlinear analysis of ECG and EPS was tested. Results: NLA assigned all patients with negative EPS to the same class of healthy subjects, whereas the patients in whom VT was inducible had been correctly and clearly isolated into a separate cluster. In our study, the result of NLA with application of the clustering technique was significantly correlated to that of EPS (P < 0.001), and was able to predict the result of EPS, with a negative predictive value of 100% and a positive predictive value of 100%. Conclusions: NLA can predict the results of EPS with good negative and positive predictive value. However, further studies are needed in order to verify the usefulness of this noninvasive tool for sudden death risk stratification in patients with ventricular arrhythmias. [source] Electrophysiological determinants of hypokalaemia-induced arrhythmogenicity in the guinea-pig heartACTA PHYSIOLOGICA, Issue 4 2009O. E. Osadchii Abstract Aim:, Hypokalaemia is an independent risk factor contributing to arrhythmic death in cardiac patients. In the present study, we explored the mechanisms of hypokalaemia-induced tachyarrhythmias by measuring ventricular refractoriness, spatial repolarization gradients, and ventricular conduction time in isolated, perfused guinea-pig heart preparations. Methods:, Epicardial and endocardial monophasic action potentials from distinct left ventricular (LV) and right ventricular (RV) recording sites were monitored simultaneously with volume-conducted electrocardiogram (ECG) during steady-state pacing and following a premature extrastimulus application at progressively reducing coupling stimulation intervals in normokalaemic and hypokalaemic conditions. Results:, Hypokalaemic perfusion (2.5 mm K+ for 30 min) markedly increased the inducibility of tachyarrhythmias by programmed ventricular stimulation and rapid pacing, prolonged ventricular repolarization and shortened LV epicardial and endocardial effective refractory periods, thereby increasing the critical interval for LV re-excitation. Hypokalaemia increased the RV-to-LV transepicardial repolarization gradients but had no effect on transmural dispersion of APD90 and refractoriness across the LV wall. As determined by local activation time recordings, the LV-to-RV transepicardial conduction and the LV transmural (epicardial-to-endocardial) conduction were slowed in hypokalaemic heart preparations. This change was attributed to depressed diastolic excitability as evidenced by increased ventricular pacing thresholds. Conclusion:, These findings suggest that hypokalaemia-induced arrhythmogenicity is attributed to shortened LV refractoriness, increased critical intervals for LV re-excitation, amplified RV-to-LV transepicardial repolarization gradients and slowed ventricular conduction in the guinea-pig heart. [source] The L-Type Ca2+ and KATP Channels May Contribute to Pacing-Induced Protection Against Anoxia-Reoxygenation in the Embryonic Heart ModelJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2008PHILIPPE BRUCHEZ M.D. Aims: The L-type Ca2+ channel, the sarcolemmal (sarcKATP), and mitochondrial KATP (mitoKATP) channels are involved in myocardial preconditioning. We aimed at determining to what extent these channels can also participate in pacing-induced cardioprotection. Methods: Hearts of 4-day-old chick embryos were paced in ovo during 12 hour using asynchronous intermittent ventricular stimulation at 110% of the intrinsic rate. Sham operated and paced hearts were then submitted in vitro to anoxia (30 minutes) and reoxygenation (60 minutes). These hearts were exposed to L-type Ca2+ channel agonist Bay-K-8644 (BAY-K) or blocker verapamil, nonselective KATP channel antagonist glibenclamide (GLIB), mitoKATP channel agonist diazoxide (DIAZO), or antagonist 5-hydroxydecanoate. Electrocardiogram, electromechanical delay (EMD) reflecting excitation-contraction (E-C) coupling, and contractility were determined. Results: Under normoxia, heart rate, QT duration, conduction, EMD, and ventricular shortening were similar in sham and paced hearts. During reoxygenation, arrhythmias ceased earlier and ventricular EMD recovered faster in paced hearts than in sham hearts. In sham hearts, BAY-K (but not verapamil), DIAZO (but not 5-hydroxydecanoate) or GLIB accelerated recovery of ventricular EMD, reproducing the pacing-induced protection. By contrast, none of these agents further ameliorated recovery of the paced hearts. Conclusion: The protective effect of chronic asynchronous pacing at near physiological rate on ventricular E-C coupling appears to be associated with subtle activation of L-type Ca2+ channel, inhibition of sarcKATP channel, and/or opening of mitoKATP channel. [source] New or Aggravated Heart Failure during Long-Term Right Ventricular Pacing after AV Junctional Catheter AblationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2009DRITAN POÇI M.D. Background: Atrioventricular junctional ablation (AVJA) improves symptoms and quality of life in patients with pharmacologically resistant atrial fibrillation (AF). However, long-term right ventricular stimulation has also been reported to lead to deterioration of the left ventricular function. We retrospectively analyzed the incidence of new or aggravated heart failure (HF) during long-term right ventricular stimulation following AVJA. Methods: Two hundred thirteen patients (110F:103M), 73 ± 10 years old, were followed for a period of 6 ± 3 years after AVJA. Forty-nine patients (23%) were known to have HF before AVJA. New HF was diagnosed if at least two of the following criteria were present: NYHA class >2, an LVEF <45%, and medication for HF. Aggravated HF was defined as an increase in the functional class and/or new prescription of medication for HF. All-cause death was a secondary endpoint. Results: During follow-up, 26% of the patients with known HF showed an aggravation of HF, while 13% developed new symptoms of HF. High age and low EF were independent predictors of new or aggravated HF and of new HF, while none of the tested variables predicted aggravation of known HF. The all-cause mortality was 16%, where high age and coronary artery disease were found to be independent predictors. Conclusion: AVJA followed by right ventricular pacing was associated with aggravated HF in 23% of patients with known HF, while development of new symptoms of HF occurred much less often during follow-up (13%). The majority of patients who underwent AVJA continued to do well during long-term follow-up. [source] Successful Radiofrequency Catheter Ablation of Ventricular Tachycardia Originating from Underneath the Mechanical Prosthetic Aortic ValvePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2008TAKUMI YAMADA M.D. A 67-year-old man who developed sustained ventricular tachycardia (VT) 4 years after a prosthetic aortic valve replacement, underwent electrophysiologic testing and catheter ablation. The mechanism of the VT was suggested to be triggered activity because the VT could be induced by programmed ventricular stimulation, and burst ventricular pacing demonstrated overdrive suppression without a transient entrainment. Successful catheter ablation using a transseptal approach was achieved underneath the mechanical prosthetic aortic valve on the blind side for that approach. This case demonstrated that catheter mapping and ablation of the entire LV using a transseptal approach might be possible. [source] Abnormal Nocturnal Heart Rate Variability and QT Dynamics in Patients with Brugada SyndromePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2007BERTRAND PIERRE M.D. Background: In Brugada syndrome (BSY), most of the ventricular arrhythmic events are nocturnal, suggesting an influence of the autonomic nervous system. Methods: In 46 patients (mean age = 41 ± 14 years, 43 men) with electrocardiograms (ECG) consistent with BSY and structurally normal hearts, we measured heart rate variability (HRV) and QT dynamics (QT/RR slopes) on 24-hour ambulatory ECG. Type 1 BSY-ECG was spontaneous in 23 (50%) and induced in 23 patients. Results: History of syncope was present in 23 patients (50%). Programmed ventricular stimulation induced ventricular tachyarrhythmias (VTA) in 13 patients (28%). A single patient developed ventricular tachycardia during a mean follow-up of 34 months. Compared to a control group matched for age and sex, HRV was decreased over 24 hours and during nighttime in patients with BSY (SDNN 122 ± 44 vs 93 ± 36 ms, P = 0.0008 and SDANN 88 ± 39 vs 54 ± 24 ms, P < 0.0001). QTend /RR slopes were decreased over 24 hours in patients with BSY (0.159 ± 0.05 vs 0.127 ± 0.05, P = 0.003) and particularly at night (0.123 ± 0.04 vs 0.089 ± 0.04, P = 0.0001). QTend /RR slopes were significantly decreased during nighttime in patients with spontaneous versus provoked BSY-ECG patterns. By contrast, HRV and QT/RR slopes were similar in symptomatic and asymptomatic patients, whether VTA were induced or not. Conclusions: Patients with a BSY-ECG pattern had lower HRV and QT/RR slopes than control subjects during nighttime. High-risk patients with spontaneous BSY-ECG patterns had the lowest nocturnal QTend/RR slopes. These unique repolarization dynamics might be related to the frequent nocturnal occurrence of VTA in BSY. [source] The Electrophysiological Characteristics in Patients with Ventricular Stimulation Inducible Fast-Slow Form Atrioventricular Nodal Reentrant TachycardiaPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2006PI-CHANG LEE M.D. Background: Atrioventricular nodal reentrant tachycardia (AVNRT) can usually be induced by atrial stimulation. However, it seldom may be induced with only ventricular stimulation, especially the fast-slow form of AVNRT. The purpose of this retrospective study was to investigate the specific electrophysiological characteristics in patients with the fast-slow form of AVNRT that could be induced with only ventricular stimulation. Methods: The total population consisted of 1,497 patients associated with AVNRT, and 106 (8.4%) of them had the fast-slow form of AVNRT and 1,373 (91.7%) the slow-fast form of AVNRT. In patients with the fast-slow form of AVNRT, the AVNRT could be induced with only ventricular stimulation in 16 patients, Group 1; with only atrial stimulation or both atrial and ventricular stimulation in 90 patients, Group 2; and with only atrial stimulation in 13 patients, Group 3. We also divided these patients with slow-fast form AVNRT (n = 1,373) into two groups: those that could be induced only by ventricular stimulation (Group 4; n = 45, 3%) and those that could be induced by atrial stimulation only or by both atrial and ventricular stimulation (n = 1.328, 97%). Results: Patients with the fast-slow form of AVNRT that could be induced with only ventricular stimulation had a lower incidence of an antegrade dual AVN physiology (0% vs 71.1% and 92%, P < 0.001), a lower incidence of multiple form AVNRT (31% vs 69% and 85%, P = 0.009), and a more significant retrograde functional refractory period (FRP) difference (99 ± 102 vs 30 ± 57 ms, P < 0.001) than those that could be induced with only atrial stimulation or both atrial and ventricular stimulation. The occurrence of tachycardia stimulated with only ventricular stimulation was more frequently demonstrated in patients with the fast-slow form of AVNRT than in those with the slow-fast form of AVNRT (15% vs 3%, P < 0.001). Patients with the fast-slow form of AVNRT that could be induced with only ventricular stimulation had a higher incidence of retrograde dual AVN physiology (75% vs 4%, P < 0.001), a longer pacing cycle length of retrograde 1:1 fast and slow pathway conduction (475 ± 63 ms vs 366 ± 64 ms, P < 0.001; 449 ± 138 ms vs 370 ± 85 ms, P = 0.009), a longer retrograde effective refractory period of the fast pathway (360 ± 124 ms vs 285 ± 62 ms, P = 0.003), and a longer retrograde FRP of the fast and slow pathway (428 ± 85 ms vs 362 ± 47 ms, P < 0.001 and 522 ± 106 vs 456 ± 97 ms, P = 0.026) than those with the slow-fast form of AVNRT that could be induced with only ventricular stimulation. Conclusion: This study demonstrated that patients with the fast-slow form of AVNRT that could be induced with only ventricular stimulation had a different incidence of the antegrade and retrograde dual AVN physiology and the specific electrophysiological characteristics. The mechanism of the AVNRT stimulated only with ventricular stimulation was supposed to be different in patients with the slow-fast and fast-slow forms of AVNRT. [source] Influence of Drive Cycle Length on Initiation of Ventricular Fibrillation During Implantable Cardioverter Defibrillator Threshold TestingPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2006NEIL K. SANGHVI Background: Programmed electrical stimulation of the heart as a method to induce tachyarrhythmias has been described since the 1960s. To date, no study has examined optimal drive cycle length in the induction of ventricular fibrillation (VF) during defibrillation threshold testing after implantable cardioverter-defibrillator placement. We hypothesized that longer drive cycle length, by means of the longer action potential duration, would promote intramyocardial phase 2 reentry and facilitate induction of VF. Methods: Fifty consecutive implants were randomized in a prospective crossover format for this study. The group consisted of 40 men and 10 women, with each patient receiving either a 400 or 600 ms initial drive train prior to 1.2 J internal shock on the T wave with a goal to induce ventricular fibrillation. The timing of the T wave shock was determined by measuring the interval from the beginning of the QRS to the apex of the T wave in lead II. Successful inductions were defibrillated via the cardioverter defibrillator. Patients were then crossed over and the protocol repeated. Results: Twenty of 23 (87%) patients were successfully induced into VF in the initial 400 ms drive train arm whereas 22 of 27 (81%) were successfully induced in the 600 ms arm. Thus, a total of 44 (88%) patients were successfully induced at 400 ms, 41 (82%) patients were successfully induced at 600 ms, and 2 (4%) patients were not inducible at either cycle length, but were inducible with 50 Hz ventricular stimulation. However, no significant difference was noted between the two groups. Conclusion: No investigation to date has questioned whether a relationship exists between drive cycle length and initiation of ventricular fibrillation. Our study addresses this question, though negative for difference between 400 and 600 ms drive trains. Further research into optimal strategies for inducing ventricular fibrillation will minimize patient sedation time and discomfort while undergoing defibrillator threshold testing. [source] Significance of Inducible Ventricular Flutter-Fibrillation After Myocardial InfarctionPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2005BÉATRICE BREMBILLA-PERROT Aim: The purpose of this study was to determine the factors associated with the induction of ventricular flutter/fibrillation (VFl/VF)and its prognostic significance in post-myocardial infarction. Methods: Programmed ventricular stimulation was performed after myocardial infarction (MI) for syncope (n = 232) or systematically (n = 755); 230 patients had an induced VFl/VF and were followed during 4 ± 2 years. Results: VFl/VF was induced in 49/232 patients (21%) with syncope versus 181/755 asymptomatic patients (24%) (NS) and 94/410 patients (23%) with left ventricular ejection fraction (LVEF) <40% versus 136/577 patients (22.5%) with LVEF >40% (NS). Cardiac mortality was 9%; LVEF was 33 ± 15% in patients who died, 43 ± 13% in alive patients (P < 0.004). In patients with LVEF <40%, induced VFl/VF, mortality rate was 31% in those with syncope, 10% in asymptomatic patients (P < 0.001), because of an increase of deaths by heart failure; patients with LVEF >40% with or without syncope had a low mortality (5% and 3%). After linear logistic regression, VFl/VF and LVEF were predictors of total cardiac mortality, but only LVEF <40% predicted sudden death. Conclusion: Syncope and the level of LVEF did not increase the incidence of VFl/VF induction after MI, but modified the cardiac mortality: induced VF increased total cardiac mortality in patients with syncope and LVEF <40%, but did not increase sudden death. In patients with LVEF >40%, induced VFl/VF has no significance neither in asymptomatic patients nor in those with syncope. [source] Intravenous Administration of Class I Antiarrhythmic Drug Induced T Wave Alternans in an Asymptomatic Brugada Syndrome PatientPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2003KIMIE OHKUBO A 53-year-old man with an abnormal ECG was referred to the Nihon University School of Medicine. The 12-lead ECG showed right bundle branch block and saddleback-type ST elevation in leads V1,V3 (Brugada-type ECG). Signal-averaged ECG showed positive late potentials. Double ventricular extrastimuli (S1: 500 ms, S2: 250 ms, S3: 210 ms) induced VF. Amiodarone (200 mg/day) was administered for 6 months and programmed ventricular stimulation was repeated. VF was induced again by double ventricular stimuli (S1: 600 ms, S2: 240 ms, S3: 170 ms). Intravenous administration of class Ic antiarrhythmic drug, pilsicainide (1 mg/kg), augmented ST-T elevation in leads V1,V3, and visible ST-T alternans that was enhanced by atrial pacing was observed in leads V2 and V3. Visible ST-T wave alternans disappeared in 15 minutes. However, microvolt T wave alternans was present during atrial pacing at a rate of 70/min without visible ST-T alternans. (PACE 2003; 26:1900,1903) [source] Improved Differentiation of the Ventricular Evoked Response from Polarization by Modification of the Pacemaker ImpulsePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2000FRANK PROVENIER The Autocapture feature, implemented in the Microny and Regency pacemakers of St. Jude Medical, continuously controls the effectiveness of ventricular stimulation by detection of the evoked response. Proper sensing of this signal depends on the magnitude of the polarization, which should be minimal. Therefore, the conjunctive use of low polarization electrodes is recommended. Further, the pacing impulse of these pacemakers has a biphasic waveform consisting of a stimulus followed by a fast discharge pulse. This study compares polarization of a modified pacing impulse with the default pacing impulse, and its effect on the ability to activate the Autocapture function when used with different types of electrodes. In 45 patients, acute measurements of the polarization and the evoked response were performed at random on the modified pacing impulses of a custom designed Regency and on the default stimuli of a standard Regency. The following bipolar leads were used: 20 Medtronic 4024 CapSure, 12 Pacesetter 1450T. and 13 Pacesetter 14701. Using the default pacing impulse, polarization and evoked response were significantly larger with the Medtronic 4024 CapSure compared to the low polarization leads. The polarization to evoked response ratio was more frequently acceptable for activation of the Autocapture with the Pacesetter leads. In all leads the modified pacing impulse was characterized bv significantly smaller polarization with the most prominent reduction in the Medtronic 4024 CapSure. The differences in the pacing impulse did not affect the evoked response. With the programmability of the fast discharge pulse, the requirements to activate the Autocapture function were fulfilled in 29 (94%) of 31 patients with the modified pacing impulse, compared to 22 (71%) of 31 patients with the standard pacing impulse. The modified pacing impulse decreased the "polarization to evoked response" ratio, and by that improved the conditions for activation of the Autocapture function. [source] | ||||||||||