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Malignant Arrhythmias (malignant + arrhythmias)

Distribution by Scientific Domains

Medical Sciences	85%

Selected Abstracts

Effects of acute vagal nerve stimulation on the early passive electrical changes induced by myocardial ischaemia in dogs: heart rate-mediated attenuation

EXPERIMENTAL PHYSIOLOGY, Issue 8 2008
Carlos L. Del Rio
Parasympathetic activity during acute coronary artery occlusion (CAO) can protect against ischaemia-induced malignant arrhythmias; nonetheless, the mechanism mediating this protection remains unclear. During CAO, myocardial electrotonic uncoupling is associated with autonomically mediated immediate (i.e. type 1A) arrhythmias and can modulate pro-arrhythmic dispersion of repolarization. Therefore, the effects of acutely enhanced or decreased cardiac parasympathetic activity on early electrotonic coupling during CAO, as measured by myocardial electrical impedance (MEI), were investigated. Anaesthetized dogs were instrumented for MEI measurements, and left circumflex coronary arterial occlusions were performed in intact (CTRL) and vagotomized (VAG) animals. The CAO was followed by either vagotomy (CTRL) or vagal nerve stimulation (VNS, 10 Hz, 10 V) in the VAG dogs. Vagal nerve stimulation was studied in two additional sets of animals. In one set heart rate (HR) was maintained by pacing (220 beats min,1), while in the other set bilateral stellectomy preceded CAO. The MEI increased after CAO in all animals. A larger MEI increase was observed in vagotomized animals (+85 ± 9 ,, from 611 ± 24 ,, n= 16) when compared with intact control dogs (+43 ± 5 ,, from 620 ± 20 ,, n= 7). Acute vagotomy during ischaemia abruptly increased HR (from 155 ± 11 to 193 ± 15 beats min,1) and MEI (+12 ± 1.1 ,, from 663 ± 18 ,). In contrast, VNS during ischaemia (n= 11) abruptly reduced HR (from 206 ± 6 to 73 ± 9 beats min,1) and MEI (,16 ± 2 ,, from 700 ± 44 ,). These effects of VNS were eliminated by pacing but not by bilateral stellectomy. Vagal nerve stimulation during CAO also attenuated ECG-derived indices of ischaemia (e.g. ST segment, 0.22 ± 0.03 versus 0.15 ± 0.03 mV) and of rate-corrected repolarization dispersion [terminal portion of T wave (TPEc), 84.5 ± 4.2 versus 65.8 ± 5.9 ms; QTc, 340 ± 8 versus 254 ± 16 ms]. Vagal nerve stimulation during myocardial ischaemia exerts negative chronotropic effects, limiting early ischaemic electrotonic uncoupling and dispersion of repolarization, possibly via a decreased myocardial metabolic demand. [source]

Early and Late Results of Partial Left Ventriculectomy: Single Center Experience and Review of the Literature

JOURNAL OF CARDIAC SURGERY, Issue 3 2003
Raimondo Ascione M.D.
Methods: From February 1996 to August 2001, 24 patients with dilated cardiomyopathy (DCM) (12 idiopathic, 12 ischemic) underwent PLV. Perioperative and follow-up data were prospectively entered into a database and analyzed. An observational analysis of the literature was carried out of all the published series of PLV reporting on ,15 patients. Results: In our series there were 22 males with amean age of 65 years (range 49 to73]). Of the 22, there were 3 (12.5%) in-hospital deaths. Mean duration of follow-up was 26 months (range 3 to 71) with 9 late deaths (38%), 6 in the idiopathic group. The five-year actuarial survival was 74% in the ischemic group and 33% in the idiopathic group. The observational analysis of literature included a total of 506 patients (425 males, age 50.2 ± 5.2 years)]. The etiology was idiopathic in 255 (50.4%), and ischemic in 89 (17.6%) patients. Baseline characteristics of the whole population include: ejection fraction 18.9 ± 3.9%, NYHA functional class 3.7 ± 0.2, and LVEDD of 7.7 ± 0.4 cm. Severe mitral regurgitation was present in 368 (72.7%) patients. There were 88 (17.4%) in-hospital deaths. Cause of death included 55 due to (62.5%) low cardiac output, 10 (11.3%) due to severe bleeding, 7 (7.95%) caused by malignant arrhythmias, 8 (9%) due to sepsis, and 5 (5.7%) as a result of stroke. Ten of the selected series (overall 386 patients) reported late outcome. There were 89 (22.9%) late deaths, 12 (13.5%) were not cardiac-related, 50 (56.2%) were due to recurrence of congestive heart failure (CHF), 20 (22.5%) caused by sudden arrhythmias, 5 (5.6%) due to infections, and 2 (2.2%) from strokes. Overall, there were 248 (64.2%) survivors, of whom 179 (72.17%) were reported to be in NYHA functional class I or II. All 10 papers reported one-year survival ranging from 50% to 85%. Seven reported a two-year survival of 45% to 72%, and 4 reported a three-year survival of 33% to 64%. Conclusions: Our results and the review of the literature seem to suggest a relatively high early mortality with satisfactory late results of PLV in patients with dilated cardiomyopathy.(J Card Surg 2003;18:190-196) [source]

The Effect of Antihistamine Cetirizine on Ventricular Repolarization in Congenital Long QT Syndrome

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2007
ANNA-MARI HEKKALA M.D.
Introduction: Many drugs are known to block cardiac potassium channels, thus prolonging QT interval and predisposing to malignant arrhythmias. Patients with congenital long QT syndrome are particularly vulnerable, but usually electrophysiological effects of drugs have not been assessed in these patients at risk. Methods: Fifteen asymptomatic patients with type 1 (LQT1), 15 patients with type 2 (LQT2) long QT syndrome, and 15 healthy volunteers took a placebo and cetirizine 10 mg. In addition, healthy volunteers took cetirizine 50 mg. The study was single-blinded and randomized. Exercise tests were performed during stable plasma concentrations. The electrocardiogram was recorded with a body surface potential mapping system (BSPM). Data were analyzed with an automated analyze program. QT intervals to the T wave apex and T wave end and their difference (Tp-e) were determined at rest and at specified heart rates during and after exercise. Results: Cetirizine did not lengthen the QT intervals at rest or during exercise and recovery in any group. It shortened Tp-e at rest in LQT1 and LQT2 patients and during exercise test in LQT1 patients, thus slightly decreasing electrocardiographic transmural dispersion of repolarization. Conclusions: Cetirizine does not adversely modify ventricular repolarization in types 1 and 2 long QT syndrome, suggesting that it might be used safely in these long QT syndrome patients. [source]

Diagnostic Value of Flecainide Testing in Unmasking SCN5A-Related Brugada Syndrome

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2006
PAOLA G. MEREGALLI M.D.
Introduction: Provocation tests with sodium channel blockers are often required to unmask ECG abnormalities in Brugada syndrome (BrS). However, their diagnostic value is only partially established, while life-threatening ventricular arrhythmias during these tests were reported. We aimed to establish sensitivity, specificity, and safety of flecainide testing, and to predict a positive test outcome from the baseline ECG. Methods and Results: We performed 160 tests with flecainide in subjects determined to be at risk for BrS. P wave width, PQ duration, QRS width, S wave amplitude and duration in leads II-III, in addition to ST morphology and J point elevation in V1-V3 were measured before and after flecainide administration. Moreover, leads were positioned over the third intercostal space (V1IC3 -V2IC3). Flecainide tests were considered positive if criteria from the First Consensus Report on BrS were fulfilled. In 64 cases, the test was positive, while 95 were negative (1 test was prematurely interrupted). The sensitivity and specificity, calculated in SCN5A-positive probands and their family members, were 77% and 80%, respectively. Baseline ECGs exhibited significant group differences in P, PQ, and QRS duration, J point elevation (leads V1-V2 and V1IC3 -V2IC3), and S duration in II, but an attempt to predict the outcome of flecainide testing from these baseline ECG parameters failed. No malignant arrhythmias were observed. Conclusion: Flecainide testing is a valid and safe tool to identify SCN5A-related BrS patients. Baseline ECGs do not predict test outcomes, but point to conduction slowing as a core mechanism in BrS. [source]

How Revealing Are Insertable Loop Recorders in Pediatrics?

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 3 2008
PATRICIA A. FRANGINI M.D.
Introduction: An insertable loop recorder (ILR) in patients with infrequent syncope or palpitations may be useful to decide management strategies, including clinical observation, medical therapy, pacemaker, or implantable cardioverter defibrillator (ICD). We sought to determine the diagnostic utility of the Reveal® ILR (Medtronic, Inc., Minneapolis, MN, USA) in pediatric patients. Methods: Retrospective review of clinical data, indications, findings, and therapeutic decision in 27 consecutive patients who underwent ILR implantation from 1998,2007. Results: The median age was 14.8 years (2,25 years). Indications were syncope in 24 patients and recurrent palpitations in three. Overall, eight patients had structural heart disease (six congenital heart disease, one hypertrophic cardiomyopathy, one Kawasaki), five had previous documented ventricular arrhythmias with negative evaluation including electrophysiology study, and three patients had QT prolongation. Tilt testing was performed in 10 patients, of which five had neurocardiogenic syncope but recurrent episodes despite medical therapy. After median three months (1,20 months), 17 patients presented with symptoms and the ILR memory was analyzed in 16 (no episode stored in one due to full device memory), showing asystole or transient atrioventricular (AV) block (2), sinus bradycardia (6), or normal sinus rhythm (8). Among asymptomatic patients, 3/10 had intermittent AV block or long pauses, automatically detected and stored by the ILR. In 19 of 20 patients, ILR was diagnostic (95%) and five subsequently underwent pacemaker implantation, while seven patients remained asymptomatic without ILR events. Notably, no life-threatening events were detected. The ILR was explanted in 22 patients after a median of 22 months, two due to pocket infection, 12 for battery depletion and eight after clear documentation of nonmalignant arrhythmia. Conclusions: The ILR in pediatrics is a useful adjunct to other diagnostic studies. Patient selection is critical as the ILR should not be utilized for malignant arrhythmias. A diagnosis is attained in the majority of symptomatic patients, predominantly bradyarrhythmias including pauses and intermittent AV block. [source]

REFLEXLY EVOKED COACTIVATION OF CARDIAC VAGAL AND SYMPATHETIC MOTOR OUTFLOWS: OBSERVATIONS AND FUNCTIONAL IMPLICATIONS

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 12 2006
Julian FR Paton
SUMMARY 1The purpose of the present review is to highlight the pattern of activity in the parasympathetic and sympathetic nerves innervating the heart during their reflex activation. 2We describe the well-known reciprocal control of cardiac vagal and sympathetic activity during the baroreceptor reflex, but point out that this appears to be the exception rather than the rule and that many other reflexes reviewed herein (e.g. peripheral chemoreceptor, nociceptor, diving response and oculocardiac) involve simultaneous coactivation of both autonomic limbs. 3The heart rate response during simultaneous activation of cardiac autonomic outflows is unpredictable because it does not simply reflect the summation of opposing influences. Indeed, it can result in bradycardia (peripheral chemoreceptor, diving and corneal), tachycardia (nociceptor) and, in some circumstances, can predispose to malignant arrhythmias. 4We propose that this cardiac autonomic coactivation may allow greater cardiac output during bradycardia (increased ventricular filling time and stronger contraction) than activation of the sympathetic limb alone. This may be important when pumping blood into a constricted vascular tree, such as is the case during the peripheral chemoreceptor reflex and the diving response. [source]

Medical management of significant coronary angiographic stenoses: Outcome of 60 patients observed for 433 patient years

CLINICAL CARDIOLOGY, Issue 8 2000
Charles L. Baird Jr. M.D.
Abstract Background: Percutaneous transluminal coronary angioplasty (PTCA) has become routine in the management of patients with stable angina pectoris and significant coronary stenoses, while medical management of such patients has declined. Hypothesis: The purpose of the present study was to evaluate the outcome of 60 patients at the Virginia Heart Institute with stable angina pectoris, observed between 1976 and 1997, who had documented evidence of severe angiographic disease but were elected to be monitored and managed in an outpatient pharmacologic rehabilitation program. Methods: Sixty patients with significant stenoses by coronary angiography (21 with single-vessel, 26 with double-vessel, and 13 with triple-vessel) without impaired ventricular function, exercise-induced ischemia or hypotension, limited exercise performance, malignant arrhythmias, or drug intolerance were enrolled in a program of pharmacologic rehabilitation and observed for an average of 7.2 years. Results: Among the 60 patients, there were 6 deaths at a mean interval of 8.3 years. Two deaths were in patients ineligible for revascularization. Another patient who died had refused revascularization after new-onset left ventricular dysfunction, and another died intraoperatively during abdominal aortic aneurysm repair. Two patients died while exercising. Thirteen patients underwent follow-up catheterization for worsening angina; 11 of 13 showed progression, predominantly from new lesions. Four of 11 were referred for revascularization; 7 of 11 continued medical treatment; 49 patients were stable on medical therapy throughout the period of observation. Conclusion: Medical management of selected patients with significant coronary stenoses is safe and effective. [source]