Mevan Wijetunga

A Comparison of Echocardiographic Findings in Young Adults With Cardiomyopathy: With and Without a History of Methamphetamine Abuse

Methamphetamine is currently the most widespread illegal stimulant abused in the United States. No previous reports comparing echocardiographic findings of cardiomyopathy with and without a history of methamphetamine abuse are available.

Ablation of isthmus dependent atrial flutter: When to call for the next patient

Typical atrial flutter is a common reentrant atrial arrhythmia. The critical portion of the reentrant circuit is the rim of tissue between the tricuspid valve (TV) annulus and the inferior vena cava (IVC) (Fig.1).1,2 The reentrant circuit can operate in either clockwise or counterclockwise directions (Figs. 2–3). Elimination of conduction across the TV-IVC isthmus eliminates the tachycardia.3 The endpoint of ablation is to achieve bidirectional TVIVC isthmus block. Successful ablation of TV-IVC

Risk Stratification and Primary Prevention of Sudden Cardiac Death: Sudden Death Prevention

The initial challenge in primary prevention of sudden cardiac death (SCD) lies in identifying those at greatest risk, before the index event. Ventricular fibrillation is the leading cause of SCD; however, many clinical conditions predispose fatal ventricular dysrhythmias. In patients with structural heart disease, left ventricular dysfunction is the strongest predictor of SCD. Noninvasive markers such as nonsustained ventricular tachycardia, delayed potentials, decreased heart rate variability and baroreflex sensitivity, and repolarization alternans are further observed to assess risk in ischemic cardiomyopathy; however, most of these markers have poor positive predictive value and lack specificity. The electrophysiologic study has strong positive predictive value, but remains a costly and invasive method for risk stratification. In patients with normal hearts, genetic predisposition may identify patients at risk but clinical markers are not readily recognized. The implantable loop recorder is a useful tool in detecting dysrhythmic causes of syncope and identifying patients at risk for SCD.

Amiodarone versus Implantable Defibrillator (AMIOVIRT): background, rationale, design, methods, results and implications.

Non ischemic dilated cardiomyopathy (NIDCM) is a substrate for sudden cardiac death. Treatment with amiodarone may have a positive or neutral survival benefit. The role of ICD therapy in the primary prevention of sudden cardiac death in asymptomatic NIDCM patients is not clear. The purpose of the Amiodarone versus Implantable Defibrillator (AMIOVIRT) study was to compare total mortality, arrhythmia-free survival, quality of life and costs of therapy in patients with NIDCM, asymptomatic non-sustained ventricular tachycardia (NSVT) and left ventricular ejection fraction <or=0.35 who were randomized to therapy with amiodarone (52 patients) or an ICD (51 patients). At the first scheduled interim analysis, the previously determined stopping rule for futility was reached and the study was stopped. There was no statistically significant difference in the 1- and 3-year survival rates in the patients who received amiodarone compared with those who received an ICD (90% and 87% for amiodarone group versus 96% and 88% for ICD group; p = 0.8). There was a trend towards improved arrhythmia-free survival rates (p = 0.1), and cost of medical care (8,879 dollars vs. 22,039 dollars, p = 0.1) in the patients who were treated with amiodarone as compared to the patients who were treated with an ICD. At one year, the quality of life measures were not significantly different (p = 0.1).

Cardiac resynchronization therapy for congestive heart failure.

Cardiac resynchronization represents a novel therapeutic strategy for the treatment of congestive heart failure due to systolic dysfunction. Since its modest beginnings in the 1990s, cardiac resynchronization therapy has gained widespread acceptance as a useful adjunct to pharmacologic therapy for congestive heart failure. Randomized trials have consistently shown functional improvement in patients with congestive heart failure due to systolic dysfunction, a wide QRS complex on electrocardiogram and sinus rhythm, that are treated with cardiac resynchronization therapy. This review article will address the rationale, mechanisms of action, limitations and appropriate selection of patients for cardiac resynchronization therapy.

Nonexcitatory electrical currents for congestive heart failure: exciting or not?

A ventricular stimulation technique—cardiac contractility modulation by nonexcitatory electrical currents—has been proposed as a novel therapy for congestive heart failure.1-7 Preliminary human data with this therapy for congestive heart failure are presented by Pappone et al.8 in this issue of the Journal. The study uses a right ventricular stimulation technique that is purported to improve contractility in the failing heart.1-7 The pacemaker-like device delivers high-output pacing stimuli (7.7 V and 20 ms) to the right ventricle during the absolute refractory period. Therefore, the stimuli do not result in ventricular depolarization and, hence, are nonexcitatory. In theory, this increases available calcium from the sarcoplasmic reticulum and increases contractility.9 Animal studies and an acute study in humans have demonstrated improved contractility with nonexcitatory electrical currents.1-7 The study included 13 patients with severe symptoms due to congestive heart failure from systolic dysfunction who underwent implantation of a device system that delivers stimuli during the absolute refractory period. The system is composed of the pulse generator, a conventional atrial pacemaker lead, and two conventional ventricular pacemaker leads. The nonexcitatory stimuli were delivered daily for various time periods during the 32-week study. The primary study endpoints were safety and feasibility. Safety was defined as not identifying an increase in supraventricular or ventricular ectopy/nonsustained ventricular tachycardia. Feasibility was defined as appropriate sensing and delivery of the nonexcitatory electrical stimuli. Efficacy was a secondary endpoint and was assessed by comparing a variety of “soft endpoints.” These included things such as New York Heart Association (NYHA) functional classification, need for hospitalization for congestive heart failure therapy, quality-of-life measures, functional capacity, 6-minute hall walk, and various echocardiographic measures. The various endpoints were compared from baseline measurements to measurements obtained during or at the end of the treatment period. The authors report that the primary endpoints of safety and feasibility were achieved, that is, an increase in ventricular or supraventricular ectopy was not observed, and the nonexcitatory electrical stimuli were inhibited and delivered when appropriate. A post hoc analysis demonstrated a reduction in ectopic beats (P = 0.05) and nonsustained ven-