The Convergent Procedure: A Unique Multidisciplinary Hybrid Treatment of Atrial Fibrillation.

The convergent procedure is a hybrid ablation treatment for atrial fibrillation. It is increasingly considered as a management option for patients with persistent and long-standing atrial fibrillation. It consists of surgical ablation of the posterior left atrium through a minimally invasive closed-chest approach followed by endocardial catheter ablation. It is increasingly performed with concurrent epicardial occlusion of the left atrial appendage with a video-assisted thoracoscopic technique to physically and electrically isolate the left atrial appendage. This article provides an overview of a multidisciplinary approach to the convergent procedure, with concurrent thoracoscopic closure of the left atrial appendage, with an emphasis on perioperative management at a single institution. It provides a literature review of procedural outcomes, current data limitations, and future considerations.

Prediction and Prevention of Sudden Cardiac Death.

Sudden death is a major problem, with significant impact on public health. Many conditions predispose to sudden cardiac death and sudden cardiac arrest (SCA), foremost among them coronary artery disease, and an effective therapy exists in the form of the implantable cardioverter defibrillator. Risk stratification for SCA remains imperfect, especially for patients with nonischemic cardiomyopathy. Ongoing trials may make it easier to identify those at high risk, and potentially those at very low risk, in the future.

Cryoablation of the pulmonary veins using a novel balloon catheter.

INTRODUCTION: Pulmonary vein (PV) isolation has emerged as a promising technique for the treatment of patients with drug-refractory atrial fibrillation, however, the achievement of transmural lesions has remained a challenge. We evaluated the ability of a novel balloon-based cryogenic catheter system in achieving transmural lesions for PV isolation. METHODS: Six pulmonary vein ostia from three excised ovine hearts and lungs were used in this study. The balloon catheter was deployed and positioned at the ostia of the PVs and a full 8-minute ablation was then performed, while the heart was bathed in a circulating bath of normal saline at 37 degrees. Thermocouples positioned on the endocardial (balloon surface-tissue interface) and epicardial surfaces of the ostia were used to determine whether transmural freezing was achieved. RESULTS: The mean temperatures measured on the endocardial and epicardial tissue in six PV ablations were -38.8 +/- 6.9 degrees C and -10.0 +/- 7.5 degrees C, respectively. The average pulmonary vein thickness was 3.3 +/- 1.4 mm. CONCLUSIONS: A novel cryoablation balloon catheter is capable of achieving transmural freezing of the pulmonary vein. The catheter has promise for future clinical therapy of atrial fibrillation.

Cardiovascular toxicities of performance-enhancing substances in sports.

Athletes commonly use drugs and dietary supplements to improve athletic performance or to assist with weight loss. Some of these substances are obtainable by prescription or by illegal means; others are marketed as supplements, vitamins, or minerals. Nutritional supplements are protected from Food and Drug Administration regulation by the 1994 US Dietary Supplement Health and Education Act, and manufacturers are not required to demonstrate proof of efficacy or safety. Furthermore, the Food and Drug Administration lacks a regulatory body to evaluate such products for purity. Existing scientific data, which consist of case reports and clinical observations, describe serious cardiovascular adverse effects from use of performance-enhancing substances, including sudden death. Although mounting evidence led to the recent ban of ephedra (ma huang), other performance-enhancing substances continue to be used frequently at all levels, from elementary school children to professional athletes. Thus, although the potential for cardiovascular injury is great, few appropriately designed studies have been conducted to assess the benefits and risks of using performance-enhancing substances. We performed an exhaustive OVID MEDLINE search to Identify all existing scientific data, review articles, case reports, and clinical observations that address this subject. In this review, we examine the current evidence regarding cardiovascular risk for persons using anabolic-androgenic steroids including 2 synthetic substances, tetrahydrogestrinone and androstenedione (andro), stimulants such as ephedra, and nonsteroidal agents such as recombinant human erythropoietin, human growth hormone, creatine, and beta-hydroxy-beta-methylbutyrate.

Atrioventricular nodal reverse facilitation in connexin40-deficient mice.

BACKGROUND: Facilitation is an important physiologic property of the atrioventricular (AV) node. Previous studies demonstrated abnormal AV conduction in connexin (Cx)40-deficient mice. OBJECTIVES: We hypothesize that Cx40-deficient mice display altered patterns of AV nodal facilitation compared with wild-type mice. METHODS: Sixteen 36-week-old mice (eight Cx40(-/-) mice and eight Cx40(+/+) controls) underwent in vivo closed chest electrophysiologic study. A 2Fr octapolar catheter was advanced into the right ventricle to record a His-bundle electrogram. A special facilitation stimulation protocol was performed in each mouse to evaluate facilitation. Following atrial drive pacing (S1S1) at 150 ms, a facilitating beat S2 was delivered prior to the test beat S3. S3H3 was measured for varying S1S2 values at fixed H2S3 intervals. RESULTS: Progressive shortening of S1S2 (from 150 ms to 130, 110, and 90 ms) resulted in gradual prolongation of S2H2. The prolongation was more pronounced in Cx40(-/-) mice for each S1S2 compared with wild-type mice (P <.001). In each wild-type mouse, for a given H2S3 interval, this gradual increase in S2H2 produced progressive shortening of S3H3, so-called AV nodal facilitation phenomenon. However, in each Cx40(-/-) mouse, facilitation was seen only at S1S2 of 130 ms (P <.001 vs S1S2 of 150 ms). Evidence of reverse facilitation was documented at S1S2 of 110 and 90 ms. CONCLUSION: Facilitation is observed in wild-type mice. With similar S1S2 intervals in Cx40-deficient mice, facilitation is seen only at longer S1S2 intervals, whereas reverse facilitation is seen at shorter S1S2 intervals, suggesting that Cx40 is involved in the generation of AV nodal facilitation.

Enalapril treatment and hospitalization with atrial tachyarrhythmias in patients with left ventricular dysfunction.

BACKGROUND: Experimental and clinical evidence suggests a preventive role for agiotensin-coverting enzyme (ACE) inhibitors on the development of atrial fibrillation. However, the effect of ACE inhibition on hospitalization with atrial tachyarrhythmias in patients with left ventricular (LV) dysfunction is not known. We sought to determine whether enalapril treatment reduced hospitalizations with atrial tachyarrhythmias in patients with LV dysfunction. METHODS: We performed a retrospective analysis of the Studies of Left Ventricular Dysfunction (SOLVD) trial. Hospitalizations with atrial tachyarrhythmias were noted. RESULTS: A total of 192 hospitalizations with atrial tachyarrhythmias occurred in 158 patients during a follow-up period of 34 months. The time to first hospitalization with atrial tachyarrhythmias or death was significantly lower in the enalapril group (P =.005). In a multivariate analysis adjusting for the presence of atrial fibrillation at study entry, enalapril treatment was associated with a reduction in the rate of hospitalization with atrial tachyarrhythmias or death (RR, 0.87; 95% CI, 0.79-0.96; P =.007). The incidence of hospitalization with atrial tachyarrhythmias was 7.9 hospitalizations per 1000 patient-years of follow-up in the enalapril group, compared with 12.4 per 1000 patient-years in the placebo group (RR, 0.64; 95% CI, 0.48-0.85; P =.002). CONCLUSION: Enalapril is associated with a decreased incidence of hospitalization with atrial tachyarrhythmias in patients with LV dysfunction.

Use of antiarrhythmics and implantable cardioverter-defibrillators in congestive heart failure.

As much as half of the mortality in patients with congestive heart failure (CHF) resulting from left ventricular systolic dysfunction is attributable to sudden cardiac death. Thus, the identification of risk and prevention of sudden death are important components of treating this population of patients. Antiarrhythmic drugs have been shown to be either neutral or harmful when studied in patients with prior myocardial infarction and impaired left ventricular function. Amiodarone, when studied in patients with CHF, may be of benefit. This benefit may be more pronounced in patients with nonischemic cardiomyopathy. Implantable cardioverter defibrillators (ICDs) are of clear benefit when used in the primary and secondary prevention of sudden death in selected populations. Studies soon to be completed should clarify the role of the cardioverter-defibrillator in patients with CHF. Antiarrhythmic medications are often used in conjunction with ICDs for a variety of reasons. However, these drugs have the potential to adversely affect defibrillator function, and knowledge of these effects is important when using this strategy.

Echocardiographic evidence of left atrial abnormality in young patients with lone paroxysmal atrial fibrillation.

Usual assessment of left atrial size by 2-dimensional echocardiography in the anteroposterior dimension often underestimates the true atrial size. We compared 15 young patients (< or =50 years old) with lone paroxysmal atrial fibrillation to age-matched controls, and measured atrial size in the inferosuperior and mediolateral dimensions. These additional measurements and atrial volumes were significantly increased compared with control patients, revealing that patients with apparent "lone" paroxysmal atrial fibrillation may have subtle structural abnormalities of the left atrium.

Adverse cardiovascular events temporally associated with ma huang, an herbal source of ephedrine.

OBJECTIVE: To evaluate possible cardiovascular toxic effects associated with use of dietary supplements containing ma huang, an herbal source of ephedrine. METHODS: We reviewed the comprehensive database Adverse Reaction Monitoring System of the Food and Drug Administration, which included clinical records, investigative reports, and autopsy reports related to ma huang use. The main outcome measurements were stroke, myocardial infarction, and sudden death. RESULTS: From 1995 to 1997, 926 cases of possible ma huang toxicity were reported to the Food and Drug Administration. In 37 patients (23 women and 14 men with a mean +/- SD age of 43 +/- 13 years), use of ma huang was temporally related to stroke (in 16), myocardial infarction (in 10), or sudden death (in 11). Autopsies performed in 7 of the 11 patients who experienced sudden death showed a normal heart in 1, coronary atherosclerosis in 3, and cardiomyopathies in 3. In 36 of the 37 patients, use of ma huang was reported to be within the manufacturers' dosing guidelines. CONCLUSIONS: Analysis of the 37 patients indicates the following findings: (1) ma huang use is temporally related to stroke, myocardial infarction, and sudden death; (2) underlying heart or vascular disease is not a prerequisite for ma huang-related adverse events; and (3) the cardiovascular toxic effects associated with ma huang were not limited to massive doses. Although the pathogenesis of the cardiac toxic effects of ma huang remains incompletely defined, available observational and circumstantial evidence indicates that use of the substance may be associated with serious medical complications.

Clinical results with catheter ablation: AV junction, atrial fibrillation and ventricular tachycardia.

With the limitations of pharmacologic and device therapies for atrial fibrillation and ventricular tachycardia, catheter ablation is assuming a larger role in the management of patients with these common arrhythmias. Multiple case series and clinical trials have helped to define the evolving role of these techniques for ablation of the atrioventricular node, atrial fibrillation, and ischemic ventricular tachycardia. Based on very low complication rates, excellent efficacy and proven outcomes with radiofrequency ablation of the atrioventricular node, this approach with permanent pacing should play a larger role in the treatment of symptomatic patients with permanent atrial fibrillation. While linear ablation of atrial fibrillation has limited clinical utility for the treatment of this common arrhythmia, the results of multiple case series of focal atrial fibrillation ablation indicate the potential for an expanding role of this curative technique. Catheter ablation techniques for ventricular tachycardia in the setting of coronary artery disease have a role as supplemental therapy to the implantable cardioverter defibrillator in patients with recurrent pharmacologically refractory ventricular arrhythmias requiring frequent device interventions.

Frequent ICD shocks due to double sensing in patients with bi-ventricular implantable cardioverter defibrillators.

Biventricular pacing has emerged as a modality for treatment of patients with heart failure. Combined biventricular pacers and implantable cardioverter defibrillators offer treatment of heart failure as well as protection from sudden cardiac death. However, inappropriate ICD shocks as a result of double sensing due to widely spaced ventricular bipoles may pose a significant problem in these patients. We examined the ICD records of twenty-three patients with biventricular ICDs, and evaluated all episodes of double sensing that resulted in aborted or delivered therapy. In follow-up of 3.7 +/- 2.6 months, thirty-three shocks in fifteen episodes occurred in five patients (21.7%) due to double sensing. Four patients (17.4%) had aborted shocks due to double sensing. All episodes resulting in shock occurred because of sinus tachycardia or supraventricular tachycardia above the upper programmed pacing rate of the device with resultant AV conduction and double sensing of the nonpaced ventricular depolarization. In conclusion, double sensing of the R-wave is a common and clinically important cause of inappropriate ICD detection and shock in patients with biventricular ICDs. Appropriate programming of the ICD can prevent episodes of inappropriate shocks.