Param P. Sharma

Coronary no-flow and ventricular tachycardia associated with habitual marijuana use

A 34-year-old man reported heart fluttering and near syncope a few hours after marijuana smoking. In the emergency department, he was found to have a right bundle-branch-type ventricular tachycardia. The patient underwent a successful electric cardioversion. Coronary angiography showed no pericardial artery stenosis yet very slow coronary blood flow. Clinical tachycardia was also inducible in the electrophysiologic laboratory. After verapamil therapy and cessation of marijuana, his coronary flow normalized and ventricular tachycardia was no longer inducible in the electrophysiologic laboratory. Marijuana use might affect coronary microcirculation and cause ventricular tachycardia. Verapamil therapy and cessation of smoking might be curative.

Swallow Syncope: A Case Report and Review of the Literature

Swallow or deglutition syncope is a relatively rare syndrome. It is a vagally mediated syncope induced by swallowing. Swallow syncope may occur in all age groups and, when diagnosed, is treatable. A woman, aged 60 years, presented with an episode of a syncopal attack associated with swallowing a sandwich. She had a 6-month history of recurrent episodes of lightheadedness while eating solid foods. Telemetry monitoring demonstrated several episodes of severe bradycardia and complete atrioventricular block with up to a 7.0 second pause associated with meals. Computed tomography of the head and neck revealed no significant findings, and barium esophagram was normal. Echocardiogram was within normal limits. Her symptoms resolved after permanent pacemaker placement. Herein, we review the diagnosis, mechanism, and management of swallow syncope.

Longitudinal study of implantable cardioverter-defibrillators: methods and clinical characteristics of patients receiving implantable cardioverter-defibrillators for primary prevention in contemporary practice

Background—Implantable cardioverter-defibrillators (ICDs) are increasingly used for primary prevention after randomized, controlled trials demonstrating that they reduce the risk of death in patients with left ventricular systolic dysfunction. The extent to which the clinical characteristics and long-term outcomes of unselected, community-based patients with left ventricular systolic dysfunction undergoing primary prevention ICD implantation in a real-world setting compare with those enrolled in the randomized, controlled trials is not well characterized. This study is being conducted to address these questions. Methods and Results—The study cohort includes consecutive patients undergoing primary prevention ICD placement between January 1, 2006 and December 31, 2009 in 7 health plans. Baseline clinical characteristics were acquired from the National Cardiovascular Data Registry ICD Registry. Longitudinal data collection is underway, and will include hospitalization, mortality, and resource use from standardized health plan data archives. Data regarding ICD therapies will be obtained through chart abstraction and adjudicated by a panel of experts in device therapy. Compared with the populations of primary prevention ICD therapy randomized, controlled trials, the cohort (n=2621) is on average significantly older (by 2.5–6.5 years), more often female, more often from racial and ethnic minority groups, and has a higher burden of coexisting conditions. The cohort is similar, however, to a national population undergoing primary prevention ICD placement. Conclusions—Patients undergoing primary prevention ICD implantation in this study differ from those enrolled in the randomized, controlled trials that established the efficacy of ICDs. Understanding a broad range of health outcomes, including ICD therapies, will provide patients, clinicians, and policy makers with contemporary data to inform decision-making.

Familial Atrioventricular Nodal Reentry Tachycardia

Dual atrioventricular nodal pathways, the substrate responsible for atrioventricular node reentry tachycardia (AVNRT), are thought to be randomly occurring congenital anomalies. This article describes 14 patients in six families, each with two or three first‐degree relatives with paroxysmal supraventricular tachycardia. Electrophysiological evidence of dual atrioventricular nodal pathways was established in all 13 patients studied, AVNRT was induced in 12 (92%), and radiofrequency ablation of the slow pathway was curative in all cases. The data suggest a hereditary contribution to the development of atrioventricular nodal pathways and AVNRT. The pattern of inheritance appears to be autosomal dominant. (PACE 2004; 27:73–76)

Atrial Flutter Versus Atrial Fibrillation in a General Population: Differences in Comorbidities Associated With Their Respective Onset

Objective: Determine and compare the prevalence of known risk factors for cardiovascular disease among unselected individuals presenting with their first ever episode of atrial flutter (AFL) and atrial fibrillation (AF). Study Design and Setting: We evaluated 11 pre-selected clinical variables including age, sex, smoking history and other potential cardiac risk factors. Using the resources of the Marshfield Epidemiologic Study Area, a population-based database, all newly diagnosed cases of either AFL or AF in the region during a 4-year period were identified. Results: Among the 472 incident cases, 76 (16.1%) had AFL and 396 (83.9%) had AF. Compared to those with AF, subjects with AFL were more likely to have had a history of chronic obstructive pulmonary disease (25% vs. 12%, P = 0.006), heart failure (28% vs. 17%, P = 0.05), and smoking (49% vs. 37%, P = 0.06). Hypertension, on the other hand, was more common among individuals with AF (63% vs. 47%, P = 0.01). Conclusion: This study represents the first report to evaluate potential differences in the conditions associated with the development of AFL versus AF. Research into the mechanisms of atrial arrhythmogenesis may lead to improved preventive and therapeutic interventions.

Catheter Ablation in the Elderly in the United States: Use in the Medicare Population from 1991 to 1998

SMITH, P.N., et al.: Catheter Ablation in the Elderly in the United States: Use in the Medicare Population from 1991 to 1998. The safety and efficacy of catheter ablation for the treatment of drug refractory cardiac arrhythmias is well established in young patients. Little is known about its effectiveness or use in the elderly. We determined trends in the use of catheter ablation in the United States Medicare population. Data were obtained from the approximately 30 million patients covered each year by Medicares fee‐for‐service program of the Health Care Financing Administration of the Department of Health and Human Services. From 1991 to 1998, Medicares fee‐for‐service beneficiaries covered 80%–93% of all adults > 65 years old in the United States. All catheter‐based ablative procedures performed in this population were identified through the use of the Current Procedural Terminology codes 93650, 93651, and 93652. Use rate per 1 million beneficiaries grew from 33 in 1991 to 603 in 1998. While during this 7‐year period the Medicare fee‐for‐service population decreased by 8%, ablations increased 16‐fold (1,608%). The use of catheter ablation in the older American grew exponentially during the 1990s. Further research is needed to determine the optimal use of this potentially curative technique in the elderly.

Patient with Sotos syndrome, Wolff-Parkinson-White pattern on electrocardiogram, and two right-sided accessory bypass tracts

Sotos syndrome is a growth regulation disorder. Accessory conduction pathways, the anatomical structures responsible for Wolff‐Parkinson‐White syndrome, are thought to result from developmental failure to eradicate the remnants of the atrioventricular connections during cardiogenesis. Although the reported prevalence of congenital heart disease in Sotos syndrome is 10 times higher than in the general population, there are no reported cases with ventricular pre‐excitation. We report a patient with Sotos syndrome with two distinct accessory atrioventricular bypass tracts documented by invasive electrophysiology testing and a curative catheter ablation procedure.

Device Therapies Among Patients Receiving Primary Prevention Implantable Cardioverter‐Defibrillators in the Cardiovascular Research Network

Background Primary prevention implantable cardioverter‐defibrillators (ICDs) reduce mortality in selected patients with left ventricular systolic dysfunction by delivering therapies (antitachycardia pacing or shocks) to terminate potentially lethal arrhythmias; inappropriate therapies also occur. We assessed device therapies among adults receiving primary prevention ICDs in 7 healthcare systems. Methods and Results We linked medical record data, adjudicated device therapies, and the National Cardiovascular Data Registry ICD Registry. Survival analysis evaluated therapy probability and predictors after ICD implant from 2006 to 2009, with attention to Centers for Medicare and Medicaid Services Coverage With Evidence Development subgroups: left ventricular ejection fraction, 31% to 35%; nonischemic cardiomyopathy <9 months’ duration; and New York Heart Association class IV heart failure with cardiac resynchronization therapy defibrillator. Among 2540 patients, 35% were <65 years old, 26% were women, and 59% were white. During 27 (median) months, 738 (29%) received ≥1 therapy. Three‐year therapy risk was 36% (appropriate, 24%; inappropriate, 12%). Appropriate therapy was more common in men (adjusted hazard ratio [HR], 1.84; 95% confidence interval [CI], 1.43–2.35). Inappropriate therapy was more common in patients with atrial fibrillation (adjusted HR, 2.20; 95% CI, 1.68–2.87), but less common among patients ≥65 years old versus younger (adjusted HR, 0.72; 95% CI, 0.54–0.95) and in recent implants (eg, in 2009 versus 2006; adjusted HR, 0.66; 95% CI, 0.46–0.95). In Centers for Medicare and Medicaid Services Coverage With Evidence Development analysis, inappropriate therapy was less common with cardiac resynchronization therapy defibrillator versus single chamber (adjusted HR, 0.55; 95% CI, 0.36–0.84); therapy risk did not otherwise differ for Centers for Medicare and Medicaid Services Coverage With Evidence Development subgroups. Conclusions In this community cohort of primary prevention patients receiving ICD, therapy delivery varied across demographic and clinical characteristics, but did not differ meaningfully for Centers for Medicare and Medicaid Services Coverage With Evidence Development subgroups.

Implantable Cardiac Defibrillator Placement in a Patient with Persistent Left Superior Vena Cava and Brugada Syndrome

A 45-year-old man was diagnosed with new-onset atrial fibrillation. Control of ventricular rate led to spontaneous conversion to sinus rhythm. Subsequent electrocardiograms revealed ST segment changes characteristic of Brugada syndrome. Electrophysiology study demonstrated inducible ventricular fibrillation. During the placement of an implantable cardiac defibrillator the patient was found to have a persistent left superior vena cava. Persistent left superior vena cava is present in 0.3% of cases in autopsy series. To date, persistent left superior vena cava has not been reported in association with Brugada syndrome. We report such a case.

Comparison of Inappropriate Shocks and Other Health Outcomes Between Single- and Dual-Chamber Implantable Cardioverter-Defibrillators for Primary Prevention of Sudden Cardiac Death: Results From the Cardiovascular Research Network Longitudinal Study of Implantable Cardioverter-Defibrillators

Background In US clinical practice, many patients who undergo placement of an implantable cardioverter‐defibrillator (ICD) for primary prevention of sudden cardiac death receive dual‐chamber devices. The superiority of dual‐chamber over single‐chamber devices in reducing the risk of inappropriate ICD shocks in clinical practice has not been established. The objective of this study was to compare risk of adverse outcomes, including inappropriate shocks, between single‐ and dual‐chamber ICDs for primary prevention. Methods and Results We identified patients receiving a single‐ or dual‐chamber ICD for primary prevention who did not have an indication for pacing from 15 hospitals within 7 integrated health delivery systems in the Longitudinal Study of Implantable Cardioverter‐Defibrillators from 2006 to 2009. The primary outcome was time to first inappropriate shock. ICD shocks were adjudicated for appropriateness. Other outcomes included all‐cause hospitalization, heart failure hospitalization, and death. Patient, clinician, and hospital‐level factors were accounted for using propensity score weighting methods. Among 1042 patients without pacing indications, 54.0% (n=563) received a single‐chamber device and 46.0% (n=479) received a dual‐chamber device. In a propensity‐weighted analysis, device type was not significantly associated with inappropriate shock (hazard ratio, 0.91; 95% confidence interval, 0.59–1.38 [P=0.65]), all‐cause hospitalization (hazard ratio, 1.03; 95% confidence interval, 0.87–1.21 [P=0.76]), heart failure hospitalization (hazard ratio, 0.93; 95% confidence interval, 0.72–1.21 [P=0.59]), or death (hazard ratio, 1.19; 95% confidence interval, 0.93–1.53 [P=0.17]). Conclusions Among patients who received an ICD for primary prevention without indications for pacing, dual‐chamber devices were not associated with lower risk of inappropriate shock or differences in hospitalization or death compared with single‐chamber devices. This study does not justify the use of dual‐chamber devices to minimize inappropriate shocks.