Biomedical subjects

Jonathan Weinstock

Publications and source records attributed to Jonathan Weinstock.

9 recordsLinked to original sources

PubMed2007

Commotio cordis--sudden cardiac death with chest wall impact.

Commotio cordis (CC), sudden death as a result of a blunt, often innocent-appearing chest wall blow, is being reported with increasing frequency. The clinical spectrum is diverse; however, a substantial number of cases occur in youth athletics. In events that occur during sport, victims are struck by projectiles regarded as standard implements of the game. Sudden death is instantaneous and victims are most often found in ventricular fibrillation (VF). Overall survival is poor; however, successful resuscitation can be achieved with early defibrillation. Autopsy is notable for the absence of any significant cardiac or thoracic injury. Development of an experimental model has allowed for substantial insights into the underlying mechanisms of sudden death. In anesthetized juvenile swine, induction of VF is instantaneous following chest wall blows occurring during a vulnerable window before the T wave peak. Crucial variables including the velocity of impact, impact location, and hardness of the impact object have been identified. Rapid left ventricular (LV) pressure rise following chest impact likely results in activation of ion channels via mechano-electric coupling. The generation of inward current via mechano-sensitive ion channels likely results in augmentation of repolarization and nonuniform myocardial activation, and is the cause of premature ventricular depolarizations that are triggers of VF in CC. While softer-than-standard safety baseballs reduce the risk of CC, commercially available chest protectors are ineffective in preventing CC. The development of more effective chest protectors and more widespread use of automated external defibrillators at youth sporting events are needed.

Death, Sudden, Cardiac↗

PubMed2006

Failure of commercially available chest wall protectors to prevent sudden cardiac death induced by chest wall blows in an experimental model of commotio cordis.

OBJECTIVE: Sudden cardiac death that results from chest wall blows (commotio cordis) the second leading cause of death in young athletes. Most events are caused by blows from projectiles, such as baseballs or lacrosse balls, with a substantial proportion occurring despite the use of a chest protector. In the present experiment, we tested the effectiveness of commercially available chest protectors in preventing ventricular fibrillation (VF) that results from chest wall strikes with baseballs and lacrosse balls. METHODS: Twelve different baseball or lacrosse chest protectors were evaluated in juvenile swines that were subjected to 40-mph baseball or lacrosse ball blows to the precordium during the vulnerable period of repolarization for VF and were compared with control impacts without chest protectors. Seven baseball chest protectors were hit by regulation baseballs, and 5 lacrosse chest protectors were tested by blows with standard lacrosse balls. Each animal received 2 chest blows for each protector and 2 control impacts without a chest protector, with the sequence of impacts assigned randomly. RESULTS: VF was elicited by 12 (32%) of 37 strikes in control animals without baseball chest protectors. None of the baseball chest wall protectors tested were shown to decrease significantly the occurrence of VF when compared with controls. VF was elicited by 11 (46%) of 24 strikes in control animals without lacrosse chest protectors. None of the lacrosse chest wall protectors tested decreased significantly the occurrence of VF when compared with controls. CONCLUSION: In our experimental animal model of commotio cordis, commercially available baseball and lacrosse chest wall protectors were ineffective in protecting against VF that was triggered by chest blows and, by inference, sudden cardiac death. Improvements in materials and design of chest wall barriers are necessary to reduce the occurrence of these tragic events and make the athletic field safer for youths.

Adolescent↗

PubMed2006

Treatment of athletes with cardiac disease or arrhythmias.

Ventricular arrhythmias and sudden cardiac death in the athlete are uncommon but extremely visible because of the high profile of amateur and professional athletes. In athletes under the age of 30 years, the incidence of sudden death is low and in most cases occurs in individuals with inherited heart disease. In the older athlete, sudden death is more common and is generally due to arrhythmias in the context of coronary artery disease. Many athletes with aborted sudden death, arrhythmia-related syncope, or high-risk genetic disorders benefit from therapy with implantable cardioverter-defibrillators (ICDs). Although ICD therapy can effectively abort sudden death, implantation of an ICD generally prohibits an individual from all competitive athletics except low-intensity sports. Recommendations for participation in competitive athletics generally follow the recently published 36th Bethesda Conference Eligibility Recommendations for Competitive Athletes with Cardiovascular Abnormalities.

Journal Article↗

PubMed2005

Effectiveness of automated external defibrillators in high schools in greater Boston.

A program using a strategy of donating a single automatic external defibrillator to 35 schools in the Boston area resulted in compliance with American Heart Association guidelines on automatic external defibrillator placement and training and 2 successful resuscitations from sudden cardiac arrest. Participating schools indicated a high degree of satisfaction with the program.

Adolescent↗

PubMed2005

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.

Androstenedione↗

PubMed2005

Device trials in heart failure: a focused summary.

Despite considerable progress in heart failure management with pharmacologic agents, measures to bring about significant improvements in morbidity and mortality are still needed. Cardiac resynchronization therapy (CRT) is a means to enhance myocardial function by stimulating the failing left ventricle at or near the time of right ventricular activation to synchronize ventricular depolarization. Current data from randomized, controlled trials suggest that CRT benefits patients with moderate to severe heart failure and have shown that this therapy significantly reduces mortality and hospital admissions in this group. In addition to CRT, implantable cardioverter-defibrillators have been evaluated in heart failure patients with significantly reduced left ventricular function and have been shown to reduce mortality from sudden cardiac death. This article summarizes recent device trials and discusses how best to apply their results to clinical practice.

Cardiac Pacing, Artificial↗

PubMed2003

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.

Anti-Arrhythmia Agents↗

PubMed2003

Herbal medicine: beneficial effects, side effects, and promising new research in the treatment of arrhythmias.

Herbal medications and dietary supplements are unregulated in the United States. The use of these medications has dramatically increased over the past decade. Many of these drugs are biologically active, yet physicians are often unaware their patients are using a traditional remedy. Physicians are frequently unfamiliar with the medications being used and the intended effect, as well as the side-effect profiles that accompany them. Recently, some of the herbal mediations that are commonly used in the general population have been shown to be beneficial for the treatment of arrhythmias. Unfortunately, many more have been shown to be detrimental. In this article, the background behind herbal medication and the degree to which herbal medications are being used is reviewed. Herbal medications known to have beneficial effects in the treatment of arrhythmias, as well as those that have known detrimental effects with regard to cardiac arrhythmias, are highlighted. Finally, research that has been done in this field, focusing on those compounds that have been shown to be biologically active in the treatment of cardiac arrhythmias, are reviewed.

Arrhythmias, Cardiac↗

PubMed2003

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.

Atrial Fibrillation↗