Mark S. Link

Clinical profile of commotio cordis: an under appreciated cause of sudden death in the young during sports and other activities.

Blunt Chest Impact Leading to Cardiac Arrest. Not particularly well recognized are athletic Held catastrophes in which virtually instantaneous cardiac arrest is produced by nonpenetrating chest blows in the absence of heart disease or identifiable morphologic injury to the chest wall or heart (commotio cordis). To better characterize the clinical profile of this syndrome, we have assembled 70 cases, including 34 occurring during organized competitive athletics and 36 others that occurred during informal recreational sports at home, school or the playground, or during nonsporting activities. Ages were 2 to 38 (mean age: 12) with 70% < 16 years old. Most common sports involved were youth baseball (n = 40), softball (n = 7), and ice hockey (n = 7). Seven (10%) of the 70 commotio cordis victims, including six with documented ventricular fibrillation, have survived the consequences of their chest blow. Eleven of the events (16%) occurred despite the presence of chest padding believed to be potentially protective. Four victims experienced modest chest blows while in circumstances completely unrelated to sports activities; three of the four individuals who delivered these blows were ultimately convicted of criminal acts within the justice system. An experimental model of low‐energy chest wall impact demonstrates that commotio cordis events are due largely to the exquisite timing of blows during a narrow window within the repolarization phase of the cardiac cycle, 15 to 30 msec prior to the peak of the T wave.

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.

Connexin40‐Deficient Mice Exhibit Atrioventricular Nodal and Infra‐Hisian Conduction Abnormalities

AV Nodal and Infra‐Hisian Conduction in Cx40 Mice. Introduction: Previous electrophysiologic investigations have described AV conduction disturbances in connexin4(Cx40)‐deficient mice. Because expression or(Cx40 occurs predominantly in the atria and His‐Purkinje system of the mouse heart, the AV conduction disturbances were thought to be secondary to disruption in His‐Pnrkinje function. However, the lack of a His‐bundle electrogram recording in the mouse has limited further investigation of the importance of Cx40. Using a novel technique to record His‐bundle recordings in Cx40‐deficient mice, we define the physiologic importance of defciencies in Cx40.

Athletes and arrhythmias.

Athletes and Arrhythmias. Athletes are thought the healthiest segment of the population. Yet, there is a general appearance that athletes are more prone to sudden cardiac death and arrhythmias than nonathletes. Bradycardias in athletes are nearly universal, but advanced heart block is usually pathologic. Athletes may be more prone to atrial fibrillation, but not likely to other types of supraventricular tachycardias. Sudden cardiac death in athletes is rare in the absence of heart disease, with the exception of commotio cordis. Treatment strategies for athletes are focused for the return to athletics. Guidelines for treatment will be derived from the 36th Bethesda Guidelines for athletes, and the European Society of Cardiology (ESC) guidelines for athletes. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1184‐1189)

Role of Streptomycin-Sensitive Stretch-Activated Channel in Chest Wall Impact Induced Sudden Death (Commotio Cordis)

Introduction: Deaths secondary to low‐energy impacts to the precordium in young individuals (commotio cordis) have been reported with increasing frequency. In a swine model, baseball impacts induce ventricular fibrillation when directed at the center of the left ventricle during the vulnerable portion of repolarization just prior to the T‐wave peak. It has been hypothesized that activation of stretch‐sensitive channels could be crucial for this electrophysiological phenomenon. In this study, a nonselective stretch‐activated cation channel was pharmacologically blocked prior to chest blows to determine whether this channel represents a possible pathway by which commotio cordis events occur.

Cell Membrane Stretch and Chest Blow‐Induced Ventricular Fibrillation: Commotio Cordis

Introduction: Commotio cordis, sudden cardiac death secondary to blunt nonpenetrating chest blows in sports, is reported with increasing frequency. In a swine model, ventricular fibrillation (VF) is induced by a baseball blow to the chest, and the initiation of VF is related to the peak left ventricular (LV) pressure produced by the blow. LV pressure changes likely result in cell membrane stretch and mechanical activation of ion channels. Disruption of cell cytoskeleton that anchors the cell membrane prior to precordial blows offers the opportunity to explore whether cell membrane deformation is critical to commotio cordis.

Safety and Efficacy of a Steerable Temperature Monitoring Microwave Catheter System for Ventricular Myocardial Ablation

Microwave Ablation of Canine Ventricle. Introduction: Radiofrequency current delivered during cardiac ablation is limited by a rise in impedance secondary to coagulum formation on the ablation electrode. Microwave antennas continue to deliver energy despite the presence of coagulum; thus, temperature control of the ablation electrode may be even more important for microwave than for radiofrequency ablations to avoid thromboembolic risks. The purpose of this study was to test the safety and efficacy of an ablation system utilizing a feedback control system to maintain a fixed target temperature for creating lesions with multiple applications of microwave energy.

Microwave ablation using a spiral antenna design in a porcine thigh muscle preparation: in vivo assessment of temperature profile and lesion geometry.

Microwave Ablation with Spiral Antenna Design. Introduction: Theoretical studies have suggested that microwave energy can increase the depth of heating compared with radiofrequency energy. A spiral microwave antenna design may have advantages over previous designs using smaller designs because the resulting power deposition pattern is considerably larger than the catheter diameter. We tested the efficacy of a spiral antenna using microwave energy in a porcine thigh muscle preparation.

Cardiac Safety of Electrical Stun Guns: Letting Science and Reason Advance the Debate

The authors reflect on the cardiac safety of electrical stun guns. They commented that the role of biologic models in evaluating the cardiac effects of Taser plays greater importance with the limitations of the epidemiologic data, clinical investigations and theoretical arguments. They added that the debate over the use of Taser is confounded by lack of sufficient scientific evidence to make firm conclusions on the potential of adverse cardiac effects.

Cardiac electrophysiologic abnormalities in the CREBA133 transgenic mouse model of idiopathic dilated cardiomyopathy.

Introduction: We hypothesized that the transgenic mice expressing a dominant‐negative form of the CREB transcription factor (CREBA133) under the control of the cardiac myocyte‐specific α‐MHC promoter and displaying dilated cardiomyopathy would exhibit electrophysiologic abnormalities similar to those observed in human cardiomyopathy.