Cardiology in review
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Although thought to be rare, sudden deaths caused by nonpenetrating chest wall impact in the absence of structural injury to the ribs, sternum, and heart (commotio cordis) are reported with increasing frequency. This phenomenon is described in individuals when they are struck by relatively innocent blows to the chest wall. Young male athletes aged 5 to 18 years are particularly at risk for this catastrophe. ⋯ Death is usually instantaneous, and successful resuscitation is uncommon. A recently reported experimental model provides clues to the mechanisms and inferences for the prevention and treatment of this devastating condition. This swine model shows that a) ventricular fibrillation results from low-energy chest wall impacts during a vulnerable period of repolarization, b) the risk of this event can be decreased with softer-than-standard baseballs, and c) prompt defibrillation is crucial for resuscitation to be successful.
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The inherited long QT syndrome is caused by mutations of at least 5 ion channel genes. Mutations of the cardiac sodium ion channel gene and 3 potassium channel genes have been identified to this time. A genetic locus on chromosome 4 has been identified, but no gene has been discovered as of yet. ⋯ The principal treatment is beta-blocker therapy. Appropriate dosing, with ascertainment of efficacy and compliance with administration, are the key elements in therapeutic success. Molecular physiology-based strategies are being considered, including the use of sodium channel blockers in LQT3 and potassium administration in LQT1 patients.