Cardiac electrophysiology and the athlete: a primer for the sports clinician.

Intense exercise requires a significant increase in cardiac output in order to meet the needs of the skeletal muscles for oxygenated blood. In order to improve cardiac performance, the autonomic nervous system increases sympathetic tone primarily through release of norepinephrine from postganglionic receptors to stimulate the ß-adrenergic receptors of the nodal and muscle tissue of the heart. This event initiates a signaling cascade focused on increasing the amount of calcium available to the contractile myofilaments in the cardiac cell. Failure of the myocytes to counterbalance the increase in inward ion flow or adequately sequester cytosolic calcium during diastole leads to potentially catastrophic electrical instability. In this review, the relationship between the cellular events initiated by exercise and the induction of arrhythmias associated with the long QT, Brugada, and Wolff-Parkinson-White syndromes; catecholaminergic polymorphic ventricular tachycardia; and the heritable cardiomyopathies are explored.

Surveillance for febrile respiratory infections during Cobra Gold 2003.

The Naval Health Research Center conducted laboratory-based surveillance for febrile respiratory infections at the 2003 Cobra Gold Exercise in Thailand. Seventeen individuals met the case definition for febrile respiratory illness, and diagnostic specimens were obtained from 16. Laboratory testing identified influenza A for 44%; sequence analysis demonstrated that these were Fujian-like influenza strains, which represented the predominant strain found globally in 2003/2004. Other pathogens identified included coronavirus OC43, respiratory syncytial virus, and rhinovirus. Logistical challenges were overcome as laboratory-supported febrile respiratory illness surveillance was conducted during a military training exercise. With heightened concern over the potential for another global influenza pandemic, such surveillance could prove critical for the detection of emerging influenza and respiratory pathogen strains with potential for importation to the United States.