ECG Quiz Answer: Collapse in a Young Runner
Matthew F. Davis, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 25 - NO. 7 - JULY 97
This patient suffered cardiac arrest from ventricular fibrillation, as figure 1 reveals. She was successfully defibrillated at the scene. She had severe short-term memory loss for several days after her cardiac event, but experienced no other residual effects.
Appropriate tests in young athletic patients who have ventricular arrhythmias are those that reveal congenital and electrical abnormalities such as hypertrophic or other cardiomyopathies, congenital valvular disease, long QT syndrome, and Wolff-Parkinson-White syndrome (1). Accordingly, tests ordered for this patient included a resting ECG, 24-hour ambulatory ECG monitoring, echocardiography, and an exercise treadmill test.
Her resting ECG shows T-wave inversions and high QRS voltage (figure 3), which would indicate disease in nonathletic or older patients, but are common findings among trained athletes. Subsequent ambulatory ECG monitoring showed no abnormalities. The patient's echocardiogram showed no evidence of obstructive cardiomyopathy or other anomaly, and her Bruce protocol treadmill test was normal.
Many cardiologists also recommend coronary angiography, cardiac biopsy, and electrophysiologic studies for athletic patients who have ventricular arrhythmias that cannot be explained with noninvasive tests (2,3). All of these studies were done. The only abnormality found was second degree heart block (Mobitz type I atrioventricular block), seen during the electrophysiologic study. Up to 10% of trained athletes may exhibit this characteristic as a normal variant (4).
The patient's condition was diagnosed as idiopathic ventricular fibrillation. In nearly 20% of young patients who have ventricular fibrillation, no specific cause can be found. Ventricular fibrillation recurs in 30% of these patients (3), and a recent trial showed a survival advantage of 25% over 3 years for implantable cardioverter-defibrillators (ICD) over antiarrhythmia medications in patients who had ventricular arrhythmias (5). Therefore, an ICD is the treatment of choice. Prior to discharge, the patient had an ICD placed and was instructed to limit her exercise to moderately dynamic sports. Her short-term memory loss resolved, and she was discharged from the hospital after 8 days. At a 3- month follow-up visit she had had no further episodes of arrhythmia.
Dr Davis is a senior resident in the department of medicine at the University of Florida in Gainesville. Address correspondence to Matthew F. Davis, MD, Senior Resident, University of Florida Department of Medicine, 5240 SW 92nd Ct, Gainesville, FL 32608; e-mail to [email protected].
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