William J. Welch

Tachyarrhythmias in young athletes.

Nineteen young athletes with documented symptomatic tachyarrhythmia were systematically evaluated. There were 15 men and 4 women, aged 14 to 32 years (mean 22 +/- 6). Documented tachyarrhythmias were paroxysmal atrial fibrillation in five patients, paroxysmal supraventricular tachycardia in five, paroxysmal ventricular tachycardia in eight (sustained in five, nonsustained in three) and ventricular fibrillation in one patient. Abnormal substrates were demonstrated in 15 (79%) of the 19 athletes: 5 had an anomalous atrioventricular (AV) pathway and 10 had heart disease (mitral valve prolapse in 9 patients and dilated cardiomyopathy in 1 patient). In 13 (68%) of the 19 athletes, all spontaneous attacks of tachyarrhythmia had started during strenuous exercise. Tachyarrhythmia that closely resembled clinical arrhythmia was induced by programmed cardiac stimulation in 13 athletes (68%) and was reproducibly provoked by treadmill exercise in 8 athletes (42%). In four of seven athletes with ventricular tachycardia, tachycardia closely resembling clinical arrhythmia was provoked by infusion of isoproterenol. In summary: young athletes can have any of several tachyarrhythmias; abnormal substrates can be demonstrated in many athletes with symptomatic tachyarrhythmia; and tachyarrhythmias in young athletes frequently occur during exercise.

Lack of effectiveness of oral mexiletine in patients with drug-refractory paroxysmal sustained ventricular tachycardia: A study utilizing programmed stimulation

Abstract Recent studies indicate that oral administration of mexiletine is useful in the therapy of recurrent ventricular tachycardia (VT). To further define the clinical usefulness of this drug, mexiletine was administered to 13 men and 4 women with a mean age ± standard deviation of 62 ± 8 years who had drug-refractory paroxysmal sustained VT associated with chronic ischemic heart disease in 14, valvular heart disease in 1, and primary myocardial disease in 1. One patient had no heart disease. All 17 patients had inducible sustained VT during the control electrophysiologic study and during serial electrophysiologic study on conventional drugs. Eleven patients tolerated a mean maximal daily dose of 1,073 ± 149 mg of mexiletine and underwent programmed ventricular stimulation; sustained VT was inducible in 10 patients and nonsustained VT in 1. in 10 patients with inducible sustained VT on mexiletine, the VT cycle length was longer during mexiletine therapy than during control (mean ± standard error of the mean, 342 ± 22 versus 268 ± 14 ms, respectively) (p

Doxepin Induced Torsade De Pointes

A case of torsade de pointes with normal QT interval secondary to the administration of small amounts of doxepin is presented. Electrophysiological studies during rechallenge with doxepin demonstrated replication of the patients spontaneous arrhythmia. Evaluation of syncope in patients taking doxepin should include careful evaluation for torsade de pointes.

Long-term therapy with disopyramide phosphate: Side effects and effectiveness☆

In this study, the safety and efficacy of long-term therapy with disopyramide phosphate were evaluated in 40 patients with documented, recurrent, symptomatic tachyarrhythmias. Twenty-one (53%) of the patients had organic heart disease, and nine of these patients had compensated congestive heart failure. The tachyarrhythmias which were treated were paroxysmal supraventricular tachycardia (21 patients), paroxysmal atrial fibrillation (six patients), and paroxysmal ventricular tachycardia (13 patients). In each patient there was evidence, from continuous ECG monitoring or electrophysiologic testing, that disopyramide would be effective therapy, and each patient was able to tolerate disopyramide (no side effects or tolerable side effects) during an initial trial period of 1 to 2 weeks. Dosages of disopyramide were 400 to 1600 mg/day (994 +/- 320 mm/day). During long-term therapy, side effects were reported by 28 (70%) of the patients. The side effects were usually anticholinergic, and were usually a continuation of side effects noted during the initial trial period. None of the patients had idiosyncratic reactions to disopyramide. Most of the patients found side effects to be tolerable; however, in seven patients it was necessary to discontinue disopyramide after 1 to 8 (6 +/- 3) months. Actuarial incidence of intolerable side effects was 21 +/- 7% at 12 months. Nine (22%) of the 40 patients had symptomatic recurrences of tachyarrhythmia after 3 to 32 (15 +/- 9) months of therapy. Actuarial incidence of drug ineffectiveness was 32 +/- 10% at 24 months. Disopyramide was both effective and tolerated in 24 (60%) of the patients, who were followed for 2 to 64 (23 +/- 16) months.(ABSTRACT TRUNCATED AT 250 WORDS)

Cumulative effects of cycle length on ventricularrefractoriness in man

This study examined the time course of changes of ventricular effective refractory period (VERP) following an abrupt change of cycle length (CL) in man. Stimulation at the right ventricular apex consisted of 19 cycles of an initial CL, followed by a variable number of cycles (0 to 50 cycles) of a new CL, and an extrastimulus to test for VERP. Fifteen patients were enrolled in each part of the study. In part A, initial CLs were long (mean +/- standard error, 650 +/- 20 msec) and new CLs were short (325 +/- 10 msec). VERPs were 259 +/- 6 msec after the long cycles, 238 +/- 6 msec after one short cycle (p less than 0.05), 224 +/- 5 msec after 10 short cycles, and 210 +/- 6 msec after 50 short cycles (p less than 0.05 versus 1 or 10 short cycles). Thus 43% of total shortening of VERP occurred in the first short cycle and 57% occurred in subsequent short cycles. In part B, initial CLs were short and new CLs were long. VERPs were 212 +/- 7 msec after the short cycles, 237 +/- 7 msec after one long cycle (p less than 0.05), 239 +/- 7 msec after 10 long cycles, and 247 +/- 7 msec after 50 long cycles (p less than 0.05 versus 1 or 10 long cycles). Thus 71% of total lengthening of VERP occurred in the first long cycle and 29% occurred in subsequent long cycles. In conclusion, following an abrupt change of CL in man, VERP changes markedly in the first new cycle (immediate effect) and then undergoes further, more gradual change over a large number of subsequent cycles (cumulative effects). Cumulative effects appear to be greater following shortening of CL than following lengthening of CL.

Paroxysmal fascicular tachycardia and ventricular tachycardia due to mechanical stimulation by a mitral valve prosthesis

Electrophysiologic studies were performed in a woman who had two varieties of paroxysmal wide QRS tachycardia after mitral valve replacement with a Starr-Edwards prosthesis. One tachycardia originated in the left anterior fascicle; QRS complexes were 100 ms wide and resembled right bundle branch block with left posterior fascicular block, and a His bundle potential preceded each QRS by an interval of 20 ms (compared with 50 ms during sinus rhythm). The other tachycardia originated in the left ventricle. Clinical and echocardiographic observations suggested that the tachycardias were caused by mechanical stimulation of the interventricular septum by the mitral prosthesis.