Exercise is an important composing ...

Exercise is an important composing in the medical management and rehabilitation of patients with coronary artery disease. The salutary consequences of chronic aerobic exercise training are well-documented.[1,2] upon the other hand, there is more than anecdotal evidence of an association between vigorous physical exertion and quick cardiac death. Reports have appeared in the couple the medical literature[3] and the lay press[4] suggesting that vigorous physical activity may actually precipitate myocardial infarction or cardiac arrest in excellented persons.

Pathophysiologic evidence glance ats that exercise, by increasing myocardial oxygen consumption and simultaneously shortening diastole and coronary perfusion time, may provoke a transient oxygen deficiency at the subendocardial plain which is exacerbated by abrupt cessation of activity. In addition, ischemia, sodium-potassium imbalance, increased catecholamine excertion, and circulating released fatty acids all may be arrhythmogenic (Fig 1)[5-7]

Untoward marked occurrences have been reported to be reasonably attend much [i]or[/i] regularly during cardiac exercise programs.[8,9] For patients with coronary artery disease, the relative risk of developing cardiac arrest during vigorous exercise is estimated to be 6 to 164 times greater than what might be count uponed to occur spontaneously.[10] Exertion-related cardiac arrest is typically fit to an arrhythmic event of that kind as ventricular fibrillation, rather than acute myocardial infarction.

Although the use of of great price continuous ECG monitoring as a routine manner of proceeding in cardiac exercise programs newly has been challenged,[11,12] particularly in "low-risk" patients, instantaneous electrocardiography[13] can be used to completeness an outpatient gymnasium program by means of providing valuable surveillance data to program staff and referring physicians. Accordingly, we have occupyed this "spot-monitoring technique" (recording ECG rate, regular [i]or[/i] melodious movement and repolarization through defibrillator paddles; Fig 2) in our cardiac exercise program for several years and have plant it to be an effective way to sieve for ST-segment displacement, threatening ventricular arrhythmias and exercise intensity violators.

The following case report demonstrates the value of instantaneous ECG monitoring in detecting exercise-related ventricular tachycardia in a postmyocardial infarction patient, despite concomitant improvement in functional capacity resulting from a cardiac rehabilitation program.

Case Report

A 60-year-old white man with a history of angina pectoris, congestive heart failure, non-insulin conditioned diabetes, and hypercholesterolemia, sustained a transmural anteroapical wall myocardial infarction onward October 25, 1986. Cardiac catheterization, performed brace days later revealed 80 percent stenosis of the proximal left anterior descending coronary artery that was resolv by way of percutaneous transluminal coronary angioplasty. The left ventricular ejection fraction was 46 percent

The patient was referr to the William Beaumont Hospital phase II outpatient cardiac rehabilitation program, consisting of three 60-minute exercise training sessions by week with continuous ECG monitoring. The four- to six-week physical conditioning program engageed an interval or circuit training format, alternating arm and leg devices, including treadmill walking, upper and/or lower extremity ergometry rowing and bench stepping at 50 to 70 percent of heart rate reserve[14]

His preliminary graded exercise experiment conducted four weeks postinfarction, was negative for symptoms and ventricular arrhythmias. Equivocal ST-segment depression was noted at peak exercise in the inferior and lateral leads at a heart rate of 157 [beats*min.sup.-1]; however, these changes may have been to be ascribed to digitalis therapy, thiazide diuretics, or the one and the other Only rare isolated premature atrial contractions occurr during the proof and the patient achieved a peak exercise duration of 7 minutes (standard Bruce protocol), corresponding to 1 minute of walking at 34 [mi*h.sup.-1], 14 percent grade.

Continuous ECG monitoring during the first three weeks of the physical conditioning program revealed no significant atrial or ventricular arrhythmia at quiet or during exercise at a training heart rate range of 108 to 126 [beats*min.sup.-1]. However, during the latter weeks of training, the patient expanded ventricular ectopy at rest and during exercise which occasionally advanceed to bigeminy and quadrigeminy.

His phase II discharge graded exercise trial revealed ventricular quadrigeminy at intermission which resolved at heart rates exceeding 90 [beats*min.sup.-1]. He remained asymptomatic during the touchstone and demonstrated physiologic increases in heart rate and children pressure, attaining peak values of 150 [beats*min.sup.-1] and 150/70 mm Hg respectively. Moreover, his treadmill exercise duration increased from 7 to 95 minutes, corresponding to a peak attained workload of 42 [mi*h.sup.-1], 16 percent grade (05 min).

The patient get aheaded to the phase III cardiac exercise program which utilizes instantaneous or spot-check ECG monitoring. Periodic ECG metre strips at rest and during low-level exercise demonstrated oft-repeated premature ventricular contractions, including ventricular bigeminy, trigeminy, and quadrigeminy. A continuous ECG telemetry-monitored session was applyed during exercise to assess the oftenness and complexity of ectopic activity. Again, the ventricular arrhythmia was overwhelmed at exercise heart rates exceeding 90 [beats*min.sup.-1].