Exercise and sudden cardiac death

Exercise as a coronary protective factor

Exercise has multiple beneficial actions, both in normal subjects and in patients with coronary artery disease, which can be cardioprotective. Apart from reducing known risk factors and protecting against their deleterious effects, exercise also reduces the risk of coronary artery disease by increasing cardiovascular fitness. The exact contribution of each of these mechanisms in reducing coronary artery disease morbidity and mortality is unclear. Although fitness may be desirable, much of the cardioprotection can be achieved through increased leisure time and recreational physical activity. The risk-benefit ratio is very much in favor of moderate intensity exercise. Even in the absence of a controlled trial, the available evidence suggests that efforts to encourage physical activity are justified.

Sports-related and non-sports-related sudden cardiac death in young adults

Sports-related sudden cardiac deaths were compared with non-sports-related sudden cardiac death in individuals (14 to 40 years old) who were autopsied from 1981 to 1988 at the Maryland Medical Examiner's Office. Thirty-four of 690 total cases of sudden cardiac death were sports-related, which represents 5% of sudden cardiac death in this age group. Causes of death were severe atherosclerosis (nine), hypertrophic cardiomyopathy with asymmetry (eight), coronary artery anomalies (four), idiopathic concentric left ventricular hypertrophy (three), myocarditis (two), arrhythmogenic right ventricle (one), Kawasaki disease (one), and unknown (six); two of the cases with unknown causes had tunnel arteries. Exercise-related deaths were more likely due to hypertrophic cardiomyopathy (p = 0.0007) compared with 102 age-, sex-, and race-matched controls in the non-exercise group; there was no difference in the incidence of severe atherosclerosis (p = 0.4). The mean age of individuals with hypertrophic cardiomyopathy with asymmetry was less than that of those with severe atherosclerosis (24 vs 32 years, p = 0.03). Thus exercise precipitates sudden cardiac death in younger individuals with hypertrophic cardiomyopathy.

The effect of regular physical exercise on sensitivity to ischaemia in the rat's heart

The effect of different training regimes (three programmes of both swimming and running exercise) on the heart hypertrophy index and some biochemical indices was evaluated and compared individually with the sensitivity of the corresponding heart to ischaemia in order to elucidate the significance of training intensity and observed changes in the development of heart ischaemic injury. The sensitivity of the heart to ischaemia, evaluated by the rate of development of ischaemic contracture 48 h after completing the exercise programme, increased in parallel with an increase in the heart hypertrophy index. Experiments with different swimming programmes showed that the extent of cardiac hypertrophy increased together with an increase in the duration of everyday swimming bouts. Hypertrophied hearts from trained rats were characterized by greater mobilization of glycogen and increased incorporation of 32P into ATP when investigated 10 min after isoprenaline administration. During total ischaemia the development of ischaemic contracture was accelerated in catecholamine-stimulated trained hearts due to more rapid hydrolysis of ATP compared with that in the hearts from sedentary animals. It is suggested that the observed difference between hearts from sedentary and trained animals is, at least partially, connected with the higher sensitivity of myofibrils to Ca2+ in trained hearts.

Sudden cardiac death associated with exercise: the risk-benefit issue

Although there is an overall increased risk of sudden cardiac death associated with physical exertion, the risk is small. Yet it warrants consideration by physicians and their adult patients who pursue exercise because, in any individual patient, the risk may be high. To advise patients properly on the risks and benefits of exercise, physicians should have an understanding of the risks of exercise, a strategy for patient evaluation that effectively identifies patients at risk, and a knowledge of appropriate exercise procedures that minimize risk. Patients should also know proper exercise procedures, be aware that there is some degree of risk in exercise, know their exercise tolerance, understand self-monitoring procedures, and be sensitive to prodromal symptoms. The essential feature of prudent exercise is a gradual progression during which an individual remains well within the limits of his/her exercise tolerance.

Ventricular Tachycardia in a Marathoner

In brief Young marathoners who run 60 miles per week may appear to be in great shape. But episodes of palpitations and light-headedness may signify a cardiovascular problem. Tests can reveal just how deceiving appearances can be.

Unstable angina, myocardial infarction and sudden death after an exercise stress test

We performed coronary angiography within 95 minutes of the onset of symptoms in seven patients with an acute coronary event after an exercise stress test. The test was normal in six patients. Previous angiography in four patients revealed no evident or moderate obstructive coronary arterial disease. After the test, unstable angina developed in two patients, acute myocardial infarction in four and ventricular fibrillation in one, who was successfully resuscitated. At acute angiography the coronary artery involved was occluded in four and sub-totally obstructed in three. In three cases, coronary occlusion was due to thrombosis, vasospasm, or both. In six vessels there was an eccentric lesion, which is consistent with a ruptured plaque. These findings show that physical exercise can unexpectedly provoke an acute coronary event with sub-total or total occlusion of a previous angiographically normal or moderately obstructed coronary artery. The mechanism is probably related to exercise-induced plaque rupture which can produce coronary (sub)occlusion by coronary thrombosis, spasm, or both.