Exercise ECG Test Research Articles

Epidemiology of ventricular arrhytmias and sudden death

Patients who present with ventricular tachyarrhythmias constitute a diverse group in which a variety of factors may combine to cause ventricular tachycardia or fibrillation. For this reason, we believe that each patient should undergo a comprehensive medical evaluation directed at identifying and treating such factors as ischemia, congestive heart failure, valvular heart disease, sensitivity to cardioactive drugs, and metabolic derangements. Antiarrhythmic treatment is not necessary for many patients with simple VPBs. However, certain patients who have already suffered a life-threatening arrhythmia or who are at high risk for such arrhythmias should be vigorously treated with specific antiarrhythmic therapy. Such therapy must be carefully selected for each individual. The efficacy of any antiarrhythmic treatment should be assessed by ECG monitoring, exercise testing, or electrophysiologic study. In studies reported to date, antiarrhythmic therapy guided by these methods greatly reduced the risk of recurrent arrhythmias. It is too early to assess the impact of these techniques on overall long-term survival in the various patient populations studied.

Computerized exercise ECG in the diagnosis of critical coronary lesions.

Different ECG criteria are evaluated with respect to their ability to identify individuals with critical lesions of the coronary arteries in a population of patients with severe angina. Six chest leads and the the limb leads were recorded in 85 patients by computer during maximal, symptom-limited exercise ECG testing. Averaging of ECG complexes enhances the signal quality and makes it possible to use measurements of the limb leads recorded during exercise. 14 patients with abnormal Q waves in lead V2 were excluded from ST analysis. In the remaining 71 patients, more than 1/3 mm ST depression in lead I and/or more than 2.0 mm ST depression in any of the chest leads had a sensitivity of 85% and a specificity of 67% for lesions in the main stem and/or proximal LAD and/or three-vessel disease. The predictive value of a positive test was 83%. This and other criteria were evaluated for different disease groups and a different stages during the exercise test.

ECG exercise test and selective coronary angiography in patients with coronary artery disease.

ECG exercise test and selective coronary angiography in patients with coronary artery disease.

Clinical Value of Early Exercise Testing After Myocardial Infarction

The clinical utility of predischarge exercise ECGs was assessed prospectively in 47 patients 17 +/- 2 days after myocardial infarction. The graded-interval ergometric exercise protocol was terminated at 450 kilopond-m/min (kpm/min), a heart rate greater than 75% of predicted maximum, or for established clinical indications. Prior to testing, the attending physician and resident indicated their clinical impressions with regard to anticipated (1) angina, (2) exercise capacity, (3) arrhythmias during limited exercise, as well as anticipated discharge medications and activity prescriptions. Ratings were compared to exercise results and consequent alterations in management noted. No complications were noted during the evaluations. Nine patients noted anginal pain during exercise; five were unsuspected by the attending physician or resident. Ten patients demonstrated significant ventricular arrhythmias. Four were receiving antiarrhythmic therapy. Severe limitation of exercise capacity (< 300 kpm/min) was noted in six patients, unanticipated in four. Where not contraindicated, routine use of predischarge exercise ECG testing is recommended.

Exercise ECG Testing

Recently, the limitations of the exercise (stress) ECG test in the diagnosis of coronary artery disease (CAD) have been overemphasized, particularly in the asymptomatic population.^1-3Nevertheless, many physicians who have extensive and clinical investigative experience with the exercise ECG test are fully convinced that the test provides great value in the diagnosis of CAD and in the assessment of functional capacity.^4.5 Some physicians who are skeptical about the value of the exercise ECG test for the screening of presumably healthy individuals are constantly disturbed by the high incidence (35% to 36%) of "false"-positive tests—ST segment responses.^6.7They criticize that a false-positive exercise ECG test frequently leads to psychological trauma (production of "cardiac neurosis") for the individual who has no CAD. It should be emphasized, however, that psychological trauma is usually physician-induced and by no means test-induced. The psychological reaction will largely depend on the physician's approach to a given individual

The relation between the levels of HDL cholesterol and the capacity for removal of triglycerides.

In twenty-two men with "normal" findings clinically, by exercise ECG and laboratory tests, we performed an i.v. fat tolerance test, measurement of LCAT activity and the activities of post-heparin triglyceride lipases, and estimated serum lipids. HDL cholesterol was positively correlated to lipoprotein lipase (r=0.50, p < 0.05) and to the fractional removal rate of exogenous fat (r=0.59, p < 0.01), and negatively to the fasting levels of triglycerides (r=-0.65, p < 0.01). LCAT was neither correlated to HDL cholesterol nor to the fat removal rate. Our reseults confirm that a high triglyceride removal capacity is closely correlated to a high level of HDL. The association between the catabolism of triglyceride-rich lipoproteins and HDL was thus further substantiated.

Reaction to cold of patients with coronary insufficiency.

Twenty six patients with angina pectoris and coronary insufficiency as judged by an exercise ECG test were examined. About half of the patients had more pronounced ECG changes in a cold room at -15 degrees C than at room temperature. They worked less, their subjective rating of exertion during exercise was higher and the heart performed less work, expressed as the heart rate blood pressure product. The other half of the patients was not much influenced by cold. During an exercise test in the supine position almost all patients got more pronounced ECG changes, worked less and the heart performed less work than in the sitting position. It is suggested that cold exposure as well as a supine body position may to a considerable part exert their effect, i.e. lower the anginal threshold and increase ECG changes, by increasing the central blood volume and the diastolic volume of the left heart and thus ceteres paribus the myocardial oxygen consumption.

Cardiovascular impairment and physical working capacity in children with chronic renal failure.

Forty children with chronic renal failure (CRF) on conservative treatment, on hemodialysis, or after renal transplantation and 22 children respresenting a non-uremic control group were subjected to repeated cardiologic examinations by ECG, PCG, chest X-rays and cycle ergometer exercise tests to monitor signs of uremic heart disease and to evaluate physical working capacity (W170). In the CRF group a progressive impairment of W170 was found, starting at an early stage of the disease. Exercise tolerance was inversely related to the degree of CRF. A correlation was also found between W170 and renal anemia. After starting dialysis, W170 failed to increase significantly. Immediately after dialysis an acute drop in W170 occurred. Renal anemia was found to be the main pathogenetic factor of uremic heart disease in children. In some cases hypercirculation following arteriovenous fistulae became equally important as a cause of reduced myocardial performance. Physical rehabilitation, as measured by exercise tolerance tests, was better in transplanted than in dialysed children.

Premature ventricular contractions in normal children

To document the assumed benign prognosis of premature ventricular contractions in children, we followed 17 patients with PVCs and without other heart disease for a mean of seven years (range one to 19 years). Data were collected from the history, physical examination, 15-lead ECG, and treadmill exercise test. Eight of the 17 children still had PVCs at the most recent follow-up. Of these eight children, seven were asymptomatic. The physical examination remained normal in all except one, who developed signs of mitral prolapse. Light exercise abolished the PVCs in all children. We believe that if a careful clinical examination discloses no abnormalities, and if the PVCs are unifocal and disappear with exercise, this dysrhythmia is, in fact, benign in children, and requires no further cardiovascular examination.

Electrocardiographic exercise test in patients with abnormal T waves at rest

The results of submaximal ECG exercise test were evaluated in six leads recorded simultaneously in two groups of patients with T-wave abnormalities in one or more of Leads I, II, and V4-6. Group I included 185 patients with documented ischemic heart disease (IHD) and Group II 28 patients in whom IHD appeared unlikely. The test was positive in 88 per cent of patients in Group I and in 4 per cent of patients in Group II. In the majority of patients in both groups the T wave either did not change or became more positive or less negative after exercise. The pattern of exercise-induced T-wave changes was similar in patients with and without IHD, and was influenced predominantly by the physiologic effects of exercise. T-wave normalization after exercise occurred frequently in patients with and without IHD, and in patients with positive and negative exercise tests. Our results suggest that T-wave abnormalities, not caused by hypertrophy, conduction disturbances, drugs, or electrolyte imbalance, do not modify the results of submaximal ECG stress test, and that behavior of T wave after exercise does not alter the interpretation of the postexercise ECG. The independent behavior of the S-T segment and T wave after exercise in consistent with the theory that the S-T segment and the T wave are generated by different components of the ventricular action potential.

Potassium-43 myocardial perfusion scanning for the noninvasive evaluation of patients with false-positive exercise tests.

Twelve patients with false-positive ECG exercise tests presented with ischemic ECG responses (greater than one mm ST segment depression) during graded maximal treadmill exercise testing in the absence of exercise-induced chest pain or clinical coronary heart disease. Coronary arteriography, left ventriculography and hemodynamic evaluation revealed no significant abnormality in these patients. Transmyocardial lactate analysis during atrial pacing revealed a normal extraction (mean 21%) during pacing stress in five patients. Nine of 12 patients were evaluated with exercise potassium-43 myocardial perfusion imaging whereby the radioactive tracer was administered intravenously during exercise at a time when abnormal ECG changes were present. Myocardial images in these nine patients all showed a normal homogeneous pattern of radioisotope distribution. These results are in direct contrast to findings in patients with coronary heart disease in whom reproducibly demonstrable abnormal regions of decreased potassium-43 accumulation have been noted in myocardial images obtained following injection of the radioactive tracer during exercise. Potassium-43 exercise myocardial perfusion scanning thus appears to be an accurate noninvasive method of assessing patients with suspected false-positive exercise tests and provides a means of increasing the specificity of exercise testing.

The T wave of the electrocardiogram during and after exercise in normal subjects.

In normal subjects the electrocardiographic T wave decreases in amplitude during exercise. Immediately after exercise the T amplitude increases, and there is a rise in the ST segment and in its slope. These changes, which may be due to alterations of sympathetic tone, are relevant to the interpretation of ECG exercise tests.

Digitalis Effects On Exercise Test

<h3>To the Editor.—</h3> In reference to the Question and Answer relating to digitalis effect on the ECG exercise test (<b>217</b>:485, 1971), using a generally accepted criterion of a positive ECG response to exercise, ie, flat or downsloping ST-segment in one or more post-exercise lead, equal to or greater than 1.0 mm in magnitude, normal persons given digitalis often may show "pseudo-positive" exercise ECGs even though the control tracing reveals little or no digitalis effects on the ST-segments. Illustrative cases are reported by Kawai and Hultgren (<i>Amer Heart J</i><b>68</b>:409, 1964). Their article contains other pertinent bibliographic references.

Therapy of Angina Pectoris with Propranolol and Long-Acting Nitrates

A double-blind study of the effects of isosorbide dinitrate, 10 mg given orally four times a day, propranolol, 40 mg four times a day, and the combination of these two drugs was performed on 21 patients with angina pectoris. Each patient received placebo, isosorbide, propranolol, and the combination of the two drugs for 1 month each in a random sequence over 4 months. The number of anginal pains and nitroglycerin tablets used were recorded, and a multistage treadmill ECG exercise test was performed after each treatment period. Frequency of anginal pains was reduced significantly with propranolol (7.0±2.5 pains/week) and the combination of propranolol and isosorbide dinitrate (9.9±2.9) as compared with placebo (21.0±6.4). Similarly, the number of nitroglycerin tablets was reduced with propranolol-containing regimens. Isosorbide was not significantly better than the placebo. Symptomatic improvement with propranolol could be related to a reduction in heart rate, and the product of heart rate and systolic blood pressure during exercise ( P &lt;0.001). The capacity of these patients to perform a multistage exercise test, however, was not improved significantly, and the ischemic ST-segment changes were not altered by the treatments. Thus, propranolol appeared to be effective on the symptoms of angina pectoris, but it did not significantly improve exercise performance, and it did not prevent the ischemic patterns in the exercise ECG in this group of patients. Isosorbide dinitrate, alone or in combination with propranolol, was ineffective in this study.

REDUCING PILLS AND DIGITALIS INTOXICATION

A recent issue of the<i>Archives of Internal Medicine</i>contains a report¹of six patients in whom the ingestion of multicolored reducing pills was associated with the appearance of electrocardiographic changes that led to the misdiagnosis of heart disease. In two cases, abnormal resting ECGs led to the diagnosis of coronary insufficiency. Three patients had spuriously positive exercise ECG tests, and one had first- and second-degree heart block along with severe potassium depletion and muscle weakness. The electrocardiographic patterns in each case had the appearance of digitalis effect. Cessation of the reducing-pill ingestion resulted in complete resolution of the abnormalities in all six patients. The pills were found to contain digitalis and thyroid extract (often combined in the same tablet), diuretic agents, amphetamines, and laxatives. Digitalis and potassium-depleting diuretics may lead to severe digitalis intoxication, while thyroid and the amphetamines have the capacity to excite tachyarrhythmias of the heart. Thus

Anomalous Origin of the Left Coronary Artery from the Pulmonary Artery

Two cases of anomalous origin of the left coronary artery from the pulmonary artery are reported in asymptomatic patients 15 and 27 years of age, bringing to 30 the total number of cases of this anomaly reported in the postinfantile age group. ECG exercise tests demonstrated marked ischemic changes in both patients, but angina or abnormal shortness of breath did not develop in either patient during or after exercise. The anomalous vessel was interrupted by closure of its ostium through a pulmonary arteriotomy during cardiopulmonary bypass, a procedure felt to offer a distinct technical advantage in the surgical treatment of this condition. Following ligation of the anomalous vessel, ECG exercise tests no longer showed definitive evidence of myocardial ischemia. This is interpreted as evidence that ligation should reduce the incidence of exercise-induced sudden deaths in this anomaly.

The effect of digitalis upon the exercise electrocardiogram

1. 1. Electrocardiographic exercise tests (Master's 2-step test) were performed in 15 patients and 16 normal subjects before and after full digitalizing doses of digoxin (Lanoxin). 2. 2. While receiving digoxin, 14 of 15 patients and 8 of 16 normal subjects developed “positive” tests. Five of the 15 patients and all of the normal subjects had “negative” tests when not receiving digoxin. 3. 3. Although the mechanism of the effect of digoxin upon the ECG exercise test remains unknown, no evidence was found to suggest that myocardial ischemia was produced by the drug. An effect upon intramyocardial potassium seems to be most likely. 4. 4. ECG exercise tests should not be carried out in patients who are receiving digitalis preparations. Digitalis should be discontinued for at least 3 weeks before an exercise test is performed. 5. 5. Examination of the Q-T ratio may enable one to differentiate a false-positive test due to digitalis from a true-positive exercise test.

The exercise ECG test. At what intervals to record after exercise?

The exercise ECG test. At what intervals to record after exercise?