Cardiac dysrhythmias associated with exercise stress testing

Incidence, pathophysiology and prognosis of exercise-induced sustained ventricular tachycardia associated with healed myocardial infarction

Of 150 consecutive patients with sustained monomorphic ventricular tachycardia (VT) (n = 116) or ventricular fibrillation (VF) (n = 34) late after acute myocardial infarction, 17 had reproduction of their sustained monomorphic VT during exercise testing. Data from these patients (group I) were compared with data from patients without exercise-induced VT (group II). No statistical difference was found between groups I and II with relation to age, sex, number of vessels with greater than 70% stenosis, left ventricular ejection fraction, number of previous myocardial infarctions, inducibility during programmed stimulation and total mortality during follow-up. In group I, only 1 patient (6%) developed ST depression during exercise compared with 47 patients (35%) in group II (p less than 0.01). After a 34-month mean follow-up, 6 patients in group I (35%) and 18 patients in group II (13%) died suddenly (p = 0.02). It is concluded that sustained monomorphic VT is reproduced during exercise in only 11% of patients with spontaneous late sustained monomorphic VT or VF. Electrocardiographic findings do not support ischemia as a triggering mechanism of exercise-induced sustained monomorphic VT. Patients with exercise-induced sustained monomorphic VT have a high incidence of sudden death.

Clinical relevance of exercise-induced ventricular arrhythmias in suspected coronary artery disease

Because there is controversy regarding the clinical relevance of exercise-induced ventricular arrhythmias, we analyzed their significance in 383 patients who had undergone both exercise thallium-201 stress-testing and cardiac catheterization. Two-hundred twenty-one patients (58%) had no exercise-induced ventricular arrhythmias while 162 (42%) did. There was no difference between patients with and without exercise-induced ventricular arrhythmias in terms of previous myocardial infarction (p = 0.61), incidence of fixed thallium-201 defects (0.06), number of diseased vessels (p = 0.09) and resting left ventricular ejection fraction (p = 0.06). In contrast, evidence of provocable ischemia (redistribution on thallium-201 and ST-segment depression on the electrocardiogram) were more likely (p less than 0.02) to be seen in patients with exercise-induced ventricular arrhythmias. Discriminant function analysis revealed that these 2 variables best separated patients with and without exercise-induced ventricular arrhythmias. In a 4- to 8-year follow-up, 89 patients had adverse cardiac events. Of these 89, there were 41 deaths, 9 nonfatal myocardial infarctions and 39 coronary revascularization procedures performed later than 3 months after catheterization. Patients with exercise-induced ventricular arrhythmias were more likely (p = 0.01) to have these events than those without these arrhythmias. Moreover, these arrhythmias provided independent prognostic information beyond that provided by the thallium-201 stress test and coronary angiography. We conclude that exercise-induced ventricular arrhythmias are associated with exercise-induced ischemia and provide prognostic information which adds marginally to that provided by other noninvasive and invasive parameters in ambulatory patients being evaluated for chest pain.

Exercise-induced ST depression in the diagnosis of coronary artery disease. A meta-analysis

To evaluate the variability in the reported diagnostic accuracy of the exercise electrocardiogram, we applied meta-analysis to 147 consecutively published reports comparing exercise-induced ST depression with coronary angiography. These reports involved 24,074 patients who underwent both tests. Population characteristics and technical and methodologic factors, including publication year, number of electrocardiographic leads, exercise protocol, use of hyperventilation, definition of an abnormal ST response, exclusion of certain subgroups, and blinding of test interpretation were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity, 68%; range, 23-100%; SD, 16%; and mean specificity, 77%; range, 17-100%; SD, 17%). The four study characteristics found to be significantly and independently related to sensitivity were the treatment of equivocal test results, comparison with a "better" test such as thallium scintigraphy, exclusion of patients on digitalis, and publication year. The four variables found to be significantly and independently related to specificity were the treatment of upsloping ST depressions, the exclusion of subjects with prior infarction or left bundle branch block, and the use of preexercise hyperventilation. Stepwise linear regression explained less than 35% of the variance in sensitivities and specificities reported in the 147 publications. There is wide variability in the reported accuracy of the exercise electrocardiogram. This variability is not explained by information reported in the medical literature.

Ventricular arrhythmias during exercise testing: mechanism, response to coronary bypass surgery and prognostic significance

To investigate the determinants and prognostic significance of ventricular arrhythmias during exercise testing, 86 patients with such arrhythmias were identified from a consecutive series of 446 patients who underwent treadmill exercise testing and cardiac catheterization. The prevalence of these arrhythmias was 19% in the total group but increased to 30% in the 120 patients with 3-vessel or left main coronary artery disease. Patients with exercise-induced arrhythmias were more likely to have 3-vessel or left main coronary artery disease, a lower resting ejection fraction, greater than or equal to 2 mm of ischemic ST depression and more severe segmental wall motion abnormalities than patients without this finding (p less than 0.05). Repeat exercise testing in 22 patients with exercise-induced arrhythmias after coronary bypass surgery revealed that persistence of these arrhythmias was associated with either severe wall motion abnormalities preoperatively or residual ischemic ST depression during the post-operative exercise testing. At a mean follow-up period of 5.3 years, the presence of exercise-induced ventricular arrhythmias was not associated with increased cardiac mortality in the medically treated patients.

Electrophysiologic mechanism of exercise-induced sustained ventricular tachycardia

To elucidate electrophysiologic mechanism of exercise-induced ventricular tachycardia (VT), electrophysiologic studies were performed in 12 patients in whom sustained VT had developed during treadmill exercise testing. Six patients had arteriosclerotic coronary heart disease, 3 had cardiomyopathy, and 3 had no clinical evidence of organic heart disease. All patients had had documented episodes of sustained VT related to exertion and had experienced dizziness, syncope, or both. In addition, 3 patients had had nonfatal cardiac arrest. Electrophysiologic studies provoked paroxysms of sustained VT identical to those observed during treadmill exercise testing in 10 patients and provoked ventricular flutter/fibrillation in 1. Seven patients had VT suggestive of a reentrant mechanism, as the VT could be readily initiated with programmed ventricular extrastimulation or terminated by ventricular overdrive pacing, or both. Three patients had VT suggestive of catecholamine-sensitive automaticity. The VT could not be initiated with programmed electrical stimulation, but it could be provoked by intravenous isoproterenol infusion; furthermore, the VT could not be terminated with ventricular overdrive pacing, but it could be abolished by discontinuing isoproterenol infusion. Reproduction of VT in these 10 patients allowed serial pharmacologic testing in selecting an effective antiarrhythmic regimen. Thus (1) exercise-induced VT can be caused by either reentry or catecholamine-sensitive automaticity, and (2) electrophysiologic studies are of use in defining the underlying mechanism of exercise-induced sustained VT.

The magnitude of exercise-induced ST segment depression and the predictive value of exercise testing

The assess whether the magnitude of exercise induced ST segment depression improves the predictive values of symptom limited exercise tests, and helps in the recognition of patients with more severe coronary heart disease, 90 consecutive patients with positive treadmill tests who also underwent selective coronary arteriography were reviewed. The predictive value improved progressively with the increasing ST depression and was most reliable in a select group of patients with normal electrocardiographic baseline who were not receiving digitalis (73% with ST depression greater than or equal to 1 mm to 100% with ST depression greater than or equal to 4 mm). The incidence of 2 and 3 vessel disease increased from 61% with ST depression greater than or equal to 1 mm in the overall population to 100% with ST depression greater than or equal to 4 mm in the select group, and the incidence of left main trunk lesions increased, respectively from 6 to 30%. The prediction of 2 and 3 vessels disease was found to be significantly greater when patients were dichotomized into those with ST depression greater than or equal to 4 mm compared to less than 4 mm. It is concluded that the magnitude of ST segment depression definitely improves the predictive values of exercise tests as well as the ability to recognize the patients with more severe disease. However, the markedly positive exercise tests cannot be utilized to accurately predict the presence of 2 or 3 vessel disease in individual cases unless ST depression attains 4 mm or more in patients with normal electrocardiographic baseline who are not taking digitalis. In this group, the ability to predict left main trunk lesion is approximately 30%.

The significance of hypotension developing during treadmill exercise testing

The significance of hypotension developing during treadmill exercise testing was evaluated and correlated with the findings at cardiac catheterization in two groups of patients. Twenty-five patients (Group I) had a fall in systolic pressure during exercise and were compared to 50 consecutive unselected patients (Group II) with a normal blood pressure response. Clinical characteristics were similar in both groups. Females comprised 48 per cent of the patients in Group I and only 30 per cent in Group II. The incidence of significant coronary artery disease was not different when the two groups were compared as a whole, 56 per cent in Group I and 36 per cent in Group II (P = NS). When males and females were considered separately, it was noted that the incidence of coronary artery disease was higher in hypotensive males (77 per cent) when compared to control males (40 per cent) (p less than 0.01). Females in both groups had a lower but comparable incidence of coronary artery disease (25 per cent and 27 per cent, respectively). Resting hemodynamics and angiographic characteristics, such as contraction abnormalities, and the number and distribution of diseased coronary vessels, were similar in both groups of patients. These findings suggest that hypotension in females does not necessarily connote coronary artery disease. Males with hypotension have a higher incidence of coronary artery disease, but the extent and distribution of their disease is no different from that of patients with a normal blood pressure response to exercise.

Ventricular arrhythmia 24 hours before and after maximal treadmill testing

To determine if maximal exercise treadmill testing influences the occurence of ventricular arrhythmia in the hours after exercise, 45 myocardial infarction and 22 angina pectoris patients (New York Heart Association Class I-II), and 23 normal subjects were examined with 24-hour ambulatory electrocardiographic Holter recordings before and after exercise testing. Comparison of qualitative and quantitative ventricular arrhythmia detected during identical chronological two-, four-, and 20- or more hour periods, before and after exercise testing in each patient, revealed no statistically significant difference in any patient group. The prevalence of ventricular ectopy in 80 per cent of ischemic heart disease patients and 30 per cent of normal subjects as detected by 24-hour Holter recordings was similar to previous studies. It is concluded that in ambulatory ischemic heart disease patients (New York Heart Association Class I-II) and normal subjects, maximal treadmill testing does not significantly affect the occurrence of ventricular arrhythmia in the hours after exercise.

Submaximal treadmill exercise testing of patients with coronary artery disease

The submaximal treadmill exercise test is a valuable noninvasive tool for the diagnosis of overt or latent coronary artery disease (CAD). When submaximal heart rates of 80% to 90% of the predicted maximal rates are attained and when ST-segment depression of at least 1 mm is taken as a criterion of ischemia, testing by any of the various exercise protocols with continuous ECG monitoring affords reasonable specificity and sensitivity. The objectives of testing are to (1) diagnose and determine the severity of CAD, (2) assess functional capacity, (3) observe the natural history of disease, (4) evaluate the effects of medical and surgical treatment, and (5) evaluate responses to physical conditioning or to programs directed toward prevention of CAD. Proper precautions and safety standards minimize the risk of exercise testing.

Prevalence and reproducibility of exercise-induced ventricular arrhythmias during maximal exercise testing in normal men

The occurrence of ventricular arrhythmias at rest or during ordinary daily activities has been implicated as a risk factor for future coronary-related events and sudden death. However, the clerical significance of exercise-induced ventricular arrhythmias remains uncertain. To assess the prevalence and reproducibility of such arrhythmias, two serial maximal treadmill exercise tests were performed in a study population of 543 male Indian State policemen at an average interval of 2.9 years. Four hundred sixty-two subjects were clinically free of evidence of cardiovascular disease, and 81 had evidence of definite or suspected cardiovascular disease. The prevalence of exercise-induced ventricular arrhythmias during the first test was 30% in men aged 25 to 34 years, 32% in those aged 35 to 44 years and 36% in those aged 45 to 54 years. The prevalence rate in these age groups with repeat testing was 36, 38 and 42%, respectively. These differences were not statistically significant. The group with definite or suspected cardiovascular disease had a greater prevalence of exercise-induced ventricular arrhythmias than normal subjects during both tests but the prevalence rate with repeat testing remained constant. The occurrence of exercise-induced ventricular arrhythmias was reproducible in individual subjects during the second test in 55% of 25 to 34 year olds, 58% of 35 to 44 year olds and 62% of 45 to 54 year olds. Thus, individual reproducibility in two consecutive tests was only slightly greater than reproducibility by chance alone. The group with known or suspected cardiovascular disease demonstrated a trend toward greater reproducibility with repeat testing. Exercise-induced ventricular arrhythmias were not reproducible by type or complexity. The marked variability of exercise-induced ventricular arrhythmias during repeat maximal exercise testing in a clinically normal population appears to negate the usefulness of this finding during a single test as a marker of future cardiovascular disease. Nevertheless, subjects whose arrhythmias were reproducible may form a group destined to manifest clinical cardiovascular disease in long-term follow-up studies.

Comparative study of exercise-induced ventricular arrhythmias in normal subjects and patients with documented coronary artery disease

The incidence, types and patterns of emergence of treadmill exercise induced ventricular arrhythmias were studied in 482 subjects with and without coronary heart disease. All subjects were free of premature ventricular complexes at rest and were classified into groups on the basis of their clinical status. In Group 1A were 141 patients with chest pain and normal coronary arteriograms and in Group IB 144 age-matched subjects free of clinical evidence of heart disease. Group II consisted of 197 patients with chest pain and arteriographically documented coronary artery disease. Patients in Group IA and II exercised to at least 85% of their predicted maximal heart rate or until chest pain occurred. Subjects in Group IB underwent maximal exercise testing. The total incidence of exercise-induced ventricular arrhythmias was 16% in Group IA, 44% in Group IB and 29% in Group II. However, when exercise heart rate at the time of appearance of ventricular arrhythmias was taken into account the incidence of exercise-induced ventricular arrhythmias up to a heart rate of 130/min was 27% in the patients with documented coronary artery disease (Group II) compared with rates of 9 and 6%, respectively, for Groups IA and IB (P less than 0.001). The incidence rates of multifocal ventricular premature complexes, ventricular tachycardia and ventricular premature complexes at a rate of more than 10/min were also significantly greater at submaximal heart rates in the patients with coronary disease. Patients with three vessel coronary artery disease and abnormal left ventricular wall motion had a significantly greater incidence of exercise-induced ventricular arrhythmias. The incidence of exercise-induced ventricular arrhythmias in patients with coronary disease and a positive S-T segment response was not significantly increased.

Multiple lead ECG submaximal treadmill exercise tests in angiographically documented coronary heart disease

One hundred patients underwent submaximal exercise tolerance testing and coronary cineangiography. Sixty-six percent of the exercise tests were diagnostic including 48 positive and 18 negative tests; 34 patients had indeterminate test results. The occurrence of exercise induced ventricular premature beats was not related to significant coronary artery disease. Ventricular asynergy was significantly more frequent in patients with positive exercise tests (p less than .0001). Application of the age-adjusted target heart rate criterion recommended from Scandinavia and Myrtle Beach to patients with indeterminate results due to failure to reach target heart rate resulted in six false negative tests and lowered sensitivity. The number of positive diagnostic responses achieved using a multiple electrocardiographic lead system was compared with positive diagnostic responses detected in a single lead (V5) and the number of positive tests identified by the additional leads was highly significant (p less than .0001). A high incidence of indeterminate test results due to failure to achieve target heart rate is noted.

Treadmill arrhythmias in patients with idiopathic hypertrophic subaortic stenosis

Treadmill tests were performed in 19 patients with previously documented idiopathic hypertrophic subaortic stenosis (IHSS). Arrhythmias occurred in 79 percent (15) of the patients, and new arrhythmias not previously documented occurred in over 50 percent (10) of the patients. Paroxysmal supraventricular tachycardia (PSVT), ventricular premature beats (VPBs) (two or more per minute) or atrial premature beats (APBs) (three or more per minute) occurred in 10 of 19 patients. There was no association between treadmill arrhythmias and clinical symptoms, hemodynamic data, or electrocardiographic features. Propranolol administration resulted in failure of exercise to induce PSVT in one patient and had no effect on PSVT in two others, nor any effect on maximum frequency of APBs or VPBs. Treadmill testing is more productive than retrospective analysis of ECGs for characterizing arrhythmias in IHSS.

Myocardial ischemic effects of isometric, dynamic and combined exercise in coronary artery disease

The electrocardiographic effects isometric (handgrip) and combined isometric-dynamic (treadmill-plus-brief-case) exercise were evaluated and compared to a submaximal treadmill stress test in 140 patients with known or suspected coronary artery disease. Only 3 of 90 patients developed ischemic ST changes during handgrip, as opposed to 25 positive treadmill tests (p less than 0.01). Of 19 of 50 patients who were positive during the standard treadmill test, only 17 showed positive findings during the combined treadmill-briefcase test. Analysis of hemodynamic responses showed significant (p less than 0.01) differences between the handgrip and treadmill tests in terms of heart rate response (control 83 plus or minus beats/minute, handgrip 105 plus or minus 4, treadmill 151 plus or minus 6), diastolic blood pressure (control 80 plus or minus 2 mm Hg, isometric 93 plus or minus 3, treadmill 81 plus or minus 3) and heart rate-systolic pressure product (control 9940 plus or minus 564 units, handgrip 15022 plus or minus 779, treadmill 22270 plus or minus 1147). In comparing treadmill and combined treadmill-briefcase tests, significant differences were seen in systolic blood pressure (control 114 plus or minus 2 mm Hg, treadmill 143 plus or minus 3, briefcase 155 plus or minus 3), diastolic blood pressure (control 83 plus or minus 2 mm Hg, treadmill 82 plus or minus 2, briefcase 89 plus or minus 2) and rate-pressure product (control 10134 plus or minus 373, treadmill 19624 plus or minus 777, briefcase 21201 plus or minus 798). Isometric exercise alone is much less likely to produce myocardial ischemia than vigorous dynamic exercise. Higher arterial diastolic (coronary perfusion) pressure may retard the development of myocardial ischemia during isometric or combined isometricdynamic exercise in coronary patients.

Idioventricular tachycardia with angina pectoris

Idioventricular tachycardia (IVT) occurred in a patient with angina pectoris on three separate occasions associated with stress induced angina. It occurred immediately after a Master's test, a treadmill exercise test, and following an episode of paroxysmal atrial tachycardia which was precipitated by endocardial pacing. His bundle electrograms demonstrated that the rhythm was ventricular in origin. Cardiac catheterization documented the presence of severe coronary artery disease. Idioventricular tachycardia is often seen with acute myocardial infarction. It is rarely seen with angina or with exercise testing. To our knowledge this is the first reported case of IVT which could be repeatedly produced by stress induced angina.

Maximum treadmill exercise electrocardiography in female patients

Exercise testing has become standardized for the diagnostic and functional evaluation of male patients but little data is available regarding its specificity and sensitivity in the female. Therefore, maximum treadmill exercise (Bruce protocol) was performed on 98 consecutive females and compared to coronary arteriography. Using 50% obstruction as indicating coronary artery disease and 1 mm ST-segment depression (horizontal or downsloping) as positive for ischemia, 24 patients had coronary artery disease with seven false-negative results (sensitivity = 71%) and 74 patients had no coronary artery disease with 16 false-positive responses (specificity = 78%).

Five of seven false-negative tests were in patients with single-vessel disease. Eleven of 16 false-positive responses were in patients on digitalis, diazepam, or methyldopa. In 39 patients on no drug therapy except for nitroglycerin there were no false negatives and only four false-positive tests. There were no false negatives and only two false-positive tests in 34 patients with normal resting electrocardiograms. Only one of 18 patients with both normal resting electrocardiograms and on no drug therapy had a false-positive test result. Eleven false-positive and seven false-negative results occurred in 40 patients with both an abnormal resting electrocardiogram and associated drug therapy.

The exercise electrocardiographic response in female patients is similar to the male when patients with resting electrocardiographic abnormalities and concomitant drug therapy are eliminated.