Premature ventricular complexes induced by stress testing. Their frequency and response to physical conditioning

Diagnostic usefulness of graded exercise testing in pediatric supraventricular tachycardia

BACKGROUND

Episodic symptoms, often reported during exertion, complicate the assessment of suspected supraventricular tachycardia (SVT).

OBJECTIVE

To examine the diagnostic sensitivity of graded exercise testing in young patients with documented SVT or ventricular preexcitation.

METHODS

A single-centre retrospective review identified 53 patients (5.1 to 17.5 years of age) with structurally normal hearts who had undergone 65 graded treadmill exercise tests in the setting of either documented SVT with normal resting electrocardiograms (n=30) or ventricular preexcitation (n=23). Twenty-five patients (13 pre-excited and 12 nonpreexcited) had exercise-related symptoms. SVT induction during exercise testing was assessed in relation to pre-excitation and the patient's history of exercise-induced symptoms.

RESULTS

SVT was induced during six of the 65 exercise tests performed in three of 53 patients (overall sensitivity 5.7%). All three patients had a history of exercise- induced symptoms, and two had ventricular preexcitation. SVT was induced in 12% of patients with exercise- related symptoms. No other rhythm disturbances occurred during exercise testing.

CONCLUSION

The diagnostic yield of graded exercise testing in patients with suspected SVT is limited, even among those with exercise related symptoms.

Ventricular arrhythmias in healthy young men during physical exhaustion

The occurrence of ventricular arrhythmias was studied in 25 healthy young men, with the aid of ambulatory ECG monitoring, during maximal bicycle tests, short term running, exhausting route marches, and during a 16 h period after brief and long term exercise. The bicycle test allowed prediction of 4 out of the 12 cases (33%) with ventricular premature beats (VPB) during running. The bicycle test combined with ambulatory ECG monitoring over a 16 h period allowed prediction of 12 out of the 14 cases (86%) with VPBs during marching. All 9 subjects who became exhausted during marching had VPBs, whereas 5 out of the 16 who were not exhausted had VPBs (p less than 0.001). In men with VPBs during all three exercise tests, the heart rates at the time of the VPBs were lowest during exhausting route marching. In conclusion, VPBs can be regarded as a physiological phenomenon if they occur only when exhaustion ensues.

Effects of antiarrhythmic agents on left ventricular function during exercise in patients with chronic left ventricular dysfunction

This study was designed to determine the effects of antiarrhythmic agents on global left ventricular (LV) function during exercise in patients with chronic LV dysfunction. Thirty-five patients with LV dysfunction [LV ejection fraction (LVEF) < 45%] and ventricular arrhythmias were studied. They were randomly classified into 3 groups: patients who received a single oral dose of 6 mg/kg disopyramide phosphate (n = 12), those who received a single oral dose of 4 mg/kg mexiletine hydrochloride (n = 12), and those who received a single oral dose of 4 mg/kg pilsicainide hydrochloride (n = 11). First, all patients were subjected to baseline rest and peak exercise, equilibrium-gated cardiac-pool scintigraphy with 99mTc-human serous albumin of 740 MBq (baseline data). Second, on a separate day, they were given drugs once, and were subsequently subjected to rest and peak exercise equilibrium-gated cardiac-pool scintigraphy. Exercise LVEF and peak ejection rate (PER) after administration were significantly lower in the disopyramide and pilsicainide groups than in the mexiletine group (p < 0.05, respectively). The changes in LVEF and PER from rest to peak exercise after administration were significantly less than the baseline changes in those in the disopyramide and pilsicainide groups (p < 0.05, respectively). However, no significant changes in functional parameters were recognized in the mexiletine group. Due care should be taken when disopyramide and pilsicainide are administered to patients with chronic LV dysfunction since they reduce systolic LV function during exercise.

Exercise-induced ventricular arrhythmias in patients with healed myocardial infarction

BACKGROUND

Controversy exists about the clinical and prognostic significance of exercise-induced ventricular arrhythmias late after myocardial infarction. The aim of the study was to identify the main clinical and prognostic features of exercise-induced ventricular arrhythmias in out-patients with healed Q-wave myocardial infarction.

METHODS

The study population was 777 consecutive patients who underwent a symptom-limited (Bruce protocol) treadmill test from May 1988 to January 1991 after myocardial infarction (at least 1 year). Clinical and exercise data were prospectively entered in a computerized database and retrospectively two different groups were selected: (1) 228 patients with exercise-induced ventricular arrhythmias; (2) 549 patients without. Incidence and morphology of exercise-induced ventricular arrhythmias, various exercise parameters and a follow-up were evaluated.

RESULTS

Patients with exercise-induced ventricular arrhythmias were older (P < 0.001), had higher blood pressure (P < 0.03) and peak exercise rate pressure product (P < 0.00) than the others. No difference was found in the incidence of exercise-ischaemia: either symptomatic or not. When simple (< or = 2 Lown) versus complex (> or = 3 Lown) exercise-induced ventricular arrhythmias were considered, the latter were more frequent in patients with anterior myocardial infarction, shorter exercise duration (P < 0.001) and lower exercise rate pressure product, lower ejection fraction and lower incidence of exercise-induced ischaemia. In the follow-up (mean 24 +/- 13 month) there were 24 deaths: five (2.2%) in patients with exercise-induced ventricular arrhythmias and 19 (3.4%) in patients without. Cardiac event rate was similar in both groups.

CONCLUSIONS

We conclude that in out-patients with healed myocardial infarction exercise-induced ventricular arrhythmias are quite frequent, but they are not associated with exercise-induced ischaemia, either symptomatic or not. Exercise-induced ventricular arrhythmias seem to be related to age or peak workload. Moreover patients with these arrhythmias have no adjunctive negative risk on prognosis.

Cardiovascular rehabilitation: status, 1990

Cardiovascular rehabilitation is defined as the process of development and maintenance of a desirable level of physical, social, and psychologic functioning after the onset of a cardiovascular illness. Patient education, counseling, nutritional guidance, and exercise training play prominent roles in the process of rehabilitation. Benefits from cardiac rehabilitation include improved exercise capacity and decreased symptoms of angina pectoris, dyspnea, claudication, and fatigue. Recent pooled data regarding exercise training after myocardial infarction demonstrated a 20 to 25% reduction in mortality and major cardiac events. Exercise training may result in an improvement in systemic oxygen transport, a reduction in the myocardial oxygen requirement for a given amount of external work, and a decrease in the extent of myocardial ischemia during physical activity. The efficacy of modification of risk factors in reducing the progression of coronary artery disease and future morbidity and mortality has been established. Herein we review the history, current practice and results, and future challenges of cardiovascular rehabilitation.

Prevalence and long-term significance of exercise-induced frequent or repetitive ventricular ectopic beats in apparently healthy volunteers

Frequent or repetitive exercise-induced ventricular ectopic beats are often considered a marker for serious cardiac disease or sudden death, or both. However, the prognostic value of these arrhythmias in an unreferred asymptomatic community-dwelling population over a broad age range is unknown. Of 1,160 subjects aged 21 to 96 years who underwent maximal exercise treadmill testing an average of 2.4 times, 80 (6.9%) developed frequent (greater than or equal to 10% of beats in any 1 min) or repetitive (greater than or equal to 3 beats in a row) ventricular ectopic beats on at least one test. These 80 individuals were significantly older than the group without such arrhythmia (63.8 +/- 12.5 versus 50.0 +/- 16.1 years, p less than 0.0001). A striking age-related increase in the prevalence of frequent or repetitive exercise-induced ventricular ectopic beats was seen in men (p less than 0.0001) but not in women. The prevalence of electrocardiographic abnormalities at rest, exercise-induced ST segment depression and thallium perfusion defects, duration of treadmill exercise, maximal heart rate, systolic blood pressure and rate-pressure product did not differ between these 80 study subjects with frequent exercise-induced ventricular ectopic beats and a control group matched for age and gender. Furthermore, the incidence of cardiac events (angina pectoris, nonfatal myocardial infarction, cardiac syncope or cardiac death) (10% versus 12.5%) as well as noncardiac mortality (each 7.5%) was found to be similar for the study and control groups, respectively, over a mean follow-up period of 5.6 years. No study subjects required antiarrhythmic drugs over this time interval.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventricular ectopy in cardiac rehabilitation patients on exercise training and nonexercising days

We evaluated the effect of routine exercise training sessions on the frequency of ventricular ectopic activity (VEA) in 18 coronary artery disease patients (mean age = 60 years) who were active participants in a cardiac rehabilitation program. Nine patients were classified as high risk and nine patients were low risk according to clinical status and cardiac catheterization criteria. Five patients in each group were on beta blockade, but none were on antiarrhythmic agents. Serial 24-h ECG monitoring was obtained on a routine supervised exercise day and nonexercise control day. VEA were compared during three time periods: (1) exercise training and recovery (4 h) and the corresponding 4 h during control, (2) activities of daily living (12 h), and (3) sleep (8 h). Both groups showed a moderate increase in total VEA during the three activity periods from control day to exercise day. However, this increase was only significant (p less than 0.05) in the high-risk group during the 12-h activity of daily living period postexercise. VEA was significantly greater (p less than 0.05) in the high-risk group during all activity intervals except the sleep period on the exercise day. We conclude that VEA occurs with similar frequency during exercise training or corresponding control periods. High-risk patients have significantly greater VEA on exercise and control days and show additional increased in VEA during activities of daily living (eating and driving) on exercise days.

Does ergometric stress test induce a procoagulative condition in patients with previous myocardial infarction?

A regularly scheduled physical training program seems to have antithrombotic effects. Moreover, the hemostatic changes occurring in patients with coronary artery disease during acute exercise have not been clearly elucidated. Since stress testing is routinely performed in clinical cardiology, it would be helpful to assess whether patients with coronary artery disease are exposed to acute coronary thrombosis during or soon after sustained physical exercise. This study was designed to evaluate the effect of acute physical exercise (stress test by bicycle ergometer) on blood coagulation in a group of patients with previous myocardial infarction, and to determine whether the antithrombotic therapy commonly administered favorably influences hemostatic equilibrium. Our results suggest that exercise testing is not harmful to patients with previous myocardial infarction in regard to hemostasis and fibrinolysis and that antithrombotic therapy reduces postexercise increase in platelets.

Electrocardiographic findings in male veteran endurance athletes

Twenty male veteran endurance runners and 20 controls underwent resting, exercise, and ambulatory electrocardiography. Four athletes and three controls satisfied voltage criteria for left ventricular hypertrophy. The PR interval was longer in the athletes and they had longer mean (SD) treadmill exercise times (19 (4) v 16 (2) min) than the controls. Four athletes but no controls had greater than 2 mm downsloping ST segment depression during exercise. During 48 hour ambulatory electrocardiography the athletes had a consistently lower heart rate but maintained a circadian variation. Profound bradycardia (less than 35 beats/min) occurred in eight athletes but only one control. Eight athletes and two controls had asystolic pauses ranging from 1.8 to 15 seconds. Six athletes had first degree heart block, four had Mobitz II second degree block, and three had complete heart block. Most conduction abnormalities occurred at night and resolved during exercise. Ventricular ectopic activity was not significantly different between the groups. Thus heart block patterns and profound bradycardia are more frequent in older athletes than their youthful counterparts.

Can the site of origin of ventricular extrasystoles enhance the localisation of exercise-induced ischaemia?

Previous work from the Departments of Cardiology and Nuclear Medicine, Guy's Hospital, London, has enabled an atlas of the electrocardiographic appearances of ectopics from individual ventricular sites to be compiled. This has been used to investigate the relationship between regions of myocardial ischaemia and the site of origin of exercise-induced ventricular arrhythmias. Two hundred and ten patients underwent maximal exercise testing on a bicycle ergometer, prior to thallium scintigraphy. All 12 leads of the electrocardiogram were recorded simultaneously at rest, immediately post-exercise and then for several minutes afterwards. Thallium scintigraphy was performed immediately and 4 hours post-exercise. Twenty-nine patients of the 210 had ventricular arrhythmias on exercise. Two had dilated (congestive) cardiomyopathy, 1 had hypertrophic cardiomyopathy and 26 were subsequently proven to have ischaemic heart disease. Fifteen of those patients with coronary artery disease and ventricular arrhythmias had otherwise negative exercise tests. Patients with reversible posterior (circumflex) defects had right bundle branch block extrasystoles with a limb lead QRS axis of -60 degrees to -150 degrees. Reversible inferior defects demonstrated ectopic activity with left bundle branch block and a superior axis. Ectopics of septal origin could present with either right or left bundle branch block and an inferior axis from the upper septum, or superior axis from the lower septum. In patients with ischaemic heart disease the 12-lead electrocardiographic appearance of ventricular arrhythmias enables their site of origin to be localised thus suggesting ischaemia in a particular coronary artery territory.

Exercise capacity in the elderly

One of the primary manifestations of ageing is a reduced ability to respond to physiologic challenges. With aging, the ability to perform exercise and physical work declines and is reflected in the reduction in maximal oxygen consumption. Although this decline is influenced to some degree by the state of health and age, it seems that maintenance of regular physical activity significantly counteracts the loss of aerobic capacity. In healthy old age, the cardiovascular system is able to compensate for certain age-associated declines in cardiac function. A program of endurance training, even when begun in old age, can restore more youthful levels of physical fitness and results in tangible improvements in certain resting, submaximal and maximal indicators of exercise capacity. With comprehensive preexercise clinical screening, physical training can be conducted safely with minimal musculoskeletal problems in the aged. The long-term effects of exercise on morbidity, mortality and psychologic function in old age are unknown.

Prevalence and prognosis of exercise-induced nonsustained ventricular tachycardia in apparently healthy volunteers

Although exercise-induced ventricular tachycardia (VT), whether sustained or nonsustained, is usually associated with significant organic heart disease, its prevalence, associated characteristics and prognostic significance in an asymptomatic, unreferred community-dwelling population are unknown. Therefore, the prevalence of VT associated with maximal treadmill exercise was assessed in 597 male and 325 female volunteers, aged 21 to 96 years (mean +/- standard deviation 54 +/- 16), from the Baltimore Longitudinal Study on Aging who were without apparent heart disease. Ten subjects, 7 men and 3 women, with exercise-induced VT were identified, representing 1.1% of those tested; only 1 was younger than 65 years. All episodes of VT were asymptomatic and nonsustained. In 9 of 10 subjects, VT developed at or near peak exercise. The longest run of VT was 6 beats; multiple runs of VT were present in 4 subjects. Two subjects had exercise-induced ST-segment depression, but subsequent exercise thallium scintigraphic results were negative in each. Compared with a group of age- and sex-matched control subjects, those with asymptomatic, nonsustained VT displayed no difference in exercise duration, maximal heart rate, or the prevalence of coronary risk factors or exercise-induced ischemia as measured by electrocardiography and thallium scintigraphy. Over a mean follow-up period of 2 years, no subject has developed symptoms of heart disease or experienced syncope or sudden death. Thus, exercise-induced VT in apparently healthy subjects occurs almost exclusively in the elderly, is limited to short, asymptomatic runs of 3 to 6 beats usually near peak exercise, and does not portend increased cardiovascular morbidity or mortality rates over a 2-year period of observation.

Comparison of noninvasive arrhythmia induction techniques with electrophysiologic studies and evaluation of lorcainide in patients with symptomatic ventricular tachycardia

Twenty-six patients (19 men and 7 women) with symptomatic ventricular tachycardia (VT) were studied using invasive and noninvasive techniques to induce VT. Of the study population, 12% had syncope and VT on Holter monitoring, 30% had cardiac arrest and 58% had symptomatic VT. All patients had antiarrhythmic agents stopped 5 half-lives before evaluation and then had autonomic profile (upright tilt, cold pressor test, exercise testing and hand grip) as well as programmed electrical stimulation studies performed. Autonomic profile testing induced VT in 5 of 26 patients (19%) and in only 1 patient was the arrhythmia reproducibly induced. All 26 patients had VT induced on electrophysiologic testing; 9 patients had nonsustained and 17 had sustained VT. Lorcainide administered intravenously prevented VT induction in 20 of 26 patients tested, whereas procainamide was effective in 11 of 24 patients. Ten of the 13 not protected by procainamide were protected by lorcainide. Twenty patients were started on long-term lorcainide therapy and followed up for 29 +/- 3.4 months. Five patients have discontinued therapy, 2 because of breakthrough arrhythmias, 2 because of severe sleep-wake disturbances and 1 because of private physician preference. An additional 3 patients died during therapy because of myocardial infarction in 1, progressive myopathy in 1 and sudden death in 1. Sixty percent of patients started on lorcainide therapy have continued. In this patient population, noninvasive induction of VT is not a sensitive or reproducible technique in assessing antiarrhythmic therapy. Furthermore, when selected on the basis of electrophysiologic testing, lorcainide is a well-tolerated and effective antiarrhythmic agent.

Safety of maximal exercise testing in patients at high risk for ventricular arrhythmia

While maximal exercise testing is useful for detection of arrhythmias and assessment of antiarrhythmic drug efficacy, few reports have documented the safety of this procedure in patients with malignant ventricular arrhythmias. We reviewed the complications of symptom-limited exercise in 263 patients with such arrhythmias who underwent a total of 1377 maximal treadmill tests. Seventy-four percent of the population studied had a history of ventricular fibrillation or hemodynamically compromising ventricular tachycardia and the remainder had experienced ventricular tachycardia in the setting of either recent myocardial infarction or poor left ventricular function. A complication was defined as the occurrence of arrhythmia during exercise testing--ventricular fibrillation, ventricular tachycardia, or bradycardia--that mandated immediate medical treatment (cardioversion, use of intravenous drugs, or closed-chest compression). Complications were noted in 24 patients (9.1%) during 32 tests (2.3%), whereas 239 patients (90.9%) were free of complication during 1345 tests (97.7%). There were no deaths, myocardial infarctions, or lasting morbid events. Clinical descriptors associated with complications included male sex, presence of coronary artery disease, and a history of exertional arrhythmia (p less than .05). Clinical variables previously considered to confer increased risk during exercise, such as poor left ventricular function, high-grade ventricular arrhythmias (Lown grade 4A or 4B) before or during exercise, exertional hypotension, and ST depression, were not predictive of complications (p greater than .05). Occurrence of a complication was also unaffected by the use of antiarrhythmic drugs at the time of exercise (chi square = 0.19, p greater than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Reproducibility and treatment of exercise-induced ventricular tachycardia

Fourteen patients with exercise-induced ventricular tachycardia (VT) underwent serial treadmill testing, and those with reproducible arrhythmia were treated with a beta-adrenergic blocking agent. In 11 patients (79%), VT of similar rate, morphologic characteristics and duration was reproduced on 2 consecutive treadmill tests performed 1 to 14 days apart. Beta blockade prevented recurrent VT during acute testing in 10 of 11 patients and during chronic therapy in 9. Eight patients had a consistent relation between a critical sinus rate and the onset of VT. In these patients, successful therapy correlated with preventing achievement of the critical sinus rate during maximal exercise. Thus, serial exercise testing is an appropriate means of assessing efficacy of therapy in patients with exercise-induced VT, provided that reproducibility is established on 2 control tests before beginning treatment. Therapy with beta-blocking agents is effective, especially when guided by the presence of a critical sinus rate-VT relation.

Prevalence and nature of cardiac arrhythmias in apparently normal well-trained runners

Sixty well-conditioned runners were evaluated for arrhythmias by Holter monitor during both a distance run and a maximal treadmill test. Twenty-seven percent of subjects had ventricular arrhythmias during treadmill testing, only 3% having grades higher than just an occasional isolated premature ventricular complex (PVC), compared with 60% during the monitored run, of which ventricular bigeminy occurred in 10%, ventricular couplets in 10%, and multiform PVCs in 5%. Treadmill testing significantly underestimated the frequency and grade of both atrial and ventricular arrhythmias: 57% of subjects who had ventricular arrhythmias while running had none on the treadmill, and 11 of 16 who had ventricular arrhythmias on the treadmill had up to 3 grades higher on the run. The discovery of frequent high-grade atrial and ventricular arrhythmias in subjects considered to be completely fit and healthy suggests that such variations in heart rhythm are a normal phenomenon and no more specific for heart disease or risk than ventricular arrhythmias during maximal treadmill exercise testing.

Objective evidence of occult myocardial dysfunction in patients with frequent ventricular ectopy without clinically apparent heart disease

Eighteen asymptomatic persons without apparent cardiac disease were incidentally discovered to have frequent ventricular ectopic activity (VEA) (more than a mean of 100 b/hr during 24-hour ambulatory ECG examination) and were found by cardiac catheterization to have normal coronary arteriograms. Thirteen persons (72%) also demonstrated complex (multiform or repetitive patterns) VEA and eight persons were found to have undiagnosed hypertension. Examination of left ventricular (LV) angiographic and hemodynamic data of these persons showed elevated LV end-systolic volume index in 10 persons (56%), elevated LV and end-diastolic volume index in 12 persons (67%) and elevated LV end-diastolic pressure in 11 persons (61%). Although ejection fractions of all but three persons were normal, impaired myocardial contractility, as measured by decreased mean velocity of circumferential fiber shortening (less than 1.0 circ/sec), was found in 10 persons (56%). Abnormalities of LV function were more prevalent in persons with higher mean frequencies of VEA (more than 300 b/hr), but did not seem related to the presence of complex VEA. Etiologic mechanisms of the frequent and complex VEA could not be defined. We conclude that subclinical evidence of myocardial dysfunction is present in some persons without apparent cardiac disease who have frequent VEA as evidence by subtle abnormalities of increased LV volumes and end-diastolic pressure and decreased mean velocity of myocardial circumferential fiber shortening.

Exercise testing early after myocardial infarction. Risks and benefits

Submaximal exercise testing in the early weeks following myocardial infarction appears to be safe in selected patient groups. Potential benefits of such testing includes: (1) promotion of patient self-confidence, (2) determination of post-hospital exercise prescription, (3) detection of arrhythmias, and (4) determination of post-hospital prognosis. However, the practical value of the apparent psychologic benefits and of the exercise prescription information in a patient not participating in formal exercise rehabilitation therapy is unclear. Detection of potentially important arrhythmias appears to be more adequately effected with 24-hour ambulatory electrocardiography, and detection of such arrhythmias appears to add relatively little prognostic information to that available from exercise electrocardiographic S-T analysis, or from resting radionuclide ejection fraction. Nonetheless, exercise-induced S-T segment depression can provide potentially useful prognostic information regarding morbid or fatal events during the year after infarction. Moreover, recent data suggest that exercise-induced angina and/or S-T segment depression can aid importantly in the noninvasive determination of the anatomic extent of coronary artery disease. The additional benefit or radionuclide cineangiographic determination of left ventricular function during exercise and of thallium 201 scintigraphic determination of myocardial perfusion during stress remain to be defined, although both approaches appear to provide important prognostic information. However, despite the potential benefits of exercise testing, in the absence of clinical trials of available therapy in the "high risk" patient defined by exercise testing, there remains an ill-defined relationship between the information available from exercise testing and the results of management decisions based on this information.

Ambulatory electrocardiographic recording in endurance athletes

Data from ambulatory electrocardiographic recording in 35 highly trained endurance athletes and in 35 non-athletic controls of similar ages are given. The minimal, mean hourly, and maximal heart rates were significantly lower in the athletes. Thirteen athletes (37 . 1%) but only two controls (5 . 7%) had sinus pauses exceeding 2 . 0 seconds. First degree atrioventricular block was observed in 13 athletes (37 . 1%) and five controls (14 . 3%), second degree Wenckebach type block in eight athletes (22 . 9%) and two controls (5 . 7%), and second degree block with Mobitz II-like pattern in three athletes (8 . 6%) and no control. All athletes with Mobitz II-type pattern also had first degree and Wenckebach-type second degree atrioventricular block. The behavior of sinus rate on development of atrioventricular block varied, not only interindividually but also intraindividually, from absence of change to an increase or decrease in most subjects in both study groups. A decrease in sinus rate on appearance of atrioventricular block was found constantly in only two athletes and one control. Atrioventricular dissociation with junctional rhythm occurred in seven athletes (20%) and with ventricular rhythm in one athlete. Neither of these phenomena was seen in the group of controls. The athletes had slightly fewer ventricular extrasystoles than controls, and no athlete had ventricular tachycardia, whereas two controls had ventricular tachycardia.

Exercise-induced ventricular tachycardia

Exercise tests were done on all patients referred to us because of ventricular premature beats. Exercise-associated ventricular tachycardia was seen in three of these patients. Once therapy for the arrhythmia was begun in two patients, we performed serial exercise tests, attempting to provoke the arrhythmia again. In the third patients, who was pregnant, we advised against strenuous physical activity and will exercise her post partum to determine whether therapy is warranted. We have shown that exercise testing can be used successfully in unmasking ventricular arrhythmias not detectable on resting evaluation.

Comparison of ambulatory electrocardiography and exercise testing

Ambulatory electrocardiography and exercise testing are two noninvasive diagnostic procedures widely employed to evaluate patients for cardiac arrhythmias and S-T segment changes. This review addresses the differences and similarities of the two techniques, and examines the relative diagnostic and prognostic merit of the arrhythmia and S-T segment changes detected with each method. Ambulatory electrocardiography is more sensitive than exercise testing in detecting cardiac arrhythmias. The recording of ventricular arrhythmia is of value in predicting sudden death in survivors of myocardial infarction, whereas exercise-induced ventricular arrhythmia has limited predictive value. Nevertheless, exercise-induced S-T depression is of great prognostic value in predicting mortality and sudden death in patients with acute and chronic coronary heart disease.

Exercise-induced ventricular ectopy in children and young adults with complete heart block

Twenty-five children and young adults with complete heart block and 50 normal control subjects were maximally exercised on a treadmill and their electrocardiograms were analyzed for the presence and degree of ventricular ectopy activity. Sixty-eight % (17 of 25) of the heart block patients and significant ventricular ectopy (frequent unifocal ectopy or worse) on exercise compared to 2% (one of 50) of the controls (p = less than 0.01). In the patients with block there was a significant trend toward more frequent and more severe ectopy with increasing age (p = less than 0.05) independent of heart rate. More severe ventricular ectopy was also seen in those patients with QRS prolongation (p = less than 0.05). No significant differences were found between the 14 patients with isolated "congenital" heart block, the seven with associated defects, and the four with surgically acquired block. We believe that severe ventricular ectopy is common at exercise in patients with complete heart block and they may have an increased risk for sudden death.

Exercise-induced ventricular tachycardia. Clinical features, relation to chronic ventricular ectopy, and prognosis

To determine the clinical status, the occurrence of chronic ambulatory arrhythmias, and the prognosis of patients with exercise-induced ventricular tachycardia, 26 patients with ventricular tachycardia during or immediately following exercise on a treadmill were evaluated. Of the 26 patients, 16 had coronary arterial disease, two had nonischemic cardiomyopathy, and eight had no other cardiac disease. Eleven (61 percent) of the 18 patients with heart disease developed ventricular tachycardia during exercise, in contrast to six (75 percent) of eight normal subjects who had ventricular tachycardia after exercise. In eight patients with repeat stress testing, four (50 percent) had reproducible ventricular tachycardia or malignant ventricular ectopic beats. In 19 (73 percent) of 29 patients, malignant ventricular ectopy occurred on random 24-hour electrocardiographic monitoring; ventricular tachycardia occurred in 5/26 (19 percent), and malignant ventricular ectopic beats occurred in 14/26 (54 percent). Fifteen (83 percent) of 18 patients with cardiac disease vs 4 (50 percent) of eight normal subjects (P less than 0.05) evidenced malignant ventricular ectopy during ambulatory monitoring. Only one episode of sudden cardiac death occurred in 24 patients followed for 21 months. Thus, 30 percent (eight) of the patients with exercise-induced ventricular tachycardia had no evidence of heart disease. Furthermore, exercise-provoked ventricular tachycardia presaged sudden death in only one of 24 patients; however, ventricular tachycardia with exercise correctly predicts the presence of chronic advanced ventricular ectopic beats or ventricular tachycardia in 73 percent (19/26) of the patients.

Ventricular arrhythmias during exercise testing, jogging, and sedentary life: a comparative study of healthy physically active men, healthy sedentary men, and men with previous myocardial infarction

The occurrence of ventricular arrhythmias during exercise testing, jogging, and sedentary life with and without preceding exercise was studied with the aid of ambulatory electrocardiographic monitoring in healthy physically active men, healthy sedentary men, and men with previous myocardial infarction (15 men in each group). Ventricular premature beats of the same grade were found during exercise testing and jogging in ten of the 15 healthy physically active men, in ten of the 15 healthy sedentary men, and in eight of the 15 men with previous myocardial infarction. When unifocal ventricular premature beats were omitted, the corresponding figures were 14/15, 11/15, and 15/15, respectively. Healthy physically active men had less ventricular arrhythmias in all of the tested situations. The greatest number and also the highest grades of ventricular arrhythmias during the exercises were found in healthy sedentary men, whereas the men with previous myocardial infarction had ventricular arrhythmias more during sedentary life.

Ventricular premature contractions: a randomized non-drug intervention trial in normal men

The influence of a 6-week intervention on factors thought to be related to ectopic cardiac rhythms was tested in normal men with frequent ventricular premature contractions (VPCs), using a randomized, controlled and partial crossover design. The VPC intervention trial experimental regimen included total abstinence from caffeine and smoking, reduction of alcohol intake, and a physical conditioning program. Effects were studied in detail among 81 healthy men with persistent VPCs. VPCs were measured during standard states of rest, dynamic and isometric exercise and other stresses, and 24-hour ambulatory monitoring. Adherence to the treatment was excellent. The experimental group achieved more than 80% of activities asked of them, and little "contamination" occurred in the control group. VPCs were analyzed according to VPC/min, VPC/man and VPC/total number of heart beats. Moderate changes in VPC rates occurred in both experimental and control groups but no significant group differences were found at rest or during any induction test. This 6-week, multiple-factor "hygienic" intervention program had no significant influence on the frequency or occurrence of VPCs in apparently normal men with persistent and frequent VPCs. Because the mechanisms and the significance of VPCs are different in patients with ischemic heart disease, our approach and methods may be useful for similar trials among cardiac patients of adjunct or non-drug therapy for ectopic rhythms.

Reproducibility of exercise-induced ventricular arrhythmia after myocardial infarction

To evaluate the reproducibility of exercise-induced ventricular arrhythmia, 155 men with a mean age of 53 +/- 8 years underwent serial exercise testing 3 to 52 weeks after myocardial infarction. The reproducibility of categorical test responses, that is, the presence or absence of ventricular arrhythmia, was evaluated with the kappa coefficient, which considers negative as well as possible test responses and expresses reproducibility above the chance level. Reproducibility was highest at an intertest interval of 1 to 5 days and was not enhanced by further categorizing premature ventricular complexes as simple or complex based on their frequency or configuration. Continuous response measures such as frequency of premature ventricular complexes yielded higher reproducibility than categorical responses. Continuous response measures appear preferable to categorical responses for evaluating the clinical significance and response to antiarrhythmic therapy of ventricular arrhythmias.

The electrocardiogram in the assessment of the effect of drugs on cardiac arrhythmias

The search for the ideal antiarrhythmic drug continues since none of the available agents offers optimum antiarrhythmic therapy. The continuing search coupled with the interest in the mechanisms of cardiac arrhythmias has led to the development of new techniques for the study of arrhythmias and antiarrhythmic drugs. In this article it is proposed to discuss the electrocardiographic methods used in the assessment of antiarrhythmic drugs. Firstly, to discuss the electrocardiogram in the assessment of the clinical electrophysiological properties of a drug and secondly, the electrocardiogram in the assessment of the value of the drug in the management of cardiac arrhythmias in man.

Efficacy of propranolol in the control of exercise-induced or augmented ventricular ectopic activity

The effect of propranolol on exercise-induced or augmented ventricular ectopy was studied in sixteen male patients, six of whom had documented coronary artery disease. Fifteen patients were exercised after two weeks of oral therapy, fourteen after single oral therapy and eight patients after intravenous therapy. Propranolol dosage was titrated to produce maximal beta-adrenergic blockade. Effective reduction of exercise-induced ventricular ectopy occurred in ten of fifteen patients (P less than 0.001), and in five of six patients with coronary disease (P less than 0.02). Propranolol therapy abolished ventricular couplets in eight of twelve patients and ventricular tachycardia in four of the patients. Single oral and intravenous therapy had similar or greater effects. Plasma propranolol levels following different routes of administration did not correlate with exercise-induced maximal heart rates or percent reduction in ventricular ectopy. When compared to exercise in eleven patients, ambulatory monitoring underestimated the severity, particularly the highest grades, of ventricular ectopy.

Predictive implications of ventricular premature contractions associated with treadmill stress testing

Follow-up data on future coronary events was collected on 6,500 patients who had undergone stress testing; 1,327 of these exhibited ventricular premature contractions (VPCs) associated with one or more phases of treadmill stress testing (TSTs). Eighty-three percent of all patients tested had known or suspected cardiovascular disease. The annual incidence of new coronary events (myocardial infarction, angina, cardiac death) during a five year follow-up was 1.7% among 1,067 patients without VPCs or ischemic ST changes, 6.4% in 758 patients with VPCs alone, 9.5% among 609 patients with ischemic ST changes alone and 11.4% in 569 patients with VPCs plus ischemic ST changes. The significance of VPCs associated with the TSTs rests largely upon the clinical status of the persons tested. VPCs observed among patients referred for TSTs for the evaluation of known or suspected cardiovascular disease, with or without ischemic ST abnormalities, represent a definite risk factor for future coronary events.