Cardiac arrhythmias observed during maximal treadmill exercise testing in clinically normal men

Blood pressure response is impaired in patients with exercise-induced ventricular ectopy

Exercise-induced ventricular ectopy (EIVE) has clinical and prognostic significance. But the mechanism underlying EIVE-related mortality still remains unclear. This study aims to assess blood pressure alteration in patients with EIVE and to identify the potential causes of increased mortality in this patient group. A total number of 3611 patients were screened within a 1-year period, and patients with a structural heart disease, coronary artery disease, hypertension, diabetes mellitus, thyroid dysfunction, and chronic renal disease were excluded from the study. A total number of 98 patients with no chronic disease, who were retrospectively diagnosed with EIVE, were included in the study as patient group and 116 patients without EIVE were included as control group. The median age, gender distribution, laboratory test results, and echocardiographic findings were similar between the two groups. Systolic blood pressure (SBP) alterations during exercise stress testing were found to be significantly different (P < .001). Moreover, EIVE group had significantly higher peak SBP (P < .001). A significant positive relation was found between peak SBP level and ventricular ectopy count (r:0.27, P = .006). Our study showed that EIVE patients without a structural heart disease or a chronic disease had higher peak SBP levels. Higher SBP alteration can be related to ventricular ectopy occurrence during exercise stress testing, which can be a possible reason underlying the increased rate of mortality among EIVE patients.

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.

Association of ventricular ectopy with nuclear scintigraphic perfusion defects during dipyridamole stress testing

BACKGROUND AND HYPOTHESIS

No information is available regarding the significance of ventricular ectopic activity induced during dipyridamole nuclear scintigraphic stress testing. This study tested the hypothesis that dipyridamole-induced ventricular ectopy predicts a thallium-201 or technetium-99m sestamibi perfusion defect.

METHODS

A group of 186 consecutive patients with premature ventricular contractions and/or couplets occurring during dipyridamole stress testing (ventricular tachycardia did not occur) was compared with a control group of 194 patients without ventricular ectopy during dipyridamole stress testing.

RESULTS

The results indicated that ventricular ectopy induced during dipyridamole infusion occurred more frequently in patients demonstrating either a fixed or reversible perfusion defect on scintigraphic imaging (p < 0.01). The higher frequency of perfusion defects in this group of patients was attributable to a higher frequency of "fixed" compared with "reversible" defects (p < 0.05). This finding is consistent with the additional observation that ventricular ectopy induced by dipyridamole was associated with the presence of Q waves on the resting ECG (p < 0.05). The positive and negative predictive values of the presence of ventricular ectopy in predicting a fixed myocardial perfusion defect were 59 and 54%, respectively.

CONCLUSIONS

Ventricular ectopy induced during dipyridamole infusion suggests the presence of a fixed myocardial perfusion defect.

[Coronary artery disease--relevance of total coronary revascularization on the incidence of malignant arrhythmias]

Myocardial ischemia induces redistribution of different ions (H(+), K(+), Na(+), Ca(++)) across the cardiomyocyte membrane, as well as the loss of intracellular ATP content. This results in changes in the electrical properties including shortening of the action potential, appearance of delayed afterpotentials, and a modified refractoriness of the cardiomyocyte. These changes may induce or support malignant cardiac arrhythmias. Supersensitivity of sympathetic denervated myocardium may further support the electrical instability of ischemic myocardium.Virtues of studies indicate that patients with coronary artery disease who develop complex arrhythmias during or after exercise bear a substantially increased risk for sudden cardiac death. Other studies report about arrhythmic stabilization and reduced mortality if patients with reversible myocardial ischemia receive complete revascularization. However, none of these studies is without methodological flaws. Due to the lack of methodologically sound studies in sufficiently large patient cohorts, the question whether complete coronary revascularisation improves the prognosis of patients with coronary artery disease and which strategy (medical, interventional, or surgical) warrants the best outcomes remains open.

Postoperative arrhythmias in colorectal surgical patients: incidence and clinical correlates

OBJECTIVE

To determine the incidence and clinical correlates of postoperative cardiac arrhythmias in patients undergoing elective large bowel resection.

METHODS

Fifty-one consecutive patients undergoing elective open colorectal resection were recruited for this prospective observational study. Participating patients underwent daily three-lead electrocardiograms postoperatively. Data regarding potential risk factors for arrhythmias were recorded. Post-operative complications were recorded.

RESULTS

Thirteen (26%) patients developed a postoperative arrhythmia, most commonly atrial fibrillation. Significant univariate correlates with postoperative arrhythmias were: age (P<0.01), hypertension (P<0.01), pre-operative serum potassium levels (P<0.01), postoperative pulmonary oedema (P=0.03), postoperative serum potassium (P=0.03) and sodium (P<0.01). Arrhythmia patients were more likely to have other complications (P=0.02). Thirty-one percent of arrhythmia patients had underlying sepsis compared with 18% of controls (P=0.38).

CONCLUSION

Arrhythmias are common following elective large bowel resection. They occur in older patients and are associated with the development of other complications.

Exercise-induced ventricular arrhythmias and cardiovascular death

BACKGROUND

Exercise-induced ventricular arrhythmias (EIVA) are frequently observed during exercise testing. However, the clinical guidelines do not specify their significance and so we examined this issue in our population.

METHODS

A retrospective analysis of prospectively collected data was performed on 5754 consecutive male veterans referred for exercise testing at two university-affiliated Veterans Affairs Medical Centers. Exercise test responses were recorded and cardiovascular mortality was assessed after a mean follow-up of 6 +/- 4 years. EIVA were defined as frequent premature ventricular complexes (PVCs) constituting more than 10% of all ventricular depolarizations during any 30-second ECG recording, or a run of three or more consecutive PVCs during the exercise test or recovery.

RESULTS

EIVA occurred in 426 patients (7.4%). There were 550 (10.6%) cardiovascular deaths during follow-up. Seventy two (17%) patients with EIVA died of cardiovascular causes, whereas 478 (9.0%) of patients without EIVA died of cardiovascular causes (P < 0.001). Patients with EIVA had a higher prevalence of cardiovascular disease, resting PVCs, resting ST depression, and ischemia during exercise than patients without EIVA. In a Cox hazards model adjusted for age, cardiovascular disease, exercise-induced ischemia, ECG abnormalities, exercise capacity and risk factors, EIVA was significantly associated with time to cardiovascular death. The combination of both resting PVCs and EIVA was associated with the highest hazard ratio.

CONCLUSIONS

EIVA are independent predictors of cardiovascular mortality after adjusting for other clinical and exercise test variables; combination with resting PVCs carries the highest risk.

Supervision of occupational fitness assessments

Controversy continues regarding an appropriate level of supervision for occupational fitness assessments. A bout of vigorous physical activity can augment the immediate risk of a cardiac catastrophe by a factor of 5-100 depending on age, cardiac risk factors, and the physical and emotional circumstances of the participant. However, if a person engages regularly in such activity, the immediate risk is more than offset by an improvement in prognosis during intervening periods of rest. During demanding physical work, there is a small but measurable risk of sudden death (3 to 7 episodes per 100,000 personnel per year). The risk associated with a brief (< 15 min) but vigorous occupational fitness assessment is so low as to preclude attempts to reduce it still further by direct medical supervision. If testing encourages an increase in personal fitness, any immediate increase in risk is enormously offset by a reduction in the number of cardiac deaths while resting. Furthermore, evidence is unconvincing that the average medical practitioner can prevent or treat any emergencies that may arise better than a well-trained professional fitness and lifestyle consultant (PFLC), a person certified by the Canadian Society for Exercise Physiology who has had frequent opportunities to practice the necessary skills. Since occupational fitness assessments are not diagnostic procedures, they appear to fall outside the jurisdiction of medical licensing bodies. In the absence of a history of cardiovascular disease, supervision of such assessments is safely and appropriately undertaken by the PFLC. Unnecessary insistence on medical supervision could preclude annual evaluation of occupational fitness and a resulting enhancement of physical condition, thus increasing rather than diminishing the risk to the worker.

Do echocardiographic changes explain the age-associated increase in exercise-induced supraventricular arrhythmias?

Although exercise-induced supraventricular arrhythmias (EISVA) increase with advancing age, it is unclear whether age-associated changes in cardiac structure or function play a major role in this increase. To address this question, we examined the relationship between M-mode echocardiographic variables and EISVA occurring during maximal treadmill exercise in 366 healthy volunteers aged 20 to 90 years from the Baltimore Longitudinal Study of Aging. Simple (i.e., isolated) EISVA were detected in 69 subjects (19%), and complex EISVA (i.e., comprising > 10% of beats in any minute or occurring in runs) in another 29 subjects (8%). Univariate predictors of any EISVA, whether simple or complex, were older age (p < 0.0001), male gender (p < 0.05), greater left atrial size (p < 0.01), left ventricular mass index (p < 0.0001), interventricular septal thickness (p < 0.001), isovolumic relaxation time (p < 0.01), atrial filling fraction (p < 0.01), reduced mitral E-F closure slope (p < 0.001), peak E velocity (p < 0.02), and peak E/A ratio (p < 0.0001). Lesser exercise duration (p < 0.01), lower maximal heart rate (p < 0.0001), and higher peak systolic and diastolic blood pressures (p < 0.001) were also associated with EISVA. However, by multiple logistic regression analysis, age (p < 0.0001) was the only independent predictor of any EISVA. Univariate predictors of complex EISVA were greater age (p < 0.0001), and atrial filling fraction (p < 0.001), diastolic blood pressure (p < 0.05), lesser mitral E-F slope (p < 0.004), exercise duration (p < 0.005) and maximal heart rate (p < 0.01). However, only age (p < 0.0001) independently predicted complex EISVA. Thus, in healthy volunteers undergoing maximal treadmill exercise. EISVA are associated with greater left ventricular wall thickness, reduced early diastolic performance, diminished exercise capacity and elevated exercise blood pressure. However, none of these variables are independent predictors of EISVA over and above the powerful effect of age.

Exercise-induced ventricular tachycardia without demonstrable heart disease in childhood

Exercise-induced ventricular tachycardia (VT) without demonstrable heart disease was studied in pediatric patients. The study population consisted of 17 patients aged 5-14 years (average 9.1 years), who demonstrated reproducible VT during or immediately after exercise testing using a treadmill. The main reasons for the exercise testing were episodes of exercise-related syncope in two patients, exercise-related palpitation in seven and evaluation of sporadic ventricular premature contraction (VPC) in eight. Of the eight patients in the asymptomatic group, two developed sustained VT and the other six had non-sustained VT. Of the nine patients in the symptomatic group, six developed sustained VT. Verapamil produced a good response in seven of 14 patients, and propranolol in six. None of the patients died during the follow-up period, an average of 59.6 months. In four patients, both VT and VPC disappeared, not only on exercise testing, but also on Holter electro-cardiograms, so the anti-arrhythmic agents were discontinued. One patient had syncope and convulsion caused by rapid bidirectional VT in the follow-up period. It was concluded that the prognosis of exercise-induced VT without demonstrable heart disease in children is relatively benign, but careful follow-up is required.

Prevalence and prognostic significance of exercise-induced supraventricular tachycardia in apparently healthy volunteers

The prevalence, characteristics, and prognostic significance of supraventricular tachycardia (SVT) occurring during maximal treadmill exercise testing were examined in 843 male and 540 female asymptomatic volunteers aged 20 to 94 years from the Baltimore Longitudinal Study of Aging who underwent exercise testing a mean of 2.3 times between 1977 and 1991. Exercise-induced SVT occurred during at least 1 test in 51 men (6.0%) and 34 women (6.3%), p = NS for gender. The 85 subjects with exercise-induced SVT were significantly older than the 1,298 free from this arrhythmia (66.0 +/- 13.5 vs 49.7 +/- 18.0 years, respectively, p < 0.001). The prevalence of SVT increased with age in men (p < 0.001) but not in women. Ninety-eight percent of the 141 discrete episodes of exercise-induced SVT were paroxysmal SVT, with heart rates varying from 105 to 290 beats/min (mean 186.3 +/- 43.3); only 16% were > 10 beats in duration and only 4% of subjects were symptomatic. Nearly half (44%) of SVT episodes occurred at peak effort. Coronary risk factors, echocardiographic left atrial size (3.3 +/- 6.7 vs 3.3 +/- 0.6 cm), and the prevalence of exercise-induced ischemic ST-segment depression (11% vs 13%) were similar in 85 subjects with SVT and 170 control subjects matched for age and sex.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

Occupational demand and human rights. Public safety officers and cardiorespiratory fitness

The issue of discrimination in physically demanding employment, such as police, firefighters, prison guards and military personnel, is contentious. In terms of oxygen transport, the 'action limit' (calling for personnel selection or task redesign) is a steady oxygen consumption of 0.7 L/min, while the maximum permissible limit is 2.1 L/min. Note is taken of the commonly expressed belief that public safety duties are physically demanding, calling for personnel with an aerobic power of at least 3 L/min, or 42 to 45 ml/kg/min. The actual demands of such work can be assessed on small samples by physiological measurements (using heart rate or oxygen consumption meters), but the periods sampled may not be typical of a normal day. A Gestalt can also be formed as to the heaviness of a given job, or a detailed task analysis can be performed; most such analyses of public safety work list distance running and other aerobic activities infrequently. An arbitrary requirement of 'above average fitness' is no longer accepted by courts, but a further approach is to examine the characteristics of those currently meeting the demands of public safety jobs satisfactorily. Young men commonly satisfy the 3 L/min standard, but this is not usually the case for women or older men; in the case of female employees, it also seems unreasonable that they should be expected to satisfy the same standards as men, since a lower body mass reduces the energy cost of most of the tasks that they must perform. A second criterion sometimes applied to physically demanding work (a low vulnerability to heart attacks) is examined critically. It is concluded that the chances that a symptom-free public safety officer will develop a heart attack during a critical solo mission are so low that cardiac risk should not be a condition of employment. Arbitrary age- and sex-related employment criteria are plainly discriminatory, since some women and 65-year-old men have higher levels of physical fitness than the average young man of 25 years. Neither laboratory nor field tests offer a satisfactory means of distinguishing such individuals, and the only equitable basis of selecting personnel for physically demanding work seems a probationary period of employment.

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.

Cardiac arrhythmias during exercise in severe chronic obstructive pulmonary disease

We studied the effect of maximal exercise on the prevalence of arrhythmias in 122 subjects with severe COPD. At rest, ten subjects had supraventricular arrhythmias while 13 had unifocal VPB greater than or equal to 6/min or ventricular bigeminy. At peak exercise, six subjects had supraventricular arrhythmias while 24 had VAs. Univariate and multivariate analysis with logistic regression did not show relationships between exercise-related cardiac arrhythmias and the severity of pulmonary disease, oxyhemoglobin desaturation or ECG evidence of chronic lung disease. Exercise-related arrhythmias were significantly associated with the presence of arrhythmias at rest and 87 percent of subjects who had no arrhythmias at rest did not have any during exercise. In patients with COPD, the development of potentially serious arrhythmias during exercise is uncommon without clinically apparent CAD or arrhythmias at rest. However, routine cardiac monitoring during exercise testing should not be abandoned in this population since VAs can occur despite their absence at rest.

Suppression of exercise-induced ventricular arrhythmias by propranolol and diltiazem in a woman without organic heart disease--a case report

A thirty-five-year-old woman without organic heart disease who has exercise-induced ventricular arrhythmias suppressed by propranolol and diltiazem is reported. Treadmill exercise provoked reproducibly nonsustained ventricular tachycardia (NSVT) and salvos of ventricular premature contraction (VPC). QRS morphology of these ventricular arrhythmias showed left bundle branch block pattern and right axis deviation. Oral propranolol (20 mg) and diltiazem (90 mg) prevented exercise provocation of NSVT and VPC. However, oral mexiletine (200 mg) and procainamide (500 mg) could not prevent exercise provocation of these ventricular arrhythmias. No ventricular arrhythmias could be induced by any form of ventricular extrastimulations. Right ventricular pacing at a rate of 210 beats/minute provoked NSVT of which the QRS morphology was similar to that of exercise-induced NSVT. Triggered activity may be a possible electrophysiologic mechanism for exercise-induced ventricular arrhythmias in this patient, although other mechanisms such as reentry and enhanced automaticity could not be completely excluded.

Selective enhancement of the cardiac sympathetic response to exercise by anginal chest pain in humans

Cardiac and whole body [3H]norepinephrine kinetics were used to evaluate the response of overall and cardiac sympathetic activity to supine bicycle exercise in 31 patients with coronary artery disease (CAD) and in nine normal control subjects (group 1). Of the 31 patients with CAD, 20 developed evidence of myocardial ischemia during exercise (group 2), typical angina occurring in 20 of 20 and ischemic ST segment changes in 13 of 20, whereas 11 patients developed no evidence of ischemia (no chest pain or electrocardiographic changes) (group 3). Exercise resulted in increased total and cardiac NE spillover in all groups of patients. Basal cardiac NE spillover was similar in the three groups (group 1, 5 +/- 1 ng/min; group 2, 8 +/- 1 ng/min; group 3, 7 +/- 2 ng/min; p = NS), but during exercise, cardiac NE spillover was greater in patients who developed angina (group 2, 30 +/- 5 ng/min) than in those who did not (group 1, 17 +/- 2 ng/min; group 3, 17 +/- 2 ng/min; p less than 0.05). The increases in total NE spillover were similar in the three groups. Supine bicycle exercise increases cardiac and overall sympathetic tone in normal control subjects and in patients with CAD. The occurrence of angina selectively enhances the cardiac sympathetic response to exercise. In the absence of angina, patients with CAD and control subjects without CAD have similar sympathetic responses to exercise.

Electrophysiological study of young patients with exercise related paroxysms of palpitation: role of atropine and isoprenaline for initiation of supraventricular tachycardia

Electrophysiological studies were performed in eight patients (four men and four women, mean (SD) age 24 (5) years with paroxysmal attacks of palpitation during or immediately after exercise. Five patients were competitive athletes at college. In two patients spontaneous supraventricular tachycardia during exercise was recorded by ambulatory electrocardiographic monitoring and in another it was induced by treadmill exercise testing. Two had dual atrioventricular nodal pathways, three had manifest atrioventricular accessory pathways, and three had concealed atrioventricular pathways. Programmed stimulation induced sustained supraventricular tachycardia in six patients--in two after intravenous injection of atropine sulphate (1 mg) and in four during infusion of isoprenaline (0.01 microgram/kg/min). In one patient, non-sustained atrioventricular nodal reentrant tachycardia was induced during isoprenaline infusion. In the remaining patient, who had dual atrioventricular nodal pathways, tachycardia was not inducible. AH block prevented maintenance of reentry in five patients. In five patients shortening of the effective refractory period of the atrioventricular node with atropine (one patient) and isoprenaline (four patients) caused sustained supraventricular tachycardia. The present study indicates that treatment with atropine and isoprenaline may be an important factor in the initiation of supraventricular tachycardia in patients with exercise related paroxysms of palpitation.

Exercise testing in patients with life-threatening ventricular tachyarrhythmias: results and correlation with clinical and arrhythmia factors

The results of exercise treadmill stress testing were analyzed in 64 consecutive patients presenting with either ventricular fibrillation (42%) or hemodynamically significant ventricular tachycardia (58%). Underlying diseases included coronary artery disease (55%), dilated cardiomyopathy (16%), and miscellaneous disorders (29%). Patients were additionally studied with ambulatory electrocardiographic monitoring and programmed stimulation. During exercise testing, 22 patients (34%) had nonsustained and five (8%) had sustained ventricular tachycardia. No patient experienced ventricular fibrillation or a major complication during exercise testing. Patients with a history of ventricular fibrillation were significantly less likely to have exercise-induced ventricular tachycardia than those with a history of ventricular tachycardia. Other clinical factors were not associated with the results of exercise testing. The results of programmed stimulation did not correlate with the results of exercise testing. Ventricular tachycardia was commonly documented during ambulatory monitoring (72%), but this was not predictive of ventricular tachycardia during exercise. However, patients who did not have ventricular tachycardia during ambulatory monitoring were predictably unlikely to have it during exercise testing (p less than 0.002). Thus exercise testing is safe and can provoke ventricular tachycardia in a significant proportion of patients with life-threatening arrhythmias.

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.

Cardiovascular evaluation of adolescents and young adults. Salient aspects of the examination

Cardiac findings in adolescents and young adults are usually normal, and most murmurs and other abnormalities that are found are benign. However, the primary care physician needs to obtain a complete personal and family history and perform a thorough physical examination to rule out cardiovascular disease and its precursors. Of primary concern are a personal or family history of syncope, family history of sudden death, and several pathologic murmurs such as those caused by mitral valve prolapse and hypertrophic cardiomyopathy. The physician may need to reassure the patient until a definitive diagnosis is made and can also provide accurate information on cardiac disease prevention.

Survivors of cardiac arrest: prevention of recurrence by drug therapy as predicted by electrophysiologic testing or electrocardiographic monitoring

Sixty-two patients (44 men and 18 women, aged 15 to 75 years) resuscitated from at least 1 cardiac arrest unrelated to acute myocardial infarction were studied. No patient was taking antiarrhythmic drugs at the time of the initial cardiac arrest. Thirty-five patients had coronary artery disease (CAD) and 27 did not. Before drug therapy, control electrophysiologic studies induced ventricular tachycardia (VT) in 43 of 58 patients (74%) (30 of 35 with CAD and 17 of 27 without CAD). At control continuous electrocardiographic monitoring for 48 hours or longer, only 19 of 62 patients (31%) had spontaneous VT, 5 of whom had no VT induced at control electrophysiologic study. Mean follow-up was 22 months. Fourteen of 41 patients, 8 of 25 with and 6 of 16 without CAD, had VT suppressed with drugs during serial electrophysiologic testing, and none had a recurrent arrhythmic event. VT was suppressed in 12 of 14 patients receiving conventional drugs. Of 27 patients with VT induced during all drug studies, 6 died from cardiac arrest and 4 had recurrent VT. Drug efficacy in 20 patients was guided by continuous electrocardiographic monitoring, and 4 of 9 patients in whom VT and ventricular pairs were suppressed by drug therapy, as documented by continuous electrocardiographic monitoring for 48 hours or longer, died of cardiac arrest. Overall, 26 patients were discharged receiving amiodarone therapy, and 5 died of cardiac arrest and 3 had recurrent sustained VT.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of exercise testing in predicting sudden death

The exercise test can be utilized to identify a subset of patients with coronary heart disease who are at increased risk of subsequent cardiac mortality including sudden cardiac death. The exercise test variables that best identify these high risk patients differ according to clinical subsets, but exercise duration, ST segment depression and ventricular arrhythmias on the electrocardiogram are the most important variables. In the clinical setting, the exercise test is of limited value for identifying the patient at risk for developing sudden cardiac death because its sensitivity and specificity are not high enough. However, the exercise test does provide prognostic information that is independent of other clinical variables and it may prove to be of clinical utility when combined with multiple other prognostic variables.

Effects of oral prajmaline bitartrate on exercise test responses in patients with coronary artery disease

The safety, tolerability and haemodynamic effects of oral prajmaline bitartrate were assessed in a double-blind, randomized, placebo-controlled, crossover trial in 21 patients with stable angina pectoris and coronary artery disease. No serious side-effects occurred. Prajmaline bitartrate produced no statistically significant changes in resting heart rate or systolic blood pressure or in work capacity on the treadmill, or in heart rate or systolic blood pressure at maximum exercise compared to placebo values. No new arrhythmias or conduction abnormalities were produced in any patient. We conclude that oral prajmaline bitartrate is well tolerated and can be given safely to patients with coronary artery disease without producing deleterious haemodynamic effects or changes in exercise capacity.

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.

Exercise stress testing in the management of cardiac rhythm disorders

Exercise testing is an important tool for exposing symptomatic arrhythmias as well as asymptomatic but potentially serious ventricular tachyarrhythmias. When evaluating the effect of antiarrhythmic drugs, exercise testing is an adjunctive modality.

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.

Prognostic value of ventricular arrhythmias associated with treadmill exercise testing in patients studied with cardiac catheterization for suspected ischemic heart disease

The prognostic information provided by ventricular arrhythmias associated with treadmill exercise testing was evaluated in 1,293 consecutive nonsurgically treated patients undergoing an exercise test within 6 weeks of cardiac catheterization. The 236 patients with simple ventricular arrhythmias (at least one premature ventricular complex, but without paired complexes or ventricular tachycardia) had a higher prevalence of significant coronary artery disease (57 versus 44%), three vessel disease (31 versus 17%) and abnormal left ventricular function (43 versus 24%) than did patients without ventricular arrhythmias. Patients with paired complexes or ventricular tachycardia had an even higher prevalence of significant coronary artery disease (75%), three vessel disease (39%) and abnormal left ventricular function (54%). In the 620 patients with significant coronary artery disease, patients with paired complexes or ventricular tachycardia had a lower 3 year survival rate (75%) than did patients with simple ventricular arrhythmias (83%) and patients with no ventricular arrhythmias (90%). Ventricular arrhythmias were found to add independent prognostic information to the noninvasive evaluation, including history, physical examination, chest roentgenogram, electrocardiogram and other exercise test variables (p = 0.03). Ventricular arrhythmias made no independent contribution once the cardiac catheterization data were known. In patients without significant coronary artery disease, no relation between ventricular arrhythmias and survival was found.

Aggressive management of ventricular arrhythmias. With newer techniques to predict drug efficacy

Although myocardial infarction is perhaps the more dramatic cause of sudden cardiac death, it is cardiac arrhythmias without infarction that account for over half of these deaths. Dr Wells outlines the various means available for monitoring pharmacologic suppression of arrhythmias to provide maximum effectiveness and discusses two other means of control, pacing and surgery.

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.

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.

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.