Exercise testing for detecting changes in cardiac rhythm and conduction

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.

The prognostic significance of exercise-induced atrial arrhythmias

OBJECTIVES

The purpose of the study was to determine if atrial ectopy (AE) or atrial arrhythmias during exercise are predictive of an increased risk of cardiac events and death.

BACKGROUND

Although stress-induced atrial arrhythmias are common during exercise testing, there is a paucity of data regarding the correlation with underlying heart disease and cardiovascular outcomes. Atrial arrhythmias may reflect underlying left atrial enlargement and diastolic dysfunction, which are prognostic of mortality. We hypothesized that these stress-induced arrhythmias are associated with long-term adverse cardiac events.

METHODS

Exercise echocardiography was performed in 5,375 patients (age 61 +/- 12 years) with known or suspected coronary artery disease. An abnormal result was defined as exercise-induced atrial fibrillation (AF)/atrial flutter, supraventricular tachycardia (SVT), or AE.

RESULTS

A total of 311 (5.8%) patients died (132 [2.5%] from cardiac causes) over a period of 3.1 +/- 1.7 years. In addition, 193 (3.6%) patients experienced a myocardial infarction (MI) and 531 (9.9%) patients required revascularization. During exercise testing, 1,272 (24%) patients developed AE, 185 (3.4%) developed SVT, and 43 (0.8%) developed AF. The five-year cardiac death rate was not statistically different between groups (none [3.8%], AE [4.3%], SVT [3.7%], AF [0%], p = 0.43). The five-year rate of MI was significantly different between groups (none [5.7%], AE [8.3%], SVT [0%], AF [9.0%], p = 0.005). The five-year rate of revascularization between groups was not significantly different (none [14.2%], AE [17.0%], SVT [11.8%], AF [14.8%], p = 0.50). A composite of all five-year adverse end points was similar between groups (none [22.7%], AE [27.8%], SVT [17.7%], AF [25.7%], p = 0.10). In stepwise multivariate analysis, AE was not predictive of myocardial infarction when taking into account traditional clinical variables and exercise test results.

CONCLUSIONS

In this large cohort of patients, the occurrence of AE was predictive of an increased risk of MI. However, the association did not persist after adjustment for clinical and exercise variables known to predict adverse long-term cardiovascular outcomes. The rate of long-term cardiac death or revascularization was not influenced by the development of stress-induced atrial arrhythmias.

[Use of Gated-SPECT with with 99mTC-MIBI in the evaluation of the prognostic significance of ventricular arrhythmias during a stress test]

The presence of ventricular complex cardiac arrhythmias in coronary patients, both at rest or during physical exercise, is considered a risk factor for future coronary events or sudden death during long time follow up. The meaning of ventricular complex arrhythmias (VCA) in patients with normal ventricular function and without myocardium ischemia has still not been explained. This study aimed to evaluate if patients with normal ventricular function and no evidence of cardiac ischemia (determined by means of Gated SPECT) who developed VCA during stress test show an increase in cardiac events on later monitoring.

PATIENTS AND METHODS

All patients were studied by means of an ergometric exercise test using a standard Bruce protocol and Gated SPECT with Methoxyisobutyl Isonitrile-99mTechnetium (99mTC-MIBI). Sixty-seven (67) patients with normal ventricular function and no evidence of cardiac ischemia were included.

RESULTS

13 patients had VCA and 54 had no ventricular arrhythmias during stress test. During the follow up of 681.3 +/- 469 days, none of the 13 patients had sudden death, angina pectoris or myocardium infarction.

CONCLUSIONS

In our sample, the appearance of VCA during stress test in patients without myocardium ischemia and normal ventricular function was not associated with an increase of cardiac events during the monitoring which was carried out.

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)

The mechanisms of exercise provocation of supraventricular tachycardia

Treadmill exercise tests, electrophysiologic studies, and isoproterenol infusions were performed in 14 patients with exercise provocable supraventricular tachycardia to delineate the mechanisms of exercise provocation of paroxysmal supraventricular tachycardia. Treadmill exercise tests reproducibly provoked supraventricular tachycardia in all patients. Supraventricular tachycardia similar to that provoked by exercise occurred spontaneously during isoproterenol infusions in 9 of 11 patients tested. The specific supraventricular tachycardia diagnoses of all patients were atrial reentrant tachycardia (two patients), automatic atrial tachycardia (three), atrial flutter-fibrillation (one), atypical junctional tachycardia (two), and orthodromic atrioventricular (AV) reentrant tachycardia (six) as defined by electrophysiologic studies. Various mechanisms of exercise or isoproterenol induction of supraventricular tachycardia were identified. A critical heart rate and/or appropriate sympathetic state was found to provoke all instances of reentrant or automatic atrial tachycardia and atypical junctional tachycardia. A properly timed atrial premature beat provoked five of six cases of AV reentrant tachycardia and the only case of atrial flutter-fibrillation. The remaining case of AV reentrant tachycardia was induced by a ventricular premature beat. In conclusion, the mechanisms of exercise provocation of reentrant or automatic supraventricular tachycardia are multiple and include a critical sinus rate, increased sympathetic tone, and properly timed atrial or ventricular premature beats.

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.

Exercise-induced distal atrioventricular block

Three patients with 1:1 atrioventricular (AV) conduction at rest developed fixed 2:1 or 3:1 AV block during treadmill exercise testing. Electrophysiologic study documented block distal to the AV node in all three patients, and suggested that the exercise-induced block occurred because of increased atrial rate and abnormal refractoriness of the His-Purkinje conduction system. The findings in these three patients suggest that high grade AV block appearing during exercise reflects conduction disease of the His-Purkinje system rather than of the AV node, even in the absence of bundle branch block. Patients with this diagnosis should be considered for permanent cardiac pacing.

The relationship of carotid sinus stimulation to exercise testing

This review is an attempt to demonstrate the safety and usefulness of the simple maneuver of carotid sinus stimulation with selected subjects undergoing exercise tests. In a variety of circumstances the addition of CSP before or after treadmill walking can yield clinically relevant information relating to arrhythmias, conduction disturbances, symptoms, and pacemakers. Further applications and benefits of these combined procedures remain to be clarified and expanded for judicious application with attention to safeguards.

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.

Clinical significance and characteristics of exercise-induced ventricular tachycardia

Forty-seven patients (0.08%) from a total of 5,730 consecutive patients undergoing treadmill stress tests developed one or more episodes of ventricular tachycardia. Forty patients had heart disease, coronary artery disease being the leading cause. Rest ECG was normal in 12 patients and showed long QTc (greater than 440 msec) in 16 patients. Ventricular tachycardia was brief and self-terminating, requiring D/C cardioversion in only one patient. "Exertional hypotension" preceded ventricular tachycardia in 16 of 34 patients. There was poor correlation (r = 0.16) between the rate of ventricular tachycardia (VT) and the underlying heart rate. Only four episodes of VT were initiated by R on T premature ventricular beats. In summary, exercise-induced ventricular tachycardia 1) is a rare complication of treadmill stress test and occurs in patients with heart disease; 2) is frequently preceded by "exertional hypotension," and 3) is not related to the R on T phenomenon. The high incidence of prolonged QT may indicate a role for the automatic nervous system in its pathogenesis.

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.

Value of treadmill exercise testing in patients with complete bundle branch block

Exercise electrocardiography and selective coronary arteriography was performed in 24 consecutive patients with complete bundle branch block. The criteria for a positive exercise electrocardiogram (E-ECG) were a 1 mm depression or elevation in the J point from the control state, as well as in the ST-segment measured at 0.04 seconds from the J point. Eleven of 12 patients with complete left bundle branch block had a positive E-ECG. Nine of them had normal coronary arteriograms, except one with less than 50% lesions in two arteries. Two patients had severe three-vessel disease. Only one patient had a true negative exercise test. No patient had a false negative test. Nine of 12 patients with complete right bundle branch block had a positive E-ECG. One of these 9 had minimal nonobstructive disease, while the other 8 had severe two- or three-vessel coronary artery disease. Three of the 12 right bundle branch block patients had a negative E-ECG. Two of them had a true negative exercise test, and one a false negative test. Because of a high incidence of probably false positive results, E-ECG appears to be unreliable in detecting coronary artery disease in patients with complete left bundle branch block. But it can provide useful information in the noninvasive evaluation of coronary artery disease in patients with complete right bundle branch block.

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 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.

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.

Exercise testing and portable ECG recording in arrhythmia-prone patients

To detect transient arrhythmias or conduction disturbances, 200 patients with the symptoms of palpitations, syncope or dizziness, and patients with coronary heart disease, angina pectoris, arrhythmias or conduction disturbances on resting 12-lead electrocardiogram, were studied by submaximal treadmill exercise and portable Holter recording. Thirty-nine patients (19.5%) had arrhythmias on the resting 12-lead ECG, 136 patients (68%) showed arrhythmias either on treadmill or Holter recording or both. Eighty-nine patients (44.5%) showed arrhythmias on exercise, while 123 patients (61.5%) had rhythm or conduction disturbances on Holter recording. Twenty-two patients (11%) had arrhythmias only on treadmill walking, while 68 (34%) had arrhythmias only with the Holter. In six patients different arrhythmias was noted by each method. Although the Holter recording technique affords a higher yield of recording transient arrhythmias than did exercise testing, both methods are useful and complementary in evaluating the ambulatory patients suspected of having rhythm or conduction disturbances.