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Biomedical subjects

R F DeBusk

Publications and source records attributed to R F DeBusk.

At least 73 records · Page 4Linked to original sources
PubMed1980

Symptom-limited vs heart-rate-limited exercise testing soon after myocardial infarction.

To develop guidelines for exercise testing soon after uncomplicated myocardial infarction, 93 men completed a heart-rate-limited (HRL) protocol and 107 completed a symptom-limited (SXL) protocol 3 weeks after the acute event. In the HRL protocol, effort terminated at a heart rate of 130 beats/min in the absence of a limiting symptom, exertional hypotension or ventricular tachycardia. Peak heart rate was not an end point in the SXL protocol. Despite a higher peak heart rate and work load in patients who completed the SXL protocol, the prevalence of exercise-induced ischemic ST-segment depression and ventricular ectopic activity was similar in the two groups. No complications occurred with either protocol. Twelve patients (6%) had cardiac events within the next 2 months. Regardless of the test protocol used, early events were more common in patients with ischemic ST-segment responses (15%) than in patients without ischemic responses (3%) (p less than 0.01). In contrast, exercise-induced ventricular arrhythmias were not predictive of early events. Eleven weeks after infarction, when all tests were SXL, the prevalence of exercise-induced ischemic ST-segment depression and premature ventricular complexes was similar to that at 3 weeks. We conclude that SXL and HRL exercise test protocols reveal a similar prevalence of ischemic ST-segment depression and ventricular ectopic activity soon after uncomplicated myocardial infarction.

Angina Pectoris↗
PubMed1980

A new method for evaluating antiarrhythmic drug efficacy.

To develop standards for distinguishing antiarrhythmic drug effect from spontaneous variability of premature ventricular complexes (PVCs), 21 males (mean age 56 +/- 8 years) with chronic ischemic heart disease and PVCs underwent symptom-limited treadmill exercise testing and 24-hour ambulatory monitoring before and after 2 weeks of placebo medication. Linear regression analysis was used to describe the relationship between baseline and placebo PVC frequency for various indexes of ventricular ectopic activity and to establish 95% and 99% one-tailed confidence intervals for this relationship within the group of 21 patients. The lower limit of baseline PVC frequency for which the procedure could distinguish a placebo from a true drug response, termed the "sensitivity threshold," was an average frequency of 2.2 PVCs/hour for ambulatory electrocardiographic monitoring and 1.2 PVCs/min for treadmill exercise testing. All patients exceeded the sensitivity threshold on baseline ambulatory ECGs, but only 38% of patients did so on baseline treadmill exercise tests. To establish antiarrhythmic efficacy with 95% confidence, the minimal percent reduction of PVCs between baseline and placebo visits was 68% for treadmill exercise testing and 65% for ambulatory electrocardiography. Although these standards were developed in patients with chronic ischemic heart disease, the model can be used to establish antiarrhythmic drug efficacy in any patient group.

Ambulatory Care↗
PubMed1980

The work evaluation of the cardiac patient.

Treadmill exercise testing performed three weeks following clinically uncomplicated myocardial infarction was used to assess the occupational work potential of 196 men aged 70 or less. Within the six months after infarction the rate of combined medical and surgical events (sudden death, nonfatal cardiac arrest, myocardial infarction or coronary artery bypass graft surgery) was 34% in the one-quarter of patients judged to be at high risk and 4% in the three-quarters of patients judged to be at low risk on the basis of exercise testing--an eight-fold difference. Seven weeks or more after infarction, treadmill testing or leg-cranking ergometry proved more sensitive than static effort or arm cranking or treadmill exercise combined with static effort in the detection of ischemic and arrhythmic abnormalities. Occupational work assessment may limit costs for postinfarction patients in two ways: (1) by facilitating optimal usage of diagnostic tests and therapeutic interventions in high-risk patients; and (2) by obviating needless delay in the return to work of low-risk patients.

Disability Evaluation↗
PubMed1979

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.

Arrhythmias, Cardiac↗
PubMed1979

The prognostic significance of serial exercise testing after myocardial infarction.

Serial treadmill exercise testing (mean 5.5 tests/patient) was used to evaluate the prognosis of 200 males (mean age 53 years) without clinical heart failure or unstable angina pectoris 3 weeks after acute myocardial infarction (MI). Exercise-induced ischemic ST-segment depression greater than or equal to 0.2 mV 3 weeks after MI was significantly more prevalent in patients with subsequent cardiac arrest (100%) or coronary artery bypass graft surgery (64%) than in patients without subsequent events within 2 years of infarction (35%) (p less than 0.05). Exercise-induced ventricular arrhythmia on multiple tests 5-52 weeks after MI was more prevalent in patients with recurrent myocardial infarction (90%) than in patients without subsequent events (47%) (p less than 0.001). By contrast, exercise-induced ventricular arrhythmia on a single test at 3 weeks was a less powerful predictor of subsequent cardiac events. Exercise-induced ischemia 3 weeks after MI predicted early fatal events, while ventricular arrhythmia on serial testing predicted later nonfatal events.

Adult↗
PubMed1978

Cardiovascular responses to dynamic and static effort soon after myocardial infarction. Application to occupational work assessment.

Static and dynamic work involving the arms and the legs was performed by 40 men seven weeks after myocardial infarction. Leg ergometry produced a significantly higher peak work load, systolic blood pressure (BPs), heart rate (HR), and HR X BPs X 10(-2) product (DP) than did arm ergometry: 842 +/- 178 vs 546 +/- 135 kg-m/min, 176 +/- 24 vs 154 +/- 19 mm Hg and 256 +/- 54 vs 219 +/- 48 (SD). Peak heart rates were 145 and 142. Endpoints were primarily muscular and generalized fatigue and dyspnea. Ischemic abnormalities and ventricular ectopy were more frequent with leg ergometry. Sustained forearm lifting elicited higher HR, PBs and DP responses than sustained handgrip contraction: 95 +/- 16 vs 91 +/- 16 beats/min, 162 +/- 18 vs 152 +/- 17 mm Hg and 154 +/- 33 vs 139 +/- 33 (SD). Ischemic ST segment depression and significant ventricuar arrhythmias were infrequent with static effort. Dynamic leg testing is superior to dynamic or static arm testing in assessing the capacity of patients to perform physical work tasks after myocardial infarction.

Adult↗
PubMed1977

Sudden death during ambulatory monitoring. Clinical and electrocardiographic correlations. Report of a case.

A man with known coronary heart disease underwent treadmill exercise testing to determine his functional capacity. The test was negative for ischemia. Ventricular ectopic activity was noted at rest and in the recovery period. On the same day, while viewing a sporting event at home, the patient died suddenly. An ambulatory electrocardiographic recording documented ventricular fibrillations as the terminal mechanism. Ventricular ectopic activity and heart rate increased in the two hours prior to death, and ischemic ST-segment depression was noted at the time of the terminal arrhythmia. It is postulated that myocardial ischemia and catecholamine response lowered the threshold to ventricular fibrillation, thus facilitating the emergence of the fatal arrhythmia.

Ambulatory Care↗
PubMed1977

Exercise testing soon after myocardial infarction.

Forty-six men under age 70, without clinical congestive heart failure or unstable angina pectoris, performed treadmill tests 3, 5, 7, 9 and 11 weeks after myocardial infarction. Patients were more frequently able to perform moderate exertion (2 mph, 14% grade) at 7 and 11 weeks than at 3 weeks following infarction. Ischemic ST-segment depression, usually unaccompained by angina pectoris, occurred in 45% of patients and was associated with a significantly increased incidence of subsequent coronary events. The presence of exercise-induced ventricular ectopic activity provided little independent prognostic information. No serious complications occurred in 210 tests. Exercise testing soon after myocardial infarction provides objective information concerning the capacity to resume physical activity, including return to work. Two tests, at 3-5 weeks and at 7-11 weeks, appear to provide most of the information contined in five tests performed during this time.

Aged↗