Comparison of treadmill exercise testing and psychologic stress testing soon after myocardial infarction.

Are physical or psychologic stressors more useful for evaluating psychologic stress in patients with coronary heart disease? To evaluate this question, patients underwent physical and psychologic testing 7 weeks after myocardial infarction. The psychologic stress test consisted of an open-ended interview, a videotape depicting stressful scenes and a puzzle task. In 20 men whose mean age ± standard deviation was 52 ± 1 years, the interview produced the following peak heart rate and systolic blood pressure responses: 83 ± 18 beats/min and 140 ± 13 mm Hg, which were 8 and 10 percent, respectively, above values at rest (P < 0.05). Symptom-limited treadmill exercise testing in 10 of these patients elicited maximal heart rate and systolic blood pressure values of 152 ± 24 beats/min and 172 ± 32 mm Hg, respectively; ischemic S-T segment depression or angina pectoris occurred in 6 of the 10 patients, whereas none had demonstrated ischemia with psychologic testing. A second consecutive series of 20 patients demonstrated cardiovascular responses to physical and psychologic stress similar to those of the first series. Again, ischemic abnormalities were absent during psychologic stress, whereas exercise-induced ischemic abnormalities were noted in 3 of 20 patients. Ischemic abnormalities are unlikely to appear during psychologic stress testing in patients with a high heart rate and systolic blood pressure threshold for ischemic abnormalities during exercise testing. Standard methods of physical exercise testing are superior to currently available psychologic stress tests for evaluating the cardiovascular response to most commonly encountered psychologic stressors.     

Stepwise risk stratification soon after acute myocardial infarction

A stepwise rise stratification procedure sequentially combining historical and clinical characteristics and treadmill exercise test results was applied to 702 consecutive men aged ≤70 years who were alive 21 days after acute myocardial infarction (Ml). Historical characteristics alone (prior Ml and prior angina or recurrence of pain in the coronary care unit) identified 10% of patients with the highest rate of reinfarction and death within 6 months (18%). Clinical contraindications to exercise testing identified another 40% of patients with an intermediate rate of cardiac events (6.4%). In the 50% of patients who underwent treadmill testing 3 weeks after Ml, the rate of cardiac events within 6 months was 4.4%: 3.9% in patients with a negative test and 9.7% in patients with a positive test (ischemic ST-segment depression ≥0.2 mV and a peak heart rate ≤135 beats/min). Patients with negative treadmill tests, who comprised 46% of patients ≤70 years and 53% of patients ≤60 years, had a cardiac death rate of <2% in the 6 months after Ml. The stepwise classification procedure correctly classified 72% of patients with hard medical events within 6 months. Thus, most patients who experience subsequent cardiac events are correctly classified on the basis of historical and clinical risk characteristics. In patients without these risk characteristics, early treadmill testing is useful for further discriminating high-risk from very low risk patients.     

Exercise training soon after myocardial infarction

To assess the cardiovascular effects of exercise training soon after clinically uncomplicated myocardial infarction, 70 men (mean age 54 years) underwent gymnasium training (no. = 28), home training (no. = 12) or no training (no. = 30) 3 to 11 weeks after the acute event. During this 8 week interval functional capacity increased significantly (P < 0.001) in all three groups: gymnasium training, 66 percent; home training, 41 percent; and no training, 34 percent. Peak functional capacity at 11 weeks was 11.0 ± 1.6, 10.3 ± 1.4 and 9.4 ± 1.8 (mean ± standard deviation) multiples of resting energy expenditure (METs) in the three groups—values approximating those of sedentary men of similar age without coronary heart disease. Functional capacity increased more in the gymnasium training group than in the no training group, but this difference was statistically significant only in patients without exercise-induced ischemie S-T segment depression or angina pectoris (P < 0.01). Another “training effect”—diminished heart rate response to submaximal work—was also observed in all three groups. It is concluded that (1) symptom-limited treadmill exercise testing performed soon after clinically uncomplicated myocardial infarction is feasible and safe and provides useful guidelines for physical reconditioning. (2) Patients who demonstrate nonischemic responses to treadmill exercise testing soon after infarction may safely undergo unsupervised exercise training at home. (3) Formal exercise training may not be required to restore functional capacity to nearly normal values soon after clinically uncomplicated myocardial infarction.     

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.     

Effects of early postmyocardial infarction exercise testing on self-perception and subsequent physical activity

The effects of exercise testing 3 weeks after clinically uncomplicated myocardial infarction (MI) on subsequent physical activity were evaluated in 40 consecutive men with a mean age of 52 +/- 9 years. Patients' confidence in their ability to perform various physical activities was evaluated with self-efficacy scales which patients completed before and after a symptom-limited treadmill exercise test. Increases in confidence (self-efficacy) for activities similar to treadmill exercise (walking, stair climbing, and running) were greatest after treadmill exercise, whereas increases for dissimilar activities (sexual intercourse and lifting) were greatest after test results were explained by a physician and nurse. The intensity and duration of subsequent physical activity at home were more highly correlated with self-efficacy after treadmill exercise than with peak treadmill heart rate. Of the 8 patients whose treadmill tests were limited by angina pectoris, 7 had self-efficacy scores which remained low after treadmill testing or which decreased from initially high values after treadmill testing. These patients had lower peak heart rates and work loads than patients whose self-efficacy increased or remained high after treadmill testing. After MI, patients' perception of their capacity for physical activity and their actual patterns of subsequent physical activity are influenced by early treadmill testing in a manner which is congruent with these patients' treadmill performance.     

Mechanisms for decreased exercise capacity after bed rest in normal middle-aged men

The mechanisms responsible for the decrease in exercise capacity after bed rest were assessed in 12 apparently healthy men aged 50 +/- 4 years who underwent equilibrium gated blood pool scintigraphy during supine and upright multistage bicycle ergometry before and after 10 days of bed rest. After bed rest, echocardiographically measured supine resting left ventricular end-diastolic volume decreased by 16% (p less than 0.05). Peak oxygen uptake during supine effort after bed rest was diminished by 6% (p = not significant [NS]), whereas peak oxygen uptake during upright effort declined by 15% (p less than 0.05). After bed rest, increases in heart rate were also greater during exercise in the upright than in the supine position (p less than 0.05). Values of left ventricular ejection fraction increased normally during both supine and upright effort after bed rest and were higher than corresponding values before bed rest (p less than 0.05). After bed rest, increased left ventricular ejection fraction and heart rate largely compensated for the reduced cardiac volume during supine effort, but these mechanisms were insufficient to maintain oxygen transport capacity at levels during upright effort before bed rest. These results indicate that orthostatically induced cardiac underfilling, not physical deconditioning or left ventricular dysfunction, is the major cause of reduced effort tolerance after 10 days of bed rest in normal middle-aged men.     

Antiarrhythmic efficacy of encainide and quinidine: Validation of a model for drug assessment

The antiarrhythmic efficacy of encainide and quinidine was compared in 20 ambulatory men (mean age 56 ± 8 years) with a history of premature ventricular complexes. All but one patient had a history of chronic ischemic heart disease. A longitúdinal crossover design was used to study the effects of encainide and quinidine on premature ventricular complexes recorded on treadmill excercise tests and on 24 hour ambulatory electrocardiograms. After a baseline evaluation, patients were randomized to one of two drug sequences consisting of 2 weeks of treatment with placebo followed by 2 weeks of treatment with the first drug, after which the same sequence was repeated for the second drug. Encainide was generally better tolerated than quinidine. The reduction in the average number of premature ventricular complexes/hour on ambulatory electrocardiograms and in the average number of premature ventricular complexes/min on treadmill exercise tests was greater With encainide than with quinidine (p <0.01 and <0.025, respectively). Encainide suppressed all premature ventricular complexes recorded on ambulatory electrocardiograms in 44 percent of patients, reduced them by at least 80 percent in 88 percent of patients and suppressed complex forms in 100 percent of patients. By contrast, no patient demonstrated total suppression of premature ventricular complexes with quinidine, only 44 percent demonstrated at least 80 percent reduction and only 53 percent demonstrated suppression of complex forms on 24 hour ambulatory electrocardiograms. Encainide Is safe and effective for the treatment of chronic ventricular ectopic activity. In this study, It appeared to be superior to average doses of quinidine.     

Factors influencing estimated oxygen uptake during exercise testing soon after myocardial infarction

To determine the extent to which oxygen uptake (VO₂) estimated from exercise testing in healthy adults is applicable to patients tested soon after myocardial infarction, v?O₂ was measured during symptom-limited treadmill testing 3 and 11 weeks after the acute event. Twenty-two men (Group I) underwent treadmill testing using a “standard” modified Balke protocol (3 miles/h [80 m/min] with 2.5 percent increments in grade every 3 minutes) 3 and 11 weeks after infarction. Twenty-five clinically similar men (Group II) underwent treadmill testing using a standard protocol at 3 weeks but an “accelerated” protocol (3 miles/h with 5 percent increments in grade every 3 minutes) at 11 weeks. Measured and estimated values of peak v?O₂ were nearly identical for both groups of patients performing the standard protocol at 3 weeks (mean ± standard deviation 20.5 ± 4.7 versus 20.4 ± 6.1 and 22.1 ± 4.1 versus 22.5 ± 4.5 ml/kg per min for Groups I and II, respectively). Measured and estimated values of peak v?O₂ were also similar for patients completing the standard protocol at 11 weeks (26.3 ± 7.6 versus 26.7 ± 6.9 ml/kg per min). In contrast, estimated values of peak v?O₂ were significantly higher than measured values in patients completing the accelerated protocol at 11 weeks (30.8 ± 4.3 versus 27.7 ± 5.0 ml/kg per min (probability [p] = 0.001). Holding onto the treadmill handrails significantly increased estimated peak v?O₂ (32.7 to 37.9 ml/kg per min) but did not affect measured peak v?O₂ (32.1 to 31.8 ml/kg per min). These results indicate that v?O₂ for patients performing treadmill exercise testing after myocardial infarction can be estimated from data derived from healthy adults so long as the exercise intensity is increased slowly and holding onto the handrails is avoided.     

Improvement in ventricular function during exercise studied with radionuclide ventriculography after cardiac rehabilitation

A heterogeneous group of 19 consecutive patients with coronary artery disease were studied with radionuclide ventriculography before and after a mean of 6 months of exercise training. Ejection fraction was measured at rest, at matched submaximal supine work loads and during maximal supine bicycle exercise. After training there was no change in mean ejection fraction at rest or during maximal exercise, but a higher maximal mean systolic blood pressure, heart rate and work load were achieved. At equivalent submaximal work loads after training, similar levels of mean heart rate and systolic blood pressure were reached but a statistically greater mean ejection fraction was obtained. These preliminary results suggest that exercise training may improve cardiac function during exercise in selected patients with coronary disease. A randomized study using similar techniques has been initiated.     

Increased exercise level and plasma lipoprotein concentrations: A one-year,randomized, controlled study in sedentary,middle-aged men

Eighty-one sedentary but healthy men aged 30–55 participated in a 1 yr randomized study of the effects of exercise on plasma lipoprotein concentrations. Forty-eight were assigned to a running program, while 33 remained as sedentary controls (an approximately 3:2 ratio). After 1 yr the running group had become significantly fitter and leaner than the control group. Lipoprotein concentration changes in the runners (vs. controls) uniformly favored reduced risk of coronary heart disease, but were not significant when all 46 participants with complete data were included. However, the 25 men who averaged at least eight miles (12.9 kilometers) per wk of running increased their plasma high-density-lipoprotein (HDL) cholesterol level by 4.4 mg/dl (p = 0.045) and their HDL₂ mass level by 33 mg/dl (p = 0.059), vs. controls. Significant correlations were found for distance run per wk vs. change in plasma HDL-cholesterol (r = 0.48), HDL₂ (r = 0.41), and low-density-lipoprotein cholesterol (r = ?0.31). Changes in percent body fat and in HDL-cholesterol were correlated (r = ?0.47) in runners. There appears to be a threshold at about 8 miles per wk above which a 1-yr running program leads to beneficial lipoprotein changes.     

Cholesterol, cancer, and public health policy

A review of prospective cardiovascular epidemiologic studies reveals an inverse relationship between serum cholesterol levels and cancer mortality in half the studies in which this relationship has been examined. This inverse relationship has been demonstrated only for males, and is most consistently demonstrated for large bowel cancer. However, a review of international and intergroup epidemiologic data reveals that dietary fat intake is positively correlated with mortality rates for all cancers and for large bowel cancer. Internationally, there is also a positive correlation between mortality rates for ischemic heart disease and for cancer, as well as a positive correlation between mean population values of total serum cholesterol levels and cancer mortality. The biologic plausibility of the relationship between low serum cholesterol levels and cancer, and between high dietary fat intake and cancer are examined, with particular reference to large bowel cancer. Models are proposed to provide a coherent framework in which both low serum cholesterol levels and high dietary fat intake are risk factors for carcinogenesis. It is concluded that, on the basis of present knowledge, limitation of dietary fat and cholesterol intake is a prudent public health measure for the prevention of both coronary heart disease and cancer.     

Advances in guidewire technology

Since the introduction in 1979 of a movable guidewire system for PTCA, significant advances have been made in guidewire technology that have improved primary success rates and reduced complications with the use of this system. Coronary stenoses in distal sites or in branch vessels with abrupt angulations can now routinely be reached and crossed with newer-generation guidewires. This report concentrates on the evolution of advances in guidewire technology and outlines changes in guidewire design that have allowed for improved efficacy and safety with the movable wire system. Appropriate cases are presented to illustrate the advantages of available guidewires.     

Prognostic value of submaximal exercise radionuclide ventriculography after myocardial infarction

Submaximal exercise testing with radionuclide ventriculography (RVG) was performed in 117 patients before hospital discharge 17 +/- 7 days (+/- standard deviation) after an acute myocardial infarction (MI). The hypothesis tested in these studies was that submaximal exercise testing coupled to RVG allows the identification of patients at risk for future ischemic events in the subsequent 6 months, irrespective of MI location and type. The sites of MI were characterized as anterior transmural in 33, inferior transmural in 39, limited nontransmural in 18, extensive nontransmural in 24 and indeterminant in 3. During 6 months of follow-up, 9 patients died, 14 had recurrent MI, 18 had refractory angina pectoris, 16 had limiting angina and 17 had congestive heart failure. Discriminant function analysis ranked exercise changes in left ventricular (LV) ejection fraction and end-systolic volume the most important of all clinical, exercise and scintigraphic variables for predicting future cardiac events. The predictive accuracy of changes in LV ejection fraction and end-systolic volume were 93 and 91%, respectively, for the entire group, and were significantly more sensitive than any degree of ST-segment depression or elevation (p less than 0.001). These findings were generally independent of MI location and type. Thus, submaximal exercise RVG after MI is an accurate means of identifying patients at risk for major cardiac events in the 6 months after hospital discharge.     

Simultaneous maximal exercise radionuclide angiography and thallium stress perfusion imaging

Gold-195m is a new ultra-short-lived radionuclide that can be used for cardiac studies. Accurate, reproducible ejection fraction and ventricular wall motion studies can be obtained from first-transit angiography using commercially available imaging and image-processing equipment. The short half-life of gold-195m (30.5 seconds) makes simultaneous dual isotope imaging possible and substantially reduces the radiation exposure from the isotope angiography.The feasibility and possible benefits of performing dual radionuclide studies were evaluated during a single exercise stress test in 24 subjects with known coronary artery disease (CAD) and in 20 normal volunteers. High-quality first-transit angiograms were obtained in all subjects. An 83% sensitivity and 95% specificity for detecting CAD with thallium-201 imaging was noted in this investigation, suggesting that its diagnostic accuracy was not altered by simultaneous dual isotone imaging. When segmental left ventricular (LV) wall motion was compared with thallium-201 perfusion imaging, divergent results were noted in 15 of 44 subjects. An analysis of the ejection fraction (EF) results at rest and stress provided additional information that could be useful in assessing the clinical significance of such differences in segmental wall motion and perfusion.Simultaneous dual isotope imaging appears to be appropriate for situations in which both LV perfusion and function require evaluation. The use of gold-195m allows such information to be obtained from a single exercise test and can thereby reduce the cost and time required for noninvasive evaluations of patients for CAD.     

A new catheter system for coronary angioplasty

A new catheter system has been designed for percutaneous transluminal coronary angioplasty. An independently movable, flexible-tipped guide wire within the balloon dilation catheter facilitates selection of the involved vessel. This guide wire can be passed slowly and carefully beyond the coronary stenosis, permitting safe advancement of the balloon catheter. After testing in animal and cadaver hearts, this system was used in 53 patients (56 stenoses) with single vessel coronary artery disease, with an overall primary success rate of 64 percent. In the last 41 of these 56 cases, use of a balloon catheter with a smaller deflated diameter increased the success rate to 73 percent. In patients with lesions of the left anterior descending coronary artery, the success rate was 89 percent. Three (6 percent) of the 53 patients had complications during coronary arterial dilation that necessitated emergency coronary arterial bypass graft surgery. There were no procedure-related or late cardiac deaths. During the mean follow-up period of 8 months (range 1 to 21), there were one late death (of noncardiac causes) and no late myocardial infarctions. Clinical status was persistently improved in 31 of the 36 patients who had successful dilation. The remaining five patients experienced restenosis at the angioplasty site and return of angina pectoris within 3 months of dilation. Two of these patients had repeat coronary angioplasty with restoration of asymptomatic status, and three had elective coronary bypass graft surgery.     

Noninvasive detection of multivessel disease after myocardial infarction by exercise radionuclide ventriculography

The ability of exercise radionuclide ventriculography to detect multivessel coronary artery disease in patients who survived a single myocardial infarction was assessed. Seventy-four patients who had had myocardial infarction at least 8 weeks earlier underwent cardiac catheterization and exercise radionuclide ventriculography. Thirty-eight patients had had an inferior infarction: 25 with multivessel disease and 13 with single vessel disease of the right coronary artery. Thirty-six patients had had an anterior infarction: 26 with multivessel disease and 10 with single vessel disease of the left anterior descending coronary artery.

Among patients with anterior infarction there was no significant difference between patients with single vessel disease and patients with multivessel disease with regard to resting ejection fraction, exercise ejection fraction, and the mean change from rest to exercise. Patients with single vessel disease had a decrease in ejection fraction from rest to exercise of 2.2 ± 2.7% units (mean) ± standard error [SE]), compared with a decrease of 5.4 ±1.3% units in those with multivessel disease (p = not significant [NS]). Seventeen of 26 (65%) patients with multivessel disease and 6 of 10 (60%) with single vessel disease had a decrease in ejection fraction of at least 5 percentage units (p = NS).

In patients with inferior infarction there was no difference in the mean resting ejection fraction in those with single vessel disease (53 ± 2%) compared with those with multivessel disease (50 ±2%); however, the mean exercise ejection fraction in patients with single vessel disease (57 ± 3%) was significantly higher (p < 0.005) than that in patients with multivessel disease (45 ± 2%). Sixteen of the 25 patients with multivessel disease (64%) but only 1 patient with single vessel disease (7.7%) had a decrease in ejection fraction of at least 5 percentage units (p < 0.001).

A new wall motion abnormality developed in 8 patients with anterior infarction and 11 with inferior infarction with multivessel disease and none with single vessel disease. The sensitivity and specificity in predicting multivessel disease using the criteria of the development of a new wall motion abnormality or a decrease in ejection fraction with exercise of at least 5 percentage units were 80 and 92% for the patients with inferior infarction, but only 69 and 40% for the patients with anterior infarction.

These results suggest that exercise radionuclide angiography can be used to discriminate between single and multivessel disease after inferior myocardial infarction. For patients with anterior infarction, only a new abnormality in wall motion accurately predicts multivessel disease, but this occurred in only one third of such patients.     

Prognostic value of resting and submaximal exercise radionuclide ventriculography after acute myocardial infarction in high-risk patients with single and multivessel disease

In patients who survive the acute phase of myocardial infarction, those with multivessel coronary artery disease generally have a worse prognosis than those with single-vessel disease. However, some patients with significant multivessel stenoses have a good prognosis, whereas some with a significant single-vessel stenosis have a poor prognosis. Thus, although definition of coronary anatomy may be helpful, it is a not a fail-safe prognosticator. In this retrospective analysis, the association of abnormalities at rest and during submaximal exercise testing with radionuclide ventriculography after acute myocardial infarction with major cardiac complications (death, recurrent infarction, severe angina or congestive heart failure) in the ensuing 6 months was assessed in patients with single and multivessel disease. Coronary angiography and submaximal exercise testing with radionuclide ventriculography were performed within 3 months of each other in 42 patients. Eleven of the 16 patients with single-vessel coronary stenosis had major cardiac complications. The subsequent course of these 16 patients was correctly predicted by left ventricular ejection fraction (LVEF) ≤ 0.40 in 8 patients, by LVEF < 0.55 in 7 patients, by failure of LVEF to increase by 0.05 units in 13 patients, and by an increase in left ventricular end-systolic volume index (LVESVI) during exercise >5% above baseline in 11 patients. Of the 26 patients with multivessel coronary artery disease, 24 had major cardiac complications. The subsequent course of these 26 patients was correctly predicted in 13 by LVEF ≤ 0.40, in 20 by LVEF < 0.55, in 25 by a failure of LVEF to increase by 0.05 units during exercise, and in 20 by an increase in LVESVI by > 5% during exercise. Thus, submaximal exercise testing with radionuclide ventriculography may provide valuable prognostic information concerning the occurrence of major cardiac events after myocardial infarction not only in patients with multivessel disease, but also in those with single-vessel disease. Exercise-induced abnormalities of left ventricular function may have greater prognostic importance than the delineation of coronary arterial anatomy or the assessment of residual left ventricular function at rest.