Radionuclide imaging correlatives of heart rate impairment during maximal exercise testing

A lower than normal heart rate response to maximal dynamic exercise, known as chronotropic incompetence or heart rate impairment, has been demonstrated to have a poor prognosis. In order to better describe patients with this finding, 156 men with coronary heart disease were evaluated. All patients were studied with maximal exercise testing, including measurements of oxygen consumption, exercise electrocardiograms, thallium scintigraphy and radionuclide ventriculography. Chronotropic incompetence was defined as a maximal heart rate 1 standard error of the estimate below the regression line of age versus maximal heart rate on two separate exercise tests. In patients so defined, mean maximal oxygen consumption was significantly lowered and angina was the major reason for stopping exercise on the treadmill. Patients with chronotropic incompetence not limited by angina had more evidence of myocardial scar and dysfunction and had a greater prevalence of three vessel coronary disease than did patients with a normal heart rate response. Radionuclide testing results suggest that among patients with chronotropic incompetence, those with angina have a better prognosis than those who do not have angina but who may have myocardial dysfunction

The effect of resting ST segment depression on the diagnostic characteristics of the exercise treadmill test

AbstractOBJECTIVESThe aim of this study is to demonstrate the effect of resting ST segment depression on the diagnostic characteristics of the exercise treadmill test.BACKGROUNDPrevious studies evaluating the effect of resting ST segment depression on the diagnostic characteristics of exercise treadmill test have been conducted on relatively small patient groups and based only on visual electrocardiogram (ECG) analysis.METHODSA retrospective analysis of data collected prospectively was performed on consecutive patients referred for evaluation of chest pain. One thousand two hundred eighty-two patients without a prior myocardial infarction underwent standard exercise treadmill tests followed by coronary angiography, with coronary artery disease defined as a 50% narrowing in at least one major epicardial coronary artery. Sensitivity, specificity, predictive accuracy and area under the curve of the receiver operating characteristic (ROC) plots were calculated for patients with and without resting ST segment depression as determined by visual or computerized analysis of the baseline ECG.RESULTSSensitivity of the exercise treadmill test increased in 206 patients with resting ST segment depression determined by visual ECG analysis compared with patients without resting ST segment depression (77 ± 7% vs. 45 ± 4%) and specificity decreased (48 ± 12% vs. 84 ± 3%). With computerized analysis, sensitivity of the treadmill test increased in 349 patients with resting ST segment depression compared with patients without resting ST segment depression (71 ± 6% vs. 42 ± 4%) and specificity decreased (52 ± 9% vs. 87 ± 3%) (p < 0.0001 for all comparisons). There was no significant difference in the area under the curve of the ROC plots (0.66–0.69) or the predictive accuracy (62–68%) between the four subgroups.CONCLUSIONSThe diagnostic accuracy and high sensitivity of the exercise treadmill test in a large cohort of patients with resting ST segment depression and no prior myocardial infarction support the initial use of the test for diagnosis of coronary artery disease. The classification of resting ST segment depression by method of analysis (visual vs. computerized) did not affect the results

A randomized trial of the effects of 1 year of exercise training on computer-measured ST segment displacement in patients with coronary artery disease

As part of a randomized trial of the effects of 1 year of exercise training on patients with stable coronary artery disease, 48 patients who exercised and 59 control patients had computerized exercise electrocardiography performed initially and 1 year later. The patients who had exercise training as an intervention had a 9% increase in measured maximal oxygen consumption and significant decreases in heart rate at rest and during submaximal exercise. ST segment displacement was analyzed 60 ms after the end of the QRS complex in the three-dimensional X,Y and Z leads and utilizing the spatial amplitude derived from them. Statistical analysis by ttesting yielded no significant differences between the groups except for less ST segment displacement at a matched work load, but this could be explained by a lowered heart rate. Analysis of variance yielded some minor differences within clinical subgroups, particularly in the spatial analysis. Obvious changes in exercise-induced ST segment depression could not be demonstrated in this heterogeneous group of selected volunteers with coronary artery disease secondary to an exercise program

Comparison of the ramp versus standard exercise protocols

To compare the hemodynamic and gas exchange responses of ramp treadmill and cycle ergometer tests with standard exercise protocols used clinically, 10 patients with chronic heart failure, 10 with coronary artery disease who were asymptomatic during exercise, 11 with coronary artery disease who were limited by angina during exercise and 10 age-matched normal subjects performed maximal exercise using six different exercise protocols. Gas exchange data were collected continuously during each of the following protocols, performed on separate days in randomized order: Bruce, Balke and an individualized ramp treadmill; 25 W/stage, 50 W/stage and an individualized ramp cycle ergometer test.Maximal oxygen uptake was 16% greater on the treadmill protocols combined (21.4 ± 8 ml/kg per min) versus the cycle ergometer protocols combined (18.1 ± 7 ml/kg per min) (< 0.01), although no differences were observed in maximal heart rate (131 ± 24 versus 126 ± 24 beats/min for the treadmill and cycle ergometer protocols, respectively). No major differences were observed in maximal heart rate or maximal oxygen uptake among the various treadmill protocols or among the various cycle ergometer protocols. The ratio of oxygen uptake to work rate, expressed as a slope, was highest for the ramp tests (slope ± SEE ml/kg per min = 0.80 ± 2.5 and 0.78 ±1.7 for ramp treadmill and ramp cycle ergometer, respectively). The slopes were poorest for the tests with the largest increments in work (0.62 ± 4.0 and 0.59 ± 2.8 for the Bruce treadmill and 50 W/stage cycle ergometer, respectively).Normal subjects demonstrated a greater slope (0.71 ± 4.2) than did patients with chronic heart failure (0.53 ± 2.8), coronary artery disease (0.51 ± 2.6) and angina (0.53 ± 3.1) (< 0.001). The difference between measured and predicted maximal oxygen uptake was greatest for the tests with the largest increments between stages (>1 metabolic equivalent (MET) for the Bruce treadmill and 50 W/stage cycle ergometer) and least for the tests with the smallest increments between stages (ramp tests and 25 W/stage cycle ergometer). These findings suggest that the exercise protocol, even when the same mode is used, can result in marked variations in maximal oxygen uptake and the dynamics of gas exchange during exercise testing

Maximal exercise testing and gas exchange in patients with chronic atrial fibrillation

AbstractTo evaluate the response of patients with chronic atrial fibrillation to exercise, 50 men (mean age 65 ± 8 years) with atrial fibrillation underwent a maximal exercise test using respiratory gas exchange techniques. Patients were classified by the presence (n = 29) or absence (“lone atrial fibrillation,” (n = 21) of underlying heart disease. Responses were evaluated at a standard submaximal work load (3.0 mph. [4.8 km/h] 0% grade), at the gas exchange anaerobic threshold and at maximal exercise. For all 50 patients, the mean maximal oxygen uptake was 20.6 ml/kg per min, which approximates 85% of the aerobic capacity predicted for age-matched normal individuals.Patients with lone atrial fibrillation demonstrated normal exercise capacity in contrast to patients with atrial fibrillation and known heart disease (22.7 ± 5 versus 19.1 ± 5.0 ml/kg per min, p < 0.05). The mean maximal heart rate (176 ± 30 beats/min) was approximately 20 beats/min higher than that expected for age, was extremely variable and accounted for only 8% of the variance in maximal oxygen uptake. Maximal heart rate in subjects with lone atrial fibrillation was higher than that of subjects with atrial fibrillation and known heart disease (189 ± 32 versus 166 ± 24 beats/min, p < 0.01). Stepwise regression analysis revealed that maximal systolic blood pressure accounted for 19% of the variance in maximal oxygen uptake (VO2max), suggesting that systolic function is an important determinant of exercise performance in atrial fibrillation.It is concluded that 1) the exercise response in patients with lone atrial fibrillation differs markedly from the typical heterogeneous group of patients with atrial fibrillation and underlying heart disease, 2) the higher maximal heart rate observed in patients with lone atrial fibrillation may be a compensation for the loss of atrial function, and 3) exercise impairment in patients with atrial fibrillation is due to underlying heart disease and not the arrhythmia itself