A comparison of treadmill and arm-leg ergometry exercise testing for assessing exercise capacity in patients with peripheral arterial disease

PURPOSE: To compare the results of treadmill exercise testing (TM) to arm-leg ergometry testing (AL) in patients with peripheral arterial disease (PAD). METHODS: Twelve men and 8 women with PAD (mean age, 62 +/- 10 years) completed a treadmill test and an arm-leg ergometer exercise test. Oxygen uptake, heart rate, rate-pressure product (x10(-3)), ratings of claudication and perceived exertion, and power were measured. RESULTS: Peak oxygen uptake, heart rate, and rate-pressure product were similar between TM and AL. Exercise duration was longer and the peak power higher on the AL than on the TM. Claudication pain > or =3/4 was the reason for test termination in all subjects during TM test and in 13 subjects during AL. Nine patients discontinued due to severe claudication on both tests, but the pain occurred later in AL than TM. CONCLUSIONS: Although peak oxygen uptake was similar between the 2 exercise tests, patients with PAD exercised longer and to a higher peak power during the AL. These data suggest that the AL test may be used to evaluate peak exercise capacity in patients with PAD. The AL may also provide an alternate method for detecting PAD and coronary heart disease.     

Increase in myocardial oxygen consumption indexes by exercise training at onset of ischemia in patients with coronary artery disease

It has been unclear whether exercise training of patients with coronary artery disease increases the level of myocardial oxygen consumption, as indicated by heart rate and double product of heart rate and systolic blood pressure, at which electrocardiographic evidence of myocardial ischemia develops. To assess this question we evaluated the experience of 10 patients with coronary artery disease who underwent a modest-level exercise training program for 6 months. All of these subjects had achieved a training effect, had developed electrocardiographic evidence of ischemia during initial exercise testing, had not increased the amount of cardiac medication taken, and had not been taking digoxin. After completion of the training period, the mean heart rate at which electrocardiographic evidence of ischemia developed increased from 107 +/- 19 to 119 +/- 23 beats/min (p less than .05) and the mean double product increased from 166 +/- 18 to 209 +/- 51 X 10(2) mm Hg X beats/min (p less than .05). Eight of the 10 patients demonstrated an increase in heart rate at onset of ischemia (p less than .02), and seven of the eight in whom double product could be assessed manifested an increase in this parameter at onset of ischemia (p less than .05). Thus the rate of myocardial oxygen consumption at which myocardial ischemia develops, as indirectly assessed by heart rate and double product, can be favorably altered by 6 months of moderate-level exercise training.     

Correlation between exercise test and coronariography]

In order to evaluate the sensibility and specificity of the maximal treadmill exercise-stress test, a correlation was made, in fifty patients, of the resus of the test and the findings at selective coronary arteriography. None of the patients had received cardioactive drugs previous to the study. Among twenty-nine patients with proven coronary disease, three had false negative exercise tests. The remaining twenty-six cases had positive tests. The sensitivity of the method (reliability in identifying the presence of disease) was 89.7%. Twelve of twenty-one subjects with normal coronary arteries had negative exercise tests. In eight patients without coronary artery lesions, the exercise test was positive (false positive tests). An additional patient had an equivocal response and is included among the false positive responses. These nine-patients form a special group since they had severe heart disease, even though it was not due to atherosclerosis of the major coronary vessels. The specificity of the test (reliability in identifying the absence of disease) was 57.1%. However, in the absence of other heart disease, none of the subjects with normal coronary arteries had a false positive response. An analysis is made of the possible causes of these false negative and false positive responses. It was also shown in this study that the patients with coronary artery disease and positive treadmill tests had a definite functional aerobic impairment as well as a significant reduction in such indices of myocardial oxygen consumption as the heart rate and the double product (pressure-pulse), when compared to the subjects with normal coronary vessels and negative tests. In the group of patients with false positive responses, these parameters were not significantly different from the normals. The exercise-stress test protocol used in this study appears to have an adequate sensibility and an acceptable specificity.     

Features of the exercise test that reflect the activity of ischemic heart disease out of hospital

To better understand the relationship between the transient myocardial ischemia seen during an exercise test and ischemic activity out of hospital, 39 patients with well-documented coronary artery disease underwent standard treadmill exercise testing (Bruce protocol) and 24 to 48 hr of continuous ambulatory electrocardiographic monitoring during normal daily activities. A total of 245 episodes of transient ischemia were recorded in 21 of 32 patients with positive exercise electrocardiograms (group I), whereas seven patients with negative test results (group II) had no episodes of transient ischemia, during monitoring out of hospital (p less than .01). Certain measures in the exercise test were related to the severity of ischemia out of hospital: there were more episodes and a greater total duration of transient ischemia per 24 hr of ambulatory monitoring in patients who developed ischemic electrocardiographic changes before 6 min of exercise (p less than or equal to .021) or at a heart rate of less than 150 beats/min (p = .005) and in those in whom these ST segment changes persisted for more than 5 min after exercise (p less than or equal to .016). In contrast, there was no relationship between transient ischemia out of hospital and the commonly quoted exercise variables: chest pain, total exercise duration, and the maximum levels of heart rate, systolic blood pressure, and double product. Thus, patients with coronary artery disease and negative exercise electrocardiograms are most unlikely to experience active ischemia during normal daily life.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise thallium testing in ventricular preexcitation

Ventricular preexcitation, as seen in Wolff-Parkinson-White syndrome, results in a high frequency of positive exercise electrocardiographic responses. Why this occurs is unknown but is not believed to reflect myocardial ischemia. Exercise thallium testing is often used for noninvasive assessment of coronary artery disease in patients with conditions known to result in false-positive electrocardiographic responses. To assess the effects of ventricular preexcitation on exercise thallium testing, 8 men (aged 42 +/- 4 years) with this finding were studied. No subject had signs or symptoms of coronary artery disease. Subjects exercised on a bicycle ergometer to a double product of 26,000 +/- 2,000 (+/- standard error of mean). All but one of the subjects had at least 1 mm of ST-segment depression. Tests were terminated because of fatigue or dyspnea and no patient had chest pain. Thallium test results were abnormal in 5 patients, 2 of whom had stress defects as well as abnormally delayed thallium washout. One of these subjects had normal coronary arteries on angiography with a negative ergonovine challenge, and both had normal exercise radionuclide ventriculographic studies. Delayed thallium washout was noted in 3 of the subjects with ventricular preexcitation and normal stress images. This study suggests that exercise thallium testing is frequently abnormal in subjects with ventricular preexcitation. Ventricular preexcitation may cause dyssynergy of ventricular activation, which could alter myocardial thallium handling, much as occurs with left bundle branch block. Exercise radionuclide ventriculography may be a better test for noninvasive assessment of coronary artery disease in patients with ventricular preexcitation.     

Arm-crank ergometry: a new method for the evaluation of coronary artery disease

We have developed an electrocardiographic stress test to evaluate coronary heart disease using an arm-crank device (modified bicycle ergometer) in patients unable to perform leg exercise. With an initial work load of 200 kg-m/min at 40 revolutions/min for 3 minutes, followed by 100 kg-m/min increments every 3 minutes to a maximum of 700 kg-m/min at the same speed, a linear relation between the increase in heart rate and work load was observed. Twenty-one patients underwent both conventional treadmill exercise (modified Bruce protocol) and arm-crank exercise on separate days. Peak heart rate was slightly slower with arm-crank exercise (81 ± 4 [standard error] vs. 85 ± 3 percent of maximal predicted heart rate for age, P < 0.02) but peak systolic blood pressure and heart rate-systolic blood pressure product (double product) did not differ significantly (157 ± 7 vs. 154 ± 6 mm Hg, P > 0.5) and (22.0 ± 1.2 vs. 22.5 ± 1.2 × 10³, P > 0.1). Ten patients with documented coronary artery disease, including 7 with angina pectoris, had an ischemie S-T segment response (0.08 second depression greater than 1 mm) by both methods and 10 patients (7 with previous myocardial infarction and 3 with normal coronary arteriograms) had negative results by both techniques. One patient with normal coronary arteriograms had a negative arm-crank test and a positive treadmill test. In 26 patients unable to perform leg exercise the mean peak heart rate, systolic blood pressure and double product with arm-crank exercise were not significantly different (P > 0.05) from those achieved by the ambulatory patients (73.2 ± 1.9 vs. 81.0 ± 4.0 percent, 167 ± 8 vs. 157 ± 7 mm Hg and 22.4 ± 1.2 vs. 22.0 ± 1.4 × 10³, respectively). Six of 26 patients unable to perform leg exercise had a positive arm-crank test. Four of these six patients had angina pectoris and three had a previous myocardial infarction. We conclude that arm-crank exercise is comparable to treadmill exercise and is a reliable alternative method for the evaluation of suspected coronary artery disease in patients unable to perform leg exercise.     

Correlation of plasma propranolol concentration with therapeutic response in patients with angina pectoris.

The therapeutic response to propranolol was evaluated in patients with documented coronary artery disease at doses varying from 40 to 320 mg/day. Therapeutic response was quantified by evaluating exercise performance on a treadmill and then related to plasma propranolol concentration. Plasma propranolol was defined in terms of beta-adrenergic blockade by comparison with dose (concentration) response curves in normal subjects. Individual therapeutic benefit occurred at doses which averaged 144 +/- 21 mg/day and at concentrations which averaged 30 +/- 7 ng/ml. There was a wide variation between both dose and concentration among the patients at maximum therapeutic response, but when the plasma propranolol was related to pharmacologic activity, the maximum therapeutic response was observed between 64 to 98% of total blockade. Despite the increased exercise performance in these patients, the double product of heart rate and systolic blood pressure was always less, suggesting either an alteration of the relation between myocardial oxygen consumption and the double product during propranolol or a reduction on oxygen delivery to the myocardium as the result of beta-adrenergic blockade of the coronary vasculature.     

Attenuation of exercise-induced ST depression during combined isometric and dynamic exercise in coronary artery disease

ST-segment depression was measured during submaximal dynamic (treadmill) and combined isometric-dynamic (isodynamic) exercise at comparable rate-pressure products in 11 patients (mean age 63 years) with stable coronary artery disease who were participating in an exercise training program. Each patient completed 3 separate trials. Trial 1 (baseline) was a submaximal treadmill exercise test to determine the threshold heart rate-systolic blood pressure (rate-pressure product) for ST-segment depression (greater than or equal to 1.0 mm). During trials 2 and 3, patients performed (in random order) dynamic treadmill exercise and isodynamic exercise (treadmill walking 1.5 to 2.0 mph carrying 15 to 25 kg) until threshold rate-pressure product was achieved. During trial 1, each patient showed significant ST depression (mean 1.7 mm) at target rate-pressure product (mean 18,200). Subsequent dynamic exercise trials 2 and 3 showed similar mean ST depression (1.5 mm) and rate-pressure product (18,000). During isodynamic exercise trials 2 and 3, subjects showed only minimal ST depression (mean 0.4 mm) at a rate-pressure product similar to dynamic exercise (mean 18,590). Heart rates were significantly lower (-10/min) and systolic (+20 mm Hg) and diastolic (+25 mm Hg) pressure was higher during isodynamic exercise (p less than 0.05). The rate-pressure product is not a valid index of ST response during isodynamic exercise in stable exercise-trained cardiac patients. Attenuation of ST depression during isodynamic exercise may be attributed to a combination of increased diastolic perfusion pressure, decreased heart rate and possibly to reductions in venous return and ventricular diastolic wall tension due to increased intrathoracic and abdominal pressure.     

The threshold for myocardial ischemia varies in patients with coronary artery disease depending on the exercise protocol

It is generally accepted that angina pectoris and, presumably, myocardial ischemia occur at a fixed heart rate-systolic blood pressure product in a given patient. This concept of a fixed threshold has recently been challenged. To evaluate the effects of varying exercise intensity on the ischemic threshold, 33 patients with coronary artery disease and provokable myocardial ischemia, documented by thallium-201 myocardial perfusion imaging, underwent two exercise tests 2 to 7 days apart. A symptom-limited incremental treadmill exercise test was followed by a 20 min submaximal treadmill test at an intensity approximating 70% of the peak heart rate attained during the incremental test. During the incremental exercise test, angina pectoris developed in 16 patients and 17 patients were asymptomatic. At least 0.1 mV of ST segment depression developed in all subjects during the incremental exercise test at a mean exercise duration of 5.3 +/- 2.6 min, a rate-pressure product of 19,130 +/- 5,735 and oxygen uptake of 19.6 +/- 7.0 ml/kg per min. During the submaximal exercise test, 28 (85%) of the 33 patients had significant ST segment depression. Of these patients, 24 (86%) were asymptomatic, including 10 patients who had previously reported anginal symptoms during the incremental test. The average time to onset of 0.1 mV ST segment depression during the submaximal test was 8.1 +/- 4.5 min. These changes occurred at a rate-pressure product of 15,250 +/- 3,705 and an oxygen uptake of 14.3 +/- 5.9 ml/kg per min, and were significantly (p less than 0.001) lower than values observed during the graded exercise.(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of exercise-induced changes in R wave amplitude in asymptomatic men with electrocardiographic ST-T changes at rest

Fifty asymptomatic men, 44 (88 percent) of whom were pilots or allied aviation personnel, were referred because of resting ST-T electrocardiographic changes indistinguishable from those of myocardial ischemia. Because of the nature of their occupations, cardiac catheterization was performed to establish the presence or absence of coronary artery disease. Exercise tests were performed and analyzed retrospectively with respect to exercise-induced changes in the S-T segment and R wave amplitude. The results were correlated with coronary angiographic and echocardiographic findings.The 50 subjects were classified into two groups: Group I, 5 men with angiographically proved coronary artery disease, and Group II, 45 men without significant coronary arterial obstruction. Analysis of the S-T segment changes at peak exercise showed 21 subjects (42 percent) with a positive exercise test and 29 (58 percent) with a negative test. All subjects in Group I had a positive test. Sixteen subjects (35 percent) in Group II had a false positive result. Analysis of exercise-induced changes in R wave amplitude revealed that six subjects had a positive R wave response on the basis of sum of the changes in voltage in the leads measured (Δ∑R). Four of the six subjects had coronary artery disease and the other two were thought to have a cardiomyopathy. One subject with coronary artery disease had a negative R wave response. Echocardiography revealed five subjects with asymmetric septal hypertrophy; two of these had a positive exercise test and three a negative test on the basis of S-T segment criteria.Thus, symptom-limited treadmill exercise testing of asymptomatic men with resting ST-T electrocardiographic changes produced a high incidence rate of false positive results when S-T segment criteria were used, whereas analysis of changes in R wave amplitude yielded only two false positive results, both in men who had evidence of other heart disease.     

Heart rate adjustment of ST segment depression for improved detection of coronary artery disease

Normal values for heart rate-adjusted indexes of ST segment depression during treadmill exercise electrocardiography (the ST segment/heart rate slope and the delta ST segment/heart rate index) were derived from evaluation of 150 subjects with a low likelihood of coronary artery disease, including 100 normal subjects and 50 subjects with nonanginal chest pain. Partitions chosen by the method of percentile estimation to include 95% of normal subjects remained highly specific in subjects with nonanginal pain syndromes. Sensitivities of the derived partitions for detection of myocardial ischemia were tested in an additional 150 patients with a high likelihood of coronary disease, including 100 patients with angiographically demonstrated coronary obstruction and 50 patients with stable angina. In contrast to the 68% (102 of 150 subjects) sensitivity of standard exercise electrocardiographic criteria for the detection of disease in this population, the sensitivity of an ST segment/heart rate slope partition of 2.4 muV/beats/min was 95% (142 of 150 subjects, p less than 0.001), and the sensitivity of a delta ST segment/heart rate index partition of 1.6 muV/beats/min was 91% (137 of 150 subjects, p less than 0.001). Analysis of receiver-operating curves confirmed the superior performance of the heart rate-adjusted indexes throughout a wide range of test specificities. These findings suggest that heart rate adjustment of ST segment depression can markedly improve the clinical usefulness of the treadmill exercise electrocardiogram.     

Myocardial perfusion and left ventricular performance during exercise-induced ST-segment depression in apparently healthy subjects

Ischemic-like ST-segment depression seen during exercise in apparently healthy subjects has previously been noted, but the cause of this change is unknown. The aim of this study was to investigate the pathophysiology of this electrocardiographic change. Ten healthy subjects who developed an electrocardiographic "ischemic" pattern of ST change during treadmill exercise testing were studied. All subjects underwent both thallium-201 myocardial perfusion imaging and radionuclide angiocardiography at rest and during exercise at a time when abnormal ST changes appeared, and demonstrated a normal homogeneous pattern of thallium-201 distribution on both rest and exercise images. Overall, left ventricular ejection fraction rose from 0.60 +/- 0.06 (mean +/- SD) at rest to 0.65 +/- 0.07 with exercise. None of the subjects had regional wall motion abnormalities at rest or during exercise. These results are different from the findings observed in patients with coronary heart disease and angina pectoris in whom regional abnormalities in both perfusion and left ventricular performance have been noted during exercise. Therefore it would seem that myocardial ischemia is not likely to be a tenable explanation for the electrocardiographic "ischemic" changes in these apparently healthy subjects.     

Limitations of exercise testing in critical left coronary artery disease.

Exercise testing was evaluated in 51 patients with critical left coronary artery disease (LCA) documented by coronary arteriography within two weeks of their bicycle ergometer (26 patients) or treadmill (25 patients) electrocardiographic study. Adequate tests, as defined by the patient having reached 85% of predicted maximum heart rate, were achieved in only 16 patients on the ergometer (62%) and in 21 (84%) on the treadmill. Nevertheless mean maximum double product (220 vs 232) and mean exercise time (4.6 min vs 5.0 min.) were similar (p:NS). The sensitivity for ergometry and treadmill testing was 75 and 62% respectively. If however we include those negative studies in which for various reasons patients were unable to achieve 85% of their predicted maximal heart rate (i.e., inadequate studies), sensitivity was only 46 and 52% respectively. Thus a sizable group of patients with critical LCA disease cannot adequately perform exercise tests especially on the ergometer; and over half of all such patients studied will be found for one reason or another to respond negatively, regardless of exercise protocol.     

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) (p less than 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).(ABSTRACT TRUNCATED AT 250 WORDS)     

Treadmill exercise test in aortic stenosis and mitral stenosis.

The incidence of positive submaximal treadmill exercise tests was evaluated in patients with mitral stenosis and aortic stenosis, no electrocardiographic evidence of left ventricular hypertrophy, and normal coronary arteries on angiography. Seven of 19 patients (37 percent) with aortic stenosis (53 to 80 mm Hg gradient across the aortic valve) had greater than or equal to 1.0 mm of ischemic S-T segment depression during or after a submaximal treadmill test. Three of 15 patients (20 percent) with mitral stenosis (11 to 22 mm Hg mean gradient across the mitral valve) had greater than or equal to 1.0 mm of ischemic S-T segment depression during or after a submaximal treadmill exercise test. Patients with significant valvular disease, no electrocardiographic evidence of left ventricular hypertrophy, and normal coronary arteries may have a positive submaximal treadmill exercise test due to an unfavorable balance between myocardial oxygen supply and myocardial oxygen demand.     

Blood pressure, heart rate, pressure-rate product and electrocardiographic changes in healthy children during treadmill exercise.

Heart rate, systolic and diastolic blood pressure, rate-pressure product and electrocardiographic changes were measured in 288 healthy children during treadmill exercise. A constant speed (3.5 miles/hour) protocol was used to facilitate the measurements of physiologic data during exercise. Because responses to exercise vary with size, the children were separated into four groups according to body surface area. Comparisons were also made between male and female and between black and white children. The values for heart rate and systolic pressure showed excellent reproducibility in repeated tests. These data establish for clinical use reference values for children during treadmill exercise.     

Prevalence and magnitude of S-T segment and T wave abnormalities in normal men during continuous ambulatory electrocardiography

Fifty asymptomatic normal male volunteers, mean age 44.6 years (range 35 to 59), were prospectively studied to ascertain the prevalence and magnitude of S-T segment and T wave changes detected during continuous ambulatory electrocardiographic monitoring. Transient S-T segment depression of 1.0 mm or more was recorded in 15 (30 percent) of the subjects, and labile T wave inversion of up to 3 mm occurred in an additional 18 (36 percent). The presence of ST-T changes during monitoring did not correlate with age, daily activity status or heart rate. There was also no correlation with the S-T segment response or work performance during treadmill exercise testing. It is concluded that S-T segment depression and T wave inversions are commonly observed during ambulatory electrocardiographic monitoring of normal men. Therefore, similar changes observed in patients with coronary artery disease should be interpreted with caution.     

Exercise testing for sports and the exercise prescription

The uses of the exercise test continue to grow and diversify. Familiarity with the mechanics, logistics, and interpretation of these tests leads to their optimal use. The application of exercise testing for competitive or recreational sports, cardiovascular fitness exercise training, and cardiac rehabilitation is the focus of this review. Many test protocols are available, but treadmill testing is the most widely used. The inclusion of thallium scintigraphy in the exercise protocol requires additional time and expense and is best reserved for those in whom the exercise electrocardiographic response cannot be adequately interpreted. Exercise testing is a relatively safe procedure, providing that adequate screening of individuals for unstable cardiac or medical conditions has been performed. The test must be administered by experienced personnel in a setting where the necessary emergency resuscitative equipment is available. Adequate interpretation of the exercise test requires knowledge of the individual being tested and of the reason the test is being performed. Complete analysis of the exercise test includes electrocardiographic response (ST segment changes and rhythm disturbances), hemodynamic response (heart rate and blood pressure before, during, and after exercise), and functional capacity (exercise duration, symptoms, conversion to MET's). When exercise tests are employed to establish a diagnosis of coronary artery disease, an assessment of the pretest likelihood (prevalence) of disease is essential in deriving a reasonable assessment of the probability of disease after the test has been performed and reviewed. This information is particularly important when screening asymptomatic subjects for underlying coronary disease before they engage in an exercise program. Exercise testing of individuals with known cardiac disease prior to engaging in competitive or recreational sports can yield much useful information. In addition to a knowledge of the underlying cardiac condition, the type and intensity of the sport being performed must be taken into account when exercise testing is performed for athletic screening. Individuals with congenital or acquired valvular heart disease, coronary artery disease, and rhythm disturbances should undergo an exercise test as part of the pretraining evaluation. Patients with ischemic heart disease, especially those who have had a recent myocardial infarction or have undergone coronary artery bypass surgery, require counseling regarding their ability to perform certain activities of daily living and to return to work. Exercise testing can be a useful tool in establishing activity guidelines for these individuals.(ABSTRACT TRUNCATED AT 400 WORDS)     

Comparison of supine and erect bicycle exercise electrocardiography in coronary heart disease: Accentuation of exercise-induced ischemic ST depression by supine posture

Exercise-induced electrocardiographic ST depression was compared during supine and erect graded bicycle exercise in 43 patients with chest pain but no prior myocardial infarct; all had ≥1 mm of ST depression during either erect or supine exercise; 16 had multivessel, 24 had 1-vessel and 3 had no coronary artery disease. Supine exercise used 4 minutes/stage and erect exercise used either 4 minutes or 3 minutes/stage with identical graded work loads for both postures. Chest pain occurred in 31 patients during erect and in 29 during supine exercise. ST depression was ≥1 mm in 28 patients during erect exercise and in all 43 during supine exercise (p <0.001); mean maximal ST depression was 1.3 ± 0.2 mm during erect and 2.6 ± 0.2 mm during supine exercise (p <0.001). Maximal work load was higher during erect than supine exercise (745 ± 32 versus 678 ± 32 kpm/min; p <0.001). The accentuation of ST depression by supine posture was not attributable to the changes in heart rate, rate-pressure product or mean blood pressure during supine versus erect exercise. In the 10 patients who had 2 erect bicycle tests using work load durations of 3 and 4 minutes, the maximal ST depression was not significantly different (erect 3 minutes 1.3 ± 0.5 mm and erect 4 minutes 1.4 ± 0.4 mm). In 7 patients who also had a maximal treadmill exercise test, the maximal ST depression was significantly greater during supine exercise (2.3 ± 0.4 mm) than during either an erect bicycle test (0.6 ± 0.4 mm) or treadmill exercise (0.7 ± 0.4 mm) (p <0.05). Supine posture should be considered as an important potentiator of exercise-induced myocardial ischemia whem comparing indicators such as electrocardiography, radionuclide ventriculography and thallium-201 myocardial perfusion imaging during exercise.     

运动试验中QRSc延长对诊断冠心病的意义

目的　探讨运动后QRSc(心率校正QRS)变化对冠心病的诊断价值。方法　测定分析 86例病人 ,均进行活动平板试验及冠脉造影。 2 2例冠脉造影排除冠心病 ,其他 6 4例冠脉造影确定冠心病。对比二组受检者在运动前、运动后即刻、2分、4分、6分的QRSc改变。结果　冠脉正常组运动后QRSc缩短 ,冠心病组运动后QRSc延长 ,二组在运动前QRSc无显著差异 (P >0 0 5 )。运动后即刻、2分、4分、6分的QRSc均有非常显著差异 (P <0 0 1)。二组各自组内比较 ,运动前与运动后即刻无显著差异 (P >0 0 5 ) ,而与运动后 2分、4分、6分均有非常显著差异 (P <0 0 1)。结论　运动后QRS时限延长是心肌缺血的标志之一。平板运动试验时在测量ST段的同时 ,测量QRS时限 ,计算QRSc =QRS RR ,特别是运动后 2分以后的QRSc更有意义 ,从而提高冠心病心肌缺血早期诊断的阳性率和准确性