Improvement in exercise performance after unsuccessful myocardial revascularization

Exercise stress testing before and after successful multivessel percutaneous transluminal coronary angioplasty

Controversy exists regarding the diagnostic accuracy, optimal technique, and timing of exercise testing after percutaneous coronary intervention. The objectives of the present study were to analyze variables and the power of exercise testing to predict restenosis or a new lesion, 6 months after the procedure. Eight-four coronary multi-artery diseased patients with preserved ventricular function were studied (66 males, mean age of all patients: 59 +/- 10 years). All underwent coronary angiography and exercise testing with the Bruce protocol, before and 6 months after percutaneous coronary intervention. The following parameters were measured: heart rate, blood pressure, rate-pressure product (heart rate x systolic blood pressure), presence of angina, maximal ST-segment depression, and exercise duration. On average, 2.33 lesions/patient were treated and restenosis or progression of disease occurred in 46 (55%) patients. Significant increases in systolic blood pressure (P = 0.022), rate-pressure product (P = 0.045) and exercise duration (P = 0.003) were detected after the procedure. Twenty-seven (32%) patients presented angina during the exercise test before the procedure and 16 (19%) after the procedure. The exercise test for the detection of restenosis or new lesion presented 61% sensitivity, 63% specificity, 62% accuracy, and 67 and 57% positive and negative predictive values, respectively. In patients without restenosis, the exercise duration after percutaneous coronary intervention was significantly longer (460 +/- 154 vs 381 +/- 145 s, P = 0.008). Only the exercise duration permitted us to identify patients with and without restenosis or a new lesion.

Exercise tolerance and work ability following aorto-coronary bypass surgery

This investigation was performed to study the reasons for receiving disability pension after aortocoronary bypass surgery. During the period March 1983 to November 1985, 250 patients underwent aortocoronary bypass surgery. At a mean follow-up of 4.9 years (range 3.6-6.7) after the operation, 31 patients were dead. Of the 219 survivors, all except four underwent a follow-up examination including an exercise test. The mean physical work capacity had increased from 92.2 W preoperatively to 119.3 W at follow-up (p < 0.001). At follow-up, however, 72 patients had received disability pension. The percentage of positive ECG-tests were equal among those who were working and those who had received disability pension. We suggest that, among those who had received disability pension, about 50% were in sufficient physical condition to manage their previous jobs or another type of job. Reasons other than physical working capacity played an important part as criteria for receiving disability pension.

Value and limitations of exercise stress testing to predict the functional results of coronary artery bypass grafting

To assess the value of exercise stress testing to predict the functional result of revascularization, 90 patients were evaluated by coronary angiography and exercise testing pre and postoperatively. Patients were classified on the basis of the postoperative angiogram in a group with successful surgery and a group with unsuccessful surgery. The predictive accuracy positive of ST segment depression to detect unsuccessful surgery was 67% The predictive accuracy negative was 61%. The best predictor of unsuccessful surgery was residual angina pectoris after revascularization with predictive value positive and negative of 85% and 60%, respectively. Thus exercise stress testing has limited value to accurately predict the degree of revascularization.

Significance of silent myocardial ischemia after coronary artery bypass surgery

The prevalence and prognostic significance of transient myocardial ischemia after coronary artery bypass grafting (CABG) were evaluated. In 3 studies, ischemia was found in an average of 24% of patients by ambulatory electrocardiographic monitoring at 3-12 months after CABG. An average of 36% of patients in 3 other studies experienced ischemic ST-segment depression during exercise testing at 4-50 months after CABG. Of the ischemic episodes, 77% were silent during exercise testing. In the Coronary Artery Surgery Study (CASS) randomized patient subsets, survival at 12 years was significantly lower for patients who had either silent or symptomatic ischemia during exercise testing at 6 months after CABG compared with those who had no ischemia.

Prevalence and prognostic significance of silent and symptomatic ischemia after coronary bypass surgery: a report from the Coronary Artery Surgery Study (CASS) randomized population

The prevalence and prognostic significance of postoperative myocardial ischemia, as detected by exercise testing, were prospectively assessed in 174 patients from the Coronary Artery Surgery Study (CASS) randomized surgical population who had exercise testing before and 6 months after coronary artery bypass graft surgery. Whereas the prevalence of symptomatic ischemia significantly decreased postoperatively (52% vs. 6%, p less than 0.001), the frequency of silent myocardial ischemia did not change (30% vs. 29%). Survival at 12 years after bypass surgery based on the 6-month postoperative exercise test results was significantly better for the 112 patients with no ischemia (80%) than for the 51 patients with silent ischemia (68%) or the 11 patients with symptomatic ischemia (45%). These data show that coronary artery bypass graft surgery diminishes the overall prevalence of symptomatic but not silent ischemia and that both silent and symptomatic ischemia adversely affect the postoperative prognosis of these patients.

Assessment of coronary bypass surgery and percutaneous transluminal coronary angioplasty

Coronary bypass surgery developed as another in a line of surgical procedures dating back more than 60 years. The medical profession at first assessed this procedure with time-honored anecdotal techniques. Gradually, for a variety of reasons, improved methods of comparisons worked their way into assessments of bypass surgery. Randomized controlled trials met resistance but have been very influential. Assessment of percutaneous transluminal coronary angioplasty has benefited from the knowledge generated during the last 25 years, but clinicians have been slower to apply the most advanced techniques.

Usefulness of Holter monitoring to improve the sensitivity of exercise testing in determining the degree of myocardial revascularization after coronary artery bypass grafting for stable angina pectoris

To assess whether Holter monitoring improves the sensitivity of exercise testing in identifying incomplete myocardial revascularization, both tests were performed in 45 patients from 3 to 5 months after elective coronary artery bypass grafting (CABG) for stable angina pectoris. Coronary angiography revealed incomplete revascularization in 26 patients. Six of these 26 had 52 episodes of ST-segment depression during Holter monitoring and myocardial ischemia during exercise testing. Their exercise capacity was significantly lower than that of 10 other patients in whom the results of exercise testing only were positive (heart rate at 0.1 mV ST-segment depression 112 +/- 9 vs 123 +/- 15 beats/min, p less than 0.001). In the other 10 patients with incomplete myocardial revascularization the results of both investigations were negative. The graft patency rate was lower in patients with a positive response to exercise testing than in those with a negative response (52% vs 71%, p less than 0.005). Myocardial revascularization was angiographically complete in 19 patients. In 18 of these 19 patients the findings of both investigations were negative; in 1 patient Holter monitoring revealed episodes of ST-segment elevation suggestive of variant angina. Thus, after CABG for stable angina pectoris the results of Holter monitoring do not improve the sensitivity of exercise testing in identifying patients with angiographically incomplete myocardial revascularization because findings are positive only in patients with low exercise capacity. Both tests fail to show evidence of myocardial ischemia in most patients with angiographically complete myocardial revascularization.

Improved stress test results after multiple coronary grafting

Compared with previous reports that have addressed the issue of preoperative and postoperative stress testing in coronary artery bypass grafting, our results show a 30 percent improvement in the conversion rate from abnormal to normal. In a group of patients with severe coronary artery disease, we have been able to obtain normal stress test results postoperatively. Modern surgical techniques, including the use of blood cardioplegia and other methods of myocardial preservation, have allowed for safety in doing adequate grafting. From our population, we identified a select group of patients (approximately 30 percent) who require 6 or more grafts for complete revascularization. Although our follow-up of 30 months is relatively short, we are encouraged by the results so far. We believe that more than 90 percent of patients can be converted to normal postoperative stress test results after adequate coronary artery bypass grafting.

Different mechanisms for the relief of angina after coronary bypass surgery. Physiological versus anatomical assessment

To determine the physiological effect of coronary artery bypass surgery and the mechanisms for pain relief, 15 patients with exertional angina were studied before and after operation. Before the operation conventional tests included exercise tests (all positive) and coronary angiography (all patients had greater than or equal to 70% stenosis of major vessels). In addition, ambulatory electrocardiographic monitoring during 48 hours detected 92 episodes (greater than or equal to 1 mm) of ST depression. Regional myocardial perfusion was assessed with positron tomography using rubidium-82 (t1/2 78 s) and this showed reversible inhomogeneity with absolute regional reduction of cation uptake after exercise in all 15 patients. After coronary surgery 10 of the 15 patients had (a) no angina, (b) patent grafts (three or more), (c) no evidence of ischaemia during ambulatory monitoring out of hospital, and (d) homogeneous perfusion with reversal of the disturbances in regional myocardial perfusion after exercise. After operation one of the 15 patients had no angina and showed silent infarction in the segment that was previously ischaemic but supplied by a patent graft. All but one of the remaining patients had no angina, patent grafts, but disturbances of regional myocardial perfusion with silent ischaemia on exercise. Two of these patients continued to have asymptomatic and ischaemic episodes of ST depression during ambulatory monitoring out of hospital. This physiological study of regional myocardial perfusion in patients in hospital and in those with ischaemia out of hospital showed that three different mechanisms may account for the relief of pain--improved perfusion, infarction, and silent ischaemia. Silent ischaemia in particular raises puzzling pathophysiological and therapeutic questions that may affect prognosis and the interpretation of clinical trials.

Association between early graft patency and late outcome for patients undergoing artery bypass graft surgery

For a group of 658 patients who received coronary artery bypass graft surgery, we investigated the correlation between the degree of early (6 months) graft patency and recurrence of anginal symptoms, late myocardial infarction, and postoperative coronary-related death. The patients were grouped according to the number of surgically placed grafts, and each group was further subgrouped on the basis of the number of grafts functioning at the early postsurgical follow-up examination. The patients were observed over a period as long as 13 years. The frequency with which angina returned correlated significantly with the degree of patency within each of the groups (one, two, three, or four grafts); patients with a higher percentage of patent grafts experienced longer periods of freedom from angina. On the average, patients with all of their multiple grafts patent experienced at least 7 more years of symptomatic relief than their counterparts with all grafts occluded. Most surprisingly, the rate of the return of angina for those patients who had all grafts patent and were completely revascularized was independent of the number of diseased vessels or the number of grafts placed. The findings for coronary death and postoperative infarction showed similar trends.

Serial exercise testing up to 6 years after coronary bypass surgery: behavior of exercise parameters in groups with different degrees of revascularization determined by postoperative angiography

To evaluate the behavior of exercise parameters in patients with different angiographically defined degrees of revascularization, serial exercise tests were analyzed in 435 patients 1 to 6 years after coronary artery bypass grafting (CABG). All patients had undergone postoperative angiography 2 to 12 months after CABG to determine the degree of revascularization achieved. Revascularization was complete in 182 patients (all significantly stenosed arteries had patent grafts), sufficient in 176 patients (at least the dominant artery supplying the left ventricle had a patent graft) and incomplete in 57 patients (the dominant artery supplying the left ventricle had a closed graft). Twenty patients had all grafts occluded. Exercise tolerance, angina-free exercise tolerance (angina threshold), maximal double product, prevalence of greater than or equal to 0.1 mV exercise-induced S-T segment depression, and the prevalence of the combination of S-T segment depression plus angina pectoris were determined in serial exercise tests (average of 3.0 postoperative exercise tests per patient for a mean follow up of 3.5 years). Patients with complete, sufficient, and incomplete revascularization showed improvement of all exercise parameters for 6, 4, and 1 year after CABG, respectively. Patients with all grafts occluded had improvement of only some exercise parameters. Five years after CABG, exercise tolerance was improved by 24 W (p less than 0.0005) and 21 W (p less than 0.005) in patients with complete and sufficient revascularization, respectively, and not improved in patients with incomplete revascularization or with all grafts occluded. The angiographically determined completeness of revascularization correlates with the extent and the duration of improvement of exercise parameters after CABG.

Use of exercise tests in assessment of the functional result of aortocoronary bypass surgery

The value of an objective exercise test for the assessment of the functional results of aortocoronary bypass was investigated in 19 patients who were studied before and six months after the operation. For positive tests the end point was defined as a net ST segment depression of 0·1 mv 80 ms after the J point of the ECG. For negative tests the end point was 85% of the age-predicted maximal heart rate response. One patient who was not able to attain either of these points after the operation was excluded. In the remaining 18 patients three indices were used in the analysis. First, the heart rate (HR) and the product of heart rate and systolic blood pressure (RPP) were measured at the defined level of ST segment depression during positive exercise tests to yield HR/ST and RPP/ST threshold respectively. Second, the HR and RPP were measured at the end point of the negative tests. Third, the duration of exercise till the end point of the tests was measured. In each patient the duration of the postoperative test was longer than that of the preoperative test. While all the patients had a positive exercise test before the operation, the test was negative in 11 after it. In 10 of these 11 patients the HR and RPP attained at the end point of the postoperative test had increased; the HR and RPP remained unchanged in one patient. Positive tests were still present in seven of the 18 patients. In five of these the HR/ST threshold and RPP/ST threshold were greater after than before operation, and they remained unchanged in two. An improvement in myocardial blood supply after aortocoronary bypass was suggested indirectly by the ability to attain, during exercise, a higher HR and RPP at the end point of the test. The test proved especially valuable in patients who retained a positive exercise test after the operation.

Serial exercise testing after coronary artery bypass surgery

To determine the duration of functional benefit from coronary bypass surgery, 111 patients with angina pectoris were serially evaluated by standard exercise testing prior to and for up to 4 years after surgery. Exercise testing 6 to 18 months after surgery showed greater heart rate-blood pressure product at peak work load, improved work capacity, and less symptomatic and electrocardiographic evidence of ischemia than was demonstrated preoperatively. Twenty patients were tested 37 to 48 months postoperatively and showed improved exercise performance in comparison with preoperative results, but the frequency of positive tests during this period no longer differed. Thus, improved exercise performance appears to persist for at least 4 years after coronary bypass surgery.

Exercise tolerance five years after coronary bypass surgery in relation to clinical and angiographic findings

Exercise on a bicycle ergometer was used to assess symptom-limited working capacity (Wsl) five years after coronary bypass surgery. Ninety-six patients were evaluated with a sitting bicycle test using 10 Watt increments of work load every minute from an initial load of 10 Watt. Ninety-three per cent had less symptoms than before surgery and 32% said they had no angina. Angina was provoked at exercise in 1/31 asymptomatic patients (3%) and in 46/65 (71%) of those with residual symptoms. The Wsl of 50-250 Watt (mean 143 Watt) in a asymptomatic patients was significant higher than 30-220 Watt (mean 105 Watt) performed by patients with residual angina. In 61 patients, exercise tests were performed before, one year and five years after the operation. Average Wsl was significantly higher after one year (127; 36 Watt) than before surgery (90; 23 Watt). but declined significantly until the five-year evaluation (113; 37 Watt). After one year 82% had a higher Wsl than prior to operation compared to 69% five years after surgery. Angiography five years after surgery revealed that 60/76 subjects (79%) had all grafts patent and 16/76 (21%) one or more grafts occluded. In spite of one or more grafts occluded. 2/16 patients (13%) were asymptomatic, whereas 25/60 (42%) with all grafts patent were free from symptoms. Average Wsl was significantly higher in patient with all grafts patent (130; 44 Watt) compared to patients with one or more grafts occluded (102; 33 Watt). It is concluded that although subjective improvement after coronary bypass surgery persisted in about 90% of the patients for five years, bicycle exercise tests show a significant decline of Wsl after the first year, but five years after surgery was still better than before the operation.

Extensive myocardial blood flow distribution through individual coronary artery bypass grafts

The regional myocardial perfusion distribution of coronary artery bypass grafts were studied in 61 patients who received 162 grafts. Selective intragraft instillations of radioactive-labeled macroaggregated albumin particles were used to study perfusion. The extent of individual graft perfusion was assessed in 100 patent grafts. Regional myocardial blood flow distribution was similar to the blood flow distribution of the native vessel receiving the graft in 64 of 100 grafts and less than that expected of the native vessel in 12 grafts. However, 24 grafts demonstrated a blood flow distribution pattern which extended beyond the normal distribution expected of the native vessel receiving the graft. This extensive perfusion could be attributed to collateral vessels or retrograde flow. A high incidence of both graft and native vessel occlusion was found in areas receiving blood from these distant grafts with extensive distributions (16/24), and left ventricular wall motion was preserved or significantly improved postoperatively in 28/31 segments in such areas. When comparing angiographic and scintigraphic methods of evaluating myocardial perfusion, the angiogram underestimated the full extent of graft blood flow distribution in 13 of 24 instances (54 percent).

Functional evaluation of aortocoronary bypass surgery by exercise testing

Exercise stress test was performed prior to and after aortocoronary bypass surgery in 91 male patients in an attempt to quantitate the change of physical capacity after operation and to correlate this to clinical improvement and late shunt angiography. The mean maximal work load was significantly higher after than prior to surgery in all groups. In average the maximal work load increased 65%. No difference was found between patients who were operated on for stable angina pectoris and those with unstable angina or impending myocardial infarction. Patients, who subjectively were without symptoms or much better after surgery, had a higher maximal work load after operation than those who were subjectively less improved or worse. In a sub-group of patients the maximal oxygen consumption was calculated in per cent of normal values for the age. The mean maximal oxygen consumption increased from 59% prior to surgery to 76% of normal values after surgery.

Radionuclide assessment of aortocoronary bypass surgery

Rest and exercise thallium 201 myocardial scintigraphy and multiple gated radionuclide angiography were correlated with the results of clinical status, exercise electrocardiography, coronary arteriography, and contrast left ventriculography in a series of 12 prospectively studied consecutive patients before and after aortocoronary bypass operation. Patients were divided into two groups based on a comparison between preoperative and postoperative 201T1 scintigrams. Group 1 (6 patients) demonstrated improved or normal postoperative perfusion scintigrams and excellent correlation between the site of a patent graft and the improvement in myocardial perfusion on the postoperative exercise scintigrams. Regional wall motion remained normal in 3 patients and improved in 3. In Group 2 (6 patients) the postoperative 201T1 scintigrams were unchanged or worse. Each patient demonstrated graft occlusion, graft stenosis, distal disease, or a perioperative myocardial infarction. No improvement in regional wall motion occurred in 4 of these 6 patients. Neither the symptomatic response to aortocoronary bypass operation nor the response to exercise testing successfully predicted graft patency.

Long-term results of myocardial revascularization

During 1970 to 1977, among 1,733 patients who underwent isolated coronary bypass grafting, the operative mortality was 2.5 percent. Actuarial 5 year survival is 88.1 percent. At an average follow-up of 46 months (range 13 to 108), 90 percent of patients remain angina-free or with symptomatic improvement. The 5 year survival rate of patients with single vessel coronary artery disease is 97.9 percent. In patients with multivessel disease, operative survival appears to be favorably influenced by the presence of normal preoperative ventricular function. Late survival is significantly better in patients with multivessel disease with normal preoperative ventricular function or with complete revascularization. Risk of perioperative myocardial infarction has been appreciably reduced by the introduction of cold potassium chloride cardioplegia. Late myocardial infarction has occurred at an average annual risk of 1.46 percent. These data show that long-term survival and a small incidence of late myocardial infarction after myocardial revascularization are more likely in patients who undergo complete revascularization before significant left ventricular myocardial damage has occurred.

Reversal of exertional hypotension after coronary bypass grafting

A decrease in systolic blood pressure that occurs with treadmill exercise testing may be a sign of reversible ischemic left ventricular dysfunction. To test this hypothesis, we examined retrospectively the postoperative treadmill responses of 37 patients who had exertional hypotension (end exercise systolic blood pressure less than or equal to initial preexercise levels) before coronary arterial bypass grafting. This group of 37 patients was characterized preoperatively by an abnormal exercise electrocardiogram (36 patients), multiple vessel occlusive disease (36 patients) and a normal ejection fraction at rest (32 patients). Postoperative exercise tests showed improvement in hemodynamic and electrocardiographic changes with reversal of exertional hypotension (33 patients), and conversion to a normal exercise electrocardiogram (29 patients). Coronary bypass surgery can be expected to reverse exertional hypotension in patients with symptomatic angina pectoris and evidence of ischemia in the exercise electrocardiogram.

Persistence of improved exercise tolerance and degree of revascularization after coronary bypass surgery. A prospective randomized study

Exercise tolerance was repeatedly determined over a 2-year period in a series of 100 patients with coronary heart disease randomly allocated for medical therapy and coronary bypass surgery. The surgical group had a consistently better exercise tolerance than the medical group during the whole follow-up. Completeness of the revascularization, assessed by repeated graft and native vessel angiography, resulted in a marked improvement whereas incompletely revascularized patients exhibited only a marginal improvement which, nevertheless, to some degree exceeded the result of medical management alone. It is concluded that coronary bypass surgery and medical therapy, when indicated, result in markedly better exercise tolerance than medical management alone. This improvement persists up two years after the operation and is largely dependent on the completeness of the revascularization.

Aortocoronary bypass grafting in the management of patients with coronary artery disease

There is widespread agreement that aortocoronary bypass grafting generally lessens the symptoms and functional limitations of patients with angina pectoris. Evidence for prolongation of life or prevention of myocardial infarction, arrhythmias and ventricular dysfunction is inconclusive. Harmful effects associated with surgical management of coronary artery disease can be documented in terms of operative mortality, perioperative myocardial infarction, graft occlusion and progression of occlusive disease in the native circulation. In this review of published experience, the accomplishments and the limitations of myocardial revascularization are considered in various clinical settings. Critical assessment of evolving information leads to the conclusion that widespread application of this procedure beyond the alleviation of symptoms refractory to medical therapy is not justified by present data.

Thallium-201 myocardial scintigraphy in patients with triple-vessel disease and ischemic exercise stress tests

Thirty patients with triple-vessel coronary artery disease proven by angiography, symptomatic angina and a positive ECG stress test were evaluated with thallium-201 (201TI) scintigraphy. Twenty patients also had aortocoronary saphenous vein bypass surgery; 15 of them had repeat noninvasive evaluation. Seventy percent of these patients showed ischemia by 201TI scintigraphy, of which one-half returned to normal after surgery. Postoperative reversion of the ECG stress test together with 201TI stress/reperfusion imaging correlated well with the completeness of surgical revascularization. We could not explain the prevalence (80%) of infarcts detected by 201TI in this group, of which 76% could be anatomically correlated to epicardial scars. The positivity of infarcts by 201TI exceeded that predicted by previous history of infarction, Q waves on resting ECG or ventriculographic akinesis. These observations suggest that 201TI scintigraphy is a useful noninvasive tool in the follow-up and understanding of patients with coronary heart disease. These conclusions also support the concept that 201TI stress imaging need not have the identical connotation as the ECG stress test.

A multivariate approach for interpreting treadmill exercise tests in coronary artery disease

To determine the value of a multivariate approach for the analysis of the treadmill exercise tolerance test (ETT), 237 patients referred for evaluation of chest pain who underwent a standard Bruce protocol ETT and coronary arteriography were studied. Predictive value of a positive ETT was 0.78 (43/55) using 1.0--1.9 mm ST segment depression criterion, 0.97 (59/61) using greater than or equal to 2.0 mm ST segment depression. When the 1.0--1.9 mm ST criterion was combined with peak systolic blood pressure-heart rate product (double product) less than or smaller than 23,000, exercise duration less than 6 minutes, and ST depression for greater than 3 minutes into recovery, predictive value improved to 0.89 in 18 patients with any two of the above. Predictive value for multivessel disease was also improved using non-ST criteria. Predictive value of a negative ETT for absence of coronary artery disease was 0.60 (29/48), and was 0.86 (12/14) if double product was greater than or equal to 30,000. Presence of chest pain during ETT did not improve predictive value of any type of test. Digitalis ingestion in 33 patients was not associated with decreased predictive value of a positive test. These data suggest that the predictive value of both positive and negative ETT in a symptomatic population can be improved with a multivariate approach.