Effects of coronary artery bypass grafting on resting and exercise hemodynamics in patients with stable angina pectoris: a prospective, randomized study

Enhanced regional left ventricular function after distant coronary bypass by means of improved collateral blood flow

To determine whether coronary artery bypass surgery can improve function in left ventricular regions not amenable to direct revascularization, 24 patients with multivessel coronary artery disease were studied by radionuclide angiography and coronary arteriography before and 6 months after coronary artery bypass surgery. All had proximal stenosis of the left circumflex artery or a major obtuse marginal branch. Left ventricular regional function was assessed by dividing the left ventricular region of interest into 20 sectors; the 8 sectors corresponding to the posterolateral free wall were used to assess function in the left circumflex artery distribution. Change in function in the left anterior descending territory was not analyzed because of the non-specific septal hypokinesia that develops postoperatively. For the total group, coronary artery bypass surgery significantly increased both global left ventricular ejection fraction during exercise (43 +/- 13% to 50 +/- 14%, p less than 0.001) and the change in ejection fraction from rest to exercise (-7 +/- 10% to 0 +/- 6%, p less than 0.001). Such improvement was observed in 9 of 10 patients with all stenoses bypassed, and to an equivalent degree in 9 of 10 patients in whom the left circumflex artery either could not be bypassed or the bypass graft was occluded (but bypass grafts to other coronary arteries were patent). Similarly, regional ejection fraction in posterolateral segments during exercise also increased comparably after operation in patients with a patent (from 57 +/- 18% to 70 +/- 19%, p less than 0.001) or nonpatent (from 51 +/- 14% to 68 +/- 14%, p less than 0.001) left circumflex graft.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of coronary artery bypass grafting on left ventricular systolic function at rest: evidence for preoperative subclinical myocardial ischemia

Successful coronary artery bypass grafting (CABG) improves exercise-induced left ventricular (LV) dysfunction in patients with coronary artery disease (CAD), but its potential for improving resting LV function remains controversial. To assess the influence of CABG on LV function at rest, 31 CAD patients without previous myocardial infarction were studied before and 6 months after CABG by radionuclide angiography after all cardiac medicines were withdrawn. No patient had angina or ischemic electrocardiographic changes at rest. In 27 patients with patent bypass grafts, CABG significantly increased LV ejection fraction during exercise (47 +/- 11% before to 63 +/- 9% after operation, p less than 0.001), indicating reduction in exercise-induced LV ischemia. Moreover, LV ejection fraction at rest also increased (55 +/- 9 to 60 +/- 8%, p less than 0.001), with 20 of 27 patients manifesting an increase compared with preoperative values. Eleven of these 20 patients had apparently normal LV function at rest (ejection fraction and regional wall motion) before CABG. LV regional ejection fraction was computed by dividing the LV region of interest into 20 sectors. Regional analysis indicated that improved ejection fraction at rest after CABG occurred in regions developing ischemia during exercise before CABG. In 4 patients with occluded grafts, the ejection fraction at rest was unchanged by CABG globally (59 +/- 8 to 58 +/- 9%, difference not significant) and regionally. Thus, LV global and regional function at rest improved after successful CABG, even in patients with normal global LV ejection fraction and no visually detectable wall motion abnormality before surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Sustained efficacy of percutaneous transluminal coronary angioplasty

To determine whether the immediate efficacy of percutaneous transluminal coronary angioplasty (PTCA) is sustained, follow-up data were obtained in 183 patients who had undergone PTCA at least 1 year earlier. The duration of follow-up ranged from 1 to 5 years. Subjective clinical information was obtained in each patient and objective functional information, determined by exercise stress testing, was obtained in 91. PTCA was initially successful in 141 patients (79%). Of the 42 patients in whom PTCA was unsuccessful, 26 underwent coronary artery bypass graft surgery (CABG), while 16 were maintained on medical therapy (MED). When compared to the MED patients at time of follow-up, successful PTCA patients experienced less angina (13% vs 47%; p = 0.003), used less nitroglycerin (25% vs 73%, p = 0.003), were hospitalized less often for chest pain (8% vs 31%; p = 0.02), and subjectively felt their condition had improved (96% vs 20%; p less than 0.001). Furthermore, during exercise testing, the prevalence of angina was reduced (9% vs 43%; p = 0.05), and exercise duration was greater (8.2 minutes vs 5.8 minutes, p = 0.05) among PTCA patients. There were no significant differences in the incidence of subsequent myocardial infarction, mortality, or need for coronary artery bypass surgery. For these variables, no differences were seen between the CABG and PTCA groups. Thus, successful PTCA results in long-term relief of subjective and objective manifestations of myocardial ischemia, superior to that of medical therapy and comparable to CABG.

Comparative long-term effects of coronary artery bypass graft surgery and percutaneous transluminal coronary angioplasty on regional coronary flow reserve

To evaluate the relative long-term improvement in coronary artery hemodynamics after revascularization by coronary artery bypass graft surgery (CABG) or percutaneous transluminal coronary angioplasty (PTCA), regional coronary flow reserve (CFR) was measured, by digital computer analysis of 35 mm cine film, in 50 men undergoing cardiac catheterization. CFR (mean +/- SEM) in 12 atherosclerotic arteries before revascularization was 1.02 +/- 0.05. Mean CFR in 29 normal arteries of men with normal coronary arteriograms was significantly higher (2.59 +/- 0.11) than that in 16 atherosclerotic arteries of patients revascularized by CABG (2.02 +/- 0.17, p less than .01) or in 14 atherosclerotic arteries of those revascularized by PTCA (1.97 +/- 0.12, p less than .01). No difference in CFR between the CABG and PTCA groups was found and variables known to influence CFR were similar between groups. Equivalent and significant long-term improvement in coronary artery hemodynamics is provided by CABG or PTCA. We postulate that the difference in CFR in the men with normal arteries and those who underwent revascularization was related to the effects of the general atherosclerotic process, which remain despite successful treatment by these techniques.

Left ventricular systolic and diastolic function in coronary artery disease: effects of revascularization on exercise-induced ischemia

Left ventricular systolic and diastolic function were studied before and after surgical revascularization in a group of 24 patients with stable angina who all had an excellent clinical response to surgery. With use of micromanometer left ventricular pressure measurements and ventricular volumes, calculated from biplane cineangiograms, left ventricular function at rest and during exercise before and after surgery was compared. Before surgery all patients had exercise-induced ischemia with new asynergy, a fall in ejection fraction from 57% to 49% (p less than .001), and a rise in left ventricular end-diastolic pressure from 23 to 37 mm Hg (p less than .001). Postoperative exercise resulted in no new asynergy and ejection fraction rose from 59% to 61% (p less than .05). Left ventricular end-diastolic pressure still rose from 17 to 25 mm Hg (p less than .01). Left ventricular pressure decay during exercise was greatly improved after revascularization and allowed maintenance of reduced early diastolic pressures. The early diastolic pressure nadir before surgery rose from 9 to 21 mm Hg (p less than .001); the postoperative nadir was 5 mm Hg at rest and 6 mm Hg during exercise. All patients had an upward shift in the diastolic pressure-volume relationship during preoperative exercise. After revascularization there was no upward shift in some patients and a much smaller shift in others. The postoperative increase in left ventricular end-diastolic pressure was due to increased end-diastolic volume, not altered compliance. There was an increase in mean right atrial pressure during exercise either before (6 to 11 mm Hg) or after surgery (4 to 10 mm Hg). These increases were quite variable, suggesting no consistent role of pericardial restraint during exercise. Early diastolic peak filling rate during exercise was greater after surgery (1260 vs 950 ml/sec, p less than .001). In fact, during postoperative exercise early diastolic filling rates were greater than normal, reflecting the persistence of abnormally high atrial pressures for filling. As at preoperative study, late diastolic filling during exercise was restricted after revascularization when compared with that in a control group. Postoperatively patients undergoing bypass procedures with a good clinical result showed significantly improved left ventricular diastolic and systolic function. Persistent elevation of end-diastolic and atrial pressures and other abnormalities of diastolic function may reflect chronic structural changes and need to be taken into account when evaluating patients after bypass surgery.

Early and long-term results of coronary artery bypass grafting with severely depressed left ventricular performance

The effects of coronary artery bypass grafting (CABG) on ventricular performance and long-term clinical status were studied in 18 consecutive patients with disabling angina pectoris and severely depressed left ventricular (LV) performance (ejection fraction [EF] 27 +/- 9%). All patients survived CABG, although 1 patient had a perioperative myocardial infarction. There was no change in LVEF at rest, 29 +/- 12%, in the other 17 patients. However, LVEF during peak exercise increased from 22 +/- 7% to 27 +/- 14% (p less than 0.05). The 17 patients were separated into 2 groups: those who increased their peak exercise LVEF by at least 10% (group A, 8 patients) and those who increased it by less than 10% (group B, 9 patients). Preoperatively, patients in group A had a higher LVEF at rest (p less than 0.001) and smaller end-systolic and end-diastolic volumes at rest (p less than 0.001) and during exercise (p less than 0.005). Preoperatively, the LVEF in group A decreased with exercise, from 36 +/- 4% to 27 +/- 5% (p less than 0.01), but was unchanged in group B (19 +/- 3% vs 17 +/- 4%, difference not significant). After CABG, patients in group A had a smaller increase in end-systolic volume with exercise than those in group B (13 +/- 7 vs 34 +/- 22 ml/m2, p less than 0.05), but the changes in end-diastolic volume with exercise were not significantly different. At 27 +/- 5 months after CABG, 5 of 8 patients in group A were asymptomatic.(ABSTRACT TRUNCATED AT 250 WORDS)

Mean systolic ejection rate after aortocoronary bypass graft surgery

In 62 patients with coronary artery disease who underwent aortocoronary bypass graft surgery, we measured the mean systolic ejection rate invasively at rest and during upright exercise before and several months after operation. After bypass surgery, mean systolic ejection rate did not show any change at either supine or sitting rest and at submaximal exercise levels of walking on a treadmill. At maximal exercise, only patients with complete revascularization showed a significant increase in heart rate from 105 to 147 (+40%) and mean systolic ejection rate from 339 ml/sec to 404 ml/sec (+19%, P less than 0.001). Patients with incomplete revascularization did not show a substantial change in these variables. Beta-blocker withdrawal did not affect the result significantly.

Effect of left ventricular aneurysmectomy on exercise performance

We performed pre- and post-operative exercise testing on 12 patients with coronary artery bypass surgery and ventricular aneurysmectomy and 2 patients with ventricular aneurysmectomy alone. Most patients showed better exercise performance, higher double product, better work capacity and were able to exercise longer. Two patients who had ventricular aneurysmectomy alone showed similar changes. Most patients showed improved New York Heart Association functional classification and exercise performance after surgery.

Changes in cardiac functional capacity after coronary bypass surgery in relation to adequacy of revascularization

Seventy patients having aortocoronary vein bypass grafting surgery for angina pectoris underwent preoperative invasive exercise testing to symptom limits and again 6 to 14 months postoperatively. Cardiac output was measured using the direct Fick principle. Postoperatively at maximal exercise, there was a 3.11 liters/min (p less than 0.0001) increase in cardiac output in men (n = 61) and a 2.04 liters/min (p less than 0.01) increase in women (n = 9). Patients with complete revascularization showed a significantly greater improvement in cardiac output postoperatively than did those with incomplete revascularization (26 versus 6%, p less than 0.0001). The major reason for the increased maximal cardiac output was a marked increase in heart rate while stroke volume was maintained at the same preoperative level. These findings were true irrespective of preoperative use of beta-adrenergic blocking drugs.

Low-level exercise testing before and after coronary artery bypass surgery

Heart rate and blood pressure responses to low-level exercise tests in patients immediately before and after coronary artery bypass graft surgery lack sufficient documentation. This study documents heart rate, blood pressure, electrocardiographic responses and symptoms during low-level treadmill tests (LLTT) of 19 patients in two subgroups (A and B) before surgery, and again the day before hospital discharge. Preoperatively, the most common reason for stopping the treadmill test early was onset of angina. Postoperatively, patients stopped due to fatigue (4), dyspnea (6), and dizziness (2). Mean resting heart rate responses increased 37% in group A (n = 9) and 40% in group B (n = 10) from the preoperative to postoperative test. Mean postoperative resting pressure rate product responses increased 16% in group A and 38% in group B compared to preoperative values. Mean resting systolic blood pressure responses were 15% lower postoperatively for group A. This LLTT proved to be a clinically feasible tool which provided objective information about the patient's readiness for discharge and exercise prescription.

Late exercise test results from a prospective randomized study of bypass surgery for stable angina

A prospective randomized study comparing coronary bypass surgery (group 1, 51 patients) to drug therapy (group 2, 49 patients) was initiated in 1981. Supine graded exercise testing (SGXT) was performed initially, at 6 months, and annually with a bicycle ergometer. The presence or absence of ischemic ST segment changes (positive or negative SGXT) and chest pain were recorded. Initially, 63% of all patients had positive SGXT. For group 2, the frequency of positive SGXT results did not change significantly at 6 months (58%) or at 5 years (52%). At 6 months the number of patients without chest pain increased in group 1 compared with group 2 (28/41 vs 13/41, respectively; p less than .002), but there was no difference in the frequency of positive SGXT results (20/41 vs 24/41, respectively; p = NS). This occurred because a majority of the group 1 patients with positive SGXT no longer had associated chest pain (group 1, 11/20, group 2, 3/24; p less than .007). This response was associated with incomplete revascularization in eight of these 11 group 1 patients and may result from "silent ischemia." At 5 years, no significant difference existed in the incidence of positive SGXT (group 1, 10/32 vs group 2, 12/23; p = NS), but group 1 patients continued to have a reduction (although not statistically significant) in the number of patients without chest pain (group 1, 19/32 vs group 2, 7/23). The incidences of death and myocardial infarction were not significantly different between groups. Fewer episodes of unstable angia occurred in group 1 (10/51 vs 19/49; p less than .05). The prognosis of group 1 patients with positive SGXT and no chest pain and incomplete revascularization was not different from that of the entire group.

Effects of coronary artery bypass grafting on left ventricular function assessed by multiple gated ventricular scintigraphy

The effect of coronary artery bypass grafting on global left ventricular ejection fraction and regional contraction was studied in 56 consecutive patients with chronic stable angina pectoris by means of multiple gated ventricular scintigraphy at rest and during dynamic supine exercise before and six weeks after myocardial revascularisation. Before operation, exercise induced a significant fall in ejection fraction and regional wall motion score. Six weeks after operation 52 patients were symptomless. Resting ejection fraction and regional wall motion score were unchanged but during exercise ejection fraction increased significantly, and the previous exercise induced regional wall motion abnormalities were abolished. All four patients with persisting angina showed the same pattern as before operation, with a fall in left ventricular ejection fraction and regional wall motion score during exercise. Multiple gated ventricular scintigraphy affords a safe, objective, reproducible, and non-invasive means of assessing serial ventricular function at rest and during exercise in patients with ischaemic heart disease. The technique confirms that coronary bypass surgery abolishes exercise induced abnormalities of left ventricular function, but has no influence on resting function.

Early assessment of rest and exercise left ventricular function following coronary artery surgery

Radionuclide assessment of rest and exercise left ventricular function was performed in 14 patients before, eight days after, and three months after coronary artery bypass grafting (CABG). Resting function was unaltered after operation, although mild increases in heart rate and end-diastolic volume were observed on the eighth postoperative day. In contrast, exercise function was significantly improved at both postoperative time periods. Exercise ejection fraction was 0.54 +/- 0.10 before operation, 0.73 +/- 0.12 at eight days, and 0.64 +/- 0.13 at three months. Before CABG, the exercise-induced increase in stroke volume was achieved by an increase in end-diastolic volume, whereas eight days after CABG this increase was achieved by an increase in contractility (systolic blood pressure/end-systolic volume). By three months, both contractility and end-diastolic volume increased with exercise. Thus, improvement in left ventricular function during exercise can be documented as early as eight days after coronary revascularization. This change may be less pronounced after three months of convalescence, but considerable improvement in ventricular function persists compared to preoperative assessment.

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.

Selection of angina-free patients with severe left ventricular dysfunction for myocardial revascularization

Stress thallium-201 myocardial imaging was used in two angina-free patients with severe congestive heart failure to identify clinically silent areas of ischemic myocardium and to distinguish between scar and reversibly ischemic myocardium as a cause for akinesia of left ventricular wall segments. Subsequent myocardial revascularization in these patients led to considerable improvement in their clinical state and findings in postoperative nuclear scans. Thus, stress myocardial imaging may be useful in selecting patients with severe left ventricular failure but no angina pectoris for myocardial revascularization.

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.

Effect of coronary arterial bypass surgery on exercise-induced ventricular arrhythmias. Long-term follow-up of a prospective randomized study

The effect of coronary arterial bypass surgery on exercise-induced ventricular arrhythmias and their relation to sudden death was examined in 102 patients with stable angina pectoris randomly assigned to medical and surgical therapy (54 and 48 patients, respectively). Symptom-limited treadmill tests were performed at entry and at 1 and 5 years. The surgical group demonstrated significant improvement in exercise performance at 1 year compared with the medical group, and at 5 years exercise-induced ischemia as evidenced by S-T depression and exertional angina remained substantially decreased in the surgical group with little change in the medical group. However, the frequency and severity of exercise-induced ventricular arrhythmias in each group remained unchanged at 1 and 5 years from those at entry. Similar results were obtained from an evaluation of ventricular arrhythmias in the electrocardiogram at rest. With the exception of exercise-induced ventricular tachycardia and fibrillation, no relation was found between ventricular arrhythmias and sudden death. Coronary bypass grafting does not decrease the frequency or severity of exercise-induced or resting ventricular arrhythmias. In patients with stable angina pectoris, with the exception of ventricular tachycardia and fibrillation, exercise-induced ventricular arrhythmias are poor predictors of sudden death. The data suggest that exercise-induced ventricular arrhythmias may not be related to ischemia but to other effects of exercise such as cardiac stimulation by catecholamines or other factors.

Thallium-201 myocardial imaging in assessment of results of aortocoronary bypass surgery

Thirty-six patients were assessed by thallium-201 myocardial imaging before and after aortocoronary bypass operations and the results were compared with evaluation based on symptomatic assessment, exercise testing, and electrocardiography. After operation, the majority of patients were free from symptoms or symptomatically improved with increased exercise duration. Perioperative myocardial damage was shown in eight patients and myocardial ischaemia in 15 patients when assessed by thallium imaging during exercise. Thallium imaging proved more sensitive than electrocardiography in the demonstration of perioperative infarction and in the detection of postoperative ischaemia. Exercise electrocardiography may be misleading after aortocoronary bypass operations. Thallium imaging offers a simple, objective evaluation of the results of revascularisation procedures, throws light on the mechanisms of relief of angina by operation, and helps in the assessment of the patient whose progress is unsatisfactory after operation.

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.

Traumatic pulmonary artery--left atrial fistula: an unusual case of cyanosis in an adult

Eighteen months after sustaining a stab wound to the left upper chest, a 59-year-old man presented with cyanosis and extertional dyspnea. Arterial desaturation due to a central 22 per cent right-to-left shunt was present. A selective pulmonary arteriogram demonstrated a fistula between the main pulmonary artery and the left atrium. At operation the fistula was closed. A laceration of the pulmonic valve and healed pericarditis were present. Marked symptomatic improvement followed the operation, but a murmur of pulmonic valvular regurgitation persisted. The fistula and laceration of the pulmonic valve were probably traumatic in origin.

The value of exercise stress testing in predicting benefit from aorto coronary bypass surgery

A total of 142 saphenous vein bypass patients who underwent pre- and postoperative treadmill stress tests were analyzed. The double product at the onset of ischemia improved in 15 of 25 females (68%) and 67 of 117 males (58%). In patients with a history of preoperative angina, 103 of 132 (78%) were relieved after operation, but only 81 of 132 (61%) improved their double product. In those with preoperative angina during treadmill stress testing, 48 of 79 (61%) improved. In patients without preoperative angina on treadmill stress testing, 40 of 65 (62%) improved their double product. When ST depression developed at a workload of 4 METS on the preoperative treadmill stress test, 54 of 87 (62%) improved. When ST depression developed at 6 METS, 20 of 34 (58%) improved their double product at the point of ischemia.

The patient's sex, angina during treadmill stress testing, and the workload associated with ischemia did not help identify those who would benefit from bypass surgery. Treadmill stress testing does demonstrate the disparity be tween symptomatic and functional improvement and provides an important parameter for evaluation of aortocoronary bypass.

Haemodynamics during maximal exercise after coronary bypass surgery

Fifty patients underwent an objective measurement of physical working capacity by means of a multistage test of maximally tolerated exertion before and after coronary bypass surgery; 29 patients also had haemodynamic measurements during maximal exercise before and after coronary bypass surgery. The patients were divided into 3 groups according to the degree of revascularisation: adequate (n = 20), partial (n = 17), or none (n = 13). Adequate revascularisation induces a large increase in physical working capacity because of an increased maximal heart rate and maximal cardiac output; stroke volume during maximal exercise and ejection fraction at rest were not modified, suggesting no major changes in left ventricular function. After unsuccessful coronary bypass surgery, the physical working capacity was unchanged despite an increased maximal heart rate; maximal cardiac output was unchanged and stroke volume during maximal exercise was significantly lower. These undesirable results are often associated with perioperative myocardial infarction and are attended by a decreased ejection fraction at rest; these data suggest an impaired left ventricular function after unsuccessful coronary bypass surgery. The results of partial revascularisation are intermediate but appear to be determined by the incidence of partial graft failure which is also often associated with perioperative myocardial infarction. From individual changes in data collected during maximal exercise testing, it is often impossible to predict the degree of revascularisation.

Thallium-201 myocardial imaging before and after coronary revascularization: assessment of regional myocardial blood flow and graft patency

Twenty patients underwent myocardial imaging with Thallium-201 (201Tl) before and subsequent to coronary artery bypass grafting. All patients had rest and maximal treadmill exercise imaging postoperatively. Eleven of the 20 patients had rest and exercise 201Tl images preoperatively; 9/20 only had rest imaging preoperatively. Postoperative regional exercise perfusion was improved in seven of the 11 patients who had preoperative exercise images, and was associated with regional graft patency in each case. Thirteen of 20 patients showed no new defect with postoperative exercise imaging. The remaining seven patients developed or had an increased defect with exercise. The patients with no new perfusion defects during postoperative study has 26/30 grafts patent (87%). Patients developing a new perfusion defect with exercise had fewer grafts patent (7 of 13 [54%]; P less than 0.03). In these seven cases, a new exercise-induced defect was associated with regional graft closure or residual nonoperated disease. Knowledge of the preoperative coronary anatomy allowed the distinction between ungrafted areas and regional graft dysfunction. We conclude that preoperative and postoperative 201Tl imaging may noninvasively predict graft closure and/or improved regional perfusion with patent grafts.

Accuracy of treadmill testing in assessment of direct myocardial revascularization

Near-maximal treadmill exercise tests (TET) performed at the time of coronary arteriography and bypass graft visualization an average of 13 months after direct myocardial revascularization were analyzed in 217 consecutive patients to assess the accuracy of the TET in predicting completeness of revascularization. TET results were correlated with bypass patency and extent of revascularization. Although conversion of a TET from an abnormal to a normal test or relief of TET-induced angina following surgery is closely correlated with bypass graft patency, the high incidence of normal exercise tests in the presence of residual coronary disease limits their usefulness in the individual postoperative patient in estimating the completeness of revascularization.