Ischemic myocardial injury during coronary artery surgery

Improved outcome of coronary arterial bypass surgery in a small center after identification and modification of peroperative risk factors

By uni- and multivariate analysis, predictors of surgical mortality and postoperative angina were identified retrospectively in 189 patients having had coronary arterial bypass surgery over the period 1978-1984. After modification of these risk factors, surgical outcome was followed up in another 178 patients undergoing operation from 1985 to 1987. The surgical mortality of 7% in the first series was closely associated with postoperative signs of acute myocardial injury. All deaths occurred in patients having at least 3 out of 5 pre- and peroperative risk factors: triple vessel/left main coronary arterial disease, incomplete revascularization, no propranolol treatment, Bretschneider cardioplegia other than "HTP"-solution with blood preperfusion and perioperative vasopressor support. The procedures of cardiac protection were modified. St Thomas multidose potassium cardioplegia and general hypothermia were introduced, perioperative propranolol treatment increased and bypass time decreased. Improved cardiac protection with this regime was seen in the patients operated in 1985-1987 when compared with the first series with regard to perioperative vasopressor support (8 vs 33%, P less than 0.001), spontaneous operative defibrillation (72 vs 52%, P less than 0.001), postoperative arrhythmias (20 vs 43%, P less than 0.001), peak levels of serum enzymes (P less than 0.001), myocardial infarction (7 vs 19%, P less than 0.001) and hospital mortality (2 vs 7%, P less than 0.05). The incidence of freedom from symptoms at 3 months was also increased in the patients undergoing operation from 1985 to 1987 (72 vs 61%, P less than 0.05). Even small centers can improve their surgical outcome by carefully analysing their own results and modifying the identified risk factors.

Current status of cardiac surgery: a 40 year review

Cardiac surgery has undergone dramatic advancements during the past 3 decades. The introduction of cardiopulmonary bypass and cardioplegic arrest ushered in the true era of open heart surgery. Bioprostheses and mechanical valves as well as techniques for valve reconstruction permit routine repair or replacement of stenotic and regurgitant native valves. Progress in the disciplines of mechanical and electrical engineering has led to the development of pocket watch-sized, physiologically responsive pacemakers as well as a variety of circulatory assist devices that include the intraaortic balloon pump, ventricular assist device and total artificial heart. The synthesis of cardiotonic and vasoactive drugs and advancements in anesthetic management, postoperative monitoring and nursing care greatly facilitate perioperative patient management. This summary of state of the art cardiac surgery begins with a brief historical background followed by a review of recent advances in six main categories: coronary artery disease, acquired valvular heart disease, congenital cardiac disease, cardiac transplantation, myocardial preservation and mechanical circulatory assistance. In conducting the review of recent literature, particular attention was directed to large clinical series that document the results of contemporary surgical procedures, novel therapeutic approaches to current clinical problems and unresolved controversies in the field of cardiac surgery. The abundance of surgical literature and constraints on the length of this article do not permit an exhaustive review. Apologies are extended to clinicians and laboratory investigators whose important contributions to the understanding and treatment of cardiac disease are not included herein.

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.

Use of survival analysis to determine the clinical significance of new Q waves after coronary bypass surgery

There are few data on the long-term effects of new Q waves on survival and morbidity after coronary bypass graft surgery (CABG). We followed 1340 patients who underwent CABG in 1978 at 10 hospitals participating in the Coronary Artery Surgery Study (CASS). The incidence of perioperative Q-wave infarction was 4.76% (range 0.0-10.3% by hospital). The rate of infarction was higher in patients who had an increased left ventricular end-diastolic pressure or cardiomegaly on the preoperative chest radiograph. Patients who received more grafts or who had longer cardiopulmonary bypass time were also at higher risk of infarction. In a stepwise discriminant analysis of 44 clinical, angiographic and surgical variables, cardiopulmonary bypass time, topical cardiac hypothermia and cardiomegaly entered the stepwise selection of variables. Long-term survival was adversely affected by the appearance of new postoperative Q waves. The hospital mortality was 9.7% in the 62 patients who had new postoperative Q waves and 1.0% in the 1278 patients who did not (p less than 0.001); the 3-year cumulative survival rates were 85% and 95%, respectively (p less than 0.001). In patients who survived to hospital discharge, the presence of new postoperative Q waves did not adversely affect 3-year survival (94% and 96%, respectively). The survival rates were worse in patients who had a history of infarction or who had impaired left ventricular function preoperatively. The number of readmissions to hospital after CABG among the patients who had a transmural perioperative infarction was similar to to that among patients who did not. We conclude that the appearance of new Q waves after CABG adversely affects survival. The major impact on mortality occurs before hospital discharge. Patients who are destined to have a perioperative infarct cannot be predicted from commonly measured preoperative and angiographic variables.

Postoperative monitoring of myocardial oxygen tension: experience in 51 coronary artery bypass patients

Following a preliminary feasibility report, polarographic monitoring of myocardial tissue O2 tension (Pmo2) in 51 coronary bypass patients has been accomplished. In this context, the influence of rapid atrial pacing (RAP), O2 inhalation, and intra-aortic balloon assistance (IAB) was statistically analyzed using Wilcoxon sign-rank and Student's t-tests. Electrodes were implanted in revascularized and nonrevascularized areas for comparison (24.0 +/- 1.1; and 26.3 +/- 1.8 mmHg Pmo2, p, not significant). Increasing myocardial O2 demand with RAP caused a 6% PmO2 drop (p less than 0.01). A 70% O2 inhalation increased Pmo2 by 30% (p less than 0.01). In 5 cases the benefit of IAB was confirmed by a 41% increase in Pmo2 (p = 0.02). These data support the clinical usefulness of polarographic Pmo2 as a measure of regional myocardial oxygenation. In addition to early recognition of intraoperative or postoperative graft failure previously reported, the efficacy of various therapeutic interventions can be more precisely determined.

Serum CK-MB activity during and after aortocoronary bypass surgery

Frequent serum sampling of CK-MB and total CK levels was carried out in 100 patients during and up to 48 hours following aortocoronary bypass surgery. Using an ion exchange chromatography method for CK-MB determination, significantly higher serum CK-MB levels (peak 46.1 +/- 5.2 cf. 31.3 +/- 2.2 u/L), but not total CK levels were present 6 to 16 hours postoperatively in those with new Q waves in the ECG. Serum levels of CK-MB in those patients with uncomplicated surgery were defined. New post-operative Q waves were seen in only one half of cases with frankly abnormal CK-MB curves and seriously underestimated the incidence of perioperative infarction. Peak levels of CK-MB in patients with new Q waves occurred within 16 hours of surgery suggesting that infarction is usually an intraoperative or early post-operative event.

Left ventricular pump function before and after aortocoronary bypass surgery

Ten patients with severe effort angina and with left ventricular dysfunction during exercise before operation underwent haemodynamic and angiographic studies in average 20 months after coronary artery bypass surgery. Five patients (50%) were completely asymptomatic after operation(group I). The other five (group II) were still limited physically because of anginal pain, although two were much improved. Pre-operatively there was no significant difference in the severity of the disease, as judged from case histories, work tests and haemodynamic and angiographic findings between the two groups. The working capacity of the patients in group II was not increased significantly post-operatively. Their coronary arteriograms revealed unsatisfactory surgical results. In two patients, one significantly stenosed vessel was not bypassed because of poor run-off. In the other three patients, one graft was closed. Left ventricular function curves showed no significant improvement of left ventricular pump function. In group I, working capacity increased significantly, all stenoses of major coronary vessels were bypassed and all grafts were patent. Left ventricular function showed an almost normal response during exercise. These findings suggest that left ventricular dysfunction due to ischaemia can be significantly improved by coronary bypass and that there is a good correlation between clinical, haemodynamic and angiographic findings.

Effects of glucocorticosteroids in patients undergoing coronary artery bypass surgery

Glucocorticosteroid, methylprednisolone sodium succinate (MPSS), 30 mg/kg of body weight, or dexamethasone sodium phosphate (DSP), 6 mg/kg of body weight, were given intravenously to 60 patients, divided into two groups of 30 45 minutes prior to cardiopulmonary bypass for coronary artery bypass. These two groups were compared with 30 patients in a control group receiving a placebo and undergoing the same surgery. The study was carried out in a double-lind fashion. Patients receiving MPSS had a significantly higher cardiac index in both the preoperative and postoperative periods. This was accompanied by a decreased peripheral resistance. Patients receiving either MPSS or DSP also showed some evidence for the "washout" phenomenon indicating the possibility of better microcirculatory flow. Gluconeogenesis may have been enhanced in both groups receiving MPSS or DSP, but the evidence was greater in thos patients receiving MPSS. There were no hospital deaths in any of the three groups totaling 90 patients.

Recognition and quantification of myocardial injury by means of plasma enzyme and isoenzyme activities after cardiac surgery

Serial plasma enzyme determinations were carried out in 32 patients who underwent cardiac surgery with the aid of extracorporeal circulation. Plasma creatine kinase (CK), the cardiospecific isoenzyme of CK (CKMB), and alpha-hydroxybutyrate dehydrogenase (HBDH) were determined from the onset of surgery up to 100 to 120 hours after operation. From the plasma enzyme activities, the total amount of enzyme released by the injured heart into the circulation could be calculated using mathematical equations solved numerically by means of a computer. The calculated amount of CK, CKMB, and HBDH released by the heart correlated well with (1) postoperative mortality, and (2) peak activities of the respective enzymes. The calculated amount of any of the 3 enzymes released showed poor or no correlation with (1) electrocardiographic criteria of myocardial infarction, (2) duration of cardiopulmonary bypass, and (3) duration of total aortic cross-clamping. This study shows that the extent of myocardial injury after surgery can be assessed quantitatively using the calculated amounts of enzyme released, as well as using peak plasma activities of CKMB and HBDH.

Myocardial infarct imaging after cardiac surgery

One hundred and nineteen patients undergoing cardiac surgery had postoperative myocardial imaging performed with technetium pyrophosphate in order to assess the incidence of perioperative myocardial infarction. Fifty-six patients had only coronary artery bypass graft (CABG) surgery, of whom 13(23%) had a positive scintigram. Thirteen patients had CABG with other cardiac surgery and six (46%) had a positive scintigram. Fifty patients had other cardiac surgery but no CABG, and of these eight (16%) had a positive scintigram. The overall incidence of positive scintigrams was 23%, whereas definite or probable ECG diagnosis of infarction was present in 14 patients (12%). Serum levels of cardiac enzymes were higher in patients with positive scintigrams, but this finding did not consistently reach statistical significance. The use of a left ventricular vent during surgery did not correlate with a positive scintigram, nor did the total time on cardiopulmonary bypass or aortic cross-clamping. Patients having cardiac surgery, including CABG and valve replacement, have a 23% overall incidence of positive scintigrams. This suggests that the incidence of infarction after cardiac surgery is higher than can be recognized from the conventional criteria of ECG and enzyme changes.

Left ventricular function after aortocoronary bypass surgery

Aortocoronary bypass operations without additional myocardial surgery or valve replacement were performed at Ullevål Hospital in 190 patients during the period May 1971 to Dec. 1975. Postoperatively re-examination was made by left-heart catheterization in 124 patients at a mean interval of 18.2 months and right-heart catheterization in 108 patients at a mean interval of 16.0 months after surgery. The mean postoperative values for PCVP at rest, PCVP during exercise, LVEDP before contrast and LVEDP after contrast were significantly lower than the mean pre-operative values. The difference between pre- and postoperative values were largest in patients with elevated PCVP or LVEDP values before surgery, whereas in patients with low pre-operative values the mean values after surgery were unchanged or increased. The results indicate that marked improvement of left ventricular function may occur after aortocoronary bypass operations, even in patients with signs of ventricular failure at rest. A stress test is, however, of importance in evaluating the haemodynamic consequences of coronary surgery. No difference was found in patients with single versus patients with double or triple shunts. Post-operative shunt occlusion was found in 44 of 258 grafts at re-examination. No difference was found between patients with all shunts patent and patients with one or more shunts occluded as regard to mean postoperative PCVP and LVEDP values.

Myocardial consequences of coronary artery bypass graft surgery. The paradox of necrosis in areas of revascularization

Myocardial infarction after coronary artery bypass graft (CABG) surgery has been described clinically in up to 30% of patients but there is little morphologic information about the character and pathogenesis of the myocardial injury. We studied myocardium in the distribution of bypassed and nonbypassed coronary arteries for the presence of contraction band necrosis as compared to coagulation necrosis, in 58 autopsied patients who died less than 1 month after surgery. Operation related necrosis consisting of focal subendocardial contraction band necrosis was present to some degree in 48 (83%) patients. Regional transmural necrosis was present in 22 (38%) patients and was of two types. Contraction band necrosis occurred in 18 patients and was in the distribution of a patent bypassed coronary artery in 15 of them. Coagulation necrosis was found in four patients, and in each was in the distribution of a new graft-releated coronary artery occlusion. The results suggest that coronary artery reflow through widely patent grafts following the period of operative nonperfusion, rather than graft or intrinsic coronary artery occlusion, accounts for the majority of operation-related myocardial "infarcts" associated with CABG surgery. Thus, prevention of intraoperative myocardial injury must also focus on characteristics of the phase of myocardial reperfusion.

The application of radionuclide infarct scintigraphy to diagnose perioperative myocardial infarction following revascularization

To evaluate the application of radionuclide infarct scintigraphy to diagnose myocardial infarction after revascularization, we obtained postoperative technetium 99m pyrophosphate myocardial scintigrams, serial electrocardiograms and CPK-MB isoenzymes in ten control and 51 revascularized patients. All control patients had negative electrocardiograms and scintigrams, but eight had positive isoenzymes. Eight revascularized patients had positive electrocardiograms, images and enzymes and two had positive scintigrams and enzymes with negative electrocardiograms. Thirty-four patients with negative electorcardiograms and scintigrams had positive isoenzymes; in only seven patients were all tests negative. Our data suggest radionuclide infarct scintigraphy is a useful adjunct to the electrocardiogram in diagnosing perioperative infarction. The frequent presence of CPK-MB in postoperative patients without other evidence of infarction suggests that further studies are required to identify all factors responsible for its release.

Acute myocardial infarction and ischemic injury during surgery for coronary artery disease

The incidence of myocardial infarction, acute ischemic injury, and associated serum enzyme abnormalities has been evaluated in four operations involving the coronary circulation. The highest incidence of infarction was associated with internal mammary implantation (Vineberg procedure). There was no significant difference in the incidence of infarction, ischemic injury, or abnormal enzyme levels between patients with stable angina and those with unstable angina who had vein bypass surgery. In operations involving combined vein bypass grafting and valve replacement surgery, the incidence of abnormal serum enzyme elevations was higher than in any other procedure. The incidence of infarction and acute ischemic injury in combined operations was similar to that in other procedures but this may have been due to the difficulty in the ECG diagnosis of infarction in this group of patients, most of whom had abnormal preoperative ECGs.

Reduced incidence of intraoperative myocardial infarction during coronary bypass surgery with use of intracoronary shunt technique

Intraoperative myocardial infarction is a recognized complication of aortocoronary bypass surgery. One major cause of such infarction may be interruption of coronary blood flow, particularly in patient with poor coronary collateral circulation. In 30 patients use of an intracoronary shunt made it possible to limit the period of coronary occulusion during graft construction to a few minutes. Use of this shunt was associated with a reduced incidence of intraoperative myocardial infarction (as judged by the appearance of new Q waves) when these patients were compared with 50 patients operated on without this procedure (6 of 50 [12 percent] versus 0 of 30). The incidence of postoperative persistent S-T segment elevation was reduced from 21 of 50 (42 percent) to 5 of 30 (17 percent). Except for use of the shunt, the surgical technique was identical in the two groups of patients.

Mechanisms of angina relief in patients after coronary artery bypass surgery

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Diagnostic and prognostic significance of electrocardiographic and CPK isoenzyme changes following coronary bypass surgery: correlation with findings at one year

The incidence of ECG (14 per cent) indication of acute myocardial infarction complicating coronary artery bypass surgery is documented, corroborating the findings of prior series. An additional 32 per cent of patients had appearance of myocardial specific CPK-MB in serum during the immediate postoperative period. All patients surviving to 1 year following surgery (93 of 103) were asked to return for repeat cardiac catheterization to determine the presence and extent of interim ventricular contraction abnormalities. Sixty-five (70 per cent) of the group returned for evaluation. Preoperative and 1 year postoperative left ventriculograms were compared to determine if new contraction abnormalities would confirm the specificity of perioperative QRS and isoenzyme changes, and if the absence of new abnormalities would confirm their sensitivity. The majority of patients (65 per cent) had new areas of asynergy. However, 73 per cent of these were confined to the apex and thus could have been produced by the vent employed during cardiopulmonary bypass. QRS changes were 100 per cent specific and CPK-MB appearance was 78 per cent specific but they were only 20 and 54 per cent sensitive, respectively. Indeed, 46 per cent of those with new asynergy which was non apical had neither QRS change nor CPK-MB appearance. Thus QRS changes were always--and CPK-MB appearance was usually--associated with new asynergy but, in addition, many patients with no perioperative indication of infarction developed new areas of left ventricular contraction abnormality within the first postoperative year.

LDH isoenzymes and myocardial infarction in patients undergoing coronary bypass surgery: an excellent correlation

To evaluate the efficacy of LDH isoenzymes in the detection of myocardial infarction in patients undergoing coronary bypass surgery, 73 patients were studied pre- and postoperatively by ECG, CPK, SGOT, total serum LDH, and LDH isoenzyme measurements. A reversal of the LDH1:LDH2 ratio was considered indicative of myocardial necrosis. Accordingly, the patients were separated into two groups: Group A (23 patients) who demonstrated an LDH1:LDH2 ratio exceeding 1.0 and Group B (50 patients) who failed to reveal an LDH1;LDH2 reversal. The two groups were similar in regard to preoperative evaluation and operative procedure performed. The postoperative ECG findings were significantly different. In Group A 18 of 23 patients (78 per cent) developed significant new Q waves. This occurred in only one patient in Group B. Significant arrhythmias occurred in 70 per cent of the patients in Group A as compared to 14 per cent of those patients in Group B. Severe congestive heart failure and/or clinical evidence of shock occurred in 39 per cent of Group A patients and in none in Group B. The results of our study indicate that the reversal of the LDH1:LDH2 ratio is a valuable tool for the evaluation of postoperative myocardial infarction.

Monitoring tissue oxygenation of the heart after myocardial revascularization

A polarographic technique capable of simultaneous monitoring of myocardial tissue oxygen tension (MPO2) and intramyocardial electrograms by way of the same electrodes has been developed. Initially, the method was evaluated in dogs to verify the appropriateness of the directional changes of MPO2 in function of selected determinants of myocardial oxygen supply (regional coronary blood flow, arterial blood oxygen tension) and demand (heart rate, force of ventricular contraction). A combined reduction of MPO2 and elevation of the S-T segment in the corresponding electrograms was observed only when a 50 percent or greater reduction of blood flow to the sampled area was effected. Subsequently, in nine patients undergoing aortocoronary bypass surgery, MPO2 was measured from 48 areas for 2 weeks postoperatively. In 11 normal and 31 revascularized areas, MPO2 increased during the postoperative period. In four areas subsequently found to be supplied by occluded grafts MPO2 decreased from 12.7 +/- 3.1 (mean +/- standard error) to 10.1 +/- 3.3 mm Hg (P less than 0.05). In two areas, MPO2 decreased during the 3rd postoperative day from 16 to 3 and from 14 to 4.2 mm Hg, respectively. This reduction was attended by a significant rise in the S-T segment of the corresponding electrograms. This finding preceded by 24 hours standard electrocardiographic evidence of myocardial infarction. This technique appears to be sensitive and reliable, and thereby capable of enhancing the management of patients during the high risk early postoperative period after coronary bypass surgery.

Factors predictive of perioperative myocardial infarction during coronary operations

The diagnosis of perioperative myocardial infarction (PMI) in our patients was based upon electrocardiography, vectorcardiography, and postoperative enzyme changes. A group of 303 patients operated on between January and September, 1972, formed the basis of this study. Three groups were identified from among these patients. Group A was composed of 90 consecutive patients in whom MI was excluded by all criteria. Group B comprised 25 patients with proved MI and yielded the 8% incidence of MI among our patients. Group C included 34 patients with triple-vessel disease who did not sustain MI. Significantly more patients sustaining MI had preinfarction angina and severe coronary artery disease. The incidence of MI was also higher in patients with diffuse disease and those in whom the lesions could not be totally bypassed. A statistical correlation with longer pump runs and periods of anoxia was obtained. There was some suggestion that the preoperative location of the hypokinetic segment determined the site of MI in patients.

Follow-up catheterization of patients with myocardial infarction during coronary artery bypass surgery

Of 197 consecutive patients having aortocoronary bypass grafts over a 30 month period, 38 (19 per cent) had ECG evidence of myocardial infarction. The infarctions occurred more commonly in patients receiving multiple grafts. The infarctions were usually in areas supplied by grafted vessels. The infarctions occurred most often in the inferior wall, even when multiple vessels were grafted. Eleven patients with intraoperative infarction have had repeat postoperative coronary arteriograms. Seven had all grafts patent; three of these patients had hypokinesis of the infarcted wall. Four of the 11 patients had one or more occluded grafts; three of these patients had an area of hypokinesis. We conclude that intraoperative myocardial infarction is a common problem in aortocoronary bypass surgery and is not necessarily caused by graft occlusion.

Disappearance of abnormal Q waves after aortocoronary bypass surgery

Sixty-one patients were selected from 100 consecutive patients under-going aortocoronary artery bypass. The number of vessels diseased as defined by coronary arteriography and the number of bypass grafts were recorded. Review of the preoperative electrocardiograms showed an infarct pattern in 26 of the 61 patients and analysis of the postoperative electrocardiograms revealed loss of abnormal Q waves in 3 of the 26. The pre- and postoperative clinical course of these three patients is analyzed and the extent of their coronary artery disease and number of bypass grafts compared with those of the 23 patients who had persistence of the infarction pattern and the 17 patients who manifested new Q waves. Possible explanations for the disappearance of abnormal Q waves are discussed.

Ischemic myocardial injury following aorto-coronary bypass surgery

To assess the incidence of acute myocardial injury following aorto-coronary bypass surgery 151 patients (136 men and 15 women) were evaluated by studying serial preoperative and postoperative ECGs and SGOT, LDH and CPK levels. The mean age of men was 49.1 and of women, 53.1 years. Following surgery 15 patients (group I, 9.9 percent) developed new myocardial infarction as judged by Q wave criteria, 33 patients (group II, 22.5 percent) developed significant ST-T changes, and 103 patients (group III, 68 percent) had no significant ECG change. Mean postoperative SGOT values were: group I,126.2; group II, 100.6; and group III, 72.8. Only the difference in SGOT values between group I and III was significant (P less than 0.01). There was no correlation between type and site of surgery and the incidence of myocardial infarction. There were five deaths (3.3 percent). The combination of death and diagnosed myocardial infarction amounted to 12.6 percent of patients for this widely used elective procedure.

Changes in grafted and nongrafted coronary arteries following saphenous vein bypass grafting

Progression of disease in the native coronary arterial circulation was studied in 121 patients who underwent saphenous vein bypass graft surgery at the University of Alabama Medical Center, Birmingham, between 1969 and 1972, and who had a second coronary arteriogram at a mean interval of 11.7 months later. Two hundred thirteen arteries (10 triple, 74 double, 37 single) were grafted and 148 were not. Graft patency rate was 72%. Stenotic obstructive lesions in defined arterial segments and major branches were recorded for each artery at each examination. Pre and postoperative arteriograms were reviewed at the same time. Disease was expressed as "% stenosis" of each segment or branch examined. An arterial score, which was the sum of segments and branches seen on each occasion, was calculated for each artery and the scores were compared. New total occlusion, new obstructive lesions, and progression of pre-existing lesions were five times more frequent in grafted than in nongrafted arteries with comparable initial disease. New and progressive lesions were encountered with the same frequency in arteries with patent and occluded grafts. They occurred more frequently in segments proximal to the graft than in distal segments. Arteries with moderate (less than 75%) and arteries with severe (75-99%) stenosis had similar progression rates. Only 2% of segments of ungrafted arteries showed new total occlusions as compared to 60% of grafted arteries. The arterial score fell by 34% in grafted arteries and did not change in nongrafted arteries. These findings suggest that significantly fewer branches and segments of grafted arteries are seen following bypass grafting. New totally occlusive lesions are considerably more frequent in grafted than in nongrafted arteries and are not related to graft patency at one year after surgery. Disease progression in ungrafted vessels is relatively slow. These changes in the coronary arteries should be considered when assessing patients, particularly those with moderate degrees of stenosis, for bypass grafting.

Deterioration of myocardial function following aorto-coronary bypass operation

Twenty-two patients underwent cardiac catheterization before and an average of five months after aorto-coronary bypass operation (ACBO). Two groups were examined: 10 patients with all grafts patent, and 12 patients with one or more grafts occluded. All patients improved symptomatically, regardless of graft patency. However, in the occluded group, left ventricular end-diastolic pressure (LVEDP) increased (4.4 ± 2.2 mm Hg, P < 0.05), stroke volume index fell (9.8 ± 3.1 ml/m 2 , P < 0.05), ejection fraction decreased (10 ± 4%, P < 0.05), and left ventricular stroke work index fell (12 ± 3 g-m/m 2 , P < 0.01).

Qualitative analysis of segmental left ventricular contractility was performed. Of 28 segments supplied by patent grafts, six improved and nine deteriorated. Of 22 segments supplied by occluded grafts, none improved and eight deteriorated. Frequently no angiographically demonstrable basis for the segmental deterioration was evident.

We concluded that while ACBO may appreciably benefit severely symptomatic patients, our results do not substantiate the claim that ACBO should be recommended when the primary surgical goal is preservation or enhancement of myocardial function.