WEDNESDAY AFTERNOON, MAY 10, 1978

2:00 P.M. Scientific Session - Regency Ballroom

35. Regional Myocardial Dimensions Following Coronary Artery Bypass Grafting in Patients: The Relationship of Functional Deterioration to Graft Occlusion

LEONARD H. KLEINMAN*, RONALD C. HILL*,

W. RANDOLPH CHITWOOD*, JOHN W. HAMMON, JR.*,

KENT W. JONES* and ANDREW S. WECHSLER*, Durham, North Carolina

Sponsored by David C. Sabiston, Jr., Durham, North Carolina

The direct relationship between graft flow and regional myocardial function has not been documented in patients. Therefore, the present study was designed to quantitate the effects of coronary artery bypass grafting on regional myocardial mechanics distal to a coronary artery obstruction. Thirteen patients with subtotal or total occlusion of the left anterior descending coronary artery underwent coronary artery bypass grafting. Following completion of the aortic and coronary anostomoses, two miniature altrasonic dimension transducers (3 mm diameter) were positioned within the minor axis of the anterior left ventricular free wall and allowed complete freedom of movement. The transducers were placed at mid-wall depth, and areas of clinically apparent myocardial fibrosis were not utilized as sites of implantation. During control (C), 30 minutes following the termination of cardio-pulmonary bypass, regional myocardial dimensions, pulmonary artery diastolic pressures, arterial pressures and heart rate were recorded with all saphenous vein grafts open and following 30 seconds of single vein graft occlusion. These measurements were repeated during atrial pacing (AP) at a rate of 131 ± 3 beats/minute. Data are mean ±SEM. During C, graft occlusion resulted in a regional decrease in systolic excursion from 1.99 ± .37 to 1.59 ± .34 mm (p<.01), as well as a decrease in the rate of shortening from 9.91 ± 1.67 to 7.24 ± 1.38 mm/sec (p<01), while heart rate, arterial pressure and pulmonary artery diastolic pressure remained unchanged. Graft occlusion with AP resulted in an exaggerated decrease in both regional systolic excursion from 1.64 ± .36 to 0.85 ± .33 mm (p<.05), and rate of shortening from 10.76 ± 2.16 to 4.06 ± 1.50 mm/sec (p<.05). For the group of patients studied, end-diastolic lengths were unchanged with graft occlusion during C and AP. Moreover, with graft occlusion, isolated patients demonstrated regional dyskinesia as evidence by early systolic bulging. These studies in patients have documented for the first time that, despite a constant pre-load, after-load, and heart rate, regional myocardial function following coronary artery bypass grafting is dependent upon adequate graft flow, especially during stress.

*By invitation

36. Selective Arterialization of the Coronary Venous System: Encouraging Longterm Flow Evaluation Utilizing Radioactive Microspheres

MARK S. HOCHBERG*, WILLIAM C. ROBERTS*,

ANDREW G. MORROW and W. GERALD AUSTEN,

Bethesda, Maryland and Boston, Massachusetts

The longterm effectiveness of retrograde coronary venous bypass grafts (CVBG) to ischemic left ventricles was evaluated in 18 dogs. A saphenous vein was interposed between the aorta and left anterior descending (LAD) vein. The LAD vein was ligated proximal to the CVBG to prevent an arteriovenous fistula. The LAD artery was ligated at its origin to create anterior wall ischemia. Operative graft flow was 53 ml./min.

The 14 surviving dogs were catheterized 3-5 months later. Ten of the 14 CVBGs were patent angiographically. The chests were opened and graft flow now averaged 50 ml./min. ¹⁴¹Ce microspheres were then injected into the left atrium to measure myocardial flow to the anterior wall. In the 10 dogs with patent grafts transmural flow was 39±3 (S.E.) ml./100 gm. tissue/min., with flow to the subendocardium alone 40±11 ml./100 gm./min. The endocardial/epicardial flow ratio was 1.4/1, indicating that retrograde venous perfusion effectively delivered blood to the subendocardium.

After ligation of the CVBG, microsphere measured flow dropped to 15 ± 4 ml./100 gm./min. In 15 control dogs, anterior wall flow was 100 ± 10 ml./100 gm./min., decreasing to 13 ± 6 with ligation of the LAD artery and vein.

Histologic examination of the anterior wall of the left ventricle, the area served by the CVBGs for 3-5 months, disclosed no evidence of venous sclerosis or thrombosis, and no evidence of interstitial edema or hemorrhage. Some intimal proliferation was noted in the intramural small arteries and arterioles.

Thus, a coronary venous bypass graft improves anterior wall flow almost three-fold compared to the ischemia of LAD artery ligation. Moreover, restoration of flow with CVBG is effective because it perfuses all layers of the myocardium, especially the subendocardium - the crucial layer of myocardial muscle.

*By invitation

37. Atherosclerotic Changes in Coronary Vein Grafts 6 Years after Operation: Angiographic Aspect in 100 Patients

CLAUDE M. GRONDIN, LUCIEN CAMPEAU*,

JACQUES LESPERANCE*, B. CHARLES SOLYMOSS*,

YVES R. CASTONGUAY*, CLAUDE P. MEERE*,

JACQUES HERMANN*, FREDERICO CORBARA* and

MARTIAL G. BOURASSA *, Montreal, Quebec, Canada

Angiographic studies were conducted six years (71.5±9.6 months) after operation in 100 patients with coronary vein grafts who previously had had similar studies at 2 weeks and one year. Of the 159 patent grafts at one year 17 (10.7%) were occluded 5 years later and 14 (8.8%) showed localized narrowing of varying degree - more than half being ≥40%. Three grafts recovered at reoperation showed typical features of atherosclerosis.

Angiographically, these late narrowings differ from those described in studies conducted earlier after operation - occurring away from distal or proximal anastomoses - and are reminiscent of the more common narrowings seen in coronary arteries in that, usually, they are short and sharp.

Levels of serum lipids or blood sugar were comparable in patients with graft occlusion to those of patients showing graft narrowings. Progression of disease in the native (non-grafted) circulation differed, however, in the two groups being more prevalent in patients with graft stenosis and suggesting a common operative factor.

Late stenoses or occlusions in the graft could not be predicted upon review of the one year angiographic study. From the angiographic standpoint nearly all appeared amenable to surgical treatment although few patients complained of anginal symptoms, presumably because of patency of other grafts.

*By invitation

38. Intraoperative Relationships Between Regional Myocardial Distribution of Bypass Graft Flow and the Coronary Collateral Circulation

H. NEWLAND OLDHAM, JR., ROBERT H. JONES*,

C. CRAIG HARRIS*, W. ROBIN HOWE*, JACK K. GOODRICH*

and DAVID C. SABISTON, JR., Durham, North Carolina

Definition of the role of human coronary collateral vessels in supplying adequate perfusion to areas of ischemic myocardium is of considerable potential use in determining the proper number and optimal sites of insertion of bypass grafts for myocardial ischemia. To investigate this, the relationships between collateral flow and the volume and regional distribution of graft blood flow were studied in adjacent areas of myocardium. Measurements were obtained during a stable period prior to chest closure in 14 patients undergoing coronary artery bypass surgery. Using an electromagnetic flowmeter, graft flow was quantitated and the regional distribution of this flow was measured by radio-nuclide techniques. Two separate solutions containing macroaggregated human serum albumin particles labeled with 1-125 and Tc-99m were injected into the bypass grafts. Specially designed sterile scintillation probes were used to count both radionuclides simultaneously to map the distribution of the macroaggregates over 53 areas covering the surface of the heart. Flow in ml/min was calculated for each of the 53 regions by combining electromagnetic graft flow and the percentage distribution of the radioactivity. Injections were made into two separate grafts in three patients, into the same graft with an adjacent graft first open and then temporarily occluded in five patients, and into a graft with two sequential anastomoses in five patients. The entire study can be performed in 15 minutes.

In nine patients, there was no evidence of collateral communication between the anterior, lateral, or posterior regions of the myocardium, regardless of the presence or absence of angiographically visualized collateral vessels. In three patients, there was clear demonstration of an area of common perfusion over the apex of the heart supplied by both the anterior and posterior coronary arteries. Only two patients had collateral flow between closely adjacent regions of the anterolateral left ventricle and neither had angiographically demonstrated coronary vessels. In five patients with sequential anastomoses to adjacent areas of myocardium, both the total volume and the distribution of flow were improved by grafting both areas.

From these data, it is concluded that: (1) bypass graft flow is distributed to localized regions of myocardium, (2) collateral blood flow rarely occurs between adjacent areas of myocardium, (3) sequential or multiple grafts are beneficial in completely revascularizing adjacent areas of underperfused myocardium, and (4) concepts of coronary collateral blood flow and function derived from experimental animals may not apply to patients and human data are necessary for application to the clinical situation.

*By invitation

39. Probability of Survival After Coronary Bypass Surgery in Veterans Administration and Community Hospitals

J. S. CAREY, R. A. CUKINGNAN*

and G. F. GRONER*, Los Angeles, California

The VA Cooperative Study of coronary artery surgery has been criticized because (1) VA patients may differ from the population at large and (2) the surgical results were suboptimal in terms of hospital mortality and graft patency rates. To evaluate these problems, we compared the surgical results obtained at Wadsworth VA (VA-W) with those of the VA Cooperative Study (VA-C) and with the results obtained in a community hospital series (CH). There were 154 VA-W and 152 CH patients operated upon since January, 1972 who were followed at least one year. One to five saphenous vein grafts were performed using normothermic perfusion and intermittent aortic cross-clamping. The VA-W patients were similar to the VA-C patients in most categories: 3-vessel disease, 51% (VA-W) vs. 49% (VA-C); previous MI, 55% vs. 64%; LV function abnormalities, 55% vs. 64%. The results in the VA-W group were: hospital mortality 0.7%; perioperative infarction rate 5.8%; three year survival 94%; annual mortality rate 2.0%; graft patency rate 85% (168 of 197) and number of patients with at least one graft open 97% (66 of 68). These results contrast sharply with those of the VA-C series, but are very similar to results reported from the San Franciso VA. Compared to the CH series, the VA patients were younger, had more advanced symptoms, more previous MI's and a higher incidence of abnormal left ventricle (p<.05); bypass time, aortic cross-clamp time and duration of hospitalization were longer (p<.001). The annual cardiac mortality was 1.2% in the CH patients (not significant by Wilcoxon test). We conclude that (1) coronary bypass surgery differs significantly in VA and community hospitals, and (2) the data reported by the VA Cooperative Study is not representative of surgical results in non-participating VA hospitals or in community hospitals.

*By invitation

40. Is There a Penalty for Subtotal Myocardial Revascularization?

JAMES W. JONES*, JOHN L. OCHSNER, NOEL L. MILLS

and WILLIAM P. DUNLAP*, New Orleans, Louisiana

The influence of subtotal myocardial revascularization on clinical success following direct coronary artery procedures was studied by computer statistical methods. Of the initial 1004 patients requiring direct myocardial revascularization at Ochsner Clinic, 707 had all vessels with 70% or greater luminal lesions bypassed; 202 had a major coronary lesion unbypassed; 53 patients had a minor vessel untreated; and 42 patients had both a major and a minor lesion untreated. Follow-up, complete in 98% of instances, has ranged from 2 to 8 years and averages 48.6 months. Clinical success was determined by anginal relief, non-fatal myocardial infarction rates, congestive heart failure rates, and longevity. Of the four parameters, only longevity was adversely affected in the overall group with untreated stenoses, but more comprehensive analysis showed this to be secondary to advanced disease as determined by a higher percentage of patients having decreased ventricular function by angiography. Although the disease process seemed to determine the clinical outcome, patients with severely decreased ventricular function had higher rates of unrelieved angina (5.3% vs. 26.1%) (p=0.0172) when subtotal revascularization was done. Patients with good ventricular function who had subtotal, revascularization experienced significantly higher non-fatal myocardial infarction rates (p=0.032). Certain factors were associated with a higher percentage of subtotal revascularization: (1) generalized decreased ventricular function; (2) ventricular aneurysmectomy; (3) age of 70 years or older and (4) larger number of vessels diseased. Those who had diabetes, hypertension, or hyperlipo-proteinemia, women, and cigarette smokers did not have increased rates of subtotal revascularization. Analysis according to the specific vessels bypassed or left unbypassed was unremarkable.

*By invitation

41. Coronary Bypass Surgery - Five Year Follow-Up of a Consecutive Series of 140 Patients

GEORGE E. GREEN, HARVEY G. KEMP*,

SAMIR ALAM* and IVAN DAVID *, New York, New York

The five year follow-up of a consecutive series of 140 patients who had coronary bypass surgery performed by one surgeon will be reported.

One hundred forty patients were operated between January and December of 1972. Twenty patients had single grafts, 49 double grafts, 58 triple grafts, 12 guadruple grafts, 1 quintuple grafts. Of the 345 grafts, 120 were mammary arteries and 225 were saphenous veins. Saphenous veins were removed from below the knee and measured 2.5 - 4.0 mm. diameter. Arteriotomies and anastomoses were performed with high magnification (Zeiss Operation Microscope 16x).

Five year survival was 93 per cent. There were 2 hospital deaths and 7 late deaths. Two of the late deaths were due to cancer and 5 were considered cardiac. Cardiac deaths occurred three months (1), three years (2), four years (1), and five years (1) after operation. Two patients were lost to follow-up two or more years after operation.

Of the 129 patients followed for five years 92 (70%) had no angina and 37 (30%) had at least one episode of angina. Thirty of these patients considered the angina to be less severe, 6 considered it to be the same and 1 considered it to be more severe than before the operation.

Late angiograms, predominantly in symptomatic patients, showed vein graft patency to be 80% and mammary artery patency to be 95%. Selective injection of radioactive xenon showed mammary artery flow to be equivalent to vein graft flow and to normal coronary flow.

*By invitation

42. Changing Concepts in the Surgical Management of Left Main Coronary Artery Disease

HENRY J. SULLIVAN*, ROQUE PIFARRE, DONALD DIXON*,

JOHN M. MORAN*, ALVARO MONTOYA*, SARAH A. JOHNSON*,

ADEL EL-ETR*and ROLF M. GUNNAR*, Maywood, Illinois

Since June 1970, 196 patients with significant main left coronary artery stenosis have undergone surgery. Our experience with this condition may be divided chronologically into three phases.

PHASE 1: 89 patients. Hemodynamic instability with frequent hypertension during induction of anesthesia characterized this group. Nine (10%) patients required urgent institution of cardiopulmonary bypass (CPB) for acute left ventricle failure. Operative mortality was 11% (10 patients).

PHASE 2: 55 patients. Intra-aortic balloon counterpulsation (IABC) was instituted prior to surgery. Only one patient required urgent CPB. Operative mortality was 1.5%(1 patient).

PHASE 3: 52 patients. Anesthetic management was characterized by pharmacologic reduction of left ventricular afterload with intravenous nitroprusside or nitroglycerine, and monitoring of pulmonary (PA) pressure. No patients required urgent CPB and there was no operative mortality.

Anesthetic induction is a critical time in the surgical management of patients with significant left main coronary stenosis. Our experience suggests that hemodynamic stability during this period may be achieved by IABC or by pharmacologic unloading of the left ventircle aided by monitoring of PA pressure.

Adjournment