Robert B. Wallace

A Platelet-Inhibitor-Drug Trial in Coronary-Artery Bypass Operations: Benefit of Perioperative Dipyridamole and Aspirin Therapy on Early Postoperative Vein-Graft Patency

To prevent occlusion of aortocoronary-artery-bypass grafts, we conducted a prospective, randomized-double-blind trial comparing dipyridamole (instituted two days before operation) plus aspirin (added seven hours after operation) with placebo in 407 patients. Vein-graft angiography was performed in 360 patients (88 per cent) within six months of operation (median, eight days). Within one month of operation, 3 per cent of vein-graft distal anastomoses (10 of 351) were occluded in the treated patients, and 10 per cent (38 of 362) in the placebo group; the proportion of patients with one or more distal anastomoses occluded was 8 per cent (10 of 130) in the treated group and 21 per cent (27 of 130) in th placebo group. This benefit in graft patency persisted in each of over 50 subgroups. Early postoperative bleeding was similar in the two groups. In this trial dipyridamole and aspirin were effective in preventing graft occlusion early after operation.

Effect of Dipyridamole and Aspirin on Late Vein-Graft Patency after Coronary Bypass Operations

To study the prevention of occlusion of aortocoronary-artery bypass grafts, we concluded a prospective, randomized, double-blind trial comparing long-term administration of dipyridamole (begun two days before operation) plus aspirin (begun seven hours after operation) with placebo in 407 patients. Results at one month showed a reduction in the rate of graft occlusion in patients receiving dipyridamole and aspirin. At vein-graft angiography performed in 343 patients (84 per cent) 11 to 18 months (median, 12 months) after operation, 11 per cent of 478 vein-graft distal anastomoses were occluded in the treated group, and 25 per cent of 486 were occluded in the placebo group. The proportion of patients with one or more distal anastomoses occluded was 22 per cent of 171 patients in the treated group and 47 per cent of 172 in the placebo group. All grafts were patent within a month of operation in 94 patients in the placebo group and 116 patients in the treated group; late development of occlusions was reduced from 27 per cent in the placebo group to 16 per cent in the treatment group. The results show that dipyridamole and aspirin continue to be effective in preventing vein-graft occlusion late after operation, and we believe that such treatment should be continued for at least one year.

Trial of combined warfarin plus dipyridamole or aspirin therapy in prosthetic heart valve replacement: Danger of aspirin compared with dipyridamole

Despite the use of oral anticoagulation in patients with prosthetic heart valves, persistent thromboembolism over time warrants a search for improved methods of prevention. Thus, patients receiving 1 or more mechanical prosthetic heart valves were randomized to therapy with warfarin plus dipyridamole (400 mg/day) or warfarin plus aspirin (500 mg/day) on the basis of location and type of valve and surgeon, and followed up with a concurrent, nonrandomized control group taking warfarin alone. In 534 patients followed up 1,319 patient-years, excessive bleeding (necessitating blood transfusion or hospitalization) was noted in the warfarin plus aspirin group (23 of 170 [14%], or 6.0/100 patient-years) compared with warfarin plus dipyridamole (7 of 181 [4%], or 1.6/100 patient-years, p less than 0.001), or warfarin alone (9 of 183 [5%], or 1.8/100 patient-years, p less than 0.001). A trend was evident toward a reduction in thromboembolism in the warfarin plus dipyridamole group (2 of 181 [1%], or 0.5/100 patient-years) as compared with warfarin plus aspirin (7 of 170 [4%], or 1.8/100 patient-years), or warfarin alone (6 of 183 [4%], or 1.2/100 patient-years). Adequacy of anticoagulation (based on 12,720 prothrombin time determinations) was similar in all 3 groups with 65% of prothrombin times in the therapeutic range (1.5 less than or equal to prothrombin time/control less than or equal to 2.5), 30% too low, and 5% too high. Warfarin plus aspirin therapy resulted in excessive bleeding and is contraindicated. Longer follow-up study is needed to determine whether further separation of the incidence of thromboembolism can be detected.

Complete Repair of Transposition of the Great Arteries with Pulmonary Stenosis A Review and Report of a Case Corrected by Using a New Surgical Technique

Complete surgical correction of transposition of the great arteries associated with subvalvular pulmonary stenosis carries a high mortality rate. A new surgical technique that achieves redirection of the ventricular outflows and relieves pulmonary stenosis by bypassing it, was successfully used to repair complete transposition of the great arteries associated with ventricular septal defect (VSD) and valvular and subvalvular pulmonary stenosis in a 14½-year-old patient. The repair consists of (1) division of the pulmonary artery, the cardiac end of which is oversewn, (2) repair of the VSD with a patch in such a way as to connect the left ventricle with the aorta, and (3) reconstruction of the pulmonary artery with an aortic homograft, including the aortic valve, which is anastomosed between the distal end of the pulmonary artery and the right ventricle.A review of the cases in which the current techniques were used indicates that the location and nature of the obstruction in the left ventricular outflow tract defies successful repair in most instances. Localized ridges and diffuse hypoplastic outflow tracts are recognized causes of obstruction, but anomalies of the mitral valve commonly contribute to or are the primary cause of subvalvular obstruction.

Pathologic changes in aortocoronary saphenous vein grafts

Abstract Aortocoronary saphenous vein grafts from 40 patients (total 62 grafts) were studied at autopsy. The earliest change seen was the insudation of blood constituents into the vein intima. Occluding thrombi were seen in six grafts from short-term survivors, and one organized thrombus was seen in a graft from a long-term survivor (28 months). Various degrees of intimai thickening were seen in grafts from all patients surviving for more than a month; this had progressed to diffuse occlusion in three cases. Gross and microscopic findings correlated well with postmortem angiographic findings in the long-term survivors. Electron microscopic examination showed smooth muscle cells, collagen fibers and ground substance in the thickened intima. Fibroblasts were not a feature of this thickening. Increased permeability of the graft endothelium, due to injury or hemodynamic factors, may result in exposure of medial smooth muscle cells to certain plasma factors and thus promote smooth muscle cell hyperplasia as has been produced in certain experimental models.

Long-term follow-up of isolated replacement of the aortic or mitral valve with the Starr-Edwards prosthesis.

Review of 1,684 cases of isolated aortic or mitral valve replacement with a Starr-Edwards prosthesis demonstrated that the procedure provides improved life expectancy over that found in the natural history of valvular heart disease. Further improvement in results depends on continued reduction in operative and late mortality and in the incidence of thromboembolism. Advanced preoperative functional class, atrial or ventricular enlargement, a history of prior heart surgery, advanced age at operation and untreated valvular disease were among the factors related to increased early or late mortality. The data suggest that adequate anticoagulation, earlier performance of valve replacement and more complete repair of valvular dysfunction may increase survival rates.

Postinfarction Ventricular Septal Rupture Surgical Considerations and Results

Twenty-two patients had ventricular septal rupture complicating acute myocardial infarction. Sixteen of the 22 patients underwent surgical repair. The clinical findings, catheterization data, and operative results suggest that closure of the rupture should be delayed when possible from three to six weeks after the infarction to allow firm fibrous healing of the region. When surgery is thus delayed, the operative risks are smaller and the long-term results are good.

Pregnancy and Open-Heart Surgery

During pregnancy, when surgically reparable heart disease can no longer be medically manged, open- or closed-heart surgery is the procedure of choice without prior therapeutic abortion. Cyanotic congenital heart disease in a pregnant patient when completely correctable surgically may be an indication for surgery in itself. Available data suggest that pregnancy per se does not increase the maternal risk of heart surgery with use of extracorporeal circulation. Fetal mortality in our series was 33%.

Selection of Patients with Truncus Arteriosus for Surgical Correction Anatomic and Hemodynamic Considerations

Six years have passed since the first successful surgical correction of truncus arteriosus. A review of our experience enables some conclusions regarding the operation. Patients with mild or moderate truncal valve incompetence do not need truncal valve replacement. Patients with severe truncal valve incompetence require valve replacement, which is associated with a significantly increased surgical mortality. The surgical mortality is not increased in hemodynamically favorable patients who have only one pulmonary artery. However, these patients are especially likely to have early development of severe pulmonary vascular disease. The surgical mortality for the patient with uncomplicated disease and two pulmonary arteries, with pulmonary resistance of less than 8.0 units m2, is 10%. In patients with pulmonary resistance between 8.0 and 12 units m2, the mortality is approximately three times greater. Patients with pulmonary resistances greater than 12.0 units m2 are probably inoperable. Different hemodynamic criteria must be applied in assessing the operability of patients with a single pulmonary artery. A systemic arterial oxygen saturation less than 85% in a patient with two pulmonary arteries and without pulmonary artery stenosis or a pulmonary artery band usually indicates inoperability. Elective operation usually is deferred until a patient is four years old, but if the patients clinical condition warrants, the procedure can be done at any time after the age of one year, with a good chance of success. Follow-up on most operated patients has been encouraging.

Closed mitral commissurotomy: Recent results in 291 cases

Abstract Early and late results for 291 patients undergoing closed mitral commissurotomy, usually with transventricular dilator, between July 1, 1960, and July 1, 1964, are presented. The over-all hospital mortality rate was 3.4 per cent (1.5% for patients with no previous mitral valve surgery). Over-all incidence of operative or postoperative arterial embolism was 2.4 per cent (5% in patients with a history of arterial embolism). Causes of hospital deaths are listed. Within the period of follow-up, results of surgery were good in 86 per cent of patients traced. When the valve was immobile or significantly incompetent or when an optimal initial opening was not obtained at operation, the results were less good. In proper circumstances, good palliation at a low risk usually can be achieved by a closed operation.