Biomedical subjects
D C McGoon
Publications and source records attributed to D C McGoon.
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.
Clinical follow-up study of paroxysmal supraventricular tachyarrhythmias after operative repair of a secundum type atrial septal defect in adults.
Adults with isolated secundum atrial septal defect (ASD) may present with paroxysmal atrial tachyarrhythmias. The clinical course of these rhythmic disturbances after correction of the ASD is unknown. Of 188 patients aged 44 years old or older with isolated ASD, 27 (14%) (mean age 52.7 years, range 44 to 71) had documented paroxysmal atrial tachyarrhythmias preoperatively: 16 had paroxysmal atrial fibrillation, 2 had atrial flutter, and 9 had supraventricular tachycardia. Among these 3 groups, there were no differences in age, sex, New York Heart Association class, duration of preoperative symptoms, mean right atrial and pulmonary arterial pressures, shunt size, atrial size, or follow-up period. After operative repair, follow-up data were available in all patients for a mean of 12 years (range 1.5 to 25). Of the 16 patients with preoperative paroxysmal atrial fibrillation, 14 (88%) continued to have increasingly frequent paroxysmal atrial fibrillation, culminating in sustained atrial fibrillation. In 1 of the 2 patients with paroxysmal atrial flutter, sustained atrial fibrillation developed. Of the 9 patients with preoperative paroxysmal supraventricular tachycardia, 5 had no further episodes of this arrhythmia postoperatively.
Hypertrophic obstructive cardiomyopathy: ten- to 21-year follow-up after partial septal myectomy.
This study reviews the outcome in 36 consecutive patients who survived partial septal myectomy for hypertrophic obstructive cardiomyopathy operated on between 1960 and 1972. All patients were followed up until death or until June 1981 (mean 13.4 years). Of the 26 survivors, 17 had been more than mildly symptomatic preoperatively, but only 1 remained so postoperatively. The operation was effective in relieving the obstruction (peak systolic pressure gradient reduced from 79 to 8 mm Hg [p less than 0.001]), and mitral regurgitation was relieved. No survivor's symptoms worsened, but 10 died late--4 suddenly, 5 from congestive heart failure, and 1 from a malignancy. The 10-year survival rate was 77%. No correlation with outcome was found with respect to age, surgical approach, preoperative functional class, pressure gradient, left ventricular end-diastolic pressure, or presence of atrial fibrillation, but atrial fibrillation occurring late postoperatively (12 patients) was associated with an increased frequency of late death (7 of 10 late deaths) or continuing New York Heart Association functional class III status. Early or late postoperative complete heart block occurred in 1 patient each. Thus, these results suggest a favorable effect of operation and support continued surgical intervention for appropriate patients.
Complete repair of pulmonary atresia with nonconfluent pulmonary arteries.
From 1973 through 1979, 16 patients with pulmonary atresia, two normal-sized ventricles, and bilateral but nonconfluent pulmonary arteries underwent complete repair at the Mayo Clinic. Mean age at operation was 9.1 years (standard deviation [SD] 5.2 years). Sources of pulmonary flow were previous surgical shunts, patent ductus arteriosus, and discrete systemic-pulmonary arterial collaterals. The complete surgical repair included interruption of extracardiac shunts, closure of ventricular septal defect (15 patients), closure of atrial septal defect (3 patients), and establishment of right ventricular-pulmonary arterial continuity with a porcine-valved extracardiac conduit anastomosed to a transverse limb (T graft in 12 patients) or to a side-limb (Y graft in 4 patients). There were no operative deaths. Morbidity included reoperation for bleeding in 3 patients and compression of the prosthetic graft by the sternal closure in 1. The mean postrepair ratio of right ventricular peak systolic pressure to left ventricular peak systolic pressure (pRV/pLV) was 0.64 (SD, 0.23). Follow-up ranged from 12 to 72 months (means, 34.6 months; SD, 20.7 months). One patient died 12 months after operation (postrepair pRV/pLV, 1.3). Conduit obstruction has been proved in 4 patients, of whom 3 underwent reoperation for extracardiac conduit obstruction at 46, 47, and 48 months. The remaining 11 patients are alive and free of major symptoms.
Closure of perimembranous ventricular septal defect.
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The dimensions of surgical progress in cardiac surgery.
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Double-outlet right ventricle. Surgical results, 1970-1980.
Between Jan. 1, 1970, and Jan. 1, 1980, 62 consecutive patients underwent repair of classic double-outlet right ventricle (DORV). Patients with subpulmonic ventricular septal defect (VSD), complete atrioventricular canal, atrioventricular discordance, and univentricular heart were excluded. One hundred six associated defects were present in 54 patients. Forty-six patients had pulmonary stenosis. The 36 male and 26 female patients ranged in age from 8 months to 37 years (median age 9 years). The early mortality was 11% for those with pulmonary stenosis, 25% for those without pulmonary stenosis, and 15% for the entire series. The risk of mortality was related to the age of the patient at operation. Causes of early deaths included low cardiac output (three patients), high residual right ventricular pressure (three patients), anomalous coronary artery injury (one patient), infection (one patient), and hemorrhage (one patient). Eleven late deaths occurred among the 53 operative survivors (21%). Ten (91%) of the late deaths were attributed to arrhythmia. All except one of the long-term survivors are in Functional Class I or II. Although the operative mortality for the repair of DORV continues to decrease, the late mortality is of concern, and the problem of late arrhythmia necessitates further study and analysis.
Cardiac-catheterization and cardiac-surgical facilities: use, trends, and future requirements.
Cardiac catheterizations and cardiac operations were evaluated in the population of Olmsted County, Minnesota, from 1973 through 1980, and trends in this region were compared with nationwide trends based on data from several sources. The rates of coronary arteriography and coronary-artery bypass operations in Olmsted county have increased over time, but overall, the rates of catheterization and operation appeared to be leveling off. For the country as a whole, the data appear to show similar trends, but there are wide differences among regions in the rates of operation and catheterization. In 1980 40 per cent of hospitals with cardiac-catheterization laboratories and 55 per cent of those with facilities for open-heart surgery were doing fewer than the suggested minimum numbers of these procedures necessary to achieve optimum results. The data support the view that further growth in the number of cardiac centers should be avoided. We believe there is a need for continued evaluation of the use of cardiac services if quality is to be protected and costs controlled.
Changing trends in cardiac disease and cardiac surgery.
The trends in cardiac surgery during the four decade or so life history of this specialty have been inexorably toward progress--a greater capacity to relieve suffering and to prolong life for patients afflicted with cardiac disease. It has been a team effort, led by a professional coalition of cardiologist, cardiac anaesthetist, cardiac pathologist and cardiac surgeon, but also with major involvement of nursing, technical and supporting specialties. As technology and capability have progressed and will continue to do so, the challenge for the future, both professionally and socio-economically, will increasingly be our capacity to deliver this demanding, sophisticated and expensive care to expanding proportions of aging individuals, creating a problem which can ultimately be met only by new knowledge and new disciplines of prevention.
Partial atrioventricular canal defect in elderly patients (aged 60 years or older).
Partial atrioventricular canal defect in elderly patients (aged 60 years or older) is extremely rare, and surgical results in this select group have not been reported. This report describes in detail the clinical profile of six such patients and the surgical results in four of the six. There was no operative mortality. This experience, albeit based on small numbers, suggests that operation can be performed at low risk with gratifying symptomatic improvement and that surgical repair in symptomatic elderly patients with partial atrioventricular canal detect can be justified.
Late results after extracardiac conduit repair for congenital cardiac defects.
Analysis of the late results in 352 patients surviving insertion of an extracardiac conduit before mid 1977 has provided a mean follow-up interval of 65 months. Three fourths of the patients remain in improved condition after operation. Serial measurements of transconduit gradient are available in 90. The median change was +7 mm Hg and the mean +21 mm Hg. Reoperation was required in 16 percent of patients (mortality rate 9 percent), most commonly (77 percent) because of progressive conduit stenosis, more commonly for transposition of the great arteries than for other types of anomalies, and more commonly after use of a homograft aortic conduit than a Hancock conduit. The side of the aorta on which the conduit was placed exerted no significant influence. The postrepair transconduit gradient did not affect the need for reoperation. Late survival was 95 percent at 1 year, 85 percent at 5 years, and 73 percent at 10 years and was significantly better (probability [p] less than 0.006) for patients with pulmonary atresia than for the others. The hospital mortality rate was highest, and the late mortality rate lowest, for children less than 5 years of age; the overall survival rate in this age group was lower. The postrepair right ventricular to left ventricular pressure ratio, together with age, was a principal prognostic indicator of late survival, being less good when more than 0.73. THe most frequent causes of late death were progressive congestive heart failure and sudden death.
Long-term endocardial atrial pacing in children with postoperative bradycardia-tachycardia syndrome and limited ventricular access.
Permanent pacing in children, including those with postoperative bradycardia-tachycardia syndrome has been compromised by the availability of pulse generators, electrode leads and implantation techniques designed for the adult patient. Recent technologic improvements and simplified implantation techniques have reduced many of these barriers and have made endocardial as well as epicardial ventricular pacing more feasible. However, in some children, ventricular pacing may be impeded by anatomic abnormalities due to congenital anomalies or prior cardiac operations. In these instances, endocardial atrial pacing may provide an alternative therapeutic approach in selected patients. This report describes the use of endocardial atrial demand pacing in four children with postoperatively bradycardia-tachycardia syndrome and restricted ventricular access. This approach controls symptomatic bradycardia, helps prevent and convert paroxysmal intraatrial tachycardia and overcomes the problems of limited ventricular access.
Long-term effects of prosthetic materials.
The surgical repair of the various types of congenital cardiac defects often requires the use of prosthetic materials, both bioprosthetic and synthetic. Patches have proved highly effective in many applications and locations. All prosthetic valves have significant limitations, and particularly disappointing was the observation that bioprosthetic valves undergo accelerated degeneration in younger patients. The extracardiac conduit allowed corrective operation for several complex types of anomalies, but it suffers the double jeopardy of premature degeneration of its integral tissue valve (if any), and progressive peel formation within its lumen. A threat of infection exists in the presence of prosthetic materials, especially valves. These known limitations of prosthetic devices as well as possible potential late complications not yet fully elucidated are sufficient indication for periodic, perpetual surveillance of patients who have received cardiac prostheses.
Partial atrioventricular canal defect in adults.
Between March 1955 and March 1981, 52 adult patients (age 20 years or older) with partial atrioventricular canal (PAVC) were examined at the Mayo Clinic. Forty patients were in New York Heart Association (NYHA) functional class I or II. The ECG showed right bundle branch block with left-axis deviation in 48, first-degree atrioventricular block in 33 and atrial fibrillation in nine. Preoperative catheterization was done in 37 patients; the mean pulmonary resistance index was 2.8 U.m2, and the mean pulmonary-to-systemic flow ratio was 3.0. Forty-seven patients underwent operation; two required mitral valve replacement. There were three operative deaths (6.4% operative mortality) and two late deaths. All surviving patients were in NYHA class I or II. No patient required subsequent permanent pacemaker implantation. We conclude that repair of PAVC in adults may be performed at low risk and may improve patient longevity and functional status.
Pathogenesis of nonobstructive fibrous peels in right-sided porcine-valved extracardiac conduits.
An autopsy study was conducted of 14 cardiopulmonary specimens in which porcine-valved extracardiac conduits had been placed from the right ventricle to the pulmonary artery. The gross and light microscopic appearance of the tissue lining in such conduits was evaluated. In no instance was the lining considered obstructive. The conduits had been in place for varying lengths of time ranging from 1 day to 5 years. The neointima appeared to begin developing as early as the first postoperative day as a thin layer of platelet-fibrin thrombus, followed by incorporation of red blood cells and a few leukocytes. Between 2 to 3 weeks postoperatively, such shallow thrombotic linings had become organized by fibroblastic migration and proliferation from both the proximal and distal anastomosis sites. However, incomplete development of the neointima frequently led to fenestrations. Peels, or neointimae, older than 1 month did not change, having densely fibrous luminal surfaces and having thrombus or necrotic thrombotic debris along the interface between the conduit and peel. These findings support the concept that progressive thickening of the lining peel takes place primarily along the interface between the peel and the conduit rather than the interface between the peel and the lumen.
Results of surgical treatment of ascending aortic dissections occurring late after cardiac operation.
Seven patients (one woman) have been seen with ascending aortic dissections at a mean of 8.8 years (6 months to 20 years) after cardiac operation. Previous cardiac operations included saphenous vein coronary artery bypass grafts (CAB) (two), aortic valve replacement (AVR) (one), aortic valvulotomy (one), AVR plus CAB (two), and patch closure of a ventricular septal defect and repair of a perforated aortic cusp (one). During the initial operation, three of seven patients had dilatation of the ascending aorta. Five of seven patients were hypertensive at the time of diagnosis of dissection. Six patients were managed by operation. A composite prosthetic aortic valve and ascending aortic graft with implantation of coronary ostia and saphenous vein grafts was utilized in three patients. In three the repair was by graft replacement of the ascending aorta alone. Five of six patients survived repair and were asymptomatic at discharge. Subsequent problems resulting from distal, descending thoracic, or abdominal aortic extension of the dissection were frequent and necessitated fenestration (one patient) or a graft replacement of the infrarenal aorta (one patient). We conclude that patients may be predisposed to aortic dissection occurring late after cardiac operation, possibly related to prior aortic valvular disease or systemic arterial hypertension. Operative repair is feasible and relatively safe. Follow-up for potential complications of distal aortic problems seems indicated. Techniques of operative repair in these patients are emphasized.
Systemic thromboembolism in mitral and aortic Starr-Edwards prostheses: a 10-19 year follow-up.
Our study comprised 302 consecutive patients seen between 1962 and 1971 who underwent mitral (MVR) (132 patients) or aortic valve replacement (AVR) (170 patients) with a Starr-Edwards prosthesis because of advanced mitral or aortic incompetence. The follow-up interval was 10-19 years. For more recent valve models (1200/1260 aortic or 6120/6310 mitral), the probability of a surviving patient remaining free of systemic thromboembolism after 10 years was 70% for MVR and 74% for AVR. The probability of freedom from thromboembolism was less than this for the earlier valve models; the probability for the entire group at 10 years was 66% and at 15 years was 58%, with no significant difference between AVR and MVR. About one-fourth of the patients with an embolism (20% MVR, 27% AVR) had more than one embolic event. Of all emboli, most (86% MVR, 84% AVR) were cerebral, about half (48% MVR, 57% AVR) left a neurologic deficit, and about one-tenth (11% MVR, 10% AVR) led to death. Of the predictive factors reviewed, the incidence of emboli was significantly higher only in patients with MVR considered to have inadequate anticoagulation (p less than 0.01) and in patients receiving model 6000 mitral prosthesis (p less than 0.02). This long-term follow-up study of patients with a Starr-Edwards prosthesis reveals that systemic embolism is a persistent and significant problem.