Biomedical subjects
Publications and source records attributed to A R Dobell.
A summary of Vineberg's experimental pioneer work on the internal mammary artery implant is presented, together with comments on the clinical series and the difficulty in evaluating the results before the era of coronary angiography. A plea is made for recognition of the fact that an implanted internal mammary artery can arborize and communicate with the native coronary arteries.
Eighty-six patients received orthotopic cardiac transplants at the Royal Victoria Hospital in Montreal between 1985 and 1989. Of these, 16 mortally ill, being sustained in hospital by the intravenous administration of inotropic agents (15 patients [94%]) or intra-aortic balloon counterpulsation (6 [38%]). There was one early death (at 7 days), for a death rate of 6.3% (versus 8.6% for the 70 "elective" transplants). Two others died of delayed infection: one of viral hepatitis at 6 weeks, and one of pneumonia due to Pneumocystis 4 months after transplantation. The other 13 patients are alive and well 12 to 66 months postoperatively. Nine have returned to their preoperative work, three have decreased activity levels but are functioning well, and one is retired.
Seventy-four children aged 0.3 to 21.4 years (median 4.0) were followed echocardiographically on days 4, 7, 14 and 28 (+/- 2 days) after cardiac surgery to evaluate the incidence of postoperative pericardial effusion, to identify the patients at greatest risk of developing an effusion and to evaluate the use of aspirin as prophylaxis against pericardial effusion. Pericardial effusion was graded relative to the size of the aortic root from grade 0 (no effusion) to grade 5 (larger than the aortic root dimension). Patients were randomly divided into 2 groups: group 1 (32 patients) received aspirin 60 mg/kg/day for 7 days starting on the third postoperative day; group 2 (42 patients) received no aspirin. Forty-eight patients (65%) developed an effusion during the study period, 3 required pericardiocentesis and 1 died of tamponade. All patients with tamponade had a grade 4 effusion. Age or type of operation did not alter the cumulative incidence of significant effusion. No patient with a grade 0 effusion on the first echocardiogram developed a grade 4 or 5 effusion. Results in groups 1 and 2 were similar. Pericardial effusions are common in the first month after cardiac surgery. Patients with no effusion in the immediate postoperative period appear to be at lesser risk of developing a grade 4 effusion in the first month after operation. Finally, aspirin prophylaxis against postoperative pericardial effusions did not significantly alter the outcome in this small series of patients.
In the setting of a single ventricle, subaortic stenosis may be enhanced by pulmonary artery banding and may later contraindicate a Fontan operation. The Norwood operation may prove a preferable alternative in some infants as a preparatory procedure. We have successfully used this procedure as the initial operation to palliate a newborn with tricuspid atresia, transposition of the great arteries, coarctation, and severe arch hypoplasia secondary to a restrictive bulboventricular foramen.
A 61-year-old man who had undergone aortocoronary bypass developed sternal osteomyelitis and mediastinitis which required sternal debridement and muscle flap interposition. Two years later the midline incision was used for an orthotopic heart transplantation. No major technical difficulties were encountered at the time of transplantation.
The authors report the extremely rare occurrence of a congenital abdominal aortic aneurysm, 6 cm in diameter, found in a 1-month-old infant. Prenatal ultrasonography at 34 weeks' gestation had shown the aneurysm, which at that time was interpreted as a renal cyst. At operation, an 8-mm polytetrafluoroethylene tube graft was interposed between the infrarenal aorta and the bifurcation. Cardiopulmonary bypass facilitated operative management by permitting return of blood lost and by maintaining body temperature. In a review of the literature, the authors could not find any report of a neonatal aneurysm of this magnitude. Regrettably, the cause of this true aneurysm remains obscure.
Early repair of complex congenital heart malformations may lead to life-threatening respiratory and hemodynamic embarrassment on sternal closure. To avoid a fatal outcome in these situations, we postponed sternal closure in nine critically ill neonates by suturing silicone elastomer sheeting to the skin edges. This maneuver, in a setting of optimal inotropic and ventilatory support, allowed eight of the nine neonates to survive. The mean age at operation was 10.2 days (range 3 to 31). The mean preoperative weight was 3004.4 gm (range 1550 to 3780). The sternal wound was protected with an impervious silicone elastomer sheeting for a mean of 5.6 days (range 2 to 12). There was no instance of wound infection. The judicious application of this technique after operations for complex congenital heart disease can provide the necessary compliance vital for immediate cardiopulmonary performance and ultimate survival.
A total of 466 neonates with transposition of the great arteries, all less than 15 days of age, have been entered into a 20-institution study between Jan. 1, 1985, and June 1, 1987. Seventy-three percent were less than 48 hours old when entered into the study. Two hundred twelve of these underwent an arterial switch repair, and the 1-week, 1-year, and 2 1/2-year survival rates were 82%, 79%, and 78%, respectively. The usual coronary anatomy was present in 67% of the patients. The arterial switch repair was performed in 16 of the institutions. Six among these were shown to be "low-risk" institutions, with the prevalence of the demographic and surgical variables seeming to be the same in these as in the other institutions. The 1-week, 1-year, and 2 1/2-year survival rates after the arterial switch repair in low-risk institutions for simple transposition were 96%, 91%, and 90%, respectively; for transposition with ventricular septal defect they were 84%, 83%, and 83%. Only older age at operation (over 14 days of age), in the case of simple transposition, and transposition with ventricular septal defect were risk factors for death in these six institutions. Among the patients as a whole, freedom from reoperation for pulmonary outflow obstruction at 1 week and 1 year was 99% and 89%, respectively. A previous pulmonary artery banding and, possibly, one institution were identified as risk factors for reoperation. Inferences: In low-risk institutions, the arterial switch repair can be accomplished with good early results, which suggests the possibility that the late results will be better than after the atrial switch repair. Since young age was not a risk factor for the arterial switch repair of transposition and ventricular septal defect, this type of repair for this anomaly, as well as for simple transposition, may be more advantageously performed early in life than at 2 to 3 months of age.
This report documents four instances of right atrial thrombi discovered from four days to five years after Fontan-type operations. Two of the thrombi were removed at reoperation, and two diminished in size during anticoagulation therapy. There were no pulmonary emboli in this small series, but the ominous implications of right atrial thrombi in the post-Fontan situation are obvious. For this reason we recommend regular echocardiographic surveillance of all patients who have had the Fontan operation and anticoagulation in certain situations.
A concept of management of pulmonary atresia in infancy has been presented. The basic theme employed is that pulmonary valvotomy or an outflow patch should be applied to most infants so that a biventricular heart is achieved in as many children as possible. Clearly, a functioning right ventricle cannot result in all instances and systemic to pulmonary shunts have an important adjunctive and sometimes primary therapeutic role. Our ability to judge right ventricular capability has been improved by preoperative assessment of segmental cavitary hypoplasia by noninvasive echocardiography and angiographic techniques.
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To assess the changes in resting left ventricular (LV) function following coronary bypass surgery, technetium 99m-labeled multiple equilibrated blood pool gated scans were performed in 53 consecutive patients at rest, before operation, and at 24 hours and 1 week after operation. Left ventricular ejection fraction (LVEF) and end-diastolic volume (EDV) were measured. The LVEF increased significantly from a preoperative value of 49 +/- 2% to 56 +/- 2% at 24 hours after operation (p less than 0.05) and 56 +/- 2% at 1 week following operation (p less than 0.05 compared with the preoperative value). The EDV also exhibited significant changes, decreasing from a preoperative value of 148 +/- 8 ml to 91 +/- 11 ml at 24 hours (p less than 0.001) and 114 +/- 9 ml at 1 week (p less than 0.01 compared with the preoperative value). When the patients were divided into two groups according to the preoperative LVEF (Group 1, LVEF of greater than or equal to 50%; Group 2, LVEF of less than 50%), the observed changes were similar. This study demonstrates significant improvement in resting LV function 24 hours following coronary bypass surgery. This improvement persists at 1 week and is not related to the degree of preoperative impairment. We conclude that the combination of successful revascularization and optimal myocardial protection can result in significant improvement of LV function at rest.
Congenital cardiac shunts produce pathological lesions on the arterial side of the lung vasculature. We examined the effects of chronic shunts (14.2 +/- 1.2 mo) in 10 young dogs, between the left subclavian and the left lower lobe (LLL) artery, on pulmonary vascular pressure and flow (P-Q) relationships, segmental resistance with arterial and venous occlusion (AVO), and sensitivity to drugs. At final thoracotomy, mean LLL pulmonary arterial pressure (Ppa) was 23.2 +/- 4.3 mmHg compared with 11.9 +/- 0.9 in the right lung (P less than 0.05); two animals had LLL Ppa of 41 and 48 mmHg. The LLL artery and vein were cannulated, and pressure-flow (P-Q) and AVO measurements were made and compared with previous control LLL (n = 11) and contralateral right lower lobe (RLL, n = 5). Responses to serotonin, histamine, and vasodilators (diltiazem and isoproterenol) were evaluated. Comparisons of morphometric measurements were made between LLL and RLL. We found a significant increase in arterial resistance as measured with AVO and a hypersensitivity to serotonin in the shunt LLL, without changes in total pulmonary vascular resistance or P-Q measurements; vasodilators had a small effect only in the hypertensive lobes. Our data suggest that chronic shunts to the pulmonary circulation increase arterial resistance and sensitivity to serotonin, even in the absence of discernible morphometric changes, and that vasoconstriction may be an important precursor to the development of morphological lesions.
Chylopericardium is one of the rarest complications of cardiac surgery. The authors report only the 19th case, that of a 12-year-old boy. The chylopericardium developed after an aortic valvotomy, even though the retropericardial portion of the mediastinum was entered only to pass a tape around the ascending aorta. Etiologic factors are directly or indirectly related to injury to the thoracic duct or tis tributaries. Treatment initially is conservative, consisting of adequate pericardial drainage and a low-fat, medium-chain triglyceride diet. If this fails, the appropriate operative procedure is carried out.
The spatial distribution of radioactively labeled microspheres was studied in normal and in experimentally hypertrophied hearts of adult pigs. The hearts had been "tagged" with microspheres when the pigs were young. When the adult animal was killed, the spatial distribution of the microspheres was identical in the normal and in the hypertrophied hearts. This demonstrates that hypertrophic growth had occurred evenly throughout all layers of the myocardium.
Left ventricular hypertrophy was created in 15 pigs by banding the ascending aorta when they were young. The adult animals were placed on normothermic cardiopulmonary bypass and perfused with either nonpulsatile (two groups of pigs) or pulsatile (one group) flows. As long as the perfusion rate was maintained at 70 ml/kg/min, myocardial blood flow distribution as determined by radioactive microspheres, was identical in the hearts with normal sinus rhythm and those with ventricular fibrillation irrespective of the type of perfusion. At low flow rates, however, subendocardial ischemia developed in all three groups, but was most severe in the fibrillating hearts, and was not reversed by pulsatile perfusion.
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