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Biomedical subjects

R B Mee

Publications and source records attributed to R B Mee.

90 records · Page 5Linked to original sources
PubMed1987

Surgical repair of hemitruncus: principles and techniques.

Ten patients have presented at the World Children's Hospital of Melbourne with hemitruncus, a form of truncus arteriosus. Nine of these patients underwent successful one- or two-stage hemodynamic repair. Early repair is carried out to avoid pulmonary vascular disease of the lung directly supplied from the trunk and to recruit as much of the contralateral pulmonary artery vasculature bed as possible is a secondary goal. The repair should be contemplated within the first six months of life to prevent severe pulmonary vasculature obstructive disease. Anatomy that is repairable in one stage is when the left pulmonary artery originates from the trunk and the complete right pulmonary artery supplied by pulmonary collaterals from the arch to the descending aorta. Anatomy requiring two-stage repair occurs when the RPA rises from the trunk and the left PDA rises from the descending aorta or distal aortic notch and either the right or the left lung blood supply is from multiple origins and requires unifocalization. With these anatomical principles and the general meticulous perioperative and postoperative care of the infants, a high degree of success should be obtainable with repair of this hemitruncus.

Child, Preschool↗
PubMed1986

Complete atrioventricular canal associated with tetralogy of Fallot or double-outlet right ventricle and right ventricular outflow tract obstruction: a report of successful surgical treatment.

Six patients, 4 of whom had complete atrioventricular (AV) canal and tetralogy of Fallot (TOF) and 2 of whom had double-outlet right ventricle with subaortic ventricular septal defect (VSD) and right ventricular outflow tract obstruction, were treated. Two of the patients with complete AV canal and TOF had a shunt procedure only. The other 4 patients underwent complete repair. All 6 patients survived the operation. Complete repair was performed through the right atrium using the two-patch technique. The size and shape of the VSD patch is important. Residual VSD after repair was common. Two patients have undergone successful reoperation for this problem. Another patient has a small residual VSD.

Child↗
PubMed1986

Pulmonary atresia with intact ventricular septum.

Neonates with pulmonary atresia with intact ventricular septum are ductus dependent from birth. The initial approach in these patients is to ensure continued adequate pulmonary blood flow in anticipation of imminent spontaneous closure of the ductus. Our experience and evolving approach in the management of 16 consecutive neonates with pulmonary atresia with intact ventricular septum from 1978 to 1984 is presented. On the basis of the revised classification by Bull and associates, we divided the patients into four different groups according to right ventricular morphology. Basically, three types of palliative surgical procedures were performed: systemic-pulmonary artery shunt; systemic-pulmonary artery shunt with pulmonary valvotomy; and pulmonary valvotomy alone. Systemic-pulmonary artery shunt is the most important part of neonatal palliation. Our present routine is to perform left subclavian-main pulmonary artery shunt with a polytetrafluoroethylene tube in all patients and, in addition, to perform an open transpulmonary valvotomy without cardiopulmonary bypass in patients with a patent infundibular portion of the right ventricle. Our technique and the advantages of this type of shunt procedure are discussed. Patients with right ventricular sinusoidal-coronary artery communications are a subgroup with an additional problem. In our series, patients with this anomaly are categorized into groups with major and minor connections and their surgical significance is discussed. Overall, there was one death among 16 patients after neonatal palliative procedures and one death among five patients after hemodynamic repair.

Echocardiography↗
PubMed1986

Pulmonic regurgitation and reconstruction of right ventricular outflow tract with patch. An experimental study.

Twenty-five dogs were divided into three experimental groups. In each animal of Group I (10 dogs), one pulmonary valve leaflet was resected and a monocusp-bearing bovine pericardial patch was sewn into the right ventricular outflow tract. The monocusp was retracted to the patch with plicating sutures, and when the sutures were removed the monocusp became functional. In each animal of Group II (10 dogs), an incision was made in the right ventricular outflow tract along the anterior pulmonary valvular commissure and a bovine pericardial patch of adjustable width (one half, one, or one and one half times the diameter of the pulmonary valve ring) was sewn into the incision. Group III (five dogs) was the control group. During each situation of altered pulmonary valve function, in each experimental animal, the pulmonary blood flow and intracardiac pressures were measured. Pulmonary regurgitation was expressed regurgitant fraction (retrograde flow divided by net forward flow). We reached the following conclusions: In all situations where pulmonary incompetence was created, the regurgitant fraction was related directly to the width of the patch and was usually not more than half of the net forward flow when the width of the patch was less than one and a half times the pulmonary valve ring diameter. Regurgitant fraction was about half of net forward flow when one leaflet had been excised. The index of pulmonary artery diastolic pressure minus right ventricular end-diastolic pressure was sensitive and bore an inverse relationship to the degree of pulmonary regurgitation. An accurately placed monocusp-bearing patch restored pulmonary valve competence after excision of a cusp. In treating patients, we are encouraged to preserve as much pulmonary valve function as possible.

Animals↗
PubMed1986

Severe right ventricular failure after Mustard or Senning operation. Two-stage repair: pulmonary artery banding and switch.

Since early 1981 I have been banding the pulmonary arteries of patients in whom severe right ventricular dysfunction has developed after atrial repair of transposition of the great arteries. The purpose of banding is to "retrain" the left ventricle. Of the four patients so treated, two developed adequate left ventricular pressures and have successfully undergone an arterial switch and takedown of the atrial repair. The early results are impressive. Right ventricular function has returned to normal in both patients and tricuspid valve regurgitation has resolved. In one patient moderate aortic valve regurgitation also appears to have largely resolved.

Blood Pressure↗
PubMed1986

An in vitro study of the pharmacological and electrophysiological properties and the adrenergic innervation of small pulmonary arteries from children with pulmonary hypertension.

A study was made of the pharmacological and electrophysiological properties of pieces of small intrapulmonary arteries (100-450 micron I.D.) taken from children with cardiac defects that caused the pulmonary circulation to be exposed to an abnormally high perfusion pressure. The sensitivity of the arterial smooth muscle to the constrictor agonists acetylcholine and 5-hydroxytryptamine was similar to that reported for adult pulmonary arteries. Norepinephrine or histamine caused little or no constriction, although both these substances have been reported to be powerful constrictors of adult pulmonary arteries. The electrophysiological properties were similar to those of the smooth muscle of systemic arteries. The mean resting membrane potential was -6.12 mV +/- 1.29 (SEM n = 16). Stimulation of the perivascular nerves produced excitatory junction potentials, but no smooth muscle action potentials were recorded. Histochemical investigation revealed catecholamine containing nerve fibres around all intrapulmonary arteries down to 40 micron I.D.

Acetylcholine↗
PubMed1985

Non-invasive assessment of pulmonary blood supply after staged repair of pulmonary atresia.

Radionuclide studies were performed to determine pulmonary blood flow in six children who had undergone surgery for pulmonary atresia, ventricular septal defect, and hypoplastic pulmonary arteries with or without major aortopulmonary collateral arteries. Lung blood flow was assessed from both particle perfusion lung scans and the pulmonary and systemic phase of a radionuclide dynamic flow study. Five patients had perfusion defects identified on the particle perfusion lung scan. In three of these, abnormal areas were perfused only during the systemic phase of the flow study, a combination of findings that indicate the presence of perfusion by collateral arteries. In one patient no systemic perfusion was noted and in one an initial particle perfusion study indicated the presence of a lung segment perfused by a collateral artery. In this last patient the particle perfusion scan after total correction showed a reduction in the size of the lung perfusion defect and no evidence of lung perfusion during the systemic phase of the flow study. The particle perfusion lung scan in the sixth patient showed pronounced asymmetry in blood flow to the lungs with no segmental perfusion defect on the particle perfusion scan and no abnormalities on the systemic flow study. It is concluded that radionuclide lung perfusion and flow studies provide useful information on lung perfusion and merit further evaluation to define their role in the management of these patients.

Abnormalities, Multiple↗
PubMed1985

Perioperative management of neonatal aortic isthmic coarctation.

Aortic isthmic coarctation is a common cardiovascular cause of neonatal mortality. This study reviews retrospectively sixty-one consecutive neonates operated on for this condition at the Royal Children's Hospital, Melbourne, in the years 1978-1983 inclusive. In this series, the overall mortality has fallen from 50% and 67% in 1978 and 1979 respectively, to 11% in 1983. In the last three years of this review, there have been no early hospital deaths and the late deaths relate to associated congenital anomalies. The decrease in mortality is ascribed to methods of perioperative support, non-invasive cardiac investigation, and surgical repair with subclavian aortoplasty. Prior to surgery, all infants are paralysed, mechanically ventilated and infused with prostaglandin E1 to reopen the ductus arteriosus, and dopamine to support the failing myocardium. The physical status of all infants improved with these maneuvres. This paper reviews the pathophysiology of neonatal aortic coarctation, the current modes of management, results and complications.

Alprostadil↗
PubMed1985

Truncus arteriosus. Surgical approach.

Between mid-1979 and December, 1983, 23 patients with various types of truncus arteriosus underwent total surgical correction at Royal Children's Hospital, Melbourne, Australia. Nineteen patients had primary total repair and four had secondary repair, three having survived banding done prior to 1978. Sixteen patients were less than 1 year of age. Repair was performed with circulatory arrest in infants and cardiopulmonary bypass with core cooling in older patients. Patients were electively ventilated preoperatively. In the postoperative period, pulmonary artery pressure was monitored very closely and any rise was treated with hyperventilation and vasodilators. Two patients under 1 month of age, who were severely acidotic and anuric preoperatively, died of low output syndrome. Among the rest of the infants there was only one death, probably because of pulmonary hypertensive crisis that might have been prevented. From our experience, we think that patients with truncus arteriosus should have total correction during infancy, preferably at 2 to 3 months of age, as it can be performed with a very low risk and also avoids the development of pulmonary vascular disease, which occurs very rapidly in these infants.

Blood Pressure↗
PubMed1983

Surgical treatment of absent pulmonary valve syndrome in infants: relief of bronchial obstruction.

Congenital absence of the pulmonary valve is usually associated with a malalignment type of ventricular septal defect as well as right ventricular outflow obstruction and aneurysmal dilatation of the pulmonary arteries. Symptomatic infants primarily have severe tracheobronchial obstruction caused by aneurysmal dilatation of the proximal pulmonary arteries; pulmonic and systemic blood flow are usually balanced. Surgical intervention to relieve the obstruction by plicating the pulmonary artery and its branches under deep hypothermia and circulatory arrest, together with patch closure of the ventricular septal defect, is advocated.

Airway Obstruction↗
PubMed1980

Reintroduction of the Senning operation for transposition of the great arteries.

At the Royal Children's Hospital, Melbourne, since November, 1978, the Senning operation has become the operation of first choice, in place of the Mustard procedure, for transposition of the great arteries. In total of 22 patients, there have been three hospital deaths, two of which were attributable to severe pulmonary vascular disease. There have been no deaths. Because the Senning procedure is based on the use of living tissue, it may provide better long-term results, by permitting growth and thus avoiding late systemic or pulmonary venous obstruction, than the Mustard procedure which employs extensive use of prosthetic material or graft.

Child, Preschool↗
PubMed1979

Long-term follow-up of the Hancock bioprosthetic heart valve: a 6-year review.

Clinical experience with the Hancock porcine bioprosthetic heart valve was reviewed in 467 patients (254 men and 213 women, 18--84 years old, average, 56 years) who received 528 valves from January, 1972, to January, 1978. Associated procedures, including coronary bypass graft, ascending aortic aneurysm, and valvuloplasty were done in 102 of the 467 patients (22%). The overall operative mortality was 25/467 (5.6%), 12/226 (5.3%) for aortic valve replacement (AVR), 11/183 (6%) for mitral valve replacement (MVR), and 2/58 (3.4%) for multiple valve replacement. The first 323 patients with a minimum follow-up of 16 months (16--75 months, average 33 months) were analyzed for survival and thromboemboli. Actuarial survival at 66--75 months was 75.7% for AVR, 79% for MVR, and 75.8% for multiple valve replacement. Emboli per 100 patient-years was 0.55 for AVR (no anticoagulants), 3.9 for MVR, and 4.8 for multiple valve replacement (anticoagulants for atrial fibrillation patients only); emboli occurred only in patients with atrial fibrillation. There were seven of 528 primary dysfunctional valves (1.3%): calcification in two, tissue failure in two, and fibrosis in three. A hemodynamic study of four patients with a 21 mm Hancock Modified Orifice aortic valve prosthesis showed improved orifice areas (greater than 1.3 cm2) over the standard aortic valve. The Hancock porcine xenograft bioprosthetic heart valve has been a durable heart valve in excess of 6 years and has a low associated incidence of thromboemboli in patients off anticoagulants except in those with chronic atrial fibrillation.

Adolescent↗
PubMed1978

Changing indications for the surgical treatment of unstable angina.

From 1970 to 1977, 127 patients were operated on for unstable angina. On the basis of response to intensive medical therapy, patients were classified into a medically controlled, semielective surgery group (54 patients) and a medically uncontrolled, emergent/urgent surgical group (73 patients). There were five operative deaths. 1/54 in the medically controlled group (1.8%) and 4/73 (5%) in the medically uncontrolled group; 4/5 operative deaths occured with left main coronary stenosis. There were five late deaths during a follow-up period of 12 to 84 months, 37.5 with an actuarial survival of 83.5%. If patients with unstable angina can be medically controlled, operation can be delayed and the operative long-term survival is similar to that of elective coronary bypass. Patients who cannot be controlled medically, particularly those with left main coronary lesions, should be operated on urgently with selective use of preoperative balloon support.

Adult↗
PubMed1978

Late results of operation for acute aortic dissection producing aortic insufficiency.

Since July, 1970, 8 patients with acute dissecting aneurysms of the ascending aorta producing aortic insufficiency have undergone immediate operation employing a technique in which the origin of the dissection is resected, the dissected base of the aorta is lined with nondistensible prosthetic cloth for support, and the native aortic valve is resuspended. Aortic continuity is then reestablished with end-to-end anastomosis or use of a short segment of woven graft (not necessarily circumferential). There were no operative deaths. Mean follow-up has been 60 months (range, 25 to 82 months). One late death has occurred (cerebral hemorrhage at 48 months); of the remaining 7 patients, 2 have faint murmurs of aortic insufficiency, but all are in New York Heart Association Functional Class I. This technique of aortic reconstruction in acute ascending dissections allows preservation of the native aortic valve while preventing late aortic root dilatation or major valve insufficiency.

Adult↗
PubMed1978

Conservative management of uremic pericardial effusions.

Although there has been a recent trend toward early operative treatment of uremic pericardial effusions unresponsive to intensified dialysis, this approach may be unnecessarily aggressive. Review of 787 patients in our chronic dialysis program since 1969 has shown 54 patients (6.9 percent) to have developed 56 episodes of large pericardial effusion. All were managed by increasing the frequency of dialysis. If the effusion failed to diminish or if life-threatening signs of tamponade developed, pericardiocentesis was performed. In 63 percent (35/56) the effusion resolved with increased dialysis. In 37 percent (21/56), pericardiocentesis was performed, with 57 percent (12/21) requiring only one aspiration. During a mean follow-up of 34 months (2 to 100 months) only 5.5 percent (3/54) have undergone operation: one partial pericardiectomy incidental to pulmonary decortication and two pericardiectomies for late (3 months and 5 months, respectively) constriction. There were five complications of pericardiocentesis: one pneumothorax, one pneumoperitoneum, one costochondritis, and two myocardial punctures without sequelae. The one death related to pericardial effusion in this series occurred in a home-dialysis patient who arrived in the emergency room moribund. Our experience suggests that the great majority of uremic pericardial effusions can be effectively controlled with simple needle aspiration by experienced personnel and that pericardial resection is usually not necessary.

Adolescent↗