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Biomedical subjects

R D Mainwaring

Publications and source records attributed to R D Mainwaring.

At least 37 records · Page 2Linked to original sources
PubMed1994

Damus-Kaye-Stansel procedure: midterm follow-up and technical considerations.

The Damus-Kaye-Stansel operation is useful in the management of complex congenital heart defects. We reviewed our experience with 23 patients who underwent a Damus-Kaye-Stansel procedure. The anastomotic technique was individualized depending on the anatomy. The aortic and pulmonary artery incisions were carried into the sinuses of Valsalva in 9 patients, the aorta was transected in 11 patients, and a patch was used to augment the anastomosis in 13 patients. Concurrent procedures included a Fontan operation (n = 9, mortality = 0), right ventricle-pulmonary artery conduit (n = 5, mortality = 0), bidirectional Glenn procedure (n = 6, mortality = 1), and central aortopulmonary shunt (n = 3, mortality = 2; emergency = 1). Survival is 87% with a median follow-up of 7 years (range, 2 months to 9.2 years). Four patients underwent late revision of the Damus-Kaye-Stansel connection. All survivors are asymptomatic. We conclude that the Damus-Kaye-Stansel connection provides excellent midterm results when the proximal anastomosis is adapted to the anatomy of the patient.

Anastomosis, Surgical↗
PubMed1994

Airway compromise secondary to vascular compression in a neonate.

Respiratory distress in the neonate may be due to extrinsic tracheobronchial compression. We recently observed a neonate with left mainstem bronchus obstruction resulting in respiratory distress and mediastinal shift. Initial management required intubation and positive pressure ventilation. Bronchoscopic evaluation demonstrated compression of the proximal left main bronchus. The distal bronchus appeared normal. Bronchography, echocardiography and an MRI of the chest confirmed proximal compression of the bronchus and suggested that the cause was an aneurysmal left pulmonary artery and patent ductus arteriosus. With medical therapy there was resolution of the bronchial compression. Re-evaluation by bronchoscopy and echocardiography revealed a normal left main stem bronchus, a normal left pulmonary artery and a closed ductus arteriosus. This clinical scenario suggests that transient pulmonary hypertension may result in significant airway compression due to the proximity of the left main stem bronchus to the left pulmonary artery.

Aneurysm↗
PubMed1994

Management of mycotic aneurysm following repair of corrected transposition.

Omental flaps have been used for the treatment of infected aortic prosthetic grafts in adults. We report the case of a 26-month-old male who developed a mycotic aneurysm 9 months following insertion of a ventricle to pulmonary artery conduit. The aneurysm was excised and the reconstructed outflow tract wrapped with omentum. The patient has not had recurrence of his aneurysm following this course of management.

Aneurysm, Infected↗
PubMed1994

Reduction in triiodothyronine levels following modified Fontan procedure.

Diminished cardiac function is a common manifestation following the modified Fontan procedure. Since thyroid hormone has important effects on cardiovascular function, the present study was undertaken to evaluate changes in thyroid hormone levels following this operation. A control group consisting of children undergoing open heart procedures other than a Fontan procedure was also evaluated. Serum total and free triiodothyronine (T3), total and free thyroxine (T4), thyroid stimulating hormone (TSH), and thyroglobulin were measured by immunoassays. The Fontan group demonstrated an initial increase in free T4, while free T3, total T3, total T4, TSH, and thyroglobulin were reduced. Over the subsequent days, free T4 decreased to below the preoperative value. By the fifth and eighth postoperative days, free T3, total T3, free T4, and total T4 remained reduced, while TSH and thyroglobulin began increasing toward the preoperative levels. The control group also demonstrated decreases in free T3 and TSH. However, these values had returned to baseline by the fifth postoperative day. The results indicate that children undergoing open heart surgery have suppression of the pituitary-thyroid axis, and that this is prolonged in patients undergoing Fontan procedure. The decreased levels of T3 following Fontan procedure may have adverse effects on the recovery of patients undergoing this operation.

Atrial Function↗
PubMed1993

Management of absent pulmonary valve syndrome with patent ductus arteriosus.

The etiology of absent pulmonary valve syndrome is unknown. Several theories have been advanced to explain the associated findings of a rudimentary pulmonary valve, ventricular septal defect, aneurysmal pulmonary arteries, and absence of the ductus arteriosus. The patient presented here would contradict these currently held theories. A review of the literature follows the case report.

Abnormalities, Multiple↗
PubMed1993

Neck cannulation for the repair of thoracic artery aneurysms in the infant.

Thoracic aneurysms are relatively rare in infancy. We report our experience with two such patients, one with a false aneurysm of the ascending aorta and the other with a mycotic aneurysm of the main pulmonary artery. Neck cannulation prior to sternotomy, using cannulae designed for extracorporeal membrane oxygenation, allowed entry into the mediastinum under controlled circumstances and permitted the successful repair of the aneurysms.

Aneurysm, False↗
PubMed1993

Management of systemic atrioventricular valve regurgitation in infants and children.

Since September 1979, 53 patients have required operation for systemic atrioventricular valve regurgitation at Children's Hospital and Health Center of San Diego. (Primary repairs of atrioventricular canal defects are excluded from this report.) Diagnoses include single ventricle, cardiomyopathy, congenital mitral insufficiency , Marfan's disease, rheumatic heart disease, and a history of prior repair of atrioventricular canal defect. Ages ranged from 4 months to 19 years; median age is 5 years. In 31 patients, the atrioventricular valve could be repaired. In 24 patients, the valve was replaced (including two patients previously repaired). There were four operative deaths, all in the valve replacement group: three following valve replacement, and one following emergency thrombectomy. Two early failures in the repair group required valve replacement. Techniques for repair included leaflet resection, commissural annuloplasty, ring annuloplasty, and chordal shortening. Follow-up reveals good-to-excellent status in 38 patients. There were seven late deaths: six following valve replacement (one death valve related). Current surgical technique permits repair of the systemic atrioventricular valve in many infants and children requiring operation for regurgitation. The long-term results of valve repair are good to excellent. Repair avoids the morbidity and mortality of valve replacement, e.g., anticoagulation, fixed orifice size, and catastrophic mechanical valve malfunction.

Actuarial Analysis↗
PubMed1993

Pulmonary atresia with intact ventricular septum. Surgical approach based on ventricular size and coronary anatomy.

Pulmonary atresia with intact ventricular septum has continued to have a high surgical mortality. This may relate to the nonuniformity of the anomaly. We have developed a management algorithm based on the right ventricular size and coronary anatomy. Patients with a well-developed ventricle and normal coronary arteries have undergone right ventricular outflow procedures. The adequacy of their right ventricles is subsequently evaluated; some patients are candidates for a four-chamber repair, whereas others are candidates for a Fontan procedure. Patients with severe hypoplasia of the right ventricle frequently have extensive ventriculo-coronary connections, and for these patients we have developed the technique of right ventricular obliteration. Over the past 7 years, we have treated 20 patients with pulmonary atresia with intact ventricular septum. Fourteen of the 20 patients underwent outflow tract procedures, with no operative mortality. There were two late deaths in this group. Six patients had hypoplasia of the ventricle with ventriculo-coronary connections and underwent right ventricular obliteration. There was one operative death and one late death in the group. Overall, 95% survived the neonatal period, and 80% were still alive at the time this article was written with an average follow-up of 32 months. We conclude that pulmonary atresia with intact ventricular septum can be successfully managed with the use of an algorithm based on ventricular size and coronary anatomy.

Cardiac Surgical Procedures↗
PubMed1992

Omental transfer for the treatment of mediastinitis in an infant.

Mediastinitis following congenital heart surgery is relatively uncommon but is usually seen in the setting of postoperative low cardiac output. Conservative treatment utilizing debridement and irrigation is associated with significant morbidity and mortality. We report the successful application of the omental transfer technique in the treatment of mediastinitis in a 6 month old.

Cardiac Surgical Procedures↗
PubMed1992

The cardiac illness of General Robert E. Lee.

We believe that General Robert E. Lee had ischemic heart disease. It is our opinion that he sustained a heart attack in 1863 and that this illness had a major influence on the battle of Gettysburg. Lee experienced relatively good health from 1864 to 1867, but by 1869 he had exertional angina and by the spring of 1870 had intermittent rest angina. Although his symptoms were typical of angina, his physicians consistently diagnosed pericarditis, which we believe was erroneous. This misdiagnosis can be explained by the lack of familiarity of American physicians with angina during the 19th Century. It often was stated that the loss of the war broke the heart of Lee, but in view of our modern day understanding, it probably is more accurate to say that advancing coronary atherosclerosis was the culprit.

Famous Persons↗
PubMed1991

The Damus-Fontan procedure.

The Damus-Kaye-Stansel operation is a useful technique for the treatment of complex cyanotic congenital heart disease when there is obstruction between the systemic ventricle and the aorta. Modifications of the technique include transection of the aorta and the pulmonary artery, anastomosis of the contiguous aortic and pulmonary walls, and connection of the distal aorta to the perimeter of the new bivalved proximal great artery. In addition, the bidirectional cavopulmonary shunt technique can be used with or without the Fontan procedure. Six patients underwent a Damus-Fontan operation, and all survived. Two patients underwent the Damus-cavopulmonary shunt (hemi-Fontan) procedure, and 1 survived. The postoperative status of the 7 survivors is good to excellent. Follow-up ranges from 2 months to 7 1/2 years.

Anastomosis, Surgical↗
PubMed1991

The cryopreserved homograft valve in the pulmonary position: mid-term results and technical considerations.

Since September 1985, 60 cryopreserved homograft valves (12 aortic and 48 pulmonary) have been implanted in the pulmonary position in 56 patients. There were 34 primary operations and 26 reoperations. The ages ranged from 15 days to 22 years; the follow-up ranged from 1 month to 5 1/2 years. The operative mortality was 3.3% (2/56). There were two late deaths (not valve related). Five patients underwent replacement of the homograft; in one patient the homograft was replaced with a heterograft valve. Pathological analysis of the explanted homografts revealed calcification of the wall with satisfactory leaflet function. The leaflets were relatively acellular. No evidence of inflammation or rejection was detected. Four explants were performed for nonvalve-related indications. There are 51 long-term survivors with a homograft in place. Forty-eight are in excellent condition; three are mildly symptomatic (not valve related). Benign pulmonary insufficiency murmurs are present in 29 patients. The presence of trivial or mild insufficiency was independent of the technique of implantation. In general, cryopreserved homograft valves function well in the right ventricular outflow tract. Longer term follow-up is necessary to confirm the superiority of the cryopreserved homograft when compared to the porcine heterograft in the right ventricular outflow tract.

Adolescent↗
PubMed1990

The in utero left ventricle of the fetal sheep: the effects of isoprenaline.

1. Isoprenaline was infused into in utero fetal lambs to examine the effect of this beta-adrenoceptor agonist on left ventricular stroke volume and left ventricular output and test the generally held assumption that the fetal ventricle is markedly limited in its ability to increase ventricular output. 2. Seven in utero lambs (121-133 days of gestation) were instrumented with left ventricular dimension transducers, an ascending aortic electromagnetic flow transducer, a brachiocephalic arterial catheter and electrocardiographic and atrial pacing electrodes. 3. On the day of study, 5-8 days following surgery and 129-137 days of gestation, each lamb received infusions of isoprenaline, via the superior vena cava or left atrium, at rates which ranged from 0.005-0.5 microgram kg-1 min-1. 4. Heart rate and left ventricular stroke volume, output and end-diastolic and end-systolic dimensions were measured under control conditions and during various levels of isoprenaline infusion, with and without controlling heart rate. 5. Analysis of variance was done using the mean cell model. Least-square means and standard errors of the least-square means are reported. F ratios were calculated from type III sums-of-squares; P less than 0.05 was considered significant. 6. The mean heart rate increased with isoprenaline (P less than 0.0001) from a mean control level of 169 +/- 8 to 281 +/- 9 beats min-1 (+/- S.E.M.). 7. Mean left ventricular end-diastolic and end-systolic minor axis dimensions decreased significantly with isoprenaline from 16.7 +/- 0.1 mm (control) to 15.7 +/- 0.2 mm (P less than 0.0004) and from 11.7 +/- 0.1 mm (control) to 10.4 +/- 0.2 mm (P less than 0.0001) respectively. When heart rate was controlled with atrial pacing, mean end-diastolic dimension increased significantly at the higher isoprenaline doses from 14.6 +/- 0.1 mm (control) to 15.3 +/- 0.2 mm (control) (P = 0.0002), while mean end-systolic dimension fell significantly from 10.9 +/- 0.1 to 10.5 +/- 0.1 mm (P less than 0.003). Inasmuch as stroke volume increased, the increase in end-diastolic dimension and the fall in end-systolic dimension indicate an increase in venous return to the left ventricle. 8. During spontaneous rhythm, isoprenaline increased stroke volume from 2.45 +/- 0.06 ml (control) to 2.63 +/- 0.09 ml, not statistically significant. When heart rate was controlled, stroke volume increased with isoprenaline dose from 1.68 +/- 0.06 ml (control) to 2.40 +/- 0.08 ml (P less than 0.0001).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Synchronous hepatocellular carcinoma and adenocarcinoma of the colon.

It is not uncommon for patients with colon cancer to have a second primary neoplasm. The reported incidence of synchronous colon tumors is approximately about 3 to 4 per cent. Colon cancer also may be associated with a synchronous extra-colonic neoplasm; this incidence is less well defined and certainly is less emphasized in the literature. The authors recently treated a patient who had a synchronous hepatoma and adenocarcinoma of the colon. This appears to be the first report of these tumors presenting synchronously. The patient had both tumors resected and has no evidence of recurrence ten months later. This case illustrates the need to seek both colonic and extra-colonic synchronous tumors in patients discovered to have a colon cancer.

Adenocarcinoma↗
PubMed1988

Myocardial reactive hyperemia in the newborn.

Adenosine may be an important metabolic regulator of coronary blood flow during active hyperemia in the newborn. In this study, the adenosine uptake blocker dipyridamole (DPY) and receptor antagonist theophylline (THEO) were used to assess the role of adenosine in the reactive hyperemic response of the neonatal heart. Eighteen anesthetized, open-chest lambs were instrumented with aortic and coronary sinus catheters as well as an extracorporeal shunt to the circumflex coronary artery incorporating a 2.0-mm electromagnetic flow transducer. Ten-second occlusions of the circumflex coronary artery catheter were performed, and the resulting reactive hyperemia was used to determine peak hyperemic blood flow (PHF), duration of hyperemia, and the blood flow repayment. These values were determined prior to treatment and 30 min following administration of a saline vehicle, DPY (0.2 mg/kg) or THEO (5 mg/kg). DPY resulted in increases in PHF from 220 +/- 12 to 247 +/- 14 ml/min/100 g heart tissue (P less than 0.05), durations of hyperemia from 29 +/- 2 to 38 +/- 2 sec (P less than 0.01), and blood flow repayments from 65 +/- 2 to 102 +/- 4 ml/100 g (P less than 0.001). THEO resulted in decreases in PHF from 224 +/- 15 to 198 +/- 12 ml/min/100 g (P less than 0.05), durations of hyperemia from 28 +/- 2 to 22 +/- 2 sec (P less than 0.05), and blood flow repayments from 64 +/- 2 to 46 +/- 2 ml/100 g (P less than 0.01). The data indicate that DPY enhances reactive hyperemia while antagonism of adenosine with THEO attenuates it. These results suggest that adenosine plays a role in mediating reactive hyperemia in the newborn heart.

Adenosine↗
PubMed1987

In utero right ventricular output in the fetal lamb: the effect of heart rate.

1. The effect of heart rate on right ventricular output was examined in six lambs during a period extending from 126 to 139 days of gestation. The fetuses had been surgically instrumented at least four days previously with a main pulmonary artery flow probe, right ventricular dimension transducers and left and right atrial pacing electrodes. 2. During spontaneous variations in heart rate, rate was correlated positively with right ventricular output (P less than 0.0001) and end-diastolic dimension (P less than 0.0001) among the lambs considered as a group, but no significant effect of rate on stroke volume was found. When individual responses were examined, output increased significantly with rate in sixteen out of seventeen observations. 3. With left atrial pacing, heart rate did not affect output. With right atrial pacing, rate correlated negatively with output (P less than 0.0001). With pacing from either site, rate correlated negatively with end-diastolic dimension (P less than 0.0001) and stroke volume (P less than 0.0001). 4. The introduction of a longer period interval during each pacing rate inhibited the rate-related decrease in dimension and allowed the ventricle to fill to the same end-diastolic dimension. The systole following these longer intervals had a greater stroke volume than did the preceding systoles with smaller end-diastolic dimension. The faster the preceding paced rate, the greater was the increase in stroke volume (P less than 0.001). 5. Right ventricular dimensions and volumes were measured in vitro, and the relationship was found to be linear using regression analysis. 6. This study demonstrates that experimentally induced variations in heart rate produce changes in end-diastolic volume and contractility which prominently affect right ventricular stroke volume. As a consequence, rate has, over a broad range, either no significant effect on output or a negative one. With spontaneous variations in rate, additional changes in contractility and venous return occur which affect stroke volume and end-diastolic volume and enhance right ventricular output. These relationships are similar to those in the adult heart, and demonstrate the absence of a maturational change in the effects of rate on ventricular function from the fetus to the adult.

Animals↗
PubMed1986

Effects of dipyridamole on myocardial glucose uptake in the newborn lamb.

Carbohydrates are an important source of energy for the immature myocardium. Since dipyridamole (DPY) has been reported to facilitate glucose uptake in the adult heart, the present study was designed to determine whether DPY could enhance glucose uptake in the nonischemic newborn. In anesthetized, open chest lambs (n = 8), circumflex coronary blood flow (CBF), myocardial adenine nucleotide content, and aortic and coronary sinus concentrations of glucose, lactate, and pyruvate were determined before and after a single dose of DPY (0.2 mg/kg, intravenously). Adenine nucleotides were measured by HPLC. The consumption of substrates was calculated as the product of CBF and the aortic-coronary sinus difference in substrate concentration. Coronary blood flow averaged 114 +/- 6 ml/min/100 g in the untreated animals, and increased by 44% following treatment with dipyridamole (P less than 0.01). This was associated with a 32% decrease in coronary vascular resistance (P less than 0.01). Glucose uptake increased from 9 to 46 mumoles/min/100 g (P less than 0.01) following dipyridamole treatment; lactate uptake decreased by 97% (P less than 0.01). There was a net release of pyruvate from the neonatal hearts; this increased from 18 to 25 mumole/min/100 g (P less than 0.05). Myocardial ATP content averaged 4.08 mumole/g wet wt in the untreated animals, and increased 11% to 4.52 following DPY (P less than 0.01). The agent had no effect on the myocardial tissue levels of AMP or ADP. These data indicate that DPY is a coronary vasodilator in the newborn lamb and augments both glucose uptake and myocardial ATP content. These metabolic effects provide a rationale for further studies during periods of hypoxia and ischemia.

Adenine Nucleotides↗