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Biomedical subjects

R K Lamb

Publications and source records attributed to R K Lamb.

At least 37 records · Page 2Linked to original sources
PubMed1995

Use of larger sized aortic homograft conduits in right ventricular outflow tract reconstruction.

Between 1973 and 1993 sixty aortic homograft valved conduits in fifty-six patients were used to establish continuity between the right ventricle and the pulmonary artery in congenital heart disease. Age range was one day to 23.5 years (median 3.6 years) which included twenty-six patients less than one-year-old. Conduit size ranged from 11 to 23 mm (median 17.6 mm). there were nine hospital deaths and eight late deaths. The 45 survivors have been followed for a median of 8.6 years (range 6 months to 20 years). All patients have had serial echocardiographic assessments and 35 have had post repair cardiac catheterization. Almost all patients had mild-to-moderate degrees of homograft regurgitation. There were eleven with severe homograft regurgitation and two are being considered for reoperation. The follow up homograft gradient ranged from 0 to 64 mmHg (mean 24 mmHg). Freedom from reoperation for conduit obstruction was 98.2% at five years falling to 91% (C.L. 82%-100%) at 10 years. Of the 23 homografts inserted more than 10 years ago, only one (4.3%) has been replaced because it was causing important obstruction. None have been replaced for regurgitation. Our results indicate that larger sized aortic homografts used in reconstruction of the right ventricular outflow tract give satisfactory results and there is a low incidence of reoperation for replacement at medium term follow up.

Aortic Valve↗
PubMed1994

Unusual left atrial mass following cardiac surgery in an infant.

An unexpected left atrial mass was found during routine postoperative transthoracic echocardiogram in an infant following surgical closure of ventricular septal defect. Thrombus could not be excluded. At reoperation it was found to be an inverted left atrial appendage. This case demonstrates the echocardiographic appearance of an inverted left atrial appendage.

Cardiopulmonary Bypass↗
PubMed1993

Late functional results after surgical closure of acquired ventricular septal defect.

To assess the longer term outlook for patients who have undergone surgery for acquired (postinfarction) ventricular septal defect, we interviewed and studied 60 survivors from a single regional cardiac center between 3 and 144 months after the operation. Including the patients who died within 1 month of the operation, the 5-, 10-, and 14-year survivals (with standard errors) were 69% (65% to 74%), 50% (44% to 57%), and 37% (27% to 46%). Eighty-two percent of patients were in New York Heart Association class I or II. Ten patients (17%) had a persisting but not hemodynamically significant ventricular septal defect. Mean left ventricular ejection fraction was reduced at 0.39 (standard deviation 0.15), but this did not correlate with either New York Heart Association class or exercise tolerance. Twenty-eight patients (47%) had asymptomatic arrhythmias (17 with ventricular premature beats). Angina and other medical problems were not prevalent.

Aged↗
PubMed1992

Induced hypothermia in the management of refractory low cardiac output states following cardiac surgery in infants and children.

Post-operative low cardiac output states remain a major cause of mortality following cardiac surgery in infants and children. Since 1979 we have used moderate induced whole-body hypothermia in the management of low-output states refractory to conventional modes of therapy. This is based not only upon the relationship between body temperature and oxygen consumption, but also on experimental work showing a beneficial effect of cooling upon myocardial contractility, particularly when there is pre-existing impairment of ventricular function. Between July 1986 and June 1990, 20 children with refractory low-output states were cooled by means of a thermostatically controlled water blanket to a rectal temperature of 32-33 degrees C. The median age was 12 months (1 week-11 years) with a median weight of 6 kg (3.5-33 kg). Ten children survived to leave hospital while a further two made a haemodynamic recovery. There was a marked reduction in heart rate (P < 0.001). The mean arterial pressure rose (P = 0.037) while there was a fall in mean atrial pressure (P < 0.001). There was a significant improvement in the urine output (P = 0.002). A fall in the platelet count (P < 0.001) was not accompanied by any change in the white cell count (P = 0.15). Although it is impossible to say whether cooling influenced the outcome in any of these children, it was usually effective in stabilising their clinical condition. The technique is simple and has a sound theoretical basis.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output, Low↗
PubMed1992

Twelve year experience with the modified Blalock-Taussig shunt in neonates.

Between 1978 and 1990, 53 consecutive modified Blalock-Taussig (MBT) shunts were performed on 51 neonates with cyanotic congenital heart disease using 3 mm-5 mm Gore-Tex grafts. Only 4 of these children had uncomplicated tetralogy of Fallot. The remainder had more complicated pathology requiring urgent intervention. Retrospective analysis of the acute and long term results was performed with 100% follow-up, ranging from 1 month to 12 years (mean 3 years). There were 3 (6%) early deaths (within 30 days of operation) and 17 (33%) late deaths. Of the late deaths, 2 died after further palliation, 2 died after total correction and 13 died suddenly at home. Post mortem examination of the 13 sudden deaths revealed blocked shunts in only 3. Actuarial survival at 2 years was 58%. Shunt patency at 12 months was 87% and at 2 years, 62%. No patient used their initial MBT shunt for more than 40 months. Although this shunt provides good initial palliation, there is a high incidence of late sudden death. We are also concerned about the limited life span of the shunt which partly (3/13) explains the sudden deaths. Therefore we have adopted an aggressive approach to re-study by angiography within 3 months of surgery.

Actuarial Analysis↗
PubMed1992

Complex coronary arterial anatomy in transposition of the great arteries. Arterial switch procedure without coronary relocation.

Translocation of the coronary arteries remains a technical problem in anatomic correction of transposition of the great arteries. Myocardial ischemia related to difficulties with coronary relocation is a significant factor in perioperative morbidity and mortality, particularly in those patients with complex coronary anatomy. Two neonates with transposition of the great arteries and intact ventricular septum are described in whom the coronary arteries arose from multiple ostia, all lying within sinus 1, with one of the ostia in each instance being severely eccentric. An anatomic switch of the great vessels was done without coronary relocation. This was achieved by means of an aortopulmonary fenestration with a bovine pericardial tunnel to allow coronary artery perfusion with blood from the neoaorta. An additional pericardial patch was placed to the contralateral wall of the proximal neopulmonary artery. Both infants had an uneventful postoperative recovery with no evidence of myocardial ischemia, although both have a mild gradient across the proximal pulmonary artery. This operative technique may be appropriate in those patients in whom there is concern over the feasibility of translocating the coronary arteries without producing myocardial ischemia.

Anastomosis, Surgical↗
PubMed1991

Cardiac arrhythmias after surgical correction of total anomalous pulmonary venous connection: late follow-up.

Sixteen patients (10 males and six females) aged 7 months to 20 years, who had undergone surgical repair in the first year of life for total anomalous pulmonary venous connection (TAPVC), underwent assessment of cardiac rhythm by 24-h electrocardiogram (ECG) monitoring, nine of them also had maximal exercise treadmill tests, 3 months to 19.5 years after surgical repair. No patient had symptoms of an arrhythmia and the resting ECG was normal in all except one who had occasional single supraventricular ectopic beats. But on 24-h ECG monitoring significant arrhythmias were recorded in six of the 16 patients, including supraventricular tachycardia (three patients), bradyarrhythmia (two patients), sick sinus syndrome (two patients), and multiform supraventricular and ventricular ectopic beats (two patients). Five of these six patients were assessed more than 6 years after surgery. An inappropriate chronotropic response was seen on maximal exercise treadmill testing in four patients; three of them had arrhythmias previously recorded by 24-h ECG monitoring. Our observations show that significant arrhythmias may occur in asymptomatic patients long after TAPVC correction, and we therefore recommend long-term follow-up of these patients, even if they are asymptomatic.

Adolescent↗
PubMed1991

The early and long-term results of surgery for coarctation of the aorta in the 1st year of life.

The cases of 110 infants less than 1 year of age, who had surgical repair for coarctation of the aorta between June 1974 and February 1988, were analysed. Three groups of patients were identified. In group 1 there were 39 patients with isolated coarctation. In group 2 there were 25 infants with additional ventricular septal defects (VSD), while in group 3 there were 46 infants with other associated congenital cardiac defects. Repair was performed using the subclavian flap aortoplasty (SFA) procedure in 83 patients, resection with end-to-end anastomosis (EEA) in 23, patch aortoplasty in 3 and Goretex tube bypass in 1. Twenty-eight patients had simultaneous pulmonary artery banding and one concomitant closure of the VSD. The overall early mortality rate was 8.2% (5.1% in group 1, 0% in group 2, and 15.2% in group 3). Age at operation (under 1 month, p = 0.04) and other associated cardiac anomalies (p = 0.03) increased early mortality significantly. There were 11 late deaths (10.8%) among 101 patients followed from 1 to 15 years (mean 5.3 years). Twelve patients underwent further surgery for recoarctation, eight of them within 11 months. A further 11 patients currently have a Doppler gradient across their coarctation site of more than 20 mmHg, but have not undergone further surgery to the coarctation repair site.

Anastomosis, Surgical↗
PubMed1990

Circulatory support in infants with post-cardiopulmonary bypass left ventricular dysfunction using a left ventricular assist device.

Extracorporeal membrane oxygenation has been advocated as the most appropriate mode of circulatory support in the paediatric age group for post-cardiopulmonary bypass ventricular dysfunction. The results in infants who have predominantly left ventricular failure, or who require such support in order to be weaned off bypass, have been disappointing. Three infants with severe left ventricular dysfunction following cardiopulmonary bypass for correction of congenital heart defects have been managed with a left ventricular assist device. Two required this form of circulatory support in order to be weaned from full bypass while in the third infant it was instituted for progressive left ventricular dysfunction postoperatively. All three were less than 10 kg in weight. Left atrial appendage to aortic bypass was effected using a closed loop circuit with a constrained vortex pump (Biomedicus). Duration of support ranged between 40 and 146 h. One infant made a complete recovery and was able to be discharged home 20 days postoperatively. Another made a circulatory recovery such that both mechanical and inotropic support could be discontinued but had sustained massive neurological damage. The third died of progressive left ventricular dysfunction. This experience with a left ventricular assist device demonstrates that it is technically feasible in small infants, and can be performed to good effect in infants with predominant left ventricular dysfunction following cardiac surgery. It may well be more appropriate than extracorporeal membrane oxygenation in this group of patients.

Cardiac Output, Low↗
PubMed1990

Reoperation for recurrent angina after aortocoronary bypass surgery.

One hundred reoperations were performed on 93 patients of a total of 2287 patients who underwent initial coronary artery bypass surgery (CABG) between September 1972 and August 1988. The mean age of the 84 males and 9 females was 55.5 years (range 31-75 years). All patients prior to reoperation had severe angina and were judged to be in NYHA class III or class IV. Late graft failure alone or in combination with progressive atherosclerosis accounted for more than 60% of the cases requiring reoperation. The early mortality for reoperation was 1% compared with 1.4% for initial CABG. Perioperative myocardial infarction was recorded as a complication in 3.2% of cases at initial operation compared with 1% at reoperation. Symptomatic improvement occurred in 89.1% of cases after reoperation and almost 60% became entirely asymptomatic (mean follow-up interval 17 months).

Adult↗
PubMed1990

Changing role of non-invasive investigation in the preoperative assessment of congenital heart disease: a nine year experience.

The total surgical experience of a supraregional paediatric cardiology unit over a nine year period (January 1980 to December 1988) was reviewed to assess the effect of the introduction of the full range of ultrasound techniques. A total of 1517 patients underwent cardiac surgery (955 cardiopulmonary bypass, 562 closed procedures). Of these, 485 patients (32%) did not undergo cardiac catheterisation before operation: 217 bypass (23% of all procedures under cardiopulmonary bypass) and 268 closed procedures (48%). The overall ratio of catheterisations to operations for patients undergoing palliative or corrective surgery fell from 0.97 (1980) to 0.38 (1988). The patients were classified as (a) neonates (0-28 days), (b) infants (one to 12 months), and (c) children (one to 14 years). The main impact of non-invasive surgical referral was in neonates (total catheter:operation ratio 0.38; neonates 0.2 for 1988). The surgical population was further divided according to the principal echocardiographic technique available: (a) 1980-4 cross sectional imaging; (b) 1985-6; imaging plus spectral Doppler ultrasound; (c) 1987-8; imaging plus spectral Doppler ultrasound and colour flow mapping. A fall in the catheter:operation ratio for all age groups was most pronounced in the last four years. This reflects increased familiarity and surgical confidence with non-invasive diagnostic assessment. The introduction of each new echocardiographic technique was associated with a significant fall in the total catheter:operation ratio compared with the preceding period. Six incorrect ultrasound diagnoses were made during the entire period; one of these patients died in the early postoperative period. The integration of Doppler ultrasound with cross sectional imaging has made non-invasive assessment an increasingly practical alternative to preoperative cardiac catheterization.

Adolescent↗
PubMed1990

Surgical treatment for infarct-related ventricular septal defects. Improved early results combined with analysis of late functional status.

A total of 101 patients (mean age 64.9 years) underwent surgical correction of postinfarction ventricular septal defect at this institution over a 15-year period (1973 to 1988). The overall early mortality rate was 20.8%, although the most recent experience with 36 patients (January 1987 to October 1988) has seen this decline to 11.1%. Factors found to influence early death significantly, when analyzed univariately, were as follows: (1) site of infarction (anterior 12.1%, inferior 32.6%, p = 0.02); (2) time interval between infarction and operation (less than 1 week 34.1%, greater than 1 week 10.5%, p = 0.008); (3) cardiogenic shock (present 38.1%, absent 8.5%, p = 0.001). Nonsignificant variables included preoperative renal function, age, and concomitant coronary artery bypass, although older age (greater than 65 years) became significant when examined in a multivariate fashion. Of the 80 hospital survivors, eight were subsequently found to have a recurrent or residual defect necessitating reoperation, with survival in seven. Late follow-up is 99% complete and reveals an actuarial survival rate for 100 patients of 71.1% at 5 years (95% confidence interval 60.6 to 80.0), and 40.0% at 10 years (95% confidence interval 21.7 to 58.4). A significant recent change in policy of not using coronary angiography in patients with a ventricular septal defect caused by anterior wall infarction has not resulted in any increase in either the early mortality or in the late prevalence of angina. The functional status of 38 surviving patients has been analyzed by a graded treadmill exercise protocol, whereas left ventricular functional assessment was by nuclear scan with additional information on mitral valve function by echocardiogram. Color Doppler flow mapping has been used to determine the presence of a residual defect. Most late survivors have limited exercise tolerance related to both cardiac and noncardiac factors. Left ventricular function is moderately impaired (mean ejection fraction = 0.39). However, many patients are elderly and have adapted to their residual symptoms without significant changes in life-style.

Age Factors↗
PubMed1988

Balloon dilatation of the pulmonary valve in the first year of life in patients with tetralogy of Fallot: a preliminary study.

Fifteen infants with tetralogy of Fallot, who would otherwise have required a palliative operation, underwent balloon dilatation of the right ventricular outflow tract. The mean period of palliation was 8.5 months (range 0-26 months). The procedure was performed without serious complications on 88% of occasions. This preliminary study suggests that balloon dilatation may be useful in the management of tetralogy of Fallot.

Catheterization↗
PubMed1988

The use of atenolol in the prevention of supraventricular arrhythmias following coronary artery surgery.

Sixty patients undergoing coronary artery bypass surgery were studied prospectively in order to investigate the effect of a cardioselective beta-blocker on the incidence of postoperative supraventricular arrhythmias. Patients with good left ventricular function were randomly divided into two groups: 30 patients treated with atenolol and 30 patients acting as controls. Atrial fibrillation was seen in 11 patients and frequent premature atrial extrasystoles were noted in one. Eleven (37%) patients in the control group experienced arrhythmias whilst atenolol significantly reduced this incidence to 3% (one patient), P = 0.001. There was no significant relationship between the development of supraventricular arrhythmias and the following variables: age, sex, severity of preoperative symptoms, previous myocardial infarction, extent of coronary artery disease, technique of myocardial preservation used, ischaemic time, number and site of saphenous vein grafts, endarterectomies performed and perioperative serum potassium levels. It is concluded that the use of atenolol (started 72 h before operation) is effective in reducing the incidence of supraventricular arrhythmias following elective coronary artery bypass operations in patients with good left ventricular function.

Angina Pectoris↗
PubMed1988

Total anomalous pulmonary venous drainage. Seventeen-year surgical experience.

Between 1968 and 1985, 80 children underwent correction of total anomalous pulmonary venous drainage. There were 47 boys and 33 girls whose ages ranged from 3 days to 16 years (median 2 months, interquartile range 5 years). Seventy (87.5%) were less than 1 year of age at operation. Fifty-eight (72.5%) weighed less than 5 kg, the range being 1.6 to 42 kg (median 3.7 kg, interquartile range 2.4 kg). Forty-five (56%) patients had supracardiac, 14 (17.5%) cardiac, 15 (19%) infracardiac, and 6 (7.5%) had mixed total anomalous pulmonary venous drainage. Follow-up was complete in 78 (97.5%) and ranged from 6 to 189 months (median 58 months, interquartile range 59 months). There were 14 (17.5%) early and six (7.5%) late deaths. Analysis by various factors revealed year of operation as the only factor to affect survival at the 5% level of significance. Early mortality was 29% between 1968-1977 and 11% between 1978-1985 (p = 0.04). Postoperative pulmonary venous obstruction occurred in five (6%) patients between 6 weeks and 3 months after operation. All 5 died, three after reoperation. Five (6%) other children had reoperations, four for residual shunts and one for superior vena caval obstruction.

Adolescent↗
PubMed1987

Pulmonary artery tear following balloon valvoplasty in Fallot's tetralogy.

A 3-year-old girl with Fallot's tetralogy underwent balloon pulmonary valvoplasty without any obvious complications. Elective total correction was performed 15 months later. At operation, a well-healed longitudinal tear measuring 2 cm was noted in the posterior wall of the main pulmonary artery 1 cm from the pulmonary valve extending into the right pulmonary artery.

Cardiac Catheterization↗