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Biomedical subjects

R M Whitlock

Publications and source records attributed to R M Whitlock.

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

Late outcome after coronary artery bypass graft surgery in patients < 40 years old.

BACKGROUND: Randomized trials confirm the long-term efficacy of coronary artery bypass graft surgery (CABG), although there are no randomized data in patients < 40 years old. Because these patients have been reported to have an early recurrence of symptoms, the long-term postoperative outcome was examined. METHODS AND RESULTS: The long-term outcome of patients (n = 221) < 40 years old undergoing CABG at Green Lane Hospital, New Zealand, from 1970 to 1992 was determined. The 30-day mortality rate was 1.8% for initial and 9.5% for redo CABG. The median times to angina or myocardial infarction (recurrent ischemic event), further intervention, and death were 6.0, 9.6, and 14.2 years, respectively. Factors associated with increased late mortality on univariate analysis included end-systolic volume (ESV) > or = 80 mL (P = .004; 10-year mortality 19% versus 39% ESV > or = 80 mL), no internal mammary conduit (P = .01), no lipid-modifying therapy (P = .005), and no postoperative aspirin use (P = .0002); the latter was also associated with increased recurrent ischemic events (P = .04) or increased reintervention (P = .02). On stepwise logistic regression analysis, factors associated with increased late mortality were increasing ESV (P = .004), no internal mammary artery conduit (P = .009), diabetes (P = .04), and no postoperative aspirin (P = .02); the latter was also associated with increased recurrent ischemic events (P = .02). Hypercholesterolemia (> or = 6.5 mmol/L) was present in 65% of patients at presentation and 45% at follow-up. CONCLUSIONS: To attempt to prevent recurrent ischemia or late death, patients < 40 years old who require CABG should receive internal mammary conduits, aspirin, lipid-modifying therapy, therapy to inhibit ventricular dilatation, and strict diabetes management.

Actuarial Analysis↗
PubMed1994

Waiting lists for coronary artery surgery: can they be better organised?

AIM: To determine whether a numerical ranking system can provide an equitable basis for prioritising patients awaiting coronary artery bypass grafting. METHODS: A review of the current coronary surgery waiting list was undertaken using a newly developed scoring system. The factors included in the score were age, symptoms, results of exercise testing, coronary anatomy, employment status and perceived surgical risk. This score was compared with a Canadian consensus system. Rankings were then compared with the clinical priorities given by clinicians when the patients were placed on the waiting list. RESULTS: There was excellent correlation between the two priority ranking systems using only those items included in the Canadian system (r = 0.9179). However, correlation between the Canadian system and the full Green Lane Hospital (GLH) scoring system was weaker (r = 0.6869). The Canadian system assigned higher surgical priorities than Auckland clinicians. Comparison between the GLH system and clinical priority gradings (O, urgent out of hospital), (A) and (B) showed considerable scatter. Waiting times for these three categories considered acceptable by the Canadian consensus group were two to six weeks for priority (O), six weeks to three months for priority (A) and three to six months for priority (B). The mean times on the waiting list for the 260 patients still awaiting surgery at GLH were two months for (O), 11 months for (A) and 22 months for (B). CONCLUSIONS: The Canadian and expanded GLH ranking systems are no more than aids to establishing priorities. They cannot replace clinical judgement because the importance of individual scoring items is heavily influenced by the ranking of other items. Waiting times for surgery are now grossly excessive despite the use of criteria for entry to the waiting list which are very conservative by international standards. There is no equitable or clinically acceptable way to modify priorities to reduce waiting times, and institution of a booking system is impractical.

Aged↗
PubMed1994

Tumor thickness in early tongue cancer.

OBJECTIVE: To review the relationship between tumor thickness and the subsequent development of cervical nodal metastases in 26 patients with stage I and II carcinomas of the oral tongue. METHODS: The histologic features of 26 consecutive patients treated for squamous carcinoma of the oral tongue were reviewed "blindly" by a pathologist, and the variables were correlated with clinical outcome. RESULTS: No association between tumor thickness and nodal metastases was found. Perineural infiltration was the only factor to approach statistical significance. There was also no statistically significant correlation between tumor thickness and patient survival. CONCLUSIONS: The histologic factors considered herein probably should be controlled for when comparing results of treatment of cancer of the oral tongue.

Carcinoma, Squamous Cell↗
PubMed1993

Coronary artery surgery in the elderly: long-term follow-up.

BACKGROUND: There has been controversy concerning the indications for coronary artery surgery in the elderly, particularly in countries where health resources are restricted. AIMS: To assess the results of coronary artery bypass grafting (CABG) in a large group of elderly subjects with regard to initial risks and long term follow-up. METHODS: Ninety-six consecutive patients aged 70 years or older underwent isolated CABG between January 1981 and December 1985. Long term follow-up was obtained in 94 (98%). RESULTS: The mean age was 71.6 years (70-78) and mean duration of follow-up 73 months. Seventy (73%) were male. In 80 cases the myocardial score was > 10. In 22 of 90 who had left ventricular angiography the ejection fraction was < 50%. Hospital survival was 96% and the five year survival 77%. It was not influenced by gender, myocardial score, ejection fraction or age at the time of operation. The status of survivors was reviewed in 1991. Of the 55 long term survivors 35 (64%) were free of angina. Eight (15%) and ten (18%) were in the Canadian Cardiovascular Society Angina classes 1 and 2 respectively. Seventeen patients (31%) had symptoms of heart failure with 14 (25%) in NYHA class 2 and 3 (5%) in class 3. Eight patients (15%) had survived a cerebrovascular event during follow-up. There were 35 late deaths (37%). Sixteen of these were cardiac, 18 due to other causes and one unknown.

Aged↗
PubMed1993

Aortic valve replacement in the elderly.

Aortic valve replacement is an established mode of therapy that enhances and prolongs life in patients with significant aortic valve disease. This is true for the elderly, but with a higher reported mortality and morbidity than in younger patients. One hundred and eighty-three elderly patients aged 70 years and over were considered suitable candidates for isolated aortic valve replacement (n = 97) or aortic valve replacement combined with coronary artery bypass surgery (n = 86) in the decade 1980-89. The mean age at surgery was 73.2 years (70-80). The hospital mortality and morbidity of this group were compared to 340 consecutive patients aged 60-69 who underwent similar surgery over the same period. There was no significant difference in hospital mortality: 4.4% for elderly patients and 4.1% for those aged 60-69. Measures of hospital morbidity were similar except for the perioperative stroke rate, which was 4.4% in the elderly patients and 1.5% in the younger group (p < 0.05). Detailed long term follow up was obtained in 75 of the 76 elderly patients who underwent aortic valve replacement or aortic valve replacement combined with coronary artery bypass surgery in the first five year period. Hospital survival was 99% (one hospital death). The overall five year actuarial survival was 81% and greater than the age and sexmatched general population (73%). Of the 44 patients alive at the time of review, 35 (80%) were free of angina and 32 (73%) had no significant symptoms of heart failure. Additionally, these patients were questioned about their quality of life.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

The zero pressure fixed medtronic intact porcine valve: an 8.5 year review.

The Medtronic Intact valve is the only porcine valve which is fixed in glutaraldehyde at zero pressure. This preserves near normal extensibility of the leaflet collagen, enabling full leaflet opening without kinking, which in turn should improve durability compared with low and high pressure fixed valves. From 1983 to 1991, 265 patients had 276 Intact valves inserted (125 aortic, 129 mitral, 22 tricuspid). The mean age was 53 years (10-81), with 24% below 40 years. The 100% follow up represents 911 patient years and averaged 50 months (3-106) in survivors. The actuarial survival was 54% +/- 9% at eight years, compared with a matched general population of 82%. The mean NYHA class was 3.2 preoperatively and 1.2 at follow up. At eight years, freedom from infective endocarditis was 97% +/- 1%, from thromboembolism 89% +/- 3%, and from non-structural dysfunction 96% +/- 2%. Reoperation was required in three patients for infective endocarditis, in six for non-structural dysfunction and in seven for structural valve deterioration (SVD). Freedom from SVD in the aortic position (mean age 59 years) was 100%, in the tricuspid position (mean age 48 years) 80% +/- 7%. In the mitral position, freedom from SVD was 86% +/- 10% in patients aged 60 years or more (n = 39, two events), 96% +/- 4% in those aged 40-59 years (n = 23, one event in a patient with renal failure), 67% +/- 16% in those aged 20-39 years (n = 31, three events in two following pregnancy) and 38% +/- 28% in those under 20 years (n = 9, two events).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

First-time coronary artery bypass grafting: the anaesthetist as a risk factor.

We have investigated the contribution of the anaesthetist and surgeon to outcome after 1301 consecutive coronary artery bypass grafting operations (first operation). The mean + 1 SD aspartate amino transferase concentration on the day after surgery (AST-D1) was 134 u litre-1 (or, after logarithmic transformation, 94 u litre-1). Twenty patients were selected at random from each of three groups having AST-D1 less than 100 u litre-1, 100-134 u litre-1 or greater than 134 u litre-1; positive ECG diagnoses of perioperative myocardial infarction were significantly more frequent with AST-D1 values greater than 100 u litre-1 than with smaller values, but no more frequent with AST-D1 greater than 134 u litre-1. Because several deaths occurred before AST-D1 could be measured, an "adverse outcome" was defined as either hospital death or AST-D1 greater than 100 u litre-1. Univariate analysis implicated both anaesthetist and surgeon as significant predictors of adverse outcome but, after allowing for 12 patient-related factors, only cardiopulmonary bypass time (or ischaemic cross-clamp time) (P less than 0.01) and anaesthetist (P = 0.05) were associated significantly with outcome.

Aged↗
PubMed1992

Prognosis after recovery from myocardial infarction: the relative importance of cardiac dilatation and coronary stenoses.

In order to further define clinical and angiocardiographic predictors of long-term survival after myocardial infarction we followed 616 consecutive male patients under 60 years of age, survivors of a first (N = 455) or recurrent (N = 161) myocardial infarction, for 8.8 +/- 2.9 years. Patients had angiocardiography at 4-8 weeks after infarction; none had thrombolysis, but 33% had cardiac surgery, 14% on a clinical trial basis. Left ventricular end-systolic volume was the most powerful predictor of cardiac mortality; ejection fraction and end-diastolic volume added no further information. Myocardial score, a measure of the severity of coronary stenoses in relation to the amount of myocardium supplied, was of only borderline predictive value on multivariate analysis, possibly because any effect had been negated by coronary surgery. Administration of beta-blocker drugs had an independent effect of improving prognosis, while continued cigarette smoking worsened it. Age, status of index infarction (first or recurrent) and serum cholesterol did not affect survival. A trial of surgery, carried out in a subset of 200 of these patients who were relatively asymptomatic but had severe coronary disease, showed no survival advantage for intended surgical over non-surgical management. We conclude that a high left ventricular end-systolic volume remains the most important adverse prognostic factor after recovery from myocardial infarction.

Actuarial Analysis↗
PubMed1992

The role of dipyridamole in addition to low dose aspirin in the prevention of occlusion of coronary artery bypass grafts.

One hundred and one subjects were randomised to receive either aspirin 100 mg or aspirin 100 mg + dipyridamole 300 mg daily before undergoing coronary bypass surgery. The drugs were commenced at least 36 hours before operation and patients were followed for one year. There were three perioperative deaths and 37 withdrawals, of which 14 were drug related (aspirin four, aspirin + dipyridamole ten). Cineangiocardiograms at nine weeks and one year showed vein graft patency rates of 93% and 87% for subjects treated with aspirin alone; and 90% and 89% in those who received aspirin+dipyridamole. During the follow-up period 14% of 232 coronary lesions in the aspirin treated group advanced by more than two grades compared with 15% of 315 lesions in the aspirin+dipyridamole group. The study did not establish superiority of one regimen over another in terms of graft patency or progress of lesions in native vessels. However, low dose aspirin was better tolerated than combination therapy.

Aged↗
PubMed1990

Intravenous amiodarone bolus versus oral quinidine for atrial flutter and fibrillation after cardiac operations.

The safety and efficacy of amiodarone and quinidine in reverting atrial tachyarrhythmias after cardiac operations were compared in a randomized cross-over trial. Patients with sustained atrial fibrillation or flutter for more than 2 hours' duration, stable hemodynamic status, and prior digoxin therapy were randomized to receive either intravenous amiodarone, 5 mg/kg over 20 minutes (41 patients), or oral quinidine, 400 mg immediately and 400 mg in 4 hours (39 patients), with cross-over at 8 hours if reversion was not achieved. Thirty-six patients had a coronary artery operation, 35 a valvular operation, five had both, and there were four miscellaneous cases. There was a male:female ratio of 1.5:1 and a mean age of 58 years (range 23 to 75 years). Preoperative atrial fibrillation or flutter was present in nine patients, and four patients had an ejection fraction less than 40%. Twenty-five of 39 patients (64%) given quinidine first reverted to sinus rhythm, compared with 17 of 41 patients (41%) given amiodarone first (2p = 0.04). Side-effects occurred in 18 patients given quinidine and five patients given amiodarone (2p = 0.01). Two patients, both given quinidine, were withdrawn from the study. There was no correlation, with either drug, between serum levels and clinical efficacy. Multivariate analysis identified longer times from arrhythmia to treatment, preoperative atrial fibrillation, mitral valve operations, and concomitant propranolol therapy as factors predictive of failure to revert to sinus rhythm. Oral quinidine was more effective than intravenous amiodarone in reverting postoperative atrial fibrillation and flutter but caused more side-effects.

Administration, Oral↗
PubMed1990

Rest and exercise hemodynamics of 20 to 23 mm allograft, Medtronic Intact (porcine), and St. Jude Medical valves in the aortic position.

Doppler echocardiography was used to measure gradients and valve areas at rest and after supine bicycle exercise in 35 patients with valve replacements 20 to 23 mm in size. Thirteen patients with a St. Jude Medical valve (St. Jude Medical, Inc., St. Paul, Minn.) were matched to 13 patients with an allograft valve, and seven patients with a Medtronic Intact (porcine) valve (Medtronic, Inc., Minneapolis, Minn.) to seven patients with an allograft valve. Patients were matched for age, sex, valve size, body surface area, and left ventricular systolic function. There was no statistically significant difference between the matched groups for body surface areas, resting cardiac output, exercise heart rate, or workload achieved. Mean pressure gradient was higher for St. Jude Medical than for allograft groups, both at rest (11.8 +/- 6.67 mm Hg for St. Jude Medical versus 6.67 +/- 2.98 mm Hg for allografts) and after exercise (16.4 +/- 8.47 mm Hg versus 9.7 +/- 3.94 mm Hg), but the differences were of borderline significance (p = 0.016 and 0.027, respectively). Valve area at rest was similar for both devices (1.4 +/- 0.45 cm2 for St. Jude Medical versus 1.8 +/- 0.56 cm2 for allograft; p greater than 0.1). There were highly significant differences between patients with Intact and those with allograft valves for resting mean pressure gradient (19.3 +/- 4.23 mm Hg for Intact versus 5.9 +/- 3.68 mm Hg for allograft; p less than 0.001) and for exercise mean pressure gradient (27.8 +/- 8.63 mm Hg versus 8.1 +/- 8.43 mm Hg; p less than 0.001). The differences between the valve areas at rest also were significant (1.1 +/- 0.12 cm2 versus 2.2 +/- 0.62 cm2; p less than 0.01). It is concluded that when a tissue valve is indicated in patients with a small aortic root, the freehand allograft aortic valve is an ideal device from the hemodynamic perspective and is superior to the Intact valve. It is also probably superior in this respect to the St. Jude Medical valve, although the analysis may be biased slightly in favor of the allograft valve.

Aged↗
PubMed1989

Effect of intravenous streptokinase as compared with that of tissue plasminogen activator on left ventricular function after first myocardial infarction.

In a double-blind trial comparing two thrombolytic agents as treatment for acute myocardial infarction, we randomized 270 consecutive patients an average (+/- SD) of 2.5 +/- 0.6 hours after the onset of chest pain from a first myocardial infarction--135 to receive intravenous streptokinase (1.5 million units over 30 minutes) and 135 to receive intravenous recombinant tissue plasminogen activator (rt-PA) (100 mg over three hours). The primary end point was left ventricular function as assessed by cineangiography performed three weeks after infarction. The effects of the two agents on left ventricular function were similar. The ejection fraction was identical (58 +/- 12 percent) in both groups. The end-systolic volume was 61 +/- 29 ml in the streptokinase group and 66 +/- 31 ml in the rt-PA group (P not significant). Patency rates at three weeks for the infarct-related artery were also similar (75 percent in the streptokinase group and 76 percent in the rt-PA group). Reinfarction rates at 30 days were the same (5 percent) in both groups. One patient had a fatal intracerebral hemorrhage 13 hours after receiving rt-PA, and another had a fatal cerebellar hemorrhage 21 hours after receiving rt-PA for reinfarction nine days after treatment with streptokinase. An intention-to-treat analysis revealed that mortality at 30 days was 3.7 percent in the rt-PA group as compared with 7.4 percent in the streptokinase group (P greater than 0.2). Follow-up for a mean of 9.0 months revealed no significant difference in survival; we observed 12 deaths (8.9 percent) in the streptokinase group and 8 deaths (5.9 percent) in the rt-PA group (P = 0.34). We conclude that rt-PA and streptokinase, in the doses given, have similar effects on left ventricular function after a first myocardial infarction. Because of the small number of deaths, it is not possible to determine whether their effects on mortality are similar.

Double-Blind Method↗
PubMed1988

A review of surgery for acquired tricuspid valve disease, including an assessment of the stented semilunar homograft valve, and the results of operation for multivalvular heart disease.

A total of 246 operations were performed in 230 patients for correction of acquired tricuspid valve disease. All but three of the patients had multivalvular heart disease. There was an 11% hospital mortality which fell to 7% in the later era (1973-82). Mortality was similar for tricuspid annuloplasty and tricuspid replacement and for double and triple valve surgery. On multivariate analysis the incremental risk factors for hospital death were extreme functional disability (Class V), being of Caucasian race, and having a high cardiothoracic ratio (CTR). Actuarial survival was 58% at 9 years postoperative. The incremental risk factors for late death were prior cardiac surgery, age at operation greater than or equal to 55 years, and advanced functional disability (Classes IV, V). The actuarial incidence of significant tricuspid incompetence following annuloplasty was 12% at 3 years, and following stented homograft semilunar valve replacement was 6% at 3 years and 24% at 8 years. Severe homograft valve incompetence was always associated with recurrent left-sided valve lesions or residual pulmonary hypertension. It is concluded that a homograft valve is a superior form of tricuspid valve replacement.

Adolescent↗
PubMed1988

Early and late results of re-operation for coronary artery disease: a 13-year experience.

A second coronary artery bypass grafting procedure was performed for recurrent angina in 119 patients between 1970 and mid-1983. Angiographic findings were assessed and computerized using the Brandt myocardial scoring system. The myocardial score was similar prior to the first and second operations. Graft failure was the most common indication for re-operation, either alone (48%) or in combination with progression of coronary artery disease (29%) or incomplete revascularization (10%). Progression of coronary artery disease alone was an indication in 9% and previous incomplete revascularization alone in 4%. The completeness of revascularization at the end of operation was analysed using a new index, the myocardial score/graft coverage rate. This showed that revascularization was less complete at the second operation than at the first (P less than 0.0001). The hospital mortality at re-operation was 2.5% and the peri-operative myocardial infarction rate was 9.2%. The follow-up period was 54 months (range 10-160 months). Actuarial survival was 94% at 5 years and 74% at 10 years. The average onset of recurrent angina was earlier after the second operation than after the first (P = 0.001). Using a cumulative actuarial curve, survival at 8 years was 85%, a further 6% of patients had undergone a third or fourth operation, and a further 25% were in NYHA Classes III or IV. Therefore 54% achieved a good or excellent result. It was concluded that re-operation is a worthwhile procedure.

Angina Pectoris↗
PubMed1988

Correction of inert gas washin or washout for gas solubility in blood.

We show that when an inert gas is washed into the lungs its retention in the blood during any one breath is approximately proportional to its solubility. This relationship makes possible the correction of washin or washout data for blood uptake or release, provided that two gases of different solubility are used simultaneously. The method automatically allows for the characteristics of an individual washin or washout and for the occurrence of recirculation within a fairly short washin or washout period. It has been tested in models with nonuniform ventilation and perfusion and closely approximates the behavior of a truly insoluble gas. In the derived ventilation distribution, gas solubility appears as ventilation to units of low turnover. In the case of N2 this effect is small but causes appreciable overestimation of lung volume. The recovered dead space and main alveolar distribution are insignificantly affected.

Cardiac Output↗
PubMed1987

Human alveolar gas-mixing efficiency for gases of differing diffusivity in health and airflow limitation.

1. Incomplete mixing of alveolar gas may be expressed as an equivalent alveolar dead space serving a remaining alveolar space in which mixing is regarded as complete. Calculation of this dead space during multiple-breath, inert gas wash-in or wash-out leads to an estimate of 'multiple-breath alveolar mixing efficiency' (MBME). 2. We measured MBME in 25 healthy subjects and six patients with chronic airflow limitation (CAL), and in three asthmatic patients before and after bronchial provocation with histamine aerosol, from successive breaths during open-circuit, multiple-breath wash-in of a mixture containing helium (He) and sulphur hexafluoride (SF6). The simultaneous use of a light and a heavy gas helps to identify diffusive mechanisms. 3. MBME fell almost linearly with log Z, the proportion of total wash-in remaining uncompleted. For a given Z, MBME was always lower for SF6 than for He in the same subject. In health the lowest MBME (52.2%) was seen for SF6 in a man aged 21 years. The same wash-in yielded a ventilation distribution with an extreme range of specific ventilation of less than 1 decade. MBME of this order is thus consistent with estimates of ventilation distribution in health. 4. Patients with CAL showed a big increase in the volume of the conducting airways or 'series dead space' (VDS) for both gases, and VDS was always bigger for SF6 than for He. This very large VDS appears to be the main reason for wash-in delay in these patients, followed by impaired diffusive mixing in the peripheral air spaces. Ventilation maldistribution may play little part in the mixing defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗