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Biomedical subjects

P R McLaughlin

Publications and source records attributed to P R McLaughlin.

At least 19 recordsLinked to original sources
PubMed1998

Diabetes Atherosclerosis Intervention Study (DAIS): quantitative coronary angiographic analysis of coronary artery atherosclerosis.

The primary objective of the Diabetes Atherosclerosis Intervention Study (DAIS) is to determine by quantitative coronary angiography whether long-term correction of the dyslipoproteinemia of diabetes with micronized fenofibrate results in evidence of decreased progression or regression of angiographically measured obstructive coronary atherosclerosis. The purpose of this communication is to describe the angiographic methodology for the DAIS project, and to present data documenting the reproducibility of measurements that will determine the primary outcome of DAIS. Four hundred eighteen subjects between the ages of 40 and 65 were entered from 11 centers in Canada, France, Finland, and Sweden, with 305 males and 113 females. Thirty-two percent of subjects had undergone a previous coronary artery intervention, either PTCA or bypass grafting. Subjects underwent coronary arteriography at baseline according to a strictly defined protocol. The coronary tree was divided into AHA segments and quantitative analysis of segments was performed using the cardiovascular measurement system described by Reiber. Geometric parameters including mean lumen diameter, minimum lumen diameter, maximum lumen diameter, and segment length were determined. In 15 studies, measurements were carried out on the same frame by two observers, and at least 1 week apart by the same observer. In 13 studies, measurements were performed by the same observer on two separate injections of the same coronary artery. The mean of the standard deviation of the differences of measurements of all segments for the primary study analyst was 0.029 mm, with a mean of correlation coefficients of 1.00. Between two observers, the mean of the standard deviations of segmental mean lumen diameters was 0.347 mm with a mean of coefficients of variation of 0.78. The mean of standard deviations for measurements of segmental mean lumen diameter from two separate coronary injections was 0.122, with a mean of correlation coefficients of 0.94. The mean of correlation coefficients for minimum lumen diameter were 0.98 for intraobserver variability, 0.77 for inter-observer variability, and 0.96 for inter-angiogram variability. For segment length the corresponding values were 0.99, 0.79, and 0.94. These data demonstrate that a high level of reproducibility and precision may be achieved in a multicenter study in assessment of the coronary tree in carefully performed studies using this methodology. We anticipate the results will provide a statistically powerful conclusion with new and unique data to answer the question of the effect of long-term correction of dyslipoproteinemia on coronary atherosclerosis in type II diabetic patients with dyslipoproteinemia.

Adult↗
PubMed1997

Sustained ventricular tachycardia in adult patients late after repair of tetralogy of Fallot.

OBJECTIVES: We sought to determine the features associated with sustained monoform ventricular tachycardia (VT) in adult patients late after repair of tetralogy of Fallot (TOF) and to review their management. BACKGROUND: Patients with repair of TOF are at risk for sudden death. Risk factors for ventricular arrhythmia have been identified from patients with ventricular ectopic beats because of the low prevalence of sustained VT. METHODS: From a retrospective chart review of patients assessed between January 1990 and December 1994, 18 adult patients with VT were identified and compared with 192 with repaired TOF free of sustained arrhythmia. RESULTS: There was no significant difference in age at repair, age at follow-up or operative history. Patients with VT had frequent ventricular ectopic beats (6 of 9 vs. 21 of 101), low cardiac index ([mean +/- SD] 2.4 +/- 0.4 vs. 3.0 +/- 0.8) and more structural abnormalities of the right ventricle (outflow tract aneurysms and pulmonary or tricuspid regurgitation) than control patients. Electrophysiologic map-guided operation was performed in 10 of 14 patients who required reoperation. VT has reoccurred in three of these patients. Four patients did not undergo operation (three received amiodarone; one underwent defibrillator implantation). Two patients with VT also had severe heart failure and died. CONCLUSIONS: Most patients with VT late after repair of TOF have outflow tract aneurysms or pulmonary regurgitation, or both. These patients have a greater frequency of ventricular ectopic beats than arrhythmia-free patients after repair of TOF. A combined approach of correcting significant structural abnormalities (pulmonary valve replacement or right ventricular aneurysmectomy, or both) with intraoperative electrophysiologic-guided ablation may reduce the potential risk of deterioration in ventricular function and enable arrhythmia management to be optimized.

Adult↗
PubMed1997

Pulmonary valve replacement late after repair of tetralogy of Fallot.

BACKGROUND: Pulmonary valve incompetence is usually well tolerated after tetralogy of Fallot repair but may result in late progressive right heart failure as manifested by increasing fatigue, dyspnea, and frequently arrhythmias. METHODS: All patients who underwent pulmonary valve replacement in our center late after repair of tetralogy of Fallot were reviewed. RESULTS: Eighty-five patients had elective pulmonary valve replacement late (median, 9.3 years) after repair. Operative risk was low (1.1%). Ninety percent of survivors are in New York Heart Association class I. Survival 10 years after pulmonary valve replacement is 95%, with 86% of the patients free of reoperation for valve failure. CONCLUSIONS: Pulmonary valve replacement is infrequently required after repair of tetralogy of Fallot. Pulmonary valve replacement may be performed electively with little risk; it improves symptoms of right heart failure and provides satisfactory long-term survival with low risk of early valve failure. As the population of patients who have had repair of tetralogy of Fallot ages, pulmonary valve replacement will become a more frequent consideration.

Adolescent↗
PubMed1996

Percutaneous catheter closure of the persistently patent ductus arteriosus in the adult.

The USCI patent ductus occluder has been shown to be an effective nonsurgical technique for closure of the persistently patent ductus in a primarily pediatric population. Its clinical impact in the adult has been reported only within small subgroups of larger pediatric studies or for a small population. This study was conducted to determine the feasibility, success rate, and complications of device closure for the persistently patent ductus arteriosus (PDA) in the adult. The population consisted of 55 patients (4 men and 51 women; mean age 38.8 +/- 15.0 years) with follow-up of 2.2 +/- 2.1 years. All patients underwent echocardiography obtained as part of their follow-up assessment. The device was successfully placed in 54 patients, with 75% clinical and echocardiographic closure at the first follow-up assessment 2.4 +/- 2.6 months). One patient with initial clinical and echocardiographic evidence of closure was subsequently found to have an open ductus. Spontaneous closure (2 patients) or second implant (6 patients) resulted in 86% closure at the most recent assessment. Thus, the percutaneous PDA double-umbrella occluder device is a feasible and effective technique for closing persistent PDA in the adult and will result in occlusion of the shunt in most patients without the need for thoracotomy.

Adolescent↗
PubMed1996

Congenitally corrected transposition of the great arteries in the adult: functional status and complications.

OBJECTIVES: We sought to assess the clinical outcome, functional status and complications of adult patients with congenitally corrected transposition of the great arteries. BACKGROUND: Congenitally corrected transposition is a rare form of congenital heart disease, although survival into adult life may be expected. Little information is available on the long-term prognosis of these patients once they have reached adulthood. This study focuses exclusively on patients >18 years old followed up at a single tertiary referral center. METHODS: The charts of all patients with a diagnosis of congenitally corrected transposition of the great arteries from the Toronto Congenital Cardiac Centre for Adults since 1985 were reviewed. Data were available for 52 patients, 26 of whom had undergone radionuclide angiography. Mortality, clinical and functional status, surgical procedures and complications were reviewed. RESULTS: Thirteen patients (25%) died; age at death was 38.5 +/- 12.5 years (mean +/- SD). The current age of survivors is 32.7 years (range 18.2 to 54.3). Of the survivors, 17 had palliative procedures, and 25 had definitive repair, 11 of whom required reoperation. Left ventricle to pulmonary artery conduit replacement was necessary in seven patients. Eighteen patients have permanent pacemakers, nine of whom developed complete heart block perioperatively. Nine patients developed progressive atrioventricular (AV) block unrelated to operation. Supraventricular arrhythmias occurred in 15 patients. Progressive systemic AV valve regurgitation developed in 10 patients and endocarditis in 6. CONCLUSIONS: Congenitally corrected transposition in the adult patient is not a benign condition. Late complications are common and warrant careful, long-term follow-up.

Adult↗
PubMed1996

Interventional cardiology for the adult patient with congenital heart disease: the Toronto Hospital experience.

Interventional cardiac procedures for patients with congenital heart disease, developed for the pediatric patient, have been adapted for the adult patient. In this review these unique procedures are reviewed with emphasis on the experience at The Toronto Congenital Cardiac Centre for Adults. Procedures directed to closing shunts include: occlusion of patent ductus arteriosus, coil embolization of aorto-systemic collaterals, coronary fistulas, and Blalock-Taussig shunts, and early attempts at nonsurgical occlusion of atrial septal defects. Balloon dilation procedures include management of pulmonary valve stenosis, peripheral pulmonary artery stenosis, and more recently the application of stents in dilation of coarctation of the aorta. Development of interventional techniques for adult congenital heart disease involves a diverse number of procedures which provide successful nonsurgical options for many patients with congenital heart disease.

Adult↗
PubMed1996

Sudden cardiac death in the adult with congenital heart disease.

Preliminary results of a review of sudden cardiac death in the adult with congenital heart disease were presented at the Canadian Adult Congenital Heart (CACH) Network meeting during the Canadian Cardiovascular Society's annual meeting in October 1994. Of 125 patients who were known to have died, sufficient details were available for 92 to determine the circumstance of death. Sudden death occurred in 23 patients (estimated incidence 5.3 per 1000 patients followed per year) at an average age of 33.5 +/- 11.9 years. Surgical procedures included intracardiac repair in 12, palliative procedures in only six and no cardiac surgery in six. Nine patients with sudden death had Eisenmenger syndrome. Right or left ventricular abnormalities were present in 15 of 21 patients with premorbid echocardiographic evaluation. A prior history of ventricular arrhythmia was available in only three patients. Sudden death is a significant cause of mortality in adults with congenital heart disease. Determination of risk factors will be an important aspect of the patient database under development by the CACH Network.

Adult↗
PubMed1995

Cardiopulmonary function in adult patients late after Fontan repair.

OBJECTIVES: The clinical status and exercise assessment of adult patients late after the Fontan operation were reviewed to determine cardiovascular function. BACKGROUND: The Fontan operation is the final operation for many patients with tricuspid atresia or a single ventricle. Follow-up reports describe most patients to be in Canadian Cardiovascular Society functional class I or II. Objective measures of cardiac performance in the pediatric age group have shown significant dysfunction. METHODS: Forty-seven adult patients were seen late after the Fontan operation at the Toronto Congenital Cardiac Centre for Adults. Thirty of these underwent cycle ergometry to determine maximal exercise capacity. Maximal ventilation, maximal oxygen uptake and anaerobic threshold were determined from a ramp exercise protocol. Ejection fraction at rest and during exercise was measured with gated radionuclide angiography. Results were compared with those of eight normal volunteers. Results are given as mean +/- SD. RESULTS: Thirty patients underwent cardiopulmonary exercise testing 6.7 +/- 3.9 years after a first Fontan operation. Clinically 93% were in functional class I or II. The Fontan group patients had a significantly lower maximal work load (548 +/- 171 vs. 1,094 +/- 190 kilopond-meters, p < 0.00001), anaerobic threshold (11.2 +/- 2.9 vs. 23.6 +/- 4.6 ml/kg per min) and maximal oxygen consumption (14.8 +/- 4.5 vs. 42.1 +/- 10.0 ml/kg per min). Systemic ventricular ejection fraction was lower at rest (38 +/- 12% vs. 58 +/- 7%) and during exercise (40 +/- 15% vs. 70 +/- 8%). CONCLUSIONS: Despite a clinical impression of good function, by objective measures adult patients continue to have significant cardiovascular limitation late after the Fontan operation.

Adult↗
PubMed1995

Favorable left ventricular remodeling following large myocardial infarction by exercise training. Effect on ventricular morphology and gene expression.

Continued adverse remodeling of myocardium after infarction may lead to progressive ventricular dilation and heart failure. We tested the hypothesis that exercise training in a healed myocardial infarction-dysfunction rat model can favorably modify the adverse effects of ventricular remodeling including attenuation of abnormal myosin gene expression. Sprague-Dawley rats were subjected to either proximal LAD ligation or sham operation. At 5 wk after the operation, animals were randomly assigned to sedentary conditions or 6 wk of graduated swim training, creating four experimental groups: infarct sedentary (IS), infarct exercise (IE), sham sedentary (SS), and sham exercise (SE). At 11 wk all rats were sacrificed and analyzed. Compared to sedentary infarct controls, exercise training attenuated left ventricular (LV) dilation and allowed more hypertrophy of the non infarct wall. The exercise-trained hearts also showed a reduction in the estimated peak wall tension. Northern blot analysis showed an increase in beta-myosin heavy chain expression in the hearts of the sedentary infarction group soon after infarction when compared to sham controls. However, with exercise training, there was a significant attenuation of the beta-myosin heavy chain expression in the myocardium. Exercise training in a model of left ventricular dysfunction after healed myocardial infarction can improve the adverse remodeling process by attenuating ventricular dilation and reducing wall tension. The abnormal beta-myosin expression was also attenuated in the exercise trained group. This is evidence that abnormal gene expression following severe myocardial infarction dysfunction can be favorably modified by an intervention.

Animals↗
PubMed1994

Right-to-left shunt following repair of partial anomalous pulmonary venous connection: a novel use of the Rashkind double-umbrella occlusion device.

A patient with partial anomalous pulmonary venous connection complicated by postoperative occlusion of the distal superior vena cava and a baffle leak causing right-to-left shunt is described. Surgery was avoided by balloon dilation and stenting of the superior vena cava. The baffle leak was closed with a Rashkind double-umbrella device.

Adult↗
PubMed1994

Alterations in fatty acid metabolism in adriamycin cardiomyopathy.

Myocardial fatty acid metabolism may be impaired in adriamycin cardiomyopathy. In order to determine the extent of fatty acid metabolism alterations, we measured steady state [14C]palmitate oxidation and the incorporation of [14C]palmitate into the neutral lipid pool in a rat model of adriamycin cardiomyopathy. Isolated hearts from control rats and rats treated with adriamycin were perfused with 1.2 mmol/l of [14C]palmitate for 30 min to achieve steady state oxidation measured as [14C]O2 production; then perfused with 1.2 nmol/l of unlabelled palmitate. Hearts were killed early (0-5 min) or late (10-30 min) after the [14C]palmitate perfusion, to determine incorporation into the neutral lipid pool, and neutral lipid utilization. In the control group steady state oxidation was reached in 10 min ([14C]O2 production = 580 +/- 61 nmol/min/g dry wt) of perfusion. In the adriamycin treated group, mean CO2 production was significantly reduced at 10 min (329 +/- 44 nmol/min/g dry wt, P < 0.01 v control). At 30 min, [14C]O2 production in the treated group was not significantly different than controls (521 +/- 65 nmol/min/g dry wt v 617 +/- 36 nmol/min/g dry wt, P = N.S.). The incorporation of [14C]palmitate into the neutral lipid pool measured in the early subgroup was significantly reduced for adriamycin treated hearts v controls (7.2 +/- 0.6 v 12.0 +/- 1.4 mumol/g dry wt respectively, P < 0.01). In the control group 14C labelled neutral lipid reduced with time to 8.4 +/- 1.1 mumol/g dry wt (P < 0.05) in the late group. The adriamycin group demonstrated no significant change between early and late measurements. In conclusion, in adriamycin cardiomyopathy: (1) there is significant delay in achieving steady state palmitate oxidation, although the steady state rate is near normal; (2) palmitate incorporation into the neutral lipid pool is reduced; (3) neutral lipid pool utilization may also be reduced. These data suggest impaired uptake of palmitate into the cell in adriamycin cardiomyopathy, with a relatively maintained capacity for oxidative metabolism.

Animals↗
PubMed1993

Atrial natriuretic peptide during acute and prolonged exercise in well-trained men.

In this study, cardiac performance and circulating immunoreactive atrial natriuretic peptide (Ir-ANP) were measured during sustained exercise to examine the relationship between cardiac filling, heart rate and circulating ANP. Fifteen well-trained male subjects (mean age = 27.6 +/- 1 years) were studied during two exercise sessions. Initially, graded exercise to maximum was performed to determine maximal oxygen consumption (VO2max). On a separate occasion subjects performed 150 minutes of continuous exercise at 70-74% of the maximal heart rate, with radionuclide angiography performed at rest and every 50 minutes, in conjunction with Ir-ANP, blood pressure and heart rate measurements. During maximal exercise subjects reached a VO2max of 47.9 +/- 2.1 ml/kg/min. Ir-ANP increased from 9.8 +/- 1.1 pg/ml at rest to 45.2 +/- 6.6 pg/ml at maximal exercise. Ir-ANP remained elevated (28.9 +/- 3.4 pg/ml) 3 minutes after exercise (p < 0.05). During prolonged exercise, left ventricular end-diastolic filling decreased significantly between 50 and 150 minutes (p < 0.05), with progressive rise in heart rate observed between 50 (141 +/- 8 beats/minute) and 150 minutes (154 +/- 3 beats/min; p < 0.05). No change in left ventricular end-systolic counts, or arterial blood pressure were observed throughout the exercise period. Ir-ANP was elevated significantly during prolonged exercise, increasing from 9.4 +/- 1.7 at rest, to 19.2 +/- 3.4 after 50 minutes, 17.8 +/- 4.3 pg/ml after 100 minutes of exercise (p < 0.05), and 23.5 +/- 2.1 pg/ml by 150 minutes of exercise. A weak correlation (r = 0.33) was observed between heart rate and Ir-ANP throughout the exercise session.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Vascular conductance and aerobic power in sedentary and active subjects and heart failure patients.

The relationship between peak aerobic power and a strain-gauge determination of local skeletal muscle vascular conductance 10-13 s after calf exercise to fatigue was examined in 21 middle-aged adults (age 38.1 +/- 2.5 yr): seven physically active men (A), seven sedentary men (S), and six men and one woman with compensated idiopathic heart failure (HF). The three subgroups were chosen as differing widely in peak O2 intake [48.2 +/- 1.2, 32.9 +/- 1.6, and 16.1 +/- 1.3 (SE) ml.kg-1 x min-1, respectively]. Calf vascular conductance showed a gradation with aerobic power: 64.8 +/- 3.8, 40.7 +/- 4.3, and 30.7 +/- 6.1 (SE) ml/min local flow per 10 liters of tissue per unit of blood pressure. There was a strong positive correlation between O2 intake and vascular conductance for the overall group (VO2 = 0.614 G + 3.5; r = 0.75, P < 0.001) and for the 14 normal subjects (VO2 = 0.377 G + 20.6; r = 0.74, P < 0.002). The mean conductance was smaller in HF (P < 0.001), with no significant slope in relation to O2 intake. There was no relationship between the resting cardiac ejection fraction [74.4 +/- 4.1% (SE) for A, 74.3 +/- 4.2% for S, and 25.8 +/- 5.2% for HF] and either peak aerobic power or calf vascular conductance. We conclude that peak aerobic power is strongly associated with local vascular conductance during peripherally limited exercise involving the calf muscles of one leg and that vascular conductance is particularly low in subjects with compensated idiopathic heart failure.

Adult↗