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Biomedical subjects

R Weisel

Publications and source records attributed to R Weisel.

8 recordsLinked to original sources
PubMed1992

Cultured vascular endothelial cell susceptibility to extracellularly generated oxidant injury.

To understand better the effect of oxidant injury on vascular endothelial cells, human saphenous vein endothelial cells were cultured at atmospheric (pO2 of 150 mmHg) or low (pO2 of 40 mmHg) oxygen tensions. The cellular rates of growth, antioxidant enzyme activities (superoxide dismutase, catalase, and glutathione peroxidase), phospholipid fatty acids and cellular susceptibility to extracellularly generated oxidants (hypoxanthine-xanthine oxidase) were measured. The antioxidant enzyme activities were regulated by oxygen tension and significantly differed by day 14. The cells cultured at the low oxygen tension had significantly (P less than 0.01) lower antioxidant activities than the cells cultured at the high oxygen tension. The cells cultured at an oxygen tension of 150 mmHg were more resistant to shrinkage and lipid peroxidation from the oxidants than the cells cultured at a pO2 of 40 mmHg by day 14. Since arterial and venous endothelial cells are perfused with blood at a pO2 of 100 and 40 mmHg, respectively, the postcapillary venous endothelial cells should have lower antioxidant enzyme activities than the precapillary arterial endothelial cells.

Catalase↗
PubMed1990

Validation of left ventricular function parameters acquired with the non-imaging nuclear probe: comparison with tantalum marker cine-fluoroscopy.

We evaluated the accuracy of the non-imaging nuclear probe for measuring various parameters of left ventricular function by comparing these with simultaneous measurements acquired via tantalum marker cine-fluoroscopy. Eight patients with surgically implanted mid-myocardial tantalum markers were studied during cardiac catheterization. High temporal resolution tantalum marker-derived volume/time curves were generated and calibrated to absolute endocardial volumes by comparison with contrast left ventricular angiography. Left ventricular function parameters were acquired at baseline and during atrial pacing, nitroprusside infusion and volume loading. Simultaneous measurements obtained with the nuclear probe and via tantalum marker cine-fluoroscopy were compared. The following correlation coefficients were obtained: ejection fraction, r = 0.49, P less than 0.001; peak ejection rate, r = 0.41, P less than 0.01; mean ejection rate, r = 0.62, P less than 0.001; time to peak ejection, r = 0.73, P less than 0.001; peak filling rate, r = 0.73, P less than 0.001; time to peak filling, r = 0.58, P less than 0.001. Relative changes in end-diastolic volume were accurately tracked by the nuclear probe in six of seven patients (r values 0.77-0.93). These results suggest that measurements of certain left ventricular volume parameters with the nuclear probe may not accurately reflect true volume changes as measured by tantalum marker cine-fluoroscopy. Although, the probe may be useful in tracking relative changes in end-diastolic volume, we would advise caution in using this instrument for studies requiring accurate measurements of ejection and filling parameters.

Cardiac Catheterization↗
PubMed1990

Doppler echocardiography assessment of prosthetic heart valves.

Transthoracic Doppler echocardiography is an accurate noninvasive method for the evaluation of prosthetic valve function. The flow characteristics and pressure gradients of normally functioning mechanical and bioprosthetic valves have been, in general established. Normal functioning mitral valve prostheses have a valve area greater than 1.8 cm 2 with the St. Jude valve having the largest effective valve area and normally functioning aortic prosthetic valves have a peak instantaneous gradient of less than 45 mmHg, with the Starr-Edwards valves (Starr-Edwards, Irvine CA) showing the highest gradients. The incidence of minimal or mild regurgitation is approximately 15% to 30% in the mitral position and 25% to 50% in the aortic position, with the higher incidence of regurgitation seen with mechanical compared to bioprosthetic valves. Transthoracic Doppler echocardiography can accurately detect patients with prosthetic valvular stenosis. The presence of prosthetic aortic regurgitation can also generally be accurately assessed, except in the presence of both prosthetic aortic and mitral valves. Assessment of prosthetic mitral regurgitation remains limited due to significant attenuation of the ultrasound beam by the prosthesis and the frequent underestimation of severity of regurgitation. Other limitations of transthoracic studies include assessment of leaflet morphology, detection of vegetations and valve abscesses, and differentiation between valvular and paravalvular regurgitation.

Bioprosthesis↗
PubMed1985

Determinants of risk for coronary artery bypass grafting in stable and unstable angina pectoris.

Although the operative risk and morbidity associated with coronary artery bypass grafting for chronic stable angina is exceptionally low, clinical and angiographic factors exist that may predict differing outcomes in patient subsets. Forty-five variables were prospectively recorded on all 1302 patients who underwent coronary artery bypass grafting at Toronto General Hospital over a 24-month period. Twelve selected variables were analysed by univariate and multivariate techniques. The patients were divided in two groups depending upon their clinical presentation (stable versus unstable angina) and the timing of surgery (elective versus urgent). The results of risk-factor analysis revealed that the unstable cohort had four predictors for operative mortality: sex, age, left ventricular function and left main coronary stenosis greater than 50%, whereas the stable cohort had only three predictors: sex, age and left ventricular function. The results for postoperative morbidity (perioperative myocardial infarction or low-output syndrome) showed that the unstable cohort had six predictors: sex, age, left ventricular function, timing of surgery, extent of coronary artery disease and the type of myocardial protection used. The stable cohort had only three predictors of morbidity, the same as for mortality. This analysis of multiple risk factors on patients grouped according to stability and timing of surgery clearly demonstrated determinants of risk in the two groups (operative mortality for the stable group of 2.9% versus 5.4% for the unstable group, and perioperative infarction rate for the stable group of 9.1% and for the unstable group of 13.7%).

Angina Pectoris↗
PubMed1978

Diagnostic value of the portable chest x-ray technic in pulmonary edema.

The ability of the portable chest x-ray film to define the amount of physiologic shunting and the severity of noncardiogenic pulmonary edema was evaluated in thirty-seven observations of eleven patients. Ten of the eleven patients were suffering from acute respiratory failure. The radiologic assessment of the amount of pulmonary edema and the severity of left ventricular failure were compared with the physiologic shunt fraction, tracer-measured lung water, and pulmonary arterial wedge pressure. The radiologic scores for edema did not predict the shunt fraction or tracer measurements of lung water. The radiologic score for congestive failure correlated with the wedge pressure but not well enough to be clinically useful. Five per cent of the x-ray results were false-positive and 11 per cent false-negative. Results indicate that the portable chest x-ray technic does not provide quantitative information regarding cardiopulmonary function. It is especially hazardous to accept an x-ray diagnosis of congestive failure as the cause of pulmonary edema.

Adult↗
PubMed1978

Limitations of portable roentgenography of the chest in patients with acute respiratory failure.

The ability of the portable roentgenography of the chest to define the amount of physiologic shunting and the severity of noncardiogenic pulmonary edema was evaluated in 37 observations of 11 patients. Ten of the 11 patients had acute respiratory failure. The roentgenologic assessment of the amount of pulmonary edema and the severity of left ventricular failure was compared with the physiologic shunt fraction, tracer measured lung water and the pulmonary arterial wedge pressure. The roentgenologic scores for edema did not predict the shunt fraction or tracer measured lung water. The roentgenologic score for congestive heart failure correlated with the wedge pressure but not well enough to be clinically useful. Five per cent of the roentgenograms were false-positive and 11 per cent were false-negative. Roentgenologic findings lagged behind physiologic derangements. Thus, the roentgenogram could predict the shunt value of the preceding day. Results indicate that it is hazardous to accept a portable roentgenographic diagnosis of congestive heart failure as a cause of pulmonary edema.

Acute Disease↗
PubMedDate not supplied

The effect of moderate exercise training on oxygen uptake post-aortic/mitral valve surgery.

BACKGROUND: This study determined the response of aortic and/or mitral valve replacement/reconstruction (AVR/MVR) surgery patients to a 3-month exercise rehabilitation program (ERP) of moderate intensity, frequency, and duration that commenced approximately 9 weeks post-operatively. METHODS: Based on geographic proximity and availability of transportation to attend ERP classes, 29 experimental subjects were enrolled in the ERP and 20 control subjects received standard care that did not include the ERP, but did not prohibit activity/exercise. Exercise tolerance was determined from estimated oxygen uptake (VO2) during exercise tolerance testing (GXT) before and after standard care or the ERP. RESULTS: VO2 at the maximum stage of the GXT increased significantly (P < or = 05) for the experimental (4.89 +/- 5.07 mL/kg/min) and control (5.11 +/- 4.48 mL/kg/min) groups. No significant between-group differences were noted in VO2 at the maximum stage of the exercise testing or at the target heart rate (HR). Furthermore, reported exercise levels of subjects in both groups were comparable and sufficient for training effects to occur. CONCLUSION: Alternate strategies to improve exercise tolerance such as home-based rehabilitation programs should be investigated for relatively healthy aortic and/or mitral valve surgical patients.

Aortic Valve Insufficiency↗