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Biomedical subjects

V J Fisher

Publications and source records attributed to V J Fisher.

At least 19 recordsLinked to original sources
PubMed1997

Racial differences in performance of invasive cardiac procedures in a Department of Veterans Affairs Medical Center.

Racial differences have recently been described in hospital practice, most notably with regard to cardiac procedure utilization. To evaluate the possible reasons behind these differences, we analyzed statistics generated from a surgical referral conference at a large, tertiary care Veterans Affairs hospital between the years 1988 and 1996. In this setting, there is no financial incentive for physicians to recommend or perform invasive procedures, as all physicians are salaried employees of the Veterans Administration. Furthermore, all patients presented at conference have already had cardiac catheterization and are felt to be potential candidates for surgery or angioplasty. Cardiac therapeutic procedures (surgery or percutaneous transluminal coronary angioplasty) were recommended for 1075 of 1474 (72.9%) Caucasian patients and 207 of 322 (64.3%) African-American patients (odds ratio 1.497, 95% confidence interval 1.160 to 1.932, p = 0.0022). Of those patients presented with the option of an invasive procedure, 32 of 207 (15.4%) African-American patients and 89 of 1075 (8.3%) Caucasian patients refused any invasive procedure (odds ratio 2.026, 95% confidence interval 1.311 to 3.130, p = 0.0025). We conclude that reluctance by African-American patients to undergo invasive cardiac procedures may help explain observed disparities in race-related cardiac care.

Black or African American↗
PubMed1990

Combined force and voltage measurement in rapidly superfused guinea pig heart cells.

We describe the construction and use of a setup that allows the rapid exchange of the solution surrounding an isolated guinea pig heart cell while simultaneously measuring the isometric force and membrane potential (Em). Cells were stably attached, by means of poly-L-lysine, to a force transducer which was adapted from one previously used for a study of frog atrial cells [N. Shepherd and F. Kavaler.Am. J. Physiol. 251 (Cell Physiol. 20): C653-C661, 1986]. The modified transducer is simple to construct and use and can be readily added to existing patch-clamp setups. The strength of attachment of a cell to the transducer exceeded the strength of the gigaseal in all of the experiments. The membrane potential was measured by means of patch electrodes and a high-impedance voltage follower. Rapidly changing extracellular K concentration [( K]o) from 5.4 to 10.8 mM caused a positive change of Em by 16.5 +/- 1.4 mV with a half-time (t1/2) of 27 +/- 4 ms. Replacing calcium in the perfusate by magnesium instantly abolished the contraction and shortened the action potential. Twitch tension returned stepwise to the control value on return of calcium to the perfusate. Our initial observations show that the patch electrode can be used successfully in conjunction with the isometric force transducer and rapid extracellular solution changes for studies of excitation and contraction coupling in isolated mammalian heart cells.

Action Potentials↗
PubMed1987

Predictive value of clinical and exercise variables for detection of coronary artery disease in men with diabetes mellitus.

Sixty-eight men with diabetes mellitus (mean age 53 +/- 10 years) and no symptoms of cardiac dysfunction enrolled in a long-range study for detection of latent coronary artery disease. The testing included maximal treadmill stress with thallium-201 scintigraphy and echocardiography. Radionuclide angiography was available in 35 men (52%), and 24 (35%) had gated scanning with exercise. Of the 68 patients, 14 (21%) had a mild (9 patients) or moderate (5 patients) decrease in ejection fraction on radionuclide angiography, echocardiography or both. Fifty-two men agreed to remain in the study and have been followed for 12 to 18 months (mean 41 +/- 19). Ten coronary events have occurred. Four of the men died (2 suddenly) and 6 have angina pectoris. Three patients have had vascular complications. Of the clinical and exercise variables studied, exercise duration effectively predicted an adverse outcome, while the odds ratio in favor of a coronary event increased by 36 times in those with thallium-201 defects and 7 times in those with ST-segment changes on exercise. Radionuclide angiographic responses during exercise were abnormal in 5 of 6 patients with events, but were also abnormal in 12 of 29 men (41%) who did not have coronary artery disease. Clinical variables such as blood pressure, cholesterol level and family history were not predictive of outcome, nor was maximal heart rate during exercise. Thus, diabetic mean who can exercise for 440 seconds on a treadmill using a bruce protocol are at low risk of a coronary event.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1985

The significance of repeated exercise testing with thallium-201 scanning in asymptomatic diabetic males.

This study was conducted with asymptomatic middle-aged male subjects with diabetes mellitus to detect latent cardiac disease using noninvasive techniques. One group of 38 diabetic males (mean age 50.5 +/- 10.2 years) and a group of 15 normal males (mean age 46.9 +/- 10.0 years) participated in the initial trial; 13 diabetic patients and 7 control subjects were restudied 1-2 years later. Maximal treadmill exercise with a Bruce protocol and myocardial scintigraphy with thallium-201(201Tl) were used. Diabetic subjects on initial examination and retesting achieved a lower maximal heart rate and duration of exercise than control subjects. Abnormal electrocardiographic changes, thallium defects, or both were observed in 23/38 diabetic males (60.5%) on the first study and only one 65-year-old control subject had such findings. On retesting, the control subjects had no abnormalities while 76.9% of diabetic subjects had either 201Tl defects or ECG changes. We conclude that despite the fact that none of diabetic males had any clinical evidence or symptoms of heart disease, this high-risk group demonstrated abnormalities on exercise testing that merit careful subsequent evaluation and followup and could be an effective method of detecting early cardiac disease.

Adult↗
PubMed1984

Left ventricular ejection times during exercise testing with scintigraphy. Their use in the detection of ischemic heart disease.

Left ventricular ejection times ( LVETs ) were obtained in a group of 20 control subjects (group 1) during maximal treadmill exercise testing, using a Bruce protocol, and in conjunction with myocardial scintigraphy. Heart rates (HRs) and LVETs were recorded during standing rest, each minute of exercise, and for eight minutes in the postexercise period. A linear regression equation was constructed and separate correction factors of 1.04 X HR + observed LVET (correlation coefficient, -.86) for the exercise period and 0.73 X HR + LVET (correlation coefficient, -.71) for the postexercise period were derived. The LVETs were also recorded in 31 subjects with positive ECGs and defects on myocardial scanning with thallous chloride TL201 (group 2) during a similar exercise protocol. Comparison of groups 1 and 2 disclosed that the former had a higher HR and shorter LVET than the latter at peak effort (consonant with the significantly longer duration of exercise achieved by the control subjects). The LVETs in group 1 remained significantly shorter than that of group 2 through the fifth minute postexercise. In the postexercise period, the LVET indexes were significantly shorter in group 1 than group 2 at 1, 3, and 5 minutes. Subjects with presumptive coronary disease (positive ECG and defects on thallium 201 scanning) not only have a decreased exercise tolerance and HR, but after exercise, their ejection times are substantially longer than in normal subjects. This may be attributed to a slower rate of ejection in patients with coronary disease when venous pooling on quiet standing after exercise delivers a smaller volume to the heart. In normal subjects, the lesser volume may be ejected more rapidly.

Adult↗
PubMed1980

Systolic anterior motion of the mitral valve with and without asymmetric septal hypertrophy. Role of left ventricular posterior wall motion.

Abnormal systolic anterior (SAM) motion of the mitral valve without asymmetric hypertrophy of the interventricular septum was observed in 16 patients (group 1). 5 of the 16 patients had no other evidence of heart disease and the remaining 11 had a variety of cardiac disorders. Left ventricular dimensions, septal and posterior wall thickness, left ventricular ejection fraction, the mean velocity of circumferential fiber shortening, and the mean velocity of the posterior wall and septal contraction was measured by echocardiography in all patients in group 1. These measurements were compared with similar measurements in 14 patients with idiopathic hypertrophic subaortic stenosis (group 2) and in 11 normal subjects (group 3) to evaluate the role of the left ventricular contractility with particular reference to the left ventricular posterior wall motion in production of SAM. All patients with SAM (groups 1 and 2) showed significantly higher indexes of left ventricular contractility, particularly posterior wall velocity, and normalized mean posterior wall velocity, when compared to the normal subjects. The significantly higher posterior wall and the normalized mean posterior wall velocities in all patients with SAM suggest that the exaggerated systolic anterior motion of the left ventricular posterior wall plays an important role in production of SAM in the presence or absence of asymmetric septal hypertrophy.

Adult↗
PubMed1979

Incidence of mitral valve prolapse in subjects with thoracic skeletal abnormalities--a prospective study.

The incidence of mitral valve prolapse (MVP) in 80 patients with various thoracic skeletal abnormalities (TSA) was examined prospectively using compete history and physical examination, chest x-rays, electrocardiography, phonocardiography, and echocardiography. There were 76 males and four females, ranging in age from 18 to 80 years. Thirty-four patients had narrow anteroposterior diameter of the chest (asthenic habitus) (Group 1), 13 had straight back (Group 2), and 33 had pectus excavatum (Group 3). Twenty-five of the 80 patients (31 per cent) had evidence of MVP, 22 by echocardiographic criteria and three by phonocardiographic criteria. The incidence of MVP in this predominantly male population was substantially higher than that reported in the general adult population. Thoracic skeletal abnormality is an important nonauscultatory feature of mitral valve prolapse syndrome. The association between TSA and MVP may be a manifestation of a single connective tissue defect during embryonic development of the bony thoracic cage and the atrioventricular valves. All patients with TSA, even when asymptomatic, should be screened for MVP by noninvasive investigations. The recognition of MVP in patients with TSA may be of potential value in prevention of life-threatening endocarditis and cardiac arrhythmia.

Adolescent↗
PubMed1976

Frequency-force relationships of mammalian ventricular muscle in vivo and in vitro.

The change in contractility with increasing heart rate was studied in the left ventricle of dogs and in isolated trabeculae carneae of cats. For some of the studies in situ a transient isovolumic state was created by aortic occlusion. At physiological temperatures the frequency-force relationship is flatter than at room temperature and at the same temperature it is flatter in vivo than in vitro. The frequency-(dF/dt)max relationship is steeper than the frequency-force relationship at both temperatures in vivo and in vitro. The frequency-(dF/dt)max relationship is steeper in vitro than it is in situ, although the discrepancy is less marked than in the case of the frequency-force relationship. It is concluded that "staircase" plays less of a physiological role in adjustment of contractile state in situ than might be inferred from studies of isolated tissue.

Animals↗
PubMed1975

Complications of selective coronary arteriography by the Judkins technique and their prevention.

Complications encountered during 351 selective coronary artery and coronary artery bypass examinations performed by the Judkins technique are reviewed. The over-all incidence of cardiac and peripheral vascular complications was 3.13 per cent. The cardiac complications included four ventricular fibrillations and one acute myocardial infarction. Peripheral vascular complications included three femoral artery thromboses, two peripheral emboli, and one probable cerebral embolus. There was one death. The incidence of cardiac complications was not significantly different from that reported in the literature with the Sones technique and local arterial complications were significantly lower than those reported with the Sones technique. The causes of individual complications are analyzed and measures to minimize these complications are described. The Judkins technique is a simple, reliable, quick, and safe method of selective coronary arteriography. The incidence of complications can be kept at an acceptably low level by stringent observation of every minor detail of the technique.

Adult↗
PubMed1975

The action of ethanol upon the action potential and contraction of ventricular muscle.

Isolated isometric ventricular muscle of frogs and cats was studied. Perfusing solutions were played directly on the muscle to permit rapid exchange of the extracellular space. Developed force and maximal rate of rise of force were measured in all studies and action potentials (AP) were recorded in some. For both species low concentrations of ethanol (75 degrees mg/l) potentiate contraction. Higher concentrations ( greater than or equal to 750 mg/l) depress contraction progressively with increasing concentration. Concentrations which depress contraction, e.g., 3-4.5 gm/l, usually shorten AP duration. The shortening of AP duration can occur even though contractile force does not fall and, conversely, force may fall while AP duration is unaffected. When 10 mM caffeine is added to the perfusate of either species, AP duration is prolonged and contraction is potentiated. If both ethanol (4.5 gm/l) and 10 mM caffeine are added simultaneously to the perfusate, there is a rapid (within 4 beats) increase in AP duration and an initial depression of contraction, followed by a further increase in AP duration and a significant potentiation of contraction. The steady state contraction is less than with caffeine alone. These preliminary studies suggest that ethanol may depress contraction both by shortening AP duration and by a direct effect upon the contractile apparatus.

Action Potentials↗
PubMed1970

Determinants of pulmonary blood volume.

Pulmonary blood volume was determined by the radiocardiographic technique in 49 patients coming to cardiac catheterization. Since this method has not been directly compared with the more commonly used double injection of dye. 25 comparisons were carried out in 13 patients of the series. Agreement was good over a range of 4.5-21.1 heart cycles since there was no statistically significant difference between transit time values measured by the two methods. The relation of pulmonary blood volume to other hemodynamic factors in these 49 patients, with and without cardiac or pulmonary disease, was evaluated by means of multiple regression analysis. The analysis carried out for mean transit time indicates that this parameter varies predominately with flow. Pulmonary blood volume, in this series of resting recumbent individuals, varies to a significant degree only with total blood volume and with pulmonary venous pressure. No parameters of vascular distensibility, such as pulmonary vascular resistance, were found to affect the volume of blood in the lungs. The fact that variations in pulmonary blood volume among the subjects could be described by a multiple regression equation linear with respect to total blood volume and pulmonary venous pressure indicates that these variations are the result of passive distention of components of the vascular bed.

Adult↗