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Biomedical subjects

B S Lewis

Publications and source records attributed to B S Lewis.

At least 127 records · Page 7Linked to original sources
PubMed1987

Usefulness of echocardiographically determined mitral leaflet motion for diagnosis of mitral valve prolapse in 17- and 18-year-old men.

Mitral leaflet motion during systole was studied by echocardiography in 102 healthy young men. Mean posterior maximal leaflet motion was 2 +/- 1 mm behind the CD line on 2-dimensionally (2-D) directed M-mode examination. On the apical 4-chamber cross-sectional view a mean area of 0.34 +/- 0.24 mm2 was contained by the mitral leaflets above the plane of the mitral anulus. Elevated values on the M-mode view (greater than or equal to 4 mm) compared with the 2-D 4-chamber view (greater than or equal to 0.70 mm2) were discordant, with 90% (18 of 20) of the elevated values found in 1 view only. Thus, there is a wide spectrum of mitral leaflet motion in asymptomatic young men. The value of the echocardiogram in diagnosis of mitral valve prolapse is questionable because any cutoff point between normal and abnormal is arbitrary and the degree of motion has not been shown to correlate with morbidity or mortality.

Adolescent↗
PubMed1987

Chronotropic effect of hydralazine and its mechanism of symptomatic sinus bradycardia.

The positive chronotropic effect of hydralazine was studied in 9 patients with symptomatic sinus bradycardia. Hydralazine was given in an intravenous dose of 0.15 mg/kg and heart rate, blood pressure, sinoatrial conduction time (Narula method) and corrected sinus node recovery time were measured. The effect of hydralazine was also studied after total autonomic nervous system blockade using 0.04 mg/kg of atropine and 0.2 mg/kg of propranolol intravenously. In the control state hydralazine produced an increase of 28 +/- 15% (mean +/- standard deviation) in heart rate, and this was essentially due to a decrease in sinoatrial conduction time (by 32 +/- 32%, p less than 0.05). Corrected sinus node recovery time also tended to shorten (decrease of 21 +/- 34%, difference not significant). After total autonomic blockade intrinsic heart rate did not change or increased very little (9 +/- 14%) after administration of hydralazine and there was no consistent change in sinoatrial conduction and corrected sinus node recovery times. The small residual effect of hydralazine on heart rate was related to incomplete autonomic blockade, since the effect of postural change (standing) on heart rate was also not totally abolished. The study showed that the positive chronotropic effect of hydralazine was mainly due to a change in sinoatrial conduction with a smaller change in corrected sinus node recovery time, and the major chronotropic effect of the drug was mediated by the autonomic nervous system.

Aged↗
PubMed1987

Effect of captopril on left ventricular end-systolic pressure-volume and stress-shortening relations in severe cardiac failure.

The effects of captopril on cardiovascular dynamics and left ventricular (LV) contractility were studied in 11 patients with severe congestive heart failure and very poor global LV function. Pressures were measured using a flow-guided catheter, cardiac output by thermodilution, and LV contraction and ejection fraction by simultaneous radionuclide angiography. Ventricular loading conditions were altered by sublingual isosorbide dinitrate to facilitate construction of LV pressure-volume and stress-shortening curves. Captopril decreased mean arterial pressure (p less than 0.02) and systemic vascular resistance, while stroke and cardiac index increased in most patients. Left ventricular ejection fraction increased from 18 +/- 5 to 22 +/- 7% (p less than 0.05), but contractility, assessed from end-systolic pressure-volume and end-systolic pressure-shortening relations, was unchanged or decreased slightly. Heart rate and double product also tended to decrease. In contrast, arteriovenous oxygen difference widened and calculated total oxygen consumption increased during captopril therapy (p less than 0.05). The study showed that captopril improved forward blood flow, total oxygen extraction, and LV ejection fraction following the decrease impedance to LV emptying but not at the expense of an increase in ventricular contractility. This makes captopril an attractive drug for patients with end-stage cardiac failure and a severely damaged myocardium.

Aged↗
PubMed1987

Left ventricular function during physiological cardiac pacing: relation to rate, pacing mode, and underlying myocardial disease.

The hemodynamic effects of cardiac pacing at different rates and in different modes were studied in 21 patients who were candidates for permanent pacemaker implantation. Nine of these had primary conduction disturbances (PCD), ten had ischemic heart disease (IHD), seven with additional cardiac failure (CHF), and two had hypertrophic cardiomyopathy (HCM). In patients with PCD, atrial (AOO) and AV sequential (DVI) pacing did not change systolic blood pressure and pulse pressure but ventricular (VVI) pacing caused a progressive fall in these measurements, especially as heart rate increased. Ventricular volume and stroke volume (counts) derived from radionuclide ventriculography (RVG) decreased progressively with higher pacing rates, especially during VVI pacing. Cardiac output was maintained during VVI pacing by the increase in heart rate; during AOO and DVI pacing, cardiac output increased. Similar but more marked differences were observed in patients with IHD and CHF and the changes were even greater in the patients with HCM. Left ventricular (LV) ejection fraction changed little with increasing heart rate in PCD but decreased progressively with the onset of ischemia in IHD and CHF. There was no difference in ejection fraction in the different pacing modes. Graphs related to LV contractility (end-systolic pressure-volume relations) showed that AOO pacing produced the highest and VVI pacing produced the lowest curves of myocardial contractility in all patient groups, except that at higher rates the AOO curve shifted down again in patients with IHD and CHF, presumably with the onset of myocardial ischemia. This study showed that physiological pacing produced the best hemodynamic results in all patient groups. Higher pacing rates should be avoided in patients with ischemic heart disease while VVI pacing should not be used in patients with HCM. Blood pressure and RVG studies during temporary pacing are useful in selecting the optimal pacing system in an individual patient when the clinical choice is not clear.

Bradycardia↗
PubMed1987

Left ventricular function from end-systolic stress-shortening relations in mitral valve prolapse.

Left ventricular (LV) function was studied from end-systolic stress-shortening relations in 13 patients with mitral valve prolapse (MVP). Studies were made noninvasively using M-mode echocardiography with blood pressure measurements on the right arm from a Baumanometer cuff. Fifteen age and sex-matched normal subjects formed the control group. LV end-diastolic dimension was normal in MVP, while shortening fraction (p less than 0.05) and velocity of circumferential fiber shortening (mean Vcf) in the short axis of the ventricle were increased (p less than 0.05). Ventricular afterload, as measured by meridional end-systolic stress was reduced in MVP (p less than 0.01) but the slope of the stress-shortening curve was not different form normal. The decrease in end-systolic stress was related to the severity of prolapse (r = 0.63, p less than 0.05). The study implied that mid- or basal LV contractility was normal in MVP. The increased shortening fraction of the LV minor axis was in keeping with geometrical changes and a reduced ventricular afterload.

Adolescent↗
PubMed1987

Peripheral vascular disease in a middle-aged population sample. The Jerusalem Lipid Research Clinic Prevalence Study.

Peripheral artery status and prevalence of peripheral vascular disease were studied in a sample of 1,036 men and 556 women, residents of Jerusalem. Ankle blood pressures determined by the Doppler ultrasound technique (Parks Electronic Lab, USA), were higher in men than in women and increased with age. In a multivariable regression analysis, systolic blood pressure and plasma cholesterol levels were significantly and inversely related to the ankle/arm blood pressure in men, and alcohol intake was inversely associated in women. The prevalence of peripheral vascular disease, as determined by symptoms of intermittent claudication, was 1.3% in men and 1.8% in women; absent pedal pulses were found in 1.1% of the men and in 2.0% of the women; leg pain on the treadmill was a reason for termination of exercise in 3.7% of the men and in 5.4% of the women and an ankle/arm blood pressure ratio of less than 0.90 in 4.2% of the men and in 5.4% of the women. The overlapping of the diagnostic criteria was low. No consistent determinants of the various measures of peripheral vascular status were found. In multivariable logistic models, cigarette smoking was significantly associated with intermittent claudication [Odd ratio (OR) = 3.03, 95% confidence interval (CI) 1.27 to 7.26], age was associated with leg pain on the treadmill (OR = 1.91, 95% CI 1.08 to 3.40 in men and OR 3.52, 95% CI 1.52 to 8.16 in women), body mass index was associated with absent and diminished pulses in women (OR = 1.61, 95% CI 1.07 to 2.42, systolic blood pressure was associated with an ankle/arm ratio of less than 0.90 in men (OR = 1.35, 95% CI 1.01 to 1.81), and glucose was associated with absent and diminished pulses in women (OR = 1.20, 95% CI 1.00 to 1.44).

Adult↗
PubMed1986

Bendazac prevents cyanate binding to soluble lens proteins and cyanate-induced phase-separation opacities in vitro: a possible mechanism by which bendazac could delay cataract.

The reaction of lens proteins with cyanate (carbamylation) causes many changes seen in human cataract including disruption of the protein conformations. Bendazac, a putative anti-cataract drug, decreases the binding of cyanate to lens proteins and prevents the cyanate-induced elevation of the phase separation temperature in incubated rat lenses. Its major metabolite, 5-hydroxybendazac, also inhibits the binding of cyanate to lens proteins even when it is present only during a pre-incubation period. The metabolite is more effective than the parent compound.

Animals↗
PubMed1986

Effect of mechanical ventilation and volume loading on left ventricular performance in premature infants with respiratory distress syndrome.

Left ventricular (LV) performance was assessed by echocardiography in 19 premature infants with severe respiratory distress syndrome. Measurements of LV size and function were made from digitized M-mode echocardiographic data in 14 babies (group 1) before and during treatment with mechanical ventilation and positive end-expiratory pressure. During ventilation, maximum LV dimension decreased (p = .001) as did peak filling rate (p = .01). LV shortening fraction decreased slightly (p = .05). There were marked reductions in calculated stroke volume (SV) (p = .001) and cardiac output (p = .0001) but systemic BP was unchanged, presumably due to peripheral vasoconstriction. The effect of simultaneous volume loading was studied in five other babies (group 2) who were ventilated under similar conditions. Blood transfusion with packed cells (10 mg/kg) prevented the fall in LV filling rate, while LV dimensions (max, p = .01; min, p = .02), SV (p = .05), cardiac output (p = .05), and systolic BP (p = .05) increased. This indicates that a low preload was responsible for the decreases observed in group 1.

Blood Cells↗
PubMed1986

Spontaneous pneumothorax and mitral valve prolapse.

We searched for mitral valve prolapse in patients with spontaneous pneumothorax to test the hypothesis that both may be part of a common disorder of connective tissue. Echocardiographic mitral valve prolapse was found in 11 (50 percent) of 22 patients who had suffered spontaneous pneumothorax compared to four (10 percent) of 40 age-matched control subjects (p less than 0.01). The body mass index (BMI) (weight/height2) was lower (p less than 0.001) in the group with pneumothorax; in five patients who were the thinnest in the study (BMI less than 2 standard deviations lower than mean normal value), mitral valve prolapse was present in four. The finding of a strong association of spontaneous pneumothorax with mitral valve prolapse, especially in subjects with an abnormal body build, suggests that in many patients, spontaneous pneumothorax may be a manifestation of a systemic abnormality of connective tissue.

Adult↗
PubMed1986

Prevalence of postural T wave changes in mitral valve prolapse: a quantitative study.

The abnormal ECG T wave changes associated with mitral valve prolapse (MVP) were studied and quantitated in a group of 36 asymptomatic individuals with MVP and compared with a 27-member control group. The mean frontal plane T wave axis shifted markedly leftward on standing, with T wave axis less than or equal to 0 degrees in 16 (44%) of the subjects with MVP vs. only 2 (7.4%) of the control group, while the QRS-T angle widened to more than 60 degrees in 18 (50%) of those with MVP. Marked left axis deviation of the T wave on standing with T wave axis less than or equal to -30 degrees was found only in subjects with MVP, and their QTc interval was longer, P less than 0.05. In 11 subjects with mitral valve bowing or rounding on the echocardiogram (i.e., less than 2 mm posterior mitral valve displacement), intermediate grades of T wave axis shifts were seen.

Adolescent↗
PubMed1985

Can total coronary occlusions be predicted from a previous coronary arteriogram?

We studied the site, severity, and coronary angiographic morphology of coronary lesions and their ability to predict progression of coronary narrowing and obstruction of coronary arteries. Twenty-six patients who had 94 lesions at the time of first angiography were followed for a mean of 29 +/- 17 (SD) months. Progression of disease or obstruction of a vessel occurred in 11 lesions (12%): eight new total obstructions (8.5%) and three subtotal (3%). Narrowings of greater than 75% of the luminal diameter were more likely to become totally obstructed than less severe narrowings (P = 0.01), but three total occlusions occurred at sites where mild disease had been present previously. Lesions in patients with double or triple vessel disease showed a marginally greater tendency to become totally occluded than in patients with single vessel disease (P less than 0.1). We found no relationship between new total obstructions and the angiographic morphology of the lesion (smooth or irregular) nor with its length or position in the artery or the extent of atheroma in the vessel.

Adult↗
PubMed1985

Psychotropic drugs and long QT syndromes: case reports.

Two depressed patients with long QT syndrome who experienced torsade de pointes ventricular tachycardia when treated with psychotropic drugs are discussed. These cases emphasize the significance of electrocardiographic evaluation of depressed patients, particularly in patients who show evidence of a long QT interval.

Aged↗
PubMed1985

Treadmill exercise testing in a middle-aged Jerusalem population sample. The Jerusalem Lipid Research Clinic Prevalence Study.

We studied determinants of the exercising physical capacity of 1,640 subjects (1,043 men and 597 women) using the Bruce protocol as modified by Sheffield. These participants represented a sample of parents of 17-year-old adolescents living in Jerusalem. Apparently healthy participants underwent a graded treadmill exercise test (88% of the men and 87% of the women). Exercise was terminated when the subject achieved a heart rate of 85 to 90% of the predicted maximal heart rate or could not continue for other reasons, mainly fatigue or weakness. Exercise performance was assessed according to time on the treadmill. On univariate analysis, duration of exercise was related in both sexes to age, country of origin, reported physical exercise, resting heart rate, systolic and diastolic blood pressure, body mass index and plasma lipids and lipoproteins. In multivariate analysis, time was related to age, body mass index, heart rate and habitual physical exercise in both men and women, and to systolic and diastolic blood pressure in men only. Cigarette smoking and plasma lipid levels were not independently related to time on the treadmill in either sex. Ethnic differences were observed.

Age Factors↗