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Biomedical subjects

E Schechter

Publications and source records attributed to E Schechter.

At least 37 records · Page 2Linked to original sources
PubMed1988

Noninvasive evaluation of aortic stenosis severity utilizing Doppler ultrasound and electrical bioimpedance.

Aortic valve area was calculated noninvasively in 30 patients with aortic stenosis undergoing cardiac catheterization. Continuous wave Doppler ultrasound was employed to estimate the mean transvalvular pressure gradient. The mean left ventricular outflow tract flow velocity and cross-sectional area were determined from pulsed Doppler and two-dimensional ultrasound recordings. Electrical transthoracic bioimpedance cardiography performed simultaneously with the ultrasonic study and repeated at the time of catheterization measured heart rate, systolic ejection period and cardiac output. These noninvasive data permitted calculation of aortic valve area using the Gorlin equation (range 0.21 to 1.75 cm2) and the continuity equation (range 0.25 to 1.9 cm2). Subsequent cardiac catheterization showed valve area to range from 0.21 to 1.75 cm2. The mean Doppler pressure gradient estimate was highly predictive of the gradient measured at catheterization (r = +0.92, SEE = 10). Bioimpedance cardiac output measurements agreed with the average of Fick and indicator dye estimates (r = +0.90, SEE = 0.52). Valve area estimates utilizing continuous wave Doppler ultrasound and electrical bioimpedance were superior (r = +0.91, SEE = 0.12) to estimates obtained utilizing the continuity equation (r = +0.76, SEE = 0.29) and were more reliable in the detection of patients with severe aortic stenosis (9 of 11 versus 6 of 11). These data show that 1) electrical bioimpedance methods accurately estimate cardiac output in the presence of aortic stenosis; 2) the hybridized bioimpedance-Doppler ultrasound method yields accurate estimates of aortic stenosis area; and 3) the speed, accuracy and cost-effectiveness of aortic stenosis evaluation may be improved by this hybridized approach.

Adult↗
PubMed1986

Late thrombolysis with intracoronary streptokinase after myocardial infarction.

This patient had a myocardial infarction 4 years after coronary bypass grafting. Catheterization 1 month later revealed occlusion of the graft to the posterior descending by what appeared to be a clot. On each of 3 successive days, infusion of streptokinase accomplished recanalization of the graft. After the third treatment, he showed marked symptomatic improvement. Recanalization may be successful as late as 1 month after occlusion and repeated infusions of streptokinase over a period of days can be carried out safely and without loss of effectiveness.

Coronary Artery Bypass↗
PubMed1984

Afterdepolarizations as a mechanism for the long QT syndrome: electrophysiologic studies of a case.

A young woman with palpitation and syncope was found to have ventricular tachyarrhythmia and a congenital long QT interval. The QT interval was shortened and the arrhythmia suppressed by propranolol. Electrograms recorded at various sites in both ventricles revealed a distinct diastolic slow wave that followed the T wave and measured 1.1 mV. Epinephrine infusion and emotion augumented this diastolic wave and induced ventricular ectopic complexes arising from this potential. Similar endocardial recordings in eight patients without a long QT interval showed diastolic slow waves that never exceeded 0.28 mV. In normal canine myocardium, afterdepolarizations can be induced by norepinephrine and blocked by propranolol. These findings suggest that the long QT syndrome is associated with abnormally large afterdepolarizations in ventricular myocardial cells, which are enhanced by beta-adrenergic stimulation to attain threshold and produce firing.

Adult↗
PubMed1983

Physiologic responses to epinephrine infusion: the basis for a new stress test for coronary artery disease.

Since many patients with chest pain cannot exercise adequately, an alternative stress would be useful to evaluate coronary reserve. We studied the physiologic responses to epinephrine to assess its potential. We report on 39 patients with chest pain. Doses from 0.03 to 0.30 micrograms/kg/min were administered intravenously. Heart rate increased from 72 +/- 10 to 86 +/- 12 bpm (mean +/- SD), systolic blood pressure (BP) from 122 +/- 20 to 158 +/- 18 mm Hg (increased afterload), and rate-pressure product/100 from 88 +/- 21 to 133 +/- 18. Rate-corrected pre-ejection period decreased from 141 +/- 23 to 92 +/- 14 msec and LVET/PEP ratio from 0.41 +/- 0.1 to 0.24 +/- 0.05 (increased contractility). Increased afterload and contractility increased myocardial oxygen demand. Simultaneously diastolic time and BP decreased, reducing myocardial blood supply. The endocardial viability ratio fell from 1.27 +/- 0.3 to 0.80 +/- 0.2. These data suggest that epinephrine infusion would be a useful stress test for coronary disease and are supported by a sensitivity of 87% and specificity of 100% in 23 patients with known coronary anatomy.

Adult↗
PubMed1983

Direct endocardial recording from an accessory atrioventricular pathway: localization of the site of block, effect of antiarrhythmic drugs, and attempt at nonsurgical ablation.

We recorded a discrete 0.95 mV potential consistent with accessory atrioventricular pathway (AP) activation during serial electrophysiologic studies in a patient with Ebstein's anomaly and Wolff-Parkinson-White syndrome. Bipolar pacing from the catheter electrode in which the AP potential was recorded resulted in a stimulus-ventricle interval identical to the AP-ventricle interval during antegrade conduction, and a stimulus-atrium interval identical to the AP-atrium interval during retrograde conduction. With the patient in the drug-free state, antegrade AP block during atrial pacing and retrograde AP block during ventricular pacing occurred distal to the AP potential (AP-ventricle junction and AP-atrium junction, respectively), supporting the "impedance mismatch" hypothesis. Procainamide and disopyramide each lengthened the antegrade AP effective refractory period by affecting the AP-ventricle junction (possibly by decreasing the current generated by the AP). Both drugs also lengthened the retrograde AP effective refractory period but produced a greater effect on the ventricle-AP junction than on the AP-atrium junction, suggesting marginal geometry of the former. R wave synchronous shocks of 160 and 320 W-sec delivered between the catheter electrode recording the largest unipolar AP potential and a skin electrode produced transient, complete, antegrade block over the AP, suggesting the feasibility of this new nonsurgical technique for AP ablation.

Adult↗
PubMed1981

Plasma apolipoprotein B and VLDL-, LDL-, and HDL-cholesterol as risk factors in the development of coronary artery disease in male patients examined by angiography.

To assess the potential use of plasma apolipoprotein B (ApoB) as a risk factor for coronary artery disease, this apolipoprotein was quantified by electroimmunoassay in 161 male patients with angiographically documented coronary atherosclerosis and 72 male patients with normal coronary arteries. In addition to ApoB, the analyzed lipoprotein profile included plasma total cholesterol, plasma triglyceride and VLDL-, LDL- and HDL-cholesterol levels. Age, plasma cholesterol, triglyceride, and VLDL- and LDL-cholesterol were significantly greater (P less than 0.05) for patients with coronary artery disease than for patients with normal arteries. In contrast, there was no difference in the mean levels of HDL-cholesterol between these 2 groups of patients. However, patients with HDL-cholesterol les than 40 mg/dl had a higher rate of coronary artery disease than those with HDL-cholesterol greater than 40 mg/dl (P less than 0.05). The results of multivariate analysis showed that age and plasma cholesterol were the 2 variables most significantly (P less than 0.01) related to the presence of coronary artery disease. However, in a subgroup of patients with plasma cholesterol less than 265 mg/dl, the most reliable variable was ApoB (P less than 0.01). For patients under 50 years of age ApoB and LDL-cholesterol were the most significant variables (P less than 0.05), whereas for patients at 50 years of age or older VLDL-cholesterol was the most significant variable (P less than 0.01). Results of this study indicate that measurement of ApoB may offer important predictive value for coronary artery disease, especially at lower levels of plasma cholesterol. Whether this and other conclusions also apply to general population, remains to be established in future studies.

Adolescent↗
PubMed1978

Transmural myocardial infarction with the prolapsing mitral-leaflet syndrome and normal coronary arteries.

Clinical and electrocardiographic evidence of transmural myocardial infarction developed in two patients (a woman, age 38, and a boy, age 17) with prolapsing mitral-leaflet syndrome. Both had normal coronary angiograms and normal plasma lipid levels. Left ventricular angiography showed dyskinetic areas in both patients. Coronary artery embolism or prolonged coronary artery spasm may have been the underlying mechanism of production of myocardial infarction.

Acute Disease↗
PubMed1978

Hemodynamic correlates of echocardiographic aortic root motion. Observations on normal subjects and patients with idiopathic hypertrophic subaortic stenosis.

In ten normal subjects, we observed an initial hump in the aortic root echocardiogram after the onset of the QRS complex, following which a sharp anterior motion was noted. The onset of the anterior motion of the aortic root coincided with the onset of the upstroke of the aortic root pressure pulse and the onset of the velocity signal in five of seven patients with coronary arterial disease; in the other two, the anterior aortic motion followed the onset of the pressure and velocity signal by 10 msec. The aortic root echocardiogram was abnormal in patients with idiopathic hypertrophic subaortic stenosis; the slope (normalized for the scales of time and depth) in early systole was steeper and in the latter part of systole was flatter than normal in these patients. The slope in early diastole was flatter and the slope due to atrial contraction was steeper in the patients with idiopathic hypertrophic subaortic stenosis than in the normal subjects. These features were consistent with rapid ejection in early systole and slow filling in the early phase of ventricular diastole in idiopathic hypertrophic subaortic stenosis. Fourier analysis of the wave form of the aortic root allowed separation between patients with idiopathic hypertrophic subaortic stenosis and normal subjects.

Adult↗
PubMed1975

Coronary bypass surgery. Value of maximal exercise testing in assessment of results.

To evaluate the relationship of results of maximal treadmill testing and results of saphenous vein bypass surgery (SVG), 30 patients underwent a maximal treadmill test before and after SVG; an additional 39 had results of postoperative exercise testing available. These patients were part of a group of 91 patients (95% of 96 survivors) who had complete right- and left-heart catheterizations and coronary angiography before and after operation. Twenty-one per cent had improved ejection fractions postoperatively; in 32% ejection fractions were worse. Duration of maximal treadmill exercise correlated poorly with ejection fraction changes or graft patency. Rate-pressure product (RPP) was usually lower postoperatively in patients with worse ejection fractions, primarily because of a low systolic blood pressure at maximum exercise. RPP postoperatively of less than 25,000 almost always meant poor surgical results, either graft occlusion or poor left ventricular function, while RPP of more than 30,000 meant that left ventricular function was preserved and all grafts or the graft to the anterior descending were patent. Thus, success or failure of SVG in these groups may be predicted without postoperative catheterization. An open graft to the anterior descending coronary generally insured a high RPP with exercise, even if other grafts were closed, as long as ventricular function remained good.

Angina Pectoris↗