PubMed Health⌕ Search

Biomedical subjects

A Shefer

Publications and source records attributed to A Shefer.

54 records · Page 3Linked to original sources
PubMed1984

Improvement in regional ventricular function after percutaneous transluminal coronary angioplasty.

We performed atrial pacing and radionuclide ventriculography in 12 patients before and after percutaneous transluminal coronary angioplasty (PTCA). Successful dilatation was achieved in 9 patients while in 3 the procedure was unsuccessful. Atrial pacing before PTCA showed ischemic dysfunction of the region supplied by the narrowed coronary artery. Regional ejection fraction decreased by 36 +/- 12% during rapid atrial pacing, while global left ventricular ejection fraction fell by 11 +/- 7% with a secondary increase in end-diastolic and end-systolic ventricular volume with the onset of ischemia. After successful PTCA, ischemic dysfunction was ameliorated or abolished. Measurements made at identical heart rates showed that both global and in particular regional left ventricular ejection fraction were significantly higher after successful angioplasty and did not fall during the stress of atrial pacing. There was no improvement in regional or global LV function in patients in whom angioplasty was not successful. The study showed that nuclear ventriculography with the stress of graded atrial pacing was a useful method for analysing the immediate results of coronary angioplasty and for studying its effects on regional myocardial function.

Adult↗
PubMed1984

The effect of nifedipine on normal and ischemic left ventricular function during atrial pacing stress.

We studied 44 patients (group I: 9 with insignificant disease and group II: 35 with significant coronary artery disease) by nuclear angiography during the controlled increase in heart rate by atrial pacing to evaluate the effect of 20 mg of sublingual nifedipine on left ventricular function. Left ventricular volumes were calculated using count-derived changes: end-diastolic (EDE), end-systolic (ESE), stroke volume (SVE) and cardiac output equivalents (COE) and ejection fraction (EF) and ejection rate (ER) were calculated during basal sinus rhythm (C) and at the maximal atrial pacing (AP) rate with and without nifedipine. In normal subjects, AP decreased ventricular volumes. The administration of nifedipine decreased blood pressure but had no further effect on left ventricular volume. In the ischemic ventricle, AP produced reversible ventricular wall paresis with a smaller decrease in EDE, an increase in ESE and a significant fall in EF. Nifedipine induced a striking improvement in EF and ER. This was probably a consequence of afterload reduction and increased coronary blood flow.

Adult↗
PubMed1983

Survival after sudden obstruction of the left main coronary artery.

Left main coronary artery (LMCA) stenosis occurs in 10% of patients undergoing coronary arteriography, but total occlusion is rare. Goldberg et al reported 6 cases of complete obstruction of the LMCA among 2,200 patients studied arteriographically. Sudden obstruction of the LMCA should be lethal, and we found no report describing survival with sudden obstruction of the LMCA. The present report describes such a patient.

Coronary Angiography↗
PubMed1983

External inspiratory resistance of protective respiratory devices: effects on physical performance and respiratory function.

Twenty subjects wearing protective respirators were studied during submaximal exercise (80% of VO2max) on a treadmill. The protective devices were fitted with canister filters of low expiratory resistance and different inspiratory resistances: (0.3, 1.8, 2.8, 3.4, 3.9, and 4.6 cm H2O X sec/liter). The effect of inspiratory resistance on physical endurance, various physiological parameters, and subjective sensations was examined. With the increase in inspiratory resistance, a significant decrease in physical performance, decrease in tidal volume, increased ratio of inspiratory to expiratory time, increased peak inspiratory pressure, and increased CO2 retention were observed. The difficulty in inspiration correlated significantly to inspiratory resistance and seems to be the main reason for cessation of the effort. No acceptable upper limit for the inspiratory resistance of the canister filters was found. Any decrease in the inspiratory resistance of the mask's filter enhanced endurance and performance.

Adult↗
PubMed1983

Early postoperative assessment of coronary artery bypass surgery using nuclear left ventriculography and atrial pacing.

Nuclear ventriculography (MUGA) was performed in 22 patients at rest and during the stress of right atrial pacing 6 to 8 days after coronary artery bypass surgery. In 7 patients the MUGA-atrial pacing test was positive for ischemia with chest pain, electrocardiographic ST depression and/or a decrease in global left ventricular ejection fraction of greater than 10%. All 7 patients subsequently developed angina pectoris with a positive treadmill test (performed at a median time of 14 months after operation). In 15 patients, the early postoperative MUGA-atrial pacing test was negative. In this group, 3 patients subsequently developed angina pectoris with a positive treadmill test in one. The sensitivity of the 'one week' early postoperative MUGA-atrial pacing in the identification of patients with residual myocardial ischemia was high (88% for positive GXT, p less than 0.0001; 70% for chest pain, p less than 0.005) with 100% specificity. The early postoperative MUGA scan was also useful in predicting later shortness of breath on exertion and there was a significant correlation between the early resting ejection fraction and the exercise capacity of the patient subsequently. The information obtained from an early postoperative MUGA-atrial pacing study may have far-reaching and important practical application in selecting patients for early recatheterization, possible fibrinolysis and/or possible cardiac reoperation.

Adult↗
PubMed1983

Recurrent obstruction and thrombolysis of the right coronary artery.

A patient presented twice with the hyperacute phase of inferior wall myocardial infarction. Emergency coronary angiography was undertaken on each occasion and the occluded right coronary artery reopened by intracoronary thrombolysis using urokinase. The patient subsequently underwent successful percutaneous transluminal coronary angioplasty to dilate the underlying subtotal obstructive lesion in the proximal right coronary artery. The sequence of events in this patient demonstrates that (1) acute coronary thrombolysis can preserve ventricular myocardium, (2) recurrent thrombolysis can be performed successfully in the same artery in the same patient, and (3) coronary angioplasty may be an effective method of dilating the underlying coronary narrowing after coronary thrombolysis.

Adult↗
PubMed1982

Intraaortic balloon counterpulsation in acute myocardial infarction.

Intraaortic balloon counterpulsation was undertaken in 24 patients with acute myocardial infarction. The patients were divided into four groups: severe left ventricular dysfunction (11 patients), mechanical lesions (6), intractable angina pectoris (6) and refractory ventricular tachycardia (1). The clinical condition and the hemodynamic measurements improved dramatically in 21 patients, but there were only 9 long-term survivors. Intraaortic balloon counterpulsation gave the best results in patients with preinfarction angina pectoris or patients with left ventricular dysfunction where the hemodynamic status deteriorated after an acute but reversible cardiovascular event. Numerous local complications were observed.

Adult↗
PubMed1982

Physiological and psychological adaptation to respiratory protective devices.

This study was conducted to investigate the adaptation process to respiratory protective devices (RPD). Twenty healthy subjects were tested at 80% of their Vo2 max for 6 consecutive days with a fitted RPD with an airway resistance of 2.80 +/- 0.07 cm H2O s/1. It was concluded that working with RPD at a work capacity close to maximum for several minutes per day induces a rapid adaptation process. This is demonstrated by an improvement in physiological parameters rather than in subjective sensations.

Adaptation, Physiological↗
PubMed1980

Ventilatory and occlusion-pressure responses to hypercapnia in divers and non-divers.

Ventilatory (VE/PCO2) and occlusion-pressure (P0.1/PCO2) responses to progressive hypercapnia (rebreathing method of Read (1)) were estimated in 20 normal subjects and 22 scuba divers. Indexes of CO2 sensitivity (slopes of response curves) and absolute response values under strong CO2 drive (PCO2 = 60 mmHg) were significantly lower in the diver group. Individual CO2 sensitivity did not correlate with either diving experience or current diving activity. Positively skewed (log-normal) frequency distribution curves of individual CO2 sensitivities were drawn for the divers and for a larger sample of normal controls (using data from other studies). All divers' values fell in the lower range of non-diver control values and about one-third were below the normal range (mean +/- 2 SD) for CO2 sensitivity. We concluded that our divers did not represent a distinct population different from the normal one but rather a group of normal healthy subjects with either an inherent or acquired relatively low CO2 response. The rebreathing technique is strongly advocated as a tool for investigating divers' CO2 sensitivity and its implications in underwater environments.

Adult↗
PubMed1976

Regional ventricular dysfunction in coronary artery disease.

Percentage asynergy, ejection fraction (EF), left ventricular end diastolic pressure (LVEDP) and the site of coronary artery narrowing or obstruction were measured in 69 patients with significant coronary artery disease. Complete obstruction in the first third of the left anterior descending artery (LAD) produced a mean asynergy of 49% associated with an ejection fraction of 40% and a LVEDP of 19mm Hg. The extent of asynergy was modified by the nature of the underlying coronary artery anatomy and the protective circulation. Complete obstruction in the main right coronary artery produced a mean asynergy of 20% associated with an EF of 67% and LVEDP of 6 mm Hg. Complete obstruction in the first third of the circumflex artery produced a mean asynergy of 15% associated with an EF or 74% and LVEDP of 14mm Hg. Subtotal obstruction in the first third of the LAD produced a mean asynergy of 25% associated with an EF of 62% and LVEDP of 7mm Hg. The damage produced by a LAD obstruction was extensive while that of a right or circumflex obstruction was mild. Patients always had a high percentage asynergy after two episodes of myocardial infarction. A negative linear relationship was found between percentage asynergy and EF. There was a rough positive linear relationship between LVEDP and percentage asynergy.

Blood Pressure↗
PubMedDate not supplied

Fatiguing illness among employees in three large state office buildings, California, 1993: was there an outbreak?

UNLABELLED: The objective was to determine if a cluster of chronic fatigue syndrome (CFS)-like illness had occurred among employees in two large state office buildings in northern California, and to identify risk factors for and features of fatiguing illness in this population. DESIGN: case-control study. POPULATION AND SETTING: Over 3300 current employees in two state office buildings and employees in a comparable "control" building. Information was collected on demographic and occupational variables, the occurrence of fatiguing illness for at least one month in the previous year, and the presence of 36 symptoms. A total of 3312 (82%) of 4035 employees returned questionnaires. Overall, 618 (18.7%) persons reported fatigue lasting at least one month; including 382 (11.5%) with fatigue of at least six months' duration and 75 (2.3%) with symptoms compatible with a CFS-like illness. Independent risk factors for fatigue lasting one month or longer were found to be Native American ethnicity (OR 2.4, CI 1.1,5.3), Hispanic ethnicity (OR 1.7, CI 1.3,2.3), female sex (OR 1.5, CI 1.2,1.9), gross household incomes of less than $50,000 (OR 1.3, CI 1.1,1.6), and less than a college education (OR 1.3, CI 1.1,1.6). Similar risks were observed for persons who reported fatigue lasting six months or longer. Female sex (OR 3.2, CI 1.7, 6.4) was the only independent risk factor found for those persons classified as having a CFS-like illness. Case prevalence rates for all three categories of fatigue, as determined by multivariate analysis, were not significantly different among buildings. Despite finding a substantial number of employees with fatiguing illness in the two state office buildings, the prevalence was not significantly different than that for a comparable control building. Previously unidentified risk factors for fatigue of at least one month and at least six months identified in this population included Hispanic ethnicity, not having completed college, and income below $50,000.

Adult↗
PubMedDate not supplied

The effects of m-AMSA on rat isolated heart.

m-AMSA (4'[9-acridinylamino]methansulphon-m-anisidide) is a new cytoxic agent now under clinical trial. We used the rat isolated perfused heart model in order to investigate the cardiac effects of m-AMSA. The results of the dose-response study indicate that m-AMSA has an acute moderate negative inotropic effect. The 90% effect (25% decrease in developed force compared to the control) was observed at drug concentration of 1.5 micrograms/ml. The refractory period (as measured by stimuli of twice diastolic threshold intensity) increased progressively as the drug concentration was increased (up to 2.5 micrograms/ml). Measurements of the strength-duration and strength-interval relationship showed that m-AMSA induced a significant reduction (P less than 0.005) in excitability and prolongation of refactoriness. We suggest that m-AMSA has a membranal cardiotoxic effect in addition to its known intracellular cytotoxic effect.

Aminoacridines↗
PubMedDate not supplied

The effect of quinidine and myocardial ischemia on the isolated rat heart with fat-free diet.

Fat-free diet changes the lipid content and the electrophysiological properties of the rat myocardium. Five percent fat supplementation to the diet does not alter the basic electrophysiological properties but still has a biochemical effect on the lipid content of the myocardium. The purpose of this work was to determine whether these biochemical alterations affect the response of the myocardium to quinidine and ischemia, both of which interact with the lipid component of the membrane. We used strength-duration, strength-interval and threshold of ventricular fibrillation to measure the electrophysiological properties of the isolated rat heart at baseline and after 30 minutes of quinidine perfusion or coronary artery ligation. The fatty acid composition of the myocardium was analyzed. We found that a fat-free diet caused essential fatty-acid deficiency, while 5% fat supplementation had a partial protective effect. Quinidine decreased excitability and increased refractoriness in both groups but had more effect on the fat-free diet hearts group. There was no difference in the ventricular fibrillation threshold. Ischemia increased myocardial excitability in the fat-free diet hearts group and had no effect on refractoriness or ventricular fibrillation threshold. These results support the theory that the lipid composition of the myocardial membrane affects its response to lipophilic drugs and ischemia.

Animals↗