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Biomedical subjects

V S Mathur

Publications and source records attributed to V S Mathur.

At least 55 records · Page 3Linked to original sources
PubMed1982

Premature closure of prosthetic mitral valves as a consequence of gravity.

To determine the influence of gravity on premature closure of prosthetic mitral valves, we studied 17 patients in whom this phenomenon had been observed during routine examination. All patients were in atrial fibrillation and none had aortic incompetence. Patients were studied in multiple positions by means of simultaneous echocardiography, phonocardiography, and cinefluoroscopy. In all patients premature closure was observed when the atrial side of the prosthesis was below the ventricular side, resulting in a downward motion of the occluder inside the valve cage. When patients were studied in positions in which the atrial side of the valve was higher that the ventricular side, premature closure never occurred, even during extremely prolonged diastolic periods. Since minor positional changes, which were found to determine whether premature closure occurred or not, are unlikely to produce significant alterations in pressure and flow across the mitral orifice during diastole, we conclude that position-dependent premature closure of prosthetic mitral valves in patients with atrial fibrillation is best explained by the effect of gravity on the prosthetic occluder. Examination of such patients in multiple positions should be helpful in distinguishing premature valve closure caused by aortic regurgitation from gravity-related presystolic closure. Inability to produce premature closure in patients in whom it had previously been demonstrated in the presence of similar R-R intervals may even prove useful in diagnosing new orifice obstruction.

Atrial Fibrillation↗
PubMed1982

Disposition of four drugs in malnourished children.

Pharmacokinetic studies on antipyrine, chloramphenicol, acetaminophen, and sulphadiazine have been carried out in infants and children suffering from protein-energy malnutrition (PEM). Increased antipyrine plasma half-life in PEM indicated altered mixed oxidative microsomal enzyme activity in hepatocytes. Chloramphenicol was absorbed (ka) as well as eliminated (ke) at slower rates in PEM. The net result was that the comparative bioavailability of the drug was higher in PEM as compared to the control. Observations were similar in the case of sulphadiazine. The rate of absorption (ka) of acetaminophen was not affected in children with PEM, but the elimination rate constant was slower and plasma half-life prolonged. Noticeable improvement was observed within 6-8 weeks of nutritional rehabilitation with respect to chloramphenicol, antipyrine, and acetaminophen pharmacokinetics.

Acetaminophen↗
PubMed1981

Pharmacokinetic study of chloramphenicol in patients with liver disease.

The pharmacokinetics of intravenous chloramphenicol has been studied in 42 patients with liver disease and in 8 controls. The half-life of chloramphenicol (t 1/2) was increased in the various liver disorders, the metabolic clearance rate (MCR) and apparent volume of distribution (Vd) were decreased and the area under the time - concentrations curve (AUC) showed an increase. The t 1/2 of chloramphenicol showed a significant correlation with serum albumin and prothrombin time index.

Acute Disease↗
PubMed1980

Metabolism of sulfadiazine in children with protein calorie malnutrition.

6 children with protein calorie malnutrition (PCM) and 5 control children received a single dose of sulfadiazine (25 mg/kg body weight). Absorption rate constant in the control group was 0.735 +/- 0.058 h-1 and in PCM 0.519 +/- 0.03 h-1. Peak blood levels of the drug were similar in both groups. However, the time to reach the peak was shorter in the control than in the PCM group. Elimination rate constant and half life of the drug were 0.0233 +/- 0.0026 h-1 and 31.78 +/- 3.82 h, respectively, in the PCM group and 0.0332 +/- 0.0022 h-1 and 21.27 +/- 1.51 h, respectively, in the control group. These values differ significantly from each other. The area under the blood concentration-time curve was more than double in the PCM group as compared to the control group. Urinary excretion of the drug in 48 h was significantly more in control (19.3 +/- 1.4 mg/kg body weight) in comparison to the PCM group (13.6 +/- 1.7 mg/kg body weight). However, the free drug concentration in urine/kg body weight was not altered in the PCM group. There was a significant decrease in quantity of acetylated drug in the PCM group as compared to the controls. In view of these observations, therapy with sulfadiazine in children suffering from PCM requires reconsideration.

Acetylation↗
PubMed1980

Is postextrasystolic potentiation dependent on Starling's law? Biplane angiographic studies in normal subjects.

The cineangiograms of 26 normal subjects were analyzed to study the effect of Starling's mechanism on postextrasystolic potentiation. The end-diastolic volumes (single plane and biplane) of the left ventricle were similar in the regular sinus beat before an extrasystole and sequential sinus beats after an extrasystole. However, the ejection fraction, mean normalized systolic ejection rate, mean velocity of fiber shortening and long-axis shortening were consistently larger in the first sinus beat after an extrasystole. We conclude that postextrasystolic potentiation is independent of left ventricular end-diastolic volume in normal human hearts and the compensatory pause after an extrasystole does not result in increased end-diastolic volume.

Angiography↗
PubMed1980

Prolonging life with coronary bypass surgery in patients with three-vessel disease.

In this study we examined survival after coronary bypass surgery in patients with three-vessel disease. First, survival data were analyzed from selected of patients who had a poor prognosis without surgery; second, data were analyzed in subsets classified by severity of disease. The data strongly suggest that patients with three-vessel disease, especially patient with a poor medical prognosis, benefit from coronary bypass surgery.

Actuarial Analysis↗
PubMed1979

Clinical standardization of the new dual cardiac probe.

A new mobile dual cardiac probe has been introduced for measurements of the left ventricular ejection fraction (LVEF). In 28 patients, correlation between LVEFs measured by the dual probe and biplane contrast ventriculography was 0.83. Central and peripheral injections yielded comparable curves, and the resultant LVEFs correlated well (R = 0.95). Correlation between LFEVs determined by the probe and by gated blood pool imaging in 43 patients was also 0.83. In 21 patients given three serial injections of 99mTc-albumin, the mean variation of the ejection fraction was 4.2 +/- 3.2%; however, reproducibility was unsatisfactory using 99mTc-sulfur colloid due to sequestration in hepatic background tissue.

Heart Ventricles↗
PubMed1979

Scintigraphic, electrocardiographic, and enzymatic diagnosis of perioperative myocardial infarction in patients undergoing myocardial revascularization.

To assess the incidence of perioperative myocardial infarction, 214 consecutive patients were evaluated 1-5 days after coronary bypass surgery, using Tc-99m pyrophosphate (TcPPi) myocardial imaging, serial electrocardiograms (ECG), and enzyme levels (SGOT, LDH, CPK). On the basis of the clinical course and scintigraphic, enzymatic, and ECG changes, the diagnosis of perioperative infarction was definite in 17 of 241 cases (7.9%) and probable in six of 241 (2.8%). In all of these 23 patients, TcPPi scans were abnormal; one additional patient had a false-positive scintigram. Only 13 of the 23 had ECG evidence of infarction, but there were no false positives. We set the threshold for abnormality of enzyme changes quite high, owing to experience in more than 900 postoperative patients (SGOT greater than 200, LDH greater than 500, CPK greater than 500 on the same day). Using these criteria, 22 of the 23 infarct patients had abnormal enzymes, and six others were falsely positive. These results indicate a relatively low sensitivity for the ECG in diagnosing perioperative infarction, but the lack of false positives suggests high specificity. The sensitivity and specificity of the enzymes and the TcPPi image were both excellent and quite similar; the main difference was a reduction of certainty of infarction with the enzyme criteria, caused by the six patients whose enzyme values were falsely positive. Considering its sensitivity, specificity, and ability to locate and to a certain extent quantitate necrosis. TcPPi imaging is probably the most valuable means of diagnosing perioperative myocardial infarction.

Clinical Enzyme Tests↗