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Biomedical subjects

V Bhargava

Publications and source records attributed to V Bhargava.

At least 109 records · Page 6Linked to original sources
PubMed1985

Function of the pericardium and pericardioperitoneal canal in elasmobranch fishes.

Previous studies of cardiac function in elasmobranch fishes have not included the influence of the pericardioperitoneal canal on pericardial pressure and volume and thus on cardiac function. Accordingly, we studied the function of the pericardium and pericardioperitoneal canal in sharks and rays. We found negative pericardial pressure that rose to a plateau of approximately 0 mmHg when fluid was infused into the pericardium with the canal undisturbed. However, this pericardial pressure elevation caused severe cardiac tamponade. After the canal was occluded, the pressure plateau was substituted with an exponential rise. We injected radioisotopes into the pericardial cavity and obtained scintigrams several hours later. The scans and counts of body fluids and tissues indicated absorption, disputing the suggestion that the primary function of the canal may be inadequate absorption of pericardial fluid. We conclude that the pericardioperitoneal canal maintains negative pericardial pressure, which is a prerequisite in elasmobranch fishes and may serve to regulate pericardial pressure level to optimize cardiac function in relation to changes in cardiac size.

Absorption↗
PubMed1984

Comparative effects of ionic and nonionic contrast materials on indexes of isovolumic contraction and relaxation in humans.

The effects of contrast media on left ventricular (LV) relaxation as assessed by the time constant of isovolumic relaxation have not previously been studied. A new nonionic contrast agent (iohexol) has been shown to have fewer deleterious effects than standard ionic agents. Nineteen patients received iohexol and sodium meglumine diatrizoate (Renografin-76) in a double-blind, crossover study during left and right coronary arteriography and with simultaneous high-fidelity micromanometer measurements of LV pressure. Neither agent induced significant changes in LV end-diastolic pressure after right or left coronary arteriography. After right coronary arteriography, neither agent produced significant deterioration of peak positive dP/dt or (dP/dt)/DP40 (dP/dt at a developed pressure of 40 mm Hg). However, after right coronary arteriography both agents caused a transient deterioration in peak negative dP/dt and the time constant of isovolumic relaxation (p less than 0.05 at 20 seconds after arteriography). After left coronary arteriography, sodium meglumine diatrizoate induced deterioration of systemic blood pressure (p less than 0.05), peak positive dP/dt (p less than 0.01), (dP/dt)/DP40 (p less than 0.05), peak negative dP/dt (p less than 0.01) and the relaxation time constant (p less than 0.01). These effects were not induced by iohexol. Thus, nonionic contrast media exert negligible alterations on LV function when used for coronary arteriography. The findings are of potential clinical importance in view of the large number of patients with depressed LV function who undergo coronary arteriography.

Coronary Angiography↗
PubMed1984

Growth pattern of intrauterine growth retarded (IUGR) babies in first nine months of life.

Forty-one full term intrauterine growth retarded (IUGR) babies of different maternal etiologies viz. maternal undernutrition (12), small maternal size (12), toxaemia of pregnancy (9) and idiopathic (8) were studied for growth pattern during first 9 months of life. Eighteen fullterm and 11 preterm who were appropriate for gestational age served as controls. These mothers were comparable for age, parity, socioeconomic status, weight and height (except in small size mothers), haemoglobin and plasma albumin (except in undernourished group). The various anthropometric parameters studied were weight, crown-heel length, head circumference, their velocities and ponderal index. The IUGR babies of undernourished mothers had lowest means for weight, crown-heel length and skull circumference. The babies of small sized mothers suffered most in crown-heel length followed by weight. The head growth was not affected in these babies. The IUGR babies of mothers with toxaemia of pregnancy demonstrated a catch up growth for all three parameters. The IUGR babies of idiopathic group showed a spurt in weight gain around 3 to 6 months and a similar spurt for crown heel length and head circumference was observed between 6 to 9 months of age. These babies were close to IUGR babies of mothers with toxaemia of pregnancy at 9 months. The preterm AGA babies also demonstrated a catch up growth for the weight, crown heel length and circumference.

Birth Weight↗
PubMed1983

Radionuclide analysis of peak filling rate, filling fraction, and time to peak filling rate. Response to supine bicycle exercise in normal subjects and patients with coronary disease.

Using gated equilibrium radionuclide angiography, variables of diastolic filling were analyzed at rest and during supine bicycle exercise in normal subjects (Group 1, n = 18), coronary patients with normal resting ejection fractions (Group 2, n = 26), and coronary patients with reduced resting ejection fractions (Group 3, n = 8). Indexes analyzed were peak filling rate and filling fraction during the first third of diastole. At rest, the peak filling rate was significantly lower in coronary patients than in normal subjects (3.18 +/- 0.82 end-diastolic volume [EDV]/s in Group 1 versus 2.41 +/- 0.66 EDV/s in Group 2, p less than 0.005; and 1.34 +/- 0.26 EDV/s in Group 3, p less than 0.001 versus Group 1). These differences persisted at peak exercise. Coronary patients also had significantly lower filling fractions at rest and during exercise than did normal control subjects. The time from end-systole to peak filling rate was longer at rest in patients in Group 2 (203 +/- 52 ms) than in subjects in Group 1 (172 +/- 50 ms, p less than 0.025). This remained true when the time to peak filling was normalized by the R-R interval. Although the exercise time to peak filling was longer in coronary patients in both Groups 2 and 3 than in Group 1, these differences were not apparent when the interval was normalized by the R-R interval. Thus, abnormalities in peak filling rate and filling fraction exist in patients with coronary disease both at rest and during exercise, but large overlaps exist between normal and coronary patients. Caution is advised in comparing the timing of events during diastole because apparent group differences may be related in part to rest or exercise heart rate.

Adult↗
PubMed1983

The role of the pericardium in interactions between the cardiac chambers.

Distension of one side of the heart involves both the atrium and the ventricle, and such atrioventricular enlargement encroaches more on pericardial volume than would ventricular distension alone. The influence of distension of the entire right side of the heart on the pressure-volume relationship of the entire left heart was studied in six postmortem canine hearts with intact pericardium. The pressure-volume relation of the left heart was determined when the right heart was empty and when it was filled with saline. The pressure-volume curve of the left heart became steeper when the volume of the right heart was increased. However, after subtracting pericardial pressure from the left heart pressure, the pressure-volume curves were unaffected by increased volume of the right heart. Selective distension of the entire right heart has a considerable effect on the filling characteristics of the left heart when the pericardium is intact, although this is less than that observed in experiments in which the more compliant atria have been excluded. This effect becomes negligible after subtracting pericardial pressure.

Animals↗
PubMed1983

Influence of the pericardium on left ventricular diastolic pressure-volume curves in dogs with sustained volume overload.

The pericardium is largely responsible for displacement of the left ventricular diastolic pressure-volume curve observed after acute volume loading in dogs. Likewise the pericardium has been considered likely to play a role in displacement of the curve in patients with acute cardiac failure and in shifts following manipulation of afterload. This study was designed to examine the influence of the pericardium on the diastolic pressure-volume relation of the left ventricle when volume load is more sustained, a setting relevant to observations made in patients with heart failure. We measured left ventricular pressure and volume in six conscious dogs with sustained volume overload (mean left ventricular end-diastolic pressure 21 mm Hg, left ventricular end-diastolic volume 149% of the upper limit of normal for our laboratory) produced by aortocaval shunt created 7 to 29 days earlier. Simultaneous left ventriculograms and pressures were obtained before and during nitroprusside infusion with the pericardium intact and in four dogs the studies were repeated 7 to 15 days after pericardiectomy. In all six dogs with intact pericardium, nitroprusside displaced the entire pressure-volume curve downward whereas after pericardiectomy, the pressure-volume data points obtained before and during nitroprusside infusion fell on a single curve. These results were similar to those previously reported for acute volume overload. Nitroprusside did not alter the time course of left ventricular pressure fall during the isovolumic period of diastole either before pericardiectomy (28.8 +/- 10.2 sec,-1, 28.4 +/- 11.9 sec-1) or after (28.8 +/- 6.7 sec-1, 26.1 +/- 7.2 sec-1). These data indicate that in dogs subjected to volume overload sustained for periods of up to 29 days, the pericardium affects the left ventricular diastolic pressure-volume curve and contributes to the elevation of left ventricular filling pressure through upward displacement of this curve.

Animals↗
PubMed1983

Pulmonary circulation time: comparison of mean, median, peak, and onset (appearance) values using indocyanine green and first-transit radionuclide techniques.

To assess the difference between a variety of mathematical methods for assessing pulmonary transit time, we evaluated 11 acutely anesthetized and instrumented mongrel dogs at a control stage and then during infusions of isoproterenol or phenylephrine, or after the induction of ischemia. Green-dye optical density curves were obtained to evaluate a variety of pulmonary circulation times. Mean transit time, median time, peak time, and onset time all correlated well (r greater than or equal to 0.93), with the mean time being the longest, followed by the median time (4% less than the mean time, p less than 0.05), peak time (15% less than the mean time p less than 0.01), and onset or appearance time (49% less than the mean time, p less than 0.001). In the 34 available data points the mean time averaged 4.67 +/- 1.7 seconds, the median time averaged 4.47 +/- 1.74 seconds, the peak time averaged 3.98 +/- 1.7 seconds, and the onset time averaged 2.27 +/- 1.43 seconds. Similar results were obtained from the first-pass radionuclide angiograms from 17 adult male subjects. We conclude that median, peak, and onset times are reasonable though predictably shorter approximates of mean pulmonary transit time. They may be utilized during interventions (particularly when alternative counting methods are planned, as with radionuclide or possibly digital angiographic techniques) as guides to changes in the pulmonary circulation.

Animals↗
PubMed1983

Hemodynamic and electrocardiographic effects in man of a new nonionic contrast agent (iohexol): advantages over standard ionic agents.

Iohexol is a new, nonionic contrast material that has been shown in animal studies to hold great promise as an agent for coronary arteriography and ventriculography with fewer adverse hemodynamic effects than standard ionic media. At present, it has not been studied systematically in man. Fifty patients referred for elective cardiac catheterization were randomized to receive either iohexol or meglumine sodium diatrizoate (Renografin-76). Both operator and patient were blinded as to which agent was being used. Hemodynamic variables measured were pulmonary artery wedge pressure and systemic blood pressure. In addition, the following electrocardiographic indexes were evaluated: S-T segment shifts, changes in Q-T interval, changes in T-wave amplitude, and changes in heart rate. These variables were measured after left ventriculography and after both left and right coronary arteriography. Both iohexol and sodium meglumine diatrizoate produced small transient elevations in pulmonary artery wedge pressure. Systemic hypotension occurred with both agents but was more profound and longer-lasting with sodium meglumine diatrizoate. Iohexol injection resulted in no electrocardiographic changes, whereas sodium meglumine diatrizoate produced marked Q-T prolongation, as well as changes in T-wave amplitude and heart rate. Iohexol was well tolerated by the patients, and radiographic opacification was good to excellent in all cases. Thus, iohexol produces fewer deleterious hemodynamic and electrocardiographic changes than sodium meglumine diatrizoate when studied in a typical adult population requiring diagnostic cardiac catheterization. This favorable preliminary experience in man has potential widespread importance because of the large number of patients undergoing angiographic procedures.

Aged↗
PubMed1983

The accuracy of radionuclide ventriculography in the analysis of left ventricular ejection fraction.

To assess the reliability of using ejection fraction values derived from gated blood pools scans as a way to classify patients, we reviewed 76 radionuclide studies. Each study was processed in 10 different ways (varying or fixed left ventricular region of interest in association with 5 different backgrounds), and compared with contrast ventriculograms performed within one week of the radionuclide study. Correlation values with contrast results varied from 0.76 to 0.94 (mean 0.84 +/- 0.06, +/- 1 SD), and linear fit slopes varied from 0.39 to 0.90 (mean 0.75 +/- 0.15). Based on contrast results, patients were divided first into four groups (severely reduced, reduced, normal, and high ejection fractions). Predictive accuracy of the radionuclide estimates for these four groups was poor, ranging from 0.39 +/- 0.08 to 0.82 +/- 0.06%. Sensitivity was somewhat better (range 0.53 +/- 0.11 to 0.78 +/- 0.08%), and specificity better yet (0.78 +/- 0.08 to 0.95 +/- 0.02%). The results were better with techniques resulting in higher correlation values, and further improved when patients were regrouped into two populations (normal or reduced), though 90% of subjects were correctly identified only when correlation values exceeded 0.90. We conclude that care must be taken in the identification of patients using radionuclide angiography who have normal and abnormal left ventricular function; it can be done with confidence only when linear fits with contrast ventriculographic results have high correlation coefficients. Stratification attempts should be reduced to a minimum, as multiple population subgroups result in substantial patient mislabeling.

Adult↗
PubMed1983

Effect of exercise on QRS duration in healthy men: a computer ECG analysis.

Increased sympathetic tone with exercise enhances ventricular conduction and would be predicted to shorten QRS duration. Previous studies, however, have not consistently documented such changes. Using a digital electrocardiograph (ECG) cart sampling at 500 Hz, a bipolar precordial lead (V5-V2) was recorded (supine, at end expiration) in 25 healthy men (mean age 29 yr, range 19-37) at rest and immediately after submaximal treadmill exercise. QRS duration was measured on complexes recorded at high gain and expanded time scale. A significant (P less than 0.0005) decrease [4.9 +/- 2.3 (SD) ms] in QRS duration was noted, and decreased QRS duration was observed in all 25 subjects (range 1-10 ms). Furthermore there was significant (P less than 0.01) shortening of the intervals between QRS onset and Q-wave nadir (1.2 +/- 2.0 ms) and between QRS onset and R-wave peak (2.4 +/- 2.5 ms), as well as of the Q-R interval (1.3 +/- 2.7 ms). However, there were no significant differences in percent shortening of early vs. later phases of the QRS. To exclude digital sampling errors the same protocol was also applied in 11 healthy men by using an analog ECG cart. QRS duration immediately postexercise shortened by 7.1 +/- 4.3 ms (range 2-11.5 ms), which was not significantly different from the results obtained with the digital ECG. We conclude that decreased QRS duration is a physiological response to moderate treadmill exercise in healthy men, reflecting enhancement of conduction in early, middle, and later phases of ventricular activation.

Adult↗
PubMed1983

Computer analysis of exercise-induced changes in electrocardiographic variables. Comparison of methods and criteria.

In order to evaluate computerized methods of electrocardiographic signal processing, determination of QRS end, and measurement of criteria for ischemia, we analyzed the data from 42 male patients with coronary heart disease who underwent maximal treadmill testing. Electrocardiographic data were digitized on-line and leads X, V5, Y and Eigen V were later analyzed for noise content, isoelectric baseline, and ST parameters using the UCSD spatial electrocardiographic computer program. Various ST segment criteria for ischemia were calculated and compared. Noise was greater in lead Y and in all leads when the median was used for signal averaging. Two isoelectric baseline algorithms and three ST segment slope algorithms gave similar results. Spatially derived QRS end was highly correlated with the amplitude measured using a fixed time interval after peak R wave. Both ST area and ST midpoint estimates differed widely using two different algorithms for each. Regression equations were derived that make it possible to estimate QRS end or ST60 amplitudes in V5 from values in X or vice versa.

Adult↗