Search PubMed⌕ Search

Biomedical subjects

V Bhargava

Publications and source records attributed to V Bhargava.

At least 127 records · Page 7Linked to original sources
PubMed1982

A computerized approach to evaluating rest and exercise-induced ECG/VCG changes after cardiac rehabilitation.

A computerized method of acquiring and analyzing rest and exercise test 12-lead electrocardiographic and three-dimensional lead vectorcardiographic data before and after cardiac rehabilitations is described. Fourteen coronary heart disease patients were exercise tested before and after a mean of five months of aerobic exercise training, The only significant ST-segment improvements were found in three-dimensional space. Spatial measurements should be considered in the assessment of electrocardiographic changes secondary to exercise training.

Adult↗
PubMed1982

Left ventricular emptying dynamics in patients with asymmetric septal hypertrophy and concentric hypertrophic cardiomyopathy.

We studied the dynamics of left ventricular (LV) emptying in 8 patients with asymmetric septal hypertrophy (ASH), 6 patients with concentric hypertrophic cardiomyopathy (CHC), and 6 normal controls. Four patients with ASH had resting systolic gradients greater than 20 mmHg, all had significant post premature ventricular contraction (PVC) systolic pressure gradients. LV volume (V) was obtained by frame-by-frame analysis of cineangiograms. End-diastolic volume was similar for all groups; end-systolic volume was significantly less in ASH and CHC patients than in normals. Maximum dV/dt was similar in ASH and CHC, and significantly greater than normals. Total systolic contraction time (SCT), i.e., time from peak volume to last cine frame at minimum volume, was similar for all groups, but the time required to eject 90% of stroke volume (90%T), as a fraction of SCT, was shorter for ASH (0.52 +/- 0.07) and CHC patients (0.51 +/- 0.05) than normals (0.67 +/- 0.07) (p less than 0.05 vs myopathy groups). In the sinus beat following a PVC, however, this ratio decreased significantly in normals and CHC patients, but did not change in ASH patients. We conclude that ASH and CHC have similar exaggerated systolic LV ejection dynamics in the basal state; the failure of ASH patients with post-PVC systolic outflow gradient to reduce 90% T/SCT post PVC may reflect obstruction to LV emptying.

Cardiac Output↗
PubMed1982

A method for measuring mean circumferential fiber shortening rate from gated blood pool scans.

Ejection fraction and ejection rate are easily obtained from gated cardiac images, but no method is available for calculating mean circumferential fiber shortening rate. We assumed that the cube root of left ventricular end-diastolic volume or counts is proportional to the minor axis of the left ventricle at end-diastole or end-systole. Mean circumferential fiber shortening rate is then equal to the [cube root of the end-diastolic volume (count) minus cube root of end-systolic volume (count)] divided by [cube root of end-diastolic volume (count) multiplied by the ejection time]. In 250 contrast ventriculograms, the standard mean circumferential fiber shortening rate (MCFSR) and that derived by the cube root method correlated well (r = 0.94). The mean value of MCFSR (0.85 +/- 0.35) was greater than the cube root value (0.75 +/- 0.35) (P less than 0.001). The regression equation was y = 0.86x + 0.02. Similar correlations were obtained from gated radionuclide images using a semiautomated program (r = 0.93) in 24 subjects or completely automated program (r = 0.85) in 28 patients. The regression equation between MCFSR and that derived from the cube root of counts for the semiautomated program was y = 0.82x + 0.04 and for the automated program was y = 0.84x + 0.004. Similar correlations, slopes, and intercepts were seen using circumferential fractional shortening for angiographic data when correlated with both the semiautomated and automated gated blood pool scan programs. These data indicate that MCFSR and circumferential fractional shortening may be obtained from gated blood pool images using cube root estimates of end-diastolic and end-systolic radii with a high degree of correlation with the standard contrast ventriculographic technique.

Adult↗
PubMed1982

Comparison of single-plane and biplane contrast analyses of right ventricular function and size.

To evaluate the utility of single and biplane right ventricular (RV) contrast angiograms, we evaluated 25 canine RV casts and 31 cineangiograms performed in patients during standard contrast ventriculograms. Both standard single and biplane formulae were utilized. In the 25 canine RVs, absolute volume was determined by water displacement. Both biplane (r = 0.96) and single-plane (r = 0.86) volumes correlated well with cast data. These formulae were then applied to contrast ventriculograms in the 31 patients (30-degree right anterior oblique and 60-degree left anterior oblique projections). The ejection fractions (EFs) calculated from the single-plane technique provided fair correlation with EFs derived from the biplane data (r = 0.81, y = 0.81X + 0.05). Similar correlations were noted when end-diastolic volume results were compared (r - 0.78, y - 0.57X + 56.4). However, while single-plane contrast right ventriculograms correlate with estimates of global RV function and size by biplane methods, considerable scatter of the data may limit its application in individual cases.

Aged↗
PubMed1982

Clinical assessment and follow-up of functional capacity in patients with chronic congestive cardiomyopathy.

The presumption that the results of left ventricular systolic function tests performed at rest are related to the symptoms of chronic congestive heart failure or to exercise capacity is unproved. Thirty-three patients with chronic congestive cardiomyopathy underwent serial exercise tests, determinations of ejection fraction and systolic time intervals, echocardiograms, assessment of symptom score, chest roentgenogram, and physical examination over a mean ( +/- standard deviation) of 24.8 +/- 14.1 months. Maximal exercise performance achieved correlation with symptoms (r = 0.66) but not with indexes of left ventricular function. Edema, elevated jugular venous pressure, rales and radiologic evidence of pulmonary venous hypertension were more common in patients with severe limitation of exercise capacity. in 17 patients whose functional capacity changed during the follow-up period, congruent changes in left ventricular function measured at rest were not consistently observed. Thus the findings on history, physical examination and radiologic examination correlate with exercise capacity, but indexes of left ventricular performance at rest do not and therefore are of limited use in assessing treatment. The clinical course of patients with chronic congestive cardiomyopathy can be followed up safely, effectively and economically by simple clinical observations. Serial laboratory testing of left ventricular function can be reserved for specific indications, research and patients with valvular heart disease.

Adult↗
PubMed1982

Pacemaker spike alternans: an artifact of digital signal processing.

Marked variability in the amplitude or polarity of pacemaker artifacts may be a clue to generator malfunction or partial electrode fracture. We report a case where "pacemaker spike alternans" occurred factitiously as a result of a digital "roll-over" effect. The widespread introduction of digital electrocardiographs into clinical practice makes recognition of such artifacts important.

Aged↗
PubMed1982

New method for measuring QRS duration using high-frequency electrocardiography.

Definition of QRS onset and offset is a basic problem in electrocardiography. Current techniques rely either on subjective estimates or on computer algorithms using QRS derivative or spatial vector velocity parameters. We developed a spectral method based on the observation that the QRS complex, unlike the P wave, PR segment, or ST-T complex is comprised of significant frequencies greater than 50 Hz. Accordingly, we adapted a microprocessor-based electrocardiograph (ECG) system with a signal-averaging program to reduce noise and a 50-300 Hz digital filter. Leads I and aVF were simultaneously acquired by computer in 40 subjects with a wide range of QRS duration (55.5-161 ms). Excellent correlation (r = 0.98) was noted between high-frequency QRS duration measurement and careful visual determinations made at high gain and expanded time scale. The high-frequency ECG appears to provide an objective physiological definition of the QRS complex based on spectral content not on morphology or slope.

Adolescent↗
PubMed1982

Effect of exercise in healthy men on QRS power spectrum.

The effect of exercise on the QRS power spectrum has not been evaluated. We hypothesized that increased conduction velocity with exercise might selectively increase high-frequency QRS potentials. Using a digital electrocardiograph (ECG) cart, a single bipolar chest lead was recorded in 21 healthy adult males at rest and then immediately after treadmill exercise. Fast Fourier transform analysis of the ECGs was performed using a 128-ms sampling window, including the QRS but not the P wave. Step discontinuities between PR and ST segments were minimized using a linear correction function to obviate artifactual increases in high-frequency content after exercise. The power spectrum plots of rest and exercise data showed an increase in the amplitude of high frequencies that could not be accounted for on the basis of noise contamination. For the frequency band between 187.5 and 250 Hz, the root-mean-square (RSM) voltage of exercise QRS complexes (10.0 +/- 3.6 micro V) was significantly (P less than 0.02) greater than that of rest QRS complexes (7.8 +/- 1.2). However, base-line noise level (computed over a 32-ms interval during the ST segment) was not different between rest and exercise over this high-frequency band. The same exercise protocol was also applied in 11 normal male subjects using an analog ECG cart. For the 187.5- to 250-Hz band, the RMS voltage of the QRS after exercise (13.0 +/- 1.8 micro V) was also significantly (P less than 0.01) greater than at rest (10.2 +/- 2.8) without any difference in ST segment noise level over the same frequency range. These data indicate that exercise causes an increase in the amplitude of high-frequency QRS potentials in healthy men.

Adult↗
PubMed1981

Progress in computer analysis of the exercise electrocardiogram.

The potential advantages of digital computer processing of exercise electrocardiographic data include reduction of noise, compression of data, improved precision and application of optimal criteria. Most prior approaches to such processing required equipment that was both expensive and inconvenient. With the revolution in instrumentation brought about by the development of microcomputers, powerful dedicated computers can now be afforded by many exercise laboratories. There are many approaches to computerized management of exercise electrocardiographic data and various criteria for ischemia. Studies are necessary to validate computer algorithms so that these devices can be used diagnostically to best advantage. Cardiologists need some understanding of this field so that they can be discriminating users of computer systems. In addition, the results of studies correlating electrocardiographic changes with radionuclide methods of assessing myocardial perfusion and function should enable such assessments to be made from the electrocardiographic signals alone, particularly when aided by computer analysis of spatial shifts.

Angina Pectoris↗
PubMed1981

Role of serotonin in the nicotine-induced depression of the brainstem auditory evoked response.

We have examined the role of serotonergic and/or dopaminergic mechanism in the mediation of the nicotine-induced depression of brainstem auditory evoked responses (BAER) to auditory stimuli. Nicotine produced dose- and time-dependent decreases in BAER amplitude. Administration of serotonin-depleting drugs (reserpine or p-chlorophenylalanine (PCPA), prevented this decrease. Administration of catecholamine-depleting drugs (alpha-methyl-p-tyrosine, disulfiram or Dopa), on the other hand, had no effect. These data thus suggest a role for serotonergic mechanisms in the mediation of nicotine-induced depression of the brainstem auditory pathway.

Animals↗