Biomedical subjects
Publications and source records attributed to R G Pai.
Effect of isolated left atrial enlargement on mitral annular size and valve competence was evaluated in 62 patients with normal left ventricular size and function and intrinsically normal mitral leaflets. Echocardiographic data showed that isolated left atrial enlargement could cause enlargement of the mitral annulus and cause mitral regurgitation.
Left ventricular (LV) diastolic dysfunction is an important cause of heart failure, and recent advances in the application of Doppler techniques allow a semiquantitative assessment of LV diastolic performance. This review discusses the use of Doppler echocardiography in the comprehensive assessment of LV diastolic function and performance in terms of the normal mitral and pulmonary venous flow profiles, their physiologic basis, and alterations in diseased states. There is also a discussion on the newer aspects of mitral flows such as relative durations of mitral A and pulmonary vein AR waves, E- and A- wave propagation inside the LV with their hemodynamic correlates, and derivation of ventricular dP/dt and Tau from the mitral regurgitation velocity profile. Analysis of these flow profiles and the other Doppler measures alluded to above allow one to make a fairly precise hemodynamic assessment of a patient in terms of left atrial pressure, LV relaxation and stiffness and the profile of LV diastolic pressure in terms of pre- 'a' wave and 'a' wave pressures and ventricular end-diastolic pressure.
Constrictive pericarditis is a fibrotic process involving both layers of the pericardium and is known to give rise to obstruction to blood flow in the right heart. We report a patient with constrictive pericarditis who had echocardiographic features of mitral stenosis caused by a fibrocalcific mass lesion involving the mitral annulus with infiltration into the base of the posterior mitral leaflet. To our knowledge, this has not been reported in the literature.
We report the anatomic and hemodynamic details of severe stenosis of a bioprosthetic tricuspid valve studied by transthoracic and transesophageal echocardiography. This patient also had antegrade systolic flow across the tricuspid valve due to a combination of severe tricuspid valve stenosis and poor right ventricular systolic function.
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Fifty-nine consecutive patients with angiographically documented coronary artery disease were prospectively studied during dobutamine stress echocardiography. Twelve patients (20%) developed hypotension, defined as a decrease in systolic blood pressure of > or = 20 mm Hg compared with baseline. The transmitral flow velocities, isovolumic relaxation time (IVRT), and flow in the left ventricular (LV) outflow tract were measured at baseline, at maximal dobutamine dose, or during a hypotensive episode; stroke volume, cardiac output, and systemic vascular resistance (SVR) were computed. Correlates of hypotensive response to dobutamine stress echocardiography included therapy with angiotensin-converting enzyme inhibitors (p = 0.032), a longer IVRT at baseline (121 +/- 25 vs 103 +/- 28 ms, p = 0.047), a greater decrease in LV end-diastolic (-6.0 +/- 3.1 vs -2.2 +/- 2.1 mm, p < 0.0001) and end-systolic (-8.3 +/- 7.0 vs -5.1 +/- 3.7 mm, p = 0.037) dimensions, and a greater decrease in stroke volume (-10 +/- 10 vs -2 +/- 11 ml, p = 0.023) compared with those with a normal response. The groups did not differ significantly with regard to baseline stroke volume, cardiac output, SVR, and LV ejection fraction or LV mass.(ABSTRACT TRUNCATED AT 250 WORDS)
Infusion of dobutamine in low and high doses in combination with echocardiography can be used for the assessment of myocardial viability and functional significance of coronary artery disease. Improvement of contractile function of hypokinetic or akinetic ventricular wall segment with low-dose dobutamine has a high predictive value for the detection of hibernating and stunned myocardium. High-dose dobutamine stress is of value for noninvasive diagnosis of coronary disease, assessment of its clinical significance, risk stratification of patients after myocardial infarction, preoperative evaluation of patients undergoing major noncardiac surgery, and assessment of the efficacy of coronary revascularization. It has an excellent safety record even in the immediate postmyocardial infarction period.
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Mitral annulus anatomy and dynamics were evaluated in 12 subjects using a three-dimensional transesophageal echocardiographic technique. The mitral annular area, diameters and distance from the left ventricular apex were measured in end-diastole, mid-systole, end-systole and mid-diastole. The mitral annulus had its largest area in end-systole and the smallest area in end-diastole. The shape of the annulus changed during the cardiac cycle with the maximal change occurring in the diameters passing close to the middle of the mitral leaflets. In the vertical plane, the annulus had a shallow ski-slope shape, with the attachment of the anterior leaflet being farthest from the apex. In other words, the highest point of the annulus was situated anteromedially and was visualized in the long axis imaging plane.
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This clinical study was undertaken to investigate the effect of respiration on the QT interval. The QT interval is affected by a variety of factors, including steady changes in heart rate, instantaneous changes in heart rate as in atrial fibrillation, and changes in autonomic tone. Respiration gives rise to cyclical changes in the instantaneous heart rate and autonomic tone. The effect of respiration on the QT interval was analyzed in 25 subjects in sinus rhythm. Cosinor analysis was used to estimate the amplitude of its change from the mean value, its statistical significance, and the timing of the maximum change. Thirteen (52%) subjects revealed significant respiratory change in the QT interval, being the shortest during inspiration in 10 of them. Its amplitude correlated positively with respiratory cycle length (r = .58, P < .01), but not with age, mean heart rate, or the amplitude of change in the RR interval. The mean amplitude of change in the QT interval was 0.8% compared to a change of 2.6% in the RR interval. There is a respiratory variation in the QT interval in subjects in sinus rhythm that is more prominent during slower respirations. However, the amplitude of change in the QT interval is small compared to the change in the RR interval.
BACKGROUND: Subjects in sinus rhythm have two distinct diastolic flow velocities in the left ventricular (LV) outflow tract directed toward the aortic valve. These follow E and A waves of the transmitral flow and are referred to as Er and Ar waves, respectively. The A wave transit time from the mitral valve to the LV outflow tract is shorter than that of the E wave and is shorter in those with LV hypertrophy and the aged, suggesting its possible dependence on LV late diastolic stiffness. METHODS AND RESULTS. We measured the peak-to-peak and onset-to-onset A wave transit times from the mitral valve to the LV outflow tract (AArp and AAro intervals, respectively) using Doppler echocardiography in 20 patients undergoing left heart catheterization for evaluation of coronary artery disease. These intervals were correlated with indices of LV late diastolic stiffness obtained from high-fidelity LV pressure tracings and angiographic volume assessments. The AArp and AAro intervals correlated significantly with LV Dp/DV (conventionally dP/dV) (r = -.68 and -.83, respectively), volume stiffness, V.Dp/DV (r = -.74 and -.80, respectively) and LV (V/P) (Dp/DV) (r = -.69 and -.74, respectively). The AAro interval correlated better with the square roots of LV Dp/DV and volume stiffness (r = -.86 and -.87, respectively). CONCLUSIONS: We conclude that AArp and AAro intervals are easily obtainable Doppler parameters that reflect LV late diastolic stiffness in patients with coronary artery disease and possibly in other patients groups.
Tricuspid regurgitation (TR) is common and the rate of right ventricular (RV) pressure rise in early systole can be obtained from the TR velocity profile. Right ventricular function has important implications in patients with valvular heart disease. Fifty five patients with mild or moderate TR and a wide range of pulmonary artery (PA) pressures were studied. The RV dP/dt was obtained as the ratio of the calculated rise in RV pressure from 0.5 m/s to 1.5 m/s of the TR velocity signal (8 mmHg based on simplified Bernoulli equation) to the time taken for this change. The RV dP/dt correlated positively with PA systolic pressure (r = 0.73, p < 0.001), tricuspid anular plane systolic excursion which is an echocardiographic index of RV ejection systolic function (r = 0.45, p < 0.001) and left ventricular (LV) fractional shortening (r = 0.40, p < 0.01). Multivariate analysis showed that all these three parameters independently influenced RV dP/dt (multivariate R = 0.83) accounting for 69% of its variability. In conclusion, it is suggested that right ventricular dP/dt is easily obtainable from Doppler TR velocity signal. It is influenced independently in a positive manner by PA systolic pressure and RV and LV systolic function. Despite its predominant dependence on PA systolic pressure, it may give useful insight into RV systolic function for a given level of PA pressure. It may also be useful for longitudinal follow up of the RV function in patients with heart disease.
UNLABELLED: Recent reports have emphasized the limitations of aortic valve area estimations using the Gorlin formula based on the Toricelli model. Since aortic valve resistance (AVR) does not use a constant and treats the pressure gradient and the cardiac output without favouring either, it has been proposed as a more accurate index of the severity of aortic stenosis. Though it has previously been calculated using pressure and flow parameters obtained in the catheterization laboratory, it is possible to derive the valve resistance using Doppler echocardiography. Doppler-echo estimates of AVR may be used as an alternative index of aortic stenosis severity; however, no data exists as to its accuracy compared with cardiac catheterization derived AVR. Thirty-nine patients with aortic stenosis undergoing invasive hemodynamic and Doppler-echo evaluations were studied. The AVR was calculated using the formula: (mean pressure gradient)/(flow per systolic ejection period). The cardiac output at catheterization was measured by using thermodilution technique, whilst the Doppler-echo method utilized the product of velocity time integral of the flow in left ventricular outflow tract and its cross sectional area. The Doppler-echo derived AVR (38.5 to 738.2 dyne.sec.cm-5) correlated significantly (r = 0.82, p < 0.0001, S.E.E. = 75.0 dyne.sec.cm-5) with independently derived catheterization values (53.6 to 738.8 dyne.sec.cm-5). There was a good correlation between mean gradient obtained by both modalities. CONCLUSION: Doppler-echo AVR correlates well with catheterization AVR and may provide an additional non-invasive parameter of aortic stenosis severity.
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