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R G Pai

Publications and source records attributed to R G Pai.

46 records · Page 3Linked to original sources
PubMed1993

A new Doppler method for assessing left ventricular diastolic stiffness based on principles of flow wave propagation: mathematical basis and review of the method.

Color flow imaging shows that the transmitral flow is initially directed to the left ventricular (LV) apex and then turns around facing the aortic valve. A pulsed wave Doppler sample placed in the LV outflow tract (LVOT) records two peaks of diastolic flow waves, Er and Ar waves, which follow E and A waves of the transmitral flow respectively. The Er and Ar waves represent transmitted E and A flow waves to the LVOT. Our preliminary clinical and hemodynamic data in human subjects have shown that the A-Ar interval, which is the time taken for the A velocity wave to propagate from the mitral valve to the LVOT, is shorter in those with LV hypertrophy (LVH), the aged and those with elevated LV late diastolic stiffness, suggesting faster A wave transmission in those with stiffer ventricles. We also have shown that velocity and pressure waves propagate similarly in the arterial system. This led to the hypothesis that the A wave transmission inside the LV may follow the principles described in the Moens-Korteweg equation, or a modification of it, and the velocity of A wave transmission inside the LV may reflect its late diastolic stiffness. Studies designed to test this hypothesis in a pulsatile LV model showed a linear relationship between the rate of diastolic flow wave propagation inside the LV and its stiffness. These preliminary data suggest that the velocity of A wave transmission inside the LV reflects LV late diastolic stiffness non-invasively. It is expected to be independent of a direct effect of heart rate and of preload.

Blood Flow Velocity↗
PubMed1992

Diastolic heart failure.

Diastolic heart failure is a distinct clinical entity increasingly seen in older patients and requires special awareness to make the diagnosis. Although no single laboratory test is identified for making a confident diagnosis of diastolic dysfunction as the pathogenetic mechanism for heart failure, a constellation of echocardiographic and radionuclear findings are helpful in most cases. Invasive assessment of LV diastole is laborious, requiring high-fidelity pressures and accurate measures of volumes, and these are rarely needed to diagnose the condition. It appears that prognosis is significantly better for those with normal systolic function, when compared with congestive heart failure caused by impaired systolic pump function. Finally, the therapeutic approaches are substantially different for the two groups. It must be emphasized that even patients with predominant myocardial systolic dysfunction have some combined diastolic dysfunction as well. This latter group is difficult to treat. However, improvement in systolic pump function, when markedly impaired, must take precedence in management strategies.

Diastole↗
PubMed1990

Doppler-derived rate of left ventricular pressure rise. Its correlation with the postoperative left ventricular function in mitral regurgitation.

A new Doppler-derived index of the rate of left ventricular (LV) pressure rise (delta P/delta t) was evaluated for the prognostic stratification of patients with chronic mitral regurgitation. The index is derived from the continuous wave Doppler mitral regurgitation signal by dividing magnitude of LV-left atrial pressure gradient rise (delta p) between 1 and 3 m/sec of the mitral regurgitation velocity signal by the time taken (delta t) for this change. We studied the LV delta P/delta t and other echocardiographic indexes of LV function before and after mitral valve surgery in 25 patients with chronic, severe mitral regurgitation in the absence of significant coronary artery disease. There was a good correlation between postoperative ejection fraction (EF) and the derived LV delta P/delta t (r = 0.75, p less than 0.001). The other echocardiographic parameters that correlated with postoperative EF were LV end-systolic dimension (r = -0.7, p less than 0.001), end-systolic volume (r = -0.69, p less than 0.001), end-diastolic dimension (r = -0.58, p less than 0.01), end-diastolic volume (r = -0.57, p less than 0.01), preoperative EF (r = 0.69, p less than 0.001), end-systolic wall stress (r = -0.61, p less than 0.01), and end-systolic wall stress normalized for end-systolic volume index (r = -0.45, p less than 0.05). With multiple regression, the LV delta P/delta t and LV end-systolic dimension (ESD) were shown to be independent predictors of postoperative EF. The postoperative EF could defined by the equation: 43 + 0.8 square root delta P/delta t--0.53 ESD (mm) (r = 0.86).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Normal changes in left ventricular filling and hemodynamics during dobutamine stress echocardiography.

During high-dose dobutamine infusion, there is a dose-dependent increase in cardiac output, a reduction in systemic vascular resistance, a reduction in left ventricular size, an increase in the mitral A wave velocity, a reduction in the E/A velocity ratio, and a reduction in the isovolumic relaxation time, with little change in the rate-corrected isovolumic relaxation time. Left ventricular cavity obliteration is common. This information may be useful in defining the mechanism of hypotension commonly seen during dobutamine stress echocardiography. It is speculated that the diastolic behavior of the left ventricle during dobutamine stress echocardiography, especially the isovolumic relaxation time, may provide an additional indicator of early myocardial ischemia, but this needs to be confirmed by larger independent studies.

Adrenergic beta-Agonists↗
PubMedDate not supplied

A case of mitral-aortic intervalvular fibrosa aneurysm with unique flow patterns and long-term natural survival.

We report a patient with a large aneurysm of mitral-aortic intervalvular fibrosa as a complication of prosthetic aortic valve endocarditis diagnosed on transthoracic echocardiography. This aneurysm began to expand with atrial systole, filled fully during ventricular systole, and collapsed in diastole on transesophageal examination. The patient refused corrective surgery and has survived on medical treatment for close to 2 years.

Adult↗
PubMedDate not supplied

A rare case of inferior venacaval type of atrial septal defect in an adult: echocardiographic features.

We report a rare type of atrial septal defect with communication between the left atrium and the inferior vena cava. This type of defect has been referred to as a low sinus venous type of atrial septal defect because of its developmental origin, and possibly is caused by defective absorption of the left venous valve of the sinus venosus into the septum secundum. Detailed echocardiographic features are discussed.

Aged↗