Contribution of Atrial Reservoir Function to Ventricular Filling in Hypertensive Patients

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Abstract
We designed this study to assess the importance of left atrial function as a contributor to mitral flow velocity pattern in hypertensive patients. In hypertensive patients the early diastolic flow velocity and ratio of early to late diastolic flow velocity in the mitral flow velocity pattern increase in association with sublingual administration of nifedipine. These changes have been interpreted as signs of improved left ventricular diastolic function; however, the mitral flow velocity pattern is also affected by various other factors. Thus, the nifedipine-induced changes may not necessarily indicate the improvement of left ventricular diastolic function. Transthoracic Doppler echocardiographic parameters of mitral and pulmonary venous flow velocity patterns and left ventricular M-mode echograms were obtained in 16 untreated hypertensive patients before and after sublingual administration of nifedipine (10 mg). Normal values of the parameters were determined in 50 age-matched healthy subjects. After nifedipine peak early diastolic mitral flow velocity increased beyond the normal value, although the peak increasing rate of left ventricular inner dimension, another index of left ventricular diastolic function, did not recover to the normal value. Peak systolic velocity in the pulmonary venous flow velocity pattern increased beyond the normal value, indicating improvement of the reservoir function of the left atrium during systole. Nifedipine-induced normalization of the mitral flow velocity pattern was associated with further abnormalities of the pulmonary venous flow velocity pattern, indicating enhanced left atrial reservoir function. Thus, nifedipine-induced normalization of the mitral flow velocity pattern should be explained not only by the normalization of left ventricular diastolic function but also by another adaptive alteration in left atrial reservoir function in hypertensive patients. Combined analysis of mitral and pulmonary venous flow velocity patterns may be useful in avoiding the misinterpretation of the mitral flow velocity pattern.

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