The clinical value of the calibrated apical A wave and its relationship to the fourth heart sound.

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Abstract
The amplitude of the calibrated apical A wave (A), its 1st derivative (dA/dt), its normalized 1st derivative ([dA/dt]/A) and its value expressed as a percentage of the total systolic deflection (A/H) were derived from calibrated left apexcardiograms in 64 normal subjects and in 150 patients with heart disease. A is significantly increased in patients with pressure and volume overload of the left ventricle, in idiopathic hypertrophic subaortic stenosis, in congestive cardiomyopathy and in ischemic heart disease in the presence of left ventricular asynergy (P < 0.001). In aortic stenosis, A is more sensitive to changes in left ventricular compliance than the A/H ratio. Highly significant correlations exist between A and peak dA/dt in normals (r [correlation coefficient] = 0.98) and in patients with heart disease (r = 0.81-0.99); at an identical A, patients with a dilated left ventricle have lower values for peak dA/dt and a lower index (peak dA/dt)/A (P < 0.001). As a result, A and peak dA/dt are primarily determined by the resistance to ventricular filling during atrial systole. In the presence of a 4th heart sound (S4), A and peak dA/dt were significantly increased (P < 0.001). A peak dA/dt value > 6X/s is always associated with an S4. To a certain degree peak dA/dt can differentiate between a physiologic and pathologic S4. The intensity of S4 depends more on the rate of rise of the A wave than on its total amplitude.

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