Comparison of left atrial pressure and wedge pulmonary capillary pressure. Pressure gradients between left atrium and left ventricle.

Simultaneous records of wedged pulmonary capillary pressure and left atrial pressure have been made in I2 patients. The pressure changes in the left atrium preceded those in the pulmonary capillary bed by o-o6 to O0I4 sec. This delay, together with the damping of the wedged pulmonary capillary pressure, may result in a false appearance of an end-diastolic gradient between the left atrium and the left ventricle if simultaneous wedged pulmonary capillary pressure and left ventricular tracings are compared. In severe aortic valve incompetence the reflux of blood into the left ventricle from the aorta during ventricular diastole may be so profuse that the pressures in the left ventricle and aorta equalize before the end of diastole. In these circumstances the end-diastolic ventricular pressure may exceed the left atrial pressure, so that the mitral valve is prematurely closed by the rise in ventricular pressure (Wright, Toscano-Barboza, and Brandenburg, I956; Colvez et al., I959). In some cases this premature closure is preceded by regurgitation of blood into the left atrium shown by left ventricular angiocardio-graphy. This phenomenon is likely to account for some, if not all, cases of Austin Flint murmur (Wigle and Labrosse, I965; Lochaya, Igarashi, and Shaffer, I967). Premature mitral valve closure may also be seen in lesser degrees of aortic incompetence where the aortic and ventricular end-diastolic pressures have not equalized, either as a result of a change in the atrio-ventricular rhythm (Colvez et al., I959), or because the end-diastolic pressure, while not reaching aortic diastolic levels, exceeds the atrial pressure (Wigle and Labrosse, I965). A similar phenomenon has been shown in dogs (Welch, Braunwald, and Sarnoff, I957). Since the occurrence of premature mitral valve closure may be regarded as evidence of a significant milestone in the decline of Received 3 June I969. left heart function in aortic incompetence, measurements of left atrial and ventricular pressure are of considerable importance. Most of the studies discussed above were made by direct pressure measurements from the left atrium, left ventricle, and aorta. In man, this involves a difficult catheterization technique in patients whose clinical condition may be poor. The recording of wedged pulmonary capillary pressure provides a much safer way of assessing the left atrial pressure, and, indirectly, the ventricular end-diastolic gradient. Both Oliver, Gazetopoulos, and Deuchar (I967) and Lochaya et al. (I967) have shown reversed gradients across the mitral valve by this technique in patients with aortic regurgitation. Transseptal left …