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Descriptive analysis of instantaneous left atrial volume—with special reference to left atrial function

1981; Elsevier BV; Volume: 30; Issue: 2 Linguagem: Inglês

10.1016/0022-4804(81)90002-0

1095-8673

David C. Hitch, Stanton P. Nolan,

Cardiac Arrhythmias and Treatments

Instantaneous left atrial volume was determined in five calves by electrical integration of left atrial differential flow (pulmonary vein flow less mitral valve flow). Volume changes were classified and compared to previously described mitral valve flow phases. With the onset of left ventricular isovolumic contraction, the left atrium began to fill. There was an initial rapid filling period, followed by a slower but steady increase in volume. With reversal of the atrioventricular gradient, there was an initial decrease in left atrial volume. This decrease then reached a plateau, during which the left atrium remained isovolumic. With atrial contraction there was a further decrease in left atrial volume. Left atrial function (reservoir, pump, or conduit) was evaluated using an algorithm to emphasize major changes. Reservoir function occurred mainly during ventricular systole, but was also seen during diastole. Pump function occurred only during ventricular diastole and could be further divided into passive and active components. The passive component contributed the majority of blood transfer from the atrium into the ventricle. Active atrial contraction provided only 13% of the stroke volume but under the conditions of normal sinus rhythms occurred at the most sensitive point of ventricular filling. Conduit function was seen during ventricular diastole, was inversely related to the reservoir and pump functions, and thus produced a rate of ventricular filling smoother than expected and permitted a maximal transfer of blood from the left atrium into the ventricle.