Atrial compliance determines the nature of passive atrial stretch and plasma atrial natriuretic factor in the conscious dog

Study objective — The aim was to measure changes in atrial wall function over a wide range of atrial filling pressures in order to determine the relationship governing the atrial stretch in vivo. Design — Acute graded haemorrhage, 30 ml·kg−1, was used to reduce atrial stretch, and volume loading with 1000 ml saline was used to increase atrial stretch. Experimental material — Awake mongrel dogs (n=6) were instrumented for the measurement of left atrial appendage pressure and diameter; awake mongrel dogs (n=4) were instrumented for measurement of left and right atrial appendage pressures and diameters. Measurements and main results — During haemorrhage, left atrial pressure and diameter decreased progressively, and plasma atrial natriuretic factor fell from 44 (SEM 10) to 25(5) pg·ml−1 (p