Determinants of left ventricular filling and of the diastolic pressure-volume relation.

Until the 1970s, the left ventricle was considered an isolated shell in which the left ventricular diastolic pressure-volume relation depended on the myocardium's material properties and the left ventricle's wall thickness and geometry. According to this view, the relation between diastolic pressure and volume could change only in response to chronic changes in the cardiac muscle's material properties, such as scarring due to infarction, or changes in cardiac geometry due to hypertrophy. As a consequence, the diastolic pressure-volume relation was considered unique over the short term. A practical application of this assumed uniqueness was that left ventricular diastolic pressure was used as a surrogate for volume in evaluating systolic function. However, in the early 1970s, studies of patients with coronary artery disease contradicted this simplistic view of the diastolic pressure-volume relation.In these patients, the left ventricular diastolic pressure-volume curve shifted upward temporarily immediately after cardiac pacing-induced angina and then returned to prepacing values. Later, other investigatorsobserved that vasodilator and vasoconstrictor drugs, which change the vascular loading conditions of the left ventricle, also produced acute reversible shifts in the left ventricular diastolic pressure-volume curve. In the process of explaining these clinical observations, we have learned that many factors can affect left ventricular filling and the diastolic pressure-volume relation acutely. The original concept that the pressure within the left ventricle is determined by the balance between the forces due to pressures within the ventricular cavity that expand the ventricle and forces due to elasticity of the myocardium that resist this expan-