[Problems of angiographic determination of diastolic pressure-volume relationship of the left ventricle (author's transl)].

The problems of determination of the left ventricular diastolic pressure-volume relationship were demonstrated by analysis of post-extrasystolic beats and of two consecutive normal beats. Quantitative high-speed left ventriculography with simultaneous pressure recording was performed in 16 patients with reduced left ventricular function. The diastolic pressure-volume relationship was evaluated using the formula of Diamond and Forrester (p = b . e(a) V + c) (formula [1]) and a simplified expression (p = b' . e(a') . V) (formula [2]), usually used. The parameters b, a and c of formula (1) showed significant but nonuniform alterations. The parameters b' and a' of formula (2) did not change significantly. The residual sums of squares of the approximation using formula (1) were about 8% less than those of formula (2); i.e.: the measured left ventricular pressures and volumes could be fitted more exactly by formula (1). Two pressure-volume-curves with identical slopes but different operating pressure-levels could not be described by formula (2), because in this case the computed slope of the pressure-volume curve was influenced by shifts of the operating pressure-level. The results show that the diastolic pressure-volume relationship cannot exactly be described by formula (2). The application of formula (1) proved the angiographic determination of left ventricular volumes to be insufficient for the evaluation of the diastolic pressure-volume relationship.