Assessment of Left Ventricular Performance in Man

Abstract

A three-dimensional construct of the tension-velocity-length relations of the intact human heart has been obtained in 17 patients by measurement of instantaneous ascending aortic flow velocity, left ventricular (LV) high-fidelity pressure, and end-diastolic volume. Left ventricular instantaneous volume was determined by subtracting the integral of the flow trace, obtained with an electromagnetic velocity catheter, at each 5-sec interval from the end-diastolic volume measured on a biplane left ventriculogram. By utilizing a thin-walled spherical model for the LV, instantaneous velocity of circumferential fiber shortening (V CF ), wall tension, and circumferential length were calculated and plotted with the aid of a computer on a three-dimensional perspective graph. The resulting tension-velocity-length relations in seven patients with normal LV function were clearly separated from those of 10 patients with abnormal LV function. Of velocity indices alone, peak V CF in circumferences/sec (circ/sec) provided the best statistical separation between the groups with normal and abnormal ventricular function (2.54 ± 0.18 [ sem ] circ/sec and 1.09 ± 0.15 circ/sec, respectively) ( P < 0.001). The time to peak V CF averaged 194 ± 13.2 msec and 167 ± 9.3 msec in the patients with normal and abnormal ventricular function, respectively ( P > 0.05). Likewise, V CF at peak tension was significantly greater in the patients with normal as opposed to abnormal LV function (1.77 ± 0.10 and 0.93 ± 0.15 circ/sec, respectively) ( P < 0.001). Time to peak tension was 138 ± 14.8 msec and 182 ± 17.1 msec in the normal and abnormal patients, respectively ( P > 0.05). Mean V CF also served to separate the two groups, averaging 1.35 ± 0.07 and 0.72 ± 0.10 circ/sec in the patients with normal and abnormal ventricular performance, respectively ( P < 0.001). Peak wall tension did not differ significantly between the two patient groups, averaging 231.4 ± 15.7 and 273.3 ± 16.4 g/cm in the patients with normal and abnormal ventricular function, respectively. Peak instantaneous power was higher in the normal compared to the abnormal group, averaging 8.39 ± 0.83 and 5.91 ± 0.60 kg-cm/sec per cm of circumference, respectively ( P < 0.05). It is concluded that a three-dimensional construct of left ventricular circumferential velocity, tension, and length during ejection is readily obtainable during diagnostic cardiac catheterization and provides a sensitive and comprehensive description of LV myocardial function in man.