This investigation was designed to determine whether left ventricular (LV) maximum time-varying elastance (E(max)) calculations obtained using equilibrium radionuclide angiography (RNA) were comparable to those obtained using biplane contrast cineangiography (CINE), and whether simple, indirect P-V relations might provide reasonable, alternative estimates of E(max). Accordingly, we studied 19 patients with simultaneous high-fidelity micromanometer LV and fluid brachial artery (Ba) pressure recordings, CINE, and RNA under control conditions and during methoxamine and nitroprusside infusions. E(max) was defined for CINE and RNA as the maximum slope of the linear relation of isochronal, instantaneous P-V data points obtained from each of the three loading conditions. The indirect P-V relations were similarly obtained from Ba peak (P) pressure versus minimum RNA LV volume (BaP/minV) and Ba dicrotic notch (di) pressure versus minimum RNA LV volume (Badi/minV) data points. The mean heart rates and LV(+)dP/dtmax values were minimally altered during the three loading conditions. The isochronal E(max) values ranged from 1.40 to 6.73 mmHg/ml (mean 4.13 ± 1.99 s.d. mmHg/ml) for CINE and from 1.48 to 7.25 (mean 4.35 ±7 1.81 mmHg/ml) for RNA (p = N.S.). Similarly, the unstressed volumes ranged from -10 to 80 ml (mean 30 ± 23 ml) for CINE and from -8 to 77 ml (29 ± 21 ml) for RNA (p = N.S.). The individual, isochronal E(max) values by RNA correlated with those by CINE (r = 0.86). In 14 of the 19 patients, the BaP/minV and Badi/minV relations correlated with the isochronal E(max) values calculated by RNA (r = 0.83 and 0.82, respectively), and these relations also correlated with the E(max) values calculated by CINE (r = 0.82 and 0.78, respectively). The slope and V0 values for the BaP/minV and Badi/minV relations underestimated those for E(max) by RNA and CINE (p < 0.01 and p < 0.05, respectively, for both). Thus, the isochronal E(max) values calculated using RNA are comparable to those obtained using CINE in man. Moreover, indirect P-V relations underestimate these E(max) values, but they are linearly related with the isochrnal E(max) values calculated by RNA and CINE. Consequently, these indirect P-V relations may provide a more simple, alternative estimate of LV contractile function in man.