Noninvasive measurement of left ventricular contractility using gated myocardial SPECT and arterial pressure tonometer

For the estimation of left ventricular (LV) contractility, the fully noninvasive measurement of the maximum elastance (E_max) from the steady-state single loop of end systolic pressure volume relation (ESPVR) is attempted. For 32 patients with coronary artery disease, we performed the gated myocardial SPECT with the simultaneous measurement of radial artery pressure using automated tonometer. The left ventricular volume generated from quantitative gated SPECT (QGS) program of SPECT and the central aortic pressure transferred from radial artery pressure measured by automated tonometer were used to make a pressure-volume (PV) loop. With a single PV loop, E_max, was calculated using (1) single PV loop estimation method based on the consistency of normalized elastance curve and (2) regression method based on time-linearity of elastance, respectively. The values of E_max by the first method were distributed within the range (2.3-5.3) and showed the independence on calculation trials and initial condition for iterative calculation. Normalized elastance curves were consistent for all patients. The E_max and V₀ for PV data from sequential gated SPECT acquisition showed the consistent value, respectively (r=0.91 for E_max, r=0.99 for V₀). The values of E_max by the second method were within (0.7-5.1) and showed the linear relationship (E_{max normalized}=2.15×E_{max linear}+0.45, r=0.64, p<0.001) with E_max by the first method. Despite of the lack of comparison with multiple PV loop method, we found the clinical feasibility of this fully noninvasive E_max, estimation method. Therefore, we concluded that E_max obtained by this methods could be useful for assessment of LV contractility