Evaluation of regional work from ECG-gated SPECT images through solution of equations of continuity for fluids-mechanical cardiac work calculated using thin wall model

摘要

Regional contraction work (RCW) of left ventricle (LV) was evaluated from cardiac perfusion images of ECG-gated single photon emission computed tomography (ECG-SPECT). The mechanical work was computed as a product of force and displaced distance. Force was determined from Laplace's law under a rectangle pressure. Deformation of wireframe representing LV was calculated from equations of continuity for two-dimensional fluids. Experiments were performed with homemade life-sized cardiac models. Total contraction work (TCW) and stroke work (SW) were 524.0 ± 166.1 mJ/beat and 709.8±169.5 mJ/beat, respectively, in normal subjects (n = 23). Moderate correlation was seen between TCW and SW (y =43.4+0.779 x, r = 0.815). The regional contraction amplitude (RCA), synchronous contraction index and RCW were 35.4±3.5%, 95.4±3.1% and 5.58±0.97 mJ cm ~2/beat in normal subjects, whereas those in patients with decreased ejection raction (EF)≤30% (n = 6) were 19.6±7.7%, 64.4±32.2% and 2.58±0.82 mJ cm ~2/beat (p < 0.0001, Student's t-test). There was a poor correlation between RCW and RCA (y = 1.648±0.116 x, r = 0.501) in normal subjects, suggesting that it might not be suitable to use RCA as an alternative to evaluate RCW.