Color M-mode Doppler flow propagation velocity is a preload insensitive index of left ventricular relaxation: animal and human validation

OBJECTIVES To determine the effect of preload in color M-mode Doppler flow propagation velocity (vp). BACKGROUND The interpretation of Doppler filling patterns is limited by confounding effects of left ventricular (LV) relaxation and preload. Color M-mode vp has been proposed as a new index of LV relaxation. METHODS We studied four dogs before and during inferior caval (IVC) occlusion at five different inotropic stages and 14 patients before and during partial cardiopulmonary bypass. Left ventricular (LV) end-diastolic volumes (LV-EDV), the time constant of isovolumic relaxation (tau), left atrial (LA) pre-A and LV end-diastolic pressures (LV-EDP) were measured. Peak velocity during early filling (E) and vp were extracted by digital analysis of color M-mode Doppler images. RESULTS In both animals and humans, LV-EDV and LV-EDP decreased significantly from baseline to IVC occlusion (both p < 0.001). Peak early filling (E) velocity decreased in animals from 56 ± 21 to 42 ± 17 cm/s (p < 0.001) without change in vp (from 35 ± 15 to 35 ± 16, p = 0.99). Results were similar in humans (from 69 ± 15 to 53 ± 22 cm/s, p < 0.001, and 37 ± 12 to 34 ± 16, p = 0.30). In both species, there was a strong correlation between LV relaxation (tau) and vp (r = 0.78, p < 0.001, r = 0.86, p < 0.001). CONCLUSIONS Our results indicate that color M-mode Doppler vp is not affected by preload alterations and confirms that LV relaxation is its main physiologic determinant in both animals during varying lusitropic conditions and in humans with heart disease.