Left ventricular energy in mitral regulation: a preliminary report

Energy exchange based on Newtonian principles is the‐most appropriate way to express the function of any pump ‐ including the heart. Using information obtained at cardiac catheterisation, we have measured the total work energy (E_T) of the left ventricle (LV) (mean 1.63 J) in patients with severe mitral regurgitation (mean regurgitant fraction 0.66). E_T was approximately‐84% above normal. Of the regurgitant energy (RE)(mean 0.95 J), on average, ¾ (73.6%)was‐kinetic (KE) and ¼ (23‐4%) potential (PE). Both components represent wasted LV energy, the Kinetic energy associated with the lost as heat, the potential energy responsible for a fix in Left Atrial (LA) pressure. The‐amount of PE as a percentage of total regurgitant Energy (RE) varied considerably from, one patient to another (10.5% to 54.4%) Hence, colour flow mapping which detects‐only KE of turbulent jet flow must underestimate LV energy loss and, because of patient to patient variation, cannot consistently reflect severity of regurgitation. Measurements of PE correlate well with wedge P‐wave height. Corresponding non‐invasive estimates were made using sphygmodynamometer‐calibrated indirect carotid pulse tracings and echocardiographic measurements. These were not significantly different from the invasive measurements. Unfortunately, the calculation of PE is indirect and invlves subtraction, so that measurements for individual patients were not accurate enough, for clinical use. Paxt of the non‐invasive calculation involved an estimate of left atrial pressure based on the blood pressure measurement and Doppler velocity of regurgitation; this should be a useful measurement in itself. Measurement of E_T, an index of both volume and pressure overload (reflecting peripheral resistance changes), should be tested in serial studies as a predictor of left ventricular‐failure in severe mitral regurgitation. Non‐invasive measurements would be useful to follow patients with acute severe mural regurgitation: Non‐invasive PE measurements are currently not reliable enough but an indirect measurement of left atrial pressure would be very useful.