Center of volume and total heart volume variation in healthy subjects and patients before and after coronary bypass surgery

Background: Total heart volume variation (THVV) and center of volume variation (COVV) likely affects the efficiency of cardiac pumping, but no study has determined COVV of the heart throughout the cardiac cycle or the effect of surgery on THVV in adults. Therefore, the purposes of this study were to determine COVV in healthy adults and patients with cardiac failure due to ischemic heart disease (IHD), identify any difference in THVV between these two groups, and determine how these parameters are affected by coronary bypass surgery. Methods: Six healthy volunteers and eight patients before and after surgery were investigated with cardiovascular magnetic resonance imaging. The atrioventricular plane movement (AVPM), THVV and time resolved three-dimensional coordinates of the center of the cardiac volume (COVV) were measured. Results: COVV followed a loop in 3D space that between the end-points was approximately 2 mm with no difference between healthy subjects and patients before surgery (P = 0.093), although AVPM was significantly lower in patients (P = 0.002). However, after surgery the COVV during the cardiac cycle doubled (P = 0.012) and the increase in THVV was significant (P = 0.050), although of very small magnitude, and the AVPM remained unchanged (P = 0401). Conclusion: COVV and THVV were similar in patients and healthy subjects even though AVPM was lower in the patient population. After surgery, however, COVV doubled despite a very small change in THVV and no change in AVPM. Taken together, the results of this study may provide new insights into the energy expenditure and efficiency of cardiac pumping.