Four-chamber heart dynamics: Modeling with in vivo validation via MRI

Previous studies in dogs using the dynamic spatial reconstructor have shown that the total (blood + tissue) volume of the pericardial sack remains constant (within a few percent) throughout the cardiac cycle. Others have reported that pericardial volume in humans remains constant for parts of the cardiac cycle. We use three-dimensional datasets acquired using cardiac MRI to determine the constant-volume attribute of the four-chamber heart. The four-chamber constant-volume attribute is achieved by reciprocal variation of atrial and ventricular volumes, requiring oscillation of the atrioventricular valve plane. We develop a lumped parameter oscillator model having fixed external dimension to model atrioventricular (mitral) valve plane location as a function of time. We conclude that the constant volume attribute of the four-chambered heart is accurate to within 4-6%, and constant-volume based modeling of heart dynamics can predict mitral valve plane displacement throughout the cardiac cycle.