Mitral annulus energetics as determinants of left ventricular filling: quantification of atrioventricular interactions

Aims During left ventricular ejection, the mitral annulus is pulled towards the cardiac apex, thus enlarging the left atrial cavity. Its rapid early d iastolic retraction is synchronous with the transmitral E wave and so may b e the result of an elastic force due to displacement of the annulus from it s equilibrium position. We aimed to quantify these effects. Methods and Results We studied 20 patients (age 63 +/- 7 years) with corona ry artery disease and normal left ventricular function by transoesophageal echocardiography and simultaneous high fidelity left atrial pressure immedi ately before bypass grafting with the pericardium open. The annulus positio n was derived by M Mode and its rate of change by digitization of the recor ds, thus deriving instantaneous power and its time integral representing wo rk. In all patients the power curve was triphasic. During atrial systole th e power curve was positive representing compressive work done on the atrium (work 0.46 +/- 0.2 mJ . cm(-2) peak power 6.3 +/- 2.0 mW . cm(-2)). During ventricular systole, as the mitral ring enlarges the atrium, the power cur ve becomes negative (work -1.9 +/- 0.6 mJ . cm(-2), peak power -7.6 +/- 3.0 mW . cm(-2)). During early diastole the power curve again becomes positive (work 0.64 +/- 0.2 mJ . cm(-2), peak power 7.3 +/- 2.0 mW . cm(-2)). The r atio of early to late diastolic annular work correlated with the transmitra l E/A ratio for both peak velocities and velocity time integrals (r=0.82, P <0.0001). Conclusion Compressive work by the mitral annulus on the left atrium during early diastole confirms that rapid ring retraction represents dissipation of potential energy derived from systole. The close correlation of early an d late diastolic annular work with the transmitral E/A ratio suggests that the energy dissipated is directly coupled to early diastolic ventricular fi lling.