Haemodynamic insights into the effects of ischaemia and cycle length on tissue Doppler-derived mitral annulus diastolic velocities

In the present study, we performed simultaneous epicardial echocardiography and left heart catheterization on ten adult dogs to investigate the effects of ischaemia and tachycardia on the mitral annulus early (E_a) and late (A_a) diastolic velocities and the haemodynamic mechanisms involved. Left atrial pressure and left ventricular (LV) volumes and pressures were measured with 5 French Millar catheters. In each dog, inferior vena cava occlusion was used to alter preload and circumflex coronary artery occlusion was applied to induce ischaemia at two different cycle lengths: 450 and 550 ms. At both cycle lengths, ischaemia resulted in a reduction in LV relaxation, LV global and ipsilateral systolic function, transmitral pressure gradient (TMG), E_a and A_a (P<0.05). The shorter cycle length was associated with a shorter tau (time constant of LV relaxation), reduced TMG and reduced septal and lateral E_a (P<0.05 for all variables). Both septal and lateral A_a were significantly increased (P<0.05). Ischaemia influences E_a through changes in LV relaxation, global and regional systolic function and TMG. An increase in heart rate reduces E_a, but increases A_a.