Strain rate imaging in normal and reduced diastolic function: comparison with pulsed Doppler tissue imaging of the mitral annulus

Abstract

Objectives: The pixel velocity values obtained by color Doppler tissue imaging (DTI) can be processed to velocity gradients as a measure of longitudinal strain rate with a technique termed strain rate imaging (SRI). Color mapping of strain rate does show the spatial-temporal relations of the diastolic phases. The phases of early filling and late filling during atrial systole can be seen to consist of a stretch wave in the myocardium, propagating from the base to the apex. Diastolic function is characterized by both peak strain rate and propagation velocity of this wave. The goals of this study were to establish normal values for these measurements and to study the changes with minimal diastolic dysfunction.

Methods: Twenty-eight healthy control subjects and 26 patients with hypertension and normal systolic function were studied. The patients had normal blood pressure on treatment, normal ejection fraction, minimal hypertrophy, and moderately prolonged deceleration and isovolumic relaxation times. Real-time SRI color cineloops, ordinary echocardiography and Doppler recordings, and pulsed wave DTI from the mitral ring were acquired and processed.

Results: Patients showed a reduction of systolic and early diastolic tissue velocities and strain rates and no significant increase in late diastolic tissue velocity and strain rate. Propagation velocity of diastolic strain during both early and late filling phases was reduced in the patients. The combination of changes in peak strain rate and propagation velocity of strain rate corresponded with changes in DTI.

Conclusion: Diastolic deformation of the ventricle can be shown as a complex series of events, with temporal sequences in the ventricle. The peak strain rate and the propagation velocities of strain rate can describe the two main diastolic events: early and late filling. In reduced diastolic function, both are reduced during early filling. The velocities of the mitral ring are the result of this combination. This adds information about the physiology and pathophysiology of diastole.