Prognostic Value of Cardiac Time Intervals Measured by Tissue Doppler Imaging M-mode in the General Population

Objective: Tissue Doppler imaging (TDI) M-mode through the mitral leaflet is an easy and precise method to estimate the cardiac time intervals. The aim was to evaluate the usability of the cardiac time intervals in predicting major cardiovascular events (MACE) in the general population.

Methods: In a large prospective community-based study, cardiac function was evaluated in 1915 participants by both conventional echocardiography and TDI. The cardiac time intervals, including the isovolumic relaxation time (IVRT), isovolumic contraction time (IVCT) and ejection time (ET), were obtained by TDI M-mode through the mitral leaflet. IVCT/ET, IVRT/ET and the myocardial performance index (MPI=(IVRT+IVCT)/ET) were calculated.

Results: During follow-up (median 10.8 years), 383 (20%) participants reached the combined endpoint MACE (ischaemic heart disease, heart failure or cardiac death). After multivariable adjustment for clinical predictors and conventional echocardiography, only the combined indexes, including information on both systolic and diastolic performance (IVRT/ET and MPI), remained significant prognosticators (p<0.05 for both). Adding IVRT/ET or MPI to a model already including all other echocardiographic parameters resulted in a significant increase in the c-statistics (0.76 vs 0.75 p<0.01 for both). IVRT/ET or MPI improved reclassification significantly when added to the clinical predictors (p<0.05 for both).

Conclusions: In the general population, the combined cardiac time intervals that include information on both systolic and diastolic function in one index (IVRT/ET and MPI) are not only powerful and independent predictors of future MACE, but provide additional prognostic information to clinical and conventional echocardiographic measures of systolic and diastolic function.