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[Relationship between ambulatory blood pressure and myocardial performance index in hypertensive patients].

OBJECTIVE
To explore the relationship between ambulatory blood pressure and myocardial performance index (MPI) in hypertensive patients.


METHODS
A total of 76 hospitalized patients with untreated hypertension from January to June 2013 were recruited. They received the examinations of office blood pressure, 24 h ambulatory blood pressure and echocardiography. MPI was determined by the following formula: MPI=(isovolumic contraction time+isovolumic relaxation time)/ejection time. Based upon left ventricular MPI, they were divided into two groups of MPI>0.47 (n=38) and MPI≤0.47 (n=38). The mean levels of office blood pressure, ambulatory blood pressure, blood pressure load, morning blood pressure surge (early morning blood pressure minus the lowest night-time blood pressure) and nocturnal blood pressure changes were compared between two groups. And the determinants of MPI were identified by multivariate regression analysis.


RESULTS
As compared to those with MPI≤0.47, patients with MPI>0.47 had higher 24 h and daytime systolic blood pressures, 24 h, daytime and nighttime diastolic blood pressures, 24 h, daytime and nighttime systolic blood pressure loads, 24 h, daytime and nighttime diastolic blood pressure loads and morning systolic blood pressure surges (all P<0.05). No inter-group differences existed in the mean levels of office blood pressure, nighttime systolic blood pressure, morning diastolic blood pressure surge, nocturnal systolic or diastolic blood pressure changes (all P>0.05). Multivariate regression analysis showed that nocturnal diastolic blood pressure (β=0.285, P=0.005) and daytime systolic blood pressure load (β=0.397, P<0.001) were independently associated with MPI. And other factors independently associated with MPI were left ventricular mass index (LVMI) and early diastolic mitral annular velocity (Em).


CONCLUSION
The increases of blood pressure level and blood pressure load are associated with an elevation of left ventricular MPI.