Background: After acute myocardial infarction (MI) the severity of diastolic dysfunction by echocardiography represents an independent prognostic marker. However, the mechanisms whereby diastolic dysfunction portends an increased risk after MI are not fully understood. We investigated the relationship between echocardiographic diastolic dysfunction severity and infarct size quantitatively measured by contrast-enhanced magnetic resonance (ce-MR).
Methods: Cross-sectional prospective study. We quantified "healed" infarct size by ce-MR measuring the percentage of delayed enhancement with respect to left ventricular mass and diastolic function by Doppler echocardiography. Both exams were scheduled at least 1 month after a first acute ST segment elevation MI (STEMI) successfully treated with primary angioplasty and stenting. To increase the specificity, individual echocardiographic parameters were integrated to grade global diastolic function in 4 grades: normal diastolic function, impaired relaxation with normal, or near-normal filling pressures; impaired relaxation with moderate elevation of filling pressures, and impaired relaxation with marked elevation of filling pressures, "restrictive filling."
Results: We prospectively enrolled 52 patients (mean age 62 +/- 13 years, 77% men). ce-MR and echocardiography were performed 48 +/- 15 days after the MI. There was a significant but modest correlation between diastolic function grade and infarct size (r = 0.423, P = 0.002), which was independent of global and regional systolic function and persisted after further adjustment for age, sex, body surface area, left ventricular mass, end-diastolic volumes, and sphericity index (all P < 0.05). Among single echocardiographic variables, infarct size correlated best with tissue Doppler velocities Em (r =-0.307, P = 0.03), Am (r =-0.39, P = 0.005), and flow propagation velocity (r =-0.34, P = 0.015).
Conclusions: In healed STEMI successfully treated with primary angioplasty and stenting, diastolic function grade was independently albeit weakly correlated with infarct size. Therefore, the increased risk of diastolic dysfunction after MI is not fully explained by infarct size.