INCREASED ECHODENSITY OF MYOCARDIAL WALL IN THE DIABETIC HEART - AN ULTRASOUND TISSUE CHARACTERIZATION STUDY

Objectives. We sought to characterize myocardial echodensity in asympt omatic patients with insulin-dependent diabetes and normal conventiona l two-dimensional echocardiographic findings to determine whether ultr asound tissue characterization can detect ultrastructural changes in m yocardium, such as an increase in collagen content. Background. Fibros is alters the acoustic properties of the heart in animals and humans, and these changes are detectable by cardiac tissue characterization wi th ultrasound. Early changes detected in the diabetic heart include in creased interstitial collagen deposition. Methods. Using two-dimension al echocardiography, we evaluated 26 asymptomatic patients with insuli n dependent diabetes with normal regional and global rest function, an d 17 age- and gender-matched control subjects. By selection, all diabe tic patients were normotensive and had negative maximal exercise stres s test results to avoid the confounding effects of hypertension and co ronary artery disease. Using an echocardiographic instrument implement ed at the Institute of Clinical Physiology, we performed an on-line ra diofrequency analysis to obtain quantitative operator-independent meas urements of the integrated backscatter signal of the ventricular septu m and posterior wall. The integrated values of the radiofrequency sign al from the myocardial wall were normalized for those from the pericar dial interface and were expressed as percentages (integrated backscatt er index). Results. Diabetic patients showed a significant increase in myocardial echodensity both in the septum ([mean +/- SD] 36.6 +/- 8.1 vs. 23.6 +/- 4.4, p < 0.0001) and posterior wall (21.2 +/- 5.3 vs. 18 .4 +/- 3.7, p < 0.001). By individual patient analysis, 17 patients ex ceeded the 95% confidence limits for normal myocardial echocardiograph ic reflectivity found in normal subjects, and only 3 had a relatively abnormal transmitral Doppler filling pattern (E/A ratio), mainly consi sting of an abnormally increased late peak flow velocity (65% vs. 11%, p < 0.001). The increased myocardial intensity was similar in patient s with (n = 16) and without in = 10) noncardiac complications, such as retinopathy or nephropathy (37.5 +/- 7.9% vs. 35.0 +/- 8.3%, p = 0.35 ). Conclusions. Abnormally increased myocardial echodensity, possibly related to collagen deposition, can be detected in asymptomatic diabet ic patients with normal rest function. Theoretically, this finding mig ht be considered a very early preclinical alteration potentially relat ed to subsequent development of diabetic cardiomyopathy.