Parameters derived by ultrasonic myocardial characterization in dialysis patients are associated with mortality

Autopsy studies have shown that hypertrophic hearts of uremic patients have peculiar characteristics. Changes in tissue structure are detectable by ultrasound as changes in echo reflectivity.

We studied 96 dialysis patients, 18 hypertensive subjects with normal renal function and 52 healthy subjects. The echo pattern of interventricular septum was assessed by videodensitometry (VDT) (i.e., a computer-assisted quantitative analysis of gray levels). For each pixel a numerical value from 0 (black) to 255 (white) was assigned. From the resulting histogram of gray level frequency distribution, we obtained indexes of central tendency (reflectivity) and of homogeneity of distribution (uniformity).

For the same septum thickness, dialysis patients showed a significantly greater reflectivity (87 +/- 19 and 70 +/- 17) (P < 0.001) and lower uniformity (137 +/- 32 and 184 +/- 71) (P < 0.007) compared with hypertensives. Hypertensive patients showed VDT parameters similar to control subjects in spite of significantly higher septum thickness (P < 0.003). Followed up after 5 years, dialysis patients with a reduced homogeneity of distribution of gray levels (lower uniformity) showed a significantly shorter survival (HR by Cox 2.5, 95% CI 1.21-5.27).

For a similar degree of cardiac hypertrophy, dialysis patients differed widely from hypertensives in their VDT parameters. By contrast, the hypertensive heart differed from the normal heart in the degree of hypertrophy but not in terms of VDT parameters. VDT parameters are independent predictors of all-cause mortality in dialysis patients.