Long-term effect of aldosterone inhibition on cardiac structural abnormality as assessed with analysis of ultrasonic radio frequency signals

Abstract

Background: Aldosterone antagonists are considered as one of interventions that may provide additional benefits to standard therapy of congestive heart failure. Experimental studies have suggested that aldosterone inhibition provides benefits through effects on cardiac structure; however, the confirmation of these experimental results in patients has been difficult because of limited tools for assessment of LV structure. Recently, we have reported that analysis of ultrasonic radio-frequency (RF) signals obtained from myocardium may have a potential of detecting structural damage noninvasively. Methods and Results: To assess long-term effect of aldosterone inhibition on cardiac structure, myocardial RF signals were analyzed in 15 patients with LV hypertrophy (LV mass index>120g/m2) before and after 6 and 12 month-administration of spironolactone. There were no changes in LV end-diastolic diameter, ejection fraction and LV mass index throughout the study protocol. Attractors constructed from RF signals formed a thin ring-like structure consisting of a relatively empty, roughly circular core (quasi-periodic pattern) before the administration and changed to chaotic pattern 6 and 12 months after the administration. The mean value of correlation dimension (CD) calculated from the RF signals of all the subjects increased towards a normal level (2.6±0.1 vs. 3.0±0.2, p<0.05) at 6 months and there was no further increase from 6 to 12 months (3.1±0.2). At 6 months, the value increased in 8 patients, decreased in 5 patients and did not change in 2 patients. In any patients, the value did not further change from 6 to 12 months. Plasma level of collagen type 1 telopeptide increased in the patients with increased value of CD at 6 months and did not further change from 6 to 12 months. Conclusion: Thus, aldosterone inhibition may accelerate collagen turnover, resulting in attenuation of structural abnormality as confirmed by this new ultrasonic technique for tissue characterization. Its effects on cardiac structure are likely to reach a plateau within 6 months after the initiation of medication, and to be maintained thereafter.