Time-frequency analysis of the RT and RR variability to stratify hypertrophic cardiomyopathy patients

The RT interval is a measure of the ventricular repolarization and is parti ally influenced by the sympathovagal balance. The analysis of the variation of the duration of the RT and RR intervals might bring new information abo ut the arrhythmogenic vulnerability and autonomic imbalance. The RR signal and its spectral density (SD) are characterized by two difficult patterns d uring the sleep period. On the basis of this information. RT and RR sequenc es have been automatically classified into two patterns. R and N. In this w ork, we propose a methodology to define new variables that are able to dist inguish patients with hypertrophic cardiomyopathy (HCM) who later developed sudden cardiac death (SCD) from HCM patients without such episode during t he follow-up. These variables are based on the instantaneous frequency calc ulation using time-frequency representation of the RT and RR signals previo usly classified into R and N patterns. In this study, three spectral bands have been considered: low-frequency band (LF 0-0.07 Hz). mid-frequency band (ME 0.07-0.15 Hz). and high-frequency band (HE 0.15-0.45 Hz). Then a suita ble combination of mean energy and mean frequency ol. the RT and RR signals in the MF and HF bands has allowed HCM patients with SCD to be discriminat ed from HCM patients without SCD (P < 0.001). (C) 2000 Academic Press.