QT dynamicity in patients with worsening heart failure

Abstract Alteration of ventricular repolarization is associated with the increased risk of sudden cardiac death in various cardiac diseases. Little information is available as to the dynamic QT interval changes in patients with worsening heart failure (HF). In 109 patients with CHF (age 65 ± 8 years; 90 men), we recorded 24-hour Holter ECG recorded at hospital admission and discharge and compared with age- and sex-matched controls (n = 55). RR, QT and rate-corrected QT intervals were automatically calculated by the analyzer, and hourly and 24-hour mean values were derived. At hospital admission, RR (722 ± 19 ms) and QT intervals (390 ± 3 ms) were decreased significantly compared with those in controls (RR 890 ± 75 ms, QT 409 ± 16 ms) and exhibited blunted circadian variation. At discharge from hospital, RR interval increased to similar value in controls (919 ± 50 ms) but QT interval significantly prolonged than controls (430 ± 10 ms). There was a pronounced circadian variation in the QT interval in parallel with the trend in the RR interval in controls and HF patients before discharge. Improvement of heart failure associated with the normalization of RR and QT intervals obtained from 24-hour Holter ECG. Such phase-dependent alterations in the QT interval dynamicity may help to understand complex arrhythmogenic substrates in HF.