Heart rate-guided, but not dose-guided titration of beta blockers stabilizes ventricular repolarization in patients...

We compared the effects of heart rate-guided and dose-guided beta-blocker titration strategies on QT variability in patients with chronic heart failure (CHF).

In a prospective study we recorded 5-minute resting high-resolution ECGs (HRECG) in 100 patients with CHF and measured heart rate (HR) and ventricular repolarization by QT variability index (QTVI). In a subgroup of patients not reaching target HR (<70bpm) we uptitrated beta blockers and repeated HRECG measurements 3months thereafter.

Target HR was present in 46 patients (group A), and in 54 patients HR was above target (group B). The groups did not differ in age, gender, NYHA class, NT pro-BNP, creatinine, or beta blocker dose. Patients in group A displayed significantly lower QTVI than patients in group B (-1.25±0.55 vs. -1.52±0.42, P=0.013). When uptitrating beta-blockers we found a decrease in HR (from 91±15bpm to 71±15bpm, P<0.001), NTpro BNP levels (from 4474±3878pg/ml to 3042±2566pg/ml, P=0.024), and NYHA class (from 3.0±0.8 to 2.5±0.7, P=0.006). With beta-blocker uptitration QTVI decreased in 10 of 24 patients (42%). In these patients HR decreased more than in the remaining cohort (-25±20bpm vs. -15±17bpm, P=0.017). On multivariate analysis, the presence of target HR was a predictor of QTVI decrease (P=0.017), but beta-blocker dose was not.

In patients with CHF treated by beta-blockers, changes in QT variability appear to occur in parallel with changes of heart rate. This suggests that heart rate-guided titration of beta-blockers may be associated with decreased risk of sudden cardiac death.