Relation between submaximal exercise test to evaluate response to resynchronization therapy and change in quality of life: a substudy of the GREATER-EARTH trial

Abstract

Purpose: A novel method of evaluating response to cardiac resynchronization therapy (CRT) was introduced in the EARTH trials. This substudy sought to assess the relationship between response to CRT using submaximal treadmill exercise testing, and quality of life (QoL) measures. Methods: The GREATER-EARTH trial was a multicentre, randomized, double-blind crossover trial evaluating left ventricular versus biventricular pacing in patients requiring an implantable cardioverter-defibrillator and CRT (LVEF <35% and QRS duration ≥ 120 msec). A total of 121 patients were randomized to CRT by left ventricular pacing (LV) followed by biventricular pacing (BiV) or vice versa for consecutive 6-month periods. The present analyses were restricted to the first 6-month period to avoid carryover effects. Clinical response to CRT was pre-defined as an increase of ≥20% duration of submaximal treadmill exercise testing at 6 months compared to baseline. QoL was assessed at baseline and 6 months using generic (SF-36, Physical [PCS] and Mental [MCS] components) and disease-specific (Minnesota Living with Heart Failure [LWHF]) questionnaires. The relationship between responder status according to submaximal exercise test and change in QoL scores was assessed using multivariate linear regression. Results: Clinical responders showed significant improvements in QoL scores between baseline and 6 months (decrease in LWHF 15 points [p 0.30). Responder status was the only independent predictor of change in QoL scores; resynchronization mode (LV vs BiV), interaction between mode and responder status, age and sex were not independently associated with changes in QoL. Changes in the duration of submaximal exercise testing showed moderate but significant correlations with changes in LWHF (Spearman's ρ= -0.38; p<0.0001) and PCS scores (ρ=0.46; p<0.0001). An exploratory regression tree analysis showed that using a cut-off value of 55% improvement in duration of submaximal exercise testing instead of 20% to define response provided the best discrimination in terms of QoL score change. Conclusions: Submaximal treadmill exercise testing adequately reflects changes in quality of life after resynchronization therapy. Although this test should be compared to other means of assessing response and refined as to its best cut-off value, it has great potential in patient evaluation following resynchronization therapy.