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Is QRS Duration a Predictor of Adverse Outcomes in HFpEF?
Study Questions:
What is the relationship of baseline QRS duration to clinical outcomes in subjects enrolled in the TOPCAT (Treatment of Preserved Cardiac Function Heart Failure With an Aldosterone Antagonist) trial?
Methods:
This was a post hoc analysis of the TOPCAT trial. Investigator-reported QRS duration, and data on specific conduction defects were available at baseline for 3,426 of 3,445 subjects (99.4%). QRS duration was analyzed as a dichotomous variable (≥120 ms or <120 ms) and as a continuous variable to determine its relation to the primary outcome (composite of cardiovascular death, aborted cardiac arrest, or heart failure [HF] hospitalization), and to each component of the primary outcome. Multivariable analysis was conducted to adjust for variables that were significant correlates of QRS duration ≥120 ms in the full population and in subjects enrolled in the Americas and in Russia/Georgia (due to regional differences in outcomes observed in the TOPCAT trial).
Results:
The prevalence of QRS duration >120 ms at baseline was 17.9%. The primary outcome was strongly associated with QRS duration >120 ms in the whole sample even after adjusting for correlates of wide QRS. Whereas unadjusted analysis showed a highly significant association of the primary outcome with QRS duration >120 ms in the Americas and Russia/Georgia, these relationships were reduced to borderline statistical significance after adjusting for global and regional variables. After adjustment for global correlates of a prolonged QRS duration, HF hospitalizations were significantly associated with right bundle branch block (RBBB) and left BBB, and the primary outcome was associated only with RBBB. There was no interaction between treatment with spironolactone and QRS duration.
Conclusions:
Among individuals with HF with preserved ejection fraction (HFpEF), prolonged QRS duration identifies those who may be at increased risk for adverse outcomes.
Perspective:
This is an interesting study that suggests the value of QRS duration in predicting outcomes in HF with reserved EF (HFrEF) patients. Certainly prolonged QRS duration is unequivocally associated with worse clinical outcomes and status in HFrEF. While the mechanism of the same association in HFpEF patients is not fully clear, the authors of this study convincingly establish the relationship, save some regional differences. As the authors emphasize, future studies (such as the ongoing KaRen study) will address whether electric dyssynchrony has a biologic influence on progression of HFpEF (and whether cardiac resynchronization therapy is warranted in this setting).
Keywords: Arrhythmias, Cardiac, Bundle-Branch Block, Cardiac Resynchronization Therapy, Heart Arrest, Heart Conduction System, Heart Failure, Outcome Assessment, Health Care, Spironolactone
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