Long-term outcome after upgrade to cardiac resynchronization therapy: A propensity score-matched analysis.

In this retrospective analysis, the outcome of patients who underwent upgrades to CRT differed significantly from patients who underwent de novo CRT implantation, particularly for upgrades from ICD. Importantly, this difference in outcome does not imply a causal relation between therapy and outcome but rather a difference between two different patient populations. This article is protected by copyright. All rights reserved.