Introduction
Heart failure (HF), a major public health issue, is becoming more prevalent due to the aging and longer survival of cardiovascular patients [1]. As HF progressing, pump failure and life-threatening ventricular arrhythmias are major causes of death [2]. Implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy (CRT) are widely applied to mild or severe HF patients with reduced ejection fraction and a wide QRS duration to reduce all-cause mortality [3].
The COMPANION trial has demonstrated that CRT with or without ICD (CRT-D or CRT-P) can decrease the risk of all-cause mortality and CRT-D was associated with a lower mortality, but there is no definitive comparison between CRT-D and CRT-P [4]. Then, plenty of observational studies reported the various outcome of CRT-D comparing to CRT-P, and a meta-analysis including nineteen studies presented that the addition of an ICD is associated with a reduction in the risk of all-cause mortality [5]. However, we cannot deny significant differences in clinical characteristics between two groups in these studies. Patients in CRT-P group were generally older age, more comorbidities and more frailty, which may introduce selection bias and resulting the consequence to be incorrect [6].
Due to lack of strong randomized evidence, it still remains controversial whether CRT-D can bring benefits compared with CRT-P. Current guideline of the European Society of Cardiology recommend that the clinician should choose CRT-P or CRT-D whichever they consider appropriate [7]. However, this choice in practice may put clinicians in a dilemma. So far, several studies focusing on the comparison of CRT-D and CRT-P in all-cause mortality has been reported, which used Cox multivariate analysis or propensity score matching to minimize the influence of clinical differences between groups[6,8-19].Therefore, we aim to review those studies to clarify the association of all-cause mortality and additional ICD in patients receiving CRT, and optimize the management of patients based on characteristics.