Preventive Role of Cardiac Resynchronisation Therapy in Heart Failure

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Summary

Preventive Role of Cardiac Resynchronisation Therapy in Heart Failure

The role of CRT is continually evolving, and recently has extended to patients with bradycardia requiring frequent ventricular pacing (> 40 %) and left ventricular ejection fraction (LVEF) ≤35 %,⁵ who are candidates for a conventional pacemaker. A growing body of evidence shows that right ventricular (RV) pacing has a detrimental effect on left ventricular (LV) function and remodeling despite normal ejection fraction before implantation. Both pacing-induced cardiomyopathy⁷ and new-onset of HF⁸ are frequently encountered in patients undergoing RV pacing, even in those with less than 40 % accumulative pacing and in the short-term (less than one month) pacing. Despite satisfactory response to CRT upgrading in patients with RV pacing-induced LV remodeling or HF,⁹ this is a “wait-and-see” approach, especially for outpatients with infrequent echocardiographic examination. Therefore, pacing-induced LV dysfunction might be avoided with de novo implantation of CRT. The results of the Biventricular versus Right Ventricular Pacing in Heart Failure Patients with Atrioventricular Block (BLOCK HF trial) supported the superiority of CRT to RV pacing as demonstrated by the significant reduction of total mortality, urgent HF care, or an increase in LV end-systolic volume index in patients with HF and conventional indications for pacing.¹⁰ The inclusion criteria for the BLOCK-HF trial included patients with LV ejection fraction <50 %, not confined to <35 % as in other HF and CRT trials. In terms of patients with bradycardia and normal ejection fraction, the Pacing to Avoid Cardiac Enlargement (PACE) trial and extended follow-up consistently demonstrated the superiority of CRT over RV pacing in prevention of LV remodeling and deterioration of systolic function, as well as reduction of HF in the long-term follow-up.^11–13 However, preliminary results of the Biventricular pacing for atrIo-ventricular BlOck to Prevent cArdiaC dEsynchronisation (BIOPACE) trial showed that CRT failed to significantly improve outcomes compared to RV pacing in atrioventricular (AV) block (preliminary result, in annual scientific meeting in ESC 2014). Nevertheless, data from this trial should be interpreted with care due to the relatively high failure rate of implantation and lower accumulative ventricular pacing percentage (90 % at one month), which might have an impact on the primary endpoint. Currently, CRT is unlikely to completely replace conventional RV pacing, even in patients with high-degree AV block; however, its preemptive role in HF deterioration and HF occurrence should be acknowledged although further study is necessary to fully elucidate its effects.