Patients with non-ischaemic dilated cardiomyopathy and hyper-responders to cardiac resynchronization therapy: characteristics and long-term evolution.

Aims: In some patients with non-ischaemic dilated cardiomyopathy (NIDCM), left bundle branch block (LBBB), and severe cardiac failure, cardiac resynchronization therapy (CRT) has been shown to reverse almost completely left ventricular (LV) function. These patients thus eligible to be qualified 'hyper-responders' are exclusively recruited in patients with NIDCM. Evaluate proportion of 'hyper-responders' among patients with NIDCM and try to determine their profile before implantation of CRT.

Methods And Results: Consecutive patients with DCM [LV ejection fraction (LVEF) <35%, LV end-diastolic diameter >60 mm], sinus rhythm, LBBB, and New York Heart Association (NYHA) class III and IV implanted with a CRT were prospectively followed. Patients were considered 'hyper-responders' if they fulfilled after a minimum period of 6 months the following criteria: functional recovery (NYHA class I or II) and LVEF >or=50%. Among the 51 NIDCM patients, 11 (21.5%) were 'hyper-responders' following CRT (LVEF increased from 26 +/- 9 to 59 +/- 6%, P < 0.01). In the 40 (78.5%) remaining patients, there was no or minimal functional improvement and only a modest increase in LVEF from 21 +/- 9 to 26 +/- 12% (P = 0.03). Comparison between 'hyper-responders' and remaining patients showed that baseline parameters of 'hyper-responders' were less severely deteriorated.

Conclusion: In a significant subset of patients with CRT for NIDCM, a 'complete' functional recovery associated with normalization of LV function was observed. This observation suggests that LBBB could be the causative factor of DCM in this subgroup of patients. There was not a unique discriminating factor at baseline between 'hyper-responders' and remaining patients.