Incidence of left ventricular function improvement after primary prevention ICD implantation for non-ischaemic dilated cardiomyopathy: a multicentre experience.

Background: The SCD-HeFT study demonstrated a benefit of primary prevention implantable cardioverter-defibrillator (ICD) implantation in patients with non-ischaemic dilated cardiomyopathy (NIDCM). However, NIDCM may improve spontaneously, even after waiting 6-9 months on optimal medical treatment.

Objective: To assess the incidence of left ventricular (LV) function improvement in patients receiving primary prevention ICDs for NIDCM.

Methods: All patients with NIDCM receiving primary prevention ICDs (non-cardiac resynchronisation therapy) from 2005 to the present at our institutions were retrospectively studied. All patients had NIDCM confirmed by a lack of significant stenoses on coronary angiography, a lack of significant valvular abnormalities on echo, and LV dysfunction with ejection fraction (EF) <35%. All patients had to have had a diagnosis of NIDCM for at least 9 months and be receiving optimal medical treatment for at least 3 months before implant according to the guidelines. All patients had at least New York Heart Association (NYHA) II symptoms. Baseline and follow-up EF was documented by quantitative echo and/or multi-gated acquisition scan.

Results: 332 patients were identified by a database search. Patients were aged 67+/-11 years, 75% of them were male, NYHA 2.3+/-0.7, with EF 25+/-13%, and LV diastolic diameter 61+/-10 mm. Time from initial NIDCM diagnosis to implant was 11+/-6 months and duration of medical treatment before implant was 8+/-5 months. Treatment at the time of implant included ACE inhibitors or ARBs (85%), beta blockers (77%), spironolactone (53%), loop diuretic (63%) and digoxin (50%). Repeat EF assessment was available in 309/332 (93%) 8+/-6 months after implant. EF improved to >35% in 37/309 (12%) patients. Patients who improved had a shorter time from diagnosis to implant (9+/-3 vs 13+/-5 months respectively, p=0.03). No other significant predictors were identified for patients with improved EF.

Conclusions: In spite of following guidelines for implantation of primary prevention ICDs in patients with NIDCM, a substantial number of patients (12%) experience improvement in LV function to levels above those recommended for ICD implant. A shorter time from diagnosis to implant may predict post-implant improvement.