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%) 866 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.