Background: Catheter-based treatment of patients with hypertrophic obstructive cardiomyopathy (HOCM) by alcohol ablation (transcoronary ablation of septal hypertrophy, TASH) leads to symptomatic and haemodynamic improvement. However, little is known regarding the survival and its evolution since the introduction of the method in 1995. Theoretically, the method may be harmful, because widening of the obstructed left ventricular outflow tract is achieved by a septal infarction and subsequently by a potentially arrhythmogenic scar., Objective: This study sought to determine the impact of TASH on the survival of all patients with HOCM treated in our institution between 1995 and 2005., Methods: Survival was assessed from the early beginning in each of 644 consecutive patients to April 2005. Group A comprises a first series of 329 patients who were treated in a dose finding strategy with decreasing amounts of ethanol until December 2001, on average, from 2.9 ml to 0.93 ml/patient. The survival of this group was analysed using Kaplan-Meier estimates, multivariate Cox regression and Log-Rank testing. Group B comprises 315 patients of the following "low alcohol dose era" (mean amount of ethanol 0.8 +/- 0.4 ml, range 0.3-1.5 ml) and their mid-term survival (period to first regular 6-month post-procedural control)., Results: All patients (age 58 +/- 15 years, 99.2% follow up, mean 1.4 years): 33 patients died (5.1% all cause mortality), including perioperative deaths. 14/33 (42%) died from cardiac reasons. Annual total (all cause) mortality was 3.2%, total in-hospital mortality 1.2% in all patients (8 of 644 patients, 6 of them with severe comorbidity) and 0.4% in low risk patients. Annual cardiac mortality after hospital discharge was 0.7% (6 patients, all with sudden death). Group A (age 58 +/- 15 years, 98.8% follow up, mean 2.1 years, maximum 6.2 years): 29 patients died (total annual mortality 4.3%), 10 of them from hypertrophic cardiomyopathy related reasons resulting in a total in-hospital mortality of 1.8% (6 deaths), a cardiac annual mortality of 1.5% (including hospital mortality) and 0.6%/year after hospital discharge. Age was identified as an independent predictor of increased overall mortality (P = 0.002) and lower alcohol dosage and the absence of atrial fibrillation as independent predictors of reduced cardiac mortality (P = 0.005 and P = 0.039, respectively). With focus on the median value of the alcohol quantity (2.0 ml), patients treated with high amounts (>2.0 ml) showed a higher total mortality than patients treated with small amounts (< or =2.0 ml) (P = 0.031) and alcohol turned out to be an independent predictor of survival (P = 0.047). The same holds true for a homogenous subset of 262 patients with respect to cardiac mortality (P = 0.018). Group B (age 57 +/- 14 years, 99.7% follow up, mean 7.3 months): Total in-hospital mortality was 0.6% (2 of 315 patients; P = 0.173, group A/B) and cardiac in-hospital mortality 0% (P = 0.016, group A/B). During follow up two patients died, both of them experienced a sudden death reflecting an annual mortality of 1.0%., Conclusion: These data represent the largest available database on survival after alcohol septal ablation of HOCM from a single centre with large experience, and its evolution over 10 years with increasing procedural experience including the pronounced reduction of ethanol quantity in a systematic doses finding strategy. The in-hospital mortality has become very low. Cardiac survival during follow up was excellent, however, the well-known risk of sudden death is not completely eliminated. Longer follow-up time would be desirable for definite evaluation of this relatively new therapeutic option in the management of HOCM.