Arrhythmogenic mechanisms for the sudden death in heart failure

Introduction Heart failure （HF） is a major clinical manifestation of many cardiac disease processes when the cardiovascular compensatory mechanisms fail. Five million patients suffer from HF with an additional 555,000 new patients diagnosed HF annually. Moreover, there are an estimated 400,000 to 460,000 deaths attributable to sudden cardiac death （SCD） in the United States each year.1 Mortality in the heart failure population is about six to seven times higher than that of the agematched general population.

Reversal of pulmonary vein remodeling after catheter ablation of atrial fibrillation

Background Pulmonary veins （PV） and the atria undergo electrical and structural remodeling in atrial fibrillation （AF）. This study aimed to determine PV and left atrial （LA） reverse remodeling after catheter ablation for AF assessed by chest computed tomography （CT）. Methods PV electrophysiologic studies and catheter ablation were performed in 63 patients （68% male; mean ± SD age： 56 ± 10 years） with symptomatic AF （49% paroxysmal, 51% persistent）. Chest CT was performed before and 3 months after catheter ablation. Results At baseline, patients with persistent AF had a greater LA volume （91 ±29 cm3 vs. 66 ± 27 cm3; P = 0.003） and mean PV ostial area （241 ＋ 43 mm2 vs. 212 ± 47 mm2; P = 0.03） than patients with paroxysmal AF. There was no significant correlation between the effective refractory period and the area of the left superior PV ostium. At 3 months of follow-up after ablation, 48 patients （76%） were AF free on or off antiarrhythmic drugs. There was a significant reduction in LA volume （77 ±31 cm3 to 70 ± 28 cm3; P 〈 0.001） and mean PV ostial area （224 ± 48 mm2 to 182 ± 43 mm2; P 〈 0.001）. Patients with persistent AF had more reduction in LA volume （11.8 ± 12.8 cm3 vs. 4.0 ± 11.2 cm3; P = 0.04） and PV ostial area （62 mm2 vs. 34 mm2; P = 0.04） than those who have paroxysmal AF. The reduction of the averaged PV ostial area was significantly correlated with the reduction of LA volume （r = 0.38, P = 0.03）. Conclusions Catheter ablation of AF improves structural remodeling ofPV ostia and left atrium. This finding is more apparent in patients with persistent AF treated by catheter ablation.

Comparative outcomes of subcutaneous and transvenous cardioverter-defibrillators

Background: The comparative outcomes of subcutaneous implantable cardioverter-defibrillator (S-ICD) and transvenous (T-ICD) have not been well studied. The aim of this study was to evaluate the safety and efficacy of currently available S-ICD and T-ICD. Methods: The study included 86 patients who received an S-ICD and 1:1 matched to those who received single-chamber T-ICD by gender, age, diagnosis, left ventricular ejection fraction (LVEF), and implant year. The clinical outcomes and implant complications were compared between the two groups. Results: The mean age of the 172 patients was 45 years, and 129 (75%) were male. The most common cardiac condition was hypertrophic cardiomyopathy (HCM, 37.8%). The mean LVEF was 50%. At a mean follow-up of 23 months, the appropriate and inappropriate ICD therapy rate were 1.2% vs. 4.7%(X^2= 1.854, P=0.368) and 9.3% vs. 3.5%(X^2 = 2.428, P = 0.211) in S-ICD and T-ICD groups respectively. There were no significant differences in device-related major and minor complications between the two groups (7.0% vs. 3.5%, X^2 = 1.055, P = 0.496). The S-ICD group had higher T-wave oversensing than T-ICD group (9.3% vs. 0%, X^2 = 8.390, P=0.007). Sixty-five patients had HCM (32 in S-ICD and 33 in T-ICD). The incidence of major complications was not significantly different between the two groups. Conclusions: The efficacy of an S-ICD is comparable to that of T-ICD, especially in a dominantly HCM patient population. The S-ICD is assodated with fewer major complications demanding reoperation.

Left ventricular 12 segmental strain imaging predicts response to cardiac resynchronization therapy

Background The number of non-responders to cardiac resynchronization therapy （CRT） exposes the need for better patient selection criteria for CRT. This study aimed to identify echocardiographic parameters that would predict the response to CRT. Methods Forty-five consecutive patients receiving CRT-D implantation for heart failure （HF） were included in this prospective study. New York Heart Association （NYHA） class, 6-minute walk distance, electrograph character, and multi echocardiographic parameters, especially in strain patterns, were measured and compared before and six months after CRT in the responder and non-responder groups. Response to CRT was defined as a decrease in left ventricular end- systolic volume （LVESV） of 15% or more at 6-month follow up. Results Twenty-two （48.9%） patients demonstrated a response to CRT at 6-month follow-up. Significant improvement in NYHA class （P 〈0.01）, left ventdcular end-diastolic volume （LVEDV） （P 〈0.01）, and 6-minute walk distance （P 〈0.01） was shown in this group. Although there was an interventricular mechanical delay determined by the difference between left and right ventricular pre-ejection intervals （（42.87±19.64） ms vs. （29.43±18.19） ms, P=0.02）, the standard deviation of time to peak myocardial strain among 12 basal, mid and apical segments （Tε-SD） （（119.97±43.32） ms vs. （86.62±36.86） ms, P=0.01） and the non-ischemic etiology （P=0.03） were significantly higher in responders than non-responders, only the Tε- SD （OR=1.02, 95% CI=1.01-1.04, P=0.02） proved to be a favorable predictor of CRT response after multivariate Logistic regression analysis. Conclusion The left ventricular 12 segmental strain imaging is a promising echocardiographic parameter for predicting CRT response.

Current concepts and management of atrial fibrillation： the American perspective

Atrial fibrillation （AF） is the most common sustained .cardiac arrhythmia encountered in clinical practice.Its prevalence increases with age, ranging from less than l% of persons younger than 50 years to nearly 10% of those older than 80 years.1＇2 In view of the rapidly aging US population, as well as the increase in the age-adjusted incidence olAF,3 this sustained arrhythmia is fast becoming a disease of epidemic proportions. It is projected that more than 5.6 million Americans will have AF by the year 2050, with more than half of affected individuals aged 80 years and older.2 The cost of treating AF in the US, including the 350 000 hospitalizations, 5 million office visits,