心脏再同步化治疗中应用同步双心室激动与优化心室间延迟的随机比较:RHYTHM II ICD(再同步化用于心力衰竭血流动力学治疗II埋藏式心脏复律除颤器)研究

Background: The clinical value of interventricular(V-V) delay optimization in patients with chronic congestive heart failure(CHF) undergoing implantation of a device for cardiac resynchronization therapy(CRT) has not been clearly demonstrated. Methods: RHYTHM II was a single-blind randomized trial including 121 recipients of a device for CRT with cardioverter/defibrillator capabilities(CRT-D) randomly assigned in a 1∶3 ratio to simultaneous(n=30) versus optimized(OPT)(n=91) biventricular pacing. V-V delay was optimized by echocardiography. The study end points were(1) freedom from CRT-D system-related complications and(2) changes between preimplant and 6 months of follow-up in(a) New York Heart Association CHF functional class,(b) distance covered during a 6-minute hall walk, and(c) quality of life(QOL). Results: In the OPT group, the V-V delay ranged from 0 to 80 milliseconds, with 28.4%of patients stimulated at an OPT V-V delay of 0 milliseconds. The overall 6-month survival free of adverse events requiring invasive interventions was 81.8%. In the whole cohort, 6 months of CRT-D was associated with a significant decrease in New York Heart Association class, increase in the distance covered during the 6-minute hall walk, and improvement in QOL(each P< .0001). The effects of CRT-D on these end points were similar in both study groups. Conclusions: Cardioverter-defibrillator capabilities was associated with a significant alleviation of CHF symptoms, increase in functional capacity, and improvement in QOL. The optimization of the V-V delay conferred no additional benefit compared with simultaneous biventricular stimulation.

心脏再同步化治疗中的心电重构

Background: More information is required on the relationship between electrical and structural reverse remodeling in patients treated with cardiac resynchronization theraphy. Methods: QRS and JT intervals were investigated during different pacing modes before and 3 months after implantation of a device for biventricular(BiV) pacing in 20 patients with severe drug refractory heart failure(with left ventricular ejection fraction< 40% and QRS >120 ms); structural remodeling was evaluated by echocardiography. Results: QRS interval was significantly shortened by BiV pacing both acutely(p=0.002) and at 3 months(p=0.007). No significant change was found in the JT interval. The extent of QRS shortening obtained by BiV pacing showed moderate correlations with the reduction of end-systolic and end-diastolic volumes(r=0.53, p=0.016 and r=0.45, p=0.045, respectively) as well as with increase of left ventricular ejection fraction(r=0.49, p=0.028) at 3 months. The widening of QRS observed during right ventricular(RV)pacing was greater after 3 months of BiV pacing(with respect to acute assessments), suggesting accentuation of pacing-induced electrical dyssynchrony after a period of pacing-induced resynchronization. Conclusion: The extent of QRS shortening induced by BiV pacing appears to correlate with the reverse structural remodeling(in terms of reduction in end-systolic volume). The acute changes and the remodeling process occurring at mid-term in the overall population of CRT-treated patients do not appear to involve the JT interval. A period of pacing-induced resynchronization appears to accentuate the potential for RV pacing-driven electrical dyssynchrony.

慢-快综合征患者房性快速性心律失常负荷的时间变异性

therapies for atrial tachyarrhythmias(ATs) by measuring the cumulative time(burden) the patient spends in arrhythmia. Contradictory results questioned either therapy efficacy or statistical power of the trials. We studied AT burden variability in patients paced for sinus node disease(SND) in order to interpret currently published data appropriately and to evaluate reliable sample sizes. Methods and results: One hundred and five patients with AT and SND received a dual chamber pacemaker with antitachyarrhythmia- pacing capability, and were followed for 13 months. Seventy- eight patients(74% ) suffered AT recurrences. Device- gathered diagnostic measures were used to simulate results of randomized studies both with crossover and parallel design. The sample size required for statistically significant results was calculated as a function of the expected therapy- induced burden reduction. AT burden intra- patient variability was high: 43% of patients showed intrinsic fluctuations hiding any therapy- induced burden reduction lower than 30% . Demonstrating therapeutic breakthrough through a 6 month study would require 290 patients with crossover design and 5800 patients with parallel design. Doubling the study period requires 400 and 3000 patients, respectively. Conclusion: Patients with AT and paced for SND showed high intra- patient burden variability, which could possibly hide an AT burden reduction induced by a therapy. Previous studies involving non- pharmacological therapies utilizing AT burden end- points could lack the power to reach statistical significance.