The rationale behind ventricular resynchronization.

Biventricular pacing or cardiac resynchronization therapy was first proposed in 1994 as a form of non-pharmacological therapy in patients with heart failure and intraventricular and atrioventricular conduction delay, refractory to medical therapy. In this group of patients the presence of ventricular dyssynchrony is associated with progressive adverse remodeling and worsening of systolic and diastolic performance and carries independent prognostic significance. Acute clinical studies have demonstrated hemodynamic benefit as well as improved systolic and diastolic ventricular performance. Also, most clinical short- and medium-term studies have shown clinical and hemodynamic improvement associated with reverse ventricular remodeling. It has recently been demonstrated that cardiac resynchronization therapy reduces morbidity and mortality. This paper analyzes the pathophysiology of abnormal electrical conduction and the acute and chronic response to cardiac resynchronization, and reviews the most relevant aspects of the various trials.     

心脏再同步治疗与室性心律失常

心脏再同步治疗(CRT)是慢性心力衰竭治疗的重要进展,大量临床研究证实,对于符合适应证的慢性心力衰竭患者,CRT能够逆转心肌重构,改善心功能,提高生活质量,降低死亡率[1-4].     

Pathobiology of left ventricular dyssynchrony and resynchronization

Left ventricular mechanical dyssynchrony has recently been recognized as a significant contributor to increased morbidity and mortality in some patients with congestive heart failure. Ventricular dyssynchrony compromises global cardiac mechanical efficiency, induces changes in regional hypertrophy and blood flow, and results in local alterations in myocardial protein expression. Cardiac resynchronization therapy has both immediate and long-term beneficial effects on global cardiac function, and has been shown to reduce both morbidity and mortality in heart failure patients. The effects of resynchronization on the tissue-level and molecular consequences of dyssynchrony remain unknown.     

Right ventricular function following cardiac resynchronization therapy

The effect of cardiac resynchronization therapy (CRT) on right ventricular (RV) function has not been well described. The purpose of this study was to use tissue Doppler imaging to assess changes in RV function after CRT. Thirty-five patients with heart failure (age 65 +/- 10 years; 26 men) who underwent color tissue Doppler imaging of the right ventricle both immediately before CRT and >3 months (mean 6 +/- 3) after were studied. Myocardial systolic velocity was measured at the tricuspid annulus and basal and midventricular segments of the right ventricle free wall and averaged to obtain a measure of global RV function (RV S(m)). Left ventricular ejection fraction was also measured using biplane Simpson's method before and after CRT. RV S(m) significantly improved after CRT (5.4 +/- 1.9 to 7.1 +/- 2.6 cm/s; p <0.001), as did left ventricular ejection fraction (26 +/- 6% to 34 +/- 10%; p <0.001). Twenty-one of 35 patients (60%) showed an increase in RV S(m) > or =1 cm/s, with an increase > or =2 cm/s in 13 of those patients (37%). Improvement was seen in both ischemic and nonischemic patients and was independent of improvement in left ventricular ejection fraction and baseline left ventricular dyssynchrony. In conclusion, CRT resulted in improved RV function measured as RV S(m). CRT had beneficial effects on RV function independent of improvement in left ventricular ejection fraction.     

Cardiac resynchronization therapy and ventricular tachyarrhythmia burden

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心脏再同步治疗中的左心室电极导线位置

经过电生理工作者多年的艰辛探索与不懈努力,在Haissaguerre等[1]的具有里程碑式的发现基础上,肺静脉兴奋灶触发的阵发性心房颤动(房颤)导管消融模式已逐渐趋于成熟.从最初的点状消融,到节段性肺静脉隔离,以致近年来世界多数心脏中心认可并采用的主流消融术式之一的环肺静脉口外线性消融,其治疗成功率逐步提高.     

Left ventricular dyssynchrony predicts right ventricular remodeling after cardiac resynchronization therapy.

OBJECTIVES: The purpose of this research was to evaluate right ventricular (RV) remodeling after six months of cardiac resynchronization therapy (CRT). BACKGROUND: Cardiac resynchronization therapy is beneficial in patients with end-stage heart failure. The effect of CRT on RV size is currently unknown. Accordingly, the effects of CRT on RV size, severity of tricuspid regurgitation, and pulmonary artery pressure were evaluated. METHODS: Fifty-six consecutive patients with end-stage heart failure (52% ischemic cardiomyopathy), left ventricular (LV) ejection fraction (EF) < or =35%, QRS duration >120 ms, and left bundle branch block were included. Clinical parameters, LV volumes, LVEF, LV dyssynchrony, and RV chamber size were assessed at baseline and after six months of CRT; LV dyssynchrony was assessed using tissue Doppler imaging. RESULTS: Clinical parameters improved significantly; LV dyssynchrony was acutely reduced after CRT and remained unchanged at six-month follow-up. Left ventricular EF improved significantly from 19 +/- 6% to 26 +/- 8% (p < 0.001), and LV end-diastolic volume decreased from 257 +/- 98 ml to 227 +/- 86 ml (p < 0.001). Right ventricular annulus decreased significantly from 37 +/- 9 mm to 32 +/- 10 mm, RV short-axis from 29 +/- 11 mm to 26 +/- 7 mm, and RV long-axis from 89 +/- 11 mm to 82 +/- 10 mm (all p < 0.001). Left ventricular and RV reverse remodeling were only observed in patients with substantial LV dyssynchrony at baseline. Finally, significant reductions in severity of tricuspid regurgitation and pulmonary artery pressure were observed. CONCLUSIONS: Cardiac resynchronization therapy results in significant reverse LV and RV remodeling after six months of CRT in patients with LV dyssynchrony. Moreover, CRT leads to a reduction of the severity of tricuspid regurgitation and a decrease in pulmonary artery pressure.     

Effects of cardiac resynchronization therapy on ventricular remodeling

Remodeling reflects the structural and functional deterioration that occurs in heart failure. Indices of remodeling constitute an important marker of the severity of heart failure, and reverse remodeling is an accepted goal in the treatment of heart failure. Cardiac resynchronization therapy (CRT) has been shown to reverse the remodeling process by improving ventricular size, shape, and mass and reducing mitral regurgitation in the short and long term. Diastolic function, right ventricular size, and atria exhibit reverse remodeling. Trials of medical therapy for heart failure strongly link remodeling indices with outcomes, and emerging data suggest that remodeling indices may be among the most accurate predictors of long-term morbidity and mortality in heart failure patients with CRT devices. This review discusses remodeling and focuses on the evidence for CRT-induced reverse remodeling.     

Predictors of sustained ventricular arrhythmias in cardiac resynchronization therapy

Background- Patients undergoing cardiac resynchronization therapy (CRT) are at high risk for ventricular arrhythmias (VAs), and risk stratification in this population remains poor. Methods and Results- This study followed 269 patients (left ventricular ejection fraction <35%; QRS >120 ms; New York Heart Association class III/IV) undergoing CRT with a defibrillator for 553±464 days after CRT with defibrillator implantation to assess for independent predictors of appropriate device therapy for VAs. Baseline medication use, medical comorbidities, and echocardiographic parameters were considered. The 4-year incidence of appropriate device therapy was 36%. A Cox proportional hazard model identified left ventricular end-systolic diameter >61 mm as an independent predictor in the entire population (hazard ratio [HR], 2.66; P=0.001). Those with left ventricular end-systolic diameter >61 mm had a 51% 3-year incidence of VA compared with a 26% incidence among those with a less dilated ventricle (P=0.001). Among patients with left ventricular end-systolic diameter ≤61 mm, multivariate predictors of appropriate therapy were absence of β-blocker therapy (HR, 6.34; P<0.001), left ventricular ejection fraction <20% (HR, 4.22; P<0.001), and history of sustained VA (HR, 2.97; P=0.013). Early (<180 days after implant) shock therapy was found to be a robust predictor of hospitalization for heart failure (HR, 3.41; P<0.004) and mortality (HR, 5.16; P<0.001.) Conclusions- Among patients with CRT and a defibrillator, left ventricular end-systolic diameter >61 mm is a powerful predictor of VAs, and further risk stratification of those with less dilated ventricles can be achieved based on assessment of ejection fraction, history of sustained VA, and absence of β-blocker therapy.     

心脏再同步治疗后心室电重构和室性心律失常与左心室逆重构关系探讨

目的 探讨慢性心力衰竭患者心脏再同步治疗（CRT）后心室电重构和室性心律失常与左心室逆重构的关系.方法 入选因心力衰竭于我院行CRT的患者,随访术后即刻与术后6个月体表心电图与超声心动图,记录术后6个月期间窒性心律失常发作次数.根据术后6个月左心室收缩末容积缩小比例（ ΔLVESV）≥15％与否分为有效组与无效组,对比组间QRS时限变化（ΔQRSd）和室性心律失常事件,对左心室逆重构程度与ΔQRSd和室性心律失常事件进行相关性分析,寻找CRT治疗后室性心律失常的预测因素.结果 共入选43例患者,有效组29例,无效组14例,组间基线资料与术后应用药物等差异无统计学意义.全部患者CRT后6个月QRSd无变化（P=0.50）,有效组QRSd明显缩短（P＜0.01）,无效组无变化（P=0.08）.组间ΔQRSd差异有统计学意义（P=0.02）.全部患者CRT后ΔLVESV与△QRSd呈正相关（r=0.523,P＜0.01）.CRT 6个月内室性早搏（PVCs）与室性早搏连发（PVCruns）次数分析显示,log（PVCs）与log（PVC runs）在组间差异有统计学意义（P＜0.01）,log （PVCs）和log.（PVC runs）均与ΔLVESV呈正相关（P＜0.01）.多元回归分析显示,ΔLVESV是log （PVCs）的独立预测因素（β=2.36,P＜0.01）,ΔLVESV和男性是log（ PVC runs）的独立预测因素（β=2.88,P＜0.01;β=-0.74,P=0.03）.结论 CRT后左心室逆重构与电重构及室性心律失常发生减少相关.左心室逆重构程度及性别对CRT患者术后室性心律失常事件有预测意义.     

Importance of left ventricular lead position in cardiac resynchronization therapy

At present, cardiac resynchronization therapy (CRT) is considereda major breakthrough in the treatment of patients with drug-refractoryheart failure. The startling benefits of CRT observed in smallinitial studies have now been clearly confirmed in large randomizedcontrolled multicentre trials which have now included over 4000patients.^1,2 The beneficial effects of CRT observed in thesetrials include an improvement in clinical symptoms as well asan improvement in left ventricular (LV) haemodynamics and areduction in LV volumes. In addition, CRT resulted in a dramaticreduction in heart failure related hospitalizations and a reductionin all-cause mortality. On the     

Symptomatic relief: left ventricular assist devices versus resynchronization therapy

In patients who have end-stage heart failure, medical therapy is of limited use, and heart transplantation is frequently not an option because of the shortage of donor hearts. Two new treatment options, left ventricular assist devices (LVADs) and implantable cardiac resynchronization therapy (CRT) devices, can improve survival and quality of life in patients who have heart failure. Both types of devices are easy to implant. However, LVADs carry the risk of infection and mechanical failure, and CRT is ineffective in a substantial proportion of patients who have heart failure. Therefore, methods must be devised to identify patients who have heart failure who are likely to benefit from these devices. Data suggest that early LVAD implantation, before end-stage heart failure develops, is critical to slowing or reversing disease progression. Similarly, in indicated patients who have less advanced disease, CRT may be particularly beneficial.     

Cardiac resynchronization therapy: an updateimpaired left ventricular systolic function

Cardiac resynchronization therapy has been shown to reduce hospitalization and mortality, and to improve heart failure symptoms, in patients with systolic dysfunction and ventricular dyssynchrony. We review the current guidelines for cardiac resynchronization therapy, the underlying evidence, the latest developments in the field and directions of future research.     

Effect of left ventricular remodeling after cardiac resynchronization therapy on frequency of ventricular arrhythmias

We evaluated whether cardiac resynchronization therapy affects the prevalence of ventricular tachycardia in relation to reverse remodeling in patients with end-stage heart failure. Clinical, echocardiographic, and implantable cardioverter-defibrillator (ICD) data of 17 patients with ICDs were obtained before and after they had received an upgrade to an ICD-cardiac resynchronization therapy device.