Resting muscle sympathetic nerve activity and peak oxygen uptake in heart failure and normal subjects.

AIMS: Exercise intolerance and increased efferent vasoconstrictor traffic to muscle are two characteristics of heart failure that have not been explicitly linked. We tested the hypothesis that peak oxygen consumption is inversely related to resting muscle sympathetic nerve activity in heart failure. METHODS AND RESULTS: We recorded peroneal muscle sympathetic nerve activity in 17 treated heart failure patients (16 men,1 woman; mean ejection fraction of 26. 0+/-3.2% (SE)) and 17 age-matched healthy subjects (16 men, 1 woman). Oxygen consumption was measured during cycle ergometry to maximal effort. In heart failure and normal subjects, mean peak oxygen consumption was 20.6+/-1.7 vs 32.2+/-2.6 ml x kg-1 x min-1(P<0.0001) and mean muscle sympathetic activity was 49.3+/-2.8 vs 33.0+/-3.3 bursts x min-1(P<.0007) respectively. When age was accounted for by multiple regression analysis, there was a significant relationship between peak oxygen consumption and burst frequency in heart failure (P<0.02) but not in healthy subjects. The percent of predicted peak oxygen consumption achieved (based on age, sex and body size) was inversely related to muscle sympathetic nerve burst frequency in heart failure (r=-0.71, P<0.0014) but not in normal subjects (r=-0. 44, P<0.08;P<0.0001 for this comparison). CONCLUSION: Reduced exercise capacity in heart failure is related to increased efferent sympathetic traffic to calf muscle. These observations are consistent with the concept of a peripheral neurogenic limit to exercise in heart failure.     

Moderate exercise training improves functional capacity, quality of life, and endothelium-dependent vasodilation in chronic heart failure patients with implantable cardioverter defibrillators and cardiac resynchronization therapy.

BACKGROUND: The objective of this study was to determine the effects of a moderate exercise training program on functional capacity, quality of life, and hospital readmission rate in chronic heart failure patients with implantable cardioverter defibrillators and cardiac resynchronization therapy. METHODS AND RESULTS: We studied 52 men (mean age 55+/-10 years, ejection fraction 31+/-7%) in chronic heart failure II (n=29) and III (n=23) NYHA functional class with ischemic cardiomyopathy who received implantable cardioverter defibrillators with or without cardiac resynchronization therapy. Patients were randomized into two groups. Group T (n=30 patients, 15 implantable cardioverter defibrillator, 15 implantable cardioverter defibrillator+cardiac resynchronization therapy) underwent a supervised exercise training program at 60% of peak VO2 three times a week for 8 weeks. Group C (n=22 patients, 12 implantable cardioverter defibrillator, 10 implantable cardioverter defibrillator+cardiac resynchronization therapy) avoided physical training. At 8 weeks, only trained patients had improvements in peak VO2 (P<0.01 versus C), endothelium-dependent dilatation of the brachial artery (P<0.001 versus C) and quality of life (P<0.001 versus C). Among trained patients, those with cardiac resynchronization therapy had greater improvements in peak VO2 and quality of life. During the follow-up (24+/-6 months), eight controls had sustained ventricular tachycardia requiring hospital readmission, while no trained patients had adverse events (log rank 8.56; P<0.001). The improvement in peak VO2 was correlated with the improvement in endothelium-dependent dilatation (r=0.65). CONCLUSION: Moderate exercise training is safe and has beneficial effects after implantable cardioverter defibrillator implantation, especially when cardiac resynchronization therapy is present. These effects are associated with improvement in quality of life and outcome.     

Effects of chronic clonidine administration on sympathetic nerve traffic and baroreflex function in heart failure

Congestive heart failure is characterized by a sympathetic activation that is coupled with a baroreflex impairment. Whether these alterations are affected by clonidine is unknown. In 26 normotensive patients age 58.0+/-1.1 years (mean+/-SEM) affected by congestive heart failure (New York Heart Association functional class II or III) and treated with furosemide and enalapril, we measured mean arterial pressure, heart rate, venous plasma norepinephrine, and muscle sympathetic nerve traffic (microneurography) at rest and during baroreceptor stimulation and deactivation caused by stepwise intravenous infusions of phenylephrine and nitroprusside, respectively. Measurements were repeated after a 2-month administration of transdermal clonidine patch (14 patients) or placebo (12 patients) according to a double-blind, randomized sequence. Clonidine caused a slight, nonsignificant reduction in mean arterial pressure and heart rate without affecting exercise capacity and echocardiographically determined left ventricular ejection fraction. In contrast, both plasma norepinephrine and sympathetic nerve traffic were significantly reduced (-46.8% and -26.7%, respectively; P<0.01 for both). This reduction was coupled with no change in cardiac and sympathetic baroreflex responses. Transdermal placebo administration for a 2-month period did not affect any of the above-mentioned variables. Thus, in congestive heart failure patients who are undergoing conventional drug treatment, chronic clonidine administration exerts marked sympathoinhibitory effects without adversely affecting cardiac functions and clinical state. Whether this leads to further therapeutic benefits remains to be tested.     

Cardiac resynchronization therapy for the management of chronic heart failure

While numerous pathophysiologic mechanisms may lead to the onset and progression of chronic systolic heart failure, a variety of electrophysiologic abnormalities seen in the setting of chronic left ventricular dysfunction may also contribute to the natural history of the disease. Atrial, atrial-ventricular, and inter- and intraventricular conduction disturbances may place the failing ventricle at a further mechanical disadvantage, thus contributing to the functional impairment and poor outcomes associated with chronic heart failure. In the early 1990s, attempts at treating patients with end-stage systolic heart failure using conventional pacing strategies met with equivocal results. However, this work did provide further insight into the electromechanical consequences of advanced heart failure and suggested that atrial-synchronized biventricular pacing, or cardiac resynchronization therapy, might provide better and more consistent symptomatic and hemodynamic improvement. Several landmark clinical trials have evaluated the safety and efficacy of cardiac resynchronization therapy in New York Heart Association (NYHA) class III and IV heart failure. These studies have consistently shown statistically significant improvements in quality of life, NYHA functional class ranking, exercise tolerance, and left ventricular reverse remodeling. Some studies have suggested reductions in morbidity and mortality. This latter observation has been confirmed by a recent large-scale outcomes study. Thus, cardiac resynchronization therapy should be routinely considered in eligible NYHA class III and IV heart failure patients with ventricular dyssynchrony.     

Long-term follow-up of cardiac resynchronization therapy in patients with end-stage heart failure

Long-term follow-up of cardiac resynchronization therapy. INTRODUCTION: Cardiac resynchronization therapy (CRT) has been introduced to treat patients with end-stage heart failure, and results of this technique are promising. The aim of our study was to assess the sustained benefit of CRT in a large patient cohort with end-stage heart failure at long-term follow-up. In addition, the prognosis of responders and nonresponders was evaluated. METHODS AND RESULTS: 125 patients with end-stage heart failure, NYHA class III or IV, LVEF<35%, QRS duration>120 msec and left bundle branch block morphology received a biventricular device. At baseline and 6 months after implantation the following parameters were evaluated: NYHA class, Minnesota Quality of life score, QRS duration on surface ECG, 6-minute walking distance and LVEF. Follow-up was obtained up to 3 years. After 6 months, patients were divided in clinical responders and nonresponders according to improvement in NYHA class. All clinical parameters improved significantly at 6-month follow-up. Hospitalization for heart failure was 3.8+/-4.9 days/year before and 0.7+/-1.6 days/year after CRT. Survival at 1-, 2-, and 3-year follow-up was 93%, 88%, and 85%, respectively. Responders (78%) showed a significantly better survival than nonresponders at 2- and 3-year follow-up (96% and 93% for responders versus 81% and 73% for nonresponders, P<0.05). CONCLUSION: The improvement in functional status and symptoms after CRT is maintained at long-term follow-up (up to 3 years). The clinical improvement was associated with a significant reduction in hospitalization rate which was also maintained over the years. Preimplantation selection of responders may result in even better long-term survival.     

Effect of cardiac resynchronization therapy in the treatment of chronic heart failure

As a result of cardiac resynchronization therapy in all 10 patients with chronic NYHA class III-IV heart failure at duration of observation from 2 to 20 months was noted positive dynamics: improvement of self feeling, increase of 6 min walking distance, decrease of heart failure class, and improvement of functional parameters of the heart according to echocardiography data. Implantation of biventricular cardiac pacemaker to patients with chronic heart failure is relatively safe and accomplish-able from technical point of view. Cardiac resynchronization in patients with pronounced chronic heart failure appears to be an effective supplementation of drug therapy.     

Effect of biventricular pacing on heart rate variability in patients with chronic heart failure

BACKGROUND: Biventricular pacing is emerging as a long-term therapy for symptomatic heart failure. Analysis of heart rate variability (HRV) has become an important predictive tool in this syndrome. AIM OF THE STUDY: To assess whether chronic resynchronization therapy can affect HRV in patients with heart failure. METHODS AND RESULTS: Thirteen patients with heart failure were studied (mean age+/-1 S.E. 65+/-2.2 years, QRS 195+/-5.3 ms, NYHA class 3.2+/-0.1, LVEF 21+/-1.7%). The protocol included a preliminary no pacing period for 1 month following device implantation. Twenty-four hour Holter ECG recordings were performed at the end of this period (baseline) and after 3 months of biventricular stimulation (VDD mode). Prior to and following pacing patients underwent NYHA class evaluation, 6-min walk test, Quality of Life Assessment and a cardiopulmonary exercise test. Biventricular pacing improved functional class (P<0.0001) and Quality of life (P<0.0001), increased 6-min walk distance, (P=0.008) and exercise duration (P<0.0001) but had no significant effect on peak exercise VO(2). Resynchronization therapy increased mean 24-h RR (922+/-58 vs. 809+/-41 ms at baseline, P=0.006), SDNN (111+/-11 vs. 83+/-8 ms, P=0.003), SDNN-I (56+/-10 vs. 40+/-5 ms, P=0.02), rMSSD (66+/-14 vs. 41+/-8 ms, P=0.003), Total Power (5724+/-1875 vs. 2074+/-553 ms(2), P=0.03), Ultra Low Frequency Power (1969+/-789 vs. 653+/-405 ms(2), P=0.03) and Very Low Frequency Power (2407+/-561 vs. 902+/-155 ms(2), P=0.004). CONCLUSION: Biventricular pacing in heart failure improves autonomic function by increasing HRV. This may have important prognostic implications.     

心脏再同步化治疗晚期扩张型心肌病13例的效果

目的: 观察心脏再同步化治疗（CRT）晚期充血性心力衰竭的临床疗效。方法: 晚期扩张型心肌病患者13例接受CRT,NYHA心功能分级为Ⅲ～Ⅳ级,左室射血分数（LVEF）为（27.4±9.7）%,左室舒张末期内径（LVEDD）为(72.8±9.6)mm,QRS时限为( 137.8＋30.4)ms。术后观察QRS时限的变化,随访左室电极起博阈值、心功能分级、LVEF及LVEDD。结果: 术后QRS时限减少为（123.8±17.1）ms。所有患者随访3～38月,左室电极慢性阈值为（1.1±0.6）V/0.4 ms。与术前相比,NYHA心功能分级从(3.4±0.5)降低为(1.5±0.9); LVEF从(27.4±9.7)%上升至(43.5±18.5)%(P<0.05);LVEDD从(72.8±9.6)mm缩小为(65.5±11.6)mm（P<0.05）。结论: CRT可改善心功能,提高LVEF,并可逆转左心室重构。     

Mechanism of cardiac resynchronization therapy by real-time three-dimensional echocardiography in patients with heart failure

We report the case of a 66-year-old man with heart failure NYHA class IV treated with biventricular pacing for cardiac resynchronization. The patient was evaluated by real-time three-dimensional transthoracic echocardiography before and 48 hours after pacemaker implantation. The use of three-dimensional echocardiography contributed to understanding the underlying mechanism involved in cardiac resynchronization therapy by demonstrating enhanced synchrony of myocardial segments, which resulted in the patient's clinical improvement.     

双心室再同步起搏治疗宽QRS慢性心力衰竭患者的长期疗效及病死率分析

目的观察双心室同步起搏治疗慢性心力衰竭(心衰)患者的长期疗效及死亡率.方法 2001年3月至2005年2月住院患者25例,男18例,女7例,年龄34～75(61.42±10.36)岁;其中扩张性心肌病16例,高血压性心脏病3例,缺血性心肌病6例,心功能NYHA分级Ⅲ级10例、Ⅳ级15例.所有患者左室舒张末期内径(LVEDD)>60 mm,左室射血分数(LVEF)<0.40,QRS>130 ms.观察术前及术后3个月、6个月、1年、2年、3年的心功能各项参数及死亡率,平均随访时间为(20.88±11.51)个月.结果 (1)死亡率死亡5例,非心原性死亡3例,心原性猝死1例,急性心肌梗死1例.(2)术后3个月至3年,平均6 min步行距离明显增加(P<0.01).(3)NYHA心功能分级,术后3个月至3年,心功能明显改善(P<0.01),平均心功能降低1级以上.(4)LVEDD术后3个月至3年,LVEDD明显减小(P<0.05～P<0.01).(5)LVEF术后3个月至2年,LVEF明显增加(P<0.05～P<0.01);术后第3年 ,LVEF也改善,但差异无统计学意义.结论双心室同步起搏治疗宽QRS慢性心衰能明显改善患者的生活质量及心功能,减少LVEDD,逆转左室重构,长期治疗疗效巩固,并能降低心衰导致的病死率.     

Combined therapy with carvedilol and amiodarone is more effective in improving cardiac symptoms, function, and sympathetic nerve activity in patients with dilated cardiomyopathy: comparison with carvedilol therapy alone.

BACKGROUND: Carvedilol therapy has been reported to be more effective than other beta-blockers in patients with chronic heart failure (CHF). Amiodarone is an anti-arrhythmic medicine that has also been reported to be effective in patients with CHF. But the usefulness of combined therapy with carvedilol and amiodarone has not been reported. METHODS: We compared 15 patients (M/F = 3/12, age = 57 +/- 8 y) with dilated cardiomyopathy (DCM) receiving carvedilol and amiodarone with 15 patients (M/F = 3/12, age = 61 +/- 9 y) receiving carvedilol alone. Patients were studied before and after 1 year of treatment (1Y). NYHA class and exercise capacity based on the specific-activity-scale (SAS), were assessed. Cardiac sympathetic nerve activity was estimated using total defect score (TDS), H/M ratio and washout rate (WR) of 123I-MIBG imaging. Cardiac function was evaluated using 99mTc-MIBI QGS. RESULTS: Combined therapy improved several parameters much more than carvedilol alone (p < 0.05) including delta-TDS (15.0 +/- 8.6 vs. 7.6 +/- 7.2) and delta-WR (15.9 +/- 11.0% vs. 7.3 +/- 10.0%) for 123I-MIBG imaging, delta-LVEF (26.1 +/- 11.4% vs. 15.5 +/- 13.8%), delta-end-systolic volume (100 +/- 63.8 ml vs. 58.9 +/- 47.3 ml), 1Y NYHA class (1.5 +/- 0.5 vs. 1.9 +/- 0.5), 1Y SAS (7.3 +/- 0.7 Mets vs. 6.2 +/- 1.0 Mets), and delta-SAS (3.4 +/- 0.8 Mets vs. 2.6 +/- 1.1 Mets). CONCLUSION: Combined therapy with carvedilol and amiodarone is more effective in improving cardiac symptoms, exercise capacity, cardiac function and cardiac sympathetic nerve activity in patients with DCM.     

Cardiac resynchronization therapy for heart failure]

The short-term prognosis of advanced refractory heart failure is extremely poor and closely correlated with progressive left ventricular dysfunction. The identification of the negative effects of conduction delay on cardiac performance, observed in almost 50% of heart failure patients, disclosed a new research field addressing the correction of electrical abnormalities in order to achieve an improvement in myocardial function. Biventricular stimulation, or cardiac resynchronization therapy, corrects the atrioventricular, inter- and intraventricular mechanical asynchrony and, to date, is indicated (class IIA, level of evidence A) for patients with NYHA class III-IV refractory heart failure regardless of its etiology, QRS interval > or = 130 ms, left ventricular end-diastolic diameter > or = 55 mm, and ejection fraction < or = 35%. To date, the completed trials demonstrated in patients undergoing biventricular pacing a significant improvement in left ventricular performance, quality of life and NYHA class with no significant effects on total mortality. The identification of non-responders (approximately 20-30% of the patient population in completed trials) represents an unresolved issue of cardiac resynchronization therapy. Tissue Doppler imaging evaluation of left ventricular dyssynchrony, which is being addressed by non-randomized prospective studies, should drastically decrease the percentage of these patients.     

Biventricular pacing as a treatment for advanced heart failure. Preliminary experience in a series of 22 consecutive patients

BACKGROUND AND OBJECTIVES: Recent data suggest that biventricular pacing may play an important role in treating advanced heart failure in the presence of a significant interventricular and/or intraventricular conduction disorder by correcting cardiac dysynchrony. In this article, we review the initial technical and clinical experience with cardiac resynchronization therapy in an electrophysiology laboratory. METHODS: The first 22 consecutive patients with severe congestive heart failure, ejection fraction < 0.35, NYHA functional class III or IV, and QRS duration > 120 ms who were implanted biventricular pacemakers were studied. Clinical, electrocardiographic, and echocardiographic evaluations were made before and three months after pacemaker implantation. Acute functional capacity testing with peak oxygen uptake was measured during biventricular pacing and during intrinsic rhythm or right ventricular pacing three months after the implantation procedure. RESULTS: The success rate of pacemaker implantation was 95%. Pre-discharge left ventricular pacing was achieved in 91%, with an average pacing threshold of 1.53 (1.04) volts. NYHA functional class improved (p = 0.039) from 3.4 (0.7) to 2.3 (0.78). The rate of hospitalization for heart failure decreased from an average of 3.12 (0.58) three months before the procedure to 1.38 (0.34) three months after the procedure. Peak oxygen uptake was significantly greater (p = 0.028) during biventricular pacing: 14.89 (2.1) ml/min/kg, than during intrinsic rhythm or right ventricular pacing: 12.65 (2.3) ml/min/kg. CONCLUSIONS: Cardiac resynchronization therapy can be performed safely and with a high success rate in the electrophysiology laboratory. Biventricular pacing seems to improve the symptoms of congestive heart failure in patients with evidence of atrioventricular and/or interventricular/intraventricular dysynchrony. An acute benefit in peak oxygen uptake was associated with biventricular pacing after the implantation procedure.     

Left ventricular-based cardiac stimulation post AV nodal ablation evaluation (the PAVE study)

BACKGROUND: Chronic right ventricular pacing has been reported to promote cardiac dyssynchrony. The PAVE trial prospectively compared chronic biventricular pacing to right ventricular pacing in patients undergoing ablation of the AV node for management of atrial fibrillation with rapid ventricular rates. METHODS AND RESULTS: One hundred and eighty-four patients requiring AV node ablation were randomized to receive a biventricular pacing system (n = 103) or a right ventricular pacing system (n = 81). The study endpoints were change in the 6-minute hallway walk test, quality of life, and left ventricular ejection fraction. Patient characteristics were similar (64% male; age: 69 +/- 10 years, ejection fraction: 0.46 +/- 0.16; 83%, NYHA Class II or III). At 6 months postablation, patients treated with cardiac resynchronization had a significant improvement in 6-minute walk distance, (31%) above baseline (82.9 +/- 94.7 m), compared to patients receiving right ventricular pacing, (24%) above baseline (61.2 +/- 90.0 m) (P = 0.04). There were no significant differences in the quality-of-life parameters. At 6 months postablation, the ejection fraction in the biventricular group (0.46 +/- 0.13) was significantly greater in comparison to patients receiving right ventricular pacing (0.41 +/- 0.13, P = 0.03). Patients with an ejection fraction 相似文献   

Baseline characteristics of patients randomized in The Resynchronization Reverses Remodeling In Systolic Left Ventricular Dysfunction (REVERSE) study

The Resynchronization Reverses Remodeling in Systolic Left Ventricular Dysfunction (REVERSE) study is a randomized controlled trial currently assessing the safety and efficacy of cardiac resynchronization therapy in patients with asymptomatic left ventricular (LV) dysfunction with previous symptoms of mild heart failure. This paper describes the baseline characteristics of randomized patients; 610 patients with New York Heart Association (NYHA) class II (82.3%) heart failure or asymptomatic (NYHA class I) LV dysfunction with previous symptoms (17.7%) were randomized in 73 centers. The mean age was 62.5+/-11.0 years, the mean LV ejection fraction was 26.7%+/-7.0%, and the mean LV end-diastolic diameter was 66.9+/-8.9 mm. A total of 97% of patients were taking angiotensin-converting enzyme inhibitors or angiotensin receptor blockers and 95.1% were taking beta-blockers, which were at the target dose in 35.1% of patients. Compared with previous randomized cardiac resynchronization therapy trials, REVERSE patients are on better pharmacologic treatment, are younger, and have a narrower QRS width despite similar LV dysfunction.     

Baroreflex control of renal sympathetic nerve activity is preserved in heart failure despite reduced arterial baroreceptor sensitivity

The purpose of this study was to determine if arterial baroreflex control of sympathetic nerve traffic is impaired in heart failure. We recorded renal nerve activity during changes in arterial pressure while simultaneously recording from aortic baroreceptor afferent fibers in 10 dogs with heart failure induced by rapid ventricular pacing and in 10 sham animals. Sensitivity of the aortic baroreceptors (percent change in nerve activity per millimeters mercury change in mean arterial pressure) was reduced in the heart failure group (heart failure, 2.3 +/- 0.3; sham, 3.6 +/- 0.4, p = 0.02). Despite the reduced sensitivity of aortic baroreceptors in heart failure, there was no difference in the baroreflex gain of renal nerve activity (heart failure, -5.5 +/- 1.4; sham, -5.8 +/- 1.3, p = NS). These values tended to decrease in both groups after vagotomy. The relation between baroreceptor input and renal sympathetic output, or central baroreflex gain (percent change in renal nerve activity divided by percent change in aortic nerve activity) was similar in both groups before vagotomy (heart failure, -2.4 +/- 0.6; sham, -2.3 +/- 0.5, p = NS). Vagotomy reduced central gain in the sham group (-0.9 +/- 0.1, p = 0.03) but not in the heart failure group (-1.7 +/- 0.5, p = NS), suggesting that the contribution of vagal afferents in the baroreflex arc is reduced in heart failure. Baroreflex control of R-R interval was attenuated in heart failure when assessed by blood pressure elevation but not reduction, indicating abnormal parasympathetic but preserved cardiac sympathetic mechanisms in heart failure. Thus, dogs with heart failure exhibit reduced sensitivity of aortic baroreceptors but preserved baroreflex control of renal nerve activity. Reduced baroreceptor sensitivity with preservation of baroreflex control of sympathetic nerve activity may contribute to the sympathoexcitatory state known to exist in heart failure.     

Cardiac resynchronization pacing therapy

Approximately one third of patients with congestive heart failure and systolic dysfunction have an intraventricular conduction delay that is manifested as a QRS duration >120 ms. An intraventricular conduction delay adversely affects ventricular performance by causing dyssynchrony in ventricular activation. When ventricular dyssynchrony is present, simultaneous left and right ventricular pacing or cardiac resynchronization therapy can improve ventricular synchrony. This can lead to an improvement in hemodynamics, ventricular remodeling, mitral regurgitation, exercise capacity and quality of life. Candidates for cardiac resynchronization therapy include patients with advanced congestive heart failure that is refractory to medical therapy, a QRS duration >130 ms, left ventricular ejection fraction <0.35 and sinus rhythm. Because patients who are candidates for biventricular pacing are at high risk of sudden death, they should be considered for implantation of a biventricular pacing device that also provides defibrillation therapy. This paper reviews biventricular pacing for congestive heart failure, including results of acute hemodynamic studies and randomized clinical trials, patient and device selection, and procedural issues.     

Cardiac resynchronization therapy in patients with systolic left ventricular dysfunction and symptoms of mild heart failure secondary to ischemic or nonischemic cardiomyopathy

Cardiac resynchronization therapy (CRT) is beneficial in selected patients with moderate to severe heart failure (New York Heart Association [NYHA] classes III to IV). Patients with mildly symptomatic heart failure (NYHA class II) are currently not eligible for CRT and the potential beneficial effects in these patients have not been well studied. Fifty consecutive patients in NYHA class II heart failure and 50 consecutive patients in NYHA classes III to IV (control group) were prospectively included. All patients had left ventricular (LV) ejection fraction120 ms. The effects of CRT in NYHA class II patients were compared with the results obtained in both groups. The severity of baseline LV dyssynchrony (assessed with color-coded tissue Doppler imaging) was comparable between patients in NYHA class II versus those in NYHA classes III to IV (83+/-49 vs 96+/-51 ms, p=NS); resynchronization was achieved in all patients. NYHA class II patients showed a significant improvement in LV ejection fraction (from 25+/-7% to 33+/-10%, p<0.001) and reduction in LV end-systolic volume (from 168+/-55 to 132+/-51 ml, p<0.001) after CRT, similar to patients in NYHA classes III to IV. In addition, only 8% of NYHA class II patients had progression of heart failure symptoms. In conclusion, CRT had comparable effects in patients in NYHA class II and in NYHA classes III to IV heart failure in terms of LV resynchronization, improvement in LV ejection fraction, and LV reverse remodeling.     

心脏再同步化治疗与室性心律失常关系研究进展

心脏再同步化治疗可提高心力衰竭患者的运动耐力及纽约心功能分级,但心脏性猝死发生率在再同步化治疗患者中仍很高.有研究提示心脏再同步化治疗中左心室起搏可能通过逆转正常激动顺序、延长QT间期和增加全室壁复极离散度引起恶性室性心律失常的发生,对适合心脏再同步化治疗的患者应评估恶性室性心律失常发生风险,明确是否同时植入带除颤功能的心室电极.     

Evaluation of left bundle branch block as a reversible cause of non-ischaemic dilated cardiomyopathy with severe heart failure. A new concept of left ventricular dyssynchrony-induced cardiomyopathy.

OBJECTIVES: We sought to determine if amelioration of left bundle branch block (LBBB)-induced contraction disturbances achieved by left ventricular (LV)-based pacing could result in sustained reversal of severe LV dysfunction in certain patients with chronic heart failure due to non-ischaemic cardiomyopathy. BACKGROUND: It has been shown that LBBB induces asynchronous contraction of LV. However, whether such a functional contraction disturbance, if present for an extended period of time, could account for a dilated cardiomyopathy remains unknown. METHODS: The study population comprised 29 patients with dilated cardiomyopathy, sinus rhythm, LBBB and severe heart failure (14 patients in New York Heart Association (NYHA) class III and 15 in class IV). Patients were followed prospectively after resynchronization therapy. LV function was considered to be normalized when ejection fraction (EF) was >50% at 1 year. RESULTS: Five among the 29 patients (17%: group 1) demonstrated both complete normalization of LV function following resynchronization therapy (EF: from 19+/-6 to 55+/-3%, P = 0.001) and clinical improvement (mean NYHA class: 3.4+/-0.5 to 1.8+/-0.4, P = 0.02; 6-min walk distance: 300+/-136 to 444+/-75 m, P = 0.12; peak VO2: 11.9+/-4 to 15.8+/-2 ml/min/kg, p = 0.03). Among the remaining 24 patients (83%: group 2) EF improved but did not normalize (from 21+/-8 to 23+/-11%, ns). Baseline clinical features could not predict which patients would exhibit the reversal of LV dysfunction. CONCLUSIONS: Normalization of LV function 1 year after resynchronization therapy in a small but important number of patients suggests that long-standing LBBB may be a newly identified reversible cause of cardiomyopathy.