Electrical devices for left ventricular dysfunction and heart failure: do we need revised guidelines?

Three recent trials have demonstrated the benefit of cardiac resynchronization therapy (CRT) in the New York Heart Association (NYHA) class II patients with heart failure (HF) with ischemic or nonischemic cardiomyopathy as well as in NYHA class I (asymptomatic) patients mostly with ischemic cardiomyopathy. Earlier intervention with CRT in asymptomatic or minimally symptomatic patients improves survival and reduces HF hospitalizations. The reduction or the prevention of HF hospitalizations is of paramount importance because the HF episodes seem to alter the natural history of disease and are associated with deterioration of left ventricular (LV) function and a marked increase in mortality. The CRT benefit is greatest in patients with a QRS ≥ 150 ms. At this time, it would seem prudent to consider CRT-D (D = ICD) therapy for class I NYHA patients with a QRS ≥ 150 ms and an LV ejection fraction ≤ 30% regardless of etiology. Although the data for NYHA class I patients with nonischemic cardiomyopathy are scanty, the recommendation for class I patients is justified because CRT achieves a much greater degree of LV reverse remodeling in nonischemic compared to ischemic patients. With regard to lone ICDs, there is no evidence that they prevent sudden cardiac death more efficiently in symptomatic than in asymptomatic patients. Cardiomyopathy should be the primary target for device therapy regardless of symptoms for both CRT and lone ICD therapy. New guidelines are needed to address the role of CRT in hospitalized NYHA class IV HF patients or those who depend on inotropic therapy or an LV assist device because randomized CRT trials have not included these patients. CRT in these patients remains controversial. The mortality of such patients even with CRT is very high despite the occasional positive response. The role of CRT in patients waiting for cardiac transplantation also needs guidelines. With the expansion of CRT indications to minimally symptomatic or asymptomatic patients, the benefit of device therapy must be carefully weighed against the potential risk of lifelong device complications.     

Benefits of cardiac resynchronization therapy for heart failure patients with narrow QRS complexes and coexisting systolic asynchrony by echocardiography.

OBJECTIVES: This study was designed to evaluate the role of cardiac resynchronization therapy (CRT) in heart failure (HF) patients with narrow QRS complexes (<120 ms) and echocardiographic evidence of mechanical asynchrony. BACKGROUND: Cardiac resynchronization therapy is currently recommended to advanced HF patients with prolonged QRS duration. Echocardiographic assessment of systolic mechanical asynchrony has been proven useful to predict a favorable response after CRT. METHODS: A total of 102 HF patients with New York Heart Association (NYHA) functional class III or IV were enrolled. Among them, 51 had wide QRS (>120 ms) and 51 had narrow QRS (<120 ms). Tissue Doppler imaging (TDI) was employed to select patients with systolic asynchrony (increased asynchrony index) in the narrow-QRS group. Clinical and echocardiographic assessments were performed at baseline and 3 months after CRT. RESULTS: There was a significant reduction of left ventricular (LV) end-systolic volume in both narrow (122 +/- 42 cc vs. 103 +/- 47 cc, p < 0.001) and wide (148 +/- 74 cc vs. 112 +/- 64 cc, p < 0.001) QRS groups. Improvement of NYHA functional class (both p < 0.001), maximal exercise capacity (both p < 0.05), 6-min hall-walk distance (both p < 0.01), ejection fraction (both p < 0.001), and mitral regurgitation (both p < 0.005) was also observed. In both groups, the degree of baseline mechanical asynchrony determined LV reverse remodeling to a similar extent, as shown by the superimposed regression lines. Withholding CRT for 4 weeks resulted in loss of echocardiographic benefits. CONCLUSIONS: Cardiac resynchronization therapy for HF patients with narrow QRS complexes and coexisting mechanical asynchrony by TDI results in LV reverse remodeling and improvement of clinical status. The amplitude of benefit is similar to the wide-QRS group provided that similar extent of systolic asynchrony is selected.     

Cardiac resynchronization therapy in patients with end-stage inotrope-dependent class IV heart failure

Although cardiac resynchronization therapy (CRT) is beneficial in patients with drug-refractory New York Heart Association (NYHA) class III/IV heart failure (HF) and left ventricular (LV) dyssynchrony, CRT efficacy is not well established in patients with more advanced HF on inotropic support. Ten patients (age 55 +/- 13 years) with inotrope-dependent class IV HF (nonischemic [n = 6] and ischemic [n = 4]) received a CRT implantable cardioverter-defibrillator device. QRS duration was 153 +/- 25 ms (left branch bundle block [n = 7], intraventricular conduction delay [n = 2], and QRS <120 ms [n = 1]). The indication for CRT was based on either electrocardiographic criteria (n = 9) or echocardiographic evidence of LV dyssynchrony (n = 1). Intravenous inotropic therapy consisted of dobutamine (n = 6; 4.3 +/- 1.9 microg/kg/min) or milrinone (n = 4; 0.54 +/- 0.19 microg/kg/min) as inpatient (n = 3) or outpatient (n = 7) therapy for 146 +/- 258 days before CRT. One patient required ventilatory support before and during device implantation. All patients were alive at follow-up 1,088 +/- 284 days after CRT. Three patients underwent successful orthotopic cardiac transplantation after 56, 257, and 910 days of CRT. HF improved in 9 patients to NYHA classes II (n = 5) and III (n = 4). Intravenous inotropic therapy was discontinued in 9 of 10 patients after 15 +/- 14 days of CRT. LV volumes decreased (end-diastolic from 226 +/- 78 to 212 +/- 83 ml; p = 0.08; end-systolic from 174 +/- 65 to 150 +/- 78 ml; p <0.01). LV ejection fraction increased (23.5 +/- 4.3% to 32.0 +/- 9.1%; p <0.05). No implantable cardioverter-defibrillator shocks were recorded, and antitachycardia therapy for ventricular tachyarrhythmias was delivered in 1 patient. In conclusion, patients with end-stage inotrope-dependent NYHA class IV HF and LV dyssynchrony may respond favorably to CRT with long-term clinical benefit and improved LV function.     

Cardiac resynchronization therapy in patients with a narrow QRS complex.

OBJECTIVES: The purpose of this study was to evaluate the effects of cardiac resynchronization therapy (CRT) in heart failure patients with narrow QRS complex (<120 ms) and evidence of left ventricular (LV) dyssynchrony on tissue Doppler imaging (TDI). BACKGROUND: Cardiac resynchronization therapy is beneficial in selected heart failure patients with wide QRS complex (> or =120 ms). Patients with narrow QRS complex are currently not eligible for CRT, and the potential effects of CRT are not well studied. METHODS: Thirty-three consecutive patients with narrow QRS complex and 33 consecutive patients with wide QRS complex (control group) were prospectively included. All patients needed to have LV dyssynchrony > or =65 ms on TDI, New York Heart Association (NYHA) functional class III/IV heart failure, and LV ejection fraction < or =35%. RESULTS: Baseline characteristics, particularly LV dyssynchrony, were comparable between patients with narrow and wide QRS complex (110 +/- 8 ms vs. 175 +/- 22 ms; p = NS). No significant relationship was observed between baseline QRS duration and LV dyssynchrony (r = 0.21; p = NS). The improvement in clinical symptoms and LV reverse remodeling was comparable between patients with narrow and wide QRS complex (mean NYHA functional class reduction 0.9 +/- 0.6 vs. 1.1 +/- 0.6 [p = NS] and mean LV end-systolic volume reduction 39 +/- 34 ml vs. 44 +/- 46 ml [p = NS]). CONCLUSIONS: Cardiac resynchronization therapy appears to be beneficial in patients with narrow QRS complex and severe LV dyssynchrony on TDI, with similar improvement in symptoms and comparable LV reverse remodeling to patients with wide QRS complex. The current results need confirmation in larger patient cohorts.     

Cardiac resynchronization therapy in patients with narrow QRS

Conduction delay affecting 30-50% of patients with NYHA class III-IV heart failure (HF) mainly results from left bundle branch block and leads to deterioration of cardiac contractility through intra- and interventricular dyssynchrony. Cardiac resynchronization therapy (CRT) has class I recommendation for the treatment of patients with severe systolic HF who have left ventricular ejection fraction less or equal to 35%, QRS duration greater than or equal to 120 ms. Nevertheless some studies have shown that systolic asynchrony is present in 27-43% of HF patients with narrow QRS complexes (defined as <120 ms). We present here results of CRT in 20 patients (13 male, 7 female). Main indication for CRT was ventricular dyssynchrony during basic cardiac rhythm or cardiac pacing independently of QRS width. In 4 patients width of QRS complex was less than 120 ms, in 3 QRS varied from 120 to 149 ms pts and in 13 it was equal to or exceeded 150 ms. CRT in patients with narrow QRS resulted in clinical improvement associated with increase of cardiac contractility and decrease of left ventricular end systolic volume. This allows to conclude that CRT can be beneficial for HF patients with narrow QRS and ventricular dyssynchrony.     

Responders to cardiac resynchronization therapy with narrow or intermediate QRS complexes identified by simple echocardiographic indices of dyssynchrony: the DESIRE study

BACKGROUND: Cardiac resynchronization therapy (CRT) is recommended for patients with NYHA class III-IV refractory heart failure (HF), ejection fraction <35% and a QRS >120 ms. We attempted to identify responders to CRT from echocardiographic (echo) indices of mechanical dyssynchrony in patients with QRS<150 ms. METHODS AND RESULTS: The study enrolled 51 men and 9 women (mean age: 64.5 years) in NYHA class III (n=54) or IV (n=6) presenting with a mean ejection fraction: 25.7%, LV end-diastolic diameter: 69.1 mm, and QRS=121+/-19 ms. All patients were implanted with a CRT system and followed for 1 year. Implantation was preceded and followed by clinical, functional and Doppler (D)-echo evaluation. The primary combined endpoint included 1) death from any cause, 2) HF-related hospitalisations, and 3) NYHA class at 6 months. Before implant, 27 patients had > or =1 echo criterion of mechanical dyssynchrony (DES+ group) and 33 had no evidence of dyssynchrony (DES- group). At 12 months, 8 patients (4 per group) had died, 7 from HF. As regards the primary endpoint at 6 months, 33 patients (55%) had improved, 10 (16%) were unchanged, and 17 (29%) had deteriorated. Clinical improvement was observed in 19 of 27 DES+ (70%), versus 14 of 33 DES- (42%) patients (P<0.04). Baseline QRS duration did not predict response to CRT. CONCLUSIONS: In this population of HF patients with QRS<150 ms, the presence of mechanical dyssynchrony at baseline D-echo examination, but not the QRS width, predicted 6-month clinical response to CRT.     

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.     

心脏再同步化治疗之适应证更新——亦宽？亦严？

欧洲心脏病学会2013年更新了其起搏与心脏再同步的临床指南,其中对心脏再同步化治疗的适应证进行了调整。新指南中对于QRS波的宽度和形态,给予更严格的要求。任何QRS波〈120ms的病人均不是心脏再同步化治疗的适应证,而120～150ms之间的QRS,只限于左柬支阻滞形态。新的指南涵盖了更多的轻、中度心力衰竭,心功能lI级亦纳入适应证。具有传统的心动过缓适应证的心力衰竭病人,新植入起搏器时,再同步的适应证很宽松,而对已有传统起搏器的升级仍保持较严格的适应证。     

Kommentar zu den ESC-Leitlinien zur Device-Therapie bei Herzinsuffizienz 2010

As part of the 2010 focused update of ESC guidelines on device therapy in heart failure, the guidelines on pacemakers in the treatment of heart failure were renewed. A new feature is that cardiac resynchronization therapy (CRT) is indicated for New York Heart Association (NYHA) class III and IV irrespective of the presence of left ventricular dilatation and specified for NYHA class IV (patient ambulatory, stable, life expectancy >6 months). Furthermore, NYHA class II (but not class I) has been added when there is left bundle branch block and QRS duration ≥150 ms. CRT is also indicated for patients in NYHA class III-IV with permanent atrial fibrillation and heart failure [left ventricular ejection fraction (LVEF) ≤ 35%] when QRS is ≥ 130 ms and ventricular rate has slowed either spontaneously or by AV node ablation. In patients with heart failure (NYHA class II-IV, LVEF ≤ 35%) who need a pacemaker for AV block, CRT is generally indicated to avoid progression of heart failure caused by right ventricular stimulation, also in cases of intrinsic QRS <120 ms. For patients with terminal heart failure who are not eligible for heart transplantation, treatment with a left ventricular assist device can be performed as destination therapy. The new guidelines expand the indication for device therapy in heart failure based on the newest study findings, particularly for patients in NYHA class II, and specify the old guidelines. There are still uncertainties that must be investigated in randomized trials regarding patients with permanent atrial fibrillation, the indication for CRT in heart block, and the question of CRT with pacemaker or defibrillator.     

Does Contractility Modulation Have a Role in the Treatment of Heart Failure?

Cardiac resynchronization therapy (CRT) is an established therapy for patients with systolic dysfunction, QRS duration greater than 120 ms, and New York Heart Association (NYHA) class III or IV symptoms. However, most patients with heart failure have QRS duration below 120 ms and 30% or more of CRT recipients are nonresponders. Cardiac contractility modulation (CCM) signals are nonexcitatory electrical impulses applied during the absolute refractory period that are intended to enhance contractile strength independent of QRS duration. Myocardial biopsy studies suggest that modulation of protein phosphorylation and gene expression underlie the mechanisms by which CCM exerts its effects. Two prospective randomized studies have investigated the impact of CCM on exercise tolerance and quality of life in patients with chronic heart failure. These studies have included predominantly patients with NYHA class III heart failure with QRS duration below 130 ms. This review summarizes results of these clinical studies and outlines additional studies underway to further clarify the role of CCM in the treatment of heart failure.     

The resynchronization therapy in narrow QRS study (RethinQ study): Methods and protocol design

Background Numerous trials have demonstrated the effectiveness of cardiac resynchronization therapy (CRT) as an adjunct to medical therapy for the relief of heart failure (HF) symptoms in patients with a wide QRS duration (QRSd). Current guidelines recommend CRT in patients with an EF <35%, medically refractory NYHA Class III–IV HF and QRSd ≥120 ms. Previous studies have demonstrated QRSd as a marker of electrical dyssynchrony fails to predict response to CRT. In addition, studies have demonstrated significant differences in QRSd post CRT between responders and non-responders. Moreover, smaller non-controlled studies demonstrated that HF patients with a narrow QRSd may benefit from CRT. A growing body of evidence suggests that echocardiographic criteria may be a better method to evaluate mechanical dyssynchrony (MD) which may predict those that will benefit from CRT, particularly those with a narrow QRSd. The Resynchronization Therapy In Narrow QRS (RethinQ) study will evaluate mechanical dyssynchrony using echocardiography (both M mode and TDI) as an eligibility requirement for CRT. Methods The RethinQ study is a prospective, multi-center, randomized, double blind controlled clinical study. The objective of the RethinQ study is to evaluate the effectiveness of CRT in patients with approved ICD indication, advanced HF (NYHA Classification III), narrow QRSd (<130 ms) and evidence of MD measured by echocardiography. Conclusion We hypothesize that patients with narrow QRS <130 ms, advanced HF, and MD as measured by echocardiography will benefit from CRT. An erratum to this article can be found at     

Triple-Site Versus Standard Cardiac Resynchronization Therapy Study (TRUST CRT): Clinical Rationale, Design, and Implementation

Background: Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with heart failure (HF), lowered LV ejection fraction, and wide QRS. However, many patients (≤40%) do not respond to this form of pacing. TRUST CRT is a prospective, single-center, randomized, single-blind, parallel, and controlled study that has been designed to treat patients with moderate to severe HF (NYHA III-IV), QRS ≥120 ms, sinus rhythm, LV dysfunction (EF ≤ 35%), and signs of mechanical dyssynchrony.
Objective: The primary objective will evaluate the 6-month's combined endpoint of alive status, freedom from hospitalization for HF or heart transplantation, relative ≥10% increase in LV ejection fraction, ≥10% in peak oxygen consumption, and ≥10% in 6-minute walking distance.
Methods: Patients with HF receiving optimal pharmacotherapy, with LV dysfunction, mechanical dyssynchrony, wide QRS and sinus rhythm will be randomized in a 1: 1 fashion to standard or triple-site CRT-D. Patients will be followed for 1 week, 1, 3, and 6 months during a blind phase, then every 6 months until study completion. One hundred patients will be enrolled by the study center.
Conclusions: TRUST CRT is a randomized, clinical trial in CRT candidates to evaluate the effectiveness of triple-site pacing versus standard resynchronization in patients with HF.     

Effect of cardiac resynchronization therapy in patients with moderate left ventricular systolic dysfunction and wide QRS complex: a prospective study

Background: We sought to investigate the effect of cardiac resynchronization therapy (CRT) on disease progression in patients with moderate left ventricular (LV) systolic dysfunction.
Methods and Results: This is a prospective study to explore the effect of CRT in 15 optimally treated patients (age: 66.1 ± 12.8 years; male = 13) with New York Heart Association (NYHA) class III, LV ejection fraction >35% and <45% and QRS duration >120 msec. Echocardiographic examination and standard heart failure assessment was performed before and 3 months after CRT implantation. The magnitude of echocardiographic remodeling measurements was compared with 30 age, sex, NYHA class, and heart failure etiology matched patients with conventional CRT indication. There were significant reductions in LV end-systolic (86.2 ± 24.1 to 69.7 ± 22.2 mL, P < 0.01)/end-diastolic (135.5 ± 36.8 to 120.5 ± 34.6 mL, P < 0.01) volumes, improvement in LV ejection fraction (39.1 ± 2.2 to 44.2 ± 5.5%, P = 0.01), and NYHA class (3.0 ± 0.0 to 2.07 ± 0.46, P < 0.001). There was no difference in changes in LV volumes, ejection fraction, NYHA class, and exercise capacity before and after CRT between the study and conventional groups except for greater improvement in the quality of life score in the conventional group.
Conclusion: In this prospective study, significant LV reverse remodeling by CRT in those with a wide QRS complex and moderate LV systolic dysfunction was observed. Further studies to explore the benefit of CRT in patients with less severe heart failure are recommended.     

Cardiac resynchronisation therapy: evidence based benefits and patient selection

Despite the improvement in pharmacologic treatment of heart failure, many patients continue to have severe persistent symptoms, and their prognosis remains poor. One of the most recent advances in heart failure management is the concept of cardiac resynchronization therapy (CRT) with right and left ventricular pacing. Large clinical trials have demonstrated morbidity and mortality benefits of CRT in patients with moderate to severe drug refractory heart failure (New York Heart Association (NYHA) functional class III or IV), and ejection fraction < or = 35% with QRS duration > or = 120 ms. Despite the documented benefits, 20-30% of patients selected to have CRT do not respond to this treatment. Echocardiography will probably play a more important role in better selecting patients with mechanical dyssynchrony who are more likely to respond to CRT. This article reviews the available evidence for CRT as well as the way to select responders to this rather invasive therapy.     

Cardiac resynchronisation therapy in patients with end-stage heart failure--long-term follow-up

BACKGROUND: Cardiac resynchronisation therapy (CRT) has been shown to be effective in the treatment of patients with end-stage heart failure (HF). However, long-term results of CRT have not yet been validated. AIM: To assess the sustained benefit of CRT in patients with end-stage HF at long-term follow-up. In addition, predictors of response to CRT were analysed. METHODS: Twenty-eight patients with end-stage HF, NYHA class >or=III (>or=II in patients with indications for ICD and echocardiographic signs of ventricular mechanical systolic dyssynchrony), left ventricular ejection fraction <35%, QRS duration >120 ms and left bundle branch block morphology received a biventricular device (BiV). In 27 patients LV pacing was achieved via the coronary sinus tributaries and in 1 patient an endocardial LV lead was introduced transseptally. Ten patients received an ICD-CRT device. The control group consisted of 29 patients fulfilling the criteria for ICD-CRT implantation in whom the CRT system was not implanted for various reasons. At baseline, 3 months after implantation, and then every 6 months the following parameters were evaluated: NYHA class, quality of life (QoL) score, QRS duration on surface ECG, and 6-minute walking distance. The need for hospitalisation assessed one year before and one year after implantation was compared. Follow-up was obtained up to 2 years. RESULTS: The NYHA class and 6-minute walking test were significantly improved in the CRT group after 3 months and continued to improve gradually until 24 months of follow-up. The QoL improvement at 6 months was sustained over 2 years. Hospitalisation rate due to worsening of HF decreased. One-year and two-year survival were significantly better in the CRT group than in the control group (94 and 87 vs. 80 and 73% respectively). The only predictor of clinical improvement after CRT implantation was baseline NYHA class. CONCLUSION: Clinical improvements with CRT are progressive and sustained over 2 years of follow-up.     

Clinical efficacy of cardiac resynchronization therapy using left ventricular pacing in heart failure patients stratified by severity of ventricular conduction delay

OBJECTIVES: We assessed the clinical efficacy of single-site left ventricular (LV) pacing and determined the impact of baseline conduction delay severity on the magnitude of benefit. BACKGROUND: Multisite biventricular pacing can improve heart failure (HF) symptoms in patients with an intraventricular conduction delay by resynchronizing abnormal ventricular contractions and improving LV systolic function. METHODS: Eighty-six patients with at least New York Heart Association functional class II HF, chronic LV systolic dysfunction, normal sinus rhythm, and a QRS interval over 120 ms were implanted for atrial-synchronized LV pacing. The single-blinded, randomized, controlled, crossover study stratified patients 1:1 by the baseline QRS interval into long (QRS >150 ms) and short (QRS 120 to 150 ms) groups, which were compared during a three-month period of active (univentricular) pacing and a three-month period of inactive (ventricular inhibited) pacing. The primary end point was peak oxygen consumption (VO(2)) followed by anaerobic threshold, distance walked in 6 min, and quality-of-life questionnaire score. PATIENTS: Twelve patients were withdrawn before randomization and 17 could not complete both study periods. The short QRS group did not improve in any end point with active pacing. For the long QRS group, peak VO(2) increased 2.46 ml/min/kg (p < 0.001), the anaerobic threshold increased 1.55 ml/min/kg (p < 0.001), the distance walked in 6 min increased 47 m (p = 0.024), and the quality-of-life score improved 8.1 points (p = 0.004). CONCLUSIONS: Left ventricular pacing significantly improves exercise tolerance and quality of life in patients with chronic HF, LV systolic dysfunction, and a QRS interval over 150 ms.     

Comparison of cardiac resynchronization therapy outcomes in patients with New York Heart Association functional class I/II versus III/IV heart failure

BackgroundSeveral randomized trials have shown that cardiac resynchronization therapy (CRT) benefits New York Heart Association (NYHA) functional class I/II heart failure (HF) patients, but it is unknown if similar outcomes occur in the real-world.Methods and ResultsAll patients receiving CRT between 2003 and 2008 with ejection fraction (EF) ≤35% and QRS duration ≥120 ms were included. Outcomes assessed were subjective clinical response, echocardiographic response, and survival free of cardiovascular (CV) hospitalization. Baseline demographics in functional class I/II (n = 155) and functional class III/IV (n = 512) were similar, except for differences in age and several comorbidities. Clinical response was similar in both groups. The functional class I/II group had a greater decrease in left ventricular (LV) end-diastolic dimension (P = .031), and trended toward greater improvements in LV end-systolic dimension (P = .056) and EF (P = .059). The functional class I/II group had a better 5-year survival rate (79 vs 54%; P < .0001) and survival free of CV hospitalization (45% vs 26%; P < .0001).ConclusionsIn this real-world clinical scenario, NYHA functional class I/II CRT patients improved clinical status, and LV function and size as good as or better than those in NYHA functional class III/IV patients. These observations provide further support for the use of CRT in patients with mild symptoms of HF.     

The benefit of cardiac resynchronization therapy and QRS duration: a meta-analysis

CRT and QRS Duration . Background: Cardiac resynchronization therapy (CRT) improves outcomes in patients with heart failure (HF) because of reduced left ventricular systolic function and a wide QRS complex. Whether this benefit is consistent across all degrees of QRS widening is unclear. We performed a meta‐analysis of randomized clinical trials to evaluate the impact of QRS duration on the efficacy of CRT. Methods and Results: We searched MEDLINE and EMBASE databases for studies evaluating the efficacy of CRT in patients with HF. Only trials that reported subgroup data according to QRS duration were included. Hazard ratios (HR) with 95% confidence interval (CI) were calculated using a random effects model. Five trials involving 6,501 patients (4,437 with QRS ≥ 150 ms and 2,064 with QRS < 150 ms) were included. Three trials, enrolling patients with mild to moderate HF, compared CRT‐implantable cardioverter defibrillator with CRT, whereas CRT versus medical therapy was compared in the other 2 trials, which included patients with advanced HF. Based on the pooled estimate across the 5 studies, CRT significantly decreased the primary endpoint of death or hospitalization for HF in patients with QRS ≥ 150 ms (HR = 0.58, 95% CI: 0.50–0.68; P < 0.00001), but not in patients with QRS < 150 ms (HR = 0.95, 95% CI: 0.83–1.10; P = 0.51). These results were consistent across all degrees of HF severity. Conclusions: The benefit of CRT seems to be dependent on QRS duration. Available data suggest a significant benefit associated with CRT in patients with QRS ≥ 150 ms, but not in patients with QRS < 150 ms. Further studies are needed to identify patients with QRS < 150 ms who might benefit from CRT. (J Cardiovasc Electrophysiol, Vol. 23, pp. 163‐168, February 2012)     

Comparison of efficacy of reverse remodeling and clinical improvement for relatively narrow and wide QRS complexes after cardiac resynchronization therapy for heart failure

INTRODUCTION: Cardiac resynchronization therapy (CRT) has been shown to reverse left ventricular (LV) remodeling and improve symptoms in heart failure patients with wide QRS complexes; however, its role in patients with mildly prolonged QRS complexes is unclear. This study investigated if CRT benefited patients with mildly prolonged QRS complexes >120 to 150 ms and explored if the severity of systolic asynchrony determined such a response. METHODS AND RESULTS: Fifty-eight patients (age 66 +/- 11 years, 66% male) who had undergone CRT were studied prospectively. Of these patients, 27 had QRS duration between 120 and 150 ms (group A), and 31 had QRS duration >150 ms (group B). Tissue Doppler echocardiography and clinical assessment were performed at baseline and 3 months after CRT. Both groups had significant reduction of LV volume and increased ejection fraction, +dP/dt, and sphericity index (all P < 0.05). These improvements were greater in group B and were explained by the higher prevalence of systolic intraventricular asynchrony. Significant reverse remodeling (reduction of LV end-systolic volume >15%) was evident in 46% of group A patients and 68% of group B patients. Improvement in clinical endpoints was observed in both groups (all P < 0.01), although the changes in metabolic equivalent and New York Heart Association functional class were greater in group B. In both groups, systolic asynchrony index (TS-SD) was the most important predictor of reverse remodeling (r =-0.78, P < 0.001) and was the only independent predictor in the multivariate model (beta=-1.80, confidence interval =-2.18 to -1.42, P < 0.001); QRS duration was not. A predefined TS-SD value >32.6 ms had a sensitivity of 94% and specificity of 83% to predict reverse remodeling. Improvement of intraventricular asynchrony after CRT was evident only in responders (P = 0.01). CONCLUSION: Improvement of LV remodeling and clinical status is evident after CRT in heart failure patients with QRS duration >120 to 150 ms. These responders are closely predicted by the severity of prepacing intraventricular asynchrony but not QRS duration.