Role of cardiac resynchronization therapy in asymptomatic and mildly symptomatic heart failure

Cardiac resynchronization therapy (CRT) improves quality of life, left ventricular (LV) size and function, and mortality among moderate to severe symptomatic congestive heart failure (CHF) patients with decreased LV ejection fraction and QRS prolongation. Whether these benefits extend to similar groups with minimal or mild CHF is an area of ongoing investigation. Two small studies with limited follow-up demonstrated reverse remodeling but no symptomatic improvement. A recent, larger study in a population of asymptomatic or mildly symptomatic CHF patients with longer follow- up confirmed the beneficial effect of CRT on LV size and function; furthermore, it was the first study to show that CRT improves clinical outcome with delayed time to heart failure hospitalization. Ongoing trials of CRT in such patients will soon provide further data on morbidity and mortality.     

Significance of QRS complex duration in patients with heart failure

Prolongation of QRS (> or =120 ms) occurs in 14% to 47% of heart failure (HF) patients. Left bundle branch block is far more common than right bundle branch block. Left-sided intraventricular conduction delay is associated with more advanced myocardial disease, worse left ventricular (LV) function, poorer prognosis, and a higher all-cause mortality rate compared with narrow QRS complex. It also predisposes heart failure patients to an increased risk of ventricular tachyarrhythmias, but the incidence of cardiac or sudden death remains unclear because of limited observations. A progressive increase in QRS duration worsens the prognosis. No electrocardiographic measure is specific enough to provide subgroup risk categorization for excluding or selecting HF patients for prophylactic implantable cardioverter-defibrillator (ICD) therapy. In ICD patients with HF, a wide underlying QRS complex more than doubles the cardiac mortality compared with a narrow QRS complex. There is a high incidence of an elevated defibrillation threshold at the time of ICD implantation in patients with QRS > or =200 ms. Mechanical LV dyssynchrony potentially treatable by ventricular resynchronization occurs in about 70% of HF patients with left-sided intraventricular conduction delay, a fact that would explain the lack of therapeutic response in about 30% of patients subjected to ventricular resynchronization according to standard criteria relying on QRS duration. The duration of the basal QRS complex does not reliably predict the clinical response to ventricular resynchronization, and QRS narrowing after cardiac resynchronization therapy does not correlate with hemodynamic and clinical improvement. Mechanical LV dyssynchrony is best shown by evolving echocardiographic techniques (predominantly tissue Doppler imaging) currently in the process of standardization.     

Significance of QRS complex duration in patients with heart failure.

Prolongation of QRS (> or =120 ms) occurs in 14% to 47% of heart failure (HF) patients. Left bundle branch block is far more common than right bundle branch block. Left-sided intraventricular conduction delay is associated with more advanced myocardial disease, worse left ventricular (LV) function, poorer prognosis, and a higher all-cause mortality rate compared with narrow QRS complex. It also predisposes heart failure patients to an increased risk of ventricular tachyarrhythmias, but the incidence of cardiac or sudden death remains unclear because of limited observations. A progressive increase in QRS duration worsens the prognosis. No electrocardiographic measure is specific enough to provide subgroup risk categorization for excluding or selecting HF patients for prophylactic implantable cardioverter-defibrillator (ICD) therapy. In ICD patients with HF, a wide underlying QRS complex more than doubles the cardiac mortality compared with a narrow QRS complex. There is a high incidence of an elevated defibrillation threshold at the time of ICD implantation in patients with QRS > or =200 ms. Mechanical LV dyssynchrony potentially treatable by ventricular resynchronization occurs in about 70% of HF patients with left-sided intraventricular conduction delay, a fact that would explain the lack of therapeutic response in about 30% of patients subjected to ventricular resynchronization according to standard criteria relying on QRS duration. The duration of the basal QRS complex does not reliably predict the clinical response to ventricular resynchronization, and QRS narrowing after cardiac resynchronization therapy does not correlate with hemodynamic and clinical improvement. Mechanical LV dyssynchrony is best shown by evolving echocardiographic techniques (predominantly tissue Doppler imaging) currently in the process of standardization.     

Effects of resynchronization therapy on cardiac function in pacemaker patients "upgraded" to biventricular devices

INTRODUCTION: Cardiac resynchronization therapy (CRT) improves echocardiographic measures of cardiac function and has a variable effect on QRS duration in patients with left bundle branch block (LBBB). How CRT affects these indices in patients with right ventricular (RV) pacing-induced LBBB who are "upgraded" with left ventricular (LV) leads for CRT is unknown. We studied the echocardiographic effects of RV pacing and CRT in patients with prior continuous RV pacing after LV lead placement. METHODS AND RESULTS: Fifteen consecutive patients (age 73 +/- 11 years, LV ejection fraction 24 +/- 6%, QRS duration 190 +/- 27 msec) with New York Heart Association class IIIB-IV symptoms and continuous RV pacing underwent LV lead placement for CRT. Echocardiography and ECG were performed sequentially during RV pacing and CRT. CRT was associated with significantly reduced QRS duration (190 +/- 27 msec vs 165 +/- 18 msec, P = 0.005) and reduced LV electromechanical delay (180 +/- 33 msec vs 161+/- 43 msec). Baseline QRS duration correlated with CRT response. After CRT, patients had significant improvements in indices of systolic function, including LV ejection fraction, myocardial performance index (MPI), and LV ejection time. Abnormal baseline MPI was associated with greater improvement after CRT. LV end-diastolic and systolic volumes were similarly decreased with CRT. Mitral valve deceleration time, an index of diastolic function, was not affected by CRT. CONCLUSION: "Upgrading" RV paced patients with advanced heart failure to CRT improves measures of electrical and LV mechanical synchrony and improves systolic function.     

Usefulness of microvolt T-wave alternans on predicting outcome in patients with ischemic cardiomyopathy with and without defibrillators

Microvolt T-wave alternans (MTWA) was proposed as an effective tool to identify high-risk patients with ischemic cardiomyopathy. However, previous studies suggested that the prognostic utility of MTWA may be limited to only patients with normal QRS duration. It therefore was assessed whether MTWA and QRS duration >120 ms independently predict mortality in patients with ischemic cardiomyopathy and whether the prognostic utility of MTWA differs by QRS duration. A total of 768 consecutive patients with ischemic cardiomyopathy (left ventricular ejection fraction < or =35%) and no history of ventricular arrhythmia were enrolled, of whom 514 (67%) screened MTWA non-negative (positive or indeterminate) and 223 (29%) had a QRS >120 ms on resting electrocardiogram. After multivariable adjustment, a non-negative MTWA test result was associated with a significantly higher risk for all-cause mortality in patients without an implantable cardioverter-defibrillator (ICD) (hazard ratio [HR] 2.27, 95% confidence interval [CI] 1.22 to 4.24, p = 0.01) and for all-cause mortality and appropriate ICD shocks in patients with an ICD (HR 2.42, 95% CI 1.07 to 5.41, p = 0.04). In contrast, a QRS >120 ms was not associated with all-cause mortality and ICD shocks in patients without (HR 0.96, 95% CI 0.52 to 1.75, p = 0.88) or with an ICD (HR 1.25, 95% CI 0.76 to 2.08, p = 0.40). No significant interaction was found between MTWA and QRS >120 ms (non-ICD p = 0.19, ICD p = 0.73). In conclusion, MTWA, but not QRS duration, predicted mortality outcomes in patients with ischemic cardiomyopathy. Moreover, the prognostic utility of MTWA did not appear to differ by QRS duration.     

Reduced mitral regurgitation in heart failure patients submitted to cardiac resynchronization therapy: a short-term prospective study.

BACKGROUND: The intraventricular delay is a determinant of functional mitral regurgitation (MR). MR contributes to the progression of congestive heart failure (CHF) and represents a marker of a worse outcome. The aim of this study was to test the hypothesis that cardiac resynchronization therapy (CRT) significantly reduces MR in CHF patients with ventricular conduction defects. METHODS: We studied 45 consecutive patients (37 males, 8 females, mean age 72 +/- 9 years) in NYHA class III-IV, with left ventricular ejection fraction < 35%, QRS duration > 150 ms with left bundle branch block or already paced in the right ventricle, and MR score > or = 1. We compared the QRS duration and the basal peak of the V-wave before and 15 min after CRT. Before implantation and 1 week after we measured ejection fraction, systolic mitral annulus diameter, MR area, left atrial area, MR area expressed as the percentage of the left atrial area (%MR area), and MR score (range 1-4). RESULTS: The QRS duration before and after CRT was 195 +/- 30 and 156 +/- 17 ms (p < 0.01) respectively. Significant decreases were observed in the systolic mitral annulus diameter (-7.9%, p < 0.001), MR area (-38%, p < 0.001), MR score (-33.4%, p < 0.001), left atrial area (-5.9%, p < 0.05), and %MR area (-36.2%, p < 0.001). The peak of the V-wave decreased by 33%. The ejection fraction increased by 46% (p < 0.001). CONCLUSIONS: CRT significantly reduces MR and improves cardiac function in patients with CHF and ventricular conduction defects. The combination of the degree of MR and a low ejection fraction and large QRS duration may contribute to a more reliable patient selection for CRT.     

Usefulness of spatial dispersion of QRS duration in predicting mortality in patients with mild to moderate chronic heart failure

To prospectively evaluate the prognostic significance of spatial dispersion of QRS duration (S-QRSd) on a signal-averaged electrocardiogram in patients with chronic heart failure (CHF), we studied 114 consecutive stable outpatients with radionuclide left ventricular ejection fraction <40%. Cardiac and sudden deaths were significantly more often observed in patients with than without abnormal S-QRSd. S-QRSd is a powerful prognostic marker of the mortality in patients with mild to moderate CHF.     

Ventricular tachycardia induced by biventricular pacing in patient with severe ischemic cardiomyopathy

INTRODUCTION: Cardiac resynchronization therapy (CRT) is a new alternative which affords symptomatic improvement in two-thirds of patients who exhibit medically refractory congestive heart failure (CHF) as well as significant prolongation of the QRS duration (>135 msec). As more experience with CRT accrues, unexpected complications of this promising therapy may become apparent. Herein, we describe a patient with severe ischemic cardiomyopathy and refractory CHF who developed incessant ventricular tachycardia (VT) after the initiation of biventricular pacing. The patient is a 75-year-old man who suffered an inferior myocardial infarction 6 years before presenting for CRT. He underwent a three-vessel CABG in 1997. Subsequently, episodes of near syncopal sustained VT developed, for which he received a dual chamber ICD. In 2001 he developed refractory CHF and ECG revealed LBBB with a QRS duration of 195 msec. Shortly after the initiation of biventricular pacing, the patient developed multiple episodes of drug resistant monomorphic VT that could be terminated only transiently by ICD therapies. Ultimately, the only intervention, which proved to be effective in eliminating VT episodes, was inactivation of LV pacing. Despite subsequent therapeutic regimen of sotalol, lidocaine, tocainide, and quinidine all subsequent attempts to reactivate LV pacing resulted in prompt VT recurrence. CONCLUSION: This case represents a clear example of CRT induced proarrhythmia, which required inactivation of LV pacing for effective acute management. Such an intervention should be considered in CRT patients who exhibit a notable increase in drug refractory VT episodes.     

Benefit of combined resynchronization and defibrillator therapy in heart failure patients with and without ventricular arrhythmias.

OBJECTIVES: We attempted to assess the efficacy of combined cardiac resynchronization therapy-implantable cardioverter-defibrillator (CRT-ICD) in heart failure patients with and without ventricular arrhythmias. BACKGROUND: Because CRT and ICDs both lower all-cause mortality in patients with advanced heart failure, combination of both therapies in a single device is challenging. METHODS: A total of 191 consecutive patients with advanced heart failure, left ventricular ejection fraction <35%, and a QRS duration >120 ms received CRT-ICD. Seventy-one patients had a history of ventricular arrhythmias (secondary prevention); 120 patients did not have prior ventricular arrhythmias (primary prevention). During follow-up, ICD therapy rate, clinical improvement after 6 months, and mortality rate were evaluated. RESULTS: During follow-up (18 +/- 4 months), primary prevention patients experienced less appropriate ICD therapies than secondary prevention patients (21% vs. 35%, p < 0.05). Multivariate analysis revealed, however, no predictors of ICD therapy. Furthermore, a similar, significant, improvement in clinical parameters was observed at 6 months in both groups. Also, the mortality rate in the primary prevention group was lower than in the secondary prevention group (3% vs. 18%, p < 0.05). CONCLUSIONS: As 21% of the primary prevention patients and 35% of the secondary prevention patients experienced appropriate ICD therapy within 2 years after implant, and no predictors of ICD therapy could be identified, implantation of a CRT-ICD device should be considered in all patients eligible for CRT.     

Assessment of left ventricular dyssynchrony in patients with heart failure and normal QRS duration

Cardiac resynchronization therapy (CRT) is an important component of heart failure therapy in patients with a left ventricular ejection fraction <35%, class III or ambulatory class IV symptoms, and a QRS duration >120 ms. The QRS duration criterion for patient selection is imperfect. About 30% of patients with an increased QRS duration are nonresponders to CRT and many with a normal QRS duration with mechanical dyssynchrony respond to CRT. The authors review the currently available echocardiographic tools for the assessment of ventricular dyssynchrony in patients with heart failure.     

心脏再同步治疗对慢性心力衰竭的临床疗效观察

目的观察心脏再同步治疗（CRT）对慢性心力衰竭的长期临床疗效。方法24例接受CRT的慢性心力衰竭患者,心功能Ⅲ～Ⅳ级（NYHA分级）,左心室射血分数（LVEF）≤0．35,左心室舒张末内径（LVEDD）／〉55mm,QRS时限≥120／TIS。植入前超声心动图及组织多普勒检查以评价心功能及心脏收缩不同步指标,并指导左心室电极导线的植入。植入后3、6个月及随后的每6个月进行随访,随访内容包括临床症状、心电图、LVEDD、LVEF及多普勒超声评价心脏收缩同步性指标。结果随访时间（12．0±4．6）个月,结果显示患者临床症状明显改善,QRS时限植入后较植入前缩短[（137．50±38．96）ms对（144．60±45．78）ms,P=0．67],但差异无统计学意义。植人后LVEDD较植入前明显缩小[（6．24±0．89）cm对（6．78±0．42）cm,P=0．03];LVEF则明显提高（0．36±0．09对0．31±0．03,P〈0．01）,左心房内径（LAD）也较术前明显缩小[（4．22±8．43）cm对（5．32±7．63）cm,P=0．01]。心脏收缩不同步指标与植入前相比也明显改善。结论对慢性心力衰竭的患者,CRT治疗可改善左心室功能,逆转左心室重构。     

Usefulness of QRS duration to predict response to cardiac resynchronization therapy in patients with end-stage heart failure

Despite current selection criteria, 20% to 30% of patients treated with cardiac resynchronization therapy (CRT) do not benefit. It has been suggested that QRS duration may not be the optimal criterion to select patients for CRT. The objective of this study was to systematically evaluate the predictive value of QRS duration for response to CRT in a large group of consecutive patients. A total of 242 patients with heart failure scheduled for implantation of a CRT device were studied. Selection criteria for CRT included moderate to severe heart failure (New York Heart Association classes III to IV), left ventricular ejection fraction (LVEF)120 ms. Before CRT implantation, QRS duration and clinical status were assessed, and 2-dimensional echocardiography (LV volumes and LVEF) was performed. Clinical status and changes in LVEF and LV volumes were reassessed at 6-month follow-up. After 6 months of CRT, 68% of patients were classified as clinical responders (improvement of >or=1 grade in New York Heart Association class) and 60% as echocardiographic responders (decrease>10% in LV end-systolic volume). At baseline, no significant differences were observed in QRS duration between clinical responders and nonresponders and between echocardiographic responders and nonresponders. No significant relation was demonstrated between baseline QRS duration and improvement in clinical and echocardiographic variables at 6-month follow-up. In conclusion, baseline QRS duration is not predictive for clinical and echocardiographic responses to CRT at 6-month follow-up. Better predictors for CRT response are needed.     

Successful treatment of heart failure with devices requires collaboration

Implanted biventricular pacemakers (cardiac resynchronisation therapy, CRT) with or without implantable cardioverter defibrillators (ICD) improve survival and morbidity in some patients with chronic heart failure (CHF) who are optimally treated with pharmacologic agents according to current guidelines. Correspondingly, ICDs improve survival. However, there is only limited evidence for device treatment in certain patient subgroups, such as the impact of ICD on outcomes in patients with reduced ejection fraction in New York Heart Association (NYHA) Class I or IV heart failure. Similarly, limited evidence exists for CRT in patients with only modest QRS prolongation or only modestly reduced ejection fraction. Despite evidence for a beneficial effect of device therapy in CHF, only a minority of eligible patients are currently offered these options. Multiple reasons contribute to the underuse of these potentially life‐saving therapies. A lack of adherence to guidelines by health care professionals is an important barrier. Clearly, efforts should be made to improve the standard of care and to familiarise all physicians involved in managing CHF patients with the indications and potential efficacy of these devices. Increased collaboration between structured heart failure care and pacemaker clinics as well as between electrophysiologists, heart failure clinicians, and primary care physicians is required. Such team collaborations should lead to improved care with reduced mortality and morbidity and increased cost effectiveness. Treatment strategy should be based on a structured approach tailored to local practice and national priorities.     

Prognostic value of the QRS duration in patients with heart failure: a subgroup analysis from 24 centers of Val-HeFT

BACKGROUND: This study investigated whether QRS duration (QRS D) is a prognostic indicator in patients with heart failure (New York Heart Association [NYHA] classes II-IV). METHODS AND RESULTS: This subgroup analysis included 248 patients with heart failure recruited in the German centers of the Valsartan Heart Failure Trial (Val-HeFT). Mean age was 60 years, mean NYHA class was 2.3, and mean left ventricular ejection fraction (EF) was 27.9%. Electrocardiograms were recorded and analyzed at the beginning of the study, at 2 weeks, 4 months, 1 year, and 2 years. The mean observation period for mortality was 25 months. Patients > or = 65 years and patients with an EF <20% had a significantly longer QRS D (P = .02; P = .0005). NYHA class, etiology of heart failure, therapy with angiotensin-converting enzyme inhibitors, amiodarone or beta-blockers, implanted defibrillator, and atrial fibrillation had no significant influence on QRS D. Total mortality was 9%: 14 patients died suddenly, 7 from heart failure, 2 from noncardiac causes. Kaplan-Meier plots show significantly different survival rates for patients with QRS D <120 ms, QRS D 120-159 ms, or QRS D > or = 160 ms (P = .0085). Multivariate analysis showed that QRS D was the only independent risk factor for all-cause mortality (P = .008). NYHA class, EF, atrial fibrillation, age, and gender failed to qualify as independent prognostic factors. CONCLUSION: QRS duration in the surface electrocardiogram is an easily obtainable parameter with a significant prognostic impact in patients with congestive heart failure and a reduced EF. In this German subgroup of Val-HeFT patients, it was an independent predictor of all-cause mortality.     

Mechanical dyssynchrony assessed by tissue Doppler imaging is a powerful predictor of mortality in congestive heart failure with normal QRS duration.

OBJECTIVES: We sought to test whether the mechanical dyssynchrony assessed by tissue Doppler imaging (TDI) is a predictor of cardiac events in patients with congestive heart failure (CHF) and QRS duration < or =120 ms. BACKGROUND: The prevalence and prognostic value of mechanical dyssynchrony in patients with CHF and normal QRS duration have not been well clarified. METHODS: A total of 106 patients (age 63 +/- 11 years) with CHF and ejection fraction (EF) <35% were followed serially; TDI was performed using four basal and four mid-left ventricular segments to assess the time to peak systolic point from R-wave on electrocardiogram (Ts). The standard deviation of Ts (Ts-SD) and the maximal temporal difference of Ts (Ts-diff) of eight segments were used as an indicator of mechanical dyssynchrony. Clinical events included readmission due to worsening of CHF, cardiac transplantation, and death. RESULTS: After 17 +/- 11 months of follow-up, the clinical event rate was 33% including all-cause mortality of 19%. Prolonged Ts-SD (>37 ms) and Ts-diff (>91 ms) were associated with a significant increase in all clinical events. By multivariate analysis, Ts-diff (>91 ms) was an independent risk factor of clinical events and mortality regardless of age, EF, QRS duration, and use of beta-blocking agents. Mean event-free survival was 16.3 months (95% confidence interval [CI] 11.9 to 20.7) in patients with Ts-diff >91 ms and 31.6 months (95% CI 28.0 to 35.1) in those with Ts-diff < or =91 ms, respectively (p < 0.001). CONCLUSIONS: Myocardial dyssynchrony assessed by TDI is a powerful predictor of clinical events in CHF with normal QRS.     

心脏再同步治疗前后QRS波时限与疗效相关性

目的探讨QRS波时限对心脏再同步治疗（CRT）临床疗效的预测价值。方法入选心功能Ⅲ～Ⅳ级（NYHA分级）、左心室射血分数≤0．35、QRS波时限〉120ms患者,CRT治疗前后1周行心电图检查。随访6～12个月,以心功能分级改善I级以上或6rain步行试验距离增加25％以上作为临床有效的标准,死亡患者定义为无效,分析CRT治疗前后QRS波时限及QRS波时限缩短值对CRT临床疗效的预测价值。结果（1）共79例患者人选,57例（72．2％）临床有效;（2）CRT治疗后1周QRS波时限,治疗前后QRS波时限差值,治疗前舒张压、左心室收缩末内径和左心房内径,有效组和无效组之间差异有统计学意义（P〈0．05）;（3）受试者工作特征曲线显示CRT治疗后1周QRS波时限、治疗前后QRS波时限差值能预测CRT的疗效（P〈0．01）。结论CRT治疗后1周QRS波时限、治疗前后QRS波时限差值可以预测宽QRS波患者的CRT疗效。     

Ventricular arrhythmias in congestive heart failure: clinical significance and management

The benefit of defibrillator therapy has been well established for patients with LV dysfunction (ejection fraction less than 35%), coronary artery disease, NSVT, and inducible and nonsuppressible ventricular tachycardia. Implantable cardioverter-defibrillator therapy is also indicated for all CHF patients in NYHA functional classes I, II, and III who present with aborted sudden cardiac death, or ventricular fibrillation, or hemodynamically unstable ventricular tachycardia--and also in patients with syncope with no documented ventricular tachycardia but with inducible ventricular tachycardia at electrophysiology study. The ongoing MADIT II trial was designed to evaluate the benefit of prophylactic ICD implantation in these patients (ejection fraction less than 30%, coronary artery disease, and NSVT) without prior risk stratification by PES. The CABG Patch trial concluded that prophylactic placement of an ICD during coronary artery bypass grafting in patients with low ejection fraction and abnormal SAECG is not justifiable. Except for the indications described above, ICD implantation has not been proved to be beneficial as primary or secondary therapy. Until more data are available, patients should be encouraged to enroll in the ongoing clinical trials.     

心力衰竭加重并左室射血分数降低患者的QRS时限与预后

目的观察住院期间QRs时限对心力衰竭并左室射血分数降低预后的影响。方法回顾性分析心力衰竭并左室射血分数降低（≤40％）或正常的住院患者住院期间的QRs波群时限。结果3002例患者纳入研究,其中正常QRS波群时限1745例（〈120ms）,QRS波群延长（≥120ms）1257例。平均随访10个月,基础QRS波群时限正常患者全因死亡率为18．8％,基础QRS波群延长患者为28．3％（nR。1．62,95％CIL38～1．88）。基础QRS波群正常患者心血管死亡和心力衰竭住院率为31．5％和35．8％,延长者则为39．0％和43．6％（朋=1．40、1．42;95％CIL25-1．60、1．18-1．72）。QRS波群时限延长与增加全因死亡率危险性相关（HR=1．25：95％C11．03～1．52）,并增加心血管死亡或心力衰竭住院率（HR=1．21、1．28,95％CIL10～1．40、1．12～1．38）。基础Qas波群延长患者最后住院心电图QRS波群正常者仅为4．0％。结论延长的QRS波群在LVEF降低患者中十分多见,是出院后高患病率和高死亡率的独立预测因素。     

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.     

Sudden death prophylaxis in heart failure

Sudden cardiac death (SCD) is the leading cause of mortality in heart failure (HF). Today the implantable cardioverter-defibrillator (ICD) has become a commonplace therapy around the world for patients with both ischemic and non-ischemic cardiomyopathy and an ejection fraction (EF) < or = 35%. However, EF alone does not discriminate between the modes of death from HF (sudden arrhythmic death vs. non-sudden death). Other risk statifiers, such as electrophysiologic study and microvolt T-wave alternans testing, should therefore be used in the appropriate settings to minimize the number of unnecessary device implants. In addition, left ventricular mechanical dyssynchrony has now become recognized as an additional major marker of cardiac mortality. Its assessment should entail echocardiography rather than measurement of the QRS duration. This will allow us to better integrate the ability of cardiac resynchronization therapy (CRT) in enhancing cardiac function with the ability of an ICD in preventing SCD. This review aims to: 1) give a synthesis of the published evidence regarding the value of implantable ICDs and CRT in the primary prophylaxis of SCD in HF; 2) discuss controversial clinical issues in this area; and 3) recommend practical device-based management strategies.