A new paradigm for physiologic ventricular pacing

Clinical trials in patients with pacemakers for sinus node dysfunction or atrioventricular block (AVB) and implantable cardioverter-defibrillators provide increasing evidence showing that desynchronization of ventricular electrical activation and contraction, induced by conventional right ventricular apex (RVA) pacing, is a serious threat for long-term cardiac morbidity and mortality. The risk of heart failure is increased even in hearts with initially normal pump function and in case of part-time ventricular pacing. These epidemiologic data fit with knowledge from decades of pathophysiological research, indicating that right ventricular (RV) pacing creates abnormal contraction, reduced pump function, hypertrophy, and ultrastructural abnormalities. This paper presents a new paradigm that aims to tailor ventricular pacing to the individual patient to achieve a way of pacing that is as physiologic as possible. In patients without AVB and no intraventricular conduction abnormalities, ventricular pacing should be avoided as much as possible, using atrial-based pacing. In patients with AVB, alternate single-site RV or left ventricular pacing or biventricular pacing may be superior to RVA pacing. Efforts to optimize the pacing mode or site should be greater in patients with a longer expected duration of pacing, poorer cardiac function, and larger mechanical asynchrony. Awareness of the problem of desynchronization should also lead to more regular monitoring of cardiac pump function and mechanical asynchrony in any patient with ventricular pacing.     

Cardiac resynchronisation therapy versus dual site right ventricular pacing in a patient with permanent pacemaker and congestive heart failure.

A 46-year-old male patient who had long-term right ventricular (RV) pacing for symptomatic complete heart block, initially by an epicardial, later with an endocardial pacing lead at the RV apex, developed congestive heart failure (CHF) and chronic atrial fibrillation 7 years following the pacemaker implantation and was medically treated. During follow-up, his pacemaker was upgraded to a cardiac resynchronisation therapy (CRT) device, because of uncontrolled CHF symptoms, New York Heart Association (NYHA) functional class IV, while on drugs. The patient's symptomatic status improved to NYHA functional class II with CRT. After 17 months of CRT, the battery became depleted, because of the high capture threshold of the left ventricular lead. The patient was then given dual site RV pacing (RV outflow tract+RV apex) in place of CRT, which showed similar efficacy at 12 weeks follow-up.     

Analysis of ventricular performance as a function of pacing site and mode

Emerging data from experimental and clinical studies have shown that right ventricular (RV) apical pacing led to abnormalities of ventricular activation and contraction, and impairment of myocardial perfusion with adverse left ventricular (LV) remodeling, which was associated with increased risk of cardiac morbidity and mortality. As a result, there is a growing interest in searching for methods to minimize unnecessary RV pacing and preserving normal ventricular activation with alternative ventricular pacing sites. The risk of developing heart failure (HF) after RV apical pacing depends on the interactions between patient-specific factors (baseline atrial rhythm, intrinsic atrioventricular and ventricular conduction, LV ejection fraction, and the presence of HF and myocardial infarction) and pacing-related factors (mode of pacing, site of ventricular pacing, paced QRS duration, and percentage and duration of pacing). In patients with intact atrioventricular conduction, atrial-based pacing should be used to avoid unnecessary ventricular pacing. In patients requiring ventricular pacing, the potential benefits of alternate ventricular pacing sites, such as RV or LV septa, or even biventricular pacing in different patient populations remain unclear and warrant further long-term prospective clinical trial evaluations especially in those patients who are at a higher risk of developing HF after RV apical pacing.     

A new paradigm for physiologic ventricular pacing.

Clinical trials in patients with pacemakers for sinus node dysfunction or atrioventricular block (AVB) and implantable cardioverter-defibrillators provide increasing evidence showing that desynchronization of ventricular electrical activation and contraction, induced by conventional right ventricular apex (RVA) pacing, is a serious threat for long-term cardiac morbidity and mortality. The risk of heart failure is increased even in hearts with initially normal pump function and in case of part-time ventricular pacing. These epidemiologic data fit with knowledge from decades of pathophysiological research, indicating that right ventricular (RV) pacing creates abnormal contraction, reduced pump function, hypertrophy, and ultrastructural abnormalities. This paper presents a new paradigm that aims to tailor ventricular pacing to the individual patient to achieve a way of pacing that is as physiologic as possible. In patients without AVB and no intraventricular conduction abnormalities, ventricular pacing should be avoided as much as possible, using atrial-based pacing. In patients with AVB, alternate single-site RV or left ventricular pacing or biventricular pacing may be superior to RVA pacing. Efforts to optimize the pacing mode or site should be greater in patients with a longer expected duration of pacing, poorer cardiac function, and larger mechanical asynchrony. Awareness of the problem of desynchronization should also lead to more regular monitoring of cardiac pump function and mechanical asynchrony in any patient with ventricular pacing.     

Eliminating right ventricular pacing may not be best for patients requiring implantable cardioverter-defibrillators

BACKGROUND: Excessive right ventricular (RV) pacing has been associated with adverse clinical outcomes in patients receiving pacemakers or implantable cardioverter-defibrillators (ICDs). It remains uncertain how much RV pacing is clinically deleterious. OBJECTIVE: This retrospective analysis assessed the relationship between the amount of RV pacing and the composite of all-cause mortality and heart failure hospitalization in all patients programmed DDDR in the Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs (INTRINSIC RV) study. METHODS: Seven hundred fifteen patients consistently programmed to DDDR mode throughout follow-up (mean 11.6 months) were examined. The relationship between RV pacing tier and death and heart failure hospitalization was determined and compared with patient characteristics. RESULTS: Across the six RV pacing tiers, patients differed significantly with respect to age, clinical history of ventricular tachycardia, atrial fibrillation, and atrial flutter, and amiodarone use. When controlling for these baseline differences, the best outcome was seen in the group with RV pacing between 10% and 19% (2.8% event rate; n = 106). Increasing levels of RV pacing were generally predictive of higher event rates (death or heart failure hospitalization; P = 0.003), except for the group (n = 344) with the least amount of RV pacing (0-9%). This group exhibited poorer outcomes than otherwise expected (P = 0.016), with 8.1% of these patients experiencing an event. CONCLUSIONS: High levels of RV pacing are associated with heart failure hospitalization and mortality in a large ICD population. However, ICD patients with some RV pacing (10%-19%) exhibit lower event rates compared with those with very low levels (0-9%), possibly due to the physiologically appropriate nature of that RV pacing.     

Single-site ventricular and biventricular pacing: investigation of latest depolarization strategy.

Aims Cardiac resynchronization therapy with biventricular pacing has proved beneficial in symptomatic heart failure patients, yet the effects in patients with structurally normal hearts remain unknown. We hypothesized that, in an acute swine model with normal anatomy and function, single-site right ventricular (RV) pacing would better preserve haemodynamic function and electrical activation compared to biventricular pacing. Methods Endocardial single-site pacing was performed in anesthetized swine (n = 7) from the RV septum and RV apex. Biventricular pacing was performed using an epicardial left ventricular (LV) lead and a RV lead. High-resolution, non-contact mapping was employed to record LV activation sequences simultaneously with haemodynamic data after 5 min of consistent capture. Results All pacing interventions significantly prolonged QRS and total endocardial activation durations (P < 0.05) compared to intrinsic activation. Biventricular pacing with the RV apex lead significantly impaired LV systolic mechanics (dP/dt(max), max LV pressure; P < 0.05), and reduced LV relaxation to the greatest extent (dP/dt(min), P = ns). Right ventricular septal pacing conserved function better than other pacing interventions (P = ns) and elicited an intrinsic electrical activation sequence. Conclusion In intact, synchronous hearts, acute biventricular pacing resulted in systolic dysfunction and abnormal LV electrical activation.     

Adverse effects of right ventricular pacing on cardiac function: prevalence,prevention and treatment with physiologic pacing

Right ventricular (RV) pacing is the main treatment modality for patients with advanced atrioventricular (AV) block. Chronic RV pacing can cause cardiac systolic dysfunction and heart failure (HF). In this review, we discuss studies that have shown deleterious effects of chronic RV pacing on systolic cardiac function causing pacing-induced cardiomyopathy (PiCM), heart failure (HF), HF hospitalization, atrial fibrillation (AF) and cardiac mortality. RV apical pacing is the most widely used and studied. Adverse effects of RV pacing appear to be directly related to pacing burden and are worse in patients with pre-existing left ventricular (LV) dysfunction. Chronic RV pacing is also associated with heart failure with preserved ejection fraction (HFpEF). Mechanisms, risk factors, clinical and echocardiographic features, and strategies to minimize RV pacing-induced cardiac dysfunction are discussed in light of the latest data. Studies on biventricular (Bi-V) pacing upgrade in patients who develop RV PiCM, use of alternate RV pacing sites, de novo Bi-V pacing, and physiologic pacing using HIS bundle pacing (HBP) and left bundle area (LBBA) pacing in patients with an anticipated high RV pacing burden are discussed.     

Transoesophageal left ventricular pacing in heart failure patients with permanent right ventricular pacing.

BACKGROUND: Previous studies of biventricular (BV) pacing for treatment of heart failure (HF) patients with left bundle branch block (LBBB) evaluated responders to BV pacing with acute transvenous left ventricular (LV) pacing and arterial pulse pressure (PP). The aim of this study was to assess transoesophageal LV pacing in evaluation of the haemodynamic response with a view to upgrading responders from permanent right ventricular (RV) pacing to BV pacing. METHODS AND RESULTS: Ten HF patients (age 62+/-8 years; one female, nine males) in NYHA III, LV ejection fraction 24+/-9% and permanent RV pacing by means of an implanted pacemaker or ICD were tested using transoesophageal LV pacing and PP. Permanently RV-paced HF patients were analysed with transoesophageal atrial sensed LV pacing in VAT mode with a different AV delay (n = 6) and with transoesophageal LV pacing in V00 mode during atrial fibrillation (n = 4). In five responders, PP was higher during transoesophageal LV pacing than PP during RV pacing (74+/-42 versus 57+/-31 mmHg, P = 0.015). Responders were upgraded by means of an LV lead via the coronary sinus in the posterior (n = 1) or posterolateral (n = 4) walls and after attaining a high LV pacing threshold with an epicardial LV lead on the anterior (n = 1) or anterolateral (n = 1) walls. NYHA class improved from 3 to 2+/-0.3 (P = 0.003) during 204+/-120 days follow-up and cardiac output increased from 4.4+/-1.5 to 5.6+/-1.7 l/min (P = 0.027) when comparing BV pacing and optimal AV delay with RV pacing. In five nonresponders, PP was not higher during transoesophageal LV pacing than during RV pacing. CONCLUSION: Transoesophageal LV pacing may be a useful technique to detect responders to BV pacing in permanently RV-paced HF patients.     

Upgrade to biventricular pacing in patients with pacing-induced heart failure: can resynchronization do the trick?

Dyssynchrony imposed on ventricular function by right ventricular (RV) apical pacing may lead in some cases to worsening or appearance of heart failure (HF) symptoms. This is a result of an altered pattern of activation, leading to several histological and functional adjustments of the left ventricle, including inhomogeneous thickening of the ventricular myocardium and myofibrillar disarray, fibrosis, disturbances in ion-handling protein expression, myocardial perfusion defects, alterations in sympathetic tone and mitral regurgitation. Studies of mid- and long-term effects of RV apical pacing on left ventricular (LV) function have demonstrated a progressive decline in ejection fraction and other indices of LV functional competence. Upgrading RV pacing systems to biventricular resynchronization modalities is a theoretically promising option for paced patients with worsening HF. The potentially favourable effect of upgrading on LV functional indices and patient clinical status has been demonstrated in few, non-randomized trials. Apart from the scantiness of existing clinical data, issues concerning technical aspects of the procedure and selection of eligible patients are raised. Is pacing-induced dyssynchrony equivalent to the indigenous dyssynchrony in unpaced patients with HF? What selection criteria should be applied in order to identify potential responders to cardiac resynchronization therapy in this patient population? Answers to these and more questions are still lacking.     

Acute hemodynamic effects of right ventricular pacing site and pacing mode in patients with congestive heart failure secondary to either ischemic or idiopathic dilated cardiomyopathy

The hemodynamic effects of pacing in patients with congestive heart failure (CHF) remain controversial. Early studies reported that pacing from the right ventricular (RV) apex improved acute hemodynamic parameters in patients with left ventricular systolic dysfunction, but these findings were not confirmed in subsequent controlled studies. More recently, it has been proposed that pacing from the RV side of the ventricular septum improves hemodynamic function compared with intrinsic conduction or apical pacing. Either dual-chamber or ventricular pacing have been evaluated, again with inconsistent findings. To assess the effects of pacing site and mode on acute hemodynamic function, we evaluated 21 subjects with CHF and intrinsic conduction disease. Hemodynamics were compared in AAI, VVI, and DDD modes with pacing from the RV apex or high septum. The pacing rate was constant in each patient and the order of testing was randomized. In the absence of ventricular pacing (AAI mode), the mean systemic arterial pressure was 85 +/- 11 mm Hg, the right atrial pressure was 11 +/- 4 mm Hg, the pulmonary capillary wedge pressure was 18 +/- 8 mm Hg and the cardiac index was 2.4 +/- 0.7 L/min/m(2). Compared with AAI pacing, there were no improvements in any hemodynamic parameter with DDD pacing from either RV site. Hemodynamic function worsened with VVI pacing from both RV sites. Subgroup analyses of patients with dilated cardiomyopathy, with prolonged PR interval, or with significant mitral regurgitation also failed to demonstrate an improvement with pacing. We conclude that pacing mode but not RV pacing site affects acute hemodynamic function. Pacing in the DDD mode prevents the deleterious effects of VVI pacing in this patient population.     

Safe right bundle branch block pattern during permanent right ventricular pacing

It is known that an electrocardiogram (ECG) after transvenous right ventricular (RV) pacing should yield left bundle branch block (LBBB) QRS patterns. When right bundle branch block (RBBB) pacing morphology appears in a patient with a permanent or temporary transvenous RV pacemaker, myocardial perforation or malposition of the pacing lead must be ruled out, even though the patient may be asymptomatic. We report a case of a 77-year-old man who underwent permanent transvenous VDD pacemaker implantation for symptomatic heart block. The postoperative ECG revealed a RBBB pacing configuration, but his chest X-ray and echocardiographic studies confirmed uncomplicated RV pacing. We review and discuss the literature concerning the differential diagnosis of such a safe RBBB ECG pattern.     

Selective site pacing from the right ventricular mid-septum. Follow-up of lead performance and procedure technique

Pacing from the right ventricular (RV) apex is associated with adverse effects such as heart failure and atrial fibrillation. We attempted pacing from the RV mid-septum, which is theoretically a more physiological pacing site. A total of 172 consecutive patients with indications for permanent pacemaker implantation were studied. A screw-in lead and a curved stylet were used for lead positioning on the RV mid-septum. Pacemaker indices were evaluated at implantation and one year later. As an electrocardiographic parameter, QRS duration was measured in lead II. These data were compared to those of 66 patients subjected to conventional RV apical pacing. Lead placement was successful in all patients of RV mid-septal pacing. There were no technical problems during or after the procedure. The cumulative percentage of ventricular pacing at one year postimplantation was 85 ± 24 % in the SSP group. Sensing, pacing threshold, and lead impedance in the SSP group remained clinically stable over one year. When these measurements were compared between the SSP and AP groups, the pacing threshold and the lead impedance at one year postimplantation in the SSP group were higher (P < 0.05) and lower (P < 0.01), respectively, than those of the AP group. The mean QRS duration was markedly shorter (123 ± 16 versus 150 ± 18 msec, P < 0.0001). Selective site pacing from the RV mid-septum is feasible and results in less conduction delay compared to conventional RV apical pacing, and its procedure seems to be more physiological in permanent pacemaker implantation.     

Long-term transvenous AV-sequential pacing in a failing atriopulmonary Fontan patient

We report on a 32-year-old man with tricuspid atresia, pulmonary stenosis and hypoplastic right ventricle. He had received a Fontan-Kreutzer procedure (anastomosis between the right atrial appendage and the pulmonary artery) at the age of 14 years. At the age of 2 years, an abdominal VVI-pacemaker with an epicardial ventricular lead had been implanted because of symptomatic third degree AV-block. The patient was now hospitalized with symptoms of severe congestive heart failure. A least invasive approach restoration of AV-synchrony by a dual chamber pacer was performed. Therefore a complete transvenous approach to avoid thoracotomy was attempted. A specially designed CS lead was advanced via the CS to a left lateral ventricular vein for ventricular stimulation. After institution of dual chamber pacing the patient recovered of his heart failure. During a follow-up time of 20 months the patient was clinically stable in the AV-sequential pacing. Conclusion: Dual chamber pacing using a transvenously placed coronary sinus lead for ventricular stimulation may improve congestive heart failure in patients after the classic Fontan operation. The minimally invasive transvenous approach might be the best solution for patients who need a pacemaker and are not candidates for surgery or heart transplantation.     

Acute and chronic haemodynamic effects of biventricular pacing and of switching to different pacing modalities in heart failure patients

BACKGROUND: In patients with severe heart failure, sinus rhythm and wide QRS complex biventricular (BiV) pacing leads to clinical and haemodynamic improvement, but the immediate reversibility of these changes is not known. METHODS: We assessed the acute and medium-term (3-month) haemodynamic effects of BiV pacing and of switching to other pacing modalities in 21 patients with severe heart failure, sinus rhythm and QRS>or=130 ms. Haemodynamic studies were performed: 1) at the time of implantation of a BiV pacing device, during AAI pacing, atrial synchronous right ventricular (RV) pacing, atrial synchronous left ventricular (LV) pacing and atrial synchronous BiV pacing (all at 100 bpm); 2) after 3 months of continuous BiV pacing--with evaluations being made by switching to RV and the other pacing modalities. RESULTS: At both the acute and medium-term evaluations, BiV pacing provided the greatest improvement in cardiac index. Switching from BiV to RV pacing led to a more marked decrease in the cardiac index at 3 months. No strict correlation was evident between acute and medium-term effects of BiV pacing on cardiac index. CONCLUSION: Cardiac resynchronization by BiV pacing provides acute/medium-term improvements in cardiac index. Sudden, medium-term failure of LV stimulation can lead to an even more pronounced haemodynamic derangement than that inducible by RV pacing at baseline. Acute haemodynamic evaluations do not seem to provide a powerful way for identifying medium-term responders.     

Cardiac resynchronization in patients with congestive heart failure and chronic atrial fibrillation: effect of upgrading to biventricular pacing after chronic right ventricular pacing

OBJECTIVES: This study assessed the effects of biventricular pacing (BVP) on ventricular function, functional status, quality of life and hospitalization in patients with congestive heart failure (CHF), prior atrioventricular (AV) junction ablation and right ventricular (RV) pacing performed for chronic atrial fibrillation (AF). BACKGROUND: Although the benefit of BVP in CHF should theoretically extend to the patient with chronic RV pacing and AF, to our knowledge, no study has determined the effects of BVP on symptoms and ventricular function in these patients. This patient population allows for the evaluation of ventricular resynchronization independent of any BVP-induced changes on the AV interval. METHODS: Twenty consecutive patients with severe CHF (ejection fraction < or = 0.35, New York Heart Association [NYHA] functional class III or IV), prior AV junction ablation and RV pacing performed for permanent AF of at least six months' duration were studied. Electrocardiograms, echocardiograms, functional status evaluations and quality of life surveys were completed before and at three to six months after implant. RESULTS: The NYHA functional classification improved 29% (p < 0.001). The left ventricular (LV) ejection fraction increased 44% (p < 0.001), the LV diastolic diameter decreased 6.5% (p <0.003) and the end-systolic diameter decreased 8.5% (p < 0.01). The number of hospitalizations decreased by 81% (p < 0.001). The scores on the Minnesota Living with Heart Failure survey improved by 33% (p < 0.01). CONCLUSIONS: We conclude that BVP improves the LV function and the symptoms of CHF in patients with permanent AF and chronic RV pacing. These benefits are comparable to those described for patients in sinus rhythm suggesting that BVP acts through ventricular resynchronization rather than optimization of the AV delay.     

Ventricular septal pacing: Optimum method to position the lead

Adverse hemodynamics of right ventricular (RV) pacing is known for years. Several studies have revealed that adverse outcomes of RV apical pacing are directly linked to cumulative percentage of ventricular pacing. Algorithms to minimize ventricular pacing are only effective if there is good atrioventricular (AV) conduction. A need for an alternate site for ventricular pacing is evident in patients with high presumed ventricular pacing burden. Most studied alternate site for ventricular pacing is ventricular septum (outflow tract septum and mid-septum). Conventionally septal position of the ventricular pacing lead is confirmed by fluoroscopic appearance of the lead and characteristics electrocardiographic (ECG) features. However, several recent studies have challenged these fluoroscopic and ECG features as to be inadequate. So, there is need for a systematic approach for septal positioning of the ventricular lead.     

Clinical and procedural characteristics of acute hemodynamic responders undergoing triple-site ventricular pacing for advanced heart failure

The advantages of triple-site ventricular pacing (Tri-V) compared to conventional biventricular site pacing (Bi-V) have been reported. We sought to identify the predictors of acute hemodynamic Tri-V responders. Acute hemodynamic studies were performed in 32 patients with advanced heart failure during Tri-V implantation. After the right ventricular (RV) and left ventricular (LV) leads were implanted for a conventional Bi-V system, an additional pacing lead was implanted in the RV outflow tract for Tri-V. The LV peak +dP/dt and tau were measured during AAI, Bi-V, and Tri-V pacing. A Tri-V responder was defined as a patient whose percentage of increase in the peak +dP/dt during Tri-V was >10% compared to of that during Bi-V. The baseline clinical variables and RV outflow tract lead location were analyzed to identify the characteristics of the Tri-V responders. Of the 32 patients, 10 (31%) were classified as Tri-V responders. The LV end-diastolic volume was greater (246 ± 48 vs 173 ± 53 ml, p <0.01), and the RV outflow tract lead was implanted at a greater outflow tract portion (p <0.05) in the Tri-V responders. Multivariate analysis revealed that only the baseline LV end-diastolic volume (per 50-ml greater) predicted the Tri-V response (odds ratio 2.87, 95% confidence interval 1.03 to 8.00, p <0.05). The area under the receiver operating characteristic curve for the LV end-diastolic volume was 0.84 (p <0.01) and an LV end-diastolic volume of >212 ml had a sensitivity of 80% and specificity of 77% to distinguish Tri-V responders. In conclusion, Tri-V provides greater hemodynamic effect for patients with a larger LV end-diastolic volume owing to its resynchronization effects on the LV anterior wall.     

Reversible left ventricular dyssynchrony and heart failure induced by right ventricular pacing

Right ventricular (RV) pacing related heart failure is reported in some patients after long term pacing. The exact mechanism is not yet clear but may be related to left ventricular (LV) dyssynchrony induced by RV apical pacing. We report one case with baseline normal LV ejection fraction but complicated by heart failure and ventricular tachycardia after 4 months of pacing for complete heart block together with illustration of LV dyssynchrony demonstrated by tissue Doppler imaging.     

Chronic right ventricular apical pacing: Adverse effects and current therapeutic strategies to minimize them

The permanent cardiac pacemaker is the only effective therapy for patients with symptomatic bradycardia and hundreds of millions are implanted worldwide every year. Despite its undisputed clinical benefits, the last two decades have drawn much attention to the negative effects associated with long-term pacing of the right ventricle (RV). Experimental and clinical studies have shown that RV pacing produces ventricular dyssynchrony, similar to that of left bundle branch block, with consequent detrimental effects on cardiac structure and function, with adverse clinical outcomes such as atrial fibrillation, heart failure and death. Although clinical evidence largely comes from subanalyses of pacemaker and implantable cardiac defibrillator studies, there is strong evidence that patients with reduced left ventricular function are at high risk of suffering from the detrimental effects of long-term RV pacing. Biventricular pacing in cardiac resynchronization therapy devices can prevent ventricular dyssynchrony and has emerged as an attractive option in this patient group with promising results and more clinical studies underway. Moreover, there is evidence that specific pacemaker algorithms that minimize RV pacing can reduce the negative effects of RV stimulation on cardiac function and may also prevent clinical deterioration. The extent of the long-term clinical effects of RV pacing in patients with normal ventricular function and how to prevent this are less clear and subject to future investigation.     

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.