Leadless pacemaker versus transvenous single-chamber pacemaker therapy: A propensity score-matched analysis.

BACKGROUND: The recent introduction of leadless pacemakers (PMs) was aimed to eliminate transvenous lead- and pocket-related complications. While the initial results with the leadless PMs seem promising, the nonrandomized nature, limited implant experience of operators, and short follow-up period of these studies preclude a simple comparison to transvenous PMs. OBJECTIVES: The objective of this study was to provide a balanced comparison of leadless and transvenous single-chamber PM therapies through a propensity score-matched analysis. METHODS: Leadless patients from 3 experienced leadless implant centers were propensity score-matched to VVI-R patients from a contemporary prospective multicenter transvenous PM registry. The primary outcome was device-related complications that required invasive intervention during mid-term follow-up. Separate analyses including and excluding PM advisory-related complications were performed. RESULTS: A total of 635 patients were match-eligible (leadless: n = 254; transvenous: n = 381), of whom 440 patients (median age 78 years; interquartile range 70-84 years; 61% men) were successfully matched (leadless: n = 220 vs transvenous: n = 220). The complication rate at 800 days of follow-up was 0.9% (95% confidence interval [CI] 0%-2.2%) in the leadless group vs 4.7% (95% CI 1.8%-7.6%) in the transvenous group when excluding PM advisory-related complications (P = .02). When including these PM advisory-related complications, the complication rate at 800 days increased to 10.9% (95% CI 4.8%-16.5%) in the leadless group vs 4.7% (95% CI 1.8%-7.6%) in the transvenous group (P = .063). CONCLUSION: This study reveals favorable complication rates for leadless compared to transvenous single-chamber pacing therapy at mid-term follow-up in a propensity score-matched cohort. When including PM advisory-related complications, this advantage is no longer observed.

Risk of heart failure- and cardiac death gradually increases with more right ventricular pacing.

BACKGROUND: Right ventricular pacing (RVP) is associated with an increased risk of heart failure (HF) events. However, the extent and shape of this association is hardly assessed. OBJECTIVE: We quantified whether the undesired effects of RVP are confirmed in an unselected population of first bradycardia pacemaker recipients. Furthermore, we studied the shape of the association between RVP and HF death and cardiac death. METHODS: Cumulative percentage RVP (%RVP) was measured in 1395 patients. Using multivariable Cox regression analysis with %RVP as time-dependant co-variate we evaluated the association between %RVP and HF- and cardiac death, both unadjusted and adjusted for confounders, including age, gender, pacemaker-indication, cardiac disease, HF at baseline, diabetes, hypertension, atrio-ventricular synchrony, usage of beta-blocking drugs, anti-arrhythmic medication, HF medication, and prior atrial fibrillation/flutter. Non-linear associations were evaluated with restricted cubic splines. RESULTS: During a mean follow-up of 5.8 (SD 1.1) years 104 HF deaths and 144 cardiac deaths were observed. %RVP was significantly associated with HF- and cardiac death in both unadjusted (p<0.001 and p<0.001, respectively) and adjusted analyses (p=0.046 and p=0.009, respectively). Our results show a linear association between %RVP and HF- and cardiac death. We observed a constant increase of 8% risk of HF death per 10% increase in RVP. A model incorporating various non-linear transformations of %RVP using restrictive cubic splines showed no improved model fit over linear associations. CONCLUSION: This long-term, prospective study observed a significant, though linear association between %RVP and risk of HF death and/or cardiac death in unselected bradycardia pacing recipients.

Prognosis of the bradycardia pacemaker recipient assessed at first implantation: a nationwide cohort study.

OBJECTIVE: Pacing technology and care have improved notably over the past decade, justifying an update on the long-term prognosis and pre-implantation determinants of prognosis of bradycardia pacemaker (PM) recipients. DESIGN: Prospective cohort study. SETTING: 23 Dutch pacemaker centres PATIENTS: Pre-implantation characteristics of 1517 patients receiving a first bradycardia PM between 2003-2007 were studied in relation to survival. INTERVENTIONS: None; patients were followed up during routine clinical practice. MAIN OUTCOME MEASURES: Cause and time to death. RESULTS: At the end of a mean follow-up of 5.8 (SD 1.1) years, 512 patients (33%) died, mostly of non-cardiac cause (67%). There were two PM related deaths. Survival rates were 93%, 81%, 69%, and 61% after 1, 3, 5 and 7 years, respectively. PM recipients without concomitant cardiovascular disease at implantation showed survival rates comparable to age and sex matched controls. Predictors at time of implantation associated with cardiac mortality were: age, coronary artery disease (CAD), diabetes, heart failure, valve disease, and the indication for PM implantation. Predictors for all cause mortality were: male gender, age, body mass index, CAD, cardiac surgery, diabetes, heart failure, and maintained atrioventricular synchrony. CONCLUSIONS: A pre-implantation history of heart failure, CAD, and diabetes are the most important predictors for worse prognosis in PM recipients. Without baseline heart disease, survival rates equal that of the general population, suggesting that the prognosis of contemporary PM recipients is mainly determined by comorbid diseases and a bradycardia pacing indication as such does not influence survival. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00135174.

Long term quality-of-life in patients with bradycardia pacemaker implantation.

BACKGROUND: Health-related quality of life (HRQoL) values shortly after pacemaker (PM) implantation for bradycardia have been established, however little is known about long-term HRQoL. METHODS: Using the generic SF-36 and the PM specific Aquarel questionnaire, HRQoL was repeatedly measured during a 7.5 year follow-up period in 881 bradycardia PM recipients included in the large scale nationwide Dutch FOLLOWPACE study. HRQoL over time, corrected for age, gender, diabetes, hypertension, heart failure, cardiovascular disease and AV-synchrony, was assessed with a linear mixed model. RESULTS: Increased scores both on overall SF-36 and on all SF-36 subscales were observed shortly after implantation. Although scores on SF-36 gradually declined over time, scores remained improved over the measured pre-implantation values. Also, scores for almost all subscales remained increased throughout the 7.5 year observation period, except for physical functioning which showed a gradual decline several years after the initial rise. Additionally, higher scores on all Aquarel scales were observed after implantation. Scores on the arrhythmias and chest discomfort subscales improved and remained stable throughout follow-up (FU), whereas the dyspnea at exertion subscale showed a gradual decline during FU to reach pre-implantation values at 5 years. CONCLUSIONS: Increased HRQoL is observed not only shortly after PM implantation, but also after long-term FU. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00135174; http://www.clinicaltrials.gov/ct2/show/NCT00135174.

Incidence and predictors of pacemaker reprogramming: potential consequences for remote follow-up.

AIMS: Remote follow-up (FU) enables to cope with the expanding number of pacemaker (PM) FU. Although remote FU offers comparable monitoring options to in-office FU, reprogramming of device settings is not available, thereby imposing a potentially important restriction to the applicability of remote FU.  The aim of this study was to assess in a large cohort of bradycardia PM recipients, the incidence of PM reprogramming during long-term FU and its predictors, to judge the possibilities for remote FU. METHODS AND RESULTS: Between 2003 and 2010 all in-office FU of 1517 bradycardia PM recipients included in the FOLLOWPACE study were recorded. Only 24.5% of all 13 258 recorded FU visits >3 months after implantation were visits-with-reprogramming (VWRs), occurring in 1158 patients (79%). Fifty percent of patients were free of reprogramming at 9 months, and 29% at 24 months. Using multivariable binary logistic regression analysis, the following patient characteristics were predictive for frequent PM reprogramming, defined as >3 VWRs during 3 year FU: age, a history of atrial arrhythmias, PM complication <3 months after implantation, congestive heart failure, PM indication, and lead fixation method. This model had a receiver operating characteristic area of 0.66 (95% confidence interval 0.61-0.71). CONCLUSION: This study observed a low proportion of VWR (∼25%) during a mean FU of 5.3 years; however, those patients at high risk for PM reprogramming cannot easily be predicted. The vast majority of patients (>80%) do not need frequent reprogramming, suggesting a potential benefit of using remote FU to reduce the number of unnecessary in-office visits.

Pacemaker follow-up: are the latest guidelines in line with modern pacemaker practice?

AIMS: Guidelines regarding pacemaker (PM) follow-up (FU) are not precisely defined. The study aim is to describe long-term routine in-hospital FU, evaluate compliance to guidelines, and assess the portion of visits-with-an-action (VWA). METHODS AND RESULTS: The multicentre prospective FOLLOWPACE study collected data in the period 2003-2010, regarding FU of 1517 patients with a first PM for bradycardia indications in 23 Dutch hospitals. A total of 15 472 visits were analysed with a median FU of 4.9 years, adding up to 6750 patient years. The median time to the first three visits was 35, 127, and 303 days, respectively. Thereafter the median interval between visits was 180 days. Most patients had 2 FU/year, 22% had 1 FU/year, and 18% had >3 FU/year. Seventy-three percent of patients with single-chamber PMs had at least 1 FU/year, whereas 36% of patients with dual-chamber PMs received at least 2 FU/year. During the first year, 52% of visits were VWA, as opposed to 17% after 6 years. Battery status was assessed in 98%, and stimulation and sensing thresholds in 90% and 77% of visits, respectively. Reprogramming markedly declined from ≈ 60% in the first FU visit to 10-20% after the fifth visit. CONCLUSION: Although the measurements during PM FU are according to guidelines, the frequency of FU is not. Moreover, in the vast majority of performed FU, PM programming is left unchanged. This suggests that a large portion of FU visits is redundant, such that their frequency after the first year can be diminished, or replaced by remote FU.

Incidence and predictors of short- and long-term complications in pacemaker therapy: the FOLLOWPACE study.

BACKGROUND: Today quantitative information about the type of complications and their incidence during long-term pacemaker (PM) follow-up is scarce. OBJECTIVE: To assess the incidence and determinants of short- and long-term complications after first pacemaker implantation for bradycardia. METHODS: A prospective multicenter cohort study (the FOLLOWPACE study) was conducted among 1517 patients receiving a PM between January 2003 and November 2007. The independent association of patient and implantation-procedure characteristics with the incidence of PM complications was analyzed using multivariable Cox regression analysis. RESULTS: A total of 1517 patients in 23 Dutch PM centers were followed for a mean of 5.8 years (SD 1.1), resulting in 8797 patient-years. Within 2 months, 188 (12.4%) patients developed PM complications. Male gender, age at implantation, body mass index, a history of cerebrovascular accident, congestive heart failure, use of anticoagulant drugs, and passive atrial lead fixation were independent predictors for complications within 2 months, yielding a C-index of 0.62 (95% confidence interval 0.57-0.66). Annual hospital implanting volume did not additionally contribute to the prediction of short-term complications. Thereafter, 140 (9.2%) patients experienced complications, mostly lead-related complications (n = 84). Independent predictors for long-term complications were age, body mass index, hypertension, and a dual-chamber device, yielding a C-index of 0.62 (95% confidence interval 0.57-0.67). The occurrence of a short-term PM complication was not predictive of future PM complications. CONCLUSIONS: Complication incidence in modern pacing therapy is still substantial. Most complications occur early after PM implantation. Although various patient- and procedure-related characteristics are independent predictors for early and late complications, their ability to identify the patient at high risk is rather poor. This relatively high incidence of PM complications and their poor prediction underscores the usefulness of current guidelines for regular follow-up of patients with PM.

Increased amount of atrial fibrosis in patients with atrial fibrillation secondary to mitral valve disease.

OBJECTIVE: Atrial fibrosis is related to atrial fibrillation but may differ in patients with mitral valve disease or lone atrial fibrillation. Therefore, we studied atrial fibrosis in patients with atrial fibrillation+mitral valve disease or with lone atrial fibrillation and compared it with controls. METHODS: Left and right atrial appendages amputated during Maze III surgery for lone atrial fibrillation (n=85) or atrial fibrillation+mitral valve disease (n=26) were embedded in paraffin, sectioned, and stained with picrosirius red. Atria from 10 deceased patients without a cardiovascular history served as controls. A total of 1048 images (4-µm sections, 10-fold magnification, 4 images per appendage) were obtained and digitized. The percentage of fibrous tissue was calculated by quantitative morphometry. RESULTS: Irrespective of the presence or absence of atrial fibrillation or mitral valve disease, more fibrous tissue was present in right atrial appendages than in left atrial appendages (12.7%±5.7% vs 8.2%±3.9%; P<.0001). The mean amount of fibrous tissue in the atria was significantly larger in patients with atrial fibrillation+mitral valve disease than in patients with lone AF and controls (13.6%±5.8%, 9.7%±3.2%, and 8.8%±2.4%, respectively; P<.01). No significant differences existed between patients with lone atrial fibrillation and patients without a cardiovascular history (controls). CONCLUSIONS: Atria of patients with atrial fibrillation and mitral valve disease have more fibrosis than atria of patients with lone atrial fibrillation. However, patients with lone atrial fibrillation have an equal amount of atrial fibrosis compared with controls. These findings support the notion that fibrosis plays a more important role in the pathogenesis of atrial fibrillation secondary to mitral valve disease than in lone atrial fibrillation and potentially explains the relatively poor success of antiarrhythmic surgery in patients with mitral valve disease.

Long-term outcome of cardiac pacing in octogenarians and nonagenarians.

AIMS: The number of patients >80 years receiving pacemakers (PMs) is increasing. Little is known about survival and complications in this specific subgroup. We aim to determine predictors of long-term survival. METHODS AND RESULTS: Pacemaker-related complications and death occurring in patients receiving a first PM for conventional bradycardia indications were systematically documented (the FollowPace registry). This report describes 481 patients ≥80 years during a mean follow-up of 5.8 (SD 1.2) years. Within 2 months 54 PM complications occurred in 47 patients (9.8%). During follow-up, 35 adverse PM events were reported in 33 patients (6.9%). Complication rates in patients ≥80 years were comparable with those for patients <80 years. Survival rates were 86, 75, and 49% after 1, 2, and 5 years, respectively, and were comparable with survival for age- and sex-matched controls from the general Dutch population. Most patients died of non-cardiac causes. Age at the time of implantation, male gender, the presence of congestive heart failure, coronary pathology, and diabetes mellitus were independent predictors of all-cause mortality. CONCLUSION: This large study of long-term cardiac pacing for bradycardia in octogenarians and nonagenarians showed a cumulative 5-year survival of ~50%, which compares with that of age- and sex-matched controls. These data suggest a beneficial impact of bradycardia pacing, restoring life expectancy to previous levels. The occurrence of PM complications during long-term follow-up is not infrequent with 18.1% of patients experiencing a PM-related complication during a mean of 5.8 years follow-up. The complication rate was not higher than in younger PM patients.

Is antiarrhythmic treatment in the elderly different? a review of the specific changes.

Aging is associated with electrical and structural changes of the myocardium. The response to catecholamines is also reduced and the baroreceptor reflex activity is blunted. These aspects conceivably affect the response to antiarrhythmic drugs in the elderly. Furthermore, physiological parameters change in older age, affecting the pharmacokinetics of drugs. In this article, the literature on the pharmacokinetics and pharmacodynamics of antiarrhythmic drugs in elderly subjects is reviewed with the purpose of improving their optimal and safe prescription. Pharmacokinetic studies of antiarrhythmic drugs in the elderly are sparse, and there are no data available for procainamide and propafenone. Mean dose reductions calculated for elderly patients relative to younger patients are 60% for digoxin, 19% for diltiazem, 32% for disopyramide, 31% for flecainide, 40% for metoprolol, 35% for quinidine, 29% for sotalol and 26% for verapamil. No dose reductions are required for dofetilide or dronedarone. The clearance of dofetilide is not affected by age after correction for renal function. The dosage of dofetilide is individualized according to an algorithm based on the corrected QT (QTc) interval and renal function. Although the area under the plasma concentration-time curve (AUC) for dronedarone is larger in elderly patients, the dose should not be reduced because the registered dose has specifically been studied in an elderly population. In elderly patients with renal insufficiency, hepatic impairment, heart failure or certain genetic variants, the pharmacokinetics of antiarrhythmic drugs might be affected to an even greater extent, meaning additional dosage adjustments are necessary. With increasing age, the number of prescribed drugs increases because of co-morbidity, making interactions between drugs more likely. Several drugs interact with antiarrhythmic drugs, leading to clinically relevant changes in drug concentrations or AUC values. Furthermore, several drugs with non-cardiovascular indications appear to have QTc prolonging effects. The combination of these drugs with antiarrhythmic drugs that affect the QTc interval increases the risk of developing torsades de pointes and should therefore be avoided. Altered effects of drugs in the elderly can also be the result of age-related changes in the cardiovascular system. For example, atenolol and sotalol show greater effects, i.e. reductions in heart rate and increased probability of adverse effects, at a given plasma concentration in older subjects compared with younger subjects. It remains unclear whether old age as such is a determinant for reduced or modified efficacy of antiarrhythmic drugs. In a randomized study it was found that patients aged ≥65 years with atrial fibrillation had better survival with rate control than with rhythm control. However, different treatment strategies were compared and the results cannot be extrapolated to indicate better survival with a specific antiarrhythmic drug. Antiarrhythmic drugs will remain the first-line approach in most patients for the prevention or suppression of atrial and ventricular arrhythmias. As a rule of thumb, a 50% reduction in the starting dose of antiarrhythmic drugs compared with younger patients appears a wise approach in elderly patients. However, this does not apply to dofetilide and dronedarone. The selection of antiarrhythmic drugs in the elderly is predominantly determined by factors such as the treatment target, assumed patient compliance, possible drug interactions, co-morbidity, and renal and liver function. Efficacy and safety monitoring should take into account symptoms, ECG findings, rhythm recordings, plasma drug concentrations and other laboratory parameters.

Effects of pacing rates on global and regional myocardial blood flow.

BACKGROUND: Information is scarce on the effects of right ventricular apical (RVA) pacing on regional and global myocardial blood flow (MBF). The purpose of this study was to assess the relationship between pacing rate and both regional and global MBF. METHODS: Four patients with exclusive atrial pacing and six patients with exclusive RVA pacing underwent three consecutive H(2) (15)O positron emission tomography scans at 60, 90, and 130 pulses per minute (ppm). For each pacing rate, regional and global MBF was determined. In all patients, the left ventricular (LV) function was normal. RESULTS: By varying the atrial pacing rate from 60 to 130 ppm, the mean global MBF increased from 0.94 to 1.40 mL/g/min, whereas the mean septal to lateral MBF ratio decreased from 1.09 to 0.83. In ventricular-paced patients at corresponding rates, the mean global MBF also increased from 1.07 to 1.52 mL/g/min but here the mean septal to lateral MBF ratio increased from 0.83 to 1.0. CONCLUSIONS: During both acute atrial and RVA pacing, regional and global MBF increases with higher pacing rates. However, the septal to lateral MBF ratio decreases with atrial pacing and increases with RVA pacing in patients with normal LV function. In RVA pacing, these different rate-dependent effects on regional MBF can be considered as a favorable factor that helps to understand why in some long-term paced patients, LV function is preserved.

Upgrading to biventricular pacing guided by pressure-volume loop analysis during implantation.

INTRODUCTION: cardiac resynchronization therapy (CRT) may improve prognosis in patients with chronic right ventricular (RV) pacing, and optimal lead position can decrease nonresponders. We evaluated the clinical and echocardiographic response to CRT in patients with previous chronic RV pacing, using pressure-volume loop analyses to determine the optimal left ventricular (LV) lead position during implantation. METHODS AND RESULTS: In this single-blinded, randomized, controlled crossover study, 40 patients with chronic RV apical pacing and symptoms of heart failure, decreased LV ejection fraction (LVEF) or dyssynchrony were included. During implantation, stroke work (SW), LVEF, cardiac output, and LV dP/dt(max) were assessed by a conductance catheter. Clinical and echocardiographic response was studied during a 3-month period of RV pacing (RV period, LV lead inactive) and a 3-month period of biventricular pacing (CRT period). At the optimal LV lead position, SW (37 ± 41%), LVEF (16 ± 13%), cardiac output (29 ± 16%), and LV dP/dt(max) increased (11 ± 11%) significantly during biventricular pacing compared to baseline. Additional benefit could be achieved by pressure-volume loop guided selection of the best left-sided pacing location. RV outflow tract pacing did not improve hemodynamics. During follow-up, symptoms improved during CRT, VO(2,max) increased 10% and significant improvements in LVEF, LV volumes, and mitral regurgitation were observed as compared to the RV period. CONCLUSIONS: CRT in patients with chronic RV pacing causes significant improvement of both LV function as measured by pressure-volume loops during implantation and clinical and echocardiographic improvement during follow-up. Pressure-volume loops during implantation may facilitate selection of the most optimal pacing site.

Radiological and electrocardiographic characterization of right ventricular outflow tract pacing.

AIMS: The right ventricular outflow tract (RVOT) is used as an alternative pacing site, but its superiority to the RV apex remains to be established. This lack of proof may in part be explained by heterogeneity within the RVOT-paced group, due to poor definitions of the RVOT. The aim of the present study is to characterize the RVOT in terms of fluoroscopic and electrocardiographic parameters. METHODS AND RESULTS: One hundred and forty-three patients who underwent pacemaker implantation with a ventricular lead in the RVOT were included. Lead position was determined by fluoroscopy. The RVOT was divided into three areas: anterior, septal, and free wall (FW). On a 12-lead electrocardiogram (ECG) during forced ventricular pacing, QRS duration, configuration, and amplitude was determined. Lead position was judged to be anterior in 52 (36%), septal in 43 (30%), and FW in 48 (34%) patients, respectively. QRS duration is not significantly different between groups. QRS axis differs significantly between pacing sites (septal 79 ± 31°, anterior 60 ± 46°, FW 47 ± 38°, P < 0.05). QRS vector in lead I and QRS morphology and vector in lead aVL differ significantly between pacing sites. Precordial transition is earlier (towards V1) in septal pacing. CONCLUSIONS: This study demonstrates heterogeneity of pacing site and depolarization pattern within a cohort of patients paced form the RVOT. However, due to considerable overlap, we could not define clear cut-off point or devise flow-charts to match ECG and pacing site.

Left atrial pressure reduction for mitral stenosis reverses left atrial direction-dependent conduction abnormalities.

AIMS: Left atrial (LA) stretch-associated electrophysiological changes in patients with mitral stenosis (MS) predispose to atrial fibrillation. We hypothesized that the normalization of the pressure gradient by percutaneous transvenous mitral balloon valvotomy (PTMV) affects LA but not right atrial (RA) conduction, depending on the site of stimulation. Because direction-dependent (asymmetric) changes of conduction may contribute to arrhythmogenesis, we assessed conduction symmetry in MS patients and tested whether it is restored by PTMV. METHODS AND RESULTS: In nine patients with MS, atrial effective refractory period and local activation times (ATs) were determined during stimulation before and after PTMV, with up to four decapolar catheters (LA and RA). Eight patients with ventricular pre-excitation served as controls. ATs at basic cycle length were similar before and after PTMV. With stimulation from either atrium, they were about 45 ms in the ipsilateral atrium and about 115 ms in the contralateral atrium. With premature stimulation, ATs increased dramatically. The shortest ATs were found in the RA with RA stimulation (78 +/- 9 and 80 +/- 6 ns, before and after PTMV). PTMV caused a shortening in LA-ATs (following LA stimulation) from 118 +/- 14 to 82 +/- 5 ms (before and after; P < 0.05). Asymmetry in conduction properties was therefore normalized by PTMV. PTMV led to a decrease in RA-ATs (following LA stimulation) from 196 +/- 11 to 174 +/- 13 ms (P < 0.02). In addition, following RA stimulation, the dispersion in ATs in the LA decreased significantly by PTMV (from 66 +/- 10 to 34 +/- 7 ms; P < 0.02). CONCLUSION: MS is associated with LA conduction delay, increased LA dispersion of conduction, and conduction asymmetry. These changes are immediately reversible by PTMV.

Myocardial perfusion SPECT identifies patients with left bundle branch block patterns at high risk for future coronary events.

BACKGROUND: The value of myocardial perfusion SPECT (MPS) for patients with left bundle branch block (LBBB) or right ventricular apical (RVA) pacing seems reduced. The prognosis of patients with only abnormal activation related perfusion defects (AARD) due to LBBB or RVA-pacing is similar to those with a normal MPS. We assessed the prognostic value of MPS in patients with LBBB or RVA pacing. METHODS: Patients with LBBB or RVA pacing referred for vasodilator stress MPS between April 2002 and January 2006 were analyzed. Group 1 are patients with normal MPS and MPS with AARD. Group 2 are patients with an MPS with a perfusion defect extending outside the AARD area. Events were cardiac death, acute myocardial infarction and coronary revascularization. RESULTS: In Group 1 (101 patients) 12 events and in Group 2 (96 patients) 45 events occurred during a mean follow-up of 2.6 +/- 1.5 years. The prognosis of Group 2 was significantly worse (49%) compared with Group 1 (91%). The annual cardiac death rate was 0.7%/year in Group 1 and 6.4%/year in Group 2 (P < .001). The prognosis of patients with LBBB was not different from those with RVA pacing. CONCLUSION: Group 2 had a significantly worse cardiac prognosis compared to Group 1. The annual cardiac death rate of <1% in Group 1 warrants a watchful waiting strategy, whereas the cardiac death rate in Group 2 warrants aggressive invasive coronary strategies.

Long-term clinical response of cardiac resynchronization after chronic right ventricular pacing.

Chronic right ventricular (RV) pacing might elicit unpredictably deleterious effects on left ventricular (LV) function similar to that of native left bundle branch block (LBBB). The objective of the present study was to evaluate the clinical and echocardiographic response to cardiac resynchronization therapy after years of chronic RV pacing. In this prospective observational study of 284 consecutive patients, cardiac resynchronization therapy was performed in 194 patients (68%) with a native LBBB and in 90 patients (32%) with a pacing-induced LBBB after chronic RV pacing (upgraded group). Echocardiographic and clinical parameters were evaluated in both groups at baseline and during 2 years of follow-up. The clinical response was defined as survival with improvement of > or =1 in the New York Heart Association class without heart failure hospitalization. Reverse LV remodeling was defined as LV end-systolic volume reduction of > or =15%. At baseline, the New York Heart Association class, quality of life, and exercise capacity were comparable but the LV ejection fraction was significant greater and the LV volumes were significant smaller in the upgraded group. Changes with time in the clinical parameters, echocardiographic parameters, and clinical response were not significantly different between the 2 groups. Reverse LV remodeling was observed in 86% in the upgraded group versus 78% of the native LBBB group after 1 year (p = 0.39). Survival was not significantly different between the 2 groups. In conclusion, comparable clinical and echocardiographic improvement was seen when resynchronization therapy was applied in patients with preceding chronic RV pacing compared with patients with a native LBBB.