A New Dual-Chamber Pacing Mode to Minimize Ventricular Pacing

Occurrence of significant long PR intervals in patients implanted for sinus node dysfunction and monitored with SafeR™: The PRECISE study

BACKGROUND

Long PR intervals may increase cardiovascular complications, including atrial fibrillation. In pacemakers, the SafeR™ mode monitors PR intervals, switching from AAI to DDD when criteria for atrioventricular block are met.

AIMS

The PRECISE study evaluated the incidence and predictors of long PR intervals and their association with incident atrial fibrillation after 1 year in patients implanted for sinus node dysfunction and free from significant conduction disorders at baseline.

METHODS

This French, prospective, multicentre, observational trial enrolled patients implanted with a REPLY™ dual-chamber pacemaker. Pacemaker memory recorded long PR intervals (defined as first-degree atrioventricular block mode switches occurring after six consecutive PR/AR intervals≥350/450ms) and atrial fibrillation incidence (fallback mode switch>1minute/day). Predictors were identified from baseline variables (age, sex, AR and PR intervals, atrial rhythm disorder and medication) using logistic regression.

RESULTS

Of 291 patients with sinus node dysfunction enrolled, 214 were free from significant conduction disorders at baseline (mean age 79±8 years; 44% men; PR/AR intervals<350/450ms). After 1 year, long PR intervals had occurred in 116 patients (54%) and atrial fibrillation in 63 patients (30%). Amiodarone was the only independent predictor of long PR interval occurrence (odds ratio 2.50, 95% confidence interval 1.20-5.21; P=0.014). There was a strong trend towards an association between long PR interval and atrial fibrillation incidence (odds ratio 1.86, 95% confidence interval 0.97-3.61; P=0.051).

CONCLUSIONS

Half of the patients with pure sinus node dysfunction developed long PR intervals in the year following pacemaker implantation. Amiodarone was the only independent predictor of long PR intervals. There was a strong trend towards an association between long PR intervals and incident atrial fibrillation.

Clinical outcomes with biventricular versus right ventricular pacing in patients with atrioventricular conduction defects

There have been increasing concerns about the unexpected effects of right ventricular (RV) pacing. We aimed to systematically evaluate the effect of biventricular (BiV) versus RV pacing on clinical events in patients with impaired AV conduction. We searched PubMed, EMBASE, and Cochrane Library for studies comparing BiV pacing with RV pacing in patients with AV block, through April 2017. We selected randomized controlled trials (RCTs) reporting data on mortality, hospitalization for heart failure (HF), and/or 6-min walk distance (6MWD). A total of 12 RCTs were finally included. Pooled analysis suggested that BiV pacing was associated with a significantly reduced all-cause mortality in contrast to RV pacing (risk ratio (RR) = 0.77, 95% confidence interval (CI) 0.62 to 0.95, I² = 9.6%). BiV pacing, compared with RV pacing, significantly reduced the rate of HF hospitalization (RR = 0.74, 95% CI 0.59 to 0.93, I² = 10.1%). Sensitivity analyses by excluding studies with AV nodal ablation showed that BiV pacing still had a lower mortality and non-significant reduced HF hospitalization. Patients in BiV and RV pacing mode had a similar 6WMD at follow-up (mean difference = 4.99 m, 95% CI - 11.34 to 21.33 m, I² = 0%). Meta-regression analysis showed that the effect size of all-cause mortality or HF hospitalization was not significantly associated with mean LVEF value at baseline. In patients with impaired AV conduction that need frequent ventricular pacing, BiV pacing was associated with reduced mortality and hospitalization for HF, compared with traditional RV pacing mode.

Feasibility and Acute Hemodynamic Effect of Left Ventricular Septal Pacing by Transvenous Approach Through the Interventricular Septum

BACKGROUND

Left ventricular septal (LVS) pacing reduces ventricular dyssynchrony and improves cardiac function relative to right ventricular apex (RVA) pacing in animals. We aimed to establish permanent placement of an LVS pacing lead in patients using a transvenous approach through the interventricular septum.

METHODS AND RESULTS

Ten patients with sinus node dysfunction scheduled for dual-chamber pacemaker implantation were prospectively enrolled. A custom pacing lead with extended helix was introduced via the left subclavian vein and, after positioning against the right ventricular septum (RVS) using a preshaped guiding catheter, driven through the interventricular septum to the LVS. The acute hemodynamic effect of RVA, RVS, and LVS pacing was evaluated by invasive LVdP/dtmax measurements. The lead was successfully delivered to the LVS in all patients. Procedure time and fluoroscopy time shortened with experience. QRS duration was shorter during LVS pacing (144 ± 20 ms) than during RVA (172 ± 33 ms; P = 0.02 versus LVS) and RVS pacing (165 ± 17 ms; P = 0.004 versus LVS). RVA and RVS pacing reduced LVdP/dtmax compared with baseline atrial pacing (-7.1 ± 4.1% and -6.9 ± 4.3%, respectively), whereas LVS pacing maintained LVdP/dtmax at baseline level (1.0 ± 4.3%; P = 0.001 versus RVA and RVS). R-wave amplitude and pacing threshold were 12.2 ± 6.7 mV and 0.5 ± 0.2 V at implant and remained stable during 6-month follow-up without lead-related complications.

CONCLUSIONS

Permanent placement of an LVS pacing lead by transvenous approach through the interventricular septum is feasible in patients. LVS pacing preserves acute left ventricular pump function. This new pacing method could serve as an alternative and hemodynamically preferable approach for antibradycardia pacing.

Very Low Ventricular Pacing Rates Can Be Achieved Safely in a Heterogeneous Pacemaker Population and Provide Clinical Benefits: The CANadian Multi-Centre Randomised Study-Spontaneous AtrioVEntricular Conduction pReservation (CAN-SAVE R) Trial

BACKGROUND

It is well recognized that right ventricular apical pacing can have deleterious effects on ventricular function. We performed a head-to-head comparison of the SafeR pacing algorithm versus DDD pacing with a long atrioventricular delay in a heterogeneous population of patients with dual-chamber pacemakers.

METHODS AND RESULTS

In a multicenter prospective double-blinded randomized trial conducted at 10 centers in Canada, 373 patients, age 71±11 years, with indications for dual chamber DC pacemakers were randomized 1:1 to SafeR or DDD pacing with a long atrioventricular delay (250 ms). The primary objective was twofold: (1) reduction in the proportion of ventricular paced beats at 1 year; and (2) impact on atrial fibrillation burden at 3 years, defined as the ratio between cumulative duration of mode-switches divided by follow-up time. Statistical significance of both co-primary end points was required for the trial to be considered positive. At 1 year of follow-up, the median proportion of ventricular-paced beats was 4.0% with DDD versus 0% with SafeR (P<0.001). At 3 years of follow-up, the atrial fibrillation burden was not significantly reduced with SafeR versus DDD (median 0.00%, interquartile range [0.00% to 0.23%] versus median 0.01%, interquartile range [0.00% to 0.44%], respectively, P=0.178]), despite a persistent reduction in the median proportion of ventricular-paced beats (10% with DDD compared to 0% with SafeR).

CONCLUSIONS

A ventricular-paced rate <1% was safely achieved with SafeR in a population with a wide spectrum of indications for dual-chamber pacing. However, the lower percentage of ventricular pacing did not translate into a significant reduction in atrial fibrillation burden.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov/ Unique identifier: NCT01219621.

Long-term clinical effects of ventricular pacing reduction with a changeover mode to minimize ventricular pacing in a general pacemaker population

Aim

Right ventricular pacing (VP) has been hypothesized to increase the risk in heart failure (HF) and atrial fibrillation (AF). The ANSWER study evaluated, whether an AAI-DDD changeover mode to minimize VP (SafeR) improves outcome compared with DDD in a general dual-chamber pacemaker population.

Methods and results

ANSWER was a randomized controlled multicentre trial assessing SafeR vs. standard DDD in sinus node disease (SND) or AV block (AVB) patients. After a 1-month run-in period, they were randomized (1 : 1) and followed for 3 years. Pre-specified co-primary end-points were VP and the composite of hospitalization for HF, AF, or cardioversion. Pre-specified secondary end-points were cardiac death or HF hospitalizations and cardiovascular hospitalizations. ANSWER enrolled 650 patients (52.0% SND, 48% AVB) at 43 European centres and randomized in SafeR (n = 314) or DDD (n = 318). The SafeR mode showed a significant decrease in VP compared with DDD (11.5 vs. 93.6%, P < 0.0001 at 3 years). Deaths and syncope did not differ between randomization arms. No significant difference between groups [HR = 0.78; 95% CI (0.48–1.25); P = 0.30] was found in the time to event of the co-primary composite of hospitalization for HF, AF, or cardioversion, nor in the individual components. SafeR showed a 51% risk reduction (RR) in experiencing cardiac death or HF hospitalization [HR = 0.49; 95% CI (0.27–0.90); P = 0.02] and 30% RR in experiencing cardiovascular hospitalizations [HR = 0.70; 95% CI (0.49–1.00); P = 0.05].

Conclusion

SafeR safely and significantly reduced VP in a general pacemaker population though had no effect on hospitalization for HF, AF, or cardioversion, when compared with DDD.

Non-physiological increase of AV conduction time in sinus disease patients programmed in AAIR-based pacing mode

PURPOSE

The EVOCAV(DS) trial aimed to quantify the paradoxal atrioventricular (AV) conduction time lengthening in sinus node (SD) patients (pts) paced in AAIR-based pacing mode.

METHODS

SD pts, implanted with dual-chamber pacemaker programmed in AAIR-based pacing mode, were randomized in two arms for a 1-month period: the low atrial pacing (LAP; basic rate at 60 bpm, dual sensor with minimal slope) and the high atrial pacing (HAP; basic rate at 70 bpm, dual sensor with optimized slope, overdrive pacing) arm. At 1 month, crossover was performed for an additional 1-month period. AV conduction time, AV block occurrence and AV conduction time adaptation during exercise were ascertained from device memories at each follow-up.

RESULTS

Seventy-nine pts participated to the analysis (75 ± 8 years; 32 male; PR = 184 ± 38 ms; bundle branch block n = 12; AF history n = 36; antiarrhythmic treatment n = 53; beta-blockers n = 27; class III/Ic n = 18; both n = 8). The mean AV conduction time was significantly greater during the HAP (275 ± 51 ms) vs. LAP (263 ± 49 ms) period (p < 0.0001). Class III/Ic drugs were the only predictors of this abnormal behaviour. Degree II/III AV blocks occurred in 49 % of pts in the HAP vs. 19 % in the LAP period (p < 0.0001). Fifty-two patients (66 %) presented a lengthening of AV conduction time during exercise.

CONCLUSION

AAIR-based pacing in SD pts may induce a significant lengthening of pts' AV conduction time, including frequent abnormal adaptation of AV conduction time during exercise.

Conventional and biventricular pacing in patients with first-degree atrioventricular block

Recent reports suggest that first-degree atrioventricular block is not benign. However, there is no evidence that shortening of the PR interval can improve outcome except for symptomatic patients with a very long PR interval ≥0.3 s. Because these patients require continual forced pacing, biventricular pacing should be used according to accepted guidelines for third-degree AV block. Functional atrial undersensing may occur in patients with conventional dual-chamber pacing and first-degree AV block because the sinus P-wave tends to be displaced into the post-ventricular atrial refractory period (PVARP) an arrangement that may cause a pacemaker syndrome. Prevention requires programming a shorter AV and PVARP that is feasible because retrograde conduction is rare in first-degree AV block patients. A relatively new pacing mode to minimize right ventricular stimulation has been designed by eliminating the traditional AV interval but with dual-chamber backup. This pacing mode permits the establishment of very long AV intervals that may cause pacemaker syndrome. About 50% of patients undergoing cardiac resynchronization therapy (CRT) have a PR interval ≥200 ms. The CRT patients with first-degree AV block are prone to develop electrical desynchronization more easily than those with a normal PR interval. The duration of desynchronization after exceeding the upper rate on exercise is also more pronounced. AV junctional ablation is rarely necessary in patients with first-degree AV block but should be considered for symptomatic functional atrial undersensing or when the disturbances caused by first-degree AV block during CRT cannot be managed by programming.

Optimizing pacemaker longevity with pacing mode and settings programming: results from a pacemaker multicenter registry

BACKGROUND

This study aimed to describe the influence on dual-chamber devices' expected longevity of devices' settings.

METHODS

Data from patients implanted with dual chamber devices (Symphony™, SORIN CRM SAS, Clamart, France) from 2003 to 2006 were collected in registries. Programmer files were retrieved: device-estimated longevity, assessed through algorithm prediction, was analyzed according to device settings.

RESULTS

One thousand sixty-eight recipients of dual chamber pacemaker in sinus rhythm (75.3±11.1 years, 54.5% male, ventricular block 30%, brady-tachy syndrome 21%, and sinus node dysfunction 49%) were followed up to 14.2±12.1 months (ranging from first quartile Q1: 2.9 months to fourth quartile Q4: 49.3 months) after implantation. DDD with automatic mode conversion and minimized ventricular pacing (SafeR) modes were programmed in 34.3%, 2.9%, and 62.8% of the patients, respectively. The mean total longevity estimated by the device was 134.1±31.5 months (11.2±2.6 years). Significant increase in longevity was observed in devices undergoing at least one reprogramming (134.4±31.4 months) versus device presenting no reprogramming (103.4±32.3 months, P=0.0005). The parameters associated with the major increase in mean longevity were the mode (mean longevity increase of +23.9 months in SafeR as compared to DDD mode, P<0.0001) and the atrial (A) and ventricular (V) amplitudes (mean longevity increase of +29.6 and +26.9 months for a decrease of less than 1V in A and V outputs respectively, P<0.0001).

CONCLUSION

This study provides information on dual chamber pacemakers' longevity and highlights the impact of devices' reprogramming on expected longevities.

Near elimination of ventricular pacing in SafeR mode compared to DDD modes: a randomized study of 422 patients

AIMS

SafeR performance versus DDD/automatic mode conversion (DDD/AMC) and DDD with a 250-ms atrioventricular (AV) delay (DDD/LD) modes was assessed toward ventricular pacing (Vp) reduction.

METHODS

After a 1-month run-in phase, recipients of dual-chamber pacemakers without persistent AV block and persistent atrial fibrillation (AF) were randomly assigned to SafeR, DDD/AMC, or DDD/LD in a 1:1:1 design. The main endpoint was the percentage of Vp (%Vp) at 2 months and 1 year after randomization, ascertained from device memories. Secondary endpoints include %Vp at 1 year according to pacing indication and 1-year AF incidence based on automatic mode switch device stored episodes.

RESULTS

Among 422 randomized patients (73.2±10.6 years, 50% men, sinus node dysfunction 47.4%, paroxysmal AV block 30.3%, bradycardia-tachycardia syndrome 21.8%), 141 were assigned to SafeR versus 146 to DDD/AMC and 135 to DDD/LD modes. Mean %Vp at 2 months was 3.4±12.6% in SafeR versus 33.6±34.7% and 14.0±26.0% in DDD/AMC and DDD/LD modes, respectively (P<0.0001 for both). At 1 year, mean %Vp in SafeR was 4.5±15.3% versus 37.9±34.4% and 16.7±28.0% in DDD/AMC and DDD/LD modes, respectively (P<0.0001 for both). The proportion of patients in whom Vp was completely eliminated was significantly higher in SafeR (69%) versus DDD/AMC (15%) and DDD/LD (45%) modes (P<0.0001 for both), regardless of pacing indication. The absolute risk of developing permanent AF or of remaining in AF for >30% of the time was 5.4% lower in SafeR than in the DDD pacing group (ns).

CONCLUSIONS

In this selected patient population, SafeR markedly suppressed unnecessary Vp compared with DDD modes.

Evolutionary innovations in cardiac pacing

Cardiac pacing has played a significant role in mitigating morbidity and mortality associated with bradyarrhythmias. Throughout the years, advances made in battery reliability, lead performance, and device portability have rapidly expanded the use of cardiac pacemakers in many different disease states. Despite the benefits, there has been growing awareness of the potential deleterious effects of long-term artificial electrical stimulation including the development of ventricular dyssynchrony and atrial fibrillation. Given their association with an increased risk for heart failure and possibly death, several advances aimed at minimizing them have been made in recent years including changes in atrioventricular pacing algorithms, novel pacing mode modifications, and better identification of hemodynamically optimal pacing sites. This article reviews the advances made and the future direction of innovations in cardiac pacing.

[Pacemaker ECG quiz no. 21: Strange ECG after DDDR pacemaker implantation]

In a patient with sinus node disease (intermittent sinus arrest with symptomatic pauses >4 s), a DDDR pacemaker with a dedicated algorithm to avoid unnecessary ventricular pacing (mode switch between AAIR and DDDR) was implanted. The pacemaker ECG after implantation shows an unexpected tachycardia.

[Avoidance of ventricular pacing in patients with sinus node disease or intermittent AV block]

In patients with frequent right ventricular stimulation, worsening of heart failure and atrial fibrillation may occur. Avoidance of unnecessary right ventricular pacing is a major requirement for pacemaker selection and programming in patients with sinus node disease or intermittent AV block. In dual chamber pacemakers this goal can be achieved by programming a long AV delay or an AV delay hysteresis. Algorithms that allow AAI pacing in a dual chamber pacing mode and change to DDD mode in case of high degree AV block are a new attempt to avoid unnecessary right ventricular pacing. The article describes various strategies to avoid unnecessary ventricular pacing and discusses their advantages and disadvantages.

New developments in antibradycardic devices

With increasing advances in technology, cardiac pacemakers have become highly sophisticated devices that allow diagnostic and therapeutic functions beyond conventional antibradycardic therapy. This review discusses the most promising developments in antibradycardic device therapy, such as novel diagnostic functions, telemonitoring, autoadjustment of programmed parameters, algorithms for support of intrinsic atrioventricular conduction, pacing algorithms for the prevention of atrial arrhythmias and cardiac resynchronization therapy. A short overview of the basic principles of antibradycardic device therapy is also provided.

Right ventricular apical pacing: a necessary evil?

PURPOSE OF REVIEW

Clinical trial evidence suggests that traditional right ventricular apical pacing may be harmful. This review summarizes the existing evidence and outlines the major avenues of ongoing research in this field.

RECENT FINDINGS

Despite theoretical advantages of dual-chamber pacing, large randomized trials found only a small advantage over single-chamber ventricular pacing. Subsequent analysis of one of these trials suggested that this was due to the tendency for dual-chamber pacemakers to produce frequent, unnecessary right ventricular pacing. This hypothesis is supported by a prospective study among defibrillator recipients, showing that dual-chamber pacing results in a very high frequency of ventricular pacing and worse clinical outcomes, compared with backup ventricular pacing. These observations have led to a renewed interest in single-chamber atrial pacing for sinus node dysfunction, the development of new dual-chamber pacemaker algorithms designed to minimize right ventricular pacing, and the search for better ways to pace the ventricles in patients who require ventricular pacing.

SUMMARY

Conventional right ventricular apical pacing should be avoided whenever possible. In patients who require ventricular pacing, ongoing research will determine if selected-site pacing or multisite pacing improves clinical outcomes compared with traditional right ventricular apical pacing.

Physiologic Pacing: New Modalities and Pacing Sites

Right ventricular (RV) apical pacing impairs left ventricular function by inducing dys-synchronous contraction and relaxation. Chronic RV apical pacing is associated with an increased risk of atrial fibrillation, morbidity, and even mortality. These observations have raised questions regarding the appropriate pacing mode and site, leading to the introduction of algorithms and new pacing modes to reduce the ventricular pacing burden in dual chamber devices, and a shift of the pacing site away from the RV apex. However, further investigations are required to assess the long-term results of pacing from alternative sites in the right ventricle, because long-term results so far are equivocal. The potential benefit of prophylactic biventricular, mono-chamber left ventricular, and bifocal RV pacing should be explored in selected patients with a narrow QRS complex, especially those with impaired left ventricular function. His bundle pacing is a promising and evolving technique that requires improvements in lead technology.

The deleterious consequences of right ventricular apical pacing: time to seek alternate site pacing

BACKGROUND

The purpose of this article is to critically review the data accumulated to date from studies evaluating the hemodynamic and clinical effects of right ventricular apical pacing during conventional permanent cardiac pacing. The data from studies comparing the effects of right ventricular apical pacing and alternate site ventricular pacing are also reviewed.

METHODS

We conducted a MEDLINE and journal search of English-language reports published in the last decade and searched relevant papers.

RESULTS

Although intraventricular conduction delay in the form of left bundle branch block (LBBB) has traditionally been viewed as an electrophysiologic abnormality, it has now become abundantly clear that it has profound hemodynamic effects due to ventricular dyssynchrony, especially in patients with heart failure. These deleterious effects can be significantly ameliorated by cardiac resynchronization therapy effected by biventricular or left ventricular pacing. However, not only is spontaneous LBBB harmful, but the iatrogenic variety produced by right ventricular apical pacing in patients with permanent pacemakers may be equally deleterious. In this review new evidence from recent studies is presented, which strongly suggests a harmful effect of our long-standing practice of producing an iatrogenic LBBB by conventional right ventricular apical pacing in patients receiving permanent pacemakers. This emerging strong new evidence about the adverse hemodynamic and clinical effects of right ventricular apical pacing would dictate a reassessment of our traditional approach to permanent cardiac pacing and direct our attention to alternate sites of pacing, such as the left ventricle and/or the right ventricular outflow tract or septum, if not for all patients, at least for those with left ventricular dysfunction. Indeed, current convincing data on alternate site ventricular pacing are encouraging and this approach should be actively pursued and further investigated in future studies.

CONCLUSIONS

Not only is spontaneous permanent LBBB harmful to our patients, but the iatrogenic variety produced by right ventricular apical pacing during conventional permanent pacing may also be deleterious to some patients. The compelling evidence presented herein cannot be ignored; it may dictate a change of attitude toward right ventricular apical pacing directing our attention to alternate sites of ventricular pacing and avoidance of the right ventricular apex.

[Feasibility and safety of long-term AAI(R) pacing in isolated sinus node syndrome]

Recent investigations prove that AAI(R) pacing is the "ideal" stimulation mode in isolated sick sinus syndrome. Nevertheless, in Germany this bradycardia is treated by AAI(R) pacemakers in less than 4% of cases compared to 25% in other countries. In our institution treatment of patients with isolated sick sinus syndrome is uniform and corresponds to the actual guidelines since the early 1990s; therefore the aim of our study was to analyze feasibility and safety of AAI(R) pacing in a retrospective study. Between 1998 and 2000, 52 of 165 patients (31.5%) with isolated sick sinus syndrome were treated by an AAI(R) pacemaker. The median follow-up duration was 51.5 months (minimal: 36 months). 6 patients died, in all cases unrelated to the stimulation mode. Three patients required reoperations, however, in only one case due to second degree AV block with the need for upgrading to DDD stimulation. Thus, the yearly incidence of this specific complication in the AAI(R) cohort is 0.64%.In conclusion, permanent atrial stimulation in isolated sick sinus syndrome is feasible in a quarter of all cases. It is safe if performed corresponding to actual guidelines. Additionally, single lead AAI(R) pacing is a cost-effective therapy and the only stimulation mode which, today, reliably prevents unnecessary right ventricular stimulation. If, on the other hand, algorithms providing automatic mode switching from AAI to DDD and vice versa are implemented reliably into all dual chamber pacemakers, single chamber atrial pacing will no longer be a subject for discussion.

Use of a new cardiac pacing mode designed to eliminate unnecessary ventricular pacing

AIMS

To examine the performance of AAIsafeR2, a new pacing mode to minimize the cumulative proportion of ventricular pacing in patients who do not need regular ventricular support.

METHODS AND RESULTS

The safety of AAIsafeR2 was examined in 123 recipients (73 +/- 12 years old, 51% men) of dual chamber pacemakers implanted for sinus node dysfunction, paroxysmal AV block or the bradycardia-tachycardia syndrome. Data were collected from pacemaker diagnostics, and the first 43 patients underwent 24-h Holter recordings before being discharged from the hospital with AAIsafeR2 activated. No adverse event related to AAIsafeR2 was observed. All ventricular pauses detected on Holter tapes triggered immediate back-up ventricular pacing. Appropriate switches to DDD occurred in 97 of 123 patients. In 69 of 123 devices (56%) switches to DDD were non-sustained, and the average % ventricular pacing in this group was 0.2+/-0.5%.

CONCLUSION

AAIsafeR2 mode seems to be safe and reliable in patients with infrequent slowing or pauses in ventricular activity, while maintaining ventricular pacing below 1%.

Temas de actualidad en estimulación cardíaca 2005

Currently, three areas of active development in cardiac pacing are of particular interest to clinical cardiologists. Biventricular pacing is now considered a type-I indication for adjuvant treatment in advanced and refractory heart failure. Consequently, some changes in everyday clinical practice will be seen when patients with end-stage heart failure start to receive resynchronization therapy. Secondly, the Cardiac Pacing Working Group of the Spanish Society of Cardiology has developed a national consensus document on sleep apnea and cardiac rhythm abnormalities. It appears that a novel way of tackling the current growing epidemic could be to use permanent cardiac pacing in an attempt to modify the cardiac rhythm alterations, mainly bradyarrhythmias, related to sleep apnea. Finally, promising developments are taking place in systems designed to reduce the unwanted right ventricular stimulation sometimes observed with antibradycardia pacing modalities. These new systems are expected to minimize significantly the well-known deleterious hemodynamic effects sometimes seen in our patients.

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.