Survey of cardiac pacing and defibrillation in the United States in 1993

A Dexamethasone-Loaded Polymeric Electrospun Construct as a Tubular Cardiovascular Implant

Cardiovascular tissue engineering is providing many solutions to cardiovascular diseases. The complex disease demands necessitating tissue-engineered constructs with enhanced functionality. In this study, we are presenting the production of a dexamethasone (DEX)-loaded electrospun tubular polymeric poly(l-lactide) (PLA) or poly(d,l-lactide-co-glycolide) (PLGA) construct which contains iPSC-CMs (induced pluripotent stem cell cardiomyocytes), HUVSMCs (human umbilical vein smooth muscle cells), and HUVECs (human umbilical vein endothelial cells) embedded in fibrin gel. The electrospun tube diameter was calculated, as well as the DEX release for 50 days for 2 different DEX concentrations. Furthermore, we investigated the influence of the polymer composition and concentration on the function of the fibrin gels by imaging and quantification of CD31, alpha-smooth muscle actin (αSMA), collagen I (col I), sarcomeric alpha actinin (SAA), and Connexin 43 (Cx43). We evaluated the cytotoxicity and cell proliferation of HUVECs and HUVSMCs cultivated in PLA and PLGA polymeric sheets. The immunohistochemistry results showed efficient iPSC-CM marker expression, while the HUVEC toxicity was higher than the respective HUVSMC value. In total, our study emphasizes the combination of fibrin gel and electrospinning in a functionalized construct, which includes three cell types and provides useful insights of the DEX release and cytotoxicity in a tissue engineering perspective.

Efficacy and Safety of Leadless Pacemaker Implantation in Octogenarians

INTRODUCTION

Long-term complication rates in standard transvenous pacemakers are reported around 4-12% with a higher incidence in the elderly population. We report our experience in octogenarians undergoing leadless pacemaker implantation in two large-volume centers in Switzerland.

METHODS

Consecutive patients undergoing leadless pacemaker implantation at two Swiss large volume centers (University Hospital Zurich, Zurich and Cardiocentro Ticino Institute, Lugano) between October 2015 and March 2020 were included in this retrospective analysis. Demographic information, clinical data, and procedural characteristics were recorded at the day of implantation and during follow-up.

RESULTS

Two hundred and twenty patients (mean age 80.6 ± 7.7 years, male 66%) were included. The main indication for pacemaker implantation was slow ventricular rate atrial fibrillation (111 of 220 patients, 50.4%). Out of the 220 patients, 124 (56.3%) were ≥80 years. Overall successful implantation rate was 98.6%. In the octogenarian population, the median procedure time (45 ± 20.2 min vs. 40 ± 19.6 min, p = 0.03) and radiation duration (6.1 ± 8.2 min vs. 5.0 ± 7.2 min, p = 0.03) were longer compared to patients <80 years. Major complications (2.7%, n = 6) and device measurements during follow-up were similar between patients ≥80 and <80 years.

CONCLUSION

Implantation of a leadless pacemaker device in octogenarians is safe and effective with a similarly low complication rate compared to non-octogenarians.

Sinus node dysfunction: current understanding and future directions

The sinoatrial node (SAN) is the primary pacemaker of the heart. Normal SAN function is crucial in maintaining proper cardiac rhythm and contraction. Sinus node dysfunction (SND) is due to abnormalities within the SAN, which can affect the heartbeat frequency, regularity, and the propagation of electrical pulses through the cardiac conduction system. As a result, SND often increases the risk of cardiac arrhythmias. SND is most commonly seen as a disease of the elderly given the role of degenerative fibrosis as well as other age-dependent changes in its pathogenesis. Despite the prevalence of SND, current treatment is limited to pacemaker implantation, which is associated with substantial medical costs and complications. Emerging evidence has identified various genetic abnormalities that can cause SND, shedding light on the molecular underpinnings of SND. Identification of these molecular mechanisms and pathways implicated in the pathogenesis of SND is hoped to identify novel therapeutic targets for the development of more effective therapies for this disease. In this review article, we examine the anatomy of the SAN and the pathophysiology and epidemiology of SND. We then discuss in detail the most common genetic mutations correlated with SND and provide our perspectives on future research and therapeutic opportunities in this field.

The association of racial differences with in-hospital outcomes of patients admitted for sinus node dysfunction

Background

The impact of race and its related social determinants of health on cardiovascular disease outcomes has been well documented. However, limited data exist regarding the association of race with in-hospital outcomes in patients admitted for sinus node dysfunction (SND).

Objective

To evaluate whether racial disparities exist in outcomes for patients hospitalized with a primary diagnosis of SND.

Methods

The National Inpatient Sample was queried from 2011 to 2018 for relevant ICD-9 and ICD-10 diagnosis and procedure codes. Baseline characteristics and in-hospital outcomes in patients with a primary diagnosis of SND were compared among White and non-White patients. A multivariate logistic regression model was used to adjust for potential confounding factors and statistically significant comorbidities between both cohorts.

Results

We identified 655,139 persons admitted with a primary diagnosis of SND, 520,926 (79.5%) of whom were White. Non-White patients had significantly higher all-cause mortality, length of stay, and total hospital cost. There were lower odds of pacemaker insertion (adjusted odds ratio [aOR] 1.13 [95% confidence interval (CI) 1.11–1.15]), temporary transvenous pacing (aOR 1.15 [95% CI 1.11–1.22]), and cardioversion (aOR 1.50 [95% CI 1.42–1.58]) in non-White patients. A subgroup analysis was performed and non-Hispanic Black race was predictive of a decreased odds of pacemaker insertion, cardioversion/defibrillation, and temporary transvenous pacing.

Conclusion

Significant differences of in-hospital outcomes exist between White and non-White patients with SND. These findings appeared to be primarily driven by disparities in non-Hispanic Black patients. Increased recognition and focused efforts to mitigate these disparities will improve the care of underrepresented populations treated for SND.

Safety of leadless pacemaker implantation in the very elderly

BACKGROUND

The Micra leadless pacemaker (MLP) has proven to be an effective alternative to a traditional transvenous pacemaker (TVP). However, there has been concern about using the MLP in frail elderly patients because of the size of the implant sheath and perceived risk of perforation.

OBJECTIVES

The objectives of this study were to report the safety of the MLP and compare MPLs with TVPs in the very elderly.

METHODS

All patients 85 years and older who received an MLP or a single-chamber TVP across 6 hospitals in the Northwell Health system from December 2015 to November 2019 were included. Demographic characteristics, procedural details, and procedure-related complications were reviewed.

RESULTS

Over 4 years, 564 patients underwent MLP implantation. During this time, 183 MLPs and 119 TVPs were implanted in patients 85 years and older. The mean age was 89.7 ± 3.4 years, and 47.4% were men. MLP implantation was successful in all but 3 patients (98.4% success rate). There was no difference in procedure-related complications (3.3% vs 5.9%; P = .276). Complications included 5 (2.7%) access site hematomas in the MLP group, 3 (2.5%) in the TVP group, 1 (0.5 vs 0.8%) pericardial effusion in each group, and 3 (2.5%) acute lead dislodgments (<24 hours) in the TVP group. MLP implantation resulted in a significantly shorter mean procedure time (35.7 ± 23.0 minutes vs 62.3 ± 31.5 minutes, P < .001).

CONCLUSION

In a large multicenter study of patients 85 years and older, MLP implantation (1) was successful in 98.4% of patients, (2) was safe with no difference in procedure-related complications compared to the TVP group, and (3) resulted in significantly shorter procedure times.

Prognosis after pacemaker implantation in extreme elderly

AIMS

Significant comorbidities may limit the potential benefit of pacemaker (PM) implantation in extreme elderly. A short-term mortality risk prediction score, able to identify high-risk patients, may be a useful tool in this population.

METHODS AND RESULTS

We retrospectively analyzed 538 patients aged >80 years at the time of implant who underwent PM implantation. Kaplan-Meier survival and multivariable Cox regression analyses were performed to identify patient, procedural or complication variables predictive of death. The ACP (Aging in Cardiac Pacing) Score was constructed by assigning weighted values to the variables identified by hazard ratios, combined into an additive mortality risk score equation. One, two and three-year overall mortality rate was 11%, 21% and 32% respectively. Renal failure (HR 1.63; CI 1.15-2.31; p = .006), active neoplasia (HR 1.78; CI 1.27-2.51; p = .008), connective tissue disorder (3.07; CI 1.34-7.08; p = .048), cerebrovascular disease (HR 1.75; CI 1.25-2.46; p = .001) and the use of a single lead device (HR 2.27; CI 1.6-3.24; p < .001) were independently associated with worse survival. The ACP Score showed discrete predictive ability (AUC 0,6792 CI 0,63-0,73). Kaplan-Meier survival curves comparing low vs high ACP Scores demonstrated that low ACP scores were associated with reduced mortality rates (p < .001).

CONCLUSIONS

Significant comorbidities were associated with worse survival after PM implantation in extreme elderly. The ACP Score is a novel tool that may help to identify patients with high mortality risk after device implantation.

Risk Factors Associated With Atrioventricular Block

IMPORTANCE

Pacemaker implantations as a treatment for atrioventricular (AV) block are increasing worldwide. Prevention strategies for AV block are lacking because modifiable risk factors have not yet been identified.

OBJECTIVE

To identify risk factors for AV block in community-dwelling individuals.

DESIGN, SETTING, AND PARTICIPANTS

In this population-based cohort study, data from the Mini-Finland Health Survey, conducted from January 1, 1978, to December 31, 1980, were used to examine demographics, comorbidities, habits, and laboratory and electrocardiographic (ECG) measurements as potential risk factors for incident AV block. Data were ascertained during follow-up from January 1, 1987, through December 31, 2011, using a nationwide registry. A total of 6146 community-dwelling individuals were included in the analysis performed from January 15 through April 3, 2018.

MAIN OUTCOMES AND MEASURES

Incidence of AV block (hospitalization for second- or third-degree AV block).

RESULTS

Among the 6146 participants (3449 [56.1%] women; mean [SD] age, 49.2 [12.9] years), 529 (8.6%) had ECG evidence of conduction disease and 58 (0.9%) experienced a hospitalization with AV block. Older age (hazard ratio [HR] per 5-year increment, 1.34; 95% CI, 1.16-1.54; P < .001), male sex (HR, 2.04; 95% CI, 1.19-3.45; P = .01), a history of myocardial infarction (HR, 3.54; 95% CI, 1.33-9.42; P = .01), and a history of congestive heart failure (HR, 3.33; 95% CI, 1.10-10.09; P = .03) were each independently associated with AV block. Two modifiable risk factors were also independently associated with AV block. Every 10-mm Hg increase in systolic blood pressure was associated with a 22% higher risk (HR, 1.22; 95% CI, 1.10-1.34; P = .005), and every 20-mg/dL increase in fasting glucose level was associated with a 22% higher risk (HR, 1.22; 95% CI, 1.08-1.35; P = .001). Both risk factors remained statistically significant (HR for systolic blood pressure, 1.26 [95% CI, 1.06-1.49; P = .007]; HR for glucose level, 1.22 [95% CI, 1.04-1.43; P = .01]) after adjustment for major adverse coronary events during the follow-up period. In population-attributable risk assessment, an estimated 47% (95% CI, 8%-67%) of AV blocks may have been avoided if all participants exhibited ideal blood pressure and 11% (95% CI, 2%-21%) may have been avoided if all had a normal fasting glucose level.

CONCLUSIONS AND RELEVANCE

In this analysis of data from a population-based cohort study, suboptimal blood pressure and fasting glucose level were associated with AV block. These results suggest that a large proportion of AV blocks are assocated with these risk factors, even after adjusting for other major adverse coronary events.

Impact of prior permanent pacemaker on long-term clinical outcomes of patients undergoing percutaneous coronary intervention

BACKGROUND

The impact of permanent pacemaker (PPM) on long-term clinical outcomes of patients undergoing percutaneous coronary intervention (PCI) has not been studied.

HYPOTHESIS

PPM may increase heart failure (HF) burden on patients undergoing PCI.

METHODS

We recruited consecutive patients undergoing PCI and carried out a nested case-control study. Patients with confirmed PPM undergoing first PCI were identified and matched by age and sex in 1:1 fashion to patients without PPM undergoing first PCI. Clinical data were collected and analyzed. The primary endpoint outcomes were all-cause mortality and hospitalization for HF.

RESULTS

The final analysis included 156 patients. The mean follow-up period was 4.6 ± 2.9 years. The overall all-cause mortality was 21.15%, without significant difference between the 2 groups (21.79% vs 20.51%; P = 0.85). However, the rate of HF-related hospitalization was significantly higher in patients with PPM than in controls (26.92% vs 10.26%; P = 0.008). After adjustment for hypertension, type 2 diabetes mellitus, hyperlipidemia, chronic kidney disease, stroke, left ventricular ejection fraction, brain natriuretic peptide, and acute coronary syndrome (ACS), PCI patients with PPM were still associated with a greater hospitalization rate for HF (odds ratio: 4.31, 95% confidence interval: 0.94-19.80, P = 0.061). Further analysis in the ACS subgroup showed VVI-mode pacing enhanced the risk for HF-associated hospitalization (adjusted odds ratio: 8.27, 95% confidence interval: 1.37-49.75, P = 0.02).

CONCLUSIONS

PPM has no effect on all-cause mortality in patients undergoing first PCI but significantly increases the HF-associated hospitalization rate, especially in ACS patients.

Sick sinus syndrome and atrial fibrillation in older persons - A view from the sinoatrial nodal myocyte

Sick sinus syndrome remains a highly relevant clinical entity, being responsible for the implantation of the majority of electronic pacemakers worldwide. It is an infinitely more complex disease than it was believed when first described in the mid part of the 20th century. It not only involves the innate leading pacemaker region of the heart, the sinoatrial node, but also the atrial myocardium, predisposing to atrial tachydysrhythmias. It remains controversial as to whether the dysfunction of the sinoatrial node directly causes the dysfunction of the atrial myocardium, or vice versa, or indeed whether these two aspects of the condition arise through some related underlying pathological mechanism, such as extracellular matrix remodeling, i.e., fibrosis. This review aims to shed new light on the myriad possible contributing factors in the development of sick sinus syndrome, with a particular focus on the sinoatrial nodal myocyte. This article is part of a Special Issue entitled CV Aging.

Association of sick sinus syndrome with incident cardiovascular disease and mortality: the Atherosclerosis Risk in Communities study and Cardiovascular Health Study

BACKGROUND

Sick sinus syndrome (SSS) is a common indication for pacemaker implantation. Limited information exists on the association of sick sinus syndrome (SSS) with mortality and cardiovascular disease (CVD) in the general population.

METHODS

We studied 19,893 men and women age 45 and older in the Atherosclerosis Risk in Communities (ARIC) study and the Cardiovascular Health Study (CHS), two community-based cohorts, who were without a pacemaker or atrial fibrillation (AF) at baseline. Incident SSS cases were validated by review of medical charts. Incident CVD and mortality were ascertained using standardized protocols. Multivariable Cox models were used to estimate the association of incident SSS with selected outcomes.

RESULTS

During a mean follow-up of 17 years, 213 incident SSS events were identified and validated (incidence, 0.6 events per 1,000 person-years). After adjustment for confounders, SSS incidence was associated with increased mortality (hazard ratio [HR] 1.39, 95% confidence interval [CI] 1.14-1.70), coronary heart disease (HR 1.72, 95%CI 1.11-2.66), heart failure (HR 2.87, 95%CI 2.17-3.80), stroke (HR 1.56, 95%CI 0.99-2.46), AF (HR 5.75, 95%CI 4.43-7.46), and pacemaker implantation (HR 53.7, 95%CI 42.9-67.2). After additional adjustment for other incident CVD during follow-up, SSS was no longer associated with increased mortality, coronary heart disease, or stroke, but remained associated with higher risk of heart failure (HR 2.00, 95%CI 1.51-2.66), AF (HR 4.25, 95%CI 3.28-5.51), and pacemaker implantation (HR 25.2, 95%CI 19.8-32.1).

CONCLUSION

Individuals who develop SSS are at increased risk of death and CVD. The mechanisms underlying these associations warrant further investigation.

Incidence of and risk factors for sick sinus syndrome in the general population

BACKGROUND

Little is known about the incidence of and risk factors for sick sinus syndrome (SSS), a common indication for pacemaker implantation.

OBJECTIVES

This study sought to describe the epidemiology of SSS.

METHODS

This analysis included 20,572 participants (mean baseline age 59 years, 43% male) in the ARIC (Atherosclerosis Risk In Communities) study and the CHS (Cardiovascular Health Study), who at baseline were free of prevalent atrial fibrillation and pacemaker therapy, had a heart rate of ≥ 50 beats/min unless using beta blockers, and were identified as of white or black race. Incident SSS cases were identified by hospital discharge International Classification of Disease-revision 9-Clinical Modification code 427.81 and validated by medical record review.

RESULTS

During an average 17 years of follow-up, 291 incident SSS cases were identified (unadjusted rate 0.8 per 1,000 person-years). Incidence increased with age (hazard ratio [HR]: 1.73; 95% confidence interval [CI]: 1.47 to 2.05 per 5-year increment), and blacks had a 41% lower risk of SSS than whites (HR: 0.59; 95% CI: 0.37 to 0.98). Incident SSS was associated with greater baseline body mass index, height, N-terminal pro-B-type natriuretic peptide, and cystatin C, with longer QRS interval, with lower heart rate, and with prevalent hypertension, right bundle branch block, and cardiovascular disease. We project that the annual number of new SSS cases in the United States will increase from 78,000 in 2012 to 172,000 in 2060.

CONCLUSIONS

Blacks have a lower risk of SSS than whites, and several cardiovascular risk factors were associated with incident SSS. With the aging of the population, the number of Americans with SSS will increase dramatically over the next 50 years.

Long-term prognosis of patients older than ninety years after permanent pacemaker implantation: does the procedure save the patients?

BACKGROUND

The implantation of a permanent pacemaker (PPM) is life-saving for patients with life-threatening bradycardia. However, the effectiveness and prognosis of PPM implantations for extremely old patients (≥ 90 years old) have not been investigated.

METHODS

From 2001-2012, a total of 108 patients older than 90 years were identified from 2630 consecutive patients receiving PPM implantations in our hospital as the study group. For each study patient, 4 age-, sex-, and comorbidity-matched subjects who did not have the diagnoses of bradyarrhythmias indicated for PPM implantations were selected from the "Taiwan National Health Research Database" to constitute the control group (n = 432). The study end point was all-cause mortality.

RESULTS

The median age of the study population was 91 (interquartile range, 90-93) years. Among the PPM group, 45 patients died during the follow-up with an annual mortality rate of 18.7%. The risk of mortality did not differ significantly between the study and control groups with a hazard ratio of 1.020 (95% confidence interval, 0.724-1.437; P = 0.912) after the adjustment for age and sex. Procedure-related complications occurred in 7.4% of the patients receiving PPM implants, and pocket hematoma was the most common. The preimplantation history of heart failure and cerebrovascular accident, rather than age, were significant predictors of mortality among PPM recipients.

CONCLUSIONS

Nonagenarians with severe bradyarrhythmias could retain the same life expectancies as those without bradyarrhythmias through PPM implantations. Extremely old age (≥90 years) should not be a barrier for PPM implants when indications are present.

Physician procedure volume and complications of cardioverter-defibrillator implantation

BACKGROUND

The outcomes of procedures are often better when they are performed by more experienced physicians. We assessed whether the rate of complications after implantable cardioverter-defibrillator (ICD) placement varied with the volume of procedures a physician performed.

METHODS AND RESULTS

We studied 356 515 initial ICD implantations in the National Cardiovascular Data Registry-ICD Registry, performed by 4011 physicians in 1463 hospitals. We examined the relationship between physician annual ICD implantation volume and in-hospital complications, using hierarchical logistic regression to adjust for patient characteristics, implanting physician certification, hospital characteristics, hospital annual procedure volume, and the clustering of patients within hospitals and by physician. We repeated this analysis for ICD subtypes: single chamber, dual chamber, and biventricular. There were 10 994 patients (3.1%) with a complication after ICD implantation, and 1375 died (0.39%). The complication rate decreased with increasing physician procedure volume from 4.6% in the lowest quartile to 2.9% in the highest quartile (P<0.0001), and the mortality rate decreased from 0.72% to 0.36% (P<0.0001). The inverse relationship between physician procedure volume and complications remained significant after adjusting for patient, physician, and hospital characteristics (OR 1.55 for complications in lowest-volume quartile compared with highest; 95% confidence interval, 1.34-1.79; P<0.0001). This inverse relationship was independent of physician specialty and of hospital volume, was consistent across ICD subtypes, and was also evident for in-hospital mortality.

CONCLUSION

Physicians who implant more ICDs have lower rates of procedural complications and in-hospital mortality, independent of hospital procedure volume, physician specialty, and ICD type.

Are elderly patients at increased risk of complications following pacemaker implantation? A meta-analysis of randomized trials

BACKGROUND

Patients over the age of 75 represent more than half the recipients of permanent pacemakers. It is not known if they have a different risk of complications than younger patients.

METHODS

Patient-level data were pooled from the CTOPP, UKPACE, and Danish pacing trials. These three randomized trials of pacing mode systematically captured early and late complications following pacemaker insertion. Early postimplant complications included lead dislodgement or loss of capture, cardiac perforation, pneumothorax, hematoma, infection, and death. Lead fracture was considered a late complication.

RESULTS

A total of 4,814 patients were included in this analysis, with an average follow-up of 5.1 years. The average age was 76 years and 43% were female. Any early complication occurred in 5.1% of patients ≥75 years of age compared to 3.4% of patients aged <75 years (P = 0.006). This was driven by an increased risk of pneumothorax (1.6% vs 0.8%, P = 0.07) and both atrial and ventricular lead dislodgement/loss of capture (2.0% vs 1.1%, P = 0.07). Early complications were higher in patients receiving atrial-based pacemakers in both age groups (<75 years: 4.6% vs 2.4%; ≥75 years: 6.6% vs 3.7%); however, the relative risk was not influenced by age group. Older patients had a lower risk of lead fracture (3.6% vs 2.7%, P = 0.08).

CONCLUSION

Elderly patients (≥75 years of age) are at increased risk of early postimplant complications but are at lower risk for lead fracture.

The relation between hospital procedure volume and complications of cardioverter-defibrillator implantation from the implantable cardioverter-defibrillator registry

OBJECTIVES

We sought to examine the relationship between hospital implantable cardioverter-defibrillator (ICD) implantation volume and procedural complications in a contemporary, representative population.

BACKGROUND

Hospitals that perform higher volumes of procedures generally have better clinical outcomes.

METHODS

We examined initial ICD implantations between January 2006 and December 2008 at hospitals participating in the NCDR (National Cardiovascular Data Registry) ICD Registry and evaluated the relationship between hospital annual implant volume and in-hospital adverse outcomes.

RESULTS

The rate of adverse events declined progressively with increasing procedure volume (p trend < 0.0001). This relationship remained significant (p trend < 0.0001) after adjustment for patient clinical characteristics, operator characteristics, and hospital characteristics. The volume-outcome relationship was evident for all ICD subtypes, including single-chamber (p trend = 0.004), dual-chamber (p trend < 0.0001), and biventricular ICDs (p trend = 0.02).

CONCLUSIONS

Patients who have an ICD implanted at a high-volume hospital are less likely to have an adverse event associated with the procedure than patients who have an ICD implanted at a low-volume hospital.

Contemporary pacemakers: what the primary care physician needs to know

Pacemaker therapy is most commonly initiated because of symptomatic bradycardia, usually resulting from sinus node disease. Randomized multicenter trials assessing the relative benefits of different pacing modes have made possible an evidence-based approach to the treatment of bradyarrhythmias. During the past several decades, major advances in technology and in our understanding of cardiac pathophysiology have led to the development of new pacing techniques for the treatment of heart failure in the absence of bradycardia. Left ventricular or biventricular pacing may improve symptoms of heart failure and objective measurements of left ventricular systolic dysfunction by resynchronizing cardiac contraction. However, emerging clinical data suggest that long-term right ventricular apical pacing may have harmful effects. As the complexity of cardiac pacing devices continues to grow, physicians need to have a basic understanding of device indications, device function, and common problems encountered by patients with devices in the medical and home environment.

Temporal trends in permanent pacemaker implantation: a population-based study

BACKGROUND

Limited data exist regarding temporal trends in permanent pacemaker (PPM) implantation. To describe trends in incidence and comorbidities of PPM recipients, we conducted a retrospective population-based cohort study over a 30-year period.

METHODS

All 1291 adult residents of Olmsted County, Minnesota, undergoing PPM implantation between 1975 and 2004 were included in the study. Trends in PPM implantation incidence, pacing mode and indication, and comorbidities (via Charlson Comorbidity Index [CCI]) were assessed through the Rochester Epidemiology Project. Permanent pacemaker recipients were compared with age- and sex-matched PPM-free controls from the population.

RESULTS

Adjusted implantation incidence rates increased from 36.6 per 100,000 person-years during 1975 to 1979 to 99 per 100,000 person-years during 2000 to 2004 (P < .0001). After adjusting for age (hazard ratio [HR] 1.06 per year), male sex (HR 1.28), and implant year (HR 0.98), the HR for death among PPM recipients by CCI quartiles was 1.0, 1.79, 2.29, and 3.91 for CCI of 0 to 1 (reference), 2 to 3, 4 to 6, and > or = 7, respectively (P < .0001). Overall, PPM recipients had higher CCI than the population-based controls (P = .04), with higher mean CCI noted since 1990. Mean age-adjusted CCI increased from 3.15 to 4.60 among the cases (P < .0001) and from 3.06 to 3.54 among the age- and sex-matched controls (P = .047).

CONCLUSIONS

There have been significant increases in incidence of PPM implantation over 30 years, and PPM recipients have had an age-independent increase in comorbidities relative to the underlying population, especially over the past 15 years.

Cardiac device implantation in the United States from 1997 through 2004: a population-based analysis

OBJECTIVE

Use of cardiac devices has been increasing rapidly along with concerns over their safety and effectiveness. This study used hospital administrative data to assess cardiac device implantations in the United States, selected perioperative outcomes, and associated patient and hospital characteristics.

METHODS

We screened hospital discharge abstracts from the 1997-2004 Healthcare Cost and Utilization Project Nationwide Inpatient Samples. Patients who underwent implantation of pacemaker (PM), automatic cardioverter/defibrillator (AICD), or cardiac resynchronization therapy pacemaker (CRT-P) or defibrillator (CRT-D) were identified using ICD-9-CM procedure codes. Outcomes ascertainable from these data and associated hospital and patient characteristics were analyzed.

MEASUREMENTS AND MAIN RESULTS

Approximately 67,000 AICDs and 178,000 PMs were implanted in 2004 in the United States, increasing 60% and 19%, respectively, since 1997. After FDA approval in 2001, CRT-D and CRT-P reached 33,000 and 7,000 units per year in the United States in 2004. About 70% of the patients were aged 65 years or older, and more than 75% of the patients had 1 or more comorbid diseases. There were substantial decreases in length of stay, but marked increases in charges, for example, the length of stay of AICD implantations halved (from 9.9 days in 1997 to 5.2 days in 2004), whereas charges nearly doubled (from $66,000 in 1997 to $117,000 in 2004). Rates of in-hospital mortality and complications fluctuated slightly during the period. Overall, adverse outcomes were associated with advanced age, comorbid conditions, and emergency admissions, and there was no consistent volume-outcome relationship across different outcome measures and patient groups.

CONCLUSIONS

The numbers of cardiac device implantations in the United States steadily increased from 1997 to 2004, with substantial reductions in length of stay and increases in charges. Rates of in-hospital mortality and complications changed slightly over the years and were associated primarily with patient frailty.

Pharmacotherapy changes following pacemaker implantation in patients with bradycardia-tachycardia syndrome

The management of bradycardia-tachycardia syndrome (BTS) includes bradycardia and tachyarrhythmia therapy. At present, the treatment for symptomatic bradycardia in BTS patients is permanent cardiac pacing. The pharmacological treatment of atrial tachyarrhythmias comprises of rhythm and rate control, and prevention of thromboembolism. Patients with BTS often require both pacemaker and drug therapy. This article reviews the interactions of pacing and drug therapies in BTS. Drugs that alter cardiac electrophysiological properties may influence pacemaker indications, pacing mode selection, efficacy of pacing algorithms and pacing performance. Pacing by preventing drug-induced bradycardia increases the safety of pharmacotherapy and, thus, allows the intensification of those treatments. Pacing therapy and antiarrhythmic drugs used together as a hybrid therapy have a synergistic effect in the prevention of atrial tachyarrhythmias. Atrial-based pacing may reduce atrial tachyarrhythmia burden, allowing reduction of rhythm and rate control. Contemporary pacemakers' memory functions may help guide rhythm and rate control, as well as anticoagulation pharmacotherapy.

Cardiac pacing in the elderly

Sinus node disease and atrioventricular block are common etiologies of symptomatic bradyarrhythmias in the elderly and remain the leading indications for permanent pacemaker implantation. In fact, the vast majority (>80%) of all pacemakers are implanted in the elderly. Whereas indications of pacemaker therapy have been largely unchanged over the past several years, several questions, such as differences in pacemaker mode selection, remained unanswered. Recent large, randomized, multicenter trials have evaluated the benefits of pacemaker therapy in sinus node dysfunction and acquired atrioventricular block and have provided us with further insights into the difference between atrial- and ventricular-based pacing in these syndromes. Further evaluation of the most appropriate pacing mode in the elderly as well as the outcome of pacing in the elderly are addressed in this review.

Pacemaker stress echocardiography predicts cardiac events in patients with permanent pacemaker

PURPOSE

Noninvasive pacemaker stress echocardiography is a newly introduced method for the diagnosis of coronary artery disease in patients with a permanent pacemaker. The prognostic value of pacemaker stress echocardiography has not been studied.

SUBJECTS AND METHODS

We studied 136 patients (mean age 64+/-12 years) with a permanent pacemaker who underwent pacemaker stress echocardiography for evaluation of coronary artery disease. All patients underwent pacemaker stress echocardiography by external programming (pacing heart rate up to ischemia or target heart rate).

RESULTS

Thirty-one patients (23%) had normal study results. Ischemia was detected in 75 patients (55%). During a mean follow-up of 3.5+/-2.4 years, 35 deaths (26%) (20 the result of cardiac causes) and 2 nonfatal myocardial infarctions (1%) occurred. The annual cardiac death rate was 1.3% in patients without ischemia and 4.6% in patients with ischemia (P=.01). The annual all-cause mortality rate was 3.1% in patients without ischemia and 7% in patients with ischemia (P=.004). The presence of ischemia during pacemaker stress echocardiography was the strongest independent predictor of cardiac death (hazard ratio 4.1, confidence interval 1.2-14.5) and all-cause mortality (hazard ratio 2.7, confidence interval 1.2-6.0) in a multivariable model.

CONCLUSION

Myocardial ischemia during pacemaker stress echocardiography is an independent predictor of cardiac death and all-cause mortality in patients with a permanent pacemaker.

N-terminal brain natriuretic peptide as a screening tool for heart failure in the pacemaker population

AIMS

Assessment of N-terminal brain natriuretic peptide (NT-BNP) as a screening tool for heart failure in patients with a permanent pacemaker.

METHODS AND RESULTS

Consecutive patients undergoing a routine permanent pacemaker assessment were enrolled. Patients underwent medical history and examination, echocardiography and blood sampling for NT-BNP. Analysis was performed on 261 patients (132 DDD, 121 VVI, eight others), mean age 73+/-12 years, range 34-99 years. Seventy two subjects (27%) had heart failure as defined by left ventricular ejection fraction (LVEF) <or=40% and symptoms of heart failure (NYHA class II, III, or IV). Screening with NT-BNP gave a sensitivity of 73% and specificity of 72% for detecting heart failure in all patients [area under the curve (AUC) 0.76, P<0.001, 95% CI 0.69-0.83]. This increased in subjects with a DDD type pacemaker (sensitivity 80%, specificity 66%, AUC=0.8, CI 0.7-0.90) and reduced in subjects with a VVI type pacemaker (sensitivity 66%, specificity 61%, AUC 0.68 CI 0.57-0.78).

CONCLUSION

Symptoms of heart failure are common in patients with pacemakers. Screening with NT-BNP is feasible and assists in the detection of important cardiac co-morbidity, particularly in patients with a DDD type pacemaker.

Epidemiology of pacemaker procedures among Medicare enrollees in 1990, 1995, and 2000

Using Medicare hospital claims records and beneficiary enrollment data, the investigators describe the epidemiology of inpatient pacemaker procedures (International Classification of Diseases, Ninth Revision, Clinical Modification codes 37.80 to 37.89) in Medicare enrollees. From 1990 to 2000, the age-standardized inpatient pacemaker procedure prevalence (per 100,000 enrollees) increased from 325.4 to 504.4 in all Medicare beneficiaries. The prevalence increased significantly with age; was less for women than for men; and was less for blacks, Hispanics, and Asians than for whites.

Physician Management of Pacemaker and Implantable Cardioverter Defibrillator Advisories

This study was designed to determine how physicians manage pacemaker (PM) and implantable cardioverter defibrillator (ICD) recalls and safety alerts (collectively "advisories") and to determine which factors influence physicians' clinical decisions. Although PM and ICD advisories affected over 500,000 patients in the past decade, physician clinical management of advisory devices has not been well studied. Advisories continue to occur frequently and are increasing in number and rate. Five-hundred physician members of the North American Society of Pacing and Electrophysiology (NASPE) were randomly surveyed by mail and were asked to make clinical recommendations regarding the management of various PM and ICD advisory scenarios. One hundred sixty-two physicians (32%) responded to the survey (cardiac electrophysiologist 69%, general cardiologist 22%, surgeon 6%, and other 3%). There was consensus among physicians regarding the management of some PM and ICD advisories but not others. Factors associated with a higher likelihood of physician recommendation for prophylactic advisory device replacement include: ICD implanted for secondary prevention (vs primary prevention, P < 0.001), pacemaker dependence (P < 0.001), prior appropriate ICD therapy (P < 0.001), higher likelihood of device malfunction (P < 0.001), and physician in practice <10 years (P = 0.02). The number of devices implanted or followed per year and physician specialty had no impact on advisory device management. Physician consensus exists regarding the management of some PM and ICD advisories and can be used to guide clinical practice. Substantial differences of opinion, however, are present regarding the management of many other advisories. Evidence based guidelines incorporating the indication for device implantation and the likelihood of device malfunction would greatly facilitate clinical management of PM and ICD advisory devices.

Death in patients with permanent pacemakers for sick sinus syndrome

BACKGROUND

Although more than one million patients in the United States have permanent pacemakers, little is known about their cause of death. We evaluated the cause of death in 404 patients who died in the Mode Selection Trial (MOST).

METHODS

In MOST, patients received a dual-chamber pacemaker randomly programmed to either dual-chamber or ventricular pacing. The circumstances surrounding each death were reviewed by a clinical events committee, which used prospectively defined criteria to adjudicate the cause of death.

RESULTS

A total of 2010 patients with a median age of 74 years were included. After a median follow-up of 33 months, 404 (20%) patients died, including 198 (49%) of noncardiac causes and 143 (35.4%) of cardiac causes. In 63 patients, the cause of death was unknown. Independent predictors of death through the use of a multivariable analysis were (1) demographic factors including age, male sex, and weight; (2) clinical factors including prior myocardial infarction, cardiomyopathy, New York Heart Association class III/IV, and the Charlson Comorbidity Index; and (3) scores from two measures of functional status, the Karnofsky Score and the Mini-Mental State Examination. Independent predictors of cardiovascular death were similar.

CONCLUSIONS

Patients treated with permanent pacemakers for sinus node dysfunction are elderly and have a substantial mortality rate, with more than half the classifiable deaths being noncardiac. Baseline demographic variables and scores from quality-of-life measures can identify patients with the highest risk of death.

Common cardiovascular issues encountered in geriatric critical care

The incidence and prevalence of CV disease is high in the growing US elderly population. It is common for CV disease to be either the primary or secondary problem for elderly patients receiving critical care. The therapeutic options for CV problems experienced in the critical care setting range from medical management with the goal of symptom relief and comfort care to invasive therapies such as PCI, intraaortic balloon pump therapy, invasive monitoring, and cardiac surgery. Age alone is not a contraindication for any of the invasive therapies. Instead, a careful risk-benefit analysis should be performed for each individual patient, taking into consideration physiologic age, comorbid conditions, other disabilities, and an assessment of quality of life. Additionally, the goals (symptom relief, improvement of quality of life, survival benefit) of any therapy should be clearly established for individual patients. End-of-life issues, cardiovascular surgery, and the disabling of ICDs deserve special consideration in the elderly, as these are often challenging issues that will likely be more frequently encountered in critical care settings as science and technology advance.

Complications arising after implantation of DDD pacemakers: the MOST experience

The purpose of this study was to characterize the incidence, time course, frequency, and spectrum of acute and chronic complications arising from dual-chamber pacemaker implantation. This information may serve as a benchmark when comparing complication rates for dual-chamber pacemaker implantation with those for biventricular pacemaker implantation.

Colonic perforation following intraoperative temporary pacemaker implantation

This report describes the case of a 73-year-old man who was referred for consultation for increasing abdominal free air 1 week after he underwent surgery for aortic valve replacement and coronary artery bypass grafting with intraoperative pacemaker implantation. Laparoscopic exploration revealed that the pacemaker wires had passed through the left transverse colon. Although no previous reports of colonic perforation due to pacemaker lead placement was found, this experience suggests that physicians should suspect this complication in patients with increasing free intraabdominal air and peritoneal signs who have recently undergone placement of a temporary cardiac pacing system.

Noninvasive pacemaker stress echocardiography for diagnosis of coronary artery disease: a multicenter study

OBJECTIVE

We evaluated the feasibility, safety, and diagnostic accuracy of noninvasive pacemaker stress echocardiography (PASE) test as a potential alternative to exercise or pharmacologic stress in patients with suspected or known coronary artery disease (CAD).

BACKGROUND

Transesophageal atrial pacing echocardiography is an accurate test for detection of CAD, but its practical impact has been blunted by semi-invasiveness. In the expanding population of patients with permanent pacemakers (PMs), a pacing stress test can be administered noninvasively by external programming of the PM.

METHODS

In a prospective, multicenter, international study design, transthoracic stress-pacing echocardiography was performed in 46 consecutive patients with a permanent PM (33 men, 13 women; age 66.6 +/- 11.1 years) with suspected or known CAD. All patients underwent noninvasive PM-stress test by external programming (10 beats/min increments up to ischemia or target heart rate). Coronary angiography was performed in all patients independently of test results. Significant CAD was defined as >/=50% visually assessed diameter reduction in at least one major epicardial coronary artery. All coronary angiograms were scored by Duke prognostic weight values.

RESULTS

Fifteen patients were stimulated in atrial, and the remaining 31 in ventricular mode during stress. No significant side effects were observed. Echocardiographic images were interpretable in all patients. The average duration of stress was 8.9 +/- 3.5 min. Significant CAD was found in 27 patients. Sensitivity of PASE for identifying patients with significant CAD was 70%, specificity was 90%, and accuracy was 78%. When any abnormal wall motion at rest that remained unchanged at peak stress was regarded as a positive result of PASE, then the sensitivity, specificity, and accuracy levels for identifying patients with significant CAD were 85%, 84%, and 85%, respectively. Four of the eight patients with a false negative did not reach the target heart rate. The Duke values had significant correlation with values of wall motion score index at peak stress (r = 0.67) and with peak heart rate (r = -0.3).

CONCLUSIONS

Noninvasive PASE is a simple, rapid, safe, and diagnostically efficient option for patients with permanent PM and suspected or known CAD.

The role of reperfusion therapy in paced patients with acute myocardial infarction

BACKGROUND/OBJECTIVE

Our purpose was to evaluate the effectiveness of reperfusion therapy among elderly paced patients with acute myocardial infarction (MI). Current guidelines make no recommendation for the use of reperfusion therapy among patients who have a paced rhythm during MI.

METHODS

We evaluated 1954 Medicare beneficiaries 65 years and older treated for acute MI between 1994 and 1996 who had a paced rhythm for use of reperfusion therapy. Use of reperfusion therapy was evaluated for associations with outcomes by logistic regression and Cox proportional hazards models incorporating propensity score analysis.

RESULTS

Reperfusion therapy was used in 171 (8.8%) patients; 70 were treated with primary PTCA and 101 with thrombolytic therapy. Patients who received reperfusion therapy had 30-day mortality rates similar to those who did not receive reperfusion (26.3% vs 25.7%, P =.87). Multivariate adjustment for mortality risk factors and treatment propensity indicated no survival benefit associated with reperfusion therapy at 30 days (relative risk [RR] 1.07, 95% confidence interval [CI] 0.77-1.43) or long-term follow-up (hazard ratio [HR] 0.86, 95% CI 0.68-1.10). Mortality risks varied by type of reperfusion therapy. Patients treated with primary percutaneous transluminal coronary angioplasty were at comparable risk of mortality at 30 days (RR 0.73, 95% CI 0.40-1.23) but at lower risk at long-term follow-up (HR 0.60, 95% CI 0.40-0.88). Mortality risks were unchanged among patients treated with thrombolytics at 30 days (RR 1.32, 95% CI 0.92-1.79) and long-term follow-up (HR 1.08, 95% CI 0.82-1.43).

CONCLUSION

We find suggestive evidence that primary percutaneous transluminal coronary angioplasty provides a long-term survival benefit in the treatment of elderly patients with acute MI who have a paced rhythm.

Cardiac pacing. A review

Pacing is a field of rapid clinical progress and technologic advances. Clinical progress in the 1990s included the refinement of indications for pacing as well as the use of pacemakers for new, nonbradycardiac indications, such as the treatment of cardiomyopathies and CHF and the prevention of atrial fibrillation. Important published data and studies in progress are shedding new light on issues of pacing mode selection, and they may influence future practice significantly. Important technologic advances include development of new rate-adaptive sensors and sensor combinations and the evolution of pacemakers into sophisticated diagnostic devices with the capability to store data and ECGs. Automatic algorithms monitor the patient for appropriate capture, sensing, battery status, and lead impedance, providing better patient safety and pacemaker longevity.

Myocardial perfusion in patients with permanent ventricular pacing and normal coronary arteries

OBJECTIVES

The purposes of this study were to test the specificity of dipyridamole myocardial perfusion scintigraphy in patients with permanent ventricular pacing (PVP) and to evaluate coronary blood flow and reserve in these patients.

BACKGROUND

Permanent ventricular pacing is associated with exercise perfusion defects on myocardial scintigraphy in the absence of coronary artery disease (CAD). On the basis of studies in patients with left bundle brunch block, coronary vasodilation with dipyridamole has been proposed as an alternative to exercise testing for detecting CAD in paced patients, but this approach has never been tested.

METHODS

Fourteen patients with a PVP and normal coronary arteries underwent stress thallium-201 scintigraphy and cardiac catheterization. In these patients and in eight control subjects, coronary flow velocities were measured in the left anterior descending coronary artery (LAD) and in the dominant coronary artery before and after adenosine administration.

RESULTS

In the paced patients, coronary flow velocities in the LAD and in the dominant coronary artery were significantly lower than those in the control subjects. In addition, seven patients showed perfusion defects on dipyridamole thallium-201 single-photon emission computed tomography, with a specificity of 50% for this test. The defect-related artery in these patients had lower coronary flow reserve (2.6 +/- 0.5) as compared with those without perfusion defects (3.9 +/- 1.0, p < 0.05) or the control group (3.5 +/- 0.5, p < 0.05).

CONCLUSIONS

Permanent ventricular pacing is associated with alterations in regional myocardial perfusion. Furthermore, abnormalities of microvascular flow, as indicated by reduced coronary flow reserve in the defect-related artery, are at least partially responsible for the uncertain specificity of dipyridamole myocardial perfusion scintigraphy.

Randomized comparison of J-shaped and straight atrial screw-in pacing leads

OBJECTIVE

To study the importance of a J shape in atrial pacing leads.

PATIENTS AND METHODS

We compared in a randomized controlled study acute and chronic results with 2 steroid-eluting, polyurethane, screw-in atrial lead models that differ only in shape. A total of 208 patients were randomized to have implantation of either a straight atrial lead (n = 105) or a J-shaped atrial lead (n = 103). Patients were followed up for 1 year.

RESULTS

On implantation, there were no significant differences between leads in rates of failure to implant, implant measurements, number of attempts to achieve an acceptable position, and fluoroscopy times. Before discharge and at 3-month and 1-year follow-up, electrical measurements showed no statistical differences between leads. During the first year after implantation, there were 2.9% early dislodgments (< 1 week after implantation) and 2.9% late dislodgments in the straight lead group (5.9% rate of all dislodgments) vs no dislodgments in the J-shaped lead group (P = .01). There was a trend toward higher rates of exit block and lead malfunction in the J-shaped lead group. Rates of pericardial complications, subclavian/axillary thrombosis, and chronic atrial fibrillation were the same in both groups.

CONCLUSIONS

Both leads appear to have an equally favorable performance profile for 1 year of follow-up. The J-shaped lead seems to be more stable and have fewer dislodgments, although it may have a somewhat higher malfunction rate.

The implantable cardioverter-defibrillator

Ventricular arrhythmias remain a major cause of cardiovascular mortality. Therapy for serious ventricular arrhythmias has evolved over the past decade, from treatment primarily with antiarrhythmic drugs to implanted devices. The implantable cardioverter-defibrillator (ICD) is the best therapy for patients who have experienced an episode of ventricular fibrillation not accompanied by an acute myocardial infarction or other transient or reversible cause. It is also superior therapy in patients with sustained ventricular tachycardia (VT) causing syncope or hemodynamic compromise. Controlled clinical trials have confirmed the utility of these devices. As primary prevention, the ICD is superior to conventional antiarrhythmic drug therapy in patients who have survived a myocardial infarction and who have spontaneous, nonsustained ventricular tachycardia, a low ejection fraction, inducible VT at electrophysiologic study, and whose VT is not suppressed by procainamide. The effect of the ICD on survival of other patient populations remains to be proven. The device is costly, but its price is generally accepted to be reasonable. The ICD has been a major advance in the treatment of ventricular arrhythmias.

Serial lead impedance measurements confirm fixation of helical screw electrodes during pacemaker implantation

The purpose of this study was to determine whether serial measurements of helical screw pacemaker lead impedance could reliably confirm electrode fixation in the right atrium and right ventricle. Fixation is generally assessed fluoroscopically, which can be misleading because the myocardium is radiolucent. Alternatively, because the electrical conductivity of blood is greater than that of myocardium, serial measurements of the lead impedance might be expected to show an impedance increase with appropriate fixation of the pacemaker electrode when the electrode becomes embedded in myocardial tissue. Impedance measurements were made during the placement of 23 atrial and 28 ventricular active fixation electrodes in 31 consecutive patients. Impedance measurements were recorded in unipolar and bipolar electrode configurations with the electrode free floating in the chamber, unfixed (with exposed screws) but touching the endocardial surface, and after fixation. No significant impedance differences were found between free-floating and unfixed electrode positions. With fixation, the lead impedance increased significantly in the ventricle (P = 0.0001, unipolar and bipolar) and the atrium (P = 0.0069 unipolar and 0.0052 bipolar). Typical increases, reflected by median values, were 197 ohms unipolar and 203 ohms bipolar in the ventricle and 47 ohms unipolar and 53 ohms bipolar in the atrium for electrodes with permanently exposed or retractable screw designs. Comparing serial measurements of lead impedance before and after electrode fixation is a valid electrical method of confirming appropriate fixation of helical screw electrodes.

Unconventional approaches to cardiac pacing in patients with inaccessible cardiac chambers

BACKGROUND

Transvenous endocardial implantation can be impossible or contraindicated in patients with inaccessible right cardiac chambers. These patients usually undergo epicardial implantation, which has been associated with frequent rising thresholds and limited lead survival. We have used the following two alternative approaches in these patients: (1) transatrial puncture and passage of pacing leads for patients with no access to the right atrium and (2) ventricular pacing from the coronary sinus or its tributaries for patients with inaccessible ventricles. METHODS. We retrospectively reviewed our experience in 9 patients who had those procedures. Five patients had pacing from the coronary sinus, and 4 by transatrial puncture.

RESULTS

Seven of the 9 patients had DDD pacing. Low acute pacing thresholds and satisfactory sensing levels were obtained with both approaches. One instance of high stimulation threshold (20%) occurred in the coronary sinus group and none in the transatrial puncture group. One patient in the transatrial puncture group died from unrelated causes. No malignant arrhythmias, pneumothorax, diaphragmatic pacing, or infectious complications have been observed.

CONCLUSION

These unconventional approaches are safe, relatively simple, and reliable. Although the short-term follow-up is favorable, long-term follow-up is necessary to ascertain the relative merit of these approaches.

Atrioventricular conduction during long-term follow-up of patients with sick sinus syndrome

BACKGROUND

It has been claimed that patients with sick sinus syndrome have an increased risk of developing AV block, but this has never been assessed prospectively. The aim of the present study was to evaluate in a prospective trial AV conduction during the long-term follow-up of patients with sick sinus syndrome.

METHODS

Two hundred twenty-five consecutive patients with sick sinus syndrome and intact AV conduction were randomized to undergo single-chamber atrial pacing (110 patients) or single-chamber ventricular pacing (115 patients). Follow-up after 3 months and then yearly included measurement of the PQ interval and, in patients with atrial pacemakers, determination of the atrial stimulus-Q intervals at pacing rates of 100 and 120 bpm. The occurrence of AV block in the atrial group was recorded. During follow-up (mean, 5.5+/-2.4 years), there was no change in PQ interval in either group and no change in atrial stimulus-Q intervals or Wenckebach block point in the atrial group. Four of 110 patients in the atrial group developed grade 2 to 3 AV block that required upgrading of the pacemaker (0.6% per year). Two of these 4 patients had right bundle-branch block at pacemaker implantation.

CONCLUSIONS

AV conduction, estimated as PQ interval and atrial stimulus-Q interval at atrial pacing rates of 100 and 120 bpm and the Wenckebach block point, remains stable during long-term follow-up. Thus, treatment with single-chamber atrial pacing is safe and can be recommended to patients with sick sinus syndrome without bundle-branch block.