Selected Abstracts

Title: Biventricular pacing in patients with bradycardia and normal ejection fraction

Yu et al (N Engl J Med 2009;361:2123-2134; PMID: 19915220) evaluated whether biventricular (BiV) pacing is superior to right ventricular apical (RVA) pacing in preventing deterioration of left ventricular (LV) systolic function and cardiac remodeling in patients with bradycardia and a normal ejection fraction (EF). In this prospective, double-blind, multicenter study, 177 patients with implantation of a BiV pacemaker were randomized to BiV pacing (89 patients) or RVA pacing (88 patients). The primary end points were the LVEF and LV end-systolic volume. At 12 months, the mean LVEF was significantly lower with RVA pacing than in the BiV pacing (54.8_/-9.1% vs. 62.2_/-7.0%, P_0.001).The LV end-systolic volume was significantly higher in the RVA pacing group than in the BiV group (35.7_/-16.3 ml vs. 27.6_/-10.4 ml, P_0.001). The authors conclude that in patients with normal LVEF, RVA pacing resulted in adverse LV remodeling and in a reduction in the LVEF. These effects were prevented by biventricular pacing.

Title: Cardiac Resynchronization Therapy in Patients with Right Ventricular Pacing-Induced Cardiomyopathy

Background: It is not known whether patients with normal baseline left ventricular (LV) function who develop right ventricular (RV) pacing-induced cardiomyopathy as a result of dual-chamber pacing can benefit from cardiac resynchronization therapy (CRT). We retrospectively assessed the effect of a CRT upgrade on RV pacing-induced cardiomyopathy.
Methods and Results: We reviewed the charts of patients who received a CRT device for RV pacing induced cardiomyopathy. We assessed the effects of CRT on LV function, recovery, and other response parameters. From September 2005 through February 2009, 21 patients (13 men; aged 63 ± 9 years) underwent a treatment upgrade to a CRT system. Before the dual-chamber pacemaker was implanted, the LV ejection fraction (LVEF) was 53 ± 2.3%. After pacing, the LVEF was 31.2 ± 3.8%, the LV end-diastolic dimension (LVEDD) was 5.8 ± 0.5 cm, and B-type natriuretic peptide (BNP) levels were 426 ± 149 pg/mL. The duration of pacing before documentation of pacing-induced cardiomyopathy was 3.8 ± 1.5 months.
All the patients had been on a stable medical regimen for at least 2 months. After the upgrade to CRT, the follow-up time was 4.9 ± 0.9 months. Sixteen patients (76%) reported a significant improvement in their symptoms. After the CRT upgrade, the LVEF increased to 37.4 ± 9.0% (P < 0.01 vs pre-CRT). The LVEDD decreased to 5.0 ± 1.0 cm (P = 0.03 vs pre-CRT), and BNP levels decreased to 139 ± 92 pg/mL (P = 0.08 vs pre-CRT).
Conclusion: A CRT upgrade is an effective treatment for RV pacing-induced cardiomyopathy and should be implemented as soon as the diagnosis is established. Unfortunately, about 24% of our patients did not respond to the upgrade. (PACE 2010; 33:37-40)

Title: Appropriate Evaluation and Treatment of Heart Failure Patients After Implantable Cardioverter-Defibrillator Discharge: Time to Go Beyond the Initial Shock

Multiple clinical trials support the use of implantable cardioverter-defibrillators (ICDs) for prevention of sudden cardiac death in patients with heart failure (HF). Unfortunately, several complicating issues have arisen from the universal use of ICDs in HF patients. An estimated 20% to 35% of HF patients who receive an ICD for primary prevention will experience an appropriate shock within 1 to 3 years of implant, and one-third of patients will experience an inappropriate shock. An ICD shock is associated with a 2- to 5-fold increase in mortality, with the most common cause being progressive HF. The median time from initial ICD shock to death ranges from 168 to 294 days depending on HF etiology and the appropriateness of the ICD therapy. Despite this prognosis, current guidelines do not provide a clear stepwise approach to managing these high-risk patients. An ICD shock increases HF event risk and should trigger a thorough evaluation to determine the etiology of the shock and guide subsequent therapeutic interventions. Several combinations of pharmacologic and device-based interventions such as adding amiodarone to baseline beta-blocker therapy, adjusting ICD sensitivity, and employing antitachycardia pacing may reduce future appropriate and inappropriate shocks. Aggressive HF surveillance and management is required after an ICD shock, as the risk of sudden cardiac death is transformed to an increased HF event risk.
Jacc nov 2009

Title: Upgrade and de novo cardiac resynchronization therapy: Impact of paced or intrinsic QRS morphology on outcomes and survival

BACKGROUND Cardiac resynchronization therapy (CRT) improves outcomes in patients with left bundle branch block (LBBB), but the benefits of CRT in patients with other QRS morphologies or previous pacing are uncertain.
OBJECTIVE The purpose of this study was to describe outcomes in patients with prior right ventricular pacing and non-LBBB morphologies.
METHODS We studied 505 patients who underwent de novo CRT (n _ 338) or CRT upgrade (n _ 167). De novo patients were categorized by underlying QRS morphology: LBBB (67%), right
bundle branch block (RBBB; 11%), intraventricular conduction delay (IVCD; 13%), and QRS _120 ms (9%). Upgrade patients were categorized by the percentage of previous ventricular pacing.
RESULTS Patients were followed for death over a median of 2.6 years (interquartile range 1.6-4.0). New York Heart Association (NYHA) functional class and echocardiographic improvement were similar in de novo and upgrade patients. However, within the de novo group, NYHA improvements were less in patients with RBBB (0.3 _ 0.8; P _ .014) or IVCD (0.2 _ 0.7; P _ .001) than in those with LBBB (0.7 _ 0.8). These patients had less left ventricular functional improvement as well. Survival was comparable after de novo versus upgrade CRT (61% vs 63% at 4 years; P _ .906). No clinical or survival differences were noted in upgrade patients based on the percentage of previous pacing. However, survival in de novo CRT recipients with RBBB (32%) was lower than in those with LBBB (66%; P _.001), and RBBB independently predicted death (hazard ratio 3.5, confidence interval 1.9-6.5; P _.001).
CONCLUSION RBBB and IVCD result in less clinical improvement or worsened survival after CRT. Additional selection criteria may be beneficial in identifying potential responders with RBBB, IVCD, or narrow QRS

Title: Spinal cord stimulation for the treatment of heart failure

Lopshire et al (Circulation 2009;120:286, PMID:19597055) tested the hypothesis that spinal cord stimulation (SCS) reduces the incidence of ventricular tachyarrhythmias in experimental models. The authors implanted implantable cardioverter defibrillator in dogs to monitor heart rhythm. These dogs were then assigned to SCS (delivered at the T4/T5 spinal region for 2 hours 3 times a day), medicine (MED; carvedilol therapy), or control (CTRL; no therapy) group. The results showed that the Left ventricular ejection fraction was significantly improved in the SCS compared with the MED and CTRL groups. The mean number of spontaneous nonsustained ventricular tachyarrhythmias and the occurrence of ischemic ventricular tachyarrhythmias were significantly decreased in the SCS and MED versus CTRL. The authors concluded that SCS significantly improved cardiac contractile function and decreased ventricular arrhythmias in canine heart failure.

Title: ECG in heart failure

Background: Attenuation of electrocardiogram (ECG) QRS complexes is observed in patients with a variety of illnesses and peripheral edema (PERED), and augmentation with alleviation of PERED. Serial ECGs in stable individuals display variation in the amplitude of QRS complexes in leads V1-V6, stemming from careless placement of recording electrodes on the chestwall. Electrocardiographs record only leads I and II, and mathematically derive the other four limb leads in real time. This study evaluated the sum of the amplitudes of ECG leads I and II, along with other sets of ECG leads in the monitoring of diuresis in patients with congestive heart failure (CHF).

Methods: Twenty patients with CHF had ECGs and weights recorded on admission and at discharge. The amplitude of the QRS complexes in all ECG leads were measured and sums of I and II, all limb leads, V1-V6, and all 12 leads were calculated.

Results: There was a good correlation between the weight loss and the increase in the sums of the amplitudes of the QRS complexes from leads I and II (r = 0.55, P = 0.012), and the six limb leads (r = 0.68, P = 0.001), but a poor correlation with the V1-V6 leads (r = 0.04, P = 0.85) and all 12 leads (r = 0.1, P = 0.40).

Conclusions: Sums of the amplitudes of the ECG QRS complexes from leads I and II constitute a reliable, easily obtainable, ubiquitously available, bedside clinical index, which can be employed in the diagnosis, monitoring of management, and follow-up of patients with CHF. (PACE 2009; 32:64-71)

Title: Advances in the treatment of heart failure with a preserved ejection fraction

Introduction :Over the last several years it has become increasingly apparent that many patients with heart failure (HF) have a normal or nearly normal ejection fraction (EF) - described as heart failure with preserved ejection fraction (HF-PEF). Epidemiological studies [1-5] and patient registries have reported a prevalence of up to 40-71% of patients with HF. A recent study [6_] from Olmstead County found that the prevalence of HF-PEF among patients with a discharge diagnosis of HF increased significantly from 1987 to 2001. The prevalence of this condition will likely keep increasing as the prevalence of elderly people with comorbid conditions such as hypertension, diabetes, obesity, and coronary artery disease increases. Although the rates of mortality and morbidity associated with HF-PEF and compared with HF due to depressed EF have varied, there is consensus that HF-PEF is a condition associated with substantial morbidity and mortality. The occurrence of clinical events increases markedly once patients are hospitalized for HF. A recent review [1] suggests that, once hospitalized for HF, patients with HF-PEF have a high rate of rehospitalization; up to a third may be readmitted for HF exacerbation within a year and about 45-60% may be hospitalized by 1 year for any reason. Similarly, once hospitalized, the mortality may be as high as _22-29% at 1 year and _65% at 5 years [6_,7_]. A study [6_] examining secular trends of HF within the Olmstead County found that, although survival improved significantly over time among patients with reduced EF, there was no trend toward improvement among patients with HF-PEF. Thus, there exists an urgent need to develop effective treatment strategies for patients with HF-PEF

Title: Video-Assisted Thoracoscopic Implantation of the Left Ventricular Pacing Lead for Cardiac Resynchronization Therapy

Background: To study the feasibility and efficacy of video-assisted thoracoscopic (VAT) placement of the left ventricular pacing lead for cardiac resynchronization therapy (CRT) where the conventional transvenous coronary sinus approach has failed.

Methods: Seventeen patients underwent the VAT procedure. Indications for CRT were ischemic cardiomyopathy in six patients and nonischemic cardiomyopathy in 11. The procedure was performed under general anesthesia with single-lung ventilation. Three 2-cm incisions were used on the left chest wall to place the screw-in lead near the obtuse marginal arteries high on the lateral wall of the left ventricle (LV).

Results: The VATS approach was successful in 13/17 (76%) patients. Median procedure time was 75 minutes (range 55-135). A learning curve was observed that appeared to plateau at 75 minutes procedure time after four cases. Median length of hospital stay was 2 days (range 2-8) with one patient requiring intensive care. Satisfactory thresholds and impedances of 2.3 0.9 V/0.5 ms and 560 ohms, respectively,were achieved at mean follow-up of 226 days. All patients reported symptomatic benefit with reduction in New York Heart Association score from III preoperatively to II postoperatively.

Conclusions: VAT placement of the epicardial pacing lead is feasible, safe, and efficacious. It should be considered in cases where the transvenous route has failed or as an alternative in prolonged or hazardous transvenous procedures. (PACE 2008; 31:812-818)

Title: Benefit of cardiac resynchronization therapy in atrial fibrillation patients vs. patients in sinus rhythm: the role of atrioventricular junction ablation

Aims:To assess the clinical benefit of cardiac resynchronization therapy (CRT) in patients with atrial fibrillation (AF) compared with patients in sinus rhythm (SR), and to evaluate the impact of atrioventricular junction (AVJ) ablation on the outcome of AF patients undergoing CRT.

Methods and results:We conducted a retrospective analysis of 131 consecutive heart failure (HF)patients who underwent CRT implantation. Three groups were considered: SR (n ¼ 78), AF with AVJ ablation (n ¼ 26), and AF without AVJ ablation (n ¼ 27). Patients were evaluated for the occurrence of cardiac death, hospitalization for HF, and responsiveness to CRT (survival with improvement of _1 New York Heart Association class at 6 months). The three groups showed a significant improvement in functional class. However, the proportion of responders was significantly lower in AF patients without AVJ ablation (52 vs. 79% in SR and 85% in AF with AVJ ablation, P , 0.008). Atrial fibrillation without AVJ ablation was also independently associated with mortality (HR 5.22, 95% CI: 1.60-17.01, P ¼ 0.006) and hospitalization for HF during the first 12 months (HR 6.23, 95% CI: 2.09-18.54, P ¼ 0.001).The outcomes of AF with AVJ ablation patients were similar to the outcomes of patients in SR.

Conclusion:Sinus rhythm and AF patients display similar survival and clinical improvement after CRT implantation, provided that AVJ ablation is performed in the latter.