Cardiac resynchronization therapy: “Nonresponders” and “hyperresponders”

Pacing induced cardiomyopathy: recognition and management

Right ventricle (RV) apex continues to remain as the standard pacing site in the ventricle due to ease of implantation, procedural safety and lack of convincing evidence of better clinical outcomes from non-apical pacing sites. Electrical dyssynchrony resulting in abnormal ventricular activation and mechanical dyssynchrony resulting in abnormal ventricular contraction during RV pacing can result in adverse LV remodelling predisposing some patients for recurrent heart failure (HF) hospitalisation, atrial arrhythmias and increased mortality. While there are significant variations in the definition of pacing induced cardiomyopathy (PIC), combining both echocardiographic and clinical features, the most acceptable definition for PIC would be left ventricular ejection fraction (LVEF) of <50%, absolute decline of LVEF by ≥10% and/or new-onset HF symptoms or atrial fibrillation (AF) after pacemaker implantation. Based on the definitions used, the prevalence of PIC varies between 6% and 25% with overall pooled prevalence of 12%. While most patients undergoing RV pacing do not develop PIC, male sex, chronic kidney disease, previous myocardial infarction, pre-existing AF, baseline LVEF, native QRS duration, RV pacing burden, and paced QRS duration are the factors associated with increased risk for PIC. While conduction system pacing (CSP) using His bundle pacing and left bundle branch pacing appear to reduce the risk for PIC compared with RV pacing, both biventricular pacing and CSP may be used to effectively reverse PIC.

Clinical Outcomes of Permanent Left Bundle Branch Area Pacing in Patients With Left Bundle Branch Block and Left Ventricular Ejection Fraction >35 vs. ≤35%

Aims

The present study aimed to compare the effects of left bundle branch area pacing (LBBAP) on cardiac function and clinical outcomes in patients with left bundle branch block (LBBB) and left ventricular ejection fraction (LVEF) >35 vs. ≤35%.

Methods and Results

Thirty-six consecutive patients with LBBB and LVEF <50% were enrolled. All patients were followed up for a mean of 6 months. The successful LBBAP was defined as a paced QRS complex presented as right bundle branch block (RBBB) morphology and QRSd < 130 ms. Echocardiography parameters, pacing parameters and clinical outcomes were collected. The successful LBBAP was achieved in 77.8% of all cases (28/36). In LVEF > 35% group (70 ± 8 years, 9 male), the success rate was 81.0% (17/21). QRSd significantly decreased from 174 ± 23 ms to 108 ± 13 ms (P < 0.001). The pacing threshold and R-wave amplitude were 0.6 ± 0.2 V @ 0.5 ms and 12 ± 7 mV, respectively. In LVEF ≤ 35% group (69 ± 5 years, 9 male), the success rate was 73.3% (11/15) with QRSd decreasing from 188 ± 25 ms to 107 ± 11 ms (P < 0.001). The hyperresponders to LBBAP (functional recovery and LVEF ≥ 50%) in LVEF > 35% group was 52.9%, which were almost twice of that in LVEF ≤ 35% group (33.3%). Whether patients had LBBAP or left ventricular septal pacing (LVSP), patients in the LVEF > 35% group showed significantly lower incidence of heart failure hospitalizations or death from any cause (hazard ratio in LVEF > 35% group, 0.22; 95%CI, 0.06 to 0.75, P = 0.011).

Conclusions

LBBAP can significantly shorten the QRSd and improve cardiac function in LBBB patients with either LVEF > 35 or ≤ 35%. LBBAP should be considered as an effective therapy for preventing the deterioration of cardiac function in early-stage heart failure patients with LBBB and LVEF > 35%.

Prognostic effects of longitudinal changes in left ventricular ejection fraction with cardiac resynchronization therapy

Aims

Left ventricular ejection fraction (LVEF) is considered an indicator of cardiac resynchronization therapy (CRT). Longitudinal studies on the predictive value of LVEF are scarce. We aimed to comprehensively evaluate the prognostic role of LVEF in the outcomes of Chinese patients with CRT.

Methods and results

Three hundred ninety‐two patients were divided into three tertiles of LVEF: ≤25%, 25–30%, and 30–35%, and four groups by LVEF changes: <0% (negative response); ≥0% and ≤5% (non‐response); >5% and ≤15% (response); and >15% (super‐response). One hundred six patients were super‐responders. During a median follow‐up of 3.6 years, 141 reached the composite endpoint. Odds ratios (ORs) for super‐response depicted a reversed U‐shaped relationship for baseline LVEF with a peak at 25–30%. Independent predictors of super‐response were smaller left atrial diameter [odds ratio 0.897, 95% confidence interval (CI) 0.844–0.955, P = 0.001], smaller left ventricular end‐diastolic diameter (OR 0.937, 95% CI 0.889–0.989, P = 0.018), and higher estimated glomerular filtration rate (OR 1.018, 95% CI 1.001–1.035, P = 0.042) in Tertile 1; atrial fibrillation (OR 0.278, 95% CI 0.086–0.901, P = 0.033), left bundle branch block (OR 4.096, 95% CI 1.046–16.037, P = 0.043), and left ventricular end‐diastolic diameter (OR 0.929, 95% CI 0.876–0.986, P = 0.016) in Tertile 2; while female sex (OR 2.778, 95% CI 1.082–7.132, P = 0.034) and higher systolic blood pressure (OR 1.045, 95% CI 1.013–1.079, P = 0.006) in Tertile 3. An inverse association with the composite endpoint was found in Tertile 1 vs. Tertile 2 (hazard ratio 1.934, 95% CI 1.248–2.996, P = 0.003). The prognostic effects of CRT response in Tertile 3 and Tertile 1 varied significantly (P for trend = 0.017 and <0.001). Among three tertiles in super‐responders, event‐free survival was similar (P for trend = 0.143).

Conclusions

Left ventricular ejection fraction of 25–30% is associated with a better prognosis of super‐response. Predictors of super‐response are different for LVEF tertiles. CRT responses would have better prognostic performance than LVEF tertiles at baseline, which should be considered when clinicians screening eligible patients for CRT.

[Continuation of ICD treatment at the time of device exchange without adequate treatment?]

INTRODUCTION

Due to improved treatment of heart failure, patients are older and have more comorbidities at the time of an elective device exchange. This leads to higher rates of complications and represents an opportunity for re-evaluation of the implantable cardioverter defibrillator (ICD) treatment.

OBJECTIVE

This article reviews the current literature regarding the indications for continued ICD therapy and device exchange in patients who have never received adequate treatment through the ICD.

MATERIAL AND METHODS

Patients with primarily prophylactic indications, who have not received adequate treatment and have shown significant improvement in the left ventricular ejection fraction (LVEF) >35%, have a significantly lower risk of ventricular arrythmia (VA) after device exchange. Although further ventricular events can occur in these patients, the continuation of ICD treatment should be individually discussed in cases of high age and increased comorbidities. In female patients with a non-ischemic cardiac myopathy and an almost normalized LVEF, mostly during cardiac resynchronization therapy (CRT), a discontinuation of ICD treatment or downgrading to CRT with pacemaker (CRT-P) treatment should be discussed.

CONCLUSION

At the time of an elective device exchange for primarily prophylactic indications, the possibility to discontinue ICD treatment can be discussed with patients who have not experienced adequate treatment. Additional factors, such as LVEF, age, sex and comorbidities of the patient should be taken into consideration in order to make an individualized decision. As prospective randomized studies are lacking, it is not possible to give generally valid recommendations.

Does 'super-responder' patients to cardiac resynchronization therapy still have indications for neuro-hormonal antagonists? Evidence from long-term follow-up in a single center

Background

Whether cardiac resynchronization therapy super-responders (CRT-SRs) still have indications for neuro-hormonal antagonists or not remains uninvestigated.

Methods

We reviewed clinical data from 376 patients who underwent CRT implantation in Fuwai Hospital from 2009 to 2015 and followed up to 2017. CRT-SRs were defined by an improvement of the New York Heart Association functional class and left ventricular ejection fraction to ≥ 50% in absolute values at 6-month follow-up. All CRT-SRs were assigned into two groups on the basis of whether persistently receiving neuro-hormonal antagonists (NHA) (defined as angiotensin-converting enzyme inhibitors/angiotensin receptor blockers and β-blockers) after 6-month follow-up and then we compared long-term outcome.

Results

A total of 60 patients met criteria for super-response. One of thirteen (7.7%) CRT-SRs without NHA had all-cause death, which also occurred in 2 of 47 (4.3%) in CRT-SRs with NHA (P = 0.526). However, 3 of 13 (23.1%) CRT-SRs without NHA had heart failure (HF) hospitalization, 1 of 47 (2.1%) CRT-SRs with NHA had this endpoint (P = 0.040). Besides, subgroup analysis indicated that, for ischemic etiology group, CRT-SRs receiving NHA had considerably lower incidence of HF hospitalization than those without NHA (0 vs. 75%, P = 0.014), which was not observed in non-ischemic etiology group (2.6% vs. 0, P = 1.000) during long-term follow-up.

Conclusions

Our study found that for ischemic etiology, compared with CRT-SRs with NHA, CRT-SRs without NHA were associated with a higher risk of HF hospitalization. However, for non-ischemic etiology, we found that CRT-SRs with NHA or without NHA at follow-up were associated with similar outcomes, which needed further investigation by prospective trials.

Cardiac resynchronization therapy (CRT) device replacement considerations: upgrade or downgrade? A complex decision in the current clinical setting

There are limited data about the management of patients presenting for elective generator replacements in the setting of previously implanted cardiac resynchronization therapy (CRT) devices that are nearing end-of-life. The individual patient's clinical status and concomitant morbidities may evolve so that considerations may include not only replacement of the pulse generator, but also potentially changing the type of device [e.g. downgrading CRT-defibrillator (CRT-D) to CRT-pacemaker (CRT-P) or ICD or upgrading of CRT-P to CRT-D]. Moreover, the clinical evidence for CRT-D/CRT-P implantation may change over time, with ongoing research and availability of new trial data. In this review we discuss the ethical, clinical and financial implications related to CRT generator replacements and the need for additional clinical trials to better understand which patients should undergo CRT device downgrading or upgrading at the time of battery depletion.

The incidence and outcomes of delayed response to cardiac resynchronization therapy

BACKGROUND

The incidence and clinical outcomes of delayed response to cardiac resynchronization therapy (CRT) have not been well clarified. We aimed to observe the incidence and prognosis of delayed response and to identify its possible mechanisms.

METHODS

A total of 115 CRT patients were retrospectively analyzed in our study. Patients who met the enrollment criteria were divided into two groups: group A, conventional responders who showed response at 1-year follow-up, and group B, delayed responders who showed response after 1-year follow-up. CRT response was defined as an absolute increase of ≥10% in left ventricular ejection fraction.

RESULTS

Fifty-two patients (61 ± 12 years, 37 male) experienced conventional response to CRT and 17 patients (63 ± 11 years, 10 male) experienced delayed response. The mean follow-up time was 5.2 ± 2.4 years. The incidence of delayed response was 14.8% (17/115). All-cause mortality and hospitalization rates for heart failure were similar for delayed and conventional responders. Multivariate logistic regression analysis revealed that scar burden > 35% was an independent predictor of CRT delayed response (odds ratio 8.794, P  =  0.038).

CONCLUSIONS

A significant proportion of patients demonstrated delayed response to CRT. The delayed responders had a good prognosis that was similar to that of conventional responders. More scar burden might be related to the incidence of delayed response.

Cellular and Molecular Aspects of Dyssynchrony and Resynchronization

Dyssynchronous contraction of the ventricle significantly worsens morbidity and mortality in patients with heart failure (HF). Approximately one-third of patients with HF have cardiac dyssynchrony and are candidates for cardiac resynchronization therapy (CRT). The initial understanding of dyssynchrony and CRT was in terms of global mechanics and hemodynamics, but lack of clinical benefit in a sizable subgroup of recipients who appear otherwise appropriate has challenged this paradigm. This article reviews current understanding of these cellular and subcellular mechanisms, arguing that these aspects are key to improving CRT use, as well as translating its benefits to a wider HF population.

Short-term outcome of cardiac resynchronization therapy - a comparison between newly implanted and chronically right ventricle-paced patients

BACKGROUND

Cardiac resynchronization therapy (CRT) is considered as a standard adjunct therapy in symptomatic patients with congestive heart failure (CHF) who have a prolonged QRS. There is an increasing number of patients who do not receive de novo CRT devices but are upgraded from right ventricular (RV) pacing to biventricular stimulation. We wanted to evaluate the benefit of CRT in patients with chronic RV pacing in comparison to previously non-paced heart failure patients.

METHODS

One hundred and sixty-five patients who had their device newly implanted (group I) and 116 who were upgraded from previously implanted RV pacing systems (group II) at Mayo Clinic Hospital were retrospectively analyzed. Clinical and echocardiographic response to CRT was evaluated. Mean follow-up time was 290±250days.

RESULTS

Baseline characteristics did not differ between the two groups of patients. Clinical response rate was identical in Groups I and II (65 vs. 65%, respectively; P=0.98) and echocardiographic response rate was similar in both groups of patients (64 vs. 62%; P=0.80). Post-implant QRS increased in group I and was reduced in group II (5 (27.4) vs. -20.0 (33.9) ms; P<0.001). NYHA class improvement (-0.7 (0.6) vs. -0.7 (0.6), P=0.81), LV ejection fraction increase (9.2 (12.9) vs. 8.2 (9.9)%; P=0.55) and LV end-systolic volume reduction (-34.5 (50.7) vs. -25.7 (47.4)%; P=0.28) were comparable in both groups.

CONCLUSIONS

Chronically RV-paced patients who receive CRT have similar short-term benefits when compared with patients with new CRT implantations.

The arterial baroreflex effectiveness index in risk stratification of chronic heart failure patients who are candidates for cardiac resynchronization therapy

INTRODUCTION

Baroreflex function is an independent marker of prognosis in heart failure (HF). However, little is known about its relation to response to cardiac resynchronization therapy (CRT). The aim of this study is to assess arterial baroreflex function in HF patients who are candidates for CRT.

METHODS

The study population consisted of 25 patients with indication for CRT, aged 65±10 years, NYHA functional class ≥III in 52%, QRS width 159±15 ms, left ventricular ejection fraction (LVEF) 29±5%, left ventricular end-systolic volume (LVESV) 150±48 ml, B-type natriuretic peptide (BNP) 357±270 pg/ml, and peak oxygen consumption (peak VO2) 18.4±5.0 ml/kg/min. An orthostatic tilt test was performed to assess the baroreflex effectiveness index (BEI) by the sequence method. This group was compared with 15 age-matched healthy individuals.

RESULTS

HF patients showed a significantly depressed BEI during tilt (31±12% vs. 49±18%, p=0.001). A lower BEI was associated with higher BNP (p=0.038), lower peak VO2 (p=0.048), and higher LVESV (p=0.031). By applying a cut-off value of 25% for BEI, two clusters of patients were identified: lower risk cluster (BEI >25%) QRS 153 ms, LVESV 129 ml, BNP 146 pg/ml, peak VO2 19.0 ml/kg/min; and higher risk cluster (IEB ≤25%) QRS 167 ms, LVESV 189 ml, BNP 590 pg/ml, peak VO2 16.2 ml/kg/min.

CONCLUSIONS

Candidates for CRT show depressed arterial baroreflex function. Lower BEI was observed in high-risk HF patients. Baroreflex function correlated closely with other clinical HF parameters. Therefore, BEI may improve risk stratification in HF patients undergoing CRT.

The role of mutations in the SCN5A gene in cardiomyopathies

The SCN5A gene encodes the alpha-subunit of the Nav1.5 ion channel protein, which is responsible for the sodium inward current (INa). Since 1995 several hundred mutations in this gene have been found to be causative for inherited arrhythmias including Long QT syndrome, Brugada syndrome, cardiac conduction disease, sudden infant death syndrome, etc. As expected these syndromes are primarily electrical heart diseases leading to life-threatening arrhythmias with an "apparently normal heart". In 2003 a new form of dilated cardiomyopathy was identified associated with mutations in the SCN5A gene. Recently mutations have been also found in patients with arrhythmogenic right ventricular cardiomyopathy and atrial standstill. The purpose of this review is to outline and analyze the following four topics: 1) SCN5A genetic variants linked to different cardiomyopathies; 2) clinical manifestations of the known mutations; 3) possible molecular mechanisms of myocardial remodeling; and 4) the potential implications of gene-specific treatment for those disorders. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.

New-onset left bundle branch block-associated idiopathic nonischemic cardiomyopathy and left ventricular ejection fraction response to guideline-directed therapies: The NEOLITH study

BACKGROUND

Left ventricular ejection fraction (LVEF) response to guideline-directed medical therapy (GDMT) and to early cardiac resynchronization therapy (CRT) in new-onset idiopathic nonischemic cardiomyopathy (NICM) and left bundle branch block (LBBB) is not well described. CRT is recommended if LVEF remains ≤35% after at least 3 months of GDMT.

OBJECTIVE

The purpose of this study was to describe LVEF response to GDMT at 3 months and to early CRT in new-onset LBBB-associated idiopathic NICM.

METHODS

A retrospective cohort study was performed in subjects with new-onset idiopathic NICM, LVEF ≤35%, and LBBB or narrow (<120 ms) QRS complex morphology. LVEF response between groups was evaluated with log-binomial and linear regression. LVEF response within groups was evaluated using the paired Student t test.

RESULTS

In 102 subjects (70 with narrow QRS complex and 32 with LBBB), post-GDMT LVEF was >35% in 39 narrow QRS complex subjects (56%) and 2 LBBB subjects (6%) (P < .0001). The absolute difference between post-GDMT LVEF and initial LVEF was greater in the narrow QRS complex group (16.1% ± 14.6% vs. 3.3% ± 10.7%; P < .0001). Narrow QRS complex, referenced to LBBB, was significantly associated with post-GDMT LVEF >35% (relative risk 10.30; 95% confidence interval 2.63-40.27; P = .0008) and absolute difference between post-GDMT LVEF and initial LVEF (β = 16.296; standard error = 2.977; P < .0001) in final multivariable analyses. CRT super-response, defined as post-CRT LVEF ≥50%, was observed in 8 of LBBB subjects (35%) who received CRT.

CONCLUSION

GDMT did not significantly improve LVEF in new-onset LBBB-associated idiopathic NICM at 3 months. Most remained candidates for CRT, and a high percentage were super-responders. Optimal timing for CRT implantation requires further investigation.

What We Can Learn from "Super-responders"

This review discusses the state of the art of knowledge to help decision making in patients who are candidates for cardiac resynchronization therapy (CRT) and to analyze the long-term total and cardiac mortality, sudden death, and CRT with a defibrillator intervention rate, as well as the evolution of echocardiographic parameters in patients with a left ventricular (LV) ejection fraction of greater than 50% after CRT implantation. Owing to normalization of LV function in super-responders, the need for a persistent defibrillator backup is also considered.

Cardiac Resynchronization Therapy in Women

The benefits of cardiac resynchronization therapy (CRT) on the outcomes of patients with heart failure are unquestionable. Women are under-represented in all CRT studies. Most of the available data show that CRT produces a greater clinical benefit in women than men. In several studies, women have left bundle branch block more frequently than men. Women have a remarkably high (90%) CRT response over a wide range of QRS lengths (130-175 milliseconds). Use of a QRS duration of 150 milliseconds as the threshold for CRT prescription may deny a life-saving therapy to many women likely to benefit from CRT.

Cellular and Molecular Aspects of Dyssynchrony and Resynchronization

Dyssynchronous contraction of the ventricle significantly worsens morbidity and mortality in patients with heart failure (HF). Approximately one-third of patients with HF have cardiac dyssynchrony and are candidates for cardiac resynchronization therapy (CRT). The initial understanding of dyssynchrony and CRT was in terms of global mechanics and hemodynamics, but lack of clinical benefit in a sizable subgroup of recipients who appear otherwise appropriate has challenged this paradigm. This article reviews current understanding of these cellular and subcellular mechanisms, arguing that these aspects are key to improving CRT use, as well as translating its benefits to a wider HF population.

Long-Term Echocardiographic Response to Cardiac Resynchronization Therapy in Initial Nonresponders

OBJECTIVES

The aim of this study was to investigate the frequency and clinical implications of a delayed echocardiographic response to cardiac resynchronization therapy (CRT).

BACKGROUND

Long-term prognosis for CRT patients is routinely based on the assessment of echocardiograms after 6 to 12 months of therapy. Some patients, however, may require a longer period of therapy before echocardiographic improvements are detectable.

METHODS

This observational study included all patients with heart failure (HF) receiving a CRT device at a single center from 2003 to 2011. Eligible patients met current indications and had technically adequate echocardiograms from before implantation, approximately 1 year after implantation (mid-term), and ≥3 years after implantation (long-term). A positive echocardiographic response to CRT was defined as a reduction in left ventricular end-systolic volume ≥15%. All-cause mortality was compared for patients in 3 response groups: mid-term responders, long-term responders, and nonresponders.

RESULTS

During this study, 294 patients met the study criteria. Of the 120 patients who were nonresponders after 1 year, 52 (43%) experienced a delayed positive response. Delayed, long-term responders had mortality and hospitalization rates similar to mid-term responders and significantly lower than nonresponders.

CONCLUSIONS

Among patients surviving at least 3 years after implantation of a CRT device and with echocardiographic follow-up, a significant portion of nonresponders after 1 year of CRT experience a delayed echocardiographic response after a longer period of time. Survival and hospitalization rates were similar for all echocardiographic responders, regardless of the time at which the response occurred.

Cardiac Resynchronisation Therapy and Heart Failure: Persepctive from 5P Medicine

Chronic heart failure is still a major challenge for healthcare. Currently, cardiac resynchronisation therapy (CRT) has been incorporated into the updated guideline for patients with heart failure, left ventricular ejection fraction ≤35 % and prolonged QRS duration. With 20 years of development, the concept of 'from bench to bedside' has been illustrated in the field of CRT. Given the fact that the indications of CRT keep evolving, the role of CRT is not limited to the curative method for heart failure. We therefore summarise with the perspective of 5P medicine - preventive, personalised, predictive, participatory, promotive, to review the benefit of CRT in the prevention of heart failure in those with conventional pacemaker indications, the individualised assessment of patient's selection, the predictor of responders of CRT, and the obstacles hindering the more application of CRT and the future development of this device therapy.

Clinical characteristics and predictors of super-response to cardiac resynchronization therapy: a combination of predictive factors

BACKGROUND

Patients with greater improvement of cardiac function after cardiac resynchronization therapy (CRT) implantation are identified as "super-responders." However, it remains unclear which kind of preimplant assessments could accurately predict outcomes after CRT. Thus, we aimed to examine the essential predicting factors for super-response to CRT, and to construct an accurate predictable model.

METHODS

We retrospectively analyzed the CRT patients who underwent implantation at Nagoya University Hospital. Super-responders are defined as those who show a relative reduction in left ventricular end-systolic volume ≥30% after 6 months of CRT.

RESULTS

Eighty patients (mean age, 67.8 ± 10.2 years) were included. Twenty-two patients received upgrading procedure to CRT implantation. Six months after the implantation, 29 patients (36%) were super-responders. Multiple logistic regression analysis shows that consistent right ventricular pacing with a previous device (odds ratio [OR] 7.28, 95% confidence interval [CI] 1.52-34.9; P = 0.013), lack of prior history of ventricular arrhythmia (OR 5.32, 95% CI 1.52-18.6; P = 0.009), and smaller left atrial diameter (LAD) (OR 0.92, 95% CI 0.86-0.98; P = 0.014) are independent predictors for CRT super-responders. The use of a combination of these predictive factors could increase the certainty with which a greater response to CRT is predicted and the presence of such a combination could improve prognosis.

CONCLUSION

Greater response to biventricular pacing occurs more frequently in patients with consistent right ventricular pacing, lack of prior history of ventricular arrhythmia, and smaller LAD. An association between patient background characteristics and a super-response to CRT was also identified.

[Right ventricular septal stimulation would produce similar bi-ventricular dyssynchrony as does apical stimulation in patients with normal ejection fraction]

OBJECTIVE

To determine in patients with normal ejection fraction, undergoing permanent VVI pacing, if medial septal stimulation has lower dyssynchrony than apical stimulation assessed by echocardiography.

METHOD

A prospective trial, 19 patients>70 years old, scheduled for VVI pacemaker implantation for complete degenerative atrioventricular block, ventricular frequency<50beat per minute and ejection fraction≥45%. Patients with atrial fibrillation, heart failure, left bundle branch block and QRS durations longer than 120milliseconds in surface electrocardiogram with sinus rhythm were excluded. Patients were randomized to apical implantation group A: 47% and septal implantation group B: 53%. Echocardiographic parameters were measured previous to the implant, 48h, 5 and 48 months after implantation.

RESULTS

No patients had diagnosis of ischemic cardiomyopathy or heart failure. Echocardiographic parameters for interventricular dyssynchrony between groups were A: 14.44±19.76msec vs. B: 9±36.45msec; A: 6.11±62.11msec vs. B: 13±38.31msec; A: 77±53.51msec vs. B: 24.29±80.90msec, P=NS). For interventricular dyssynchrony were A: 46.44±19.76msec vs. B: 42.20±29.56msec; A: 45.33±45.67msec vs. B: 29.80±44.66msec; A: 46,38±20 msec vs. B: 21±27.20msec, P=NS) at 48h, 5 and 48 months, respectively.

CONCLUSION

Apical site of stimulation does not increase ventricular dyssynchrony rate in patients with preserved ejection fraction. Septal stimulation showed decreased trend in interventricular dyssynchrony.

Predictors and outcomes of "super-response" to cardiac resynchronization therapy

BACKGROUND

Cardiac resynchronization therapy (CRT) has been shown to improve heart failure (HF) symptoms and survival. We hypothesized that a greater improvement in left-ventricular ejection fraction (LVEF) after CRT is associated with greater survival benefit.

METHODS AND RESULTS

In 693 patients across 2 international centers, the improvement in LVEF after CRT was determined. Patients were grouped as non-/modest-, moderate-, or super-responders to CRT, defined as an absolute change in LVEF of ≤5%, 6-15%, and >15%, respectively. Changes in New York Heart Association (NYHA) functional class and left ventricular end-diastolic dimension (LVEDD) were assessed for each group. There were 395 non-/modest-, 186 moderate-, and 112 super-responders. Super-responders were more likely to be female and to have nonischemic cardiomyopathy, lower creatinine, and lower pulmonary artery systolic pressure than non-/modest- and moderate-responders. Super-responders were also more likely to have lower LVEF than non-/modest-responders. There was no difference in NYHA functional class, mitral regurgitation grade, or tricuspid regurgitation grade between groups. Improvement in NYHA functional class (-0.9 ± 0.9 vs -0.4 ± 0.8 [P < .001] and -0.6 ± 0.8 [P = .02]) and LVEDD (-8.7 ± 9.9 mm vs -0.5 ± 5.0 and -2.4 ± 5.8 mm [P < .001 for both]) was greatest in super-responders. Kaplan-Meier survival analysis revealed that super-responders achieved better survival compared with non-/modest- (P < .001) and moderate-responders (P = .049).

CONCLUSIONS

Improvement in HF symptoms and survival after CRT is proportionate to the degree of improvement in LV systolic function. Super-response is more likely in women, those with nonischemic substrate, and those with lower pulmonary artery systolic pressure.

A clinical phenotype of adverse response to biventricular pacing: a case series

BACKGROUND

Biventricular pacing is an established therapy for patients with heart failure with reduced left ventricular ejection fraction and prolonged QRS duration. However, there are few reports on the adverse effects of biventricular pacing.

METHODS

Three patients who deteriorated rapidly following biventricular pacing (heart transplantation/ventricular assist device within 3 months of device implantation) were identified. The clinical, echocardiographic, and functional characteristics before and after device implantation were evaluated. The acute hemodynamic effects of biventricular pacing were assessed by cardiac catheterization.

RESULTS

Preimplant assessment showed biventricular dysfunction, pulmonary hypertension, and relatively narrow QRS duration. The time from device implantation to assessment was 62, 58, and 42 days. All three patients developed right bundle branch block (RBBB)-type QRS morphology, deterioration in right ventricular (RV) function, and functional capacity in association with rapid clinical decline. Acutely, biventricular pacing resulted in higher right atrial pressure, pulmonary wedge pressure, lower cardiac output, and RV stroke work in all three patients.

CONCLUSIONS

A phenotype of adverse response to biventricular pacing is characterized by relatively narrow QRS duration, RV dysfunction, and pulmonary hypertension. Clinical decline is rapid and associated with the development of RBBB-type morphology, worsening of pulmonary hemodynamics, and RV dysfunction with biventricular pacing.

Follow-up of patients with new cardiovascular implantable electronic devices: are experts' recommendations implemented in routine clinical practice?

BACKGROUND

A 2008 expert consensus statement outlined the minimum frequency of follow-up of patients with cardiovascular implantable electronic devices (CIEDs).

METHODS AND RESULTS

We studied 38 055 Medicare beneficiaries who received a new CIED between January 1, 2005, and June 30, 2009. The main outcome measure was variation of follow-up by patient factors and year of device implantation. We determined the number of patients who were eligible for and attended an in-person CIED follow-up visit within 2 to 12 weeks, 0 to 16 weeks, and 1 year after implantation. Among eligible patients, 42.4% had an initial in-person visit within 2 to 12 weeks. This visit was significantly more common among white patients than black patients and patients of other races (43.0% versus 36.8% versus 40.5%; P<0.001). Follow-up within 2 to 12 weeks improved from 40.3% in 2005 to 55.1% in 2009 (P<0.001 for trend). The rate of follow-up within 0 to 16 weeks was 65.1% and improved considerably from 2005 to 2009 (62.3%-79.6%; P<0.001 for trend). Within 1 year, 78.0% of the overall population had at least 1 in-person CIED follow-up visit.

CONCLUSIONS

Although most Medicare beneficiaries who received a new CIED between 2005 and 2009 did not have an initial in-person CIED follow-up visit within 2 to 12 weeks after device implantation, the rate of initial follow-up improved appreciably over time. This CIED follow-up visit was significantly more common in white patients than in patients of other races.

Optimizing electrode placement for hemodynamic benefit in cardiac resynchronization therapy

BACKGROUND

Research is needed to explore the relative benefits of alternative electrode placements in biventricular and left ventricular (LV) pacing for heart failure with left bundle branch block (LBBB).

METHODS

A fast computational model of the left ventricle, running on an ordinary laptop computer, was created to simulate the spread of electrical activation over the myocardial surface, together with the resulting electrocardiogram, segmental wall motion, stroke volume, and ejection fraction in the presence of varying degrees of mitral regurgitation. Arbitrary zones of scar and blocked electrical conduction could be modeled.

RESULTS

Simulations showed there are both sweet spots and poor spots for LV electrode placement, sometimes separated by only a few centimeters. In heart failure with LBBB, pacing at poor spots can produce little benefit or even reduce pumping effectiveness. Pacing at sweet spots can produce up to 35% improvement in ejection fraction. Relatively larger benefit occurs in dilated hearts, in keeping with the greater disparity between early and late activated muscle. Sweet spots are typically located on the basal to midlevel, inferolateral wall. Poor spots are located on or near the interventricular septum. Anteroapical scar with conduction block causes little shift in locations for optimal pacing. Hearts with increased passive ventricular compliance and absence of preejection mitral regurgitation exhibit greater therapeutic gain. The durations and wave shapes of QRS complexes in the electrocardiogram can help predict optimum electrode placement in real time.

CONCLUSIONS

Differences between poor responders and hyperresponders to cardiac resynchronization therapy can be understood in terms of basic anatomy, physiology, and pathophysiology. Computational modeling suggests general strategies for optimal electrode placement. In a given patient heart size, regional pathology and regional dynamics allow individual pretreatment planning to target optimal electrode placement.

Extraordinarily favorable left ventricular reverse remodeling through long-term cardiac resynchronization: super-response to cardiac resynchronization

BACKGROUND

Some chronic heart failure (CHF) patients show remarkable improvement in left ventricular (LV) remodeling after cardiac resynchronization therapy (CRT), for unclear reasons. This study aimed at identifying predictors of an extraordinarily favorable response to CRT.

METHODS

We studied 136 CRT patients (104 men, median 66 years, QRS 162 ms, left ventricular ejection fraction 24 ± 7%, 70% coronary disease, all left bundle branch block [LBBB]). We measured LV end diastolic diameter (LVEDD) before and after long-term (9.4 ± 6.3 months) CRT. At baseline, LV pre-ejection interval (LVPEI), interventricular mechanical delay (IVMD), LV dyssynchrony (standard deviation of electromechanical delays [SDEMD] in eight LV segments), exercise capacity (pVO(2)), and ventilatory efficiency (VE/VCO(2)) were assessed. Patients with a LVEDD reduction beyond the 80th percentile (high responders [HR]) were compared to low responders (LR).

RESULTS

In the HR group (n = 22), LVEDD was reduced from 71 to 52 mm (LR 64-61 mm, P < 0.001). HR had predominantly nonischemic heart disease (HR: 72%, LR: 44%, P = 0.019), tended to have a wider QRS (HR: 178 ms, LR: 162 ms, P = 0.066), had a longer LVPEI (HR: 179 ms, LR: 155 ms, P = 0.004), wider IVMD (HR: 60 ms, LR 48 ms, P = 0.05), larger LVEDD (P = 0.002), higher SDEMD (HR: 69 ms, LR: 46 ms, P = 0.044), but higher pVO(2) (HR: 17.5 mL/min/kg, LR: 13.5 mL/kg/min, P = 0.025) and lower VE/VCO(2) (HR: 31, LR: 35, P = 0.043), all compared to LR patients.

CONCLUSION

Extraordinarily favorable reverse LV remodeling through CRT in CHF and LBBB appears to require a particularly dilated LV due to nonischemic heart disease with pronounced electromechanical alteration, but with a fairly preserved functional capacity before CRT.

Reverse left ventricular remodeling is more likely in non ischemic cardiomyopathy patients upgraded to biventricular stimulation after chronic right ventricular pacing

BACKGROUND

Chronic right ventricular (RV) apical pacing may lead to left ventricular (LV) dyssynchrony and LV dysfunction. In heart failure due to RV pacing, upgrading to biventricular stimulation (CRT) can improve NYHA Class and LV function. A proportion of patients do not respond to upgrading. Aim was to assess whether etiology of LV dysfunction accounts for responses to CRT in RV-paced patients.

METHODS

Sixty-two patients treated by CRT, under RV pacing from 50.2 ± 5.4 months, were studied. Cause of LV dysfunction was non-ischemic (NIC) in 28 and ischemic cardiomyopathy (IC) in 34 patients. Clinical and conventional echocardiographic parameters were available within 1 month before RV pacing, within 1 month before CRT and at 12 ± 2 months of follow-up (FU).

RESULTS

Decreased LVEF (from 37.0 ± 8.8 to 25.6 ± 6.1%, p <0.001), increased LV end-systolic dimensions (LVESD) (from 48.1 ± 8.6 to 55.2 ± 7.9 mm, p <0.001) and worsened NYHA Class (from 1.9 ± 1.1 to 3.2 ± .6, p < 0.005) were found before CRT, compared to pre RV-pacing. After CRT, 44/62 patients showed a ≥ 1 NYHA Class improvement; >10% decrease in LVESD was observed in 24 patients: 5 with IC, 19 with NIC (p < .0.001). The association between cause of LV dysfunction with >10% decrease in LVESD remained highly significant (p < 0.001) adjusting for pre-CRT QRS duration, NYHA Class, LVEF, LVESD, treatment or RV pacing duration.

CONCLUSIONS

CRT improves functional class even after long-lasting pacing. Reverse remodeling is evident in a small population, more likely with NIC.

Temporal pattern of left ventricular structural and functional remodeling following reversal of volume overload heart failure

Current surgical management of volume overload-induced heart failure (HF) leads to variable recovery of left ventricular (LV) function despite a return of LV geometry. The mechanisms that prevent restoration of function are unknown but may be related to the timing of intervention and the degree of LV contractile impairment. This study determined whether reduction of aortocaval fistula (ACF)-induced LV volume overload during the compensatory stage of HF results in beneficial LV structural remodeling and restoration of pump function. Rats were subjected to ACF for 4 wk; a subset then received a load-reversal procedure by closing the shunt using a custom-made stent graft approach. Echocardiography or in vivo pressure-volume analysis was used to assess LV morphology and function in sham rats; rats subjected to 4-, 8-, or 15-wk ACF; and rats subjected to 4-wk ACF followed by 4- or 11-wk reversal. Structural and functional changes were correlated to LV collagen content, extracellular matrix (ECM) proteins, and hypertrophic markers. ACF-induced volume overload led to progressive LV chamber dilation and contractile dysfunction. Rats subjected to short-term reversal (4-wk ACF + 4-wk reversal) exhibited improved chamber dimensions (LV diastolic dimension) and LV compliance that were associated with ECM remodeling and normalization of atrial and brain natriuretic peptides. Load-independent parameters indicated LV systolic (preload recruitable stroke work, Ees) and diastolic dysfunction (tau, arterial elastance). These changes were associated with an altered α/β-myosin heavy chain ratio. However, these changes were normalized to sham levels in long-term reversal rats (4-wk ACF + 11-wk reversal). Acute hemodynamic changes following ACF reversal improve LV geometry, but LV dysfunction persists. Gradual restoration of function was related to normalization of eccentric hypertrophy, LV wall stress, and ECM remodeling. These results suggest that mild to moderate LV systolic dysfunction may be an important indicator of the ability of the myocardium to remodel following the reversal of hemodynamic overload.