Cardiac resynchronisation therapy in chronic atrial fibrillation: impact on left atrial size and reversal to sinus rhythm

Unlocking insights: Clinical associations from the largest 6-minute walk test collection via the my Heart Counts Cardiovascular Health Study, a fully digital smartphone platform

BACKGROUND

The six-minute walk test (6MWT) is a prognostic sub-maximal exercise test used clinically as a measure of functional capacity. With the emergence of advanced sensors, 6MWTs are being performed remotely via smartphones and other devices. The My Heart Counts Cardiovascular Health Study is a smartphone application that serves as a digital platform for studies of human cardiovascular health, and has been used to perform 30,475 6MWTs on 8922 unique participants.

OBJECTIVE

As our 30,475 6MWTs represent the largest such collection of data available, we sought to identify associations with measured demographic and clinical variables with 6MWT distance at enrollment and separately determine if use of the My Heart Counts smartphone application led to changes in 6MWT distance.

METHODS AND RESULTS

We present the public data release of our 30,475 6MWTs and the launch of a webpage-based data viewer of summary-level statistics, to compare the functional capacity of an individual by their age, gender, height, weight, and disease status (https://mhc-6mwts.streamlit.app). Using multivariable regression, we report associations of demographic and clinical variables with baseline 6MWT distance (N = 3606), validating prior associations with age, male gender, height, and baseline physical activity level with 6MWT distance. We also report associations of 6MWT baseline distance with employment status (+12.4 m ±4.9 m, P = 0.011) and feeling depressed (-3.65 m, ±0.79 m, P < 0.001). We separately found that cardiovascular disease status was significantly associated with decreased 6MWT distance for atrial fibrillation (-24.9 m ±7.8 m, P = 0.0013), peripheral artery disease (-41.7 m ±12.5 m, P < 0.001), and pulmonary arterial hypertension (-76.3 m ±24.8 m, P = 0.0022). Heart failure was associated with decreased 6MWT distance but was not statistically significant (-25.5 m ±14.5 m, P = 0.078). In a subset of participants who conducted repeat 6MWTs separated by at least 1 week but no greater than 3 months (N = 1129), we found that use of the My Heart Counts app was associated with a statistically significant increase in 6MWT distance (+17.5 m ±7.85 m, P < 0.001).

CONCLUSIONS

We validate previously identified associations from clinic-performed 6MWTs, demonstrating the utility of a mobile method in collecting 6MWT data for clinicians and researchers. We also demonstrate that use of the My Heart Counts app is associated with small, but significant increases in 6MWT distance. Given the importance of 6MWTs in assessment of functional capacity, our publicly-available data will serve an important purpose as a health and disease-specific reference for investigators worldwide.

Conversion to Sinus Rhythm in Refractory Atrial Fibrillation Patients after Atrioventricular Node Ablation with Conduction System Pacing

Background

"Ablate and pace" strategy is a reasonable treatment option in refractory atrial fibrillation (AF) when sinus rhythm (SR) cannot be achieved with catheter ablation or pharmacological therapy. Atrioventricular node ablation (AVNA) combined with conduction system pacing (CSP), with left bundle branch pacing (LBBP) or His bundle pacing (HBP), is gaining recognition since it offers the most physiological activation of the left ventricle. However, the incidence of conversion to SR after AVNA with CSP is not known. The purpose of the investigation was to determine the incidence of spontaneous conversion to SR and its predicting factors in patients undergoing CSP and AVNA.

Methods

Consecutive refractory symptomatic AF patients undergoing AVNA with CSP at our institution between June 2018 and December 2022 were retrospectively analyzed. Twelve lead electrocardiogram (ECG) recordings were analyzed at each outpatient follow-up visit. Echocardiographic and clinical parameters were assessed at baseline and six months after the implantation.

Results

Sixty-eight patients (male 42.6%, age 71 ± 8 years, left ventricular ejection fraction 40 ± 15%) were included. Thirty-seven patients (54.4%) received HBP and 31 (45.6%) LBBP. During follow-up, spontaneous conversion to SR was registered in 6 patients (8.8%); 3 in the HBP group and 3 in the LBBP group. Baseline characteristics of patients who converted to SR did not differ from non-sinus rhythm (NSR) patients except for left atrial volume index (LAVI), which was significantly smaller in the SR group (45 mL/ m 2 (41-51) vs. 60 mL/ m 2 (52-75); p = 0.002). Multiple regression model confirmed an inverse association between LAVI and conversion to SR even after considering other clinically relevant covariates (odds ratio 1.273, p = 0.028). At follow-up, LAVI did not change in any group (SR: p = 0.345; NSR: p = 0.508). Improvement in New York Heart Association (NYHA) class was comparable in both groups.

Conclusions

Spontaneous conversion to SR after AVNA combined with CSP is not uncommon, especially in patients with smaller left atria. Further studies are warranted to clarify which patients should be considered for initial dual-chamber device implantation to provide atrio-ventricular synchrony in case of SR restoration.

Predictors of rhythm outcomes after cardiac resynchronization therapy in atrial fibrillation patients: When should we use an atrial lead?

BACKGROUND

Cardiac resynchronization therapy (CRT) is widely used in atrial fibrillation (AF) patients and could impact rhythm stability.

HYPOTHESIS

We aimed to identify predictors of sinus rhythm (SR) stability or AF progression in a real-word cohort of CRT-AF patients.

METHODS

From 330 consecutive implantable cardioverter-defibrillator implantations due to ischemic or dilated cardiomyopathy, 65 (20%) patients with AF history (paroxysmal, n = 32) underwent a CRT implantation with an atrial electrode and were regularly followed every 4-6 months. Rhythm restoration was attempted for most AF patients based on symptoms, biventricular pacing (BP), and lack of thrombi.

RESULTS

After 33 months, 18 (28%) patients progressed to permanent mode switch (MS≥99%) and 20 (31%) patients had stable SR (MS < 1%). Logistic regression showed that history of persistent AF (OR: 8.01, 95%CI: 2.0-31.7, p = .003) is associated with higher risk of permanent MS. In persistent AF patients, a bigger left atrium (OR: 1.2 per mm, 95%CI: 1.03-1.4, p = .025) and older age (OR: 1.15 per life-year, 95%CI: 1.01-1.3, p = .032) were predictors of future permanent MS. Paroxysmal AF at implantation (OR: 5.96, 95%CI: 1.6-21.9, p = .007) and increased BP (OR: 1.4 per 1%, 95%CI: 1.05-1.89, p = .02) were associated with stable SR. In persistent AF patients, stable SR correlated with higher BP (98 ± 2 vs. 92 ± 8%, p < .001).

CONCLUSION

In patients with AF undergoing CRT implantation, persistent AF, LA dilatation and advanced age relate to future permanent MS (AF), whereas high BP promotes SR stability. These findings could facilitate the management of CRT-AF patients and guide therapy in order to maximize its effect on rhythm.

Electrical wavefront fusion in heart failure patients with left bundle branch block and cardiac resynchronization therapy: Implications for optimization

BACKGROUND

Novel metrics of electrical dyssynchrony based on multi-electrode mapping and ECG-based markers of fusion are better predictors of cardiac resynchronization therapy (CRT) response than QRS duration.

OBJECTIVE

To describe a new methodology for measuring electrical synchrony based on wavefront fusion and electrocardiographic cancellation in patients with CRT and its potential for CRT optimization.

METHODS

Patients with left bundle branch block (LBBB) type conduction and CRT (n = 84) were studied at multiple device settings using an ECG belt (53 anterior and posterior electrodes). The area between combinations of anterior and posterior curves (AUC) was calculated and cardiac resynchronization index (CRI) defined as percent change in AUC compared to LBBB.

RESULTS

In 14 patients with complete heart block or atrial fibrillation, CRI at optimal ventriculo-ventricular delay (VVD) (40 ± 19 ms) was significantly higher than with simultaneous biventricular pacing (BiVp) (90 ± 8.6% vs. 54.2 ± 24.2%, p < 0.001). In all 70 patients paced LV-only, LV-paced wavefront was ahead of native wavefront at short atrio-ventricular delay (AVD) and CRI increased with increase in AVD, peaked, and then decreased. Optimal CRI during LV-only pacing was significantly better than optimal CRI with simultaneous BiVp (89.6 ± 8% vs. 64.4 ± 22%, p < 0.001), and occurred at AVD 68 ± 22 ms less than the atrial-RV sensed interval. With sequential BiVp, best CRI was 83.9 ± 13% (with LV preactivation of 40 ± 20 ms). Best CRI at any setting was markedly better than CRI at standard setting (91.6 ± 7.7% vs. 52.7 ± 23.3, p < 0.001).

CONCLUSION

We describe a novel non-invasive investigational tool that quantifies wavefront fusion and electrical dyssynchrony, and may allow for individualized CRT optimization.

Nonpharmacological Treatment of Atrial Fibrillation: What Is the Role of Device Therapy?

Atrial fibrillation is the most common arrhythmia in the adult population, and its incidence and prevalence are still rising. Cardiac devices are widely used in clinical practice in the management of various rhythm disturbances and heart failure treatment. Many patients who receive a pacemaker, implantable cardioverter-defibrillator, or cardiac resynchronization therapy also experience atrial fibrillation in the course of their life. Therefore, this review aims to describe the role of these devices in the treatment and prevention of atrial fibrillation in the device recipients. In addition, all these implantable devices also serve as permanent ECG (electrocardiogram) monitors, thus providing important information about the presence and characteristics of atrial fibrillation that may or may not be detected by the patient but can modify our therapeutical approach with regard to the stroke prevention.

Reverse atrial electrical remodeling induced by cardiac resynchronization therapy

PURPOSE

Cardiac resynchronization therapy (CRT) has been shown to improve left atrial function; however the effect on reverse electrical remodeling has been poorly evaluated. We hypothesized that CRT might induce reverse atrial electrical remodeling manifesting in the surface ECG as a shortening in P-wave duration.

METHODS

Patients with CRT and more than 92% biventricular pacing at minimum follow-up of 1 year were included in the analysis. Those with prior history of atrial fibrillation (AF) were excluded. Data were recorded for clinical, echocardiographic and ECG variables prior to implant and at least 12 months post implantation. Semiautomatic calipers and scanned ECGs at 300 DPI maximized × 8 were used to measure P-wave duration and diagnose advanced interatrial block (aIAB) during sinus rhythm. The occurrence of AF was assessed through analyses of intracardiac electrograms and clinical presentations.

RESULTS

41 patients were included in the study with mean age of 67.4 ±9.6 years, 71% were male, left atrial diameter 41.1 ± 8.5 mm and LV EF 28.5 ± 6.5%. Over a mean follow up of 55 months, a significant reduction in P-wave duration (142.7 ms vs. 133.1 ms; p < 0.001) was noted. The presence of aIAB was significantly reduced (36% vs. 17%; p = 0.03). The incidence of new onset AF was 36%. Time to AF onset after CRT implantation was not influenced by a reduction in P-wave duration.

CONCLUSION

CRT induces atrial reverse electrical remodeling manifested as a reduction in P-wave duration. Larger studies are needed to determine the impact on AF incidence after CRT implantation.

Advanced Interatrial Block Predicts New Onset Atrial Fibrillation in Patients with Severe Heart Failure and Cardiac Resynchronization Therapy

BACKGROUND

Advanced interatrial block (aIAB) on the surface electrocardiogram (ECG), defined as a P-wave duration ≥120 milliseconds with biphasic (±) morphology in inferior leads, is frequently associated with atrial fibrillation (AF). The aim of this study was to determine whether preoperative aIAB could predict new-onset AF in patients with severe congestive heart failure (CHF) requiring cardiac resynchronization therapy (CRT).

METHODS

Retrospective analysis of consecutive patients with CHF and no prior history of AF undergoing CRT for standard indications. A baseline 12-lead ECG was obtained prior to device implantation and analyzed for the presence of aIAB. ECGs were scanned at 300 DPI and maximized 8×. Semiautomatic calipers were used to determine P-wave onset and offset. The primary outcome was the occurrence of AF identified through analyses of intracardiac electrograms on routine device follow-up.

RESULTS

Ninety-seven patients were included (74.2% male, left atrial diameter 45.5 ± 7.8 mm, 63% ischemic). Mean P-wave duration was 138.5 ± 18.5 milliseconds and 37 patients (38%) presented aIAB at baseline. Over a mean follow-up of 32 ± 18 months, AF was detected in 29 patients (30%) and the incidence was greater in patients with aIAB compared to those without it (62% vs 28%; P < 0.003). aIAB remained a significant predictor of AF occurrence after multivariate analysis (OR 4.1; 95% CI, 1.6-10.7; P < 0.003).

CONCLUSION

The presence of aIAB is an independent predictor of new-onset AF in patients with severe CHF undergoing CRT.

Is CRT pro-arrhythmic? A comparative analysis of the occurrence of ventricular arrhythmias between patients implanted with CRTs and ICDs

Aim and Hypothesis: Despite the proven symptomatic and mortality benefit of cardiac resynchronization therapy (CRT), there is anecdotal evidence it may be pro-arrhythmic in some patients. We aimed to identify if there were significant differences in the incidence of ventricular arrhythmias (VAs) in patients undergoing CRT-D and implantable cardioverter-defibrillators (ICD) implantation for primary prevention indication. We hypothesized that CRT is unlikely to be pro-arrhythmic based on the positive mortality and morbidity data from large randomized trials.

Methods and Results: A retrospective analysis of device therapies for VA in a primary prevention device cohort was performed. Patients with ischemic (IHD) and non-ischemic (DCM) cardiomyopathy and ICD or CRT+ICD devices (CRT-D) implanted between 2005 and 2007 without prior history of sustained VA were included for analysis. VA episodes were identified from stored electrograms and defined as sustained (VT/VF) if therapy [anti-tachycardia pacing (ATP) or shocks] was delivered or non-sustained (NSVT) if not. Of a total of 180 patients, 117 (68% male) were in the CRT-D group, 42% IHD, ejection fraction (EF) 24.5 ± 8.2% and mean follow-up 23.9 ± 9.8 months. 63 patients (84% male) were in the ICD group, 60% IHD, EF 27.7 ± 7.2% and mean follow-up 24.6 ± 10.8 months. Overall, there was no significant difference in the incidence of VA (35.0 vs. 38.1%, p = 0.74), sustained VT (21.3 vs. 28.5%, p = 0.36) or NSVT (12.8 vs. 9.5%, p = 0.63) and no significant difference in type of therapy received for VT/VF: ATP (68 vs. 66.6%, p = 0.73) and shocks (32 vs. 33.3%, p = 0.71) between the CRT-D and ICD groups, respectively.

Conclusion: In patients with cardiomyopathy receiving CRT-D and ICDs for primary prophylaxis, there was no significant difference in the incidence of VA. From this single center retrospective analysis, there is no evidence to support cardiac resynchronization causing pro-arrhythmia.

Left Atrial Volume and the Benefit of Cardiac Resynchronization Therapy in the MADIT-CRT Trial

Background—

Left atrial volume (LAV) is an important marker of heart failure (HF) severity. We hypothesized that LAV independently correlates with clinical outcomes in patients who receive cardiac resynchronization therapy with a defibrillator (CRT-D) and can be used for improved risk assessment in this population.

Methods and Results—

The benefit of CRT-D versus defibrillator-only therapy in reducing the risk of HF or death was assessed by LAV (dichotomized at the upper quartile >52 mL/m 2 ) among 1785 patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT) study. Landmark analysis was used to evaluate the relationship between LAV response to CRT-D and subsequent clinical outcomes. Multivariable analysis showed that patients with a higher baseline LAV experienced 69% ( P <0.001) and 59% ( P =0.02) increased hazard for HF or death and for all-cause mortality, respectively, independently of baseline left ventricular volume. CRT-D was associated with a significant reduction in LAV compared with defibrillator-only therapy (−28% versus −10%, respectively; P <0.001). Landmark analysis showed that after CRT-D implantation each 1% reduction in LAV was independently associated with a corresponding 4% reduction in the hazard of subsequent HF or death ( P <0.001). The assessment of LAV change after CRT implantation improved prediction of clinical response to the device compared with assessment of the corresponding changes in left ventricular volume.

Conclusions—

LAV is an independent correlate of clinical outcomes in mildly symptomatic HF patients treated with CRT-D. CRT exerts pronounced reverse remodeling effects on the left atrium that independently correlate with improved clinical outcomes after device implantation.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00180271.

Cardiac resynchronization therapy mechanisms in atrial fibrillation

This article examines how to assess the reliability of potential techniques for performing optimization of biventricular pacemakers in patients with atrial fibrillation. It explores the magnitude of improvement that is likely to be obtained with the optimization of biventricular pacing in this clinical setting and discusses the lessons that can be learned with regard to the mechanisms of action of biventricular pacing in the general heart failure population.

Is cardiac resynchronization therapy an antiarrhythmic therapy for atrial fibrillation? A systematic review and meta-analysis

The impact of cardiac resynchronization therapy (CRT) on atrial fibrillation (AF) burden is poorly characterized. To assess the influence of CRT on AF, we performed a systematic literature search in MEDLINE using the MeSH headings "cardiac resynchronization therapy" or "cardiac pacing, artificial" and "atrial fibrillation." Selected studies were peer-reviewed and written in English. Most studies enrolled patients meeting traditional CRT criteria. Ten observational studies and two secondary analyses of clinical trials were identified. Although ten studies suggest that CRT favorably impacts AF, one secondary analysis of a clinical trial showed no effect of CRT on new-onset AF. In a meta-analysis of three studies examining the effect of CRT on persistent or permanent AF, the combined rate of conversion from persistent or permanent AF to sinus rhythm was 0.107 (95 % confidence interval 0.069-0.163). Prospective studies, particularly among patients not meeting traditional CRT criteria, are needed.

Role of Atrio-Ventricular Junction Ablation in Symptomatic Atrial Fibrillation for Optimization of Cardiac Resynchronization Therapy

Cardiac resynchronization (CRT) therapy is indicated in patients with at least mildly symptomatic heart failure, left ventricular ejection fraction ≤35% and wide QRS, and has been associated with decreased morbidity and mortality. Unfortunately, approximately 30% of the patients appropriately selected for therapy do not respond to CRT. Among the reasons for non-response, atrial fibrillation (AF) plays a prominent role. AF limits the degree of biventricular pacing during CRT, not only when the ventricular rate is fast and highly irregular, but also during periods of of relatively constant rate, by causing fusion and pseudo-fusion complexes. Importantly, achievement of nearly 100% biventricular pacing is necessary to derive benefit from CRT. A simple, albeit irreversible, method to maximize biventricular pacing in patients with AF who are otherwise eligible for CRT is atrioventricular junction (AVJ) ablation. In this review, we discuss the role of AVJ ablation in CRT optimization in patients with AF. The available evidence from observational non-randomized studies suggests that AVJ ablation in patients with AF qualifying for CRT may offer improvement in heart failure symptoms, better survival, and better cardiac function. In light of the inherent limitations of non-randomized studies, further randomized studies are needed to support this treatment option.

Feasibility and efficacy of electrical cardioversion after cardiac resynchronization implantation in patients with permanent atrial fibrillation

PURPOSE

Patients with permanent atrial fibrillation (AF) who undergo cardiac resynchronization therapy (CRT) may spontaneously recover sinus rhythm during follow-up. We tested the feasibility and efficacy of electrical cardioversion attempted after 3 months of CRT in patients with permanent AF and measured the long-term maintenance of sinus rhythm.

METHODS

Twenty-eight consecutive patients with permanent AF in whom CRT defibrillators had been implanted were scheduled for internal electrical cardioversion after 3 months (group A) and were compared with a control group of 27 patients (group B).

RESULTS

In group A, 22 patients (79 %) were eligible for cardioversion; sinus rhythm was restored in 18 (82 %) of these, with no procedural complications. After 12 months, 16 patients (58 %) in group A were in sinus rhythm, compared with one group B patient who spontaneously recovered sinus rhythm (4 %, p < 0.001). On 12-month evaluation, ejection fraction had improved in both groups, but a reduction in left ventricular end-systolic volume was recorded only in group A patients (p = 0.018 versus baseline).

CONCLUSIONS

In patients with permanent AF, the rhythm control strategy consisting of internal cardioversion, performed by means of the implanted cardioverter-defibrillator after 3 months of CRT, was associated with a high rate of sinus rhythm resumption on long-term follow-up and with a better echocardiographic response to CRT than that seen in patients treated according to a rate control strategy.

Interstitial lung abnormalities and reduced exercise capacity

RATIONALE

The relationship between interstitial lung abnormalities (ILA) and exercise capacity has not been comprehensively evaluated.

OBJECTIVES

To assess the validity of the 6-minute walk test in subjects with ILA, and to examine the association between ILA and 6-minute walk distance (6MWD).

METHODS

Spearman correlation coefficients were used to assess the strength of the relationships between 6MWD and relevant measures of dyspnea, health-related quality of life, and pulmonary function in a cohort of 2,416 people who smoke from the COPDGene study. Unadjusted and adjusted linear and logistic regression models were used to assess the strength of the association between ILA and 6MWD.

MEASUREMENTS AND MAIN RESULTS

In all subjects, and in those with ILA, 6MWD in COPDGene was associated with relevant clinical and physiologic measures. The mean 6MWD in COPDGene subjects with ILA was 386 m (SD, 128 m), and 82% and 19% of subjects with ILA had 6MWDs less than or equal to 500 and 250 m, respectively. ILA was associated with a reduced 6MWD in univariate (-30 m; 95% confidence interval, -50 to -10; P = 0.004) and multivariate models (-19 m; 95% confidence interval, -33 to -5; P = 0.008). Compared with subjects without ILA, subjects with ILA had an 80% and 77% increase in their odds to have a walk distance limited to less than or equal to 500 and 250 m, respectively. Although these findings were dependent on ILA subtype, they were not limited to those with COPD.

CONCLUSIONS

Our study demonstrates that ILA is associated with measurable decrements in the 6MWD of people who smoke. Clinical trial registered with www.clinicaltrials.gov (NCT 00608764).

Atrial fibrillation and heart failure

Atrial fibrillation (AF) is the most common arrhythmia in congestive heart failure (HF) and indicates a worse prognosis. AF increases HF symptoms and increases in prevalence with increasing New York Heart Association class. AF also interferes with the ideal management of HF. Across all HF etiologies, AF may be a marker of disease severity. Yet, controversies exist regarding whether strategies to restore and maintain sinus rhythm can improve outcomes in HF. It is also unclear what the optimal strategy is to suppress the ventricular response to AF in patients with HF. As HF incidence and prevalence continue to rise, the authors sought to reinvestigate current literature that relates AF to HF and examine the impact of therapy on HF and/or AF. The authors performed a literature review using a MEDLINE search from 1966 to the present and included existing literature based on their strength of evidence.

Relation of gender and interatrial dyssynchrony on tissue Doppler imaging to the prediction of the progression to chronic atrial fibrillation in patients with nonvalvular paroxysmal atrial fibrillation

This prospective study aimed to identify the relation of gender and interatrial dyssynchrony on tissue Doppler imaging (TDI) to the prediction of the progression to chronic atrial fibrillation (CAF) in nonvalvular paroxysmal AF (PAF) patients. Nineteen consecutive men and 19 women with nonvalvular PAF were prospectively followed after echocardiography. We measured the interval of time from initiation of the P wave on the electrocardiogram until the beginning of the late diastolic TDI signal at the lateral border of the mitral (P-A'(M)) and the tricuspid annulus (P-A'(T)). Interatrial dyssynchrony was defined as the difference between the P-A'(M) and P-A'(T) intervals (A'(M)-A'(T)). The study endpoint was the onset of CAF (>6 months). Six men developed CAF during a follow-up of 32 +/- 26 months, and 3 women developed CAF during a follow-up of 25 +/- 19 months. Compared to those without CAF, the patients with CAF had significantly longer A'(M)- A'(T) intervals (men: 41 +/- 10 vs 27 +/- 12 ms, women: 64 +/- 4 vs 23 +/- 9 ms; P < 0.01) in both genders. Kaplan-Meier analysis, using cutoff values determined by analysis of receiver-operating characteristics curves, revealed that the progression to CAF was significantly observed more often when A'(M)-A'(T) interval was >34 ms in men and >43 ms in women. This prospective study suggests that nonvalvular PAF men and women with a high risk of developing CAF have "interatrial dyssynchrony" on atrial TDI, whose cutoff values are shorter and may affect the vulnerability of AF in men.

Incidence of paroxysmal atrial tachycardias in patients treated with cardiac resynchronization therapy and continuously monitored by device diagnostics

AIMS

Little is known about the incidence of paroxysmal atrial tachycardias (PAT) in patients with heart failure (HF). The availability of cardiac resynchronization therapy (CRT) devices with extended diagnostics for AT enables continuous monitoring of PAT episodes. The aim of the study was to assess the incidence over time of PAT in HF patients treated with CRT.

METHODS AND RESULTS

Consecutive patients in NYHA functional class III or IV despite optimal drug therapy, QRS duration > or = 130 ms, left ventricular ejection fraction < or = 35%, and left ventricular end-diastolic dimension > or = 55 mm were eligible for enrolment. Patients with permanent or persistent atrial fibrillation (AF) were not included in the study. The first follow-up examination was performed 2 weeks after implantation, to optimize atrial sensing and CRT. Subsequent follow-up examinations were carried out 15 and 28 weeks after implantation, to collect the telemetric data. A total of 173 patients (67 +/- 11 years, M 116) were enrolled. Complete arrhythmia monitoring data were available from 120 patients over a mean follow-up of 183 +/- 23 days. Atrial tachycardia episodes were detected through telemetry in 25 of 120 patients (21%) during at least one follow-up examination. Atrial tachycardia episodes were recorded in 29 and 17% (P = NS) of patients with and without previous history of AF, respectively.

CONCLUSION

More than 20% of the overall HF patient population treated with CRT suffer PAT episodes. Paroxysmal atrial tachycardia may interfere with response to CRT. Therefore, telemetric data may be relevant to drive the appropriate therapy in each patient.

Prediction of transition to chronic atrial fibrillation in elderly patients with nonvalvular paroxysmal atrial fibrillation by transthoracic Doppler echocardiography

BACKGROUND

It is well known that paroxysmal atrial fibrillation (PAF) often precedes the development of chronic atrial fibrillation (CAF).

HYPOTHESIS

The purpose of this study was to determine prospectively whether transthoracic echocardiography is useful for the prediction of the transition to CAF in elderly patients with nonvalvular PAF.

METHODS

Forty-two consecutive elderly patients (> or =65 years) with nonvalvular PAF were prospectively evaluated after undergoing transthoracic echocardiography. The study endpoint was the transition to CAF (AF; > or = 6 mo).

RESULTS

During a follow-up period of 32 +/- 24 mo, 12 patients developed CAF. Patients with CAF had a significantly lower peak A velocity (A) and a higher E/A ratio of the transmitral inflow (TMF) such as a pseudonormalization pattern, and a lower peak atrial reversal wave velocity, higher peak diastolic wave velocity (D), and lower peak systolic/diastolic wave velocity ratio (S/D ratio) of the pulmonary venous flow (PVF). Kaplan-Meier analysis revealed that the transition to CAF was observed more often when A was < or = 70 cm/sec and E/A ratio was > or = 1.07 of TMF, and D was > or = 44 cm/sec and the S/D ratio was < or = 1.34 of PVF. All patients developed CAF when the E/A ratio was > or = 1.15 or the S/D ratio was < or = 0.75.

CONCLUSIONS

This prospective study suggests that elderly patients at high risk for transition to CAF have a pseudonormalization pattern of TMF and a diastolic dominant pattern of PVF, and that transthoracic Doppler estimation of TMF and PVF may be useful in identifying elderly patients at high risk for the transition from nonvalvular PAF to CAF.

Implementation of device therapy (cardiac resynchronization therapy and implantable cardioverter defibrillator) for patients with heart failure in Europe: changes from 2004 to 2008

AIMS

Heart failure (HF) patients increasingly receive device therapy, either an implantable cardioverter defibrillator (ICD) or a biventricular pacemaker, also called cardiac resynchronization therapy (CRT), or a CRT device with an ICD (CRT-D). However, epidemiological data on the use of device therapy in Europe are limited.

METHODS AND RESULTS

Data on implantation rates for conventional pacemakers, ICD, CRT, and CRT-D in 15 Western European countries were obtained from the Eucomed Registry for the 5-year period 2004-2008. Implantation of conventional pacemakers increased by 9% in Europe over the 5 years (reaching 907/million in 2008) and there were significant differences between countries. Implantable cardioverter defibrillator implantations increased by 75% from 80/million in 2004 to 140/million in 2008, and differences between countries were larger than those for conventional pacemakers. Implantation rates for CRT-P alone increased slightly from 2004 to 2006, but remained at 25/million thereafter in Europe overall. The total number of CRT implants (CRT-P and -D) markedly increased from 46/million in 2004 to 99/million in 2008 (115%), but this was mainly due to more CRT-D implants, i.e. an increase in the proportion of CRT-D (from 55% in 2004 to 75% in 2008). Implantation rates for ICD, CRT, and CRT-D remained markedly different throughout the study period between countries.

CONCLUSION

Implantation rates of devices for HF, in particular ICD and CRT-D, have increased significantly between 2004 and 2008 in Europe, but there remain major differences between countries.

Atrial Fibrillation Complicating Congestive Heart Failure: Electrophysiological Aspects And Its Deleterious Effect On Cardiac Resynchronization Therapy

More successful recognition and treatment of cardiovascular risk factors and diseases continues to decrease mortality and increase the proportion of elderly population. Therefore, there are more people with increased risk of developing heart failure and atrial fibrillation in the course of their lives. Atrial fibrillation (AF) can complicate the course of congestive heart failure (HF) leading to acute pulmonary edema. The prevalence of AF, in patients with heart failure, increases with the severity of the disease, reaching up to 40% in advanced cases. In these HF patients, AF is an independent predictor of morbidity and mortality increasing the risk of death and hospitalization. Despite the excellent results obtained with different drugs, the optimal medical treatment can fail in the intention to improve symptoms and quality of life of patients with severe HF. Thus, the necessity to use cardiac devices emerges facing the failure of optimal medical treatment in order to achieve hemodynamic improvement and correction of the physiopathological alterations. Cardiac resynchronization therapy (CRT) can reduce the interventricular and intraventricular mechanical dissynchrony in HF patients. It has been shown that CRT increases the left ventricular filling time, decreases septal dissynchrony, mitral regurgitation, and left ventricular volumes allowing a hemodynamic improvement. However, the development of AF in this setting can avoid the beneficial effects of CRT. Therefore, this manuscript will review the available data on this topic, the electrophysiological aspects of AF, to determine what can be done in the event of an AF complicating congestive HF in CRT patients.

Effect of cardiac resynchronization therapy on conversion of persistent atrial fibrillation to sinus rhythm

BACKGROUND

Spontaneous conversion of persistent atrial fibrillation to sinus rhythm (SR) has anecdotally been reported following cardiac resynchronisation therapy.

OBJECTIVE

This monocenter observational study was designed to estimate the incidence of spontaneous conversion of persistent atrial fibrillation to SR in consecutive patients implanted with a cardiac resynchronisation device.

METHODS AND RESULTS

A total of 46 patients with persistent atrial fibrillation (> or =4 weeks pre-implant), left bundle branch block (QRS > 130 ms), left ventricular ejection fraction <0.35 and NYHA III or IV heart failure were implanted with a cardiac resynchronisation pacemaker or defibrillator and followed for at least 6 months between 6/2000 to 12/2006. During 22 +/- 9 (7-34) months of follow-up, eight out of 46 patients (17%) converted to SR. Spontaneous conversion was encountered in seven cases, whereas one patient converted due to an ICD shock delivered for ventricular tachycardia; in the latter patient, previous ICD shocks had not converted atrial fibrillation. The time interval from device implantation to conversion was 12 +/- 11 (3-31) months. In patients converting to SR, the duration of atrial fibrillation before device implantation was significantly shorter than in patients remaining in atrial fibrillation (15 +/- 13 vs. 53 +/- 58 months, P = 0.001). Echocardiographic parameters such as left ventricular ejection fraction, left ventricular end-diastolic diameter, left atrial diameter did not differ significantly between converting and non-converting patients. However, patients converting to SR showed a significant reduction in systolic pulmonary artery pressure on CRT vs. before CRT (45 +/- 13 vs. 29 +/- 5 mmHg, P = 0.008).

CONCLUSIONS

This pilot study suggests that CRT favors spontaneous conversion of persistent AF to SR in a minority of patients. If confirmed by larger clinical studies, atrial lead implantation would be encouraged in these patients, in order to provide AV synchronous pacing in case of spontaneous conversion or successful cardioversion to SR on cardiac resynchronisation therapy.

Management of atrial fibrillation in patients with heart failure

BACKGROUND

There is a well-documented relationship and a complex interaction between atrial fibrillation (AF) and heart failure. The coexistence of these 2 clinical entities renders their management even more challenging.

METHODS AND RESULTS

We searched current literature to review the management of AF in patients with heart failure. The cornerstones of AF treatment are rate control, cardioversion, and maintenance of sinus rhythm (SR), and prevention of thromboembolism. The issue of rhythm versus rate control remains unresolved. Nonpharmacologic therapies such as radiofrequency catheter ablation of the atrioventricular node with permanent pacemaker implantation, curative catheter ablation of AF, and cardiac resynchronization therapy are emerging and may alter the management of these patients.

CONCLUSION

Treatment of atrial fibrillation in the setting of heart failure encompasses a variety of approaches including drugs, devices, and ablation. Larger randomized trials are required to clarify the management of such patients.

A randomized comparison of triple-site versus dual-site ventricular stimulation in patients with congestive heart failure

OBJECTIVES

We compared the effects of triple-site versus dual-site biventricular stimulation in candidates for cardiac resynchronization therapy.

BACKGROUND

Conventional biventricular stimulation with a single right ventricular (RV) and a single left ventricular (LV) lead is associated with persistence of cardiac dyssynchrony in up to 30% of patients.

METHODS

This multicenter, single-blind, crossover study enrolled 40 patients (mean age 70 +/- 9 years) with moderate-to-severe heart failure despite optimal drug treatment, a mean LV ejection fraction of 26 +/- 11%, and permanent atrial fibrillation requiring cardiac pacing for slow ventricular rate. A cardiac resynchronization therapy device connected to 1 RV and 2 LV leads, inserted in 2 separate coronary sinus tributaries, was successfully implanted in 34 patients. After 3 months of biventricular stimulation, the patients were randomly assigned to stimulation for 3 months with either 1 RV and 2 LV leads (3-V) or to conventional stimulation with 1 RV and 1 LV lead (2-V), then crossed over for 3 months to the alternate configuration. The primary study end point was quality of ventricular resynchronization (Z ratio). Secondary end points included reverse LV remodeling, quality of life, distance covered during 6-min hall walk, and procedure-related morbidity and mortality. Data from the 6- and 9-month visits were combined to compare end points associated with 2-V versus 3-V.

RESULTS

Data eligible for protocol-defined analyses were available in 26 patients. No significant difference in Z ratio, quality of life, and 6-min hall walk was observed between 2-V and 3-V. However, a significantly higher LV ejection fraction (27 +/- 11% vs. 35 +/- 11%; p = 0.001) and smaller LV end-systolic volume (157 +/- 69 cm(3) vs. 134 +/- 75 cm(3); p = 0.02) and diameter (57 +/- 12 mm vs. 54 +/- 10 mm; p = 0.02) were observed with 3-V than with 2-V. There was a single minor procedure-related complication.

CONCLUSIONS

Cardiac resynchronization therapy with 1 RV and 2 LV leads was safe and associated with significantly more LV reverse remodeling than conventional biventricular stimulation.

Cardiac resynchronization therapy response is associated with shorter duration of atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is commonly associated with heart failure. The benefit of cardiac resynchronization therapy (CRT) on atrial remodeling has been demonstrated. However, biventricular pacing did not reduce the global incidence of AF. We evaluated the relationship between CRT response and AF duration.

METHODS

We retrospectively analyzed data from 96 patients (59 +/- 15 years; 78% male) who underwent CRT. All patients had class III-IV New York Heart Association (NYHA) symptoms despite maximal medical therapy, left ventricular ejection fraction (LVEF) < or = 35%, QRS >130 ms, and sinus rhythm before implantation. CRT response in patients who survived at six months of follow-up was defined as: (1) no hospitalization for heart failure and (2) improvement of one or more grades in the NYHA classification.

RESULTS

CRT responders (n = 54) and non-responders (n = 42) had similar baseline characteristics, including the incidence of persistent AF within six months before implantation. Six months after implantation, when compared to baseline, CRT responders exhibited a significant decrease in left atrial size (47.5 +/- 7.1 mm vs 44.6 +/- 7.7 mm, P < 0.01) and in the incidence of persistent AF (17% vs 2%, P = 0.02). At six months, CRT responders demonstrated shorter mean AF duration (7.5 +/- 43.3 hours vs 48.8 +/- 129.0 hours, P = 0.03) and lower incidence of persistent AF (2% vs 19%, P = 0.004) compared to nonresponders.

CONCLUSION

CRT response is associated with a reversal of atrial remodeling and a shorter AF duration.

Management of atrial fibrillation

Atrial fibrillation is the most common sustained cardiac rhythm disorder, and confers a substantial mortality and morbidity from stroke, thromboembolism, heart failure, and impaired quality of life. With the increasingly elderly population in the developed world, as well as improvements in the management of myocardial infarction and heart failure, the prevalence of atrial fibrillation is increasing, resulting in a major public-health problem. This Review aims to provide an overview on the modern management of atrial fibrillation, with particular emphasis on pharmacological and non-pharmacological approaches. Irrespective of a rate-control or rhythm-control strategy, stroke prevention with appropriate thromboprophylaxis still remains central to the management of this common arrhythmia. Electrophysiological approaches could hold some promise for a curative approach in atrial fibrillation.

Usefulness of preimplantation B-type natriuretic peptide level for predicting response to cardiac resynchronization therapy

Nearly 1/3 of patients with heart failure (HF) fail to respond to cardiac resynchronization therapy (CRT). The purpose of this study was to evaluate the value of preimplantation brain natriuretic peptide (BNP) in predicting the clinical response to CRT. We retrospectively analyzed 164 patients who underwent CRT. Patients with New York Heart Association functional class III or IV HF symptoms despite maximal medical therapy, who were not on inotropic medications, had left ventricular ejection fraction < or =35%, and QRS duration >130 ms were included in the study. CRT response in patients who survived at 6-month follow-up was defined as no HF hospitalization and improvement of > or =1 grades in the New York Heart Association classification. BNP assays were performed before implantation and at 6-month follow-up. Patients had ischemic (47%) or nonischemic (53%) cardiopathy. Responders (n = 107) and nonresponders (n = 57) had similar baseline characteristics. Cardiac death and hospitalization for HF occurred in 5 (4.7%) and 18 (31.6%) patients, respectively. CRT responders compared with nonresponders exhibited higher preimplantation BNP levels (800 +/- 823 vs 335 +/- 348 pg/ml, p = 0.0002) and a significant reduction in the QRS duration after implantation (-6 +/- 34 vs +7 +/- 32 ms, p = 0.048). The preimplantation BNP was the only independent predictor of the CRT response (p = 0.001). A BNP value > or =447 pg/ml demonstrated a sensitivity of 62% and specificity of 79% in identifying CRT response. In a subgroup of 41 patients who underwent Doppler tissue imaging analysis, the preimplantation BNP was higher in patients presenting with intraventricular dyssynchrony (845 +/- 779 vs 248 +/- 290 pg/ml, p = 0.04). In conclusion, the preimplantation BNP value independently predicts CRT response and was superior to QRS duration reduction in identifying CRT responders.

Implantable cardioverter-defibrillator therapy and risk of congestive heart failure or death in MADIT II patients with atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) contributes to increased risk of morbidity and mortality. Data regarding the effectiveness of implantable cardioverter-defibrillator (ICD) therapy in AF patients are limited.

OBJECTIVES

The purpose of this study was to evaluate the effectiveness of ICD therapy in patients with AF enrolled in the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) and to identify their risk for the combined endpoint of hospitalization for congestive heart failure or death.

METHODS

The MADIT II cohort served as the source for data on the clinical course, cardiac events, and effectiveness of ICD therapy in AF patients.

RESULTS

AF was found as baseline rhythm at enrollment in 102 (8%) MADIT II patients. In comparison to 1,007 patients in sinus rhythm, AF patients were older, more frequently were males, had wider QRS complex, and had higher blood urea nitrogen and creatinine levels (P <.05 for all parameters). ICD therapy was effective in reducing 2-year mortality in AF patients from 39% in 41 conventionally treated patients to 22% in 61 ICD-treated patients (hazard ratio = 0.51, P = .079). However, the combined endpoint of hospitalization for heart failure or death at 2 years was 69% and 59%, respectively (NS). AF was predictive for the combined endpoint of heart failure hospitalization or death (hazard ratio = 1.68, P = .040). New-onset AF in patients with baseline sinus rhythm was associated with increased risk of mortality (hazard ratio = 2.70, P <.001).

CONCLUSION

MADIT II patients with AF benefit from ICD therapy, which reduces their mortality. MADIT II patients with AF are at high risk for developing heart failure.