The Central Role of Left Atrium in Heart Failure

In past cardiovascular medicine, the attention to the left ventricle-identified as the only indicator and determinant of healthy or unhealthy cardiac conditions- has systematically hidden the role of the left atrium (LA). The recent advances in cardiovascular imaging have provided a better understanding of LA anatomy, physiology, and pathology, making us realize that this functional structure is far from being an innocent spectator. We now know that the LA's mechanical and neuro-hormonal properties play a relevant part in several cardiovascular diseases, including atrial fibrillation, ischemic heart disease, valvular heart disease, and heart failure. The present review aims to describe the role of LA in the specific setting of heart failure. We provide currently available information on LA structure and function and summarize its role as a determinant of symptoms, prognosis, and potential therapeutic target in heart failure patients.

A Predictive Model for Super-Response to Cardiac Resynchronization Therapy: The QQ-LAE Score

Objectives

It is important to identify super-responders who can derive most benefits from cardiac resynchronization therapy (CRT). We aimed to establish a scoring model that can be used for predicting super-response to CRT.

Methods

We retrospectively reviewed 387 CRT patients. Multivariate logistic regression analysis was performed to identify predictors for super-response (defined as an absolute increase in left ventricular ejection fraction of ≥15% at 6-month follow-up) and to create a score model. Multivariate Cox proportional-hazard regression analysis was conducted to assess associations with the long-term endpoint (defined as cardiac death/heart transplant, heart failure (HF) hospitalization, or all-cause death) across the score categories at follow-up.

Results

Among 387 patients, 109 (28.2%) met super-response. In multivariable analysis, 5 independent predictors (QQ-LAE) were identified: prior no fragmented QRS (odds ratio (OR) = 3.10 (1.39, 6.94)), QRS duration ≥170 ms (OR = 2.37 (1.35, 4.12)), left bundle branch block (OR = 2.57 (1.04, 6.37)), left atrial diameter <45 mm (OR = 3.27 (1.81, 5.89)), and left ventricular end-diastolic dimension <75 mm (OR = 4.11 (1.99, 8.48)). One point was attributed to each predictor, and three score categories were identified. The proportion of super-response after 6-month CRT implantation in patients with scores 0-3, 4, and 5 was 14.6%, 40.3%, and 64.1%, respectively (P < 0.001). Patients with score 5 had an 88% reduction in the risk of cardiac death/heart transplant (P=0.042), a 71% reduction in the risk of HF hospitalization (P=0.048), and an 89% reduction in the risk of all-cause mortality (P=0.028) compared to patients with scores 0-3.

Conclusions

The QQ-LAE score can be used for prediction of super-response to CRT and selection of most suitable patients in clinical practices.

The left atrium and the right ventricle: two supporting chambers to the failing left ventricle

Heart failure (HF) is mainly caused by left ventricular (LV) impairment of function, hence detailed assessment of its structure and function is a clinical priority. The frequent involvement of the left atrium (LA) and the right ventricle (RV) in the overall cardiac performance has recently gained significant interest with specific markers predicting exercise intolerance and prognosis being proposed. The LA and RV are not anatomically separated from the LV, while the LA controls the inlet the RV shares the interventricular septum with the LV. Likewise, the function of the two chambers is not entirely independent from that of the LV, with the LA enlarging to accommodate any rise in filling pressures, which could get transferred to the RV via the pulmonary circulation. In the absence of pulmonary disease, LA and RV function may become impaired in patients with moderate-severe LV disease and raised filling pressures. These changes can often occur irrespective of the severity of systolic dysfunction, thus highlighting the important need for critical assessment of the function of the two chambers. This review evaluates the pivotal role of the left atrium and right ventricle in the management of HF patients based on the available evidence.

Atrial Dyssynchrony: A New Predictor for Atrial High-Rate Episodes in Patients with Cardiac Resynchronization Therapy

Background: Heart failure may induce atrial dyssynchrony. We aim to investigate whether preimplantation left atrial (LA) dyssynchrony could predict newly detected atrial high-rate episodes (AHRE) after receiving cardiac resynchronization therapy defibrillator (CRT-D). Methods: We conducted a retrospective analysis of consecutive patients who received CRT-D for standard indications and without a history of atrial fibrillation. The standard deviation of the time-to-peak strain in each LA segment during ventricular systole (SDs) and late diastole (SDa) were calculated to quantify LA dyssynchrony using two-dimensional speckle tracking echocardiography before device implantation. Patients were divided into the AHRE group and the AHRE-free group, depending on the presence of AHRE during device interrogation. Results: Thirty-one patients (28%) had newly detected AHRE during a mean follow-up of 21 ± 9 months. Patients in the AHRE group had higher SDs (8.2 ± 2.6% vs. 6.3 ± 2.3%, p < 0.001) and SDa (5.4 ± 1.8% vs. 4.1 ± 1.4%, p < 0.001) values before implantation than patients in the AHRE-free group. In the multivariate logistic analysis, both SDs (OR 1.325, 95% CI: 1.074–1.636, p =0.009) and SDa (OR: 1.499, 95% CI: 1.071–2.098, p= 0.018) were independent predictors of newly detected AHRE. At a cutoff value of 7.4% for SDs and 5.3% for SDa, the Kaplan-Meier survival analysis showed that patients with higher SDs and SDa had significantly increased risks of newly detected AHRE after receiving CRT-D. Conclusions: Dyssynchronous LA lengthening and contraction could assist in the prediction of newly detected AHRE in patients with CRT-D.

Heart Failure Duration Combined with Left Atrial Dimension Predicts Super-Response and Long-Term Prognosis in Patients with Cardiac Resynchronization Therapy Implantation

Background

Response to cardiac resynchronization therapy (CRT) varies significantly among patients. This study aimed to identify baseline characteristics that could predict super-response to CRT and to evaluate the long-term prognosis in super-responders.

Methods

We retrospectively reviewed the data of 73 consecutive patients who received CRT. Patients were considered as super-responders after 6-month follow-up when NYHA class reduction to I or II combined with left ventricular ejection fraction (LVEF) ≥ 50% was observed. Patients were divided into super-responders group and non-super-responders group. All-cause mortality or hospitalization for heart failure (HF) was referred to the combined end point.

Results

17 (23.3%) patients were super-responders. HF duration, left atrial dimension (LAD), and left bundle branch block (LBBB) were independent predictors of super-response to CRT. The combination of HF duration and LAD could provide more robust prediction of super-response than standalone HF duration (0.899 versus 0.789, Z = 2.207, P = 0.027) or standalone LAD (0.899 versus 0.775, Z = 2.487, P = 0.013). super-responders had excellent LV reverse remodeling. The cumulative incidences of combined end point were significantly lower in the super-responders group, LAD ≤ 42mm group, and combination of HF duration ≤ 48 months and LAD ≤ 42mm group. LBBB remained associated with a lowered risk of the combined end point (HR: 0.19, 95% CI: 0.07-0.57, P = 0.003), whereas LAD was associated with a raised risk of the combined end point (HR: 1.09, 95% CI: 1.02-1.17, P = 0.014).

Conclusions

HF duration, LAD, and LBBB independently predicted super-response. The combination of HF duration and LAD makes more robust prediction of CRT super-response. Super-responders had excellent LV reverse remodeling and decreased the incidences of the combined end point. LBBB and LAD were independently associated with the combined end point.

Left atrium in cardiac resynchronization therapy: Active participant or innocent bystander

Background

Cardiac resynchronization therapy (CRT) is an established treatment for patients with advanced heart failure that results in improvement of left ventricle (LV) systolic function and LV reverse remodeling. This may have a positive effect on the size and the function of the left atrium (LA). We assessed the LA function, dimensions, and volumes before and after CRT implantation.

Methods

A total of 37 patients with mean age of 55.3 ± 9.64 years including 11 (29.7%) females, having symptomatic heart failure [ejection fraction (EF) <35%, left bundle branch block >120 ms, with New York Heart Association III or ambulatory class IV] were enrolled, and underwent CRT implantation. M-mode, two-dimensional (2D) echocardiography, tissue Doppler imaging, and 2D strain (ɛ) imaging were done assessing LV volumes, ejection fraction, and diastolic function, LA diameter, area, maximal and minimal volumes, LA EF, and longitudinal strain (ɛ). Patients were reassessed after 3 months. A reduction in LV end-systolic volume of ≥10% was defined as volumetric responders to CRT. Patients with decompensated New York Heart Association class IV, sustained atrial arrhythmias, rheumatic or congenital heart diseases, nonleft bundle branch block, and those who were poorly echogenic, were excluded.

Results

Twenty-four (64.8%) patients were volumetric responders (group A). Both groups were matched regarding demographic, clinical, electrocardiographic, and echocardiographic criteria apart from the LA dimension and volumes which were significantly lower in the responders group prior to CRT. At the end of the follow-up, only the responders group had further significant reduction in LA diameter (41.6 ± 1.67 vs. 43.88 ± 1.82 mm, p < 0.01), maximal volume (62.2 ± 18.3 vs. 73.04 ± 21.78 ml, p < 0.01), minimal volume (32.6 ± 12.3 vs. 41.8 ± 13.97, p < 0.01), together with a significant increase in LA EF (48.3 ± 11.3 vs. 41.99 ± 13.9, p < 0.01), positive longitudinal strain (16.59% ± 5.89 vs. 12.45% ± 6.12, p < 0.01), and negative longitudinal strain (−3.3 ± 1.9 vs. −1.62 ± 1.2, p < 0.01) compared to baseline readings, a finding that was not present in the nonresponders group. In addition, atrial fibrillation was significantly higher in the nonresponders group. Baseline LA diameter and volumes were found to be independent predictors of response to CRT by multivariate analysis.

Conclusions

CRT induces LA anatomic, electrical, and structural reverse remodeling that could be assessed by conventional 2D echocardiography and 2D (ɛ) strain imaging. LA dimension and volumes were independent predictors of response to CRT and can help in selection of candidates for it.

Effect of QRS Narrowing After Cardiac Resynchronization Therapy on Functional Mitral Regurgitation in Patients With Systolic Heart Failure

The determinants of improvement in functional mitral regurgitation (FMR) after cardiac resynchronization therapy (CRT) remain unclear. We evaluated the predictors of FMR improvement and hypothesized that CRT-induced change in QRS duration (ΔQRS) might have an impact on FMR response after CRT. One hundred ten CRT recipients were enrolled. CRT response (≥ 15 reduction in left ventricular end-systolic volume) and FMR response (absolute reduction in FMR volume) were assessed with echocardiography before and 6 months after CRT. The study end points included all-cause death or hospitalization assessed in 12 ± 3 months (range 1 to 18). A total of 71 patients (65%) responded to CRT at 6 months. FMR response was observed in 49 (69%) of the CRT responders and 8 (20%) of the CRT nonresponders (p <0.001). Although the baseline QRS durations were similar, the paced QRS durations were shorter (p = 0.012) and the ΔQRS values were greater (p = 0.003) in FMR responders compared with FMR nonresponders. There was a linear correlation between ΔQRS and change in regurgitant volume (r = 0.49, p <0.001). At multivariate analysis, baseline tenting area (p = 0.012) and ΔQRS (p = 0.028) independently predicted FMR response. A ΔQRS ≥ 20 ms was related to CRT response, FMR improvement, and lower rates of death or hospitalization during follow-up (p values <0.05). In conclusion, QRS narrowing after CRT independently predicts FMR response. A ΔQRS ≥ 20 ms after CRT is associated with a favorable outcome in all clinical end points.

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.

Complete left bundle branch block and smaller left atrium are predictors of response to cardiac resynchronization therapy in advanced heart failure

BACKGROUND

We previously reported that cardiac resynchronization therapy with defibrillator (CRT-D) is not an appropriate rescue strategy in patients with advanced heart failure (HF), especially those dependent on inotrope infusion, and instead early ventricular assist device (VAD) implantation should be considered. Predictors of response to CRT in such populations, however, remain uncertain.

METHODS AND RESULTS

We studied 67 inpatients aged <65 years old with advanced HF, who received CRT-D between 2007 and 2014. Eleven patients (16%) were responders, in whom LVEF improved >10% at 6-month follow up. On logistic regression analysis, LA volume index (LAVI) <43 ml/m(2)(odds ratio (OR), 36.67; P=0.001) and complete left bundle branch block (CLBBB; OR, 6.663; P=0.032) were significant predictors of response to CRT-D among the baseline variables. Patients with both predictors were associated with improvements in LVEF and plasma B-type natriuretic peptide compared with those with none of these predictors during the 6-month follow up period (P<0.05 for both). VAD-free survival rate was significantly higher in the responders compared with the non-responders during the 2-year study period (86% vs. 52%, P=0.044).

CONCLUSIONS

CLBBB and smaller LAVI are novel predictors of response in patients with advanced HF receiving CRT-D in real-world practice. Such responders may be better candidates for CRT-D and delay of cardiac replacement 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.

Predictors for cardiac resynchronization therapy response: the importance of QRS morphology and left ventricular lead position

Although cardiac resynchronization therapy (CRT) is a well-established treatment for a subset of patients with chronic heart failure, a considerable proportion of eligible patients still fail to benefit from this treatment. The aim of this study was to identify potential independent predictors for being a responder to CRT. A single-center, retrospective analysis was conducted in 193 consecutive patients with heart failure and wide QRS complex who successfully underwent CRT device implantation from January 2006 to October 2012. Clinical characteristics, left ventricular lead position (LV-Ps), electrocardiography and echocardiography were evaluated before and 12 months after CRT. Response to CRT was defined as an absolute increase of ≥ 5% in left ventricular ejection fraction (LVEF) compared with baseline at 12 months after CRT implantation without heart failure rehospitalization or any cause of death. There were 132 responders (68%) and 61 nonresponders (32%). By univariate logistic analysis, the presence of non-left bundle branch block (non-LBBB) and QRS duration, chronic atrial fibrillation (AF), history of ventricular tachycardia (VT), degree of tricuspid regurgitation and left atrium dimension (LAD) at baseline, ΔQRS duration, and LV-Ps were associated with predicting a response to CRT. However, on multivariate analysis, only optimal LV-Ps and presence of non-LBBB remained independently predictive for a CRT response, with an odds ratio of 2.53 (95% confidence interval [CI]: 1.13-5.66, P = 0.023), 0.15(95% CI: 0.05-0.45, P = 0.001), respectively. Kaplan-Meier analysis revealed that patients with nonoptimal LV-Ps or non-LBBB morphology had a significantly higher rate of mortality or heart failure rehospitalization as compared with those with optimal LV-Ps or LBBB morphology (P < 0.05).

Predictors of positive response to cardiac resynchronization therapy

BACKGROUND

Approximately 30% of patients treated with cardiac resynchronization therapy (CRT) do not achieve favourable response. The purpose of the present study was to identify echocardiographic and clinical predictors of a positive response to CRT.

METHODS

The study included 82 consecutive heart failure (HF) patients in New York Heart Association (NYHA) functional class III or IV with left bundle branch block (LBBB), QRS duration ≥ 120 ms and left ventricular ejection fraction (LVEF) ≤ 35%. Statistical analysis was performed using IBM SPSS statistical software (SPSS v.21.0 for Mac OS X). A p value < 0.05 was considered statistically significant.

RESULTS

Echocardiographic response was established in 81.6% and clinical response was achieved in 82.9% of patients. Significant univariate predictors of favourable echocardiographic response after 12 months were smaller left ventricular end-diastolic diameter (LVEDD) (odds ratio [OR] 0.89; 95% confidence interval [CI] 0.82 - 0.97, p = 0.01), and smaller left ventricular end-systolic diameter (LVESD) (OR 0.91; 95% CI 0.85 - 0.98, p = 0.01). Lower uric acid concentration was associated with better echocardiographic response (OR 0.99; 95% CI 0.99 - 1.0, p = 0.01). Non-ischemic HF etiology (OR 4.89; 95% CI 1.39 - 17.15, p = 0.01) independently predicted positive clinical response. Multiple stepwise regression analysis demonstrated that LVEDD lower than 75 mm (OR 5.60; 95% confidence interval [CI] 1.36 - 18.61, p = 0.01) was the strongest independent predictor of favourable echocardiographic response.

CONCLUSIONS

Smaller left ventricular end-diastolic and end-systolic diameters and lower serum uric acid concentration were associated with better response to CRT. Left ventricular end-diastolic diameter and non-ischemic heart failure etiology were the strongest independent predictors of positive response to CRT.

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.

Long-term outcome of 'super-responder' patients to cardiac resynchronization therapy

AIMS

To evaluate the long-term changes of clinical and echocardiographic parameters, the incidence of cardiac events and parameters associated with late cardiac events in 'super-responders' to cardiac resynchronization therapy (CRT) with [CRT defibrillator (CRT-D)] or without defibrillator back-up.

METHODS AND RESULTS

In all consecutive patients treated with CRT in two Italian centres (Trieste and Udine) with left ventricular ejection fraction (LVEF) ≤0.35 at implantation (Timp) and LVEF > 0.50 1 and/or 2 years (Tnorm) after implantation, the long-term outcome and the evolution of echocardiographic parameters were assessed; factors associated with a higher risk of cardiac events, defined as hospitalization or death for heart failure (HF), sudden death, or CRT-D appropriate interventions, were also analysed. Among the 259 patients evaluated, 62 (24%) had LVEF ≥ 0.50 at Tnorm (n = 44 with at 1 year, n = 18 at 2 years). During a mean follow-up of 68 ± 30 months, one cardiac death (for HF) and eight cardiovascular events (two hospitalization for HF and six appropriate CRT-D interventions) occurred. At the last echo evaluation (Tfup) performed 51 ± 26 months after Timp, LVEF was <0.50 in five patients (>0.45 in four of them). At univariable analysis, only LV end-systolic volume evaluated at Tfup was associated with a higher risk of cardiac events during follow-up.

CONCLUSION

In 'super-responders' to CRT long-term outcome is excellent. However, cardiac events, mainly CRT-D appropriate interventions, can occur despite the persistence of LVEF > 0.50. Early identification of these patients is still an unsolved issue.