Correlation of electrical and mechanical reverse remodeling after cardiac resynchronization therapy

Changes in cardiac conduction time following cardiac resynchronization therapy: rationale and design of the RECOVER study

BACKGROUND

It has been known that ventricular conduction delays play a key role in the cardiac resynchronization therapy (CRT) response of patients with advanced heart failure (HF). However, no study to our knowledge has yet evaluated the serial changes in conduction times measured between different electrodes of CRT devices.

METHODS AND RESULTS

The Reduction or Extension of Conduction Time with Ventricular Electromechanical Remodeling (RECOVER) study (NCT04397224) was designed to investigate serial changes in interelectrode conduction times and to elucidate their prognostic value. We plan to enroll 100 patients implanted with CRT systems with endocardial quadripolar left ventricular leads. Patients will be scheduled for follow-up every 3 months over a period of 2 years, where they will undergo measurement of interelectrode conduction times to evaluate their serial changes. The primary outcome of the RECOVER study is the correlation between the degree of conduction time changes and the CRT response as defined by echocardiography. The time course and prognostic value of the serial changes in conduction times will be investigated as well.

CONCLUSION

The RECOVER study is investigating whether serial changes in interelectrode conduction times can be useful parameters in predicting the CRT response or detecting worsening HF at an early stage.

Differential effect of cardiac resynchronization therapy in patients with diabetes mellitus: a long-term retrospective cohort study

AIMS

Cardiac resynchronization therapy (CRT) has become an important therapy in patients with heart failure with reduced left ventricular ejection fraction (LVEF). The effect of diabetes on long-term outcome in these patients is controversial. We assessed the effect of diabetes on long-term outcome in CRT patients and investigated the role of diabetes in ischaemic and non-ischaemic cardiomyopathy.

METHODS AND RESULTS

All patients undergoing CRT implantation at our institution between November 2000 and January 2015 were enrolled. The study endpoints were (i) a composite of ventricular assist device (VAD) implantation, heart transplantation, or all-cause mortality; and (ii) reverse remodelling (improvement of LVEF ≥ 10% or reduction of left ventricular end-systolic volume ≥ 15%). Median follow-up of the 418 patients (age 64.6 ± 11.6 years, 22.5% female, 25.1% diabetes) was 4.8 years [inter-quartile range: 2.8;7.4]. Diabetic patients had an increased risk to reach the composite endpoint [adjusted hazard ratio (aHR) 1.48 [95% CI 1.12-2.16], P = 0.041]. Other factors associated with an increased risk to reach the composite endpoint were a lower body mass index or baseline LVEF (aHR 0.95 [0.91; 0.98] and 0.97 [0.95; 0.99], P < 0.01 each), and a higher New York Heart Association functional class or creatinine level (aHR 2.14 [1.38; 3.30] and 1.04 [1.01; 1.05], P < 0.05 each). Early response to CRT, defined as LVEF improvement ≥ 10%, was associated with a lower risk to reach the composite endpoint (aHR 0.60 [0.40; 0.89], P = 0.011). Reverse remodelling did not differ between diabetic and non-diabetic patients with respect to LVEF improvement ≥ 10% (aHR 0.60 [0.32; 1.14], P = 0.118). However, diabetes was associated with decreased reverse remodelling with respect to a reduction of left ventricular end-systolic volume ≥ 15% (aHR 0.45 [0.21; 0.97], P = 0.043). In patients with ischaemic cardiomyopathy, survival rates were not significantly different between diabetic and non-diabetic patients (HR 1.28 [0.83-1.97], P = 0.101), whereas in patients with non-ischaemic cardiomyopathy, diabetic patients had a higher risk of reaching the composite endpoint (HR 1.65 [1.06-2.58], P = 0.027). The latter effect was dependent on other risk factors (aHR 1.47 [0.83-2.61], P = 0.451). The risk of insulin-dependent patients was not significantly higher than in patients under oral antidiabetic drugs (HR 1.55 [95% CI 0.92-2.61], P = 0.102).

CONCLUSIONS

Long-term follow-up revealed diabetes mellitus as independent risk factor for all-cause mortality, heart transplantation, or VAD in heart failure patients undergoing CRT. The detrimental effect of diabetes appeared to weigh heavier in patients with non-ischaemic compared with ischaemic cardiomyopathy.

Electrical Reverse Remodeling of the Native Cardiac Conduction System after Cardiac Resynchronization Therapy

Background: Little is known about electrical remodeling of the native conduction systems, particularly how the PR interval changes, after cardiac resynchronization therapy (CRT). We investigated the effects of CRT on the intrinsic PR interval (i-PRi) and QRS duration (i-QRSd). Methods and results: In 100 consecutive CRT recipients with sinus rhythm and long-term follow-up (>1 year), the i-PRi and i-QRSd were measured at baseline and at the last echocardiographic follow-up (33.4 ± 17.9 months) with biventricular pacing temporarily withdrawn. The relative decrease in the left ventricular end-systolic volume (LVESV) was measured to define CRT-responders (≥15%) and super-responders (≥30%). Following CRT, the left ventricular (LV) ejection fraction increased significantly (p < 0.001). In CRT-responders (n = 71), the LVESV and i-QRSd decreased markedly (170 ± 39 to 159 ± 24 ms, p = 0.012). However, the i-PRi was not shortened with CRT response and was actually likely to increase, even in the super-responder group (n = 33). Moreover, lengthening of the i-PRi was observed consistently irrespective of the CRT response status, beta-blocker use, or amiodarone use. CRT non-responders were associated with a remarkable PR prolongation (p = 0.005) and QRS widening (p = 0.001), along with positive ventricular remodeling. Conclusion: LV volume and i-QRSd decreased markedly with CRT response. However, the i-PRi was not shortened, but rather increased regardless of the degree of CRT response. CRT non-response was associated with a considerable increase in the i-PRi and i-QRSd, along with positive ventricular remodeling. CRT-induced electrical reverse remodeling might occur preferentially in the intraventricular, but not the atrioventricular, conduction system.

Association between changes in QRS width and echocardiographic responses to cardiac resynchronization therapy: A systematic review and meta-analysis

BACKGROUND

Numerous studies have illustrated the association of QRS width with the incidence of echocardiographic response to cardiac resynchronization therapy (CRT). This study aimed to summarize the observational studies regarding the magnitude of change in QRS width between responders and nonresponders to CRT.

METHODS

The PubMed, Embase, and the Cochrane Library were systematically searched for relevant studies investigating the changes of QRS width with the incidence of echocardiographic response to CRT from inception till May 2019. The pooled weighted mean difference (WMD) with 95% confidence interval (CI) was calculated through random-effects model.

RESULTS

Five prospective and 6 retrospective studies with a total of 1524 patients were selected for final analysis. The reduction of QRS width in responders was significantly greater than nonresponders (WMD: -20.54 ms; 95% CI: -26.78 to -14.29; P < .001). Moreover, responders were associated with greater percentage reduction in QRS width when compared with nonresponders (WMD: -8.80%; 95% CI: -13.08 to -4.52; P < .001). Finally, the mean change in QRS width between responders and nonresponders differed when stratified by country, study design, mean age, percentage male, ejection fraction, measuring time of postimplanted QRS, ischemic cardiomyopathy, atrial fibrillation, and study quality.

CONCLUSIONS

These findings indicated that shortening QRS width after CRT device implantation showed association with greater incidence of echocardiographic responses to CRT. Further prospective studies should be conducted to evaluate the prognostic values of QRS width on the incidence of echocardiographic response to CRT.

miR-133: A Suppressor of Cardiac Remodeling?

Cardiac remodeling, which is characterized by mechanical and electrical remodeling, is a significant pathophysiological process involved in almost all forms of heart diseases. MicroRNAs (miRNAs) are a group of non-coding RNAs of 20–25 nucleotides in length that primarily regulate gene expression by promoting mRNA degradation or post-transcriptional repression in a sequence-specific manner. Three miR-133 genes have been identified in the human genome, miR-133a-1, miR-133a-2, and miR-133b, which are located on chromosomes 18, 20, and 6, respectively. These miRNAs are mainly expressed in muscle tissues and appear to repress the expression of non-muscle genes. Based on accumulating evidence, miR-133 participates in the proliferation, differentiation, survival, hypertrophic growth, and electrical conduction of cardiac cells, which are essential for cardiac fibrosis, cardiac hypertrophy, and arrhythmia. Nevertheless, the roles of miR-133 in cardiac remodeling are ambiguous, and the mechanisms are also sophisticated, involving many target genes and signaling pathways, such as RhoA, MAPK, TGFβ/Smad, and PI3K/Akt. Therefore, in this review, we summarize the critical roles of miR-133 and its potential mechanisms in cardiac remodeling.

Meta-Analysis of the Usefulness of Change in QRS Width to Predict Response to Cardiac Resynchronization Therapy

The existing data regarding the role of QRS duration (QRSd) change on cardiac resynchronization therapy (CRT) response show some inconsistent results. We conducted a meta-analysis of data obtained from observational studies to examine the impact of QRS change after CRT device implantation on the clinical and/or echocardiographic response. We searched the PubMed and EMBASE databases for relevant studies published before January 2016. Twenty-seven studies were retrieved for detailed evaluation of which 12 studies with a total population of 1,545 patients met our eligibility criteria. The analysis demonstrated that QRSd narrowing was a positive predictor of response to CRT (mean difference [MD] = -19.24 ms, 95% CI = -24.00 to -14.48 ms, p <0.00001). This effect was consistent in the studies using clinical criteria (MD = -19.91 ms, 95% CI = -27.20 to -12.62 ms, p <0.00001) and in those that used echocardiographic criteria (MD = -19.51 ms, 95% CI = -25.78 to -13.25 ms, p <0.00001). The heterogeneity test showed moderate differences among the individual studies (I² = 42%). Subgroup analysis showed that QRSd change was more pronounced in studies having a follow-up ≤6 months. We did not find significant differences in studies measuring postimplantation QRSd after a certain follow-up period compared with studies measuring QRSd immediately after CRT device implantation. Further studies should clarify the exact timing of QRSd assessments during follow-up. In conclusion, QRSd shortening after CRT device implantation is associated with a favorable clinical and echocardiographic response.

Association between QRS duration and outcome with cardiac resynchronization therapy: a systematic review and meta-analysis

PURPOSE

We conducted a systematic review and meta-analysis of randomized and observational studies to evaluate the associations between QRS duration (QRSd) at baseline or in follow-up and outcomes with cardiac resynchronization therapy (CRT).

METHODS

We searched online databases to December 2010 and included 6 randomized controlled trials (RCTs) and 38 observational studies. Outcomes included clinical/functional response, left ventricular (LV) remodeling, hospitalizations and mortality.

RESULTS

In RCTs, a benefit of CRT was evident only in patients with QRSd >150ms. In observational studies, those meeting either clinical or remodeling CRT response definitions had both wider pooled baseline QRSd and significantly more QRS narrowing with CRT than non-responders.

CONCLUSIONS

RCTs demonstrate that benefit with CRT appears restricted to those with baseline QRSd wider than 150ms. Both wider baseline QRS and more QRS narrowing are associated with CRT response in observational studies. Electrocardiographic QRSd plays an important role in CRT patient selection and follow-up.

Effects of the purkinje system and cardiac geometry on biventricular pacing: a model study

Heart failure leads to gross cardiac structural changes. While cardiac resynchronization therapy (CRT) is a recognized treatment for restoring synchronous activation, it is not clear how changes in cardiac shape and size affect the electrical pacing therapy. This study used a human heart computer model which incorporated anatomical structures such as myofiber orientation and a Purkinje system (PS) to study how pacing affected failing hearts. The PS was modeled as a tree structure that reproduced its retrograde activation feature. In addition to a normal geometry, two cardiomyopathies were modeled: dilatation and hypertrophy. A biventricular pacing protocol was tested in the context of atrio-ventricular block. The contribution of the PS was examined by removing it, as well as by increasing endocardial conductivity. Results showed that retrograde conduction into the PS was a determining factor for achieving intraventricular synchrony. Omission of the PS led to an overestimate of the degree of electrical dyssynchrony while assessing CRT. The activation patterns for the three geometries showed local changes in the order of activation of the lateral wall in response to the same pacing strategy. These factors should be carefully considered when determining lead placement and optimizing device parameters in clinical practice.