Electrical Remodeling and Cardiac Dimensions in Patients Treated by Cardiac Resynchronization and Heart Failure Controls

Evolution and prognosis of tricuspid and mitral regurgitation following cardiac implantable electronic devices: a systematic review and meta-analysis

AIMS

Significant changes in tricuspid regurgitation (TR) and mitral regurgitation (MR) post-cardiac implantable electronic devices (CIEDs) are increasingly recognized. However, uncertainty remains as to whether the risk of CIED-associated TR and MR differs with right ventricular pacing (RVP) via CIED with trans-tricuspid RV leads, compared with cardiac resynchronization therapy (CRT), conduction system pacing (CSP), and leadless pacing (LP). The study aims to synthesize extant data on risk and prognosis of significant post-CIED TR and MR across pacing strategies.

METHODS AND RESULTS

We searched PubMed, EMBASE, and Cochrane Library databases published until 31 October 2023. Significant post-CIED TR and MR were defined as ≥ moderate. Fifty-seven TR studies (n = 13 723 patients) and 90 MR studies (n = 14 387 patients) were included. For all CIED, the risk of post-CIED TR increased [pooled odds ratio (OR) = 2.46 and 95% CI = 1.88-3.22], while the risk of post-CIED MR reduced (OR = 0.74, 95% CI = 0.58-0.94) after 12 and 6 months of median follow-up, respectively. Right ventricular pacing via CIED with trans-tricuspid RV leads was associated with increased risk of post-CIED TR (OR = 4.54, 95% CI = 3.14-6.57) and post-CIED MR (OR = 2.24, 95% CI = 1.18-4.26). Binarily, CSP did not alter TR risk (OR = 0.37, 95% CI = 0.13-1.02), but significantly reduced MR (OR = 0.15, 95% CI = 0.03-0.62). Cardiac resynchronization therapy did not significantly change TR risk (OR = 1.09, 95% CI = 0.55-2.17), but significantly reduced MR with prevalence pre-CRT of 43%, decreasing post-CRT to 22% (OR = 0.49, 95% CI = 0.40-0.61). There was no significant association of LP with post-CIED TR (OR = 1.15, 95% CI = 0.83-1.59) or MR (OR = 1.31, 95% CI = 0.72-2.39). Cardiac implantable electronic device-associated TR was independently predictive of all-cause mortality [pooled hazard ratio (HR) = 1.64, 95% CI = 1.40-1.90] after median of 53 months. Mitral regurgitation persisting post-CRT independently predicted all-cause mortality (HR = 2.00, 95% CI = 1.57-2.55) after 38 months.

CONCLUSION

Our findings suggest that, when possible, adoption of pacing strategies that avoid isolated trans-tricuspid RV leads may be beneficial in preventing incident or deteriorating atrioventricular valvular regurgitation and might reduce mortality.

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.

Ratio of End-Systolic Volume to Left Atrial Area Is a Solid Benchmark of Systolic Dysfunction in Non-Ischemic Cardiomyopathies

Background

Impairment of systolic function and late gadolinium enhancement (LGE) are well-known negative prognostic markers in non-ischemic cardiomyopathies (NICMPs). There is limited knowledge of the geometrical rearrangements of the ventricle volumes over size of the left atrium and their connections with systolic dysfunction and existence of LGE.

Material/Methods

Consecutive cases of NICMPs with impaired systolic function and controls were included from a computerized database of cardiac magnetic resonance exams for a 2.5-year period. Ratios made from volumetric parameters over left atrial area (LAA) area were calculated.

Results

Our study included 205 cases referred to cardiac magnetic resonance (CMR); age was 48.7±17.0 years (range 15.2–80.4), male-to-female ratio 137 (66.8%): 68 (33.2%), (both p>0.05). LGE was significantly correlated with impairment of systolic function (Rho CC=0.395; p<0.001). For detection of systolic impairment, a critical value of end-systolic-volume (ESV)/LAA of ≥2.7 had an area under curve (AUC) of 0.902 (0.853–0.939), p<0.001; stroke-volume (SV)/LAA ≤3.0 had AUC=0.782(0.719–0.837), p<0.001, and end-diastolic volume (EDV)/LAA <7.4 had an AUC of 0.671 (0.602–0.735); p<0.001. In analyses of LGE, a value of SV/LAA of ≤3.0 had an AUC of 0.681 (0.612–0.744), p<0.001; while ESV/LAA and EDV/LAA were not significant (both p<0.05). ESV/LAA was correlated with systolic dysfunction (Rho-correlation-coefficient: 0.688; p<0.001) and existence of linear midventricular LGE stripe (Rho-CC=0.446; p<0.001).

Conclusions

ESV/LAA was the most effective for detection of systolic impairment and was associated with the existence of LGE. Prospective validation for clinical applicability and prognostic relations are warranted in future studies.

Prediction of Both Electrical and Mechanical Reverse Remodeling on Acute Electrocardiogram Changes After Cardiac Resynchronization Therapy

BACKGROUND

The development of both electrical reverse remodeling and mechanical reverse remodeling (ERR+MRR) after cardiac resynchronization therapy (CRT) implantation could reduce the incidence of lethal arrhythmia, hence the prediction of ERR+MRR is clinically important.Methods and Results:Eighty-three patients (54 male; 67±12 years old) with CRT >6 months were enrolled. ERR was defined as baseline intrinsic QRS duration (iQRSd) shortening ≥10 ms in lead II on ECG after CRT, and MRR as improvement in LVEF ≥25% on echocardiography after CRT. Acute ECG changes were measured by comparing the pre-implant and immediate post-implant ECG. Ventricular arrhythmia episodes, including ventricular tachycardia and ventricular fibrillation, detected by the implanted device were recorded. Patients were classified as ERR only (n=12), MRR only (n=23), ERR+MRR (n=26), or non-responder (ERR- & MRR-, n=22). On multivariate regression analysis, difference between baseline intrinsic QRS and paced QRS duration (∆QRSd) >35 ms was a significant predictor of ERR+MRR (sensitivity, 68%; specificity, 64%; AUC, 0.7; P=0.003), and paced QTc >443 ms was a negative predictor of ERR+MRR (sensitivity, 78%; specificity, 60%; AUC, 0.7; P=0.002). On Cox proportional hazard modeling, ERR+MRR may reduce risk of ventricular arrhythma around 70% compared with non-responder (HR, 0.29; 95% CI: 0.13-0.65).

CONCLUSIONS

Acute ECG changes after CRT were useful predictors of ERR+MRR. ERR+MRR was also a protective factor for ventricular arrhythmia.

Improvement in left ventricular intrinsic dyssynchrony with cardiac resynchronization therapy

Objective:

Cardiac resynchronization therapy (CRT) has been shown to induce a structural and electrical remodeling; the data on whether left ventricle (LV) reverse remodeling is associated with restitution of intrinsic contraction pattern are unknown. In this study, we investigated the presence of improvement in left ventricular intrinsic dyssynchrony in patients with CRT.

Methods:

A total of 45 CRT recipients were prospectively studied. Dyssynchrony indexes including interventricular mechanical delay (IVMD) and tissue Doppler velocity opposing-wall delay (OWD) as well as QRS duration on 12-lead surface electrocardiogram were recorded before CRT device implantation. After 1 year, patients with chronic biventricular pacing were reprogramed to VVI 40 to allow the resumption of native conduction and contraction pattern. After 4–6 h of intrinsic rhythm, QRS duration and all echocardiographic measurements were recorded. Dyssynchrony was defined as IVMD >40 ms and OWD >65 ms. CRT response was defined by a ≥15% reduction in left ventricular end-systolic volume (LVESV) at a 12-month follow-up.

Results:

Thirty-two patients (71%) showed response to CRT. The native QRS duration reduced significantly from 150±12 ms to 138±14 ms (p<0.001), and dyssynchrony indexes showed a significant improvement only in responders. The mean OWD reduced from 86±37 ms to 50±29 ms (p<0.001), and the mean IVMD decreased from 55±22 ms to 28±22 ms (p<0.001) in responders. The reduction in LVESV was significantly correlated with ΔOWD (r=0.47, p=0.001), ΔIVMD (r=0.45, p=0.001), and ΔQRS (r=0.34, p=0.022).

Conclusion:

Chronic CRT significantly improves LV native contraction pattern and causes reverse remodeling in dyssynchrony.

Effect of Cardiac Resynchronisation Therapy on Electrical Remodelling

BACKGROUND

Cardiac resynchronisation therapy (CRT) is an accepted device therapy in patients with low ejection fraction. Beneficial effects of CRT result from mechanical remodelling. Some controversial reports suggest that CRT may also induce electrical remodelling with intrinsic QRS narrowing but still the effect of CRT on electrical remodelling is an issue for debate. The aim of our study was to evaluate the effects of CRT on intrinsic QRS duration. For clarity, our analysis was performed by the signal averaged electrocardiogram (SAECG) which is a high resolution electrocardiographic signal suitable for accurate measurement of QRS duration. Signal averaged electrocardiogram provides a better value of QRS duration compared to 12-lead ECG by the ability to detect ventricular late potentials.

METHODS

A total of 48 consecutive patients with severe systolic dysfunction and typical left bundle branch block (LBBB) were enrolled in the study prospectively. Patients were scheduled for CRT-D implantation according to the current guidelines. Intrinsic QRS duration was accurately measured by SAECG before and at least 14 months after CRT implantation.

RESULTS

The mean intrinsic QRS duration remained unchanged during follow-up (from 149.9±13.8ms to 149.6±18.4ms; P= 0.3). Among 32 CRT responder patients, the mean intrinsic QRS duration remained unchanged during follow-up. Also, the mean intrinsic QRS duration showed no significant changes in 16 CRT non-responders.

CONCLUSION

Structural remodelling induced by CRT does not necessarily translate into decrease of intrinsic ventricular activation. Despite significant left ventricular recovery, electrical characteristics of the left ventricular conduction system cannot generally be expected to recuperate.

Effects of Cardiac Resynchronization Therapy on Ventricular Electrical Remodeling in Patients With Heart Failure

Cardiac resynchronization therapy (CRT) reverses structural remodeling of the left ventricle. We investigated whether CRT reverses left-ventricular electrical remodeling.Eighty patients were enrolled and implanted with CRT-devices. Echocardiography and electrocardiography data were obtained from each patient prior to implantation and two years after implantation. At two years after implantation, the patients were classified into a responder group and a non-responder group based on echocardiography.Over the next 2 years, 75 patients completed follow-up, and 5 patients had died. Echocardiography results showed that 23 patients could be classified as non-responders and 52 as responders. Larger numbers of non-responders were diagnosed with either ischemic cardiomyopathy (ICM) or nonspecific intraventricular conduction delay (NICD). The intrinsic QRS duration was not changed in responders, patients with dilated cardiomyopathy, or in the patient categories of male and female. However, the intrinsic QRS duration was significantly prolonged in non-responders and patients with ischemic cardiomyopathy (P = 0.041). The mean left ventricular end-diastolic diameter in the responder group was significantly decreased by CRT (P < 0.05), while there was no significant change in intrinsic QRS duration.While CRT does not reduce the intrinsic QRS duration, it can delay negative ventricular electrical remodeling. Continuous CRT is necessary.

Correlation of electrical and mechanical reverse remodeling after cardiac resynchronization therapy

BACKGROUND

Cardiac resynchronization therapy (CRT) improves clinical outcome in many patients with refractory heart failure (HF). This study examined whether CRT is associated with reverse electrical remodeling by surface electrocardiogram (ECG).

METHODS

Consecutive CRT recipients at the University of Pittsburgh Medical Center with >90 days of follow-up were included in this analysis. ECG data were abstracted from medical records. Subjects with a relative increase of > or =15% in left ventricular ejection fraction (LVEF) after CRT were considered responders.

RESULTS

A total of 113 patients (age 69 +/- 11 years, men 70%, white 92%) were followed for a mean duration of 407 +/- 290 (92-1439) days. Overall, LVEF increased after CRT (29 +/- 13% vs 24 +/- 9%; P < 0.01) and 50% of patients were responders. The mean native QRS interval among responders was higher than in nonresponders (163 +/- 32 ms vs 148 +/- 29 ms; P < 0.01). More than 3 months after CRT, there was no change in the paced QRS duration compared to baseline. Paced QRS duration, however, decreased among responders and increased among nonresponders and was significantly different by response status (P < 0.001). There was a significant correlation between increase in LVEF and decrease in paced QRS width in the overall population (r =-0.3; P < 0.01).

CONCLUSIONS

Among responders to CRT, the paced QRS width decreases significantly, whereas it increases among nonresponders. Given the paced nature of the QRS, the improved conduction probably reflects enhanced cell-to-cell coupling after CRT as opposed to improved conduction within the His-Purkinje system. These findings have significant implications as to the mechanisms of benefit from CRT.