Cardiac contractility modulation attenuates structural and electrical remodeling in a chronic heart failure rabbit model

Cardiac contractility modulation: A new horizon in the management of heart failure with preserved ejection fraction (HFpEF)

Cardiac contractility modulation (CCM) is a new therapy that has shown promising results in heart failure with preserved ejection fraction (HFpEF) management. This therapy involves the use of a device that delivers electrical signals to the heart during the refractory period, enhancing cardiac contractility without changing heart rate or rhythm. This short article explores the potential of CCM as a new horizon in the management of HFpEF, highlighting its mechanism of action, clinical trials, and future directions for research. Overall, CCM has emerged as a promising therapy for improving the outcomes of patients with HFpEF and provides hope for the development of more effective treatments in the future.

Ion channel trafficking implications in heart failure

Heart failure (HF) is recognized as an epidemic in the contemporary world, impacting around 1%-2% of the adult population and affecting around 6 million Americans. HF remains a major cause of mortality, morbidity, and poor quality of life. Several therapies are used to treat HF and improve the survival of patients; however, despite these substantial improvements in treating HF, the incidence of HF is increasing rapidly, posing a significant burden to human health. The total cost of care for HF is USD 69.8 billion in 2023, warranting a better understanding of the mechanisms involved in HF. Among the most serious manifestations associated with HF is arrhythmia due to the electrophysiological changes within the cardiomyocyte. Among these electrophysiological changes, disruptions in sodium and potassium currents' function and trafficking, as well as calcium handling, all of which impact arrhythmia in HF. The mechanisms responsible for the trafficking, anchoring, organization, and recycling of ion channels at the plasma membrane seem to be significant contributors to ion channels dysfunction in HF. Variants, microtubule alterations, or disturbances of anchoring proteins lead to ion channel trafficking defects and the alteration of the cardiomyocyte's electrophysiology. Understanding the mechanisms of ion channels trafficking could provide new therapeutic approaches for the treatment of HF. This review provides an overview of the recent advances in ion channel trafficking in HF.

Enhancing myocardial function with cardiac contractility modulation: potential and challenges

Cardiac contractility modulation (CCM) offers a novel therapeutic avenue for heart failure patients, particularly those unresponsive to cardiac resynchronization therapy within specific QRS duration ranges. This review elucidates CCM's mechanistic underpinnings, its impact on myocardial function, and utility across patient demographics. However, CCM is limited by insufficient data on mortality and hospitalization rate reductions, as well as the need for specialized device implantation skills. While prevailing research has concentrated on left ventricular effects, a knowledge gap persists for other patient subsets. Future inquiries should address combinatory treatment strategies, extended usage and the impact of atrial fibrillation on device implantation. Such expanded studies could refine therapeutic outcomes and widen the scope of beneficiaries.

Basic science of cardiac contractility modulation therapy: Molecular and electrophysiological mechanisms

In heart failure with reduced ejection fraction and heart failure with preserved ejection fraction, profound cellular and molecular changes have recently been documented in the failing myocardium. These changes include altered calcium handling and metabolic efficiency of the cardiac myocyte, reactivation of the fetal gene program, changes in the electrophysiological properties of the heart, and accumulation of collagen (fibrosis) at the interstitial level. Cardiac contractility modulation therapy is an innovative device-based therapy currently approved for heart failure with reduced ejection fraction in patients with narrow QRS complex and under investigation for the treatment of heart failure with preserved ejection fraction. This therapy is based on the delivery of high-voltage biphasic electrical signals to the septal wall of the right ventricle during the absolute refractory period of the myocardium. At the cellular level, in patients with heart failure with reduced ejection fraction, cardiac contractility modulation therapy has been shown to restore calcium handling and improve the metabolic status of cardiac myocytes, reverse the heart failure-associated fetal gene program, and reduce the extent of interstitial fibrosis. This review summarizes the preclinical literature on the use of cardiac contractility modulation therapy in heart failure with reduced and preserved ejection fraction, correlating the molecular and electrophysiological effects with the clinical benefits demonstrated by this therapy.

Large animal models to study effectiveness of therapy devices in the treatment of heart failure with preserved ejection fraction (HFpEF)

Our understanding of the complex pathophysiology of Heart failure with preserved ejection fraction (HFpEF) is limited by the lack of a robust in vivo model. Existing in-vivo models attempt to reproduce the four main phenotypes of HFpEF; ageing, obesity, diabetes mellitus and hypertension. To date, there is no in vivo model that represents all the haemodynamic characteristics of HFpEF, and only a few have proven to be reliable for the preclinical evaluation of potentially new therapeutic targets. HFpEF accounts for 50% of all the heart failure cases and its incidence is on the rise, posing a huge economic burden on the health system. Patients with HFpEF have limited therapeutic options available. The inadequate effectiveness of current pharmaceutical therapeutics for HFpEF has prompted the development of device-based treatments that target the hemodynamic changes to reduce the symptoms of HFpEF. However, despite the potential of device-based solutions to treat HFpEF, most of these therapies are still in the developmental stage and a relevant HFpEF in vivo model will surely expedite their development process. This review article outlines the major limitations of the current large in-vivo models in use while discussing how these designs have helped in the development of therapy devices for the treatment of HFpEF.

Desmosomal Junctions and Connexin-43 Remodeling in High-Pacing-Induced Heart Failure Dogs

BACKGROUND

While desmosomal junctions and gap junction remodeling are among the arrhythmogenic substrates, the fate of desmosomal and gap junctions in high-pacing-induced heart failure remains unclear. This aim of this study was to determine the fate of desmosomal junctions in high-pacing-induced heart failure.

METHODS

Dogs were randomly divided into 2 equal groups, a high-pacing-induced heart failure model group (heart failure group, n = 6) and a sham operation group (control group, n = 6). Echocardiography and cardiac electrophysiological examination were performed. Cardiac tissue was analyzed by immunofluorescence and transmission electron microscopy. The expression of desmoplakin and desmoglein-2 proteins was detected by western blot.

RESULTS

A significant decrease in ejection fraction, significant cardiac dilatation, diastolic and systolic dysfunction, and ventricular thinning occurred after 4 weeks in high-pacing-induced dog model of heart failure. Effective refractory period action potential duration at 90% repolarization was prolonged in the heart failure group. Immunofluorescence analysis and transmission electron microscopy demonstrated connexin-43 lateralization accompanies desmoglein-2 and desmoplakin remodeling in the heart failure group. Western blotting showed that the expression of desmoplakin and desmoglein-2 proteins was higher in heart failure than in normal tissue.

CONCLUSION

Desmosome (desmoglein-2 and desmoplakin) redistribution and desmosome (desmoglein-2) overexpression accompanying connexin-43 lateralization were parts of a complex remodeling in high-pacing-induced heart failure.

The Effects of Device-Based Cardiac Contractility Modulation Therapy on Left Ventricle Global Longitudinal Strain and Myocardial Mechano-Energetic Efficiency in Patients with Heart Failure with Reduced Ejection Fraction

BACKGROUND

Virtually all patients with heart failure with reduced ejection fraction have a reduction of myocardial mechano-energetic efficiency (MEE). Cardiac contractility modulation (CCM) is a novel therapy for the treatment of patients with HFrEF, in whom it improves the quality of life and functional capacity, reduces hospitalizations, and induces biventricular reverse remodeling. However, the effects of CCM on MEE and global longitudinal strain (GLS) are still unknown; therefore, this study aims to evaluate whether CCM therapy can improve the MEE of patients with HFrEF.

METHODS

We enrolled 25 patients with HFrEF who received an Optimizer Smart implant (the device that develops CCM therapy) between January 2018 and January 2021. Clinical and echocardiographic evaluations were performed in all patients 24 h before and six months after CCM therapy.

RESULTS

At six months, follow-up patients who underwent CCM therapy showed an increase of left ventricular ejection fraction (30.8 ± 7.1 vs. 36.1 ± 6.9%; p = 0.032) as well a rise of GLS 10.3 ± 2.7 vs. -12.9 ± 4.2; p = 0.018), of MEE (32.2 ± 10.1 vs. 38.6 ± 7.6 mL/s; p = 0.013) and of MEE index (18.4 ± 6.3 vs. 24.3 ± 6.7 mL/s/g; p = 0.022).

CONCLUSIONS

CCM therapy increased left ventricular performance, improving left ventricular ejection fraction, GLS, as well as MEE and MEEi.

Myostatin deficiency decreases cardiac extracellular matrix in pigs

Myostatin (MSTN), a member of the TGF-β superfamily, negatively regulates muscle growth. MSTN inhibition has been known to cause a double-muscled phenotype in skeletal muscle and fibrosis reduction in the heart. However, the role of MSTN in the cardiac extracellular matrix (ECM) needs more studies in various species of animal models to draw more objective conclusions. The main objective of the present study was to investigate whether loss of MSTN affects the cardiac extracellular matrix in pigs. Three MSTN knockouts (MSTN-/-) and three wild type (WT) male pigs were generated by crossing MSTN ± heterozygous gilts and boars. Cardiac ECM and underlying mechanisms were determined post-mortem. The role of MSTN on collagen expression was investigated by treating cardiac fibroblasts with active MSTN protein in vitro. MSTN protein was detected in WT hearts, while no expression was detected in MSTN-/- hearts. The heart-to-body weight ratio was significantly decreased in MSTN-/- pigs. The morphometric analyses, including picrosirius red staining, immunofluorescent staining, and ultra-structural thickness examination of the endomysium, revealed a significant reduction of connective tissue content in MSTN-/- hearts compared to WT. Hydroxyproline, type I collagen (Col1A), and p-Smad3/Smad3 levels were significantly lower in MSTN-/- hearts in vivo. On the contrary, cardiac fibroblasts treated with exogenous MSTN protein overexpressed Col1A and activated Smad and AKT signaling pathways in vitro. The present study suggests that inhibition of MSTN decreases cardiac extracellular matrix.

Indoxyl sulfate reduces Ito,f by activating ROS/MAPK and NF-κB signaling pathways

There is a high prevalence of ventricular arrhythmias related to sudden cardiac death in patients with chronic kidney disease (CKD). To explored the possible mechanism of CKD-related ventricular arrhythmias, a CKD rat model was created, and indoxyl sulfate (IS) was further used in vivo and in vitro. This project used the following methods: patch clamp, electrocardiogram, and some molecular biology experimental techniques. IS was found to be significantly elevated in the serum of CKD rats. Interestingly, the expression levels of the fast transient outward potassium current-related (Ito,f-related) proteins (Kv4.2, Kv4.3, and KChIP2) in the heart of CKD rats and rats treated with IS decreased. IS dose-dependently reduced Ito,f density, accompanied by the decreases in Kv4.2, Kv4.3, and KChIP2 proteins in vitro. IS also prolonged the action potential duration and QT interval, and paroxysmal ventricular tachycardia could be induced by IS. In-depth studies have shown that ROS/p38MAPK, ROS-p44/42 MAPK, and NF-κB signaling pathways play key roles in the reduction of Ito,f density and Ito,f-related proteins caused by IS. These data suggest that IS reduces Ito,f-related proteins and Ito,f density by activating ROS/MAPK and NF-κB signaling pathways, and the action potential duration and QT interval are subsequently prolonged, which contributes to increasing the susceptibility to arrhythmia in CKD.

Emerging Implantable Device Technology for Patients at the Intersection of Electrophysiology and Heart Failure Interdisciplinary Care

Cardiac implantable electronic devices (CIEDs), including implantable cardioverter-defibrillators (ICDs) and cardiac resynchronization therapy (CRT), are part of guideline- indicated treatment for a subset of patients with heart failure with reduced ejection fraction (HFrEF). Current technological advancements in CIEDs have allowed the detection of specific patient physiologic parameters used for forecasting clinical decompensation through algorithmic, multiparameter remote monitoring. Other recent emerging technologies, including cardiac contractility modulation (CCM) and baroreflex activation therapy (BAT), may provide symptomatic or physiologic benefit in patients without an indication for CRT. Our goal in this state-of-the-art review is to describe the commercially available new technologies, purported mechanisms of action, evidence surrounding their clinical role, limitations, and future directions. Finally, we underline the need for standardized workflow and close interdisciplinary management of this population to ensure the delivery of high-quality care.

Acute effects of cardiac contractility modulation on human induced pluripotent stem cell-derived cardiomyocytes

Cardiac contractility modulation (CCM) is an intracardiac therapy whereby nonexcitatory electrical simulations are delivered during the absolute refractory period of the cardiac cycle. We previously evaluated the effects of CCM in isolated adult rabbit ventricular cardiomyocytes and found a transient increase in calcium and contractility. In the present study, we sought to extend these results to human cardiomyocytes using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to develop a robust model to evaluate CCM in vitro. HiPSC-CMs (iCell Cardiomyocytes2 , Fujifilm Cellular Dynamic, Inc.) were studied in monolayer format plated on flexible substrate. Contractility, calcium handling, and electrophysiology were evaluated by fluorescence- and video-based analysis (CellOPTIQ, Clyde Biosciences). CCM pulses were applied using an A-M Systems 4100 pulse generator. Robust hiPSC-CMs response was observed at 14 V/cm (64 mA) for pacing and 28 V/cm (128 mA, phase amplitude) for CCM. Under these conditions, hiPSC-CMs displayed enhanced contractile properties including increased contraction amplitude and faster contraction kinetics. Likewise, calcium transient amplitude increased, and calcium kinetics were faster. Furthermore, electrophysiological properties were altered resulting in shortened action potential duration (APD). The observed effects subsided when the CCM stimulation was stopped. CCM-induced increase in hiPSC-CMs contractility was significantly more pronounced when extracellular calcium concentration was lowered from 2 mM to 0.5 mM. This study provides a comprehensive characterization of CCM effects on hiPSC-CMs. These data represent the first study of CCM in hiPSC-CMs and provide an in vitro model to assess physiologically relevant mechanisms and evaluate safety and effectiveness of future cardiac electrophysiology medical devices.

Renal denervation prevents myocardial structural remodeling and arrhythmogenicity in a chronic kidney disease rabbit model

BACKGROUND

The electrophysiological (EP) effects and safety of renal artery denervation (RDN) in chronic kidney disease (CKD) are unclear.

OBJECTIVE

The purpose of this study was to investigate the arrhythmogenicity of RDN in a rabbit model of CKD.

METHODS

Eighteen New Zealand white rabbits were randomized to control (n = 6), CKD (n = 6), and CKD-RDN (n = 6) groups. A 5/6 nephrectomy was selected for the CKD model. RDN was applied in the CKD-RDN group. All rabbits underwent cardiac EP studies for evaluation. Immunohistochemistry, myocardial fibrosis, and renal catecholamine levels were evaluated.

RESULTS

The CKD group (34.8% ± 9.2%) had a significantly higher ventricular arrhythmia (VA) inducibility than the control (8.6% ± 3.8%; P <.01) and CKD-RDN (19.5% ± 6.3%; P = .01) groups. In the CKD-RDN group, ventricular fibrosis was significantly decreased compared to the CKD group (7.4% ± 2.0 % vs 10.4% ± 3.7%; P = .02). Sympathetic innervation in the CKD group was significantly increased compared to the control and CKD-RDN groups [left ventricle: 4.1 ± 1.8 vs 0.8 ± 0.5 (10² μm²/mm²), P <.01; 4.1 ± 1.8 vs 0.9± 0.6 (10² μm²/mm²), P <.01; right ventricle: 3.6 ± 1.0 vs 1.0 ± 0.4 (10² μm²/mm²), P <.01; 3.6 ± 1.0 vs 1.0 ± 0.5 (10² μm²/mm²), P <.01].

CONCLUSION

Neuromodulation by RDN demonstrated protective effects with less structural and electrical remodeling, leading to attenuated VAs. In a rabbit model of CKD, RDN plays a therapeutic role by lowering the risk of VA caused by autonomic dysfunction.

Evolving Cardiac Electrical Therapies for Advanced Heart Failure Patients

Symptomatic heart failure (HF) patients despite optimal medical therapy and advances such as invasive hemodynamic monitoring remain challenging to manage. While cardiac resynchronization therapy remains a highly effective therapy for a subset of HF patients with wide QRS, a majority of symptomatic HF patients are poor candidates for such. Recently, cardiac contractility modulation, neuromodulation based on carotid baroreceptor stimulation, and phrenic nerve stimulation have been approved by the US Food and Drug Administration and are emerging as therapeutic options for symptomatic HF patients. This state-of-the-art review examines the role of these evolving electrical therapies in advanced HF.