Deep and future insights into neuromodulation therapies for heart failure

The Optimal Dosage and Duration of ω-3 PUFA Supplementation in Heart Failure Management: Evidence from a Network Meta-Analysis

Heart failure is a progressive condition associated with a high mortality rate. Despite advancements in treatment, many patients continue to experience less-than-ideal outcomes. ω-3 (n-3) polyunsaturated fatty acids (PUFAs) have been studied as a potential supplementary therapy for heart failure, but the optimal dosage and duration of supplementation remain unclear. This network meta-analysis (NMA) aimed to assess the efficacy of various n-3 PUFA supplementation regimens in patients with heart failure, focusing on dose-dependent and time-dependent effects. We conducted a systematic search for randomized controlled trials (RCTs) on n-3 PUFA supplementation in heart failure till 13 September, 2024. The primary outcome was the change in heart function, specifically left ventricular ejection fraction. Secondary outcomes included changes in peak oxygen consumption (VO2), blood B-type natriuretic peptide concentrations, and quality of life. The safety analysis focused on dropout rates (i.e., patients leaving the study for any reason before completion) and all-cause mortality. A frequentist-based NMA was performed. This NMA, which included 14 RCTs with 9075 participants (mean age, 66.0 y; 23.3% female), found that high-dose n-3 PUFA supplementation (2000-4000 mg/d) over a duration of ≥1 y significantly improved left ventricular ejection fraction and peak VO2 compared with those of control groups. Lower doses and shorter treatment periods did not produce the same benefits. No significant differences were found in dropout rates or all-cause mortality between the n-3 PUFAs and control groups. Long-term, high-dose n-3 PUFA supplementation, particularly with a predominance of docosahexaenoic acid or eicosapentaenoic acid, enhances cardiac function in patients with heart failure without increasing risk of adverse events. Further well-designed RCTs with long treatment durations (i.e., >1 y) and stringent heart failure inclusion criteria are necessary to confirm these findings and reduce potential biases. This trial was registered at PROSPERO as CRD42024590476.

Potential Neuromodulation of the Cardio-Renal Syndrome

The cardio-renal syndrome (CRS) type 2 is defined as a progressive loss of renal function following a primary insult to the myocardium that may be either acute or chronic but is accompanied by a decline in myocardial pump performance. The treatment of patients with CRS is difficult, and the disease often progresses to end-stage renal disease that is refractory to conventional therapy. While a good deal of information is known concerning renal injury in the CRS, less is understood about how reflex control of renal sympathetic nerve activity affects this syndrome. In this review, we provide insight into the role of the renal nerves, both from the afferent or sensory side and from the efferent side, in mediating renal dysfunction in CRS. We discuss how interventions such as renal denervation and abrogation of systemic reflexes may be used to alleviate renal dysfunction in the setting of chronic heart failure. We specifically focus on a novel cardiac sensory reflex that is sensitized in heart failure and activates the sympathetic nervous system, especially outflow to the kidney. This so-called Cardiac Sympathetic Afferent Reflex (CSAR) can be ablated using the potent neurotoxin resinferitoxin due to the high expression of Transient Receptor Potential Vanilloid 1 (TRPV1) receptors. Following ablation of the CSAR, several markers of renal dysfunction are reversed in the post-myocardial infarction heart failure state. This review puts forth the novel idea of neuromodulation at the cardiac level in the treatment of CRS Type 2.

Proteomics Reveals Long-Term Alterations in Signaling and Metabolic Pathways Following Both Myocardial Infarction and Chemically Induced Denervation

Myocardial infraction (MI) is the principal risk factor for the onset of heart failure (HF). Investigations regarding the physiopathology of MI progression to HF have revealed the concerted engagement of other tissues, such as the autonomic nervous system and the medulla oblongata (MO), giving rise to systemic effects, important in the regulation of heart function. Cardiac sympathetic afferent denervation following application of resiniferatoxin (RTX) attenuates cardiac remodelling and restores cardiac function following MI. While the physiological responses are well documented in numerous species, the underlying molecular responses during the initiation and progression from MI to HF remains unclear. We obtained multi-tissue time course proteomics with a murine model of HF induced by MI in conjunction with RTX application. We isolated tissue sections from the left ventricle (LV), MO, cervical spinal cord and cervical vagal nerves at four time points over a 12-week study. Bioinformatic analyses consistently revealed a high statistical enrichment for metabolic pathways in all tissues and treatments, implicating a central role of mitochondria in the tissue-cellular response to both MI and RTX. In fact, the additional functional pathways found to be enriched in these tissues, involving the cytoskeleton, vesicles and signal transduction, could be downstream of responses initiated by mitochondria due to changes in neuronal pulse frequency after a shock such as MI or the modification of such frequency communication from the heart to the brain after RTX application. Development of future experiments, based on our proteomic results, should enable the dissection of more precise mechanisms whereby metabolic changes in neuronal and cardiac tissues can effectively ameliorate the negative physiological effects of MI via RTX application.

Clinical Implications of Changes in Respiratory Instability Following Transcatheter Aortic Valve Replacement

BACKGROUND

Respiratory instability, which can be quantified using respiratory stability time (RST), is associated with the severity and prognostic impact of the disease in patients with chronic heart failure. However, its clinical implications in patients with severe aortic stenosis receiving transcatheter aortic valve replacement (TAVR) remain unknown.

METHODS

Patients who received TAVR and had paired measurements of RST at a baseline and one week following TAVR were prospectively included. Changes in RST following TAVR and its impact on post-TAVR heart failure readmissions were investigated.

RESULTS

Seventy-one patients (median age, 86 years old; 35% men) were included. The baseline RST was correlated with the severity of heart failure including elevated levels of plasma B-type natriuretic peptide (p < 0.05 for all). RST improved significantly following TAVR from 34 (26, 37) s to 36 (33, 38) s (p < 0.001). Post-TAVR lower RST (<33 s, n = 18) was associated with a higher 2-year cumulative incidence of heart failure readmission (21% vs. 8%, p = 0.039) with a hazard ratio of 5.47 (95% confidence interval 0.90-33.2).

CONCLUSION

Overall, respiratory instability improved following TAVR. Persistent respiratory instability following TAVR was associated with heart failure recurrence.

RGS3L allows for an M2 muscarinic receptor-mediated RhoA-dependent inotropy in cardiomyocytes

The role and outcome of the muscarinic M₂ acetylcholine receptor (M₂R) signaling in healthy and diseased cardiomyocytes is still a matter of debate. Here, we report that the long isoform of the regulator of G protein signaling 3 (RGS3L) functions as a switch in the muscarinic signaling, most likely of the M₂R, in primary cardiomyocytes. High levels of RGS3L, as found in heart failure, redirect the G_i-mediated Rac1 activation into a G_i-mediated RhoA/ROCK activation. Functionally, this switch resulted in a reduced production of reactive oxygen species (- 50%) in cardiomyocytes and an inotropic response (+ 18%) in transduced engineered heart tissues. Importantly, we could show that an adeno-associated virus 9-mediated overexpression of RGS3L in rats in vivo, increased the contractility of ventricular strips by maximally about twofold. Mechanistically, we demonstrate that this switch is mediated by a complex formation of RGS3L with the GTPase-activating protein p190RhoGAP, which balances the activity of RhoA and Rac1 by altering its substrate preference in cardiomyocytes. Enhancement of this complex formation could open new possibilities in the regulation of the contractility of the diseased heart.

Neuromodulation for Refractory Angina, Heart Failure and Peripheral Vascular Disease

Use of spinal cord stimulation (SCS) has expanded beyond pain control. There are increasing indications in which SCS is being used. The understanding of central and peripheral neural pathways and their controlling influences on peripheral organs is better understood now. The concept of stimulating the spinal cord and modulating central pathways with SCS is already established. Different studies have shown the benefit with SCS on visceral pain control, improving quality of live in severe peripheral vascular disease and even assist in controlling the vago-sympathetic balance. We will discuss the art of implantation. Patient selection and stimulation with respect to current clinical data.

Devices and interventions for the prevention of adverse outcomes of tachycardia on heart failure

Heart failure (HF) is the leading cause of hospitalization in the USA. Despite advances in pharmacologic management, the incidence of HF is on the rise and survivability is persistently reduced. Sympathetic overdrive is implicated in the pathophysiology of HF, particularly HF with reduced ejection fraction (HFrEF). Tachycardia can be particularly deleterious and thus has spurred significant investigation to mitigate its effects. Various modalities including vagus nerve stimulation, baroreceptor activation therapy, spinal cord stimulation, renal sympathetic nerve denervation, left cardiac sympathetic denervation, and carotid body removal will be discussed. However, the effects of these modalities on tachycardia and its outcomes in HFrEF have not been well-studied. Further studies to characterize this are necessary in the future.

Influence of cardiac nerve status on cardiovascular regulation and cardioprotection

Neural elements of the intrinsic cardiac nervous system transduce sensory inputs from the heart, blood vessels and other organs to ensure adequate cardiac function on a beat-to-beat basis. This inter-organ crosstalk is critical for normal function of the heart and other organs; derangements within the nervous system hierarchy contribute to pathogenesis of organ dysfunction. The role of intact cardiac nerves in development of, as well as protection against, ischemic injury is of current interest since it may involve recruitment of intrinsic cardiac ganglia. For instance, ischemic conditioning, a novel protection strategy against organ injury, and in particular remote conditioning, is likely mediated by activation of neural pathways or by endogenous cytoprotective blood-borne substances that stimulate different signalling pathways. This discovery reinforces the concept that inter-organ communication, and maintenance thereof, is key. As such, greater understanding of mechanisms and elucidation of treatment strategies is imperative to improve clinical outcomes particularly in patients with comorbidities. For instance, autonomic imbalance between sympathetic and parasympathetic nervous system regulation can initiate cardiovascular autonomic neuropathy that compromises cardiac stability and function. Neuromodulation therapies that directly target the intrinsic cardiac nervous system or other elements of the nervous system hierarchy are currently being investigated for treatment of different maladies in animal and human studies.

Differential gene and lncRNA expression in the lower thoracic spinal cord following ischemia/reperfusion-induced acute kidney injury in rats

We used high-throughput RNA sequencing to analyze differential gene and lncRNA expression patterns in the lower thoracic spinal cord during ischemia/reperfusion (I/R)-induced acute kidney injury (AKI) in rats. We observed that of 32662 mRNAs, 4296 out were differentially expressed in the T8-12 segments of the spinal cord upon I/R-induced AKI. Among these, 62 were upregulated and 34 were downregulated in response to I/R (FDR < 0.05, |log₂FC| > 1). Further, 52 differentially expressed lncRNAs (35 upregulated and 17 downregulated) were identified among 3849 lncRNA transcripts. The differentially expressed mRNAs were annotated as “biological process,” “cellular components” and “molecular functions” through gene ontology enrichment analysis. KEGG pathway enrichment analysis showed that cell cycle and renin-angiotensin pathways were upregulated in response to I/R, while protein digestion and absorption, hedgehog, neurotrophin, MAPK, and PI3K-Akt signaling were downregulated. The RNA-seq data was validated by qRT-PCR and western blot analyses of select mRNAs and lncRNAs. We observed that Bax, Caspase-3 and phospho-AKT were upregulated and Bcl-2 was downregulated in the spinal cord in response to renal injury. We also found negative correlations between three lncRNAs (TCONS_00042175, TCONS_00058568 and TCONS_00047728) and the degree of renal injury. These findings provide evidence for differential expression of lncRNAs and mRNAs in the lower thoracic spinal cord following I/R-induced AKI in rats and suggest potential clinical applicability.

Independent prognostic importance of respiratory instability and sympathetic nerve activity in patients with chronic heart failure

BACKGROUND

Respiratory instability in chronic heart failure (CHF) is characterized by irregularly rapid respiration or non-periodic breathing rather than by Cheyne-Stokes respiration. We developed a new quantitative measure of respiratory instability (RSI) and examined its independent prognostic impact upon CHF.

METHODS

In 87 patients with stable CHF, respiratory flow and muscle sympathetic nerve activity (MSNA) were simultaneously recorded. RSI was calculated from the frequency distribution of respiratory spectral components and very low frequency components.

RESULTS

During a mean follow-up of 85±38 months, 24 patients died. Sixteen patients who died of cardiac causes had a lower RSI (16±6 vs. 30±21, p<0.01), a lower specific activity scale (4.3±1.4 Mets vs. 5.7±1.4 Mets, p<0.005), a higher MSNA burst area (16±5% vs. 11±4%, p<0.001), and a higher brain natriuretic peptide (BNP) level (514±559pg/ml vs. 234±311pg/ml, p<0.05) than 71 patients who did not die of cardiac causes. Multivariate analysis revealed that RSI (p=0.015), followed by MSNA burst area (p=0.033), was an independent predictor of subsequent all-cause deaths and that RSI (p=0.026), MSNA burst area (p=0.001), and BNP (p=0.048) were independent predictors of cardiac deaths. Patients at very high risk of fatal outcome could be identified by an RSI<20.

CONCLUSIONS

The daytime respiratory instability quantified by a new measure of RSI has prognostic importance independent of sympathetic nerve activation in patients with clinically stable CHF. An RSI of <20 identifies patients at very high risk for subsequent all-cause and cardiovascular death.