Pulmonary artery denervation reduces pulmonary artery pressure and induces histological changes in an acute porcine model of pulmonary hypertension

Autonomic nervous modulation: early treatment for pulmonary artery hypertension

Pulmonary artery hypertension (PAH) is a chronic vascular disease defined by the elevation of pulmonary vascular resistance and mean pulmonary artery pressure, which arises due to pulmonary vascular remodelling. Prior research has already established a link between the autonomic nervous system (ANS) and PAH. Therefore, the rebalancing of the ANS offers a promising approach for the treatment of PAH. The process of rebalancing involves two key aspects: inhibiting an overactive sympathetic nervous system and fortifying the impaired parasympathetic nervous system through pharmacological or interventional procedures. However, the understanding of the precise mechanisms involved in neuromodulation, whether achieved through medication or intervention, remains insufficient. This limited understanding hinders our ability to determine the appropriate timing and scope of such treatment. This review aims to integrate the findings from clinical and mechanistic studies on ANS rebalancing as a treatment approach for PAH, with the ultimate goal of identifying a path to enhance the safety and efficacy of neuromodulation therapy and improve the prognosis of PAH.

New Drugs and Therapies in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension is a chronic, progressive disorder of the pulmonary vasculature with associated pulmonary and cardiac remodeling. PAH was a uniformly fatal disease until the late 1970s, but with the advent of targeted therapies, the life expectancy of patients with PAH has now considerably improved. Despite these advances, PAH inevitably remains a progressive disease with significant morbidity and mortality. Thus, there is still an unmet need for the development of new drugs and other interventional therapies for the treatment of PAH. One shortcoming of currently approved vasodilator therapies is that they do not target or reverse the underlying pathogenesis of the disease process itself. A large body of evidence has evolved in the past two decades clarifying the role of genetics, dysregulation of growth factors, inflammatory pathways, mitochondrial dysfunction, DNA damage, sex hormones, neurohormonal pathways, and iron deficiency in the pathogenesis of PAH. This review focuses on newer targets and drugs that modify these pathways as well as novel interventional therapies in PAH.

Transcatheter interventions in refractory pulmonary artery hypertension and pulmonary embolism

Pulmonary artery hypertension causes remodeling of distal pulmonary arterial vasculature leading to increased resistance of the pulmonary arterial system, right ventricular dysfunction, and sudden cardiac death. The diagnosis of pulmonary arterial hypertension (PAH) diagnosis is made when mean pulmonary artery pressure during catheterization is ≥25 mmHg at rest, pulmonary vascular resistance (PVR) more than 3 wood units, a pulmonary capillary wedge pressure of <15 mmHg. One year survival rate is 86.3% and 5 year survival rate in PAH is 61.2%, and only 7 years of median survival. Although several breakthrough advances are made in the medical management for PAH, there are some patients who do not respond to medications and continue to detoriate despite optimal medical therapy. The non-responders to medical management are those patients whose right atrial pressure is >20 mmHg or cardiac index is <2.0 L/min/m2, which are pointers of poor prognosis. For medical refractory patients invasive procedures such as atrial septostomy, Potts shunt, and pulmonary artery denervation are a therapeutic or palliative strategy in the treatment of pulmonary artery hypertension and serve as a bridge before surgery and heart lung transplantation.

Pulmonary Artery Denervation for Pulmonary Arterial Hypertension: A Sham-Controlled Randomized PADN-CFDA Trial

BACKGROUND

World Health Organization (WHO) group 1 pulmonary arterial hypertension (PAH) is a progressive, debilitating disease. Previous observational studies have demonstrated that pulmonary artery denervation (PADN) reduces pulmonary artery pressures in PAH. However, the safety and effectiveness of PADN have not been established in a randomized trial.

OBJECTIVES

The aim of this study was to determine the treatment effects of PADN in patients with group 1 PAH.

METHODS

Patients with WHO group 1 PAH not taking PAH-specific drugs for at least 30 days were enrolled in a multicenter, sham-controlled, single-blind, randomized trial. Patients were assigned to receive PADN plus a phosphodiesterase-5 inhibitor or a sham procedure plus a phosphodiesterase-5 inhibitor. The primary endpoint was the between-group difference in the change in 6-minute walk distance from baseline to 6 months.

RESULTS

Among 128 randomized patients, those treated with PADN compared with sham had a greater improvement in 6-minute walk distance from baseline to 6 months (mean adjusted between-group difference 33.8 m; 95% CI: 16.7-50.9 m; P < 0.001). From baseline to 6 months, pulmonary vascular resistance was reduced by -3.0 ± 0.3 WU after PADN and -1.9 ± 0.3 WU after sham (adjusted difference -1.4; 95% CI: -2.6 to -0.2). PADN also improved right ventricular function, reduced tricuspid regurgitation, and decreased N-terminal pro-brain natriuretic peptide. Clinical worsening was less (1.6% vs 13.8%; OR: 0.11; 95% CI: 0.01-0.87), and a satisfactory clinical response was greater (57.1% vs 32.3%; OR: 2.79; 95% CI: 1.37-5.82) with PADN treatment during 6-month follow-up.

CONCLUSIONS

In patients with WHO group 1 PAH, PADN improved exercise capacity, hemodynamic status, and clinical outcomes during 6-month follow-up. (Safety and Efficacy of Pulmonary Artery Denervation in Patients With Pulmonary Arterial Hypertension [PADN-CFDA]; NCT03282266).

Current status of pulmonary artery denervation

Pulmonary hypertension is a progressive disease with a poor long-term prognosis and high mortality. Pulmonary artery denervation (PADN) is emerging as a potential novel therapy for this condition. The basis of pursuing a sympathetic denervation strategy has its origins in a body of experimental translation work that has demonstrated that denervation can reduce sympathetic nerve activity in various animal models. This reduction in pulmonary sympathetic nerve activity is associated with a reduction in pathological pulmonary hemodynamics in response to mechanical, pharmacological, and toxicologically induced pulmonary hypertension. The most common method of PADN is catheter-directed thermal ablation. Since 2014, there have been 12 reports on the role of PADN in 490 humans with pulmonary hypertension (311:179; treated: control). Of these, six are case series, three are randomized trials, and three are case reports. Ten studies used percutaneous PADN techniques, and two combined PADN with mitral and/or left atrial surgery. PADN treatment has low mortality and morbidity and is associated with an improved 6-minute walking distance, a reduction in both mean pulmonary artery pressure and pulmonary vascular resistance, and an improvement in cardiac output. These improved outcomes were seen over a median follow-up of 12 months (range 2–46 months). A recent meta-analysis of human trials also supports the effectiveness of PADN in carefully selected patients. Based on the current literature, PADN can be effective in select patients with pulmonary hypertension. Additional randomized clinical trials against best medical therapy are required.

Future Perspectives of Pulmonary Hypertension Treatment

Since the discovery of three major pathophysiological mechanisms of pulmonary arterial hypertension (PAH), including prostacyclin, endothelin and nitric oxide pathways, the therapeutic options for PAH have increased. Nevertheless, despite these advances, the prognosis remains unsatisfactory for many patients with PAH. With the progress of both pre-clinical and clinical research on PAH, several novel therapeutic targets have been identified for the treatment of PAH. In this study, we review updated information of novel pathophysiological pathways of pulmonary hypertension, mainly focusing on WHO Group I PAH. Drugs based on these pathways are currently under clinical or pre-clinical investigation, however they have been approved for clinical use. Large clinical trials are required to validate the clinical safety and effects of these novel therapies.

Percutaneous Treatments for Pulmonary Hypertension: Reviewing the Growing Procedural Role for Interventional Cardiology

Pulmonary arterial hypertension is a common and highly morbid medical problem resulting in elevated pulmonary arterial pressures and pulmonary vascular resistance. Medical therapies are costly, and not always well-tolerated. Surgical therapies such as pulmonary endarterectomy and lung transplantation are limited to a small subset of patients due to various patient, disease, or institutional factors. Over the past decade, there has been growing investigation into endovascular interventional therapies for patients with pulmonary hypertension such as balloon pulmonary angioplasty and pulmonary denervation. In this review, we describe the current status, future directions, and our recommendations on technical considerations with these therapies.

Transcatheter radiofrequency pulmonary artery denervation in swine: the evaluation of lesion degree, hemodynamics and pulmonary hypertension inducibility

Background

Mechanisms of positive effects of pulmonary artery (PA) denervation (PADN) remain poorly understood. The study aimed to evaluate pulmonary hemodynamic changes after PADN and their association with the extent of PA wall damage in an acute thromboxane A2 (TXA2)-induced pulmonary hypertension (PH) model in swine.

Methods

In this experimental sham-controlled study, 17 normotensive male white Landrace pigs (the mean weight 36.2 ± 4.5 kg) were included and randomly assigned to group I (n = 9)—PH modeling before and after PADN, group II (n = 4)—PADN only, or group III (n = 4)—PH modeling before and after a sham procedure. Radiofrequency (RF) PADN was performed in the PA trunk and at the proximal parts of the right and left PAs. PA wall lesions were characterized at the autopsy study using histological and the immunohistochemical examination.

Results

In groups I and II, no statistically significant changes in the mean pulmonary arterial pressure nor systemic blood pressure were found after PADN (−0.8 ± 3.4 vs 4.3 ± 8.6 mmHg, P = 0.47; and 6.0 ± 15.9 vs -8.3 ± 7.5 mmHg, P = 0.1; correspondingly). There was a trend towards a lower diastolic pulmonary arterial pressure after PADN in group I when compared with group III during repeat PH induction (34.4 ± 2.9 vs 38.0 ± 0.8; P = 0.06). Despite the presence of severe PA wall damage at the RF application sites, S100 expression was preserved in the majority of PA specimens. The presence of high-grade PA lesions was associated with HR acceleration after PADN (ρ = 0.68, p = 0.03). No significant correlation was found between the grade of PA lesion severity and PA pressure after PADN with or without PH induction.

Conclusions

Extended PADN does not affect PH induction using TXA2. Significant PA adventitia damage is associated with HR acceleration after PADN. Possible delayed effects of PADN on perivascular nerves and pulmonary hemodynamics require further research in chronic experiments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01786-y.

An Ovine Model for Percutaneous Pulmonary Artery Laser Denervation: Perivascular Innervation and Ablation Lesion Characteristics

Background: Pulmonary artery denervation (PADN) is an evolving interventional procedure capable to reduce pulmonary artery (PA) pressure. We aimed to compare PA nerve distribution in different specimens and assess the feasibility of an ovine model for a denervation procedure and evaluate the acute changes induced by laser energy. Methods: The experiment was divided into two phases: (1) the analysis of PA nerve distribution in sheep, pigs, and humans using histological and immunochemical methods; (2) fiberoptic PADN in sheep and postmortem laser lesion characteristics. Results: PA nerve density and distribution in sheep differ from humans, although pigs and sheep share similar characteristics, nerve fibers are observed in the media layer, adventitia, and perivascular tissue in sheep. Necrosis of the intima and focal hemorrhages within the media, adventitia, and perivascular adipose tissue were evidenced post laser PADN. Among the identified lesions, 40% reached adventitia and could be classified as effective for PADN. The use of 20 W ablation energy was safer and 30 W-ablation led to collateral organ damage. Conclusions: An ovine model is suitable for PADN procedures; however, nerve distribution in the PA bifurcation and main branches differ from human PA innervation. Laser ablation can be safely used for PADN procedures.

Sympathetic innervation of canine pulmonary artery and morphometric and functional analysis in dehydromonocrotaline-induced models after pulmonary artery denervation

OBJECTIVES

We aimed to describe the anatomic distribution of periarterial pulmonary sympathetic nerves and to observe the long-term morphometric and functional changes after pulmonary artery denervation (PADN), a novel therapy for pulmonary arterial hypertension (PAH).

METHODS

A total of 45 beagles were divided into a sympathetic innervation group (n = 3, 33.3% were females), a PAH group (n = 35, 34.3% were females) and a control group (n = 7, 28.5% were females). The PAH group was randomly divided into no-PADN (n = 7), instant-PADN (n = 7), 1M-PADN (n = 7), 2M-PADN (n = 7) and 3M-PADN (n = 7) subgroups. The sympathetic innervation group was sacrificed to reveal the sympathetic innervation of pulmonary arteries. PAH was induced by injecting dehydromonocrotaline (DHMCT) through the right atrium. The pulmonary capillary wedge pressure, right ventricular systolic pressure, right ventricular mean pressure, pulmonary artery systolic pressure and pulmonary artery mean pressure of each group were continuously measured. The cardiac output was detected to calculate the pulmonary vascular resistance. PAH and control groups were subjected to immunofluorescence assay, sympathetic nerve conduction velocity measurement and transmission electron microscopy.

RESULTS

The no-PADN group had significantly higher PVSP, PVMP, pulmonary artery systolic pressure, pulmonary artery mean pressure and pulmonary vascular resistance but lower cardiac output than those of the control group (P < 0.05). Instant-PADN, 1M-PADN, 2M-PADN and 3M-PADN groups had significantly lower PVSP, PVMP, pulmonary artery systolic pressure, pulmonary artery mean pressure and pulmonary vascular resistance but higher cardiac output than those of the no-PADN group (P < 0.05). Most sympathetic nerves were located within 2.5 mm of the intimae of the bifurcation and proximal trunk, mainly in the left trunk. The diameter and cross-sectional area of myelinated fibres in the PAH group were significantly larger than those of the control group. Sympathetic nerve conduction velocity of the PAH group gradually decreased, and nerve fibres were almost demyelinated 3 months after PADN.

CONCLUSIONS

PADN effectively relieved dehydromonocrotaline-induced canine PAH and decreased sympathetic nerve conduction velocity.

Neurohormonal modulation in pulmonary arterial hypertension

Pulmonary hypertension is a fatal condition of elevated pulmonary pressures, complicated by right heart failure. Pulmonary hypertension appears in various forms; one of those is pulmonary arterial hypertension (PAH) and is particularly characterised by progressive remodelling and obstruction of the smaller pulmonary vessels. Neurohormonal imbalance in PAH patients is associated with worse prognosis and survival. In this back-to-basics article on neurohormonal modulation in PAH, we provide an overview of the pharmacological and nonpharmacological strategies that have been tested pre-clinically and clinically. The benefit of neurohormonal modulation strategies in PAH patients has been limited by lack of insight into how the neurohormonal system is changed throughout the disease and difficulties in translation from animal models to human trials. We propose that longitudinal and individual assessments of neurohormonal status are required to improve the timing and specificity of neurohormonal modulation strategies. Ongoing developments in imaging techniques such as positron emission tomography may become helpful to determine neurohormonal status in PAH patients in different disease stages and optimise individual treatment responses.

[Pulmonary artery denervation in pulmonary hypertension: physiological and clinical aspects]

This article is a review of the findings of experimental and clinical studies of a new method of treatment of pulmonary hypertension - pulmonary artery denervation with the help of radiofrequency ablation, cryodenervation and ultrasonic impact. Pulmonary artery denervation results in decreased neurogenic tonic sympathetic and, probably, increased parasympathetic effects on pulmonary vessels. On models of experimental monocrotaline-induced pulmonary hypertension in various-species animals, it was determined that pulmonary artery denervation is followed by decreased activity of local pulmonary renin-angiotensin system, slowed processes of remodeling of pulmonary vessels, hypertrophy and fibrosis of the right ventricle, with inhibition of progression of pulmonary hypertension by means of suppression of extracellular signal-regulated kinase 1/2 (ERK 1/2) which regulates differentiation, proliferation and migration of smooth muscle cells. However, the problem of the pattern of pulmonary microcirculation changes (pre- and postcapillary resistance, capillary filtration coefficient) after pulmonary artery denervation warrants further study. The findings of clinical studies in patients with pulmonary hypertension suggest that pulmonary artery denervation inducing a decrease of pressure therein, as well as pulmonary vessel resistance did not lead to normalization of pulmonary haemodynamics.The mentioned impact partially removes the neurogenic component of multicircuit and multifactorial regulation of pulmonary circulation. Therefore, along with pulmonary artery denervation, further search for pharmacological agents selectively influencing pulmonary vessels remains a problem of current importance.

Neurohormonal Modulation as a Therapeutic Target in Pulmonary Hypertension

The autonomic nervous system (ANS) and renin-angiotensin-aldosterone system (RAAS) are involved in many cardiovascular disorders, including pulmonary hypertension (PH). The current review focuses on the role of the ANS and RAAS activation in PH and updated evidence of potential therapies targeting both systems in this condition, particularly in Groups 1 and 2. State of the art knowledge in preclinical and clinical use of pharmacologic drugs (beta-blockers, beta-three adrenoceptor agonists, or renin-angiotensin-aldosterone signaling drugs) and invasive procedures, such as pulmonary artery denervation, is provided.

Stimulation Mapping of the Pulmonary Artery for Denervation Procedures: an Experimental Study

Transcatheter pulmonary artery denervation (PADN) has been developed for the correction of pulmonary hypertension. We investigated pulmonary artery stimulation mapping and its role in PADN procedures. Artery stimulation was performed in 17 Landrace pigs. Low-frequency stimulation defined areas of ventricular and atrial capture. High-frequency stimulation evoked the following responses: sinus rhythm slowing and/or atrial rhythm acceleration in 59% of animals, phrenic nerve capture in 100%, and laryngeal recurrent nerve capture in 23%. The sites with evoked heart rate responses were marked by discrete radiofrequency ablations (RFA). An autopsy showed nerves in the adventitia and perivascular fat under the RFA sites, and the lack of muscarinic-1, tyrosine hydroxylase, and dopamine-5 receptors' expression. During PADN, areas adjacent to the course of phrenic and recurrent laryngeal nerves should be avoided. RFA at points with heart rate responses leads to the non-reproducibility of evoked reactions and the disappearance of neural markers' expression. Graphical abstract.

Emerging therapies for right ventricular dysfunction and failure

Therapeutic options for right ventricular (RV) dysfunction and failure are strongly limited. Right heart failure (RHF) has been mostly addressed in the context of pulmonary arterial hypertension (PAH), where it is not possible to discern pulmonary vascular- and RV-directed effects of therapeutic approaches. In part, opposing pathomechanisms in RV and pulmonary vasculature, i.e., regarding apoptosis, angiogenesis and proliferation, complicate addressing RHF in PAH. Therapy effective for left heart failure is not applicable to RHF, e.g., inhibition of adrenoceptor signaling and of the renin-angiotensin system had no or only limited success. A number of experimental studies employing animal models for PAH or RV dysfunction or failure have identified beneficial effects of novel pharmacological agents, with most promising results obtained with modulators of metabolism and reactive oxygen species or inflammation, respectively. In addition, established PAH agents, in particular phosphodiesterase-5 inhibitors and soluble guanylate cyclase stimulators, may directly address RV integrity. Promising results are furthermore derived with microRNA (miRNA) and long non-coding RNA (lncRNA) blocking or mimetic strategies, which can target microvascular rarefaction, inflammation, metabolism or fibrotic and hypertrophic remodeling in the dysfunctional RV. Likewise, pre-clinical data demonstrate that cell-based therapies using stem or progenitor cells have beneficial effects on the RV, mainly by improving the microvascular system, however clinical success will largely depend on delivery routes. A particular option for PAH is targeted denervation of the pulmonary vasculature, given the sympathetic overdrive in PAH patients. Finally, acute and durable mechanical circulatory support are available for the right heart, which however has been tested mostly in RHF with concomitant left heart disease. Here, we aim to review current pharmacological, RNA- and cell-based therapeutic options and their potential to directly target the RV and to review available data for pulmonary artery denervation and mechanical circulatory support.

The evolving role of interventional cardiology in the treatment of pulmonary hypertension

Pulmonary hypertension (PH) is a heterogeneous group of diseases defined by a mean pulmonary arterial pressure greater than 20 mmHg. Clinically, PH is classified into five groups and the group of PH generally defines the cause of PH and the therapeutic options. Currently, medical therapies that target the prostacyclin, endothelin, and nitric oxide pathways are used in pulmonary arterial hypertension and chronic thromboembolic PH (CTEPH) patients. Moreover, surgery can improve outcomes in PH as pulmonary thromboendarterectomy can be curative for CTEPH and lung transplantation is used for end-stage PH. Despite these diverse treatment options, PH patients continue to have high symptom burden and poor long-term outcomes. However, advances in percutaneous technology are opening new avenues for the management of PH. In this review, we discuss the available data supporting the use of four interventional procedures: balloon atrial septostomy, transcatheter Potts shunt, balloon pulmonary angioplasty, and pulmonary artery denervation for the treatment of PH. These procedures provide hemodynamic and functional improvements in PH patients, but they come with their own unique risk profiles. Hopefully, these procedures will continue to be refined and thereby provide a venue for interventional cardiology to safely and effectively improve outcomes for PH moving forward.

Pulmonary artery denervation for pulmonary arterial hypertension

Pulmonary arterial hypertension remains a progressive, life-limiting disease despite optimal medical therapy. Pulmonary artery denervation has arisen as a novel intervention in the treatment of pulmonary arterial hypertension, and other forms of pulmonary hypertension, with the aim of reducing the sympathetic activity of the pulmonary circulation. Pre-clinical studies and initial clinical trials have demonstrated that the technique can be performed safely with some positive effects on clinical, haemodynamic and echocardiographic markers of disease. The scope of the technique in current practice remains limited given the absence of well-designed, large-scale, international randomised controlled clinical trials. This review provides an overview of this exciting new treatment modality, including pathophysiology, technical innovations and recent trial results.

Intravascular Ultrasound Pulmonary Artery Denervation to Treat Pulmonary Arterial Hypertension (TROPHY1): Multicenter, Early Feasibility Study

OBJECTIVES

The aim of this study was to investigate whether therapeutic intravascular ultrasound pulmonary artery denervation (PDN) is safe and reduces pulmonary vascular resistance (PVR) in patients with pulmonary arterial hypertension (PAH) on a minimum of dual oral therapy.

BACKGROUND

Early studies have suggested that PDN can reduce PVR in patients with PAH.

METHODS

TROPHY1 (Treatment of Pulmonary Hypertension 1) was a multicenter, international, open-label trial undertaken at 8 specialist centers. Patients 18 to 75 years of age with PAH were eligible if taking dual oral or triple nonparenteral therapy and not responsive to acute vasodilator testing. Eligible patients underwent PDN (TIVUS System). The primary safety endpoint was procedure-related adverse events at 30 days. Secondary endpoints included procedure-related adverse events, disease worsening and death to 12 months, and efficacy endpoints that included change in pulmonary hemodynamic status, 6-min walk distance, and quality of life from baseline to 4 or 6 months. Patients were to remain on disease-specific medication for the duration of the study.

RESULTS

Twenty-three patients underwent PDN, with no procedure-related serious adverse events reported. The reduction in PVR at 4- or 6-month follow-up was 94 ± 151 dyn·s·cm-5 (p = 0.001) or 17.8%, which was associated with a 42 ± 63 m (p = 0.02) increase in 6-min walk distance and a 671 ± 1,555 step (p = 0.04) increase in daily activity.

CONCLUSIONS

In this multicenter early feasibility study, PDN with an intravascular ultrasound catheter was performed without procedure-related adverse events and was associated with a reduction in PVR and increases in 6-min walk distance and daily activity in patients with PAH on background dual or triple therapy.

NTP42, a novel antagonist of the thromboxane receptor, attenuates experimentally induced pulmonary arterial hypertension

BACKGROUND

NTP42 is a novel antagonist of the thromboxane prostanoid receptor (TP), currently in development for the treatment of pulmonary arterial hypertension (PAH). PAH is a devastating disease with multiple pathophysiological hallmarks including excessive pulmonary vasoconstriction, vascular remodelling, inflammation, fibrosis, in situ thrombosis and right ventricular hypertrophy. Signalling through the TP, thromboxane (TX) A₂ is a potent vasoconstrictor and mediator of platelet aggregation. It is also a pro-mitogenic, pro-inflammatory and pro-fibrotic agent. Moreover, the TP also mediates the adverse actions of the isoprostane 8-iso-prostaglandin F_2α, a free-radical-derived product of arachidonic acid produced in abundance during oxidative injury. Mechanistically, TP antagonists should treat most of the hallmarks of PAH, including inhibiting the excessive vasoconstriction and pulmonary artery remodelling, in situ thrombosis, inflammation and fibrosis. This study aimed to investigate the efficacy of NTP42 in the monocrotaline (MCT)-induced PAH rat model, alongside current standard-of-care drugs.

METHODS

PAH was induced by subcutaneous injection of 60 mg/kg MCT in male Wistar-Kyoto rats. Animals were assigned into groups: 1. 'No MCT'; 2. 'MCT Only'; 3. MCT + NTP42 (0.25 mg/kg BID); 4. MCT + Sildenafil (50 mg/kg BID), and 5. MCT + Selexipag (1 mg/kg BID), where 28-day drug treatment was initiated within 24 h post-MCT.

RESULTS

From haemodynamic assessments, NTP42 reduced the MCT-induced PAH, including mean pulmonary arterial pressure (mPAP) and right systolic ventricular pressure (RSVP), being at least comparable to the standard-of-care drugs Sildenafil or Selexipag in bringing about these effects. Moreover, NTP42 was superior to Sildenafil and Selexipag in significantly reducing pulmonary vascular remodelling, inflammatory mast cell infiltration and fibrosis in MCT-treated animals.

CONCLUSIONS

These findings suggest that NTP42 and antagonism of the TP signalling pathway have a relevant role in alleviating the pathophysiology of PAH, representing a novel therapeutic target with marked benefits over existing standard-of-care therapies.

Electrical Stimulation-Guided Approach to Pulmonary Artery Catheter Ablation in Patients with Idiopathic Pulmonary Arterial Hypertension: A Pilot Feasibility Study with a 12-Month Follow-Up

Background

Recently, transcatheter pulmonary artery (PA) ablation aiming at sympathetic denervation has been proposed in pulmonary arterial hypertension (PAH). This pilot feasibility study aimed to assess the feasibility of selective radiofrequency PA ablation based on response to high-frequency stimulation mapping.

Methods

The study comprised 3 female patients with idiopathic PAH (IPAH). The following reactions to PA stimulation were noted and marked by color points on the three-dimensional map: sinus bradycardia (heart rate decrease ≥15%), tachycardia (heart rate increase ≥15%), phrenic nerve capture, and cough. Since the most appropriate ablation strategy was unknown, two approaches were suggested, according to stimulation results: ablation at points with any heart rate response (either bradycardia or tachycardia)—this approach was applied in patient #1 (IPAH long-term responder to calcium channel blockers); segmental ablation at points with no response and with tachycardia response (one IPAH long-term responder to calcium channel blockers patient and one–IPAH with negative vasoreactive testing). Hemodynamic measurements were performed before and after denervation. Follow-up visits were scheduled at 6 and 12 months.

Results

Six-months follow-up was uneventful for patients #1 and 3; patient #2 had one syncope and reduced 6-minute walk test distance and peak VO₂ consumption. At 12 months, there was a normalization of mean PA pressure and pulmonary vascular resistance (PVR) in patient #1. Patient #2 had no change in PA pressure and PVR at 12 months. Patient #3 remained in II functional class; however, there was an increase in mean PA pressure and loss of vasoreactivity.

Conclusions

Electrical high-frequency stimulation of the PA identifies several types of evoked reactions: heart rate slowing, acceleration, phrenic nerve capture, and cough. The improvement in clinical and hemodynamic parameters following targeted PA ablation in the IPAH patient with positive vasoreactive testing should be confirmed in larger studies.

Pulmonary Artery Denervation as an Innovative Treatment for Pulmonary Hypertension With and Without Heart Failure

Pulmonary hypertension (PH) is categorized into 5 groups based on etiology. The 2 most prevalent forms are pulmonary arterial hypertension (PAH) and PH due to left heart disease (PH-LHD). Therapeutic options do exist for PAH to decrease symptoms and improve functional capacity; however, the mortality rate remains high and clinical improvements are limited. PH-LHD is the most common cause of PH; however, no treatment exists and the use of PAH-therapies is discouraged. Pulmonary artery denervation (PADN) is an innovative catheter-based ablation technique targeting the afferent and efferent fibers of a baroreceptor reflex in the main pulmonary artery (PA) trunk and its bifurcation. This reflex is involved in the elevation of the PA pressure seen in PH. Since 2013, both animal trials and human trials have shown the efficacy of PADN in improving PAH, including improved hemodynamic parameters, increased functional capacity, decreased PA remodeling, and much more. PADN has been shown to decrease the rate of rehospitalization, PH-related complications, and death, and is an overall safe procedure. PADN has also been shown to be effective for PH-LHD. Additional therapeutic mechanisms and benefits of PADN are discussed along with new PADN techniques. PADN has shown efficacy and safety as a potential treatment option for PH.

Pulmonary arterial hypertension: the case for a bioelectronic treatment

Pulmonary arterial hypertension (PAH) is a rare disease of unknown etiology that progresses to right ventricular failure. It has a complex pathophysiology, which involves an imbalance between vasoconstrictive and vasodilative processes in the pulmonary circulation, pulmonary vasoconstriction, vascular and right ventricular remodeling, systemic inflammation, and autonomic imbalance, with a reduced parasympathetic and increased sympathetic tone. Current pharmacological treatments for PAH include several classes of drugs that target signaling pathways in vascular biology and cardiovascular physiology, but they can have severe unwanted effects and they do not typically stop the progression of the disease. Pulmonary artery denervation has been tested clinically as a method to suppress sympathetic overactivation, however it is a nonspecific and irreversible intervention. Bioelectronic medicine, in particular vagus nerve stimulation (VNS), has been used in cardiovascular disorders like arrhythmias, heart failure and arterial hypertension and could, in principle, be tested as a treatment in PAH. VNS can produce pulmonary vasodilation and renormalize right ventricular function, via activation of pulmonary and cardiac vagal fibers. It can suppress systemic inflammation, via activation of fibers that innervate the spleen. Finally, VNS can gradually restore the balance between parasympathetic and sympathetic tone by regulating autonomic reflexes. Preclinical studies support the feasibility of using VNS in PAH. However, there are challenges with such an approach, arising from the need to affect a relatively small number of relevant vagal fibers, and the potential for unwanted cardiac and noncardiac effects of VNS in this sensitive patient population.

Pulmonary artery denervation using catheter-based ultrasonic energy

AIMS

Pulmonary arterial hypertension is a devastating disease characterised by pulmonary vascular remodelling and right heart failure. Radio-frequency pulmonary artery denervation (PDN) has improved pulmonary haemodynamics in preclinical and early clinical studies; however, denervation depth is limited. High-frequency non-focused ultrasound can deliver energy to the vessel adventitia, sparing the intima and media. We therefore aimed to investigate the feasibility, safety and efficacy of ultrasound PDN.

METHODS AND RESULTS

Histological examination demonstrated that innervation of human pulmonary arteries is predominantly sympathetic (71%), with >40% of nerves at a depth of >4 mm. Finite element analysis of ultrasound energy distribution and ex vivo studies demonstrated generation of temperatures >47ºC to a depth of 10 mm. In domestic swine, PDN reduced mean pulmonary artery pressure induced by thromboxane A2 in comparison to sham. No adverse events were observed up to 95 days. Histological examination identified structural and immunohistological changes of nerves in PDN-treated animals, with sparing of the intima and media and reduced tyrosine hydroxylase staining 95 days post procedure, indicating persistent alteration of the structure of sympathetic nerves.

CONCLUSIONS

Ultrasound PDN is safe and effective in the preclinical setting, with energy delivery to a depth that would permit targeting sympathetic nerves in humans.

Pulmonary Artery Denervation: Update on Clinical Studies

PURPOSE OF REVIEW

Sympathetic overactivity plays an important role in the progression of pulmonary arterial hypertension (PAH). The purpose of this review is to illustrate localization of pulmonary arterial sympathetic nerves, the key steps of pulmonary artery denervation (PADN) procedure, and to highlight clinical outcomes.

RECENT FINDINGS

Sympathetic nerves mostly occurred in the posterior region of the bifurcation and pulmonary trunk. Emerging preclinical data provided the potential of PADN for PAH. PADN, produced at bifurcation area, improved a profound reduction of pulmonary arterial pressure and ameliorated clinical outcomes with an exclusive ablation catheter. The application of PADN in the patients of PAH or combined pre-capillary and post-capillary PH (CpcPH) improved the hemodynamic parameters and increased 6MWD. Sympathetic overactivity aggravates PAH. PADN is a promising interventional treatment for PAH and CpcPH. Additional clinical trials are warranted to confirm the efficacy of PADN.

Long-Term High-Altitude Hypoxia and Alpha Adrenoceptor-Dependent Pulmonary Arterial Contractions in Fetal and Adult Sheep

Autonomic innervation of the pulmonary vasculature triggers vasomotor contractility predominately through activation of alpha-adrenergic receptors (α-ARs) in the fetal circulation. Long-term hypoxia (LTH) modulates pulmonary vasoconstriction potentially through upregulation of α₁-AR in the vasculature. Our study aimed to elucidate the role of α-AR in phenylephrine (PE)-induced pulmonary vascular contractility, comparing the effects of LTH in the fetal and adult periods on α-AR subtypes and PE-mediated Ca²⁺ responses and contractions. To address this, we performed wire myography, Ca²⁺ imaging, and mRNA analysis of pulmonary arteries from ewes and fetuses exposed to LTH or normoxia. Postnatal maturation depressed PE-mediated contractile responses. α₂-AR activation contracted fetal vessels; however, this was suppressed by LTH. α_1A- and α_1B-AR subtypes contributed to arterial contractions in all groups. The α_1D-AR was also important to contractility in fetal normoxic vessels and LTH mitigated its function. Postnatal maturity increased the number of myocytes with PE-triggered Ca²⁺ responses while LTH decreased the percentage of fetal myocytes reacting to PE. The difference between myocyte Ca²⁺ responsiveness and vessel contractility suggests that fetal arteries are sensitized to changes in Ca²⁺. The results illustrate that α-adrenergic signaling and vascular function change during development and that LTH modifies adrenergic signaling. These changes may represent components in the etiology of pulmonary vascular disease and foretell the therapeutic potential of adrenergic receptor antagonists in the treatment of pulmonary hypertension.

Transthoracic Pulmonary Artery Denervation for Pulmonary Arterial Hypertension

Objective—

Pulmonary arterial hypertension is characterized by progressive pulmonary vascular remodeling and persistently elevated mean pulmonary artery pressures and pulmonary vascular resistance. We aimed to investigate whether transthoracic pulmonary artery denervation (TPADN) attenuated pulmonary artery (PA) remodeling, improved right ventricular (RV) function, and affected underlying mechanisms. We also explored the distributions of sympathetic nerves (SNs) around human PAs for clinical translation.

Approach and Results—

We identified numerous SNs in adipose and connective tissues around the main PA trunks and bifurcations in male Sprague Dawley rats, which were verified in samples from human heart transplant patients. Pulmonary arterial hypertensive rats were randomized into TPADN and sham groups. In the TPADN group, SNs around the PA trunk and bifurcation were completely and accurately removed under direct visualization. The sham group underwent thoracotomy. Hemodynamics, RV function, and pathological changes in PA and RV tissues were measured via right heart catheterization, cardiac magnetic resonance imaging, and pathological staining, respectively. Compared with the sham group, the TPADN group had lower mean pulmonary arterial pressures, less PA and RV remodeling, and improved RV function. Furthermore, TPADN inhibited neurohormonal overactivation of the sympathetic nervous system and renin-angiotensin-aldosterone system and regulated abnormal expressions and signaling of neurohormone receptors in local tissues.

Conclusions—

There are numerous SNs around the rat and human main PA trunks and bifurcations. TPADN completely and accurately removed the main SNs around PAs and attenuated pulmonary arterial hypertensive progression by inhibiting excessive activation of the sympathetic nervous system and renin-angiotensin-aldosterone system neurohormone-receptor axes.

EXPRESS: Statement on imaging and pulmonary hypertension from the Pulmonary Vascular Research Institute (PVRI)

Pulmonary hypertension (PH) is highly heterogeneous and despite treatment advances it remains a life-shortening condition. There have been significant advances in imaging technologies, but despite evidence of their potential clinical utility, practice remains variable, dependent in part on imaging availability and expertise. This statement summarizes current and emerging imaging modalities and their potential role in the diagnosis and assessment of suspected PH. It also includes a review of commonly encountered clinical and radiological scenarios, and imaging and modeling-based biomarkers. An expert panel was formed including clinicians, radiologists, imaging scientists, and computational modelers. Section editors generated a series of summary statements based on a review of the literature and professional experience and, following consensus review, a diagnostic algorithm and 55 statements were agreed. The diagnostic algorithm and summary statements emphasize the key role and added value of imaging in the diagnosis and assessment of PH and highlight areas requiring further research.

Effects of Pulmonary Hypertension and Right Ventricular Function in Short and Long-Term Kidney Function

BACKGROUND

Pulmonary hypertension is not uncommon in patients with renal disease and vice versa; therefore, it influences treatments and outcomes. There is a large body of literature on pulmonary hypertension in patients with kidney disease, its prognostic implications, economic burden, and management strategies. However, the converse, namely the hemodynamic effects of pulmonary hypertension on kidney function (acute and chronic kidney injury) is less studied and described. There is also increasing interest in the effects of pulmonary hypertension on kidney transplant outcomes. The relationship is a complex phenomenon and multiple body systems and mechanisms are involved in its pathophysiology. Although the definition of pulmonary hypertension has evolved over time with the understanding of multiple interplays between the heart, lungs, kidneys, etc; there is limited evidence to provide a specific treatment strategy when kidneys and lungs are affected at the same time. Nevertheless, available evidence appears to support new therapeutics and highlights the importance of individualized approach. There is sufficient research showing that the morbidity and mortality from PH are driven by the influence of the pulmonary hemodynamic dysfunction on the kidneys.

CONCLUSION

This concise review focuses on the effects of pulmonary hypertension on the kidneys, including, the patho-physiological effects of pulmonary hypertension on acute kidney injury, progression of CKD, effects on kidney transplant outcomes, progression of kidney disease in situations such as post LVAD implantation and novel diagnostic indices. We believe a review of this nature will fill in an important gap in understanding the prognostic implication of pulmonary hypertension on renal disease, and help highlight this important component of the cardio-reno-pulmonary axis.

Electrical Vagal Nerve Stimulation Ameliorates Pulmonary Vascular Remodeling and Improves Survival in Rats With Severe Pulmonary Arterial Hypertension

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Autonomic imbalance has been documented in patients with PAH.

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Electrical VNS is known to restore autonomic balance and improve heart failure.

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This study aimed to elucidate the therapeutic effects of VNS on severe PAH in a rat model.

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VNS significantly restored autonomic balance, decreased mean pulmonary arterial pressure, attenuated pulmonary vascular remodeling, and preserved right ventricular function. In addition, VNS markedly improved the survival of rats with PAH.

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Our findings may contribute greatly to the development of device therapy for PAH and widen the clinical applicability of VNS.

This study aimed to elucidate the therapeutic effects of electrical vagal nerve stimulation (VNS) on severe pulmonary arterial hypertension in a rat model. In a pathophysiological study, VNS significantly restored autonomic balance, decreased mean pulmonary arterial pressure, attenuated pulmonary vascular remodeling, and preserved right ventricular function. In a survival study, VNS significantly improved the survival rate in both the prevention (VNS from 0 to 5 weeks after a SU5416 injection) and treatment (VNS from 5 to 10 weeks) protocols. Thus, VNS may serve as a novel therapeutic strategy for pulmonary arterial hypertension.

Inhaled Fasudil Lacks Pulmonary Selectivity in Thromboxane-Induced Acute Pulmonary Hypertension in Newborn Lambs

INTRODUCTION

Pulmonary hypertension (PH) is a potentially deadly disease for infants and adults with few existing medical interventions and no cure. In PH, increased blood pressure in the pulmonary artery eventually leads to heart failure. Fasudil, an antagonist of Rho-kinase, causes vasodilation leading to decreased systemic artery pressure and pulmonary artery pressure (PAP). This study compared the effects of fasudil administered as either an intravenous infusion or inhaled aerosol in newborn lambs.

HYPOTHESIS

Inhaled aerosol delivery of fasudil will provide selective pulmonary vasodilation when compared with intravenous administration.

METHODS

Newborn lambs (∼11 days) were surgically instrumented and mechanically ventilated under anesthesia. A pulmonary artery catheter and ultrasonic flow probe were inserted to measure hemodynamics. Acute PH was pharmaceutically induced via continuous intravenous infusion of thromboxane. After achieving a 2- to 3-fold elevation of PAP, fasudil was administered either as intravenous infusion (2.5 mg/kg) or inhaled aerosol (100 mg of fasudil in 2 mL of saline). Changes in PAP, mean systemic arterial pressure (MABP), pulmonary vascular resistance (PVR), systemic vascular resistance (SVR), cardiac output, and heart rate were assessed. In addition, plasma concentrations of fasudil were measured.

RESULTS

Both routes of fasudil delivery produced significant decreases in PAP and PVR but also produced similar decreases in MABP and SVR. The C_max for intravenous fasudil was greater than that for inhaled fasudil.

CONCLUSIONS

These results suggest inhaled fasudil lacks pulmonary selectivity when compared with intravenous fasudil.

Effects of renal denervation on monocrotaline induced pulmonary remodeling

Pulmonary artery hypertension (PAH) is a rapidly progressive disorder, which leads to right heart failure and even death. Overactivity of the renin-angiotensin-aldosterone system (RAAS) and sympathetic nervous system accounts for the development and progression of PAH. The role of renal denervation (RDN) in different periods of PAH has not been fully elucidated. A single intraperitoneal injection of monocrotaline (MCT, 60 mg/kg) was used to induce pulmonary remodeling in male Sprague Dawley rats (n = 40). After 24-hour of MCT administration, a subset of rats underwent RDN (RDN_24h, n = 10); after 2-week of MCT injection, another ten rats received RDN treatment (RDN_2w, n = 10) and the left 20 rats were divided to MCT group with sham RDN operation (MCT, n = 20). Eight rats in Control group received intraperitoneal injection of normal saline (60 mg/kg) once and sham RDN surgery. After 35 days, tissue and blood samples were collected. Histological analysis demonstrated that the collagen volume fraction of right ventricle, lung tissue and pulmonary vessel reduced significantly in RDN_24h group but not in the RDN2w group, compared with MCT group. Moreover, the earlier RDN treatment significantly decreased SNS activity and blunted RAAS activation. Importantly, RDN treatment significantly improved the survival rate. In summary, earlier RDN treatment could attenuate cardio-pulmonary fibrosis and therefore might be a promising approach to prevent the development of PAH.

ENDOVASCULAR TREATMENT OF THE RESIDUAL THROMBOEMBOLIC PULMONARY HYPERTENSION AFTER PULMONARY THROMBENDARTERECTOMY WITH THE DENERVATION SYSTEM SYMPLICITY

Aim. To assess the safety and efficacy of radiofrequency denervation of pulmonary artery (PA) with the Simplicity system in patients with residual pulmonary hypertension (PH) after the thromberarterectomy surgery.

Material and methods. To the study, 12 patients included, with the signs of residual PH (by echocardiography data, mean PH pressure ≥25 mmHg), who had undergone surgery (thrombendarcterectomy) for chronic thromboembolic PH. Mean time interval between the diagnosis of PH and pulmonary denervation was 8,5 years. After catheterization of the right chambers of the heart and tensiometry in small circle circulation, the spot circular radiofrequency denervation performed of the right and left PH at the area of ostia, with ablation catheter Simplicity. The success was defined by decrease of mean PA pressure >10 mmHg, absence of complications, exercise tolerance increase after the procedure immediately and in 12 months.

Results. At long term period after the intervention there was significant decrease of mean PA pressure from 58±6 to 33±4 mmHg (p<0,01), of pulmonary vascular pressure from 8,6±2,1 to 3,2±1,4 mmHg (p<0,01) and increase of exercise tolerance from 321±19 m to 487±29 m (p<0,01). During the follow up period, 1 patient died in 8 months after inclusion due to severe gastrointestinal bleeding. The rest did not present with adverse events or non­planned hospitalizations. Nine patients noted significant improvement of general health, decrease of dyspnea and fatigue, 3 patients had discontinued sildenafil. There were no complications at PA radiofrequency ablation procedure (death, arrhythmias, PA perforation, acute PA thrombosis in the place of access, bleeding).

Conclusion. Utilization of the Simplicity system in PA denervation is safe and effective. Further randomized studies in need to confirm clinical benefits from the procedures in PH patients.

Interventional Therapies in Pulmonary Hypertension

Despite advances in drug therapy, pulmonary hypertension-particularly arterial hypertension (PAH)-remains a fatal disease. Untreatable right heart failure (RHF) from PAH eventually ensues and remains a significant cause of death in these patients. Lowering pulmonary input impedance with different PAH-specific drugs is the obvious therapeutic target in RHF due to chronically increased afterload. However, potential clinical gain can also be expected from attempts to unload the right heart and increase systemic output. Atrial septostomy, Potts anastomosis, and pulmonary artery denervation are interventional procedures serving this purpose. Percutaneous balloon pulmonary angioplasty, another interventional therapy, has re-emerged in the last few years as a clear alternative for the management of patients with distal, inoperable, chronic thromboembolic pulmonary hypertension. The current review discusses the physiological background, experimental evidence, and potential clinical and hemodynamic benefits of all these interventional therapies regarding their use in the setting of RHF due to severe pulmonary hypertension.

Autonomic nervous system involvement in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a chronic pulmonary vascular disease characterized by increased pulmonary vascular resistance (PVR) leading to right ventricular (RV) failure. Autonomic nervous system involvement in the pathogenesis of PAH has been demonstrated several years ago, however the extent of this involvement is not fully understood. PAH is associated with increased sympathetic nervous system (SNS) activation, decreased heart rate variability, and presence of cardiac arrhythmias. There is also evidence for increased renin-angiotensin-aldosterone system (RAAS) activation in PAH patients associated with clinical worsening. Reduction of neurohormonal activation could be an effective therapeutic strategy for PAH. Although therapies targeting adrenergic receptors or RAAS signaling pathways have been shown to reverse cardiac remodeling and improve outcomes in experimental pulmonary hypertension (PH)-models, the effectiveness and safety of such treatments in clinical settings have been uncertain. Recently, novel direct methods such as cervical ganglion block, pulmonary artery denervation (PADN), and renal denervation have been employed to attenuate SNS activation in PAH. In this review, we intend to summarize the multiple aspects of autonomic nervous system involvement in PAH and overview the different pharmacological and invasive strategies used to target autonomic nervous system for the treatment of PAH.

Kidney dysfunction in patients with pulmonary arterial hypertension

Pulmonary arterial hypertension (PH) and chronic kidney disease (CKD) both profoundly impact patient outcomes, whether as primary disease states or as co-morbid conditions. PH is a common co-morbidity in CKD and vice versa. A growing body of literature describes the epidemiology of PH secondary to chronic kidney disease and end-stage renal disease (ESRD) (WHO group 5 PH). But, there are only limited data on the epidemiology of kidney disease in group 1 PH (pulmonary arterial hypertension [PAH]). The purpose of this review is to summarize the current data on epidemiology and discuss potential disease mechanisms and management implications of kidney dysfunction in PAH. Kidney dysfunction, determined by serum creatinine or estimated glomerular filtration rate, is a frequent co-morbidity in PAH and impaired kidney function is a strong and independent predictor of mortality. Potential mechanisms of PAH affecting the kidneys are increased venous congestion, decreased cardiac output, and neurohormonal activation. On a molecular level, increased TGF-β signaling and increased levels of circulating cytokines could have the potential to worsen kidney function. Nephrotoxicity does not seem to be a common side effect of PAH-targeted therapy. Treatment implications for kidney disease in PAH include glycemic control, lifestyle modification, and potentially Renin-Angiotensin-Aldosterone System (RAAS) blockade.

Future perspectives in pulmonary arterial hypertension

While there have been advances in the field of pulmonary arterial hypertension (PAH), disease management remains suboptimal for many patients. The development of novel treatments and strategies can provide opportunities to target other mechanisms that play a role in the complex pathobiology of PAH outside of the three main pathophysiological pathways. In this review, we highlight some of the potential PAH therapies or techniques that are being, or have been, investigated in phase II clinical trials. This review also discusses potential points for consideration in the development of novel therapies that target putative disease mediators or modifiers.

Novel therapies and well-designed trials are important for improving the management of PAH patientshttp://ow.ly/YHPY304XdvH

Hemodynamic, functional, and clinical responses to pulmonary artery denervation in patients with pulmonary arterial hypertension of different causes: phase II results from the Pulmonary Artery Denervation-1 study

The mechanisms underlying pulmonary arterial hypertension (PAH) are multifactorial. The efficacy of pulmonary artery denervation (PADN) for idiopathic PAH treatment has been evaluated. This study aimed to analyze the hemodynamic, functional, and clinical responses to PADN in patients with PAH of different causes.