The discrepancy between FDG uptake and myocardial fibrosis in patients with pulmonary arterial hypertension – PET/MRI study

Background

Inflammatory processes play an important role in pulmonary arterial hypertension (PAH) pathophysiology. We previously confirmed that in case of right ventricle (RV) failure, changes of cytokines' levels are correlated with myocardial metabolic and hemodynamic alterations observed in PET/MRI hybrid imaging. Presence of late gadolinium enhancement (LGE) in RV insertion points (RVIPs) has been found in majority of PAH patients and is often recognized as evidence of myocardial fibrosis due to RV pressure overload. As qualitative and/or quantitative assessments of LGE may vary due to natural PAH progression or specific therapy, we hypothesized that simple presence of LGE at RVIPs is not unequivocal to fibrotic tissue (without metabolic activity).

Purpose

To check the relationship between LGE mass and 18F-fluorodexyglucose uptake in RV insertion points in PAH patients using PET/MRI hybrid imaging.

Methods

Twenty-eight clinically stable PAH patients (49.9±15.9 years) had simultaneous PET/MRI scans during baseline and follow up (FU) visits, Figure. 18F-fluorodexyglucose (FDG) was used as a tracer and its cardiac uptake was presented as a maximum standardized uptake value (SUV) for RV insertion points (SUV in RVIPS). Septal delayed enhancement mass was quantified in RVIPs and presented as LGE mass. Occurrences of clinical end-points (CEP, defined as death or clinical deterioration) were assessed during 24 months observation.

Results

LGE was found in RVIPs of all PAH patients. Mean LGE mass was 6.32±4.41 g and mean SUV in RVIPS was 7.28±5.36. Follow up values were 8.01±7.75g (p=0.4) and 5.80±3.16 (p=0.16), respectively. We observed significant correlation between baseline SUV in RVIPS and mean pulmonary pressure, mPAP (r=0.49, p=0.04) but no correlation was found between LGE mass and SUV in RVIPS (in both baseline and FU scans).

Between baseline and follow up visits, 16 patients had CEP and needed PAH therapy escalation. CEP+ group of PAH patients presented higher baseline LGE mass (7.53±4.75 vs 3.92±2.21, p=0.04) and SUV in RVIPS (7.27±5.42 vs 6.01±4.52, p=0.4). In all CEP patients who initiated prostacycline therapy and survived (n=8, 50%), SUV in RVIPS decreased in FU PET scans together with an increase in LGE mass in MRI. At FU visits we also observed significant improvement of MRI-derived RV ejection fraction (45.1±9.6% to 52.4±12.9%, p=0.01), and mPAP (50.5±18.3 to 42.8±18.6 mmHg, p=0.03).

Conclusions

Effective PAH therapy have an impact on both LGE mass and FDG uptake in cardiac local tissue changes. Since there was no correlation between LGE mass and FDG uptake RV insertion points, the question arises what the cause of these LGE changes is. Increased fibrosis should cause diminished local glucose metabolism. This phenomenon opens new questions concerning pathophysiology processes in RVIPs and requires confirmation on bigger PAH population.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Center for Science in Poland

Impact of COVID-19 pandemics upon nationwide pulmonary hypertension cohort: 18-months analysis of BNP-PL national database

Introduction

Pulmonary hypertension (PH) patients may be vulnerable to SARS-CoV-2 infection, but large analytic studies on morbidity and mortality risks are limited.

Aim

Assessment of the incidence and course of COVID-19 among patients (pts) diagnosed with PH, treated under the NFZ program, registered in the national BNP-PL database with the assessment of the impact of the SARS-CoV-2 pandemic on the care of patients with pulmonary hypertension in Poland.

Methods

We analyzed the records of the complete population of Polish pts treated under the National Drug Program of PH (PAH and CTEPH), registered in the national database of BNP-PL, and updated on an ongoing basis by all PH centers. The frequency of SARS-CoV-2 infections, clinical severity of COVID-19 course and mortality were reviewed. Clinical characteristics of infected and deceased patients were compared to the remaining patients registered in the BNP-PL database. The rate of increase of new diagnoses ended with inclusion in the Drug Program between 01 March 2020 and 31 August 2021, compared to the pre-pandemic year 2019, and the change in the treatment profile were reviewed.

Results

The analysis included 1923 pts (PAH 1292, CTEPH 631). The incidence of SARS-CoV-2 infections was 7.4% (n=143) and similar to general population (7.6%), with a slight preponderance in PAH 8.1% (n=105) vs. CTEPH 6.0% (n=38) (p=0.099). 47 patients (33%) required hospitalization. Mortality rate was 24% (34/143) vs. 2.6% for general population – including 19/34 outside of hospital. Those who died due to COVID-19 were older (mean age 56±17.6 vs. 70.5±12.8 yrs; p<0.0001) and had more cardiovascular comorbidities (1.35 vs. 1.97; p=0.01). Systemic arterial hypertension was the strongest unique risk factor for mortality, present in 71% decedents vs. 45% of survivors, and the only independent risk factor in multivariate logistic regression analysis (OR 2.94, 95% CI 1.28–6.73). Moreover, there was a trend towards a higher incidence of diabetes and coronary artery disease in the group of non-survivors (Table 1). The number of new diagnoses of PH decreased during the pandemic compared to 2019 (new diagnoses rate in 2019 was 28.2/month vs. 19.2/month during COVID). A significant increase in total mortality was also observed in the PH group (11.1/month in 2019 vs. 13.7/month during COVID). Escalation of specific PH therapy also reduced (rate of specific therapy escalation in 2019 was 30.4/month vs. 20.5/month during COVID).

Conclusions

The COVID-19 pandemic has deeply affected the care of patients with pulmonary hypertension by reducing the number of new diagnoses, escalation of therapy, and increasing overall mortality in this population, and this impact continues into second year of pandemics. Pulmonary hypertension is associated with a more severe course and higher mortality in COVID-19.

Funding Acknowledgement

Type of funding sources: None.

Change of myocardial fluorodeoxyglucose uptake distribution after specific therapy of pulmonary arterial hypertension patients

Background

Right ventricular (RV) function is a major determinant of survival in patients with pulmonary arterial hypertension (PAH). In our previous study, we confirmed that increased RV fluorodeoxyglucose (FDG) uptake in positron emission tomography (PET) (presented as higher ratio of FDG uptake of RV to LV) was associated with progressive RV dysfunction and preceded hemodynamic and clinical deterioration in PAH patients. Now, we obtained second PET/MRI assessments of the study group after 2-years of PAH-targeted treatment.

Aim

The aim of the study was to obtain change of cardiac FDG uptake in PAH patients after follow-up period and to indicate factors mainly affecting this change.

Methods

Twenty-eight PAH patients (51.32±15.91 years) had simultaneous PET/MRI scans performed during baseline visit. FDG was used and its uptake was quantified as mean standardized uptake value (SUV) for both left (LV) and RV. Second PET/MRI assessments were done after 2 years in the group of twenty patients (four deaths, four patients did not agree to perform additional scans).

Results

After follow-up period, we observed significant change of MRI-derived RV ejection fraction (45±10% to 51.2±12.7%, p=0.03), and improvement in hemodynamic parameters obtained from right heart catheterization (RHC) e.g. mean pulmonary artery pressure, mPAP (48.5±17.2 to 41.8±17.1 mmHg, p=0.01) and pulmonary vascular resistance, PVR (8.7±5.3 to 7.0±4.2 WU, p=0.04). Follow-up SUVRV/SUVLV ratio significantly correlated with follow-up RV hemodynamic parameters confirming relationship between RV function and cardiac metabolic alterations (Table 1). Interestingly, patients who had improvement in SUVRV/SUVLV (lower follow-up value than baseline, n=11) had significantly higher mPAP at baseline visit (58.9±18.7 vs 40.3±11.8 mmHg, p=0.02), suggesting that RV FDG accumulation in advanced PAH may decrease after the PAH-specific treatment in accordance with the degree of reduction in the pulmonary vascular resistance.

Conclusion

Impaired RV function is associated with increased glucose uptake of RV myocytes estimated by FDG PET in PAH patients. Targeted treatment may improve RV function and thus affect previously altered cardiac glucose uptake.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Polish National Science Centre

408 The relationship between right ventricle-arterial coupling and cardiac metabolism in pulmonary arterial hypertension - multimodal study

Background

Right ventricular (RV) function is a major determinant of survival in patients with pulmonary arterial hypertension (PAH). The concept of coupling mainly refers to the relationship between ventricular contractility and afterload. In advanced PAH, to maintain cardiac output, RV dilates and the uncoupling occurs with wall stress and increased metabolic demand. We previously confirmed that impaired RV function is associated with increased glucose uptake of RV myocytes estimated by PET, which marks patients with worse prognosis.

Purpose

Whether echocardiographic approach of coupling parameters in PAH patients has relationship with RV metabolic alterations.

Methods

Twenty-six stable PAH patients (mean age 49.92 ± 15.94 years) and sixteen healthy subjects (control group) were enrolled into the study. The TAPSE, reflecting RV contractility, was obtained by mono-dimensional echo in standard technique. The echo estimation of the sPAP was reflecting RV afterload. Ventricular-arterial coupling was evaluated by the ratio between those two parameters. All PAH patients had also right heart catheterization (RHC) and PET performed during baseline visit. Heart glucose metabolism was assessed with fluorodeoxyglucose (FDG) as a tracer in PET. Its uptake was quantified as mean standardized uptake value (SUV) for both left ventricle (LV) and RV. Mean follow-up time of this study was 16.6 ± 7.5 months and the clinical end-point (CEP) was defined as death or clinical deterioration.

Results

Most of enrolled patients were in the WHO functional Class III (61%, 16). There were significant correlations between echo-derived hemodynamic parameters and RHC-derived values e.g. emPAP vs mPAP (RHC), r = 0.86, p &lt; 0.001. Echo-estimated RV ventricular-arterial coupling parameter (TAPSE/sPAP) was 0.35 ± 0.20 in PAH group and 1.51 ± 0.22 in control group, p &lt; 0.001. Mean SUV RV/LV ratio was 1.03 ± 0.68 in PAH group and 0.19 ± 0.08 in controls, p &lt; 0.005.

Echo-derived TAPSE/sPAP significantly correlated with hemodynamic parameters from RHC – cardiac output and pulmonary vascular resistance. Interestingly, we also observed significant correlations of TAPSE/sPAP with glucose uptake in PET - SUV RV as well as with SUV RV/LV (r=-0.63, p = 0.0006; r=-0.50, p = 0.0009), confirming higher metabolic demand in uncoupled heart in case of PAH.

Furthermore, patients who reached CEP (n = 15, 57%) had a significantly lower TAPSE/esPAP ratio (0.29 ± 0.17 vs 0.43 ± 0.21, p = 0.04) and higher SUV RV/LV (1.39 ± 0.79 vs 0.55 ± 0.45, p = 0.01). ROC analysis revealed significant cut-off value of TAPSE/esPAP in predicting CEP (AUC 0.72 (95% CI 0.52-0.92), p = 0.03). Patients with TAPSE/esPAP lower than 0.25 mm/mmHg had worse prognosis, log-rank test, p = 0.001 (Figure 1).

Conclusions

Simple echocardiographic parameter reflecting RV coupling (TAPSE/esPAP) related to altered myocardium metabolism in PAH may predict outcome in patients with PAH.

Abstract 408 Figure 1

P4686Multimodal assessment of right ventricular-arterial coupling allows better prognostication in pulmonary arterial hypertension patients

Background

The concept of coupling mainly refers to the relationship between ventricular contractility and afterload. Together, strictly related parameters may provide a more accurate estimation of the RV performance status. Indexing RV function, assessed by CMR feature tracking analysis, with a pulmonary artery systolic pressure (PASP) obtained from right heart catheterization (RHC) allows estimation of ventricular-arterial coupling and could help in prognostic stratification of pulmonary arterial hypertension (PAH) patients.

Aim

To verify the prognostic value of multimodal approach to estimate RV ventricular-arterial coupling in PAH patients.

Methods

Twenty-six stable PAH patients (mean age 49.92±15.94 years) and twelve healthy subjects (control group, 44.75±13.51 years) were enrolled into the study. CMR feature tracking analysis of the RV was performed for generation of RV global longitudinal strain (RV GLS); RV ejection fraction was also obtained by CMR. Right heart catheterization was carried out only in the PAH group with a standard technique.RV- arterial coupling was evaluated by the ratio of RV GLS/PASP. Mean follow-up time of this study was 16.6±7.5 months and the clinical end-point (CEP) was defined as death or clinical deterioration.

Results

In study group, RV GLS significantly correlated with hemodynamic parameters from RHC – mean pulmonary artery pressure, mPAP (r=0.53, p=0.04) and pulmonary vascular resistance, PVR (r=0.57, p=0.002). Mean RV GLS/PASP ratio in PAH group was (−)0.24±0.15%/mmHg.

Patients who reached CEP (n=15) had a significantly higher RV GLS and RV GLS/PASP ratio (−13.3±7.9% vs −20.4±6.2%, p=0.01 and −0.15±0.09%/mmHg vs −0.36±0.19%/mmHg, p=0.005, respectively). However, ROC analysis revealed higher area under curve (AUC) of RV GLS/PASP in predicting CEP than of RV GLS alone (0.82 (95% CI 0.64–1) vs 0.77 (95% CI 0.58–0.96), p<0.0001). Interestingly, at univariate analysis only RV GLS/PASP (HR: 0.89; 95% CI: 0.79–1.08; p=0.03), together with mPAP were all significantly associated with CEP. Patients with RV GLS/PASP cut-off value (ROC analysis) higher than (−)0.29%/mmHg had worse prognosis, log-rank test, p=0.01 (Figure 1).

Figure 1

Conclusions

Combining CMR and hemodynamic measurements via catheterization offers the potential for more comprehensive assessment of pulmonary vascular load and right heart function, as required for evaluation of the hemodynamic state in patients with PAH.

Acknowledgement/Funding

This work was supported by National Center for Science in Poland [“Preludium” grant 2017/25/N/NZ5/02689 to R.K.]

On the interactions between antimuscarinic atropine and NMDA receptor antagonists in anticholinesterase-treated mice

Both organophosphate (OP) and carbamate pesticides may produce seizures and death commonly attributed to the inhibition of acetylcholinesterase (AChE) and subsequent excess of acetylcholine (ACh). The anticonvulsant and neuroprotective properties of N-methyl-D-aspartate (NMDA) receptor antagonists in animals encouraged us to investigate their effects on the toxic and convulsant properties of OP and carbamate pesticides. Adult Swiss mice were systemically injected with the OP pesticide, chlorfenvinphos (CVP), or the carbamate pesticide, methomyl (MET). Both CVP and MET induced dose-dependent seizure activity and death in mice. Pretreatment with the muscarinic antagonist, atropine (ATR), at a dose of 1.8 mg/kg did not prevent seizures but decreased the lethal effects of CVP and MET. Pretreatment with the NMDA antagonists, dizocilpine (MK-801) at a dose of 1 mg/kg or 3-((R,S)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) at a dose of 10 mg/kg, influenced neither MET-induced seizures nor CVP- or MET-induced death. However, both MK-801 and CPP blocked CVP-induced seizures. Concurrent administration of ATR and the NMDA antagonists prevented seizures produced by CVP, but not those produced by MET. Nevertheless, both MK801 and CPP coadministered with ATR markedly enhanced its antilethal effects in CVP- and MET-intoxicated mice. The antidotes had no influence upon brain AChE activities in mice treated with saline or CVP or MET. It seems that combined treatment with ATR and NMDA receptor antagonists might be of clinical relevance.

AMPA/kainate-related mechanisms contribute to convulsant and proconvulsant effects of 3-nitropropionic acid

The role of the glutamatergic system in the convulsant and proconvulsant action of a mitochondrial toxin, 3-nitropropionic acid, was studied in mice. The occurrence of 3-nitropropionic acid-induced seizures was inhibited by the alpha-amino-2,3-dihydro-5-methyl-3-oxo-isoxazole-propionate (AMPA)/kainate receptor antagonists, 6-nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione disodium (NBQX) and 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine HCI (GYKI 52466), with ED50 of 14.1 (7.9-25.2) and 7.2 (5.3-9.6) mg/kg, respectively. The N-methyl-D-aspartate (NMDA) receptor antagonists, dizocilpine (MK-801) and 3-(2-carboxypiperazine-4-yl)propenyl-1-phosphonic acid (CPPene), were ineffective. Moreover, 3-nitropropionic acid given in a subthreshold dose potently enhanced seizures generated by intracerebroventricular administration of AMPA and kainate, lowering their CD50 from 0.98 (0.83-1.17) and 0.73 (0.64-0.83) to 0.55 (0.45-0.66) (P<0.001) and 0.58 (0.51-0.65) (P<0.05) nmol, respectively. In contrast, NMDA action was not changed by 3-nitropropionic acid application. We conclude that AMPA/kainate-mediated events are involved in proconvulsive and convulsive effects of 3-nitropropionic acid.

Mitochondrial toxin 3-nitropropionic acid evokes seizures in mice

3-Nitropropionic acid, a potent inhibitor of succinate dehydrogenase which thus compromises cellular energy metabolism, evoked convulsions in mice in a dose-dependent manner. CD50 for clonic seizures was 158.5 (144.1-174.3) mg/kg. Tonic seizures were not observed. Broad-spectrum anticonvulsants, namely diazepam, phenobarbital and valproate, prevented the occurrence of 3-nitropropionic acid-induced seizures with ED50 of 4.9 (3.1-7.6), 33.1 (17.9-61.0) and 389.7 (351.2-432.3) mg/kg, respectively. Diphenylhydantoin-like drugs (diphenylhydantoin, and carbamazepine), anti-absence drugs (trimethadione and ethosuximide) and acetazolamide were ineffective. The characteristics of 3-nitropropionic acid-induced seizures resembled those of convulsions evoked by another mitochondrial toxin, aminooxyacetic acid.

Excitatory amino acid antagonists alleviate convulsive and toxic properties of lindane in mice

Pesticides acting at GABAA receptors may induce convulsions in man and animals, but the mechanisms responsible for their convulsant activity are not fully explained. The following excitatory amino acid antagonists were studied for their protective action in mice intoxicated with chlorinated hydrocarbon insecticide lindane (gamma-hexachlorocyclohexane): the competitive NMDA antagonist: 3-(2-carboxypiperazine-4-yl)propenyl-1- phosphonic acid (D-CPPene, 20 mg/kg), the non-competitive NMDA antagonist: dizocilpine (MK-801, 0.4 mg/kg), the glycine site antagonist of NMDA receptor: 2-phenyl-1,3-propane-diol dicarbamate (felbamate, 400 mg/kg) and the competitive AMPA antagonist: 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX, 100 mg/kg). Systemic administration of an antagonist prior to lindane resulted in a strong anticonvulsant effect. D-CPPene, MK-801 and NBQX produced a marked increase of CD50 values of lindane for clonic convulsions. All the antagonists protected animals against tonic convulsions. Toxicity of lindane was potently reduced, as assessed 2, 24 and 120 hr after administration of the pesticide. Our results demonstrate that excitatory amino acid antagonists reduce convulsant properties and toxicity of lindane, suggesting that excitatory amino acid neurotransmission may be involved in its central action.