Echocardiographic Screening Methods for Pulmonary Hypertension: A Practical Review

Germline and Somatic Mutations in DNA Methyltransferase 3A (DNMT3A) Predispose to Pulmonary Arterial Hypertension (PAH) in Humans and Mice: Implications for Associated PAH

Background

Mutations are found in 10-20% of idiopathic PAH (IPAH) patients, but none are consistently identified in connective tissue disease-associated PAH (APAH), which accounts for ∼45% of PAH cases. TET2 mutations, a cause of clonal hematopoiesis of indeterminant potential (CHIP), predispose to an inflammatory type of PAH. We now examine mutations in another CHIP gene, DNMT3A , in PAH.

Methods

We assessed DNMT3A mutation prevalence in PAH Biobank subjects as compared with controls, first using whole exome sequencing (WES)-derived CHIP calls in 1832 PAH Biobank patients versus 7509 age-and sex-matched gnomAD controls. We then performed deep, targeted panel sequencing of CHIP genes on a subset of 710 PAH Biobank patients and compared the prevalence of DNMT3A mutations therein to an independent pooled control cohort (N = 3645). In another cohort of 80 PAH patients and 41 controls, DNMT3A mRNA expression was studied in peripheral blood mononuclear cells (PBMCs). Finally, we evaluated the development of PAH in a conditional, hematopoietic, Dnmt3a knockout mouse model.

Results

DNMT3A mutations were more frequent in PAH cases versus control subjects in the WES dataset (OR 2.60, 95% CI: 1.71-4.27). Among PAH patients, 33 had DNMT3A variants, most of whom had APAH (21/33). While 21/33 had somatic mutations (female:male 17:4), germline variants occurred in 12/33 (female:male 11:1). Hemodynamics were comparable with and without DNMT3A mutations (mPAP=58±21 vs. 52±18 mmHg); however, patients with DNMT3A mutations were unresponsive to acute vasodilator testing. Targeted panel sequencing identified that 14.6% of PAH patients had CHIP mutations (104/710), with DNMT3A accounting for 49/104. There was a significant association between all CHIP mutations and PAH in analyses adjusted for age and sex (OR 1.40, 95% CI: 1.09-1.80), though DNMT3A CHIP alone was not significantly enriched (OR:1.15, 0.82-1.61). DNMT3A expression was reduced in patient-derived versus control PAH-PBMCs. Spontaneous PAH developed in Dnmt3a -/- mice, and it was exacerbated by 3 weeks of hypoxia. Dnmt3a -/- mice had increased lung macrophages and elevated plasma IL-13. The IL-1β antibody canakinumab attenuated PAH in Dnmt3a -/- mice.

Conclusions

Germline and acquired DNMT3A variants predispose to PAH in humans. DNMT3A mRNA expression is reduced in human PAH PBMCs. Hematopoietic depletion of Dnmt3a causes inflammatory PAH in mice. DNMT3A is a novel APAH gene and may be a biomarker and therapeutic target.

Hypercarbia and high-flow nasal oxygen use during anaesthesia - risking a failure to thrive?

Prevention of arterial oxygen desaturation during anaesthesia with high-flow nasal oxygen (HFNO) has gained greater acceptance for a widening range of procedures. However, during HFNO use there remains the potential for development of significant anaesthesia-associated apnoea or hypoventilation and the possibility of hypercarbia, with harmful cardiovascular or neurological sequelae. The aim of this study was to determine whether any HFNO-related hypercarbia adverse incidents had been reported on webAIRS, an online database of adverse anaesthesia-related incidents. Two relevant reports were identified of complications due to marked hypercarbia during HFNO use to maintain oxygenation. In both reports, HFNO and total intravenous anaesthesia were used during endoscopic procedures through the upper airway. In both, the extent of hypoventilation went undetected during HFNO use. An ensuing cardiac arrest was reported in one report, ascribed to acute hypercarbia-induced exacerbation of the patient's pre-existing pulmonary hypertension. In the other report, hypercarbia led to a prolonged duration of decreased level of consciousness post procedure, requiring ventilatory support. During the search, an additional 11 reports of postoperative hypercarbia-associated sedation were identified, unrelated to HFNO. In these additional reports an extended duration of severe acute hypercarbia led to sedation or loss of consciousness, consistent with the known effects of hypercarbia on consciousness. These 13 reports highlight the potential dangers of unrecognised and untreated hypercarbia, even if adequate oxygenation is maintained.

Therapeutic Approaches in Pulmonary Arterial Hypertension with Beneficial Effects on Right Ventricular Function-Preclinical Studies

Pulmonary hypertension (PH) is a progressive condition that affects the pulmonary vessels, but its main prognostic factor is the right ventricle (RV) function. Many mice/rat models are used for research in PAH, but results fail to translate to clinical trials. This study reviews studies that test interventions on pulmonary artery banding (PAB), a model of isolated RV disfunction, and PH models. Multiple tested drugs both improved pulmonary vascular hemodynamics in PH models and improved RV structure and function in PAB animals. PH models and PAB animals frequently exhibited similar results (73.1% concordance). Macitentan, sildenafil, and tadalafil improved most tested pathophysiological parameters in PH models, but almost none in PAB animals. Results are frequently not consistent with other studies, possibly due to the methodology, which greatly varied. Some research groups start treating the animals immediately, and others wait up to 4 weeks from model induction. Treatment duration and choice of anaesthetic are other important differences. This review shows that many drugs currently under research for PAH have a cardioprotective effect on animals that may translate to humans. However, a uniformization of methods may increase comparability between studies and, thus, improve translation to clinical trials.

The correlation in echocardiogram to right heart catheterization in identifying pulmonary hypertension as a barrier to liver transplantation

BACKGROUND

Pulmonary hypertension (PH) and portopulmonary hypertension (POPH) can be limitations towards listing for liver transplantation (LT). Our study evaluates the correlation of right ventricular systolic pressure (RVSP) and mean pulmonary artery pressure (mPAP) on transthoracic echocardiogram (TTE) compared to mPAP on right heart catheterization (RHC).

METHODS

We performed a retrospective review of 723 patients who underwent LT evaluation at our institution between 2012 and 2020. Our cohort consisted of patients with RVSP and mPAP measured on TTE. A Wald t-test and area under the curve analysis were used for statistical analyses.

RESULTS

Patients with higher mPAP values on TTE (N=33) did not correlate with mPAP ≥ 35 mmHg on RHC, while patients with higher RVSP values (N=147) on TTE were associated with mPAP ≥ 35 mmHg on RHC. The cutoff value of RVSP ≥ 48 mmHg on TTE was associated with mPAP ≥ 35 mmHg on RHC.

CONCLUSIONS

Our data suggest that RVSP compared to mPAP on TTE is a better indicator for mPAP ≥ 35 mmHg on RHC. RVSP can be used as a marker on echocardiography for identifying patients with a higher likelihood of PH being a barrier to LT listing.

Evaluating Signs of Pulmonary Hypertension on Computed Tomography and Correlating With Echocardiography: A Study at a Tertiary Care Hospital

Introduction: Pulmonary hypertension (PH) is a threatening condition, and it is far more common than previously assumed, especially after the COVID pandemic. Its outcome is not good; if detected late, and can lead to right ventricular failure, which can be fatal. Our goal was to evaluate CT signs of PH, correlate them with echocardiography, and identify the cut-off values of these signs in our population.

Method: In this study, 160 patients having both CT and echocardiography with a maximum gap of one month were assessed from June to November 2021. The association between CT signs and echocardiography to diagnose PH was investigated. The Pearson and Spearman correlation and area under receiver operating curve (AUROC) tests were performed in the analysis. Receiver operating characteristic curve analysis was also used to assess CT’s diagnostic capability and cut-off values.

Result: The correlation between main pulmonary artery (MPA) diameter and main pulmonary artery to aorta ratio (MPA/AO) with mean pulmonary artery pressure (mPAP) was weak but statistically significant (r = 0.316 and r = 0.321, p<0.001). However, there was a very weak correlation between the right and left pulmonary artery and mPAP with correlation coefficients (r) of 0.155 and 0.138, respectively. For the first time in our population, we measured the cut-off values of MPA and MPA/AO ratios for PH which were 26 and 0.88 mm, respectively.

Conclusions: The CT signs of PH correlate with echocardiography; however, should not be used solely; the cut-off values should be used according to race and population.

Mild pulmonary hypertension and premature mortality among 154 956 men and women undergoing routine echocardiography

Although mild pulmonary hypertension (PHT) is known to be associated with increased mortality, its impact on premature mortality is largely unknown.We studied the distribution of estimated right ventricular systolic pressures (eRVSP) among 154 956 adults with no evidence of left heart disease investigated with echocardiography. We then examined individually linked mortality, premature mortality and associated life-years lost (LYL) according to eRVSP levels.The cohort comprised 70 826 men (61.3±17.7 years) and 84 130 women (61.4±18.4 years). Overall, 85 173 (55.0%), 49 276 (31.8%), 13 060 (8.4%) and 7447 (4.8%) cases had an eRVSP level indicative of no (<30.0 mmHg), mild (30.0-39.9 mmHg), moderate (40.0-49.9 mmHg), or severe (≥50.0 mmHg) PHT, respectively. During median 5.7 (interquartile range 3.2-8.9) years follow-up, 38 456/154 986 (24.8%) individuals died. Compared to an eRVSP <30.0 mmHg, age and sex-adjusted hazard ratios for all-cause and cardiovascular-related mortality were 1.90 (95% CI 1.84-1.96) and 1.85 (95% CI 1.74-1.97) respectively, for an eRVSP of 35.0-39.9 mmHg. Overall, 6,256 (54%) men and 7524 (55%) women died prematurely. As a proportion of all deaths, premature mortality rose from 46.7% to 79.2% among those with an eRVSP <30.0 mmHg versus ≥60.0 mmHg with a mean of 5.1 to 11.4 LYL each time. However, due to more individuals affected overall, an eRVSP of 30.0-39.9 mmHg accounted for 58% and 53% of total LYL among men (40 606/70 019 LYL) and women (47 333/88 568 LYL), respectively.These data confirm that elevated eRVSP levels indicative of mild PHT are associated with increased risk of death. Moreover, this results in a substantive component of premature mortality/LYL that requires more proactive clinical surveillance and management.