Role of Vasodilator Testing in Pulmonary Hypertension

Inhaled nitric oxide testing in predicting prognosis in pulmonary hypertension due to left-sided heart diseases

AIMS

The pathophysiology of pulmonary hypertension (PH) due to left-sided heart disease (Group 2 PH) is distinct from that of other groups of PH, yet there are still no approved therapies that selectively target pulmonary circulation. The increase in pulmonary capillary pressure due to left-sided heart disease is a trigger event for physical and biological alterations of the pulmonary circulation, including the nitric oxide (NO)-soluble guanylate cyclase-cyclic guanosine monophosphate axis. This study investigated inhaled NO vasoreactivity tests for patients with Group 2 PH and hypothesized that these changes may have a prognostic impact.

METHODS AND RESULTS

This was a single-centre, retrospective study with a median follow-up of 365 days. From January 2011 to December 2015, we studied 69 patients with Group 2 PH [age, 61.5 ± 13.0 (standard deviation) years; male:female, 49:20; left ventricular ejection fraction, 50.1 ± 20.4%; mean pulmonary arterial pressure, ≥25 mmHg; and pulmonary arterial wedge pressure (PAWP), >15 mmHg]. No adverse events were observed after NO inhalation. Thirty-four patients with Group 2 PH showed increased PAWP (ΔPAWP: 3.26 ± 2.22 mmHg), while the remaining 35 patients did not (ΔPAWP: -2.11 ± 2.29 mmHg). Multivariate analysis revealed that increased PAWP was the only significant predictor of all-cause death or hospitalization for heart failure (HF) after 1 year (hazard ratio 4.35; 95% confidence interval, 1.27-14.83; P = 0.019). The acute response of PAWP to NO differed between HF with preserved and reduced ejection fractions.

CONCLUSIONS

Patients with Group 2 PH were tolerant of the inhaled NO test. NO-induced PAWP is a novel prognostic indicator.

Comparison of intravenous sildenafil with inhaled nitric oxide for acute vasodilator testing in pulmonary arterial hypertension

Acute vasodilator testing (AVT) identifies acute responders for initiation of calcium channel blockers in pulmonary arterial hypertension (PAH) and operability in congenital heart disease (CHD). We sought to determine the feasibility of intravenous sildenafil (ivS) as an alternative to inhaled nitric oxide (iNO) in AVT. All patients with PAH undergoing cardiac catheterization for AVT (November 2015 to December 2020) were prospectively enrolled. Hemodynamic data were obtained at baseline, with iNO 20 ppm and ivS (0.25 mg/kg for children and 10 mg for adults). We studied 44 patients with a mean age of 20.5 ± 14.4 years (27 [61%] females and 20 [45%] children). There were 17 (38.6%) patients in the CHD group for operability assessment and 27 patients in non-CHD group (idiopathic pulmonary arterial hypertension-16 [36.3%], residual PAH after shunt closure-7 [15.9%], and 2 cases [4.5%] each of familial PAH and portopulmonary hypertension). There was an excellent intraclass correlation for mean pulmonary artery pressures (0.903, 95% confidence interval, CI: 0.809-0.949, p < 0.001), mean aortic pressures (0.745, 95% CI: 0.552-0.858, p < 0.001), pulmonary vascular resistance index (0.920, 95% CI: 0.858-0.956, p < 0.001), systemic vascular resistance (SVR) index (0.828, 95% CI: 0.706-0.902, p < 0.001), and the ratio of pulmonary and SVR indices (0.857, 95% CI: 0.752-0.919, p < 0.001) between the two agents. There were two responders, both in non-CHD group, and were identified by iNO and ivS. The hemodynamic effects of ivS show excellent correlation with iNO and could be a potential alternative agent for identifying acute responders during AVT.

Recent Advances and Future Prospects of Treatment of Pulmonary Hypertension

Pulmonary hypertension is one of the difficult situations to treat. Complex pathophysiology, association of the multiple comorbidities make clinical scenario challenging. Recently it is being shown that patients who had recovered from coronavirus disease infection, are at risk of developing pulmonary hypertension. Studies on animals have been going on to find out newer treatment options. There are recent advancements in the treatment of pulmonary hypertension. Role of anticoagulation, recombinant fusion proteins, stem cell therapy are emerging as therapeutic options for affected patients. SGLT2 inhibitors have potential to have beneficial effects on pulmonary hypertension. Apart from the medical managements, advanced interventions are also getting popular. In this review article, the authors have discussed pathophysiology, recent advancement of treatments including coronavirus disease patients, and future aspect of managing pulmonary hypertension. We have highlighted treatment options for patients with sleep apnea, interstitial lung disease to discuss the challenges and possible options to manage those patients.

Comparative Analysis of Metabolic Differences of Jersey Cattle in Different High-Altitude Areas

In high-altitude area, hypoxia is a serious stress for humans and other animals, disrupting oxygen homeostasis and thus affecting tissue metabolism. Up to now, there are few reports on the metabolic changes of dairy cows at different altitudes. In this experiment, metabonomics technology and blood biochemical indexes were used to study the metabolic changes of dairy cows in different altitudes. The results showed that the different metabolites were mainly enriched in amino acid metabolism and sphingolipid metabolism, and sphingolipid metabolism showed a negative correlation with increased altitude. The results of this study will enrich the hypoxia-adaptive mechanism of dairy cows in high-altitude areas and provide a theoretical basis for the nutritional regulation of performance and disease treatment of dairy cows in high-altitude areas.

Under Pressure: Right Heart Catheterization and Provocative Testing for Diagnosing Pulmonary Hypertension

Pulmonary hypertension (PH) is a heterogenous disorder involving multiple pathophysiological processes that ultimately affect the vasculature within the lungs. Right heart catheterization (RHC) continues to be the benchmark for diagnosing PH. The use of provocation techniques during RHC can help sub-characterize the type of PH and thus assist in developing appropriate treatment strategies for the management of each PH subtype. This review examines proven and novel approaches for evaluating the pulmonary vasculature during RHC and aspires to provide an accurate, clinically relevant framework for using RHC to diagnose and manage PH. Further improvement in standardized protocols will help optimize the application of RHC in patients with PH.

Comparison of levosimendan, NO, and inhaled iloprost for pulmonary hypertension reversibility assessment in heart transplant candidates

Aims

Assessing reversibility of pulmonary vascular changes through vasoreactivity testing (VRT) optimizes end‐stage heart failure patient selection for heart transplant. All efforts should be made to unload the left ventricle and reduce pulmonary vascular resistance to effectively exclude irreversible pulmonary hypertension.

Methods and results

We reviewed our centre's cardiac transplant registry database (2009–2017) for VRT and compared haemodynamic responses with 40 ppm inhaled NO (n = 14), 14–17 μg inhaled iloprost (n = 7), and 24 h 0.1 μg/kg/min intravenous levosimendan (n = 14). Response to levosimendan was assessed by repeat right heart catheterization within 72 h. Baseline clinical and haemodynamic features were similar between groups. VRT was well tolerated in all patients. All drugs effectively reduced pulmonary artery pressures and transpulmonary gradient while increasing cardiac index, although levosimendan had a greater impact on cardiac index increase (P = 0.036). Levosimendan was the only drug that reduced pulmonary artery wedge pressure (P = 0.004) and central venous pressures (P < 0.001) and increased both left and right ventricular stroke work indexes (P = 0.020 and P = 0.042, respectively) and cardiac power index (P < 0.001) compared with NO and iloprost. Right ventricular end‐diastolic pressures and central venous pressure were only decreased by levosimendan. The rate of positive responses (≥10 mmHg decrease or final mean pulmonary artery pressure ≤40 mmHg with increased/unaltered cardiac index) was lower with inhaled iloprost (14%) than with either levosimendan or NO (71% and 64%, respectively; P < 0.05).

Conclusions

Levosimendan may be a safe and effective alternative for pulmonary hypertension reversibility assessment or a valuable pre‐test medical optimization tool in end‐stage heart failure patient assessment for heart transplantation offering extended haemodynamic benefits. Whether it increases the rate of positive responses or allows a better selection of candidates to heart transplantation remains to be established.

Assessing pulmonary circulation in severe bronchopulmonary dysplasia using functional echocardiography

Pulmonary hypertension (PH) is common in infants with severe bronchopulmonary dysplasia (BPD) and increases the risk of death. The objectives of this preliminary study were to compare responses of pulmonary circulation parameters to 100% oxygen (O₂) and inhaled nitric oxide (iNO) in infants with BPD and PH using echocardiography. Responses between fetal growth restriction (FGR) and appropriate for gestational age infants were compared. Ten infants <28 weeks GA at birth were assessed at ≥36 weeks corrected gestation. Baseline echocardiography1 was performed which was repeated (echocardiography2) after 30 minutes of O₂. After a gap of 2–3 hours, iNO was administered for 15 minutes and echocardiography3 was performed, followed by iNO weaning. The gestation and birthweight of the cohort were 25.9 ± 1.6 weeks and 612 ± 175 g. Assessments were performed at 38.7 ± 1.4 weeks corrected gestational age. Baseline time to peak velocity: right ventricular ejection time (TPV/RVETc) increased from 0.24 ± 0.02 to 0.27 ± 0.02 (O₂, p = .01) and 0.31 ± 0.03 (iNO, p < .001), indicating a decrease in pulmonary vascular resistance [PVR]. Baseline tricuspid annular plane systolic excursion (TAPSE) increased from 8.1 ± 0.6 mm to 9.3 ± 0.7 mm (O₂, p = .01) and 10.5 ± 1.1 mm (iNO, p = .0004), indicating improved ventricular systolic performance. Percentage change for all parameters was greater with iNO. Significant correlations between cardiac performance and PVR were noted. FGR infants noted higher baseline PVR (TPV/RVETc, 0.21 ± 0.02 vs. 0.25 ± 0.01, p = .002), lower ventricular performance (TAPSE, 7 ± 1.2 mm vs. 8.6 ± 6 mm, p = .003), and lower percentage change with O₂ and iNO. A reactive component of pulmonary circulation provides real‐time physiological information, which could rationalize treatment decisions.

Sex differences of hemodynamics during acute vasoreactivity testing to predict the outcomes of chronic thromboembolic pulmonary hypertension

BACKGROUND

Acute vasoreactivity testing (AVT) which reflects the compliance of the pulmonary vascular bed has been proven to be of prognostic value. The purpose of the present study is to explore the sex differences of hemodynamics during the AVT and their impact on event-free survival in patients with chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS

Eighty-six patients underwent a right heart catheterization and AVT at Shanghai Pulmonary Hospital from February 2009 to February 2018. Univariate and multiple stepwise regression analysis were performed to determine the predictors of independent event-free survival, and receiver operating characteristic curve was plotted to determine the cut-off value of independent parameters in CTEPH.

RESULTS

There were no significant differences in both demographics and hemodynamics between male and female patients with CTEPH. Except ΔPVR/PVR showed a significantly higher difference in female than male patients (P = 0.034). Male patients had higher mRAP of pre- and post-AVT than female patients in the event-free subgroup, while, female patients showed higher PVR of pre-AVT than male patients in the event subgroup (P < 0.05). The mRAP and SvO₂ were independent predictors of event-free survival in female patients both before and after the AVT, whereas ΔSvO₂ was an independent predictor of event-free survival in male patients.

CONCLUSION

Hemodynamics during the AVT varied between male and female patients with CTEPH. Both sexes displayed unique hemodynamic responses that were independently able to predict event-free survival. Therefore, better estimates of prognosis in CTEPH can be made when sex differences are also taken into consideration.

Acute Vasoreactivity Testing during Cardiac Catheterization of Neonates with Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension

OBJECTIVES

To assess whether better baseline pulmonary hemodynamics or positive acute vasoreactivity testing (AVT) during cardiac catheterization are associated with improved outcomes in infants with bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH).

STUDY DESIGN

This retrospective, single-center study included 26 premature neonates with BPD who underwent catheterization to evaluate PH. AVT was assessed with exposure to 100% fractional inspired oxygen with or without inhaled nitric oxide. AVT was positive if the patient met the Barst criteria or increased shunt volume and decreased pulmonary vascular resistance index by >50%.

RESULTS

At baseline, the median pulmonary artery mean pressure was 29 mm Hg (IQR, 24-35) and the pulmonary vascular resistance index was 5.3 units*m² (IQR, 3.5-6.9). Nine patients (35%) had a positive AVT response, which was associated with a decreased risk of death or tracheostomy by 2-year follow-up (hazard ratio, 0.15; P = .02). Baseline pulmonary hemodynamics and the presence of left ventricular diastolic dysfunction were not associated with late outcomes in this cohort.

CONCLUSIONS

We found that 35% of infants with BPD who underwent catheterization had positive AVT and that a positive response was associated with better long-term outcomes than nonresponders. AVT better distinguishes higher from lower risk PH in infants with BPD than baseline pulmonary hemodynamics. AVT may aid in the assessment of disease severity and management of BPD-associated PH.

Stressing the Cardiopulmonary Vascular System: The Role of Echocardiography

The cardiopulmonary vascular system represents a key determinant of prognosis in several cardiorespiratory diseases. Although right heart catheterization is considered the gold standard for assessing pulmonary hemodynamics, a comprehensive noninvasive evaluation including left and right ventricular reserve and function and cardiopulmonary interactions remains highly attractive. Stress echocardiography is crucial in the evaluation of many cardiac conditions, typically coronary artery disease but also heart failure and valvular heart disease. In stress echocardiographic applications beyond coronary artery disease, the assessment of the cardiopulmonary vascular system is a cornerstone. The possibility of coupling the left and right ventricles with the pulmonary circuit during stress can provide significant insight into cardiopulmonary physiology in healthy and diseased subjects, can support the diagnosis of the etiology of pulmonary hypertension and other conditions, and can offer valuable prognostic information. In this state-of-the-art document, the topic of stress echocardiography applied to the cardiopulmonary vascular system is thoroughly addressed, from pathophysiology to different stress modalities and echocardiographic parameters, from clinical applications to limitations and future directions.

Detection and removal of impurities in nitric oxide generated from air by pulsed electrical discharge

Inhalation of nitric oxide (NO) produces selective pulmonary vasodilation without dilating the systemic circulation. However, the current NO/N₂ cylinder delivery system is cumbersome and expensive. We developed a lightweight, portable, and economical device to generate NO from air by pulsed electrical discharge. The objective of this study was to investigate and optimize the purity and safety of NO generated by this device. By using low temperature streamer discharges in the plasma generator, we produced therapeutic levels of NO with very low levels of nitrogen dioxide (NO₂) and ozone. Despite the low temperature, spark generation eroded the surface of the electrodes, contaminating the gas stream with metal particles. During prolonged NO generation there was gradual loss of the iridium high-voltage tip (-90 μg/day) and the platinum-nickel ground electrode (-55 μg/day). Metal particles released from the electrodes were trapped by a high-efficiency particulate air (HEPA) filter. Quadrupole mass spectroscopy measurements of effluent gas during plasma NO generation showed that a single HEPA filter removed all of the metal particles. Mice were exposed to breathing 50 parts per million of electrically generated NO in air for 28 days with only a scavenger and no HEPA filter; the mice did not develop pulmonary inflammation or structural changes and iridium and platinum particles were not detected in the lungs of these mice. In conclusion, an electric plasma generator produced therapeutic levels of NO from air; scavenging and filtration effectively eliminated metallic impurities from the effluent gas.