Exercise Pulmonary Resistances Predict Long-Term Survival in Systemic Sclerosis

The prognostic relevance of exercise pulmonary hypertension in cardiac and pulmonary diseases

PURPOSE OF REVIEW

In this review, we provide an overview of the prognostic implications of exPH in patients with various common cardiac and pulmonary diseases.

RECENT FINDINGS

Exercise pulmonary hypertension (exPH) has been recently re-introduced in the current European Society of Cardiology/European Respiratory Society pulmonary hypertension guidelines. Accordingly, exPH is defined as a mean pulmonary arterial pressure (mPAP)/cardiac output ( CO ) slope greater than 3 mmHg/l/min. Key considerations for this re-introduction included increasing understanding on normal pulmonary hemodynamics during exercise and the broadly available evidence on the association of an abnormal mPAP/ CO slope with poor survival in the general population and in different disease entities.

SUMMARY

Exercise (patho-)physiology has opened a new field for clinical research facilitating recognition of cardiovascular and pulmonary vascular diseases in an early stage. Such early recognition with significant prognostic and possibly therapeutic relevance, but being undetectable at rest, makes exercise pulmonary hemodynamics particularly interesting for common diseases, such as valvular heart disease, left heart disease, and chronic pulmonary disease.

The Management of Mild Pulmonary Hypertension in Clinical Practice

The definition of pulmonary hypertension (PH) has been revised recently, with the mean pulmonary artery pressure (mPAP) threshold (assessed by right heart catheterization) reduced from ⩾25 mm Hg to >20 mm Hg. This change reflects the mPAP upper limit of normal and a lower limit that is independently associated with adverse outcomes. To improve the specificity of diagnosing pathogenic increases in mPAP, however, a diagnosis of precapillary PH now also includes pulmonary vascular resistance >2.0 Wood units (WU) (lowered from >3.0 WU). These changes are positioned to capture approximately 55% more patients with PH. Because all clinical trials showing a benefit of pulmonary vasodilator therapy in precapillary PH used the classical hemodynamic definition, the approach to the diagnosis and management of patients with mild PH (i.e., mPAP 21-24 mm Hg and pulmonary vascular resistance 2-3 WU) requires particular consideration. Here, we use a question/answer format to discuss key areas in the management of mild PH, including practical information tailored to clinicians without training in PH.

Pulmonary Hypertension Associated with Connective Tissue Disease

Pulmonary hypertension (PH), a syndrome characterized by elevated pulmonary pressures, commonly complicates connective tissue disease (CTD) and is associated with increased morbidity and mortality. The incidence of PH varies widely between CTDs; patients with systemic sclerosis are most likely to develop PH. Several different types of PH can present in CTD, including PH related to left heart disease and respiratory disease. Importantly, CTD patients are at risk for developing pulmonary arterial hypertension, a rare form of PH that is associated with high morbidity and mortality. Future therapies targeting pulmonary vascular remodeling may improve outcomes for patients with this devastating disease.

Exercise Hemodynamics Predict Pulmonary Arterial Hypertension in BMPR2 Mutation Carriers

BACKGROUND

Exercise hemodynamics are recommended for early detection of pulmonary arterial hypertension (PAH) and have been suggested to be predictive of future development of PAH in high-risk populations such as BMPR2 mutation carriers. However, the optimal exercise hemodynamic screening parameter remains to be determined. Recent data suggest that pulmonary vascular distensibility coefficient (α) may serve as a useful parameter for early detection of PAH.

RESEARCH QUESTION

What is the value of exercise hemodynamics, including α, for predicting the occurrence of PAH during long-term follow-up in BMPR2 mutation carriers?

STUDY DESIGN AND METHODS

Fifty-two asymptomatic BMPR2 mutation carriers who underwent symptom-limited exercise hemodynamic assessment were followed up for a median of 10 years. The impact of hemodynamics at rest and exercise, presence of exercise pulmonary hypertension, and α on occurrence of PAH during long-term follow-up were assessed.

RESULTS

During long-term follow-up, five patients demonstrated PAH. Patients who demonstrated PAH showed a significantly lower α (0.8 ± 0.4%/mm Hg) than patients without PAH (1.8 ± 0.8%/mm Hg; P = .008). The only hemodynamic parameter that predicted the occurrence of PAH during long-term follow-up at regression analysis was α. Receiver operating characteristic analysis showed that α ≤ 1.5%/mm Hg predicted PAH occurrence with a specificity of 75% and sensitivity of 100%.

INTERPRETATION

Before development of PAH in BMPR2 mutation carriers, α is reduced markedly and may serve as a useful parameter in the setting of early disease detection. Given the low event rate, caution is warranted in interpreting these results, highlighting the need for validation studies.

Exercise pulmonary hypertension in patients with systemic sclerosis based on updated guidelines

Recent European guidelines have introduced the concept of exercise pulmonary hypertension (ex-PH). However, the clinical characteristics of ex-PH in systemic sclerosis (SSc) remains unknown. We aimed to investigate the characteristics of exercise pulmonary hypertension (ex-PH) in patients with systemic sclerosis (SSc), which are unknown. We retrospectively examined 77 patients with SSc who underwent symptom-limited exercise testing using a cycle ergometer with right heart catheterization at our hospital. Nineteen patients with postcapillary PH were excluded. Fifty-eight patients (median age, 63 years; 55 women) were divided into the overt-PH (n = 18, mean pulmonary arterial pressure [PAP] > 20 mmHg and pulmonary vascular resistance > 2 Wood units at rest), ex-PH (n = 19, mean PAP/cardiac output slope > 3), and non-PH (n = 21) groups. Exercise tolerance and echocardiography results were compared among the groups. Peak oxygen consumption was high in the non-PH group, intermediate in the ex-PH group, and low in the overt-PH group (14.5 vs. 13.0 vs. 12.5 mL/kg/min, p = 0.043), and the minute ventilation/peak carbon dioxide production slope was also intermediate in the ex-PH group (32.2 vs. 32.4 vs. 43.0, p = 0.003). The tricuspid annular plane systolic excursion/systolic PAP ratio decreased from non-PH to ex-PH to overt-PH (0.73 vs. 0.69 vs. 0.55 mm/mmHg, p = 0.018). In patients with SSc, exercise PH may represent an intermediate condition between not having PH and overt PH, according to the new guidelines.

Updated Hemodynamic Definition and Classification of Pulmonary Hypertension

Pulmonary hypertension (PH) is a pathophysiological manifestation of a heterogeneous group of diseases characterized by abnormally elevated pulmonary arterial pressures diagnosed on right heart catheterization. The 2022 European Society of Cardiology (ESC) and European Respiratory Society (ERS) Guidelines for the diagnosis and treatment of PH provides a new hemodynamic definition to define PH by lowering the threshold of the mean pulmonary artery pressure (mPAP) to 20 mm Hg. Precapillary PH is thus now defined as a mPAP >20 mm Hg together with a normal pulmonary artery wedge pressure (<15 mm Hg) and an increased pulmonary vascular resistance (>2 Wood Units). The ESC/ERS 2022 Guidelines also introduce a revised clinical classification of PH while retaining its previous distinction between the five groups according to the underlying pathophysiology.

[Diagnostic Algorithm and Screening of Pulmonary Hypertension]

The new guidelines for the diagnosis and treatment of pulmonary hypertension include a new diagnostic algorithm and provide specific recommendations for the required diagnostic procedures, including screening methods. These recommendations are commented on by national experts under the auspices of the DACH. These comments provide additional decision support and background information, serving as a further guide for the complex diagnosis of pulmonary hypertension.

[New definition and classification of pulmonary hypertension]

In the recent ESC/ERS guidelines on the diagnosis and management of pulmonary hypertension (PH) several important changes have been made in respect of the definition and classification of PH.The mPAP cut-off for defining PH was lowered. PH is now defined by an mPAP > 20 mmHg assessed by right heart catheterization. Moreover, the PVR threshold for defining precapillary PH was lowered. Precapillary PH is now defined by a PVR > 2 WU and a pulmonary arterial wedge pressure (PAWP) ≤ 15 mmHg. Furthermore, the increasing evidence for the clinical relevance of pulmonary exercise hemodynamics led to the reintroduction of exercise pulmonary hypertension (EPH) 1. EPH is characterized by a mPAP/CO-slope > 3 mmHg/L/min during exercise testing. In the classification of PH five groups are distinguished: Pulmonary arterial hypertension (group 1), PH associated with left heart disease (group 2), PH associated with lung diseases and/or hypoxia (Group 3), PH associated with pulmonary artery obstructions (group 4) and PH with unclear and/or multi-factorial mechanisms (group 5).In the following guideline-translation we focus on novel aspects regarding the definition and classification of PH and to provide additional background information.

Pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare and progressive disease characterised by remodelling of the pulmonary arteries and progressive narrowing of the pulmonary vasculature. This leads to a progressive increase in pulmonary vascular resistance and pulmonary arterial pressure and, if left untreated, to right ventricular failure and death. A correct diagnosis requires a complete work-up including right heart catheterisation performed in a specialised centre. Although our knowledge of the epidemiology, pathology and pathophysiology of the disease, as well as the development of innovative therapies, has progressed in recent decades, PAH remains a serious clinical condition. Current treatments for the disease target the three specific pathways of endothelial dysfunction that characterise PAH: the endothelin, nitric oxide and prostacyclin pathways. The current treatment algorithm is based on the assessment of severity using a multiparametric risk stratification approach at the time of diagnosis (baseline) and at regular follow-up visits. It recommends the initiation of combination therapy in PAH patients without cardiopulmonary comorbidities. The choice of therapy (dual or triple) depends on the initial severity of the condition. The main treatment goal is to achieve low-risk status. Further escalation of treatment is required if low-risk status is not achieved at subsequent follow-up assessments. In the most severe patients, who are already on maximal medical therapy, lung transplantation may be indicated. Recent advances in understanding the pathophysiology of the disease have led to the development of promising emerging therapies targeting dysfunctional pathways beyond endothelial dysfunction, including the TGF-β and PDGF pathways.

Role of Exercise Stress Echocardiography in Pulmonary Hypertension

Resting and exercise right heart catheterisation is the gold standard method to diagnose and differentiate types of pulmonary hypertension (PH). As it carries technical challenges, the question arises if non-invasive exercise stress echocardiography may be used as an alternative. Exercise echocardiography can unmask exercise PH, detect the early stages of left ventricular diastolic dysfunction, and, therefore, differentiate between pre- and post-capillary PH. Regardless of the underlying aetiology, a developed PH is associated with increased mortality. Parameters of overt right ventricle (RV) dysfunction, including RV dilation, reduced RV ejection fraction, and elevated right-sided filling pressures, are detectable with resting echocardiography and are associated with worse outcome. However, these measures all fail to identify occult RV dysfunction. Echocardiographic measures of RV contractile reserve during exercise echocardiography are very promising and provide incremental prognostic information on clinical outcome. In this paper, we review pulmonary haemodynamic response to exercise, briefly describe the modalities for assessing pulmonary haemodynamics, and discuss in depth the contemporary key clinical application of exercise stress echocardiography in patients with PH.

Updated definition of exercise pulmonary hypertension

In the recently published European Society of Cardiology/European Respiratory Society guidelines on the diagnosis and treatment of pulmonary hypertension (PH) the haemodynamic definitions of PH were updated and a new definition for exercise PH was introduced. Accordingly, exercise PH is characterised by a mean pulmonary arterial pressure/cardiac output (CO) slope >3 Wood units (WU) from rest to exercise. This threshold is supported by several studies demonstrating prognostic and diagnostic relevance of exercise haemodynamics in various patient cohorts. From a differential diagnostic point of view, an elevated pulmonary arterial wedge pressure/CO slope >2 WU may be suitable to identify post-capillary causes of exercise PH. Right heart catheterisation remains the gold standard to assess pulmonary haemodynamics both at rest and exercise. In this review, we discuss the evidence that led to the reintroduction of exercise PH in the PH definitions.

Abnormal pulmonary hemodynamics during exercise is associated with exercise capacity in COPD

BACKGROUND

Pulmonary hypertension (PH) is a frequent complication in COPD and it is associated with decreased exercise capacity and poor prognosis. We hypothesized that even in COPD patients without significant PH at rest, abnormal pulmonary hemodynamics during exercise affect exercise capacity.

METHODS

Consecutive COPD patients with clinically indicated right heart catheterization and resting mean pulmonary arterial pressure (mPAP) < 25 mmHg and age- and sex-matched controls with the same limits of pulmonary hemodynamics but no chronic lung disease who underwent clinical work-up including invasive hemodynamic assessment during exercise, were retrospectively analyzed. Chi-square tests were used to evaluate differences between groups for categorical data and Fisher's exact test or Mann-Whitney-U-tests for continuous variables. Associations were analyzed with Spearman rank correlation tests.

RESULTS

We included n = 26 COPD patients (female/male: 16/10, 66 ± 11 yr, FEV₁: 56 ± 25%predicted) and n = 26 matched controls (FEV₁: 96 ± 22%predicted). At rest, COPD patients presented with slightly increased mPAP (21 (18-23) vs. 17 (14-20) mmHg, p = 0.022), and pulmonary vascular resistance (PVR) [2.5 (1.9-3.0) vs. 1.9 (1.5-2.4) WU, p = 0.020] as compared to controls. During exercise, COPD patients reached significantly higher mPAP [47 (40-52) vs. 38 (32-44) mmHg, p = 0.015] and PVR [3.1 (2.2-3.7) vs. 1.7 (1.1-2.9) WU, p = 0.028] values despite lower peak exercise level [50 (50-75) vs. 100 (75-125) Watt, p = 0.002]. The mPAP/cardiac output slope was increased in COPD vs. controls [6.9 (5.5-10.9) vs. 3.7 (2.4-7.4) mmHg/L/min, p = 0.007] and negatively correlated with both peak oxygen uptake (r = - 0.46, p = 0.007) and 6-min walk distance (r = - 0.46, p = 0.001).

CONCLUSION

Even in the absence of significant PH at rest, COPD patients reveal characteristic abnormalities in pulmonary hemodynamics during exercise, which may represent an important exercise-limiting factor.

[Invasive Cardiopulmonary Exercise Testing: A Review]

Right heart catheterization (RHC) is the internationally standardized reference method for measuring pulmonary hemodynamics under resting conditions. In recent years, increasing efforts have been made to establish the reliable assessment of exercise hemodynamics as well, in order to obtain additional diagnostic and prognostic data. Furthermore, cardiopulmonary exercise testing (CPET), as the most comprehensive non-invasive exercise test, is increasingly performed in combination with RHC providing detailed pathophysiological insights into the exercise response, so-called invasive cardiopulmonary exercise testing (iCPET).In this review, the accumulated experience with iCPET is presented and methodological details are discussed. This complex examination is especially helpful in differentiating the underlying causes of unexplained dyspnea. In particular, early forms of cardiac or pulmonary vascular dysfunction can be detected by integrated analysis of hemodynamic as well as ventilatory and gas exchange data. It is expected that with increasing validation of iCPET parameters, a more reliable differentiation of normal from pathological stress reactions will be possible.

Pulmonary Hypertension Associated with Connective Tissue Disease

Pulmonary hypertension (PH), a syndrome characterized by elevated pulmonary pressures, commonly complicates connective tissue disease (CTD) and is associated with increased morbidity and mortality. The incidence of PH varies widely between CTDs; patients with systemic sclerosis are most likely to develop PH. Several different types of PH can present in CTD, including PH related to left heart disease and respiratory disease. Importantly, CTD patients are at risk for developing pulmonary arterial hypertension, a rare form of PH that is associated with high morbidity and mortality. Future therapies targeting pulmonary vascular remodeling may improve outcomes for patients with this devastating disease.

Pulmonary hypertension phenotypes in patients with systemic sclerosis

Pulmonary hypertension (PH) commonly affects patients with systemic sclerosis (SSc) and is associated with significant morbidity and increased mortality. PH is a heterogenous condition and several different forms can be associated with SSc, including pulmonary arterial hypertension (PAH) resulting from a pulmonary arterial vasculopathy, PH due to left heart disease and PH due to interstitial lung disease. The incidence of pulmonary veno-occlusive disease is also increased. Accurate and early diagnosis to allow optimal treatment is, therefore, essential. Recent changes to diagnostic haemodynamic criteria at the 6th World Symposium on Pulmonary Hypertension have resulted in therapeutic uncertainty regarding patients with borderline pulmonary haemodynamics. Furthermore, the optimal pulmonary vascular resistance threshold for diagnosing PAH and the role of exercise in identifying early disease require further elucidation. In this article we review the epidemiology, diagnosis, outcomes and treatment of the spectrum of pulmonary vascular phenotypes associated with SSc.

Assessment of right ventricular reserve utilizing exercise provocation in systemic sclerosis

Right ventricular (RV) capacity to adapt to increased afterload is the main determinant of outcome in pulmonary hypertension, a common morbidity seen in systemic sclerosis (SSc). We hypothesized that supine bicycle echocardiography (SBE), coupled with RV longitudinal systolic strain (RVLSS), improves detection of limitations in RV reserve in SSc. 56 SSc patients were prospectively studied during SBE with RV functional parameters compared at rest and peak stress. We further dichotomized patients based on resting RV systolic pressure (RVSP) to determine the effects of load on contractile response. Our pooled cohort analysis revealed reduced global RVLSS at rest (-16.2 ± 3.9%) with normal basal contractility (-25.6 ± 7.7%) and relative hypokinesis of the midventricular (-14.1 ± 6.0%) and apical (-8.9 ± 5.1%) segments. With exercise, global RVLSS increased significantly (p = 0.0005), however despite normal basal contractility at rest, there was no further augmentation with exercise. Mid and apical RVLSS increased with exercise suggestive of RV contractile reserve. In patients with resting RVSP < 35 mmHg, global and segmental RVLSS increased with exercise. In patients with resting RVSP ≥ 35 mmHg, global and segmental RVLSS did not increase with exercise and there was evidence of exertional RV dilation. Exercise provocation in conjunction with RVLSS identified differential regional contractile response to exercise in SSc patients. We further demonstrate the effect of increased loading conditions on RV contractile response exercise. These findings suggest subclinical impairments in RV reserve in SSc that may be missed by resting noninvasive 2DE-based assessments alone.