P284 THE RIGHT HEART ADAPTATS TO EXERCISE MORE EFFICIENTLY IN PULMONARY ARTERIAL HYPERTENSION THAN IN PULMONARY HYPERTENSION DUE TO HEART FAILURE WITH PRESERVED EJECTION FRACTION

Background

Right heart failure (RHF) represents the final step of distinct diseases, differently involving the pulmonary circulation, such as pulmonary arterial hypertension (PAH) and pulmonary hypertension (PH) due to heart failure with preserved ejection fraction (HFpEF). Exercise may unmask right heart maladaptation as a sign of RHF, but cut–offs for right atrial pressure (RAP) rise during exercise remain to be defined. We hypothesized that PH–HFpEF may present with worse right heart adaptation to exercise than PAH due to increased chamber stiffness and dysfunctional preload.

Aim

We sought to describe the behavior of RAP during exercise in PAH and in PH–HFpEF, and the mechanisms underlying right heart maladaptation.

Methods

We performed a retrospective analysis of data (2007–2021) obtained from patients with either PAH or PH–HFpEF who underwent a right heart catheterization at rest and during exercise. Right heart adaptation to exercise was described using either absolute or cardiac output (CO)–normalized RAP increase during exercise (RAP/CO slope). Patients with non–cardiac dyspnea (NCD) served to define RAP limits of normality. Estimated stressed blood volume (eSBV), as a measure of effective preload, was computed based on hemodynamics using a commercially–available software.

Results

Ninety–four patients were included (32 PH–HFpEF, 32 PAH and 30 NCD). The upper limit of normal for absolute peak RAP and RAP/CO slope were 12 mmHg and 1.55 mmHg/L/min. Compared with PH–HFpEF, PAH patients showed higher systolic, diastolic and mean pulmonary artery pressure (PAP) as well as higher indices of right ventricular afterload both at rest and during exercise, but lower filling pressures and similar CO (Figure 1).In particular, PH–HFpEF had higher peak RAP and higher RAP/CO slope than PAH (Figure 1,2). Additionally, 78% and 91% of PH–HFpEF, as compared with 47% and 44% of PAH had a RAP/CO slope and a peak RAP above normal, respectively (p < 0.001). PH–HFpEF presented with higher increase in eSBV, and higher peak eSBV values than PAH (p < 0.05), despite similar resting levels. RAP/eSBV slope was upward shifted (at a given effective preload, RAP was higher) while CO/eSBV slope was flatter (at a given effective preload, CO was lower) in PH–HFpEF as compared with PAH (Figure 3).

Conclusions

PH–HFpEF display worse right heart maladaptation to exercise than PAH, likely due to a combination of increased right heart stiffness and a more exhausted Frank–Starling reserve.

Blood CD9+ B cell, a biomarker of bronchiolitis obliterans syndrome after lung transplantation

Bronchiolitis obliterans syndrome is the main limitation for long-term survival after lung transplantation. Some specific B cell populations are associated with long-term graft acceptance. We aimed to monitor the B cell profile during early development of bronchiolitis obliterans syndrome after lung transplantation. The B cell longitudinal profile was analyzed in peripheral blood mononuclear cells from patients with bronchiolitis obliterans syndrome and patients who remained stable over 3 years of follow-up. CD24^hi CD38^hi transitional B cells were increased in stable patients only, and reached a peak 24 months after transplantation, whereas they remained unchanged in patients who developed a bronchiolitis obliterans syndrome. These CD24^hi CD38^hi transitional B cells specifically secrete IL-10 and express CD9. Thus, patients with a total CD9⁺ B cell frequency below 6.6% displayed significantly higher incidence of bronchiolitis obliterans syndrome (AUC = 0.836, PPV = 0.75, NPV = 1). These data are the first to associate IL-10-secreting CD24^hi CD38^hi transitional B cells expressing CD9 with better allograft outcome in lung transplant recipients. CD9-expressing B cells appear as a contributor to a favorable environment essential for the maintenance of long-term stable graft function and as a new predictive biomarker of bronchiolitis obliterans syndrome-free survival.