Steeve Provencher

Long-Term Response to Calcium Channel Blockers in Idiopathic Pulmonary Arterial Hypertension

Background—Characteristics of patients with idiopathic pulmonary arterial hypertension (IPAH) who benefit from long-term calcium channel blockers (CCB) are unknown. Methods and Results—Acute pulmonary vasodilator testing with epoprostenol or nitric oxide was performed in 557 IPAH patients. Acute responders, defined by a fall in both mean pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR) >20%, received long-term oral CCB. Patients who benefit from long-term CCB were defined as those being in New York Heart Association (NYHA) functional class I or II after at least 1 year on CCB monotherapy. Among the 70 patients who displayed acute pulmonary vasoreactivity (12.6%; 95% CI, 9.8% to 15.3%) and received CCB therapy, only 38 showed long-term improvement (6.8%; 95% CI, 4.7% to 8.9%). Long-term CCB responders had less severe disease at baseline than patients who failed. During acute vasodilator testing, long-term CCB responders displayed a more pronounced fall in mean PAP (−39±11% versus −26±7%; P<0.0001), reaching an absolute value of mean PAP lower than that measured in patients who failed (33±8 versus 46±10 mm Hg; P<0.0001). After 7.0±4.1 years, all but 1 long-term CCB responders were alive in NYHA class I or II, with a sustained hemodynamic improvement. In the group of patients who failed on CCB, the 5-year survival rate was 48%. Conclusions—Long-term CCB responders represent <10% of IPAH patients evaluated in a pulmonary vascular referral center. During acute vasodilator testing, these patients showed significantly lower levels of both mean PAP and PVR, which reached near-normal values.

End points and clinical trial design in pulmonary arterial hypertension.

New and emerging therapies might provide benefit in patients with pulmonary arterial hypertension. Their efficacy and safety will be compared with existing combination therapies in randomized clinical trials. Appropriate end points for these trials need to be identified: these will include exercise testing, the composite end point of time to clinical worsening, and hemodynamic markers, including advanced imaging modalities and biomarkers. Quality-of-life questionnaires are useful and important secondary end points; pulmonary arterial hypertension-specific questionnaires are currently being developed. Advantages and disadvantages of various trial designs, including placebo-controlled monotherapy or add-on trials, noninferiority studies, and withdrawal trials are also discussed.

Stress Doppler Echocardiography in Relatives of Patients With Idiopathic and Familial Pulmonary Arterial Hypertension Results of a Multicenter European Analysis of Pulmonary Artery Pressure Response to Exercise and Hypoxia

Background— This large, prospective, multicentric study was performed to analyze the distribution of tricuspid regurgitation velocity (TRV) values during exercise and hypoxia in relatives of patients with idiopathic and familial pulmonary arterial hypertension (PAH) and in healthy control subjects. We tested the hypothesis that relatives of idiopathic/familial PAH patients display an enhanced frequency of hypertensive TRV response to stress and that this response is associated with mutations in the bone morphogenetic protein receptor II (BMPR2) gene. Methods and Results— TRV was estimated by Doppler echocardiography during supine bicycle exercise in normoxia and during 120 minutes of normobaric hypoxia (Fio2=12%; ≈4500 m) in 291 relatives of 109 PAH patients and in 191 age-matched control subjects. Mean maximal TRVs were significantly higher in PAH relatives during both exercise and hypoxia. During exercise, 10% of control subjects but 31.6% of relatives (P<0.0001) exceeded the 90% quantile of mean maximal TRV seen in control subjects. Hypoxia revealed hypertensive TRV in 26% of relatives (P=0.0029). Among control subjects, TRV at rest was not related to age, sex, body mass index, systemic blood pressure, smoking status, or heart rate. Within kindreds identified as harboring deleterious mutations of the BMPR2 gene, a hypertensive TRV response occurred significantly more often compared with those without detected mutations. Conclusions— Pulmonary hypertensive response to exercise and hypoxia in idiopathic/familial PAH relatives appears as a genetic trait with familial clustering, being correlated to but not caused by a BMPR2 mutation. The suitability of this trait to predict manifest PAH development should be addressed in long-term follow-up studies.

Signal Transducers and Activators of Transcription-3/Pim1 Axis Plays a Critical Role in the Pathogenesis of Human Pulmonary Arterial Hypertension

Background— Pulmonary artery hypertension (PAH) is a proliferative disorder associated with enhanced pulmonary artery smooth muscle cell proliferation and suppressed apoptosis. The sustainability of this phenotype required the activation of a prosurvival transcription factor like signal transducers and activators of transcription-3 (STAT3) and nuclear factor of activated T cell (NFAT). Because these factors are implicated in several physiological processes, their inhibition in PAH patients could be associated with detrimental effects. Therefore, a better understanding of the mechanism accounting for their expression/activation in PAH pulmonary artery smooth muscle cells is of great therapeutic interest. Methods and Results— Using multidisciplinary and translational approaches, we demonstrated that STAT3 activation in both human and experimental models of PAH accounts for the expression of both NFATc2 and the oncoprotein kinase Pim1, which trigger NFATc2 activation. Because Pim1 expression correlates with the severity of PAH in humans and is confined to the PAH pulmonary artery smooth muscle cell, Pim1 was identified as an attractive therapeutic target for PAH. Indeed, specific Pim1 inhibition in vitro decreases pulmonary artery smooth muscle cell proliferation and promotes apoptosis, all of which are sustained by NFATc2 inhibition. In vivo, tissue-specific inhibition of Pim1 by nebulized siRNA reverses monocrotaline-induced PAH in rats, whereas Pim1 knockout mice are resistant to PAH development. Conclusion— We demonstrated for the first time that inhibition of the inappropriate activation of STAT3/Pim1 axis is a novel, specific, and attractive therapeutic strategy to reverse PAH.

Peripheral muscle dysfunction in idiopathic pulmonary arterial hypertension

Background A majority of patients with idiopathic pulmonary arterial hypertension (IPAH) display persistent exercise intolerance despite new specific therapies. Whether patients with IPAH exhibit peripheral muscle dysfunction that may contribute to this limitation remains unknown. The hypothesis that the muscles of patients with IPAH are weaker and display morphological changes compared with those of control subjects and that those changes partly correlate with their exercise capacity was tested. Objective To characterise quadriceps function, morphology and the enzymatic profile of patients with IPAH. Methods Exercise capacity, limb muscle cross-sectional area by CT scan, quadriceps strength by maximal voluntary contraction and non-volitional magnetic stimulation of the femoral nerve (quadriceps twitch; TWq), and muscle morphology and enzymatic profile by quadriceps biopsy of 10 patients with IPAH were compared with those of 10 matched controls subjects. Results Patients with IPAH displayed a lower proportion of type I muscle fibres (p=0.05), a lower maximal voluntary contraction (p=0.05) and TWq (p=0.01), and an increased muscular phosphofructokinase/3-hydroxyacyl-CoA-dehydrogenase ratio (p=0.05). They also tended to have lower thigh muscle cross-sectional area (p=0.15). Maximal oxygen uptake correlated with quadriceps strength (R2=0.42, p=0.04), and oxygen uptake at anaerobic threshold correlated with muscle oxidative capacity assessed by oxidative enzyme level for citrate synthase (R2=0.45, p=0.05) and 3-hydroxyacyl-CoA-dehydrogenase (R2=0.86, p<0.01), and type I fibre capillarity (R2=0.57, p=0.02). Conclusion Patients with IPAH present significant peripheral muscle changes that partly correlated with their exercise capacity.

Heart rate responses during the 6-minute walk test in pulmonary arterial hypertension

Patients with pulmonary arterial hypertension (PAH) exhibit a limited increase in stroke volume on exercise, and the heart rate (HR) increases may reflect the main mechanism that allows cardiac output to increase. The current prospective study documented the contribution of HR to the 6-min walking distance (6MWD) in idiopathic (IPAH) and nonidiopathic PAH. Eighty-three patients (46 IPAH and 37 nonidiopathic PAH) underwent haemodynamic evaluation and a 6MWD test. Chronotropic response (peak walking HR minus resting HR) and peripheral oxygen saturation were monitored. Fifty-seven patients were also assessed after 5±2 months of treatment (bosentan n = 38, epoprostenol n = 14, bosentan-epoprostenol n = 3, iloprost n = 2). Before treatment, the 6MWD was related to numerous demographic, haemodynamic and walking test characteristics. Stepwise regression analysis indicated that the only factors significantly associated with the 6MWD were stroke volume and chronotropic response in both IPAH and nonidiopathic PAH patients. Following treatment, changes in 6MWD were significantly related to changes in chronotropic response in both IPAH and nonidiopathic PAH. In conclusion, baseline stroke volume and chronotropic response were independently associated with the 6-min walking distance in pulmonary arterial hypertension. The lack of chronotropic response may reflect the loss in normal physiological reserve in more unwell patients.

Role for DNA Damage Signaling in Pulmonary Arterial Hypertension

Background— Pulmonary arterial hypertension (PAH) is associated with sustained inflammation known to promote DNA damage. Despite these unfavorable environmental conditions, PAH pulmonary arterial smooth muscle cells (PASMCs) exhibit, in contrast to healthy PASMCs, a pro-proliferative and anti-apoptotic phenotype, sustained in time by the activation of miR-204, nuclear factor of activated T cells, and hypoxia-inducible factor 1-&agr;. We hypothesized that PAH-PASMCs have increased the activation of poly(ADP-ribose) polymerase-1 (PARP-1), a critical enzyme implicated in DNA repair, allowing proliferation despite the presence of DNA-damaging insults, eventually leading to PAH. Methods and Results— Human PAH distal pulmonary arteries and cultured PAH-PASMCs exhibit increased DNA damage markers (53BP1 and &ggr;-H2AX) and an overexpression of PARP-1 (immunoblot and activity assay), in comparison with healthy tissues/cells. Healthy PASMCs treated with a clinically relevant dose of tumor necrosis factor-&agr; harbored a similar phenotype, suggesting that inflammation induces DNA damage and PARP-1 activation in PAH. We also showed that PARP-1 activation accounts for miR-204 downregulation (quantitative reverse transcription polymerase chain reaction) and the subsequent activation of the transcription factors nuclear factor of activated T cells and hypoxia-inducible factor 1-&agr; in PAH-PASMCs, previously shown to be critical for PAH in several models. These effects resulted in PASMC proliferation (Ki67, proliferating cell nuclear antigen, and WST1 assays) and resistance to apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling and Annexin V assays). In vivo, the clinically available PARP inhibitor ABT-888 reversed PAH in 2 experimental rat models (Sugen/hypoxia and monocrotaline). Conclusions— These results show for the first time that the DNA damage/PARP-1 signaling pathway is important for PAH development and provide a new therapeutic target for this deadly disease with high translational potential.

Sirtuin 3 deficiency is associated with inhibited mitochondrial function and pulmonary arterial hypertension in rodents and humans.

Suppression of mitochondrial function promoting proliferation and apoptosis suppression has been described in the pulmonary arteries and extrapulmonary tissues in pulmonary arterial hypertension (PAH), but the cause of this metabolic remodeling is unknown. Mice lacking sirtuin 3 (SIRT3), a mitochondrial deacetylase, have increased acetylation and inhibition of many mitochondrial enzymes and complexes, suppressing mitochondrial function. Sirt3KO mice develop spontaneous PAH, exhibiting previously described molecular features of PAH pulmonary artery smooth muscle cells (PASMC). In human PAH PASMC and rats with PAH, SIRT3 is downregulated, and its normalization with adenovirus gene therapy reverses the disease phenotype. A loss-of-function SIRT3 polymorphism, linked to metabolic syndrome, is associated with PAH in an unbiased cohort of 162 patients and controls. If confirmed in large patient cohorts, these findings may facilitate biomarker and therapeutic discovery programs in PAH.

Changes in exercise haemodynamics during treatment in pulmonary arterial hypertension

Improvement in exercise capacity may not be associated with significant changes in resting pulmonary haemodynamics. The present prospective study documented the relationships between improvement in 6-min walking distance (6MWD) and changes in resting and exercise pulmonary haemodynamics after treatment in patients with idiopathic pulmonary arterial hypertension (IPAH). A total of 42 IPAH patients underwent supine submaximal exercise haemodynamic assessments at baseline and after 5±2 months of therapy. The 6MWD, the corresponding chronotropic response (peak minus resting heart rate), and resting and exercise haemodynamic variables were analysed. The isoflow was defined as the lowest of the pre- and post-treatment peak cardiac index (CI). The extrapolated isoflow mean pulmonary artery pressure (P̄pa) was used to characterise changes in P̄pa–CI regression lines following treatment. Patients were given bosentan (n = 28), epoprostenol (n = 12) or both. The 6MWD increased significantly, from 399±88 to 442±86 m. On univariate analysis, changes in 6MWD correlated with changes in isoflow P̄pa, chronotropic response, resting haemodynamics (CI, pulmonary vascular resistance and mixed venous oxygen saturation) and exercise haemodynamics (peak CI). On multivariate analysis, only changes in isoflow P̄pa and chronotropic response were independently associated with changes in 6MWD. Improvement in exercise tolerance with chronic therapy is independently related to improvement in pulmonary haemodynamics measured in exercise but not in resting conditions.

Influences of spinal anesthesia on exercise tolerance in patients with chronic obstructive pulmonary disease.

RATIONALE Lower limb muscle dysfunction contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). We hypothesized that signaling from lower limb muscle group III/IV sensory afferents to the central motor command could be involved in premature cycling exercise termination in COPD. OBJECTIVES To evaluate the effects of spinal anesthesia, which presumably inhibited central feedback from the lower limb muscle group III/IV sensory afferents on exercise tolerance and cardiorespiratory response during constant work-rate cycling exercise in patients with COPD. METHODS In a crossover and double-blind randomized design, eight patients with COPD (FEV(1), 67 ± 8% predicted) completed a constant work-rate cycling exercise after sham (NaCl, interspinous L(3)-L(4)) or active (fentanyl 25 μg, intrathecal L(3)-L(4)) spinal anesthesia. MEASUREMENTS AND MAIN RESULTS When compared with placebo, endurance time was significantly prolonged after spinal anesthesia with fentanyl (639 ± 87 s vs. 423 ± 38 s [mean ± SEM]; P = 0.01). Ventilation and respiratory rate were reduced at isotime points under the fentanyl condition, whereas ventilatory efficiency and dead space ventilation were improved. Patients exhibited less dynamic hyperinflation at isotime points with spinal anesthesia. Consequently, the rise in dyspnea was significantly flatter during the fentanyl condition than with placebo. CONCLUSIONS Spinal anesthesia enhanced cycling exercise tolerance in patients with COPD, mostly by reducing ventilatory response and dyspnea during exercise; these effects were possibly mediated through the inhibition of group III/IV lower limb sensory muscle afferents.