Anna R. Hemnes

Hyponatremia Predicts Right Heart Failure and Poor Survival in Pulmonary Arterial Hypertension

RATIONALE Hyponatremia is associated with decompensated heart failure and poor prognosis in patients with left ventricular systolic dysfunction. OBJECTIVES We sought to determine if hyponatremia is associated with right heart failure and worse prognosis in patients with pulmonary arterial hypertension (PAH). METHODS We prospectively followed 40 patients with PAH and examined the relationship between serum sodium and right heart function as well as survival. MEASUREMENTS AND MAIN RESULTS Subjects with hyponatremia (Na < or = 136 mEq/L) were more symptomatic (11/13 World Health Organization [WHO] class III/IV vs. 12/27 WHO class III/IV; P = 0.02), had more peripheral edema (69 vs. 26%; P = 0.009), and had higher hospitalization rates (85 vs. 41%; P = 0.009) than normonatremic subjects. Hyponatremic subjects had higher right atrial pressure (14 +/- 6 vs. 9 +/- 3 mm Hg; P < 0.001), lower stroke volume index (21 +/- 7 vs. 32 +/- 10 ml/m(2); P < 0.01), larger right ventricular:left ventricular area ratio (1.8 +/- 0.4 vs. 1.3 +/- 0.4; P < 0.001), and lower tricuspid annular plane systolic excursion (1.4 +/- 0.3 vs. 2.0 +/- 0.6 cm; P = 0.001), despite similar mean pulmonary artery pressure (49 +/- 10 vs. 47 +/- 12 mm Hg; P = 0.60). The 1- and 2-year survival estimates were 93% (95% confidence interval [CI], 73-98%) and 85% (95% CI, 65-94%), and 38% (95% CI, 14-63%) and 15% (95% CI, 2-39%) for normonatremic and hyponatremic subjects, respectively (log-rank chi(2) = 25.19, P < 0.001). The unadjusted risk of death (hazard ratio) in hyponatremic compared with normonatremic subjects was 10.16 (95% CI, 3.42-30.10, P < 0.001). Hyponatremia predicted outcome after adjusting for WHO class, diuretic use, as well as right atrial pressure and cardiac index. CONCLUSIONS Hyponatremia is strongly associated with right heart failure and poor survival in PAH.

Association of the Metabolic Syndrome With Pulmonary Venous Hypertension

BACKGROUND Pulmonary venous hypertension (PVH) is a well-described cause of pulmonary hypertension (PH) in patients with left heart disease associated with elevated left heart filling pressure. PVH results from a number of processes, including left-sided valvular disease, constrictive pericardial disease, restrictive cardiomyopathies, and left ventricular (LV) systolic dysfunction. PVH in patients with normal LV systolic function, commonly referred to as diastolic dysfunction, is not well characterized. We observed that many patients with PH due to PVH have obesity, hypertension, diabetes mellitus, and hypercholesterolemia, which are clinical features of the metabolic syndrome (MS), a previously identified cause for systemic vascular disease. METHODS We evaluated 122 consecutive patients referred for diagnosis and treatment of PH and compared the prevalence of features of the MS between patients with PVH and those with pulmonary arterial hypertension (PAH). We also compared clinical and hemodynamic characteristics between these two groups. RESULTS Compared to patients with PAH, patients with PVH had a higher frequency of hypertension, obesity, diabetes mellitus, and hyperlipidemia. Two or more features of the MS were found in 16 of 17 patients with PVH (94.1%) compared with 34.3% of patients with PAH (p < 0.001; odds ratio, 30.7; 95% confidence interval, 3.6 to 260.0). PH was substantial, but less severe overall, in patients with PVH compared to those with PAH (mean pulmonary artery pressure, 45 +/- 17 mm Hg [range, 26 to 71 mm Hg] vs 53 +/- 10 [range, 33 to 72 mm Hg], respectively [p = 0.041]; and pulmonary vascular resistance, 4.4 +/- 2.9 units [range, 1.2 to 10.8 units] vs 10.8 +/- 4.7 units [range, 4.8 to 21.9 units], respectively [p < 0.001]). CONCLUSION PVH is highly associated with the MS. Our results suggest that the MS may predispose patients to develop pulmonary vascular disease.

PDE5A Inhibitor Treatment of Persistent Pulmonary Hypertension After Mechanical Circulatory Support

Background—Pulmonary hypertension (PH) secondary to left heart failure portends a poor prognosis and is a relative contraindication to heart transplantation at many centers. We tested the hypothesis that when PH persists after adequate left ventricle unloading via recent left ventricular assist device (LVAD) therapy, phosphodiesterase type 5A inhibition would decrease PH in this population. Methods and Results—We performed an open-label clinical trial using control patients not receiving therapy. Between 1999 and 2007, 138 consecutive patients undergoing cardiac transplantation evaluation with advanced left ventricular dysfunction, an elevated pulmonary capillary wedge pressure, and PH (defined by a pulmonary vascular resistance (PVR) >3 Woods Units), were treated with LVAD therapy. Fifty-eight of these patients reduced their pulmonary capillary wedge pressure to a value <15 mm Hg (11.8±2.0 mm Hg from baseline 23.2±6.2 mm Hg) 1 to 2 weeks after LVAD implantation, but despite this improvement, the PVR of these patients was only minimally affected (5.65±3.00 to 5.39±1.78 Wood Units). Twenty-six consecutive patients from this group with persistently elevated PVR were started on oral phosphodiesterase type 5A inhibition with sildenafil and titrated to an average of dose of 51.9 mg by mouth 3 times per day. The average PVR in the sildenafil-treated group fell from 5.87±1.93 to 2.96±0.92 Wood Units (P<0.001) and the mean pulmonary artery pressure fell from 36.5±8.6 to 24.3±3.6 mm Hg (P<0.0001) and was significantly lower when compared with the 32 LVAD recipients not receiving sildenafil at weeks 12 to 15 after the initial post-LVAD hemodynamic measurements (13 to 17 weeks post-LVAD implantation). In addition, hemodynamic measurements of right ventricular function in sildenafil-treated patients was also improved compared with patients not receiving sildenafil. Conclusions—In patients with persistent PH after recent LVAD placement, phosphodiesterase type 5A inhibition in this open-label trial resulted in a significant decrease in PVR when compared with control patients.

EIF2AK4 Mutations in Pulmonary Capillary Hemangiomatosis

BACKGROUND Pulmonary capillary hemangiomatosis (PCH) is a rare disease of capillary proliferation of unknown cause and with a high mortality. Families with multiple affected individuals with PCH suggest a heritable cause although the genetic etiology remains unknown. METHODS We used exome sequencing to identify a candidate gene for PCH in a family with two affected brothers. We then screened 11 unrelated patients with familial (n = 1) or sporadic (n = 10) PCH for mutations. RESULTS Using exome sequencing, we identified compound mutations in eukaryotic translation initiation factor 2 α kinase 4 (EIF2AK4) (formerly known as GCN2) in both affected brothers. Both parents and an unaffected sister were heterozygous carriers. In addition, we identified two EIF2AK4 mutations in each of two of 10 unrelated individuals with sporadic PCH. EIF2AK4 belongs to a family of kinases that regulate angiogenesis in response to cellular stress. CONCLUSIONS Mutations in EIF2AK4 are likely to cause autosomal-recessive PCH in familial and some nonfamilial cases.

High Prevalence of Occult Pulmonary Venous Hypertension Revealed by Fluid Challenge in Pulmonary Hypertension

Background— Determining the cause for pulmonary hypertension is difficult in many patients. Pulmonary arterial hypertension (PAH) is differentiated from pulmonary venous hypertension (PVH) by a wedge pressure (PWP) >15 mm Hg in PVH. Patients undergoing right heart catheterization for evaluation of pulmonary hypertension may be dehydrated and have reduced intravascular volume, potentially leading to a falsely low measurement of PWP and an erroneous diagnosis of PAH. We hypothesized that a fluid challenge during right heart catheterization would identify occult pulmonary venous hypertension (OPVH). Methods and Results— We reviewed the results of patients undergoing fluid challenge in our pulmonary hypertension database from 2004 to 2011. Baseline hemodynamics were obtained and repeated after infusion of 0.5 L of normal saline for 5 to 10 minutes. Patients were categorized as OPVH if PWP increased to >15 mm Hg after fluid challenge. Baseline hemodynamics in 207 patients met criteria for PAH. After fluid challenge, 46 patients (22.2%) developed a PWP >15 mm Hg and were reclassified as OPVH. Patients with OPVH had a greater increase in PWP compared with patients with PAH, P<0.001, and their demographics and comorbid illnesses were similar to patients with PVH. There were no adverse events related to fluid challenge. Conclusions— Fluid challenge at the time of right heart catheterization is easily performed, safe, and identifies a large group of patients diagnosed initially with PAH, but for whom OPVH contributes to pulmonary hypertension. These results have implications for therapeutic trials in PAH and support the routine use of fluid challenge during right heart catheterization in patients with risk factors for PVH.

Unrecognized glucose intolerance is common in pulmonary arterial hypertension

BACKGROUND Animal and human data suggest insulin resistance is common in pulmonary arterial hypertension (PAH). Although routine assessment of insulin resistance is difficult, hemoglobin A(1c) (HbA(1c)) is a sensitive test to detect diabetes mellitus (DM) and those at high risk for DM. We aimed to define the prevalence of elevated HbA(1c) in PAH patients and to correlate HbA(1c) levels with functional assessment. METHODS HbA(1c) was measured in 41 PAH patients without a diagnosis of DM, along with demographic, functional, and hemodynamic data. Using published criteria, HbA(1c) ≤ 5.9% defined normal, 6.0% to 6.4% was glucose intolerance, and ≥ 6.5% was DM. RESULTS Twenty-three patients (56%) had HbA(1c) ≥ 6.0%, and 6 (15%) had unrecognized DM (HbA(1c) ≥ 6.5%). Age and body mass index were similar in patients with HbA(1c) ≥ 6.0% vs < 6.0%. There was a trend towards lower mean 6-minute walk distance in patients with elevated HbA(1c) (331.0 ± 126.6 vs 413.6 ± 74.9 meters, p = 0.07). The 6-month event-free survival was not significantly different in patients with elevated HbA(1c). CONCLUSIONS Unrecognized glucose intolerance as assessed by HbA(1c) is common in PAH. Further studies are needed to discern if glucose or insulin dysregulation mediates PAH pathogenesis or is secondary to advanced PAH.

Longitudinal Analysis Casts Doubt on the Presence of Genetic Anticipation in Heritable Pulmonary Arterial Hypertension

RATIONALE Analysis of the age of onset in heritable pulmonary arterial hypertension (HPAH) has led to the hypothesis that genetic anticipation causes younger age of onset and death in subsequent generations. With accrual of pedigree data over multiple decades, we retested this hypothesis using analyses that eliminate the truncation of data that exists with shorter duration of follow-up. OBJECTIVES To analyze the pedigrees of families with mutations in bone morphogenetic protein receptor type 2 (BMPR2), afflicted in two or more generations with HPAH, eliminating time truncation bias by including families for whom we have at least 57 years of data. METHODS We analyzed 355 individuals with BMPR2 mutations from 53 families in the Vanderbilt Pulmonary Hypertension Registry. We compared age at diagnosis or death in affected individuals (n = 249) by generation within families with multigenerational disease. We performed linear mixed effects models and we limited time-truncation bias by restricting date of birth to before 1955. This allowed for 57 years of follow-up (1955-2012) for mutation carriers to develop disease. We also conducted Kaplan-Meier analysis to include currently unaffected mutation carriers (n = 106). MEASUREMENTS AND MAIN RESULTS Differences in age at diagnosis by generation were found in a biased analysis that included all birth years to the present, but this finding was eliminated when the 57-year observation limit was imposed. By Kaplan-Meier analysis, inclusion of currently unaffected mutation carriers strengthens the observation that bias of ascertainment exists when recent generations are included. CONCLUSIONS Genetic anticipation is likely an artifact of incomplete time of observation of kindreds with HPAH due to BMPR2 mutations.

Cytoskeletal defects in Bmpr2-associated pulmonary arterial hypertension

The heritable form of pulmonary arterial hypertension (PAH) is typically caused by a mutation in bone morphogenic protein receptor type 2 (BMPR2), and mice expressing Bmpr2 mutations develop PAH with features similar to human disease. BMPR2 is known to interact with the cytoskeleton, and human array studies in PAH patients confirm alterations in cytoskeletal pathways. The goal of this study was to evaluate cytoskeletal defects in BMPR2-associated PAH. Expression arrays on our Bmpr2 mutant mouse lungs revealed cytoskeletal defects as a prominent molecular consequence of universal expression of a Bmpr2 mutation (Rosa26-Bmpr2(R899X)). Pulmonary microvascular endothelial cells cultured from these mice have histological and functional cytoskeletal defects. Stable transfection of different BMPR2 mutations into pulmonary microvascular endothelial cells revealed that cytoskeletal defects are common to multiple BMPR2 mutations and are associated with activation of the Rho GTPase, Rac1. Rac1 defects are corrected in cell culture and in vivo through administration of exogenous recombinant human angiotensin-converting enzyme 2 (rhACE2). rhACE2 reverses 77% of gene expression changes in Rosa26-Bmpr2(R899X) transgenic mice, in particular, correcting defects in cytoskeletal function. Administration of rhACE2 to Rosa26-Bmpr2(R899X) mice with established PAH normalizes pulmonary pressures. Together, these findings suggest that cytoskeletal function is central to the development of BMPR2-associated PAH and that intervention against cytoskeletal defects may reverse established disease.

Metabolomic analysis of bone morphogenetic protein receptor type 2 mutations in human pulmonary endothelium reveals widespread metabolic reprogramming

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease of the lung vasculature for which the molecular etiologies are unclear. Specific metabolic alterations have been identified in animal models and in PAH patients, though existing data focus mainly on abnormalities of glucose homeostasis. We hypothesized that analysis of the entire metabolome in PAH would reveal multiple other metabolic changes relevant to disease pathogenesis and possible treatment. Layered transcriptomic and metabolomic analyses of human pulmonary microvascular endothelial cells (hPMVEC) expressing two different disease-causing mutations in the bone morphogenetic protein receptor type 2 (BMPR2) confirmed previously described increases in aerobic glycolysis but also uncovered significant upregulation of the pentose phosphate pathway, increases in nucleotide salvage and polyamine biosynthesis pathways, decreases in carnitine and fatty acid oxidation pathways, and major impairment of the tricarboxylic acid (TCA) cycle and failure of anaplerosis. As a proof of principle, we focused on the TCA cycle, predicting that isocitrate dehydrogenase (IDH) activity would be altered in PAH, and then demonstrating increased IDH activity not only in cultured hPMVEC expressing mutant BMPR2 but also in the serum of PAH patients. These results suggest that widespread metabolic changes are an important part of PAH pathogenesis, and that simultaneous identification and targeting of the multiple involved pathways may be a more fruitful therapeutic approach than targeting of any one individual pathway.

Sildenafil monotherapy in portopulmonary hypertension can facilitate liver transplantation

Portopulmonary hypertension (POPH), or pulmonary arterial hypertension associated with cirrhosis, carries a high mortality and often precludes liver transplantation. Many POPH patients have preserved or increased cardiac output; therefore, decreasing pulmonary artery pressure rather than improving cardiac output is more important in reducing liver transplant risk, and this makes sildenafil an attractive therapeutic option. We assessed the clinical response of patients with POPH treated with sildenafil monotherapy. We retrospectively reviewed the charts of 10 patients with POPH and sildenafil monotherapy. Eight of 10 patients had hepatitis C virus infection. Patients took 31 ± 14 mg (mean ± standard deviation) thrice daily and were followed for 21 ± 16 months. The World Health Organization functional class improved from 3.0 ± 0.0 to 2.3 ± 0.5 at 1 year (P < 0.05). Four of 8 patients increased the 6‐minute walk distance at 1 year by 30 m or more. Three patients became transplant‐eligible, 1 of whom underwent successful transplantation, and 3 patients have been stable without progression of liver disease or POPH. The remainder were not transplant candidates because of refractory POPH (n = 2) or other comorbidities (n = 2). We conclude that sildenafil may be an effective therapy for POPH that can stabilize or improve hemodynamics in patients with POPH and thereby facilitate liver transplantation. Liver Transpl 15:15–19, 2009.