368 Circ Heart Fail March 2014

36% of cases. Collectively, the expected rate of PH in the wide variety of HFpEF phenotypes can be≈ 50%. Whereas in HFrEF a distinctive feature is LV enlargement and loss of function, in PH-HFpEF, the preserved EF and, in some instance, morphological characteristics of the LV may generate some overlap with the phenotype of pulmonary arterial hypertension (PAH). This may happen especially when clinical presentation is similar despite important clinical clues that may differentiate the 2 conditions, such as the presence of left atrial enlargement, left ventricular hypertrophy (LVH), and the finding of subclinical pulmonary edema on chest radiograph. In this regard, it is helpful to follow the algorithm proposed by the task force of the 4th WHO Symposium at the Dana Point (Figure 3). 28 What it suggested is that patients with dyspnea and

Echo diagnosis of preserved EF can be allocated in 3 different groups. There is a small group of patients in whom, despite normal EF, a diagnosis of PH-HFpEF is unlikely, because they are young with no comorbidities, having chest radiograph findings typical and drug use specific of PAH. Then, there is the group of patients, the vast majority, in whom it is easy to define a PH-HFpEF picture. They exhibit all the demographic and clinical characteristics typically described in population-based trials, such as old age with a constellation of cardiovascular risk factors, LVH, and atrial enlargement at echo, RX findings of HF and increased natriuretic peptide levels. Finally, there is a minority whose diagnosis is uncertain, because they have any age, are euvolemic with no or mild hypertension and few comorbid risk factors, and LVH is not clearly detectable at echocardiography. This is the subset of patients that need right heart characterization (RHC) to define whether they definitively have PAH, PH-HFpEF, or mixed forms. RHC is useful because it helps to better stratify to pure diastolic component as cause of PH (PCWP≥ 15 mm Hg and pulmonary vascular resistance [PVR] within normal limits), primarily PAH when PVR≥ 3 wood/unit and PCWP< 15 mm Hg or the condition with increased PVR≥ 3 wood/unit and elevated PWCP. This condition may be challenged with pharmacological agents and results into a reduction in PCWP and not of PVR or both, suggestive of PAH and HFpEF, respectively. Recent observational studies have clarified the population characteristics of PH-HFpEF. Thenappan et al14 found that for similar mean PAP elevation, right ventricular hypertrophy, and right atrial enlargement, these patients were older, had a higher prevalence of cardiovascular comorbidities, worse exercise capacity and renal function, and often had left atrial enlargement compared with patients with idiopathic PAH. Compared with HFpEF without PH, a higher portion of patients with PH-HFpEF was female, and RV geometry was indicative of RV enlargement and hypertrophy. These changes were similar to those observed in PAH. In the study by Leung