Abstract 9223: In vivo Assessment of Pulmonary Arterial Wall Fibrosis by Intravascular optical Coherence Tomography in Pulmonary Arterial Hypertension: A New Prognostic Marker of Adverse Clinical Follow-Up

Abstract

The aim of the study is to quantify pulmonary artery (PA) wall fibrosis by intravascular optical coherence tomography (OCT) in severe pulmonary arterial hypertension (PAH) and to correlate it with clinical follow-up. Histological and OCT study of PA specimens is also performed. OCT is an imaging modality for studying vessel wall structure with higher resolution than intravascular ultrasound. Nineteen consecutive PAH patients , aged 54±16 (4 men) , functional class II-III were studied with simultaneous right heart catheterization and OCT in inferior lobe PA segments (2-4 mm diameter). Relative PA wall fibrosis (%fibrosis) was obtained by OCT (area of fibrosis/PA cross sectional area×100). All patients were prospectively followed up. Physicians who carried out the clinical follow-up were blind to the OCT results. Patients were initially divided into 2 groups, low and high degree of fibrosis, according to the median value of PA wall OCT % fibrosis. Clinical deterioration had been initially defined in terms of either mortality, lung transplantation, need of intravenous prostaglandins or onset of clinical right ventricular failure. OCT measurements showed a high intra and interobserver agreement. There was a good correlation between OCT and histological fibrosis in PA wall from explanted lungs. In the whole group area of fibrosis was 1.4±0.8 mm 2 and % fibrosis was 22.3±8. All patients were prospectively followed-up with an average follow-up of 3.5 years (2.5-4.5 years). Patients were divided into 2 groups, low and high degree of fibrosis, according to the median value of PA wall OCT fibrosis percentage ( 22% ). There were 10 patients with a high degree of fibrosis ( ≥ 22% ) and 9 with a lower degree of fibrosis (<22% ). Clinical events, as previously defined, were present in 6 patients ( 1 death, 1 lung transplantation, 2 intravenous prostaglandins, 2 right heart failure ) out of 10 patients with high fibrosis and in 0 out of 9 patients with low fibrosis ( p<0.01). In PAH, the severity of PA remodeling assessed by quantification of PA wall fibrosis by OCT was significantly predictive of severely unfavorable clinical outcome. There was a good correlation between OCT and histological fibrosis in explanted PA.