Response to: 'CT assessment for pulmonary hypertension requires systematic assessment of cardiac, vascular and parenchymal signs' by Marloes et al

Current and emerging imaging techniques in the diagnosis and assessment of pulmonary hypertension

INTRODUCTION

Pulmonary hypertension (PH) is a challenging condition to diagnose and treat. Over the last two decades, there have been significant advances in therapeutic approaches and imaging technologies. Current guidelines emphasize the importance of cardiac catheterization; however, the increasing availability of non-invasive imaging has the potential to improve diagnostic rates, whilst providing additional information on patient phenotypes. Areas covered: This review discusses the role of imaging in the diagnosis, prognostic assessment and follow-up of patients with PH. Imaging methods, ranging from established investigations (chest radiography, echocardiography, nuclear medicine and computerized tomography (CT)), to emerging modalities (dual energy CT, magnetic resonance imaging (MRI), optical coherence tomography and positron emission tomography (PET)) are reviewed. The value and limitations of the clinical utility of these imaging modalities and their potential clinical application are reviewed. Expert commentary: Imaging plays a key role in the diagnosis and classification of pulmonary hypertension. It also provides valuable prognostic information and emerging evidence supports a role for serial assessments. The authors anticipate an increasing role for imaging in the pulmonary hypertension clinic. This will reduce the need for invasive investigations, whilst providing valuable insights that will improve our understanding of disease facilitate a more targeted approach to treatment.

Editor's Highlight: Pulmonary Vascular Thrombosis in Rats Exposed to Inhaled Sulfur Mustard

Sulfur mustard (SM) is a chemical warfare agent. When inhaled, SM causes significant injury to the respiratory tract. Although the mechanism involved in acute airway injury after SM inhalation has been well described previously, the mechanism of SM's contribution to distal lung vascular injury is not well understood. We hypothesized that acute inhalation of vaporized SM causes activated systemic coagulation with subsequent pulmonary vascular thrombi formation after SM inhalation exposure. Sprague Dawley rats inhaled SM ethanolic vapor (3.8 mg/kg). Barium/gelatin CT pulmonary angiograms were performed to assess for pulmonary vascular thrombi burden. Lung immunohistochemistry was performed for common procoagulant markers including fibrin(ogen), von Willebrand factor, and CD42d in control and SM-exposed lungs. Additionally, systemic levels of d-dimer and platelet aggregometry after adenosine diphosphate- and thrombin-stimulation were measured in plasma after SM exposure. In SM-exposed lungs, chest CT angiography demonstrated a significant decrease in the distal pulmonary vessel density assessed at 6 h postexposure. Immunohistochemistry also demonstrated increased intravascular fibrin(ogen), vascular von Willebrand factor, and platelet CD42d in the distal pulmonary vessels (<200 µm diameter). Circulating d-dimer levels were significantly increased (p < .001) at 6, 9, and 12 h after SM inhalation versus controls. Platelet aggregation was also increased in both adenosine diphosphate - (p < .01) and thrombin- (p < .001) stimulated platelet-rich plasma after SM inhalation. Significant pulmonary vascular thrombi formation was evident in distal pulmonary arterioles following SM inhalation in rats assessed by CT angiography and immunohistochemistry. Enhanced systemic platelet aggregation and activated systemic coagulation with subsequent thrombi formation likely contributed to pulmonary vessel occlusion.