PRESCRIBING IN PRACTICE ■ P ulmonary hypertension refers to increased pressure in the pulmonary arterial circulation. The pulmonary circulation has to accommodate the entire cardiac output in each cardiac cycle, and evolution has adapted to this by making it a low-pressure high-flow system. However, pathology can affect both the arterial and venous components of this system. Pulmonary venous hypertension mainly refers to diseases that result in elevated venous pressure and occurs mainly from mitral valve and left-sided heart disease; these will not be discussed in this article. As a result of greater understanding of the molecular and cellular pathways involved in the pathobiology of pulmonary arterial hypertension (PAH), novel and exciting treatments have become available to treat this condition. These new drugs represent a huge step forward in the treatment of this universally fatal disease in that they allow improvement in quality of life and survival; however, they do not as yet offer a cure. Definition PAH is defined by consensus as a mean pulmonary artery pressure of above 25mmHg in the setting of a normal or reduced cardiac output, with a normal pulmonary capillary wedge pressure (PCWP) and elevated pulmonary vascular resistance (PVR). The normal PCWP is required to exclude the presence of significant left heart disease and pulmonary venous hypertension. As a result, the diagnosis of pulmonary hypertension requires invasive right-heart catheterisation. Classification Pulmonary hypertension is an umbrella term that refers simply to elevated pressure in the pulmonary vasculature. There are a wide variety of causes of this and the 2008 WHO conference in Dana Point attempted to clarify and organise these into a more defined classification (see Figure 2). 1 This article will focus on PAH (group 1).

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The aim of a clinical classification of pulmonary hypertension (PH) is to group together different manifestations of disease sharing similarities in pathophysiologic mechanisms, clinical presentation, and therapeutic approaches. In 2003, during the 3rd World Symposium on Pulmonary Hypertension, the clinical classification of PH initially adopted in 1998 during the 2nd World Symposium was slightly modified. During the 4th World Symposium held in 2008, it was decided to maintain the general architecture and philosophy of the previous clinical classifications. The modifications adopted during this meeting principally concern Group 1, pulmonary arterial hypertension (PAH). This subgroup includes patients with PAH with a family history or patients with idiopathic PAH with germline mutations (e.g., bone morphogenetic protein receptor-2, activin receptor-like kinase type 1, and endoglin). In the new classification, schistosomiasis and chronic hemolytic anemia appear as separate entities in the subgroup of PAH associated with identified diseases. Finally, it was decided to place pulmonary veno-occlusive disease and pulmonary capillary hemangiomatosis in a separate group, distinct from but very close to Group 1 (now called Group 1'). Thus, Group 1 of PAH is now more homogeneous.

Background: Cardiac injury and myocarditis have been described in adults with COVID-19. SARS-CoV-2 infection in children is typically minimally symptomatic. We report a series of febrile pediatric patients with acute heart failure potentially associated with SARS-CoV-2 infection and the multisystem inflammatory syndrome in children (MIS-C) as defined by the US Centers for Disease Control. Methods: Over a two-month period contemporary with the SARS-CoV-2 pandemic in France and Switzerland, we retrospectively collected clinical, biological, therapeutic, and early outcomes data in children who were admitted to pediatric intensive care units in 14 centers for cardiogenic shock, left ventricular dysfunction and severe inflammatory state. Results: Thirty-five children were identified and included in the study. Median age at admission was 10 years (range 2-16 years). Co-morbidities were present in 28% including asthma and overweight. Gastrointestinal symptoms were prominent. Left ventricular ejection fraction was <30% in one third; 80% required inotropic support with 28% treated with ECMO. Inflammation markers were suggestive of cytokine storm (interleukin 6 median 135 pg/mL) and macrophage activation (D-dimer median 5284 ng/mL). Mean brain natriuretic peptide was elevated (5743 pg/mL). Thirty-one/35 (88%) patients tested positive for SARS-CoV-2 infection by PCR of nasopharyngeal swab or serology. All patients received intravenous immune globulin, with adjunctive steroid therapy used in one third. Left ventricular function was restored in the 25/35 of those discharged from the intensive care unit. No patient died, and all patients treated with ECMO were successfully weaned. Conclusion: Children may experience an acute cardiac decompensation due to severe inflammatory state following SARS-CoV-2 infection (multisystem inflammatory syndrome in children - MIS-C). Treatment with immune globulin appears to be associated with recovery of left ventricular systolic function.