Hematological Markers Hold Promise as Prognostic Tools in PAH Associated With Congenital Heart Disease

Pulmonary arterial hypertension associated with congenital heart disease (PAH-CHD) is an important phenotype of pulmonary hypertension (PH) in children, as CHD makes up nearly a third of major congenital abnormalities. A recent study published in Pediatric Cardiology found that mean platelet volume (MPV), platelet distribution width (PDW), and platecrit (PCT) could potentially be useful prognostic biomarkers in children with PAH-CHD.

PAH is characterized by consistently high mean pulmonary arterial pressure (mPAP), and in the case of children with CHD it often results from a large systemic to pulmonary shunt. PAH can be debilitating, often leads to right ventricular failure and death, and there is no curative treatment for the condition. Therefore, early recognition of high-risk patients who need timely and aggressive treatment is critical.

MPV, PDW, and PCT are simple hematological markers for platelet function and activation. While some recent studies suggest that interactions between platelets and pulmonary arterioles might contribute to pulmonary vascular changes that occur in PAH, research on platelet markers in children with PAH-CHD has not been conclusive, study authors noted. Therefore, they aimed to evaluate the prognostic value of MPV, PDW, and PCT for adverse outcomes in this patient population.

The prospective cohort study included 60 children with PAH-CHD, 60 children with CHD without PAH, and an age- and sex-matched control group of 60 healthy children. Exclusion criteria included chronic respiratory disease, acute heart failure, pulmonary venous hypertension, platelet disorders, chronic liver or renal disease, and patients using antiplatelet or anticoagulant therapy.

The median age of children with PAH-CHD was 5.5 months, children with CHD but no PAH had a median age of 3.5 months, and the control group had a median age of 9 months. There were no significant differences between groups as far as age or sex, but children with CHD with or without PAH had lower weights than those in the control group. Heart rate and respiratory rate were also higher in patients with CHD compared with the control group.

All participants underwent echocardiography to assess the type of congenital heart disease and mPAP; MPV, PDW, and PCT were measured in blood samples with an automated blood counter. Follow-ups with each patient were conducted after 6 months for death or readmission.

Children with PAH-CHD had significantly higher PCT, MPV, and PDW than children with CHD alone and the control group. These hematological markers also correlated with disease severity. Patients with severe PH had significantly higher PCT, PDW, and MPV compared with patients whose PH was mild or moderate. Children with mild or moderate PH had comparable levels of all 3 markers.

MPV, PDW, and PCT all showed positive correlations with right ventricular diameter and mPAP but correlated negatively with right ventricular systolic and diastolic function. During follow-up, 8 of 60 PAH-CHD patients were either readmitted or died due to right ventricular heart failure, and platelet activation marker levels were notably higher in patients with poor prognoses compared with those with good prognoses.

Cut-off markers potentially indicative of prognosis included:

• MPV: Greater than 11.2 FL (75% sensitivity and 96.6% specificity)
• PDW: Greater than 12.7 FL (75% sensitivity and 61.5% specificity)
• PCT: Greater than 0.505% (75% sensitivity and 93.2% specificity)

Overall, the findings were in line with results from previous studies, and the authors concluded that these easily available, non-invasive markers have potential to help identify children with PAH-CHD with poor prognoses at admission.

Study limitations included a small sample size, the single-center nature of the study, and short follow-up duration. Larger studies could help confirm the findings, and further research is necessary to help identify the role of platelet activation in PAH-CHD.

Reference

Awad A, Elnemr S, Hodeib H, El Amrousy D. Platelet activation markers in children with pulmonary arterial hypertension associated with congenital heart disease. Pediatr Cardiol. Published online March 2, 2022. doi:10.1007/s00246-022-02847-7