Polysplenia Syndrome a Risk Factor for Early PH, Study Suggests

People with polysplenia syndrome — a condition characterized by a “left-sidedness” on both sides of the body — have an increased risk for early development of pulmonary hypertension (PH), a Japanese study suggests.

The study, titled “Polysplenia Syndrome as a Risk Factor for Early Progression of Pulmonary Hypertension,” was published in the Circulation Journal.

Polysplenia syndrome is a birth defect — also known as a congenital defect — where the left-right orientation of organs during embryonic development is compromised. In these patients, there is a left-sidedness on both sides of the body. Typically, this results in the formation of many small spleens, without forming a parent spleen, hence the name poly (many) spleens.

The symmetry problem extends to the heart, and these patients have congenital heart disease, particularly a defect called atrioventricular septal defect (AVSD). This means that the valves that separate the hearts’ upper chambers (atriums) from the lower chambers (ventricles) are not formed correctly, affecting the blood flow.

Besides cardiac complications, patients with congenital heart defects also suffer from PH.

Because polysplenia syndrome can often cause congenital heart defects, a team of Japanese researchers evaluated the development of PH in these patients.

They analyzed medical records of 236 patients who had been diagnosed with polysplenia syndrome at two centers of pediatric cardiology, Keio University Hospital and Tokyo Women’s Medical University Hospital, from 1978 to 2015.

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After excluding patients older than 30 at diagnosis, those with a follow-up shorter than six months, and those without cardiac catheterization data, they selected 16 patients with polysplenia who had incomplete AVSD to be part of the polysplenia group. As controls, they selected 22 age-matched patients with incomplete AVSD but without any syndromes, including polysplenia.

The team found that before surgical intervention to correct the septal defect, polysplenia patients had a mean pulmonary arterial pressure of 37.3 millimeters of mercury (mmHg), compared to 19.1 in the control group. Moreover, the pulmonary vascular resistance index — the resistance offered to blood circulation in the lungs — was about 5.7 Wood units per square meter in polysplenia patients, and 1.4 in control patients.

PH was considered to be present if pulmonary arterial pressure was above 25 mmHg, and pulmonary vascular resistance was above three Wood units. Using this criteria, the team observed that 56% of the polysplenia group had PH, while only 9% of controls had it.

Among the eight patients with polysplenia and PH who underwent surgical repair of AVSD, 87.5% still had residual PH after surgery, whereas in the control group the two patients who developed PH before surgery had an improvement of PH after the procedure.

All nine polysplenia patients with PH before surgery had a prediction of poor outcomes regarding their PH after surgery or were unable to undergo surgery due to severe PH. All patients in the control group had a good prognosis without any signs of PH after surgery.

“This suggests that pulmonary hypertension may develop earlier even with lower increased pulmonary blood flow in incomplete AVSD patients with polysplenia than in those without polysplenia,” researchers said.

Overall, these findings suggest polysplenia as a risk factor for PH associated with congenital heart defects.

“Polysplenia syndrome carries a risk of development of PH from early infancy. It is therefore necessary to prepare for the rapid progression of PH from the early postnatal period in the case of polysplenia even with incomplete AVSD, which is not usually associated with PH,” the team concluded.