Residual Pulmonary Hypertension After Pulmonary Endarterectomy Is Associated With Female Sex, Absence of Prior Venous Thromboembolism, and Higher Preoperative Mean Pulmonary Artery Pressure

The heart and lungs work as a tight team, pumping blood to the body and refreshing it with oxygen. Sometimes, blood clots travel to the lungs and get stuck, hardening into scar tissue over time. This condition, known as chronic thromboembolic pulmonary hypertension, creates a dangerous blockage that forces the heart to work much harder than it should. Without treatment, the pressure builds until the heart can no longer keep up, leading to severe illness or death. For patients who are eligible, surgeons can perform a delicate operation to physically remove these hardened clots from the lung arteries. This procedure offers a chance for a full recovery, but it is not a guarantee. Even after the surgery, some patients find that their blood pressure in the lungs remains too high, leaving them with a lingering form of the disease that requires ongoing care.

A team of researchers at a major hospital in Brazil set out to understand why this happens. They looked back at the records of 205 patients who underwent this surgery between 2015 and 2024. While most of these patients survived the operation, the researchers focused on the 149 who returned for a follow-up test where doctors measured the pressure inside their heart and lungs. They wanted to find specific clues in the patients' medical history that could predict who would still have high blood pressure after the surgery. The goal was to identify who might need closer monitoring or additional treatments sooner rather than later.

The study found that more than half of the patients who returned for testing still had high blood pressure in their lungs. When the researchers analyzed the data, three clear patterns emerged that were linked to this outcome. First, women were significantly more likely to have persistent high pressure than men. Second, patients who had never had a documented blood clot in their legs or lungs before developing the lung disease were much more likely to have lingering issues. Third, the higher the blood pressure in the lungs was before the surgery, the more likely it was to remain high afterward. These factors stood out even when the researchers accounted for other variables like age or body weight.

The connection between a patient's sex and the surgery's outcome is particularly notable. The data showed that women faced more than double the odds of having residual high pressure compared to men. This aligns with other studies suggesting that women with this condition may have a different biological makeup in their lung vessels, perhaps involving smaller, harder-to-reach blood vessels that the surgery cannot reach. However, the researchers are careful to note that the exact biological reason for this difference remains unknown and requires further study.

The finding about patients without a history of prior clots is perhaps the most surprising. Usually, doctors expect the disease to follow a clear path from a known clot to the chronic condition. Yet, in this group, those who developed the lung disease without a previous, documented clot were three times more likely to have high pressure after surgery. This suggests that these patients might have a different type of disease process, perhaps involving widespread changes in the tiny blood vessels that the surgeon cannot physically remove. Because this link is less established in medical literature, the researchers describe it as a new hypothesis that needs to be tested in other groups of people before it becomes a standard rule.

The third factor, the pressure level before surgery, acts as a straightforward measure of how much strain the heart was under. For every small increase in pressure before the operation, the chance of having high pressure afterward went up slightly. This confirms that the severity of the disease before the cut is a strong indicator of how much work remains for the heart and lungs afterward. It is not a single tipping point but a continuous scale where higher pressure means a harder road to recovery.

The researchers emphasize that these findings are not a crystal ball for predicting individual outcomes with perfect accuracy. The statistical model they built was good at spotting trends but not perfect enough to be used as a standalone rule for deciding who gets surgery. Instead, these three factors—being female, having no history of prior clots, and having higher initial pressure—serve as helpful warning signs. They suggest that doctors should pay extra attention to these patients after the operation, checking their heart and lung function more closely to see if they need additional therapies. By identifying these risks early, medical teams can better support patients who are most likely to struggle with the aftermath of the procedure, ensuring they get the right care at the right time.