Residual Pulmonary Hypertension After Endarterectomy: How Common Is It?

Origin of Residual Pulmonary Hypertension

CTEPH is a rare and serious progressive disease based on the presence of fibrotically altered thrombi chronically obstructing the pulmonary arterial system. It is generally perceived as a rare complication of pulmonary embolism, with approximately 80% of CTEPH patients having it in their medical history. The disease is also associated with microvascular remodeling similar to the changes observed in pulmonary arterial hypertension (PAH), and these two factors likely contribute together to the pathogenesis of CTEPH.

We can achieve the removal of fibrotic thromboembolic material from the pulmonary vascular system through a procedure known as a pulmonary endarterectomy (PEA). This demanding surgical procedure, performed only in specialized centers, can lead to significant improvement in symptoms and prognosis, potentially completely curing CTEPH. However, cases of persistent or residual pulmonary hypertension post-surgery are not uncommon. A possible explanation for this phenomenon is the so-called two-compartment model described by Moser and Braunwald in 1973, where patients with operable CTEPH may develop secondary distal arteriopathy in small vessels in areas not directly obstructed by thrombi. Another possible mechanism is the incomplete removal of distally located thromboemboli. The estimated proportion of patients with persistent pulmonary hypertension varies, with literature suggesting a wide range of 5–35%.

What the Meta-Analysis Revealed: An Excellent but Not Perfect Method

Based on published studies discussing the outcomes of PEA, including residual/persistent/recurrent pulmonary hypertension, the authors evaluated data from 4868 CTEPH patients who underwent this surgical procedure. The monitored outcomes included the proportion of individuals with persistent pulmonary hypertension and changes in mean pulmonary artery pressure, pulmonary vascular resistance, and functional capacity measured by the 6-minute walk test.

According to the meta-analysis, the procedure led to a reduction in mean pulmonary artery pressure by approximately 21 mmHg (standardized mean difference [SMD] 1.75; 95% confidence interval [CI] –1.62 to 1.88; p < 0.00001) and a decrease in pulmonary vascular resistance by 561 dyn∙s/cm⁵ (SMD 1.64; 95% CI –1.58 to 1.70; p < 0.00001). The distance achieved in the 6-minute walk test improved by 96 meters (SMD –0.83; 95% CI –0.91 to –0.76; p < 0.00001). Persistent pulmonary hypertension post-PEA was found in 25% of patients.

Pharmacotherapy as Another Option

Pulmonary endarterectomy is the gold standard treatment for CTEPH, leading to immediate improvement in hemodynamic parameters and physical fitness in the majority of patients. However, up to a quarter of individuals continue to have pulmonary hypertension after this surgical procedure. These patients may benefit from specific vasodilatory therapy, which has the potential to improve hemodynamics and thereby treatment outcomes and prognosis. Other candidates for this pharmacotherapy are patients with inoperable CTEPH, for example, due to peripheral involvement.

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Sources:
1. Hsieh W. C., Jansa P., Huang W. C. et al. Residual pulmonary hypertension after pulmonary endarterectomy: a meta-analysis. J Thorac Cardiovasc Surg 2018; 156 (3): 1275−1287, doi: 10.1016/j.jtcvs.2018.04.110.
2. Jansa P., Ambrož D., Kuchař J. et al. Chronic thromboembolic pulmonary hypertension. Intervenční a akutní kardiologie 2016; 15 (4): 172−176.