May-Thurner anatomy (MTA) was found to be “very common” in the rare and progressive condition chronic thromboembolic pulmonary hypertension (CTEPH), in a new retrospective study of Temple University Hospital patients.
The findings are the first to shed light on the prevalence of the anatomical variation in patients with the chronic thromboembolic disease of the lungs.
The study was published Monday online ahead of the Sept. 13. issue of JACC: Cardiovascular Interventions, with authors led by Mohamad Al-Otaibi, MD, from the Lewis Katz School of Medicine at Temple University, Philadelphia.
CTEPH is a pulmonary vascular disease caused by inadequate dissolution of acute pulmonary embolism (PE), resulting in its fibrotic transformation with progressive microvascular remodeling and the development of pulmonary hypertension, the researchers noted. It is believed to affect between 1% and 9% of all patients with acute PE.
Risk factors include deep vein thrombosis (DVT), recurrent PE, malignancy, lupus anticoagulant phenomenon, antiphospholipid syndrome, ventriculoatrial shunts, uterine fibroids, hypothyroidism, elevated factor VIII, non-O blood group, inflammatory bowel disease, and splenectomy, the researchers added.
MTA is a seemingly rare anatomical variant characterized by compression of left common iliac vein by the overlying right iliac artery, leading over time to venous intimal scarring, blood flow stasis, and DVT. However, its prevalence in CTEPH has remained unknown.
The current study was, therefore, launched: a retrospective chart review of 148 patients referred to Temple University Hospital’s cardiac catheterization laboratory for the evaluation of CTEPH between January 2016 and June 2020 who underwent invasive venography performed at the time of pulmonary angiography.
MTA was identified in 44 of these patients (29.7%), the researchers found.
Factors associated with MTA were lower-extremity DVT (odds ratio [OR]: 3.5; 95% confidence interval [CI]: 1.58-7.8; P = 0.002), and left lower-extremity post-thrombotic syndrome (OR: 2.0; 95% CI: 0.98-4.1; P = 0.05).
Patients with MTA were also found to be more likely to undergo pulmonary thromboendarterectomy than those without MTA (79.5% vs 58.7%; P = 0.015).
“The presence of MTA may be a predictor of proximal CTEPH that is amenable to [pulmonary thromboendarterectomy],” the researchers said. “Our novel findings warrant further prospective multicenter [intravascular ultrasound]-based studies to verify our results and assess the risk for PE and CTEPH recurrence in patients with MTA.”
Identifying May-Thurner syndrome (MTS) could also lead to interventional treatment for some patients, which “may reduce the risk for recurrent venous thromboembolism,” the researchers said.
They stressed that MTA prevalence – while reportedly rare – could be underestimated because of a scarcity of pelvic vein imaging in patients with lower extremity DVT.
“MTA should be suspected in those patients with left lower extremity DVT or PTS,” they added.
In an accompanying editorial, Maciej Kostrubiec, MD, PhD, from the Medical University of Warsaw, Poland, said: “The presented report does not provide any final answer on MTA and MTS significance in CTEPH but certainly points out MTA as a possibly undervalued and overlooked factor altering the incidence, course, and management of patients with CTEPH.”
Al-Otaibi M, Vaidy A, Vaidya A, et al. May-Thurner Anatomy in Patients With Chronic Thromboembolic Pulmonary Hypertension: An Important Clinical Association. JACC Cardiovasc Interv 2021;14:1940-1946.
Kostrubiec M. May-Thurner Anatomy: An Undervalued Anatomical Variant in Patients With Chronic Thromboembolic Pulmonary Hypertension? JACC Cardiovasc Interv 2021;14:1947-1949.
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