When Not to Implant the Multilayer Flow Modulator: Lessons Learned From Application Outside the Indications for Use in Patients With Thoracoabdominal Pathologies

Abstract

To scrutinize registry data on thoracoabdominal repairs performed using the Multilayer Flow Modulator (MFM) outside the indications for use (IFU) and analyze the adverse outcomes. Of 380 patients from Europe registered in the MFM Global Registry after treatment for thoracoabdominal aortic aneurysm (TAAA) or dissection, 38 (10%) patients (30 men; median age 71 years, range 30-91) treated on a compassionate basis outside the IFU were analyzed. Thirteen patients had chronic Stanford type B dissection with aneurysmal dilatation >6 cm. There were 6 mycotic and 4 saccular aneurysms in addition to 15 primary TAAAs. The mean aneurysm diameter was 7.1 cm. Ten patients presented with rupture, and 23 patients had previous open or thoracic endovascular aortic repair (TEVAR). Although no death, paraplegia, stroke, or renovisceral compromise was documented during the initial hospital stay, technical success was zero. There were 31 (81.6%) cases in which there was failure to land the device in normal aorta. Other violations of the IFU included 12 with inadequate stent overlap and 11 cases involving a small MFM being deployed inside a larger one. Five of the 9 cases in which an undersized device was used resulted in a type I endoleak (failure mode I). During a mean follow-up of 10.0±6.9 months, all-cause mortality was 89.5% (34/38), of which 27 (71.1%) were aneurysm-related deaths. Overall survival, freedom from aneurysm-related death, and rupture-free survival estimates were 17.5%, 25.0%, 31.5%, respectively, at 18 months. There were 8 visceral branch complications; in all, 14 secondary endovascular interventions were required in 11 patients for endoleak (failure modes I and II) or stent foreshortening. No false lumen was completely thrombosed in the dissecting aneurysms. All aneurysms showed a mean sac growth rate of 0.12±0.16 cm/month. Factors having a significance influence on risk of aneurysm-related death included maximum aneurysm diameter (p=0.025, HR 1.37, 95% CI 1.04 to1.82), previous TEVAR (p=0.03, HR 2.44, 95% CI 1.10 to 2.08), and inadequate overlap between MFM devices (p<0.002, HR 4.02, 95% CI 1.70 to 9.49). There are clinical scenarios in which the MFM does not perform well. The MFM is not a solution for patients living on borrowed time and should not be used indiscriminately in patients in whom other modalities of aortic repair are not feasible. Its use must adhere to the IFU, and robust clinical data are required before constructing a randomized controlled trial.