Final five-year results from the STABLE I feasibility study presented at SVS VAM

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STABLE I
Joseph Lombardi

Five-year follow-up data from STABLE I, a global feasibility study of the Zenith Dissection Endovascular stent (Cook Medical), were presented by Joseph Lombardi (Cooper University Health Care, Camden, USA) at the Society for Vascular Surgery’s Vascular Annual Meeting (SVS VAM; 20–23 June, Boston, USA). In his presentation, Lombardi highlighted the need for “commitment to long-term management of type B aortic dissection” and the risk of aortic growth following thoracic aortic endovascular repair (TEVAR).

The study concludes follow-up for the feasibility study, which preceded the STABLE II study. At the 2016 VAM meeting, Lombardi reported initial outcomes of the second trial, saying “These preliminary results from the STABLE II study appear favourable in terms of clinical and anatomical outcomes for the treatment of acute chronic type B aortic dissection.”

STABLE I prospectively enrolled 86 patients at centres in the USA, Europe and Australia in the years 2007–2012. Of those patients, 89% were followed out to five years with clinical an CT follow-up. The study included patients with type B aortic dissection who required surgical intervention or were not responding well to medical treatment within 90 days of symptom onset. The primary endpoint of 30-day mortality was 4.7% (4/86), with three deaths following acute dissection (5.5%, 3/55) vs. one following non-acute dissection (1/31).

For TEVAR in treatment of complicated type B aortic dissection, Lombardi stated the management goals include prompt diagnosis, alleviation of malperfusion and containment of rupture, maximising false lumen thrombosis and minimising long-term complications. The Zenith stent used in the STABLE trials is a composite device design, combining a proximal covered stent graft with a bare metal stent.

“Complete false lumen thrombosis in the thoracic aorta increased over time and was observed in 74% of acute and 59% of non-acute patients at five years”, Lombardi et al write in their abstract, published in the Journal of Vascular Surgery. “From before the procedure through five years, there was an overall increase in true lumen diameter and concomitant decrease in false lumen diameter in both acute and non-acute patients at the level of the largest diameter in both the thoracic and abdominal aorta. At five years, 66% of acute and 81% of non-acute patients exhibited either a stable or shrinking transaortic diameter in the thoracic aorta; 52% of acute and 24% of non-acute patients experienced growth in trans-aortic diameter in the abdominal aorta.”

Commenting on the outcomes at the VAM in Boston, Lombardi said aortic remodelling was observed within and beyond the stent-grafted segments in both acute and non-acute dissections. He also stressed that aortic growth after TEVAR for type B aortic dissection is “very real, and may be more prevalent in patients treated in the acute phase”, as well as the importance of long-term commitment to managing type B aortic dissection.

At five years, endpoints included freedom from all-cause mortality (80%±6%), freedom from dissection repair-related mortality (84%±6%) and freedom from rupture (92%±4%). “Twenty-five patients underwent secondary intervention through five years,” Lombardi added, 17 of which were acute. Freedom from secondary interventions in both groups was 66%±8% at five years.

“Overall, the acute and nonacute cohorts from the feasibility study appeared to respond similarly to treatment,” Lombardi et al conclude in their abstract, “demonstrating similar clinical outcomes and favourable aortic remodelling in the thoracic and abdominal aorta.”

Reviewing the initial 30-day outcomes for STABLE I acute dissection patients, Lombardi noted at the VAM: “When we compare our data to the pooled SVS dataset by White et al in 2011, and also the pooled results from a meta-analysis on TEVAR by Fattori et al [2013], what strikes you initially is the low mortality rate [of the STABLE I acute cohort] in comparison, and also the low paraplegia rates with the use of this combination system.” The mortality rates of the pooled datasets were 10.6% and 10.2% for White et al and Fattori et al, respectively, as compared to the STABLE I study’s 5.5% mortality at 30 days. The paraplegia rates at 1.8% were indeed also significantly lower in comparison to White et al (9.4%; paralysis or paraparesis) and Fattori et al (4.2%; 30-day or in-hospital spinal cord ischaemia) data. The non-acute group similarly showed lower mortality rates in the STABLE I study ( 3.2% vs. 7.1% and 6.6%, respectively), but no significant difference in paraplegia rates (0% vs. 0% and 1.5%, respectively).

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