Monday, June 1, 2015

Thoracic Aortic Endografts

Thoracic endovascular aortic aneurysm repair, or TEVAR, has been implemented for a range of aortic pathologies, including traumatic tear, degenerative aneurysm of the aorta, and acute and chronic dissection of the thoracic aorta (1). TEVAR has been used more often than open surgery since its first introduction in the late 1990s, as it is less invasive, and several studies have demonstrated early safety and utility advantages. However, there are limited data to address concerns about the long-term durability of the technique.

Richard P. Cambria, MD, chief of Vascular and Endovascular Surgery at the Massachusetts General Hospital Fireman Vascular Center and co-director of the Thoracic Aortic Center, and his team have conducted trials on various TEVAR devices for several different aortic diseases, evaluating long-term outcomes as well as short-term mortality and other safety and efficacy outcomes.

Site of TEVAR Implementation

Site of TEVAR Implementation
Anatomic principles of acute type B dissection must be considered in stent graft repair. TEVAR devices are fitted at the proximal seal zone, where the endograft affixes to aortic tissue. That seal zone is usually found in the mid and distal aortic arch.
Source: Richard P. Cambria, MD

TEVAR for Descending Thoracic Aortic Aneurysms: A Five-Year View

In 2014, Dr. Cambria led a team that published the results of a five-year international study that compared TEVAR with open surgical repair for descending thoracic aortic aneurysms and large ulcers. The results were published in the Journal of Vascular Surgery (2). The five-year mortality rate was similar, at 37%, for both patients treated with TEVAR and those treated with open surgery. However, aneurysm-related mortality was significantly lower (5.9%) with TEVAR than with open surgical repair (12%). No ruptures of treated aneurysms were reported in either group. Severe morbidity was also significantly lower in the TEVAR group, at 21% compared with 39% for open surgical repair. And secondary intervention rates were similar for both groups. This study confirmed that using TEVAR to treat anatomically suitable descending thoracic aortic aneurysms and ulcers is a safe and effective alternative to open surgical repair.

Outcomes for Traditional Surgical Treatment vs. Endovascular Repair

Outcomes for Traditional Surgical Treatment vs. Endovascular Repair
Kaplan-Meier estimate of freedom from severe morbid events for both endovascular treatment group and open surgical control group. Vertical lines represent 95% confidence intervals. TEVAR patients have fewer major complications.
From Matsumura, Jon S., Germano Melissano, Richard P. Cambria, Michael D. Dake, et al. “Five-Year Results of Thoracic Endovascular Aortic Repair With the Zenith TX2.” Journal of Vascular Surgery, vol. 60, no. 1 (July 2014): 1-10.

Evaluating a Conformable TEVAR Device for Acute Complicated Type B Dissection

In acute complicated type B dissection, treatment with TEVAR may address rupture or malperfusion, as well as prevent the dissection from becoming a more complex aneurysm over time. Dr. Cambria and his team recently completed a multicenter trial, with the results soon to be published (3), of the use of a conformable TEVAR device in acute complicated type B dissection where all patients had rupture, malperfusion or both. The device was engineered specifically for some of the anatomical and clinical features referable to acute dissection. In the 50 patients treated in the trial, the study authors achieved a 30-day all-cause mortality of 8%. Historically, this category of patients has had a 30-day mortality of 30%, says Dr. Cambria, and the objective performance criteria is a 30-day mortality of 10%. The one-year survival rate from the study was 88%; the two-year survival rate was 85%. That trial was the basis for the September 2013 FDA approval of the conformable TEVAR device to treat type B dissection, the first such approval.

Dr. Cambria explains that the device has been engineered to make it more conformable at the proximal seal zone. The use of TEVAR devices for aortic dissection has typically been limited by the anatomy and aortic fragility at the proximal seal zone, where the thoracic endograft affixes to normal aortic tissue. In type B dissection, that seal zone is usually found in the mid and distal aortic arch.

Generating More Long-Term Outcome Data for Type B Dissection

Currently, there is FDA approval for two TEVAR devices, soon to be three. In conjunction with the Society for Vascular Surgery, Dr. Cambria is the chair of a national study committee that, with the FDA, is conducting a five-year study of clinical results with TEVAR in the treatment of acute and chronic type B dissections. The study will enroll 200 patients with acute type B dissection and 200 patients with chronic type B dissection, all treated with TEVAR, and follow them for five years.

The study will assess 30-day mortality as well as long-term efficacy, including the percentage requiring secondary procedures or additional interventions. The goal is to quantify the success of TEVAR technology in preventing the primary late complication of dissection—the formation of an aneurysm requiring complex open surgery.

References

(1) Cambria, Richard P, Robert S Crawford, Jae-Sung Cho, Joseph Bavaria, et al. "A Multicenter Clinical Trial of Endovascular Stent Graft Repair of Acute Catastrophes of the Descending Thoracic Aorta." Journal of Vascular Surgery, vol. 50, no. 6 (December 2009): 1255-64.

(2) Matsumura, Jon S, Germano Melissano, Richard P Cambria, Michael D Dake, et al. "Five-Year Results of Thoracic Endovascular Aortic Repair With the Zenith TX2." Journal of Vascular Surgery, vol. 60, no. 1 (July 2014): 1-10.

(3) Cambria, Richard P, Mark F Conrad, Alan H Matsumoto, Mark Fillinger, et al. “Conformable Stent Graft for the Treatment of Acute, Complicated Type B Dissection: Multicenter Clinical Trial.” Journal of Vascular Surgery, (2015, in press).

Contributor

  • Richard P. Cambria, MD
    Chief of Vascular and Endovascular Surgery
    Fireman Vascular Center
    Co-Director, Thoracic Aortic Center
    Massachsuetts General Hospital
    Robert R. Linton, MD, Professor of Vascular and Endovascular Surgery
    Harvard Medical School


This article first appeared in the Spring 2015 issue of Advances at Mass General.

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