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Emory CT CCR Investigators Acknowledged at STS Meeting

February 2017

Bradley Leshnower, MD, assistant professor of surgery, and Xiaoying Lou, MD, a second year resident in the integrated, six-year cardiothoracic surgery residency, received support and recognition for their work in Emory's Cardiothoracic Surgery Center for Clinical Research (CCR) at the 53rd Annual Meeting of the Society of Thoracic Surgeons (STS), held in Houston in January. The focus of the CCR is to develop and evaluate new procedures and technologies in cardiothoracic surgery to inform evidence-based practice.

Lou, whose CCR-based research is primarily mentored by Leshnower, received the European Association for Cardiothoracic Surgery (EACTS)/STS Award. This honor is presented to the first author of the top abstract presented during the meeting's combined EACTS/STS session. Lou's abstract, "The impact of TEVAR on long-term survival in Type B aortic dissection," examined the impact of thoracic endovascular aortic repair (TEVAR) in the acute phase of Type B aortic dissection (TBAD) on long-term survival compared to TEVAR and open surgery in the chronic phase of TBAD.

TBAD occurs secondary to a tear on the inner layer of the aorta distal to the left subclavian artery that allows blood to flow into the wall of the aorta, resulting in a separation of the different layers of tissue that comprise the aortic wall. The acute phase of TBAD occurs within the first 14 days of the initial diagnosis, while TBAD is considered in the chronic phase after three months.

TEVAR has revolutionized the treatment of TBAD, and represents a minimally invasive approach to treating patients with the condition. By covering the primary aortic tear, TEVAR directs all of the blood flow into the true lumen, expands it, and causes false lumen thrombosis and obliteration. TEVAR is the primary therapy for patients with acute TBAD complicated by ischemia and/or rupture, and a viable alternative to open surgery for patients with chronic TBAD who develop aneurysms.  

Lou and her co-authors, which included Leshnower as senior author, cardiothoracic surgeon Edward Chen, MD, vascular surgeon Yazan Duwayri, MD, and vascular surgery chief William Jordan, MD, conducted a retrospective review of Emory's aortic database from 2000-2016 and identified 398 TBAD patients. Eighty acute complicated TBAD patients underwent TEVAR, while the remaining 318 uncomplicated patients were initially treated with optimal medical therapy. In the chronic phase, 46% of patients failed medical management and required either open surgery (n=59) or TEVAR (n=87). The team found that despite having the highest mortality risk, complicated TBADs undergoing TEVAR in the acute phase had an improved long-term survival compared to patients receiving definitive medical therapy, open surgery, or endovascular therapy in the chronic phase. The authors concluded that TEVAR at the index hospitalization may confer a survival advantage and serve as optimal therapy for complicated and uncomplicated acute TBAD.

During the Thoracic Surgery Foundation (TSF) reception at the STS meeting, Leshnower was presented with the second installment of the TSF/Southern Thoracic Surgical Association (STSA) Research Grant he received in 2016 to fund his project, "The search for the optimal cerebral protection strategy during aortic arch replacement: A pilot study." Leshnower was the inaugural recipient of the grant, which the TSF and STSA established to support the research of an early-career cardiothoracic surgeon.

"Neurologic injury following cardiac surgery is a devastating complication that significantly impacts length of hospitalization, cost, and mortality," says Leshnower. "In this study, we are attempting to define the optimal neuroprotection strategy during aortic arch surgery."

Branches from the aortic arch supply blood to the brain and arms. Transverse hemiarch replacement, one of the most common methods of treating dissections or aneurysms that involve the proximal aortic arch, removes the lesser curve of the diseased aorta and replaces it with a Dacron graft. This procedure requires the use of hypothermic circulatory arrest, which alters the normal blood flow to the brain and incurs a significant risk of adverse neurologic events.  

The two primary strategies for cerebral protection during transverse hemiarch replacement are the traditional method of deep hypothermic circulatory arrest (DHCA) with retrograde cerebral perfusion (RCP), and the more contemporary approach of moderate hypothermic circulatory arrest (MHCA) with unilateral selective antegrade cerebral perfusion (uSACP). DHCA+RCP involves cooling the brain to <20°C on cardiopulmonary bypass, arresting circulation, and perfusing the brain with reversed blood flow via the superior vena cava. Circulation is also arrested with MHCA+uSACP, but the brain is cooled to a temperature range of 24°–28°C using cardiopulmonary bypass, and normal, forward blood flow to the brain is provided via the right axillary artery.    

DHCA+RCP and its use of deep hypothermia to suppress cerebral metabolism has been the standard of care for administering maximal brain protection, though its detrimental effects can include prolonged cardiopulmonary bypass, endothelial dysfunction, coagulopathy, and significant inflammation. While MHCA+uSACP may provide equivalent neuroprotection without these dangers, its impact and that of DHCA+RCP on such neurologic injury as stroke and neurocognitive function is unknown.  

"Cerebral protection strategies during arch surgery have been a research interest of mine since residency, and this project serves as an extension of my previous work," says Leshnower. "My hope is that this study will provide data that justifies the need for a multi-institutional, prospective, randomized trial of the neuroprotection strategies used during aortic arch surgery, and will provide clarity regarding the true incidence of neurologic injury following arch replacement."

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