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When to Intervene in Aortic Dissection
The optimal treatment strategy for patients with uncomplicated type B aortic dissection is unclear.
Aortic dissections are classified by severity: The most severe usually call for immediate surgery, and the least severe are considered to be manageable with medication. However, uncomplicated type B aortic dissections represent a middle ground around which there is little consensus. Some studies have suggested that intervention with thoracic endovascular aortic repair confers better long-term survival than medical management alone in these patients, but other studies are less conclusive, and most studies have been small. There is more agreement on what treatment goals should be in terms of heart rate targets, BP targets and other factors.
Cardiology Today’s Intervention spoke with three experts in this area — Frank R. Arko, MD, Michael D. Dake, MD, and Mark K. Eskandari, MD, FACS— for their insights on how best to manage these patients.
What is the best way to treat patients with uncomplicated type B aortic dissection?
Frank R. Arko, MD
Patients with type B aortic dissection often present as a spectrum of acute aortic syndromes, including intramural hematoma, penetrating aortic ulcers, aortic dissection and aneurysms. Type B aortic dissections begin distal to the left subclavian artery. They present as uncomplicated or complicated. Uncomplicated is without any visceral ischemia, renal, spinal cord or lower extremity ischemia. These patients in the immediate setting are best managed with optimum medical therapy, which is called anti-impulse therapy. The main line of therapy is first to decrease the resting heart rate to less than 60 bpm, followed by attempting to maintain a systolic BP of less than 120 mm Hg.
TEVAR with a stent graft is often limited initially to treating those with complicated type B dissections to improve the flow in the true lumen. For those with uncomplicated type B dissections, TEVAR can play a role to improve the long-term survival of these patients that typically occurs after 3 years of optimum medical therapy. TEVAR will also improve aortic remodeling and limit the risk for aneurysm expansion. There appears to be a trend in treating patients with acute type B uncomplicated dissections in the subacute phase for this reason. However, this is best managed at true dedicated multidisciplinary aortic centers.
Michael D. Dake, MD
Today, there is general recognition that the natural history of uncomplicated type B aortic dissection for the majority of patients is not benign, with progression of disease and aortic enlargement during the initial years after diagnosis. In the absence of close follow-up and imaging surveillance, it is not uncommon to also observe aortic rupture during the first 5 years.
In addition, there is increasing awareness by interventionalists that management of initially uncomplicated type B dissection with TEVAR within the first few months after diagnosis is technically easier and more effective than waiting for chronic aneurysm formation, when endovascular options are challenging and often more complicated.
Consequently, there is a current trend toward lowering the threshold for early treatment of patients with uncomplicated type B dissection. Initial experience focused on selecting for TEVAR those patients with high-risk features for progression. However, given the predictable course of disease evolution despite optimal medical therapy, some authorities now advocate early TEVAR (2 to 8 weeks after diagnosis) in all patients with initially uncomplicated type B dissection except those with certain underlying conditions or anatomic features that make TEVAR placement unsuitable or risky.
Mark K. Eskandari, MD, FACS
Management of acute type B thoracic aortic dissections has significantly evolved due to the introduction of advanced endovascular therapies, particularly aortic stent grafting. When thinking about this specific topic, it is important to clearly define what an uncomplicated acute type B aortic dissection actually represents. Anatomically, this is an acute dissection — intimal disruption — involving the proximal descending thoracic aorta beyond the origin of the left subclavian artery. Clinically, it is defined as uncomplicated if there is no evidence of active bleeding (rupture) or end organ malperfusion. Manifestations of poor end organ perfusion include paralysis, intestinal ischemia, renal failure or lower limb ischemia resulting from compromised arterial flow related to the dissection. Some practitioners also include intractable pain, which is quite common among all patients with acute aortic dissections and is best managed with medical therapy. Lastly, radiographic findings of an associated aneurysm related to the dissection as well as the presence of a dissection in the ascending aorta or aortic arch must also be considered when deciding the best mode of therapy.
Currently, first-line therapy for an uncomplicated type B aortic dissection is prompt admission to an intensive care unit setting, radiographic confirmation of the dissection — preferably with a contrast-enhanced CT scan — and careful titration of IV medications to lower the systolic BP with a goal of less than or equal to 120 mm Hg, usually starting with a beta-blocker. Typically, this will result in improvement in pain associated with the dissection. If the patient responds to IV medical therapy, they are then transitioned to oral BP medications with interval imaging and clinical assessment during the index hospitalization. After discharge, surveillance imaging is recommended since it is known that 50% to 70% of patients treated medically in the acute phase are at risk for late aneurysm formation over the next decade.
Failure to respond to medical therapy or progression of ischemic or bleeding complications requires prompt surgical therapy, including aortic stent graft repair, surgical revascularization and/or open aortic repair. Additionally, there exist high-risk radiographic features which identify a subgroup of patients that may benefit from early aortic stent graft repair in the setting of an uncomplicated type B aortic dissection due to the high likelihood of early or late complications. These imaging findings include a total aortic diameter of at least 44 mm, false lumen size of at least 22 mm, and/or a primary entry tear of at least 10 mm.
In summary, the first-line therapy for an acute uncomplicated type B aortic dissection is optimal in-patient medical therapy. Failure to respond to medical therapy, progression to a complicated dissection, or presence of high-risk radiographic features are an indication for intervention typically with aortic stent graft repair of the primary entry tear. The objective is to re-expand the true lumen, improve end organ flow, and diminish or obliterate false lumen flow. While this remains a controversial topic, a prospective randomized trial will help further clarify the exact indications for aortic stent graft repair among patients with an uncomplicated type B aortic dissection. – by Erik Swain
- For more information:
- Frank R. Arko, MD, is chief of vascular and endovascular surgery, co-director of the Center for Aortic Disease and professor of cardiovascular surgery at Sanger Heart & Vascular Institute, Atrium Health. He can be reached at farkomd@gmail.com.
- Michael D. Dake, MD, is Thelma and Henry Doelger Professor of Cardiovascular Surgery and medical director of the catheterization and angiography laboratories at Stanford Health Care. He can be reached at Falk Cardiovascular Research Center, 300 Pasteur Drive, Stanford, CA 94305.
- Mark K. Eskandari, MD, FACS, is the James S. T. Yao Professor of Vascular Surgery, chief and program director of the division of vascular surgery and professor of surgery, radiology and medical education at Northwestern University Feinberg School of Medicine. He can be reached at meskanda@nm.org.
Disclosures: Arko reports he consults for and receives research grants from Medtronic and W.L. Gore & Associates, and is principal investigator for numerous studies of aortic grafts. Dake reports he consults for Cook Medical and serves as a medical adviser to W.L. Gore & Associates on unrelated topics. Eskandari reports he consults for Prairie Education, Research Cooperative, Silk Road Medical and W.L. Gore & Associates.