Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Surgery

Supervisor

Valdis, Matthew

2nd Supervisor

Dubois, Luc

Co-Supervisor

3rd Supervisor

Chu, Michael W.A.

Co-Supervisor

Abstract

Background: Acute Type A aortic dissection (TAAD) patients who experience malperfusion syndrome (MPS) are at the greatest risk of major morbidity and mortality. However, the appropriate timing for open proximal aortic repair in the presence of MPS is still uncertain due to variations in clinical manifestations and diverse treatment approaches.

Methods: We conducted a comprehensive literature review to understand the importance of MPS in the setting of TAAD. Then, we conducted a national survey to understand the perception of cardiovascular surgeons across Canada and their approach for those patients. Furthermore, we performed a retrospective analysis of our local data to analyze the outcomes of TAAD with and without malperfusion syndrome from December 1999 to December 2021. Finally, we started a prospective pilot study to assess the feasibility and safety of using intravascular ultrasound (IVUS) to assess and early diagnose MPS in the setting of TAAD.

Results:The mortality of TAAD ranges from 17% to 31%, with a third of patients presenting with MPS. Mortality of TAAD patients increases significantly in the presence of MPS Specialized centers across the world have adopted new approaches to address malperfusion syndrome and have reported improved outcomes. From the national survey that we conducted, there is awareness of the significance of malperfusion syndrome in the setting of TAAD among the cardiac surgeons across Canada. From our local institution, the 30-day in-hospital mortality of TAAD is 13.6%. The mortality of patients with malperfusion is 36.2%, while without malperfusion is 6.2% (p

Conclusion: Adopting new approaches to address malperfusion syndrome in the setting of TAAD is critical to improving mortality and morbidity outcomes.

Summary for Lay Audience

Aortic dissection is a life-threatening condition that occurs when the internal layer of the aorta, a major artery that carries blood to all body organs, tears, causing the aortic wall layers to separate (dissect). This separation compromises blood flow to organs, leading to organ damage known as Malperfusion Syndrome. Despite repairing the aortic wall tear and restoring adequate blood flow through the true lumen, the presence of malperfusion syndrome remains a major risk factor associated with increased mortality rates, as well as long- and short-term damage to organs such as stroke, dead bowel, dialysis, or leg amputation.

To gain a better understanding of the disease and approaches taken by other centers worldwide, we conducted a comprehensive literature review. We also conducted a national survey of cardiovascular surgeons across Canada to analyze their understanding and approach to managing patients with malperfusion syndrome resulting from aortic dissection, including outcomes, deficits, and areas for potential improvement.

Furthermore, we reviewed the mortality and morbidity outcomes of acute aortic dissection cases previously managed at our center, London Health Sciences Center in London, Ontario, Canada. We focused on the presence of malperfusion syndrome and its effect on mortality and morbidity outcomes.

Finally, we are conducting a study to determine the feasibility of using Intravascular Ultrasound (IVUS) to assess in real-time and confirm any evidence of malperfusion syndrome after repairing the original aortic tear. IVUS is a small ultrasound wand attached to the top of a thin tube, inserted into the aorta from the femoral artery in the groin. This device takes pictures of the aorta and its major branches to identify problems with blood flow. Having this real-time and dynamic assessment helps identify malperfused organs before leaving the operating room, potentially allowing us to address malperfusion syndrome quickly and limit complications. Without this technique, identifying the problem can take several days after surgery, by which point irreversible complications may have developed.

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