March 24, 2021Frontiers in Cardiovascular MedicineOpen Access

Hemodynamic Profiles Before and After Surgery in Bicuspid Aortic Valve Disease—A Systematic Review of the Literature

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Why the study?

Bicuspid aortic valve disease presents unique management challenges pre- and post-operatively, prompting a review of 4D flow MRI literature after aortic valve and/or ascending aortic replacement.

Does aortic valve and/or ascending aortic replacement improve hemodynamic profiles assessed by 4D flow MRI in patients with bicuspid aortic valve disease?

Structured PICO

Does aortic valve and/or ascending aortic replacement improve hemodynamic profiles assessed by 4D flow MRI in patients with bicuspid aortic valve disease?

Population

447 participants across 14 studies with bicuspid aortic valve (BAV) disease undergoing aortic valve and/or ascending aortic replacement, assessed by 4D flow MRI.

Intervention

Aortic valve replacement (AVR) and/or ascending aortic replacement (ARR) (including mechanical, bioprosthetic, Ross procedure, and valve-sparing techniques)

Comparator

Pre-operative state, healthy controls, or alternative surgical techniques (e.g., mechanical vs. bioprosthetic)

Outcome

Hemodynamic changes including helical flow, flow displacement/angle, and wall shear stress (WSS) assessed by 4D flow MRIsurrogate

4D flow MRI demonstrates that mechanical AVR and the Ross procedure normalize aortic hemodynamics in BAV patients, while bioprosthetic valves and synthetic grafts maintain abnormal flow patterns that may drive future aortic remodeling.

Limitations

Low temporal resolution of 4D flow MRI (40-50 ms) could fail to capture the peak jet
Potential for variation in data depending on the equipment (1.5 vs. 3.0T MRI) and sequence used
Further variation can be introduced with the use of different post-processing platforms
No longitudinal 4D flow MRI data on BAV patents after valve-sparing aortic root replacement

Implication

Novel 4D flow MRI parameters may predict aortic dilatation in BAV; extends mechanistic insights but leaves clinical utility open pending validation.

Abstract

Bicuspid aortic valve (BAV) disease presents a unique management challenge both pre- and post-operatively. 4D flow MRI offers multiple tools for the assessment of the thoracic aorta in aortic valve disease. In particular, its assessment of flow patterns and wall shear stress have led to new understandings around the mechanisms of aneurysm development in BAV disease. Novel parameters have now been developed that have the potential to predict pathological aortic dilatation and may help to risk stratify BAV patients in future. This systematic review analyses the current 4D flow MRI literature after aortic valve and/or ascending aortic replacement in bicuspid aortic valve disease. 4D flow MRI has also identified distinct challenges posed by this cohort at the time of valve replacement compared to standard management of tri-leaflet disorders, and may help tailor the type and timing of replacement. Eccentric pathological flow patterns seen after bioprosthetic valve implantation, but not with mechanical prostheses, might be an important future consideration in intervention planning. 4D flow MRI also has promising potential in supporting the development of artificial valve prostheses and aortic conduits with more physiological flow patterns.