False lumen ejection fraction predicts growth in type B aortic dissection: preliminary results

Abstract

OBJECTIVES Current risk assessment strategies in type B aortic dissection are focused on anatomic parameters, although haemodynamic abnormalities that result in false lumen (FL) pressurization are thought to play a significant role in aortic growth. The objective of this study was to evaluate blood flow of the FL using 4D flow magnetic resonance imaging (MRI) and identify haemodynamic and anatomic factors that independently predict the rate of aortic growth. METHODS Patients with dissection of the descending thoraco-abdominal aorta (n = 18) were enrolled in a prospective observational study and underwent 4D flow MRI for haemodynamic assessment of the entry tear and FL. Anatomic parameters were obtained by magnetic resonance angiography and baseline computed tomography. False lumen ejection fraction (FL EF) was defined the ratio of retrograde flow rate at the dominant entry tear during diastole over the antegrade systolic flow rate. RESULTS The median aortic growth rate was 3.5 mm/year (interquartile range 0.5–8.1 mm/year). Entry tear peak velocity was lower in patients with enlarging aortic dimensions (95.5 ± 24.1 vs 128.1 ± 37.4 cm/s, P = 0.039). After adjusting for co-variates FL EF (β = 0.15, P = 0.004), baseline maximal aortic diameter (β = 0.37, P = 0.001) and the entry tear distance from the left subclavian artery (β = 0.07, P = 0.016) were significant predictors of aortic growth rate. CONCLUSIONS Beyond standard anatomic risk factors, FL EF is an independent predictor of aortic growth rate and may represent an intuitive, non-invasive method to estimate FL pressurization and improve patient-specific risk assessment in patients with type B aortic dissection.

False lumen pressure estimation in type B aortic dissection using 4D flow cardiovascular magnetic resonance: comparisons with aortic growth

“…The simplicity in derivation makes FLEF an attractive metric in clinical instances where the FL has a single dominant tear in the thoracic aorta, whereas v WERP may be better suited in scenarios with multiple or complex flap fenestrations/tears (as shown in previous in-silico work [ 25 ]. Regardless of the metric, our analysis underlines the pathophysiological importance of FL pressurization in TBAD growth, adding to the increasing number of studies highlighting its diagnostic role [ 10 – 13 , 18 , 24 , 33 ]. In reality, since both FLEF and FL ΔP max can be measured from the same 4D Flow acquisition, measurement of multiple parameters may be a complementary approach that lends additional diagnostic certainty in cases where pressurization assessments are concordant.…”

“…FLEF has been previously described in TBAD [ 18 ], with this metric describing the ratio between retrograde and antegrade flow through the dominant entry tear. FLEF is a regional and indirect measure of assessing FL pressurization.…”

“…Time-resolved three-dimensional phase-contrast cardiovacular magnetic resonance (4D Flow CMR) is a non-invasive technique that provides volumetric assessment of blood flow, and has been extensively applied to study aortic hemodynamics [ 18 – 23 ]. Recent 4D Flow CMR studies have also proposed ways of estimating FL pressurization and to predict growth in TBAD [ 18 – 20 , 24 ]. Burris et al [ 18 ] proposed FL ejection fraction (FLEF)—the ratio between retrograde and antegrade flow through the FL opening—as indicative of pressurization, linking FLEF to TBAD growth.…”

“…Recent 4D Flow CMR studies have also proposed ways of estimating FL pressurization and to predict growth in TBAD [ 18 – 20 , 24 ]. Burris et al [ 18 ] proposed FL ejection fraction (FLEF)—the ratio between retrograde and antegrade flow through the FL opening—as indicative of pressurization, linking FLEF to TBAD growth. Similarly, Ruiz Munoz et al [ 24 ] used 4D flow CMR to measure the maximum systolic deceleration rate (MSDR) in the FL as a marker of FL pressurization and found significant associations between MSDR and aortic growth rate.…”

Utility of 4D Flow MRI in Thoracic Aortic Diseases: A Literature Review of Clinical Applications and Current Evidence

“…11,54,55 This crucial finding indicates that flow dynamic abnormalities in the patent FL influence FL pressurization and degeneration, ultimately determining the late outcomes. 51,[56][57][58] Accordingly, flow-based risk stratification through imaging modality might enable clinicians to predict the expansion of FL more sensitively than the current morphology-based risk stratification, including a large initial diameter (> 40 mm), large primary entry (> 10 mm), or partially thrombosed FL. The characteristics of flow dynamics in the FL are complex and differ according to the location and size of the intimal tears.…”