Valvular Heart Disease

1347966 - Novel 4D Flow Hemodynamic Signature Index (HSI) of mitral regurgitation burden associates with cardiac dysfunction independent of regurgitation severity grading

Thursday, January 26, 2023

1:00 PM – 2:00 PM

Location: Pacific Jewel

Presenting Author(s)

Mohammed Elbaz, PhD

Assistant Professor
Northwestern University
Chicago, Illinois, United States

Primary Author(s)

TN

Thara Nallamothu, BA

Graduate Student
Northwestern University, United States

Co-Author(s)

Aakash Gupta, MD

Radiology Resident Physician
Stanford University
Chicago, Illinois, United States
PG

Philip Greenland, MD

Professor of Preventive Medicine (Epidemiology) and Medicine (Cardiology)
Northwestern University
Chicago, Illinois, United States

Background: Accurate assessment of mitral regurgitation (MR) burden on cardiac dysfunction is crucial for early intervention and management of MR¹. Current MR evaluation relies on severity grading based on MR volume. However, this grading ignores the MR-induced complex left atrial (LA) flow dynamic changes (jets, vortices, heterogeneous flow). Therefore, potentially under-evaluating MR burden on cardiac dysfunction. A novel 4D Flow CMR hemodynamic signature index (HSI) was recently proposed to quantify composite 4D flow alterations in the entire LA. HSI derives the patient’s unique 4D flow CMR profile (signature) by interrogating millions of vector associations^2,3. This study aimed to assess the new 4D HSI marker as a novel comprehensive index of MR burden by testing its association with MR severity grading and cardiac function in MR patients.

Methods: This study included 124 subjects who underwent 4D Flow: 73 healthy controls and 51 MR patients. The patients were prospectively recruited based on evidence of MR on echocardiography within 3 months from CMR (Fig. 1a). Per published methods (Fig. 1b), the 4D HSI was computed from the entire LA flow by encoding the unique profile of 1.9±0.7 million vector co-disparities in the LA over entire systole (3D+time)^2,3. We tested the association of the HSI with ordinal MR severity (CMR grading) and cardiac function parameters: LV stroke volume (SV), LV cardiac output (CO), LV ejection fraction (EF).

Results: The HSI index was significantly higher in Moderate MR vs. Trivial MR (p < 0.001), Mild MR (p=0.002), and healthy controls (p < 0.001, Fig. 2a). The HSI correlated positively with MR severity (ρ=0.51, p< 0.001, Fig. 2a) as well as cardiac function: SV (ρ=0.42, p=0.003; Fig. 3a), CO (ρ=0.51, p< 0.001; Fig. 3b), EF (ρ=0.36, p=0.009; Fig. 3c). In linear regression, the HSI index associated positively with CO (p=0.005, Fig. 3d) and EF (p=0.01, Fig. 3e) independent of MR severity, age, and gender. Fig. 2b shows example of 2 patients with the same MR severity grading but a 5-fold difference in the HSI burden.

Conclusion: This study demonstrated that the novel 4D HSI metric of LA 4D flow abnormalities correlated with MR severity grading and associated with cardiac dysfunction (EF, CO) independent of MR severity grading. These results suggest the HSI as a potential novel marker of MR burden. As opposed to MR volume alone used in MR severity grading, the HSI quantifies the entire complex flow dynamics burden in the LA (3D+time) with higher HSI values indicating higher flow alteration (burden) vs. controls. The HSI —but not MR severity— associated with EF, suggesting the HSI index of MR burden may be a more sensitive marker of cardiac dysfunction. Future studies are needed to assess potential prognostic value of the 4D flow HSI index.