CMR-Flow

1337323 - 4D Flow MRI-derived Peak Wall Shear Stress in the Ascending Aorta in Patients with Sigmoid Subtype Hypertrophic Cardiomyopathy

Friday, January 27, 2023

10:20 AM – 11:00 AM

Location: Pacific Jewel

Presenting Author(s)

TG

Tomas V. Gonzalez, MD

Radiology Resident
Mayo Clinic
Rochester, Minnesota, United States

Primary Author(s)

TG

Tomas V. Gonzalez, MD

Radiology Resident
Mayo Clinic
Rochester, Minnesota, United States

Co-Author(s)

DB

Daniel R. Burczak, MD

Cardiology Fellow
Mayo Clinic, United States
JG

Jeffrey B. Geske, MD

Professor of Medicine
Mayo Clinic
Rochester, Minnesota, United States
SO

Steve R. Ommen, MD

Professor of Medicine
Mayo Clinic, United States
Jeremy D. Collins, MD

Professor of Radiology
Mayo Clinic
Rochester, Minnesota, United States
Prabhakar Rajiah, MD

Professor of Radiology
Mayo Clinic
Rochester, Minnesota, United States
Christopher J. Francois, MD

Professor of Radiology
Mayo Clinic
Rochester, Minnesota, United States

Background: Adults with hypertrophic cardiomyopathy (HCM) have increased aortic wall stiffness, which is associated with the degree of myocardial fibrosis¹ and predictive of exercise capacity². Wall shear stress (WSS) reflects the longitudinal frictional force exerted on the vessel endothelium by the flow of blood. In this study, we examined the relationships between ascending aorta 4D-flow MRI derived peak WSS (pWSS) and vessel circumference and other common clinical and imaging characteristics in patients with sigmoid subtype of HCM.

Methods: Sigmoid subtype HCM patients that underwent CMR and 4D-flow MRI were retrospectively identified according to an IRB-approved, HIPAA-compliant protocol. Patients that had septal reduction therapy were excluded. Patient age, sex, left ventricular ejection fraction (LVEF), maximal wall thickness, presence of late gadolinium enhancement (LGE), systolic anterior motion (SAM) of the mitral valve and left ventricular outflow tract obstruction (LVOTO) were recorded. Maximal vessel diameter on the magnitude 4D-flow MRI images and pWSS were collected in the proximal (pAAo), mid (mAAo) and distal (dAAo) ascending aorta using commercially available software (Arterys, v29.01). Data were analyzed using IBM SPSS Statistics (version 27). Continuous variables were expressed as median and interquartile range. Continuous variables were compared using the Mann-Whitney test or Kurskal-Wallis test. The Bonferroni correction was applied when appropriate, otherwise a p-value of < 0.05 was considered statistically significant.

Results:

In total, 44 patients were included. Median age was 59.5 years (IQR = 48.3 - 68). 40.9% (18/44) were female. Median maximal left ventricular wall thickness = 18 mm (IQR = 16.9 – 21.1). Median LVEF = 60 mL (IQR = 57.3 – 65). 72.7% had LGE. 72.7% had LVOTO. The median pWSS in the pAAo, mAAo and dAAo were 75.5 cPa (IQR = 66.3 – 93.8), 69 cPa (IQR = 60 – 86), and 59 cPa (IQR = 47.5 – 72), respectively. The median maximal vessel diameter in the pAAo, mAAo and dAAo were 35.3 mm (IQR = 32.2 – 37.5), 37.6 mm (IQR = 34.8 – 40), and 35.1 mm (IQR = 33.9 – 37.1), respectively.

Significant differences in pWSS (p = 0.000) and maximal vessel diameter (p = 0.004) between the pAAo, mAAo and dAAo were found. pWSS was higher in the mAAo when compared to the dAAo (p = 0.007) and higher in the pAAo when compared to the dAAo (p = 0.000). The maximal vessel diameter was larger in the mAAo when compared to the pAAo (p = 0.003) and dAAo (p = 0.009). There was no significant difference in pWSS at any aortic level when comparing presence of SAM of the mitral valve, presence of LGE, LVOTO or ventricular thickness above or below the median.

Conclusion: Patients with sigmoid subtype HCM demonstrated significant differences in 4D-flow derived pWSS and maximal vessel diameter along the ascending aorta. Interestingly, we observed no difference in pWSS between HCM patients with or without SAM, LVOTO, LGE or those with ventricular thickness above or below the median.