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Proximal Aortic Longitudinal Strain Predicts Aortic Events in Marfan Syndrome
Study Questions:
Does strain of the proximal aorta, as assessed by cardiac magnetic resonance (CMR), predict aortic root dilation rate and aortic events in patients with Marfan syndrome?
Methods:
Children and adults with Marfan syndrome, diagnosed as per the original Ghent criteria, and maximum aortic root diameter <45 mm, were prospectively enrolled at two Spanish centers. Exclusion criteria were prior aortic dissection, cardiac surgery, bicuspid aortic valve, and grade III-IV aortic regurgitation. All patients were treated with losartan or atenolol at maximally tolerated doses. Each subject underwent CMR at baseline and at study conclusion. Aortic circumferential and longitudinal strain and distensibility were calculated using specialized software, from double-oblique steady-state free precession (cine) images. Aortic valve displacement on two-dimensional images in multiple planes was coregistered to create a time-resolved three-dimensional projection. Longitudinal strain was calculated as (aortic valve displacement along the centerline)/(proximal aorta length) – i.e., ascending aortic stretch during systole. Clinical endpoints were aortic root diameter growth rate and aortic events, defined as dissection or aortic surgery.
Results:
The study population included 117 patients (42% male, mean age 25.3 years, 27% age <18 years). Mean aortic root Z-score was 2.83 ± 1.42. Mean follow-up duration was 85.7 months. Mean aortic root dilation rate was 0.62 ± 0.65 mm/year. Aortic dissection occurred in 4 patients (3.4%), and 15 patients (13%) underwent surgical aortic root replacement. Mean longitudinal strain in patients was 8.7 ± 3.6%, as compared with 14.8 ± 3.9% in 21 healthy volunteers. In a multivariable model including age, body surface area, and baseline aortic root diameter, longitudinal strain was independently and negatively associated with aortic root growth (B = -0.346, 95% confidence interval, -9.769 to -2.713; p = 0.001) – i.e., less aortic stretch was associated with progressive aortic root dilation. Circumferential strain and distensibility were not significantly associated with aortic root growth. In receiver-operating characteristic analysis, area under the curve for a multivariable model including aortic diameter, longitudinal strain, and age was 0.952, as compared to 0.800 for diameter alone and 0.739 for longitudinal strain alone. A cutoff value of 7.7% for longitudinal strain would result in 80% sensitivity and 58% specificity for prediction of aortic events.
Conclusions:
Longitudinal ascending aortic strain is negatively associated with progressive aortic root dilation among patients with Marfan syndrome. Adding longitudinal aortic strain to aortic diameter measurements may enhance risk prediction in this population.
Perspective:
These findings provide support for the idea that aortic stiffness is associated with greater risk of progressive aortic dilation, as reported in prior CMR and echocardiographic studies among patients with and without Marfan syndrome. The authors used steady-state free precession cine CMR images, which are standard in CMR protocols for aortic imaging, though specialized software was employed to determine strain and distensibility values. One limitation of this study was the very low rate of the only “hard” endpoint, aortic dissection. The patient population was somewhat heterogeneous, as genotyping was not required (although a majority of patients were positive for the FBN-1 mutation), and both children and adults were included. Validation of these findings in a larger cohort, as well as verification of normal aortic strain values, will be needed before aortic longitudinal strain assessment can be recommended in clinical practice.
Clinical Topics: Cardiac Surgery, Cardiovascular Care Team, Congenital Heart Disease and Pediatric Cardiology, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Valvular Heart Disease, Vascular Medicine, Aortic Surgery, Cardiac Surgery and CHD and Pediatrics, Cardiac Surgery and Heart Failure, Cardiac Surgery and VHD, Congenital Heart Disease, CHD and Pediatrics and Imaging, Echocardiography/Ultrasound, Magnetic Resonance Imaging
Keywords: Aneurysm, Dissecting, Aortic Diseases, Aortic Valve Insufficiency, Atenolol, Body Surface Area, Diagnostic Imaging, Dilatation, Echocardiography, Genotype, Heart Defects, Congenital, Heart Valve Diseases, Losartan, Magnetic Resonance Imaging, Magnetic Resonance Imaging, Cine, Marfan Syndrome, Mutation, Systole, Vascular Diseases, Vascular Stiffness
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