Comparison of MR Tissue Phase Mapping and MR Feature Tracking in Children with Hypertrophic CardiomyopathyArleen Li, Alexander Ruh, PhD, Michael Markl, PhD, Joshua D. Robinson, MD, Cynthia K. Rigsby, MD

Background

• Hypertrophic cardiomyopathy (HCM)

– Common genetic CV condition – 1 in 500

– Hypertrophy (thickening) of LV wall, w/o dilation

• No evidence of other cardiac or systemic cause

– Associated with heart failure, atrial fibrillation, sudden death

How can we evaluate myocardial function in patients who have HCM?

Maron BJ, Maron MS. Hypertrophic Cardiomyopathy. Lancet 2003; 381: 242-55.Image: columbiasurgery.org/conditions-and-treatments/hypertrophic-cardiomyopathy-and-heart-failure

Background

• Myocardial function can be measured using strain or velocity in certain directions over course of a cardiac cycle

Taylor RJ et al. Myocardial strain measurement with feature-tracking cardiovascular magnetic resonance: normal values. European Heart Journal – Cardiovascular Imaging.2015; 16(8): 871-81. doi: 10.1093/ehjci/jev006

Image: 123sonography.com/ebook/left-ventricular-function

Background

• MR techniques that can be used to measure strain and/or velocity include:

• Tissue phase mapping 1

– Phase-contrast MRI sequence with 3D velocity encoding

• Feature tracking 2

– Post-processing of steady-state free precession (SSFP) cine images, via tracking of tissue voxels

1Jung B, Markl M, Foll D, Hennig, J. Investigating myocardial motion by MRI using tissue phase mapping. European Journal of Cardio-thoracic Surgery 2006; 29: 150-7.2Taylor RJ et al. Myocardial strain measurement with feature-tracking cardiovascular magnetic resonance: normal values. Euro Heart Journal – Cardiovasc Imag. 2015; 16(8):

871-81. doi: 10.1093/ehjci/jev0062

Background

• MR techniques have demonstrated reduced myocardial function (e.g. velocity, strain) in adults with HCM, even with normal LV ejection fraction1,2

• Changes in myocardial tissue structure are associated with elevated myocardial T1 relaxation times3,4

– Indicating diffuse myocardial fibrosis

• Performance of MR techniques that evaluate LV function has not been systematically evaluated in children

1Ennis DB et al. Assessment of Regional Systolic and Diastolic Dysfunction in Familial Hypertrophic Cardiomyopathy Using MR Tagging. Magn Reson Med. 2003; 50: 638-42.

2Wu LM et al. Hypertrophic cardiomyopathy and left ventricular hypertrophy in hypertensive heart disease with mildly reduced or preserved ejection fraction: insight from altered mechanics and native T1 mapping. Clin Radiology. 2017; 72(10): 835-43.

3Kellman P, Hansen MS. T1-mapping in the heart: accuracy and precision. J Cardiovasc Magn Reson. 2014; 16:2.4Dass S et al. Myocardial Tissue Characterization Using Magnetic Resonance T1 Mapping in Hypertrophic and Dilated Cardiomyopathy. Cardiovasc Imag. 2012; 5: 726-33.

Purpose

1) To compare two MR techniques, tissue phase mapping & feature tracking, in evaluating myocardial function in children with HCM.

2) To establish a relationship between myocardial function (via tissue phase mapping and feature tracking) & structural tissue abnormalities

(via T1 mapping) in children with HCM

Methods: Participants

• 17 HCM patients and 21 normal controls undergoing standard-of-care cardiac MRI (+tissue phase mapping, with consent) were prospectively recruited

– Excluded patients with:

• Other anatomical congenital heart diseases

• Genetic syndromes

• Neuromuscular disorders

• Coronary artery disease

• Hx of septal myectomy

• Atrial fibrillation

Methods: MR Techniques

• Tissue Phase Mapping– Phase-contrast MRI sequence

with 3D velocity encoding

– Short-axis images

• Base

• Mid-ventricle

• Apex

– Post processing

• In-house MATLAB tool

Methods: MR Techniques• Feature Tracking

– SSFP cine images

– Short-axis images

• Base

• Mid-ventricular

• Apex

– Long-axis images

• 4-chamber

• 3-chamber

• 2-chamber

– Post-processing

• Commercial cardiac analysis tool (TomTec)

• Obtained velocity values

Methods: Velocity Analysis

• Segmental LV myocardial velocities at peak systole& diastole were calculated by AHA 16-segment model

• Segmental velocities then averaged to global myocardial velocities

– Radial

– Longitudinal

Tissue Phase Mapping Feature Tracking

AHA 16-segment model

Methods: Additional Image Data

• Native T1 relaxation times

– Modified Look-Locker inversion recovery (MOLLI) short-axis images

• Maximum LV wall thickness

– SSFP cine images

Patient Demographics

HCM (n = 17) Controls (n = 21) p

Age 15.3 ± 3.7 15.6 ± 4.0 0.5

Female (%) 9 (53%) 10 (48%) --

Max. LV Wall Thickness (mm) 24 ± 9 8 ± 1 <0.001

LV Mass Index (g/m2) 91 ± 65 45 ± 10 <0.001

LV Ejection Fraction (%) 65 ± 8 57 ± 3 <0.01

Mean LV Native (Noncontrast) T1 Time (msec)

1049 ± 59 1000 ± 33 0.01

Results: Mean Global Peak Velocities in HCM vs. Controls

Results: Mean Global Peak Velocities in HCM vs. Controls

Results:Peak Global Diastolic Velocities vs. Native T1 Time

Results: Peak Global Diastolic Velocities vs. Max LV Wall Thickness

Conclusions

• Both MR tissue phase mapping and feature tracking show decreased diastolic myocardial velocity in HCM patients vs. controls

– Suggests impaired myocardial relaxation, despite normal LV ejection fraction

• Significant associations between impaired diastolic LV velocities & elevated T1 times

– Direct relationship between LV function decline and tissue structure abnormalities

• May be early indicator of disease

• May be helpful in multi-parametric HCM patient analysis

THANK YOU!

Special thanks to Haben Berhane, Michael Rose, Ryan Dolan, and Dr. Amanda Hauck for their help with this project.