‘How I do’ CMR in HCM Dr Sanjay Prasad, Royal Brompton Hospital London, UK. For SCMR August 2006 This presentation is posted for members of scmr as an educational guide – it represents the views and practices of the author, and not necessarily those of SCMR. s.prasad@rbht.nhs.uk

Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy: Clinical Aspects Characterized by myocyte disarray, hypertrophy, and interstitial fibrosis 90% of pts have familial disease 10% de novo mutations Increased risk of SCD Adult prevalence 1:500 (Autosomal Dominant) 1st degree-relatives -1:2 risk gene carrier

HCM: Diagnosis Unexplained hypertrophy Measured wall thickness exceeds 2SD for gender-,age-, and BSA-matched populations ≥ 1.5cm in absence of a recognized cause There may be associated systolic anterior motion of the mitral valve leaflets and outflow tract obstruction Multiple causative mutations in at least 10 different sarcomeric proteins Variable phenotype and clinical outcome Seidman et al 2002; Chien 2003

HCM – Histopathology Myocyte Disarray Here with some associated fibrosis

HCM and Fibrosis In addition to asymmetric hypertrophy, there is often extensive fibrosis

HCM: SAM + LVOTO ADD DCM Cine

CMR Evaluation of HCM The first important aspect is determining LV and RV volumes, ejection fractions, maximal wall thickness and mass We recommend the modified Simpson’s method rather than biplanar assessment since it makes no assumptions on cardiac morphology and is both more accurate and reproducible. After piloting the 4ch and VLA views, retrospectively gated gradient echo cine slices are taken from the base to apex Typically 7mm slices with a 3mm gap. Usually myocardial coverage is achieved in 9-10 slices

CMR Quantification See the presentation ‘how I do’ LV volumes Downloadable from www.scmr.org

HCM: Cine Imaging The key questions to address are: - Presence, distribution, and severity of LVH and RVH. LV/RV mass and wall thickness Extent of septal involvement Distribution of hypertrophy in the variant forms of hypertrophic cardiomyopathy

Functional Assessment Cine images are then acquired to determine if there is SAM and LVOTO. SSFP images with retrospective gating recommended

HCM: LVOTO Assessment In-plane followed by through plane breath-hold flow mapping is performed to look at the peak velocity at the outflow tract (red-bar) and at the level of the aortic valve.

Assessment of Fibrosis The presence of replacement fibrosis can be detected using the inversion recovery late enhancement technique following gadolinium-DTPA administration. After all, fibrosis is the main component of chronic MI which is visible with the late enhancement technique

Fibrosis imaging in HCM Gd infarct imaging HCM fibrosis imaging?

HCM – a wide variety of scar 2 patients. For the lower patient, scar is present and invisible without Gd-DTPA. Many patients have no detectable scar

Fibrosis -not like IHD Picro sirius red stains collagen red. In-vivo vs exvivo match

Detection of Fibrosis: Inversion Recovery Sequence Dosage of Gd-DTPA: 0.1-0.2mmol/kg At 0.1mmol/kg, images are usually acquired after about 5 minutes with a TI starting at ~340ms (every other heart beat). At 0.2 mmol/kg, scans are acquired after about 15 minutes with a TI starting at ~250ms.

HCM: Detection of Fibrosis LGE is predominantly seen in a patchy distribution and correlates with wall thickness. Unlike in IHD, the subendocardium is not necessarily affected. Unlike DCM, the distribution is typically more diffuse and not specific to mid-wall circumferential fibres.

Detection of Fibrosis: Inversion Recovery Sequence Tips to confirm fibrosis and not artefact: Phase swap each slice If mid-wall enhancement is seen, ensure TI is optimal and if need be, repeat the slice with a different TI Cross-cut through any areas of suspected mid-wall enhancement If subendocardial enhancement is seen, reconsider the diagnosis or assess if this reflects ‘bystander’ coronary disease It is common to see some fibrosis around the LVOT and at the RV/LV septal insertion points

Assessment of Fibrosis late enhancement in the septum reflecting fibrosis

RV insertion point enhancement 2 spots of enhancement at RV insertion points The 3rd point is artefact – Present AP phase encoding, disappears head-foot. This is artefact ghosting across the image.

Other techniques: perfusion Rest Perf Late Gd Perfusion defects in HCM – uncertain significance; here matching enhancement

Summary Evaluate function, volumes, maximal wall thickness, distribution of hypertrophy and overall mass index. Flow mapping to assess LVOTO Presence of fibrosis important using inversion-recovery Gd-DTPA s.prasad@rbht.nhs.uk