Transcript Document

‘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.
[email protected]
Hypertrophic Cardiomyopathy
‘How I do’ : CMR in HCM
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
‘How I do’ : CMR in HCM
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
‘How I do’ : CMR in HCM
HCM – Histopathology
Myocyte Disarray
Here with some associated fibrosis
‘How I do’ : CMR in HCM
HCM and Fibrosis

In addition to
asymmetric hypertrophy,
there is often extensive
fibrosis
‘How I do’ : CMR in HCM
HCM: SAM + LVOTO
‘How I do’ : CMR in HCM
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
‘How I do’ : CMR in HCM
CMR Quantification
See the presentation ‘how I do’ LV volumes
Downloadable from www.scmr.org
‘How I do’ : CMR in HCM
HCM: Cine Imaging

The key questions to address are: -
1.
Presence, distribution, and severity of LVH and
RVH. LV/RV mass and wall thickness
2.
Extent of septal involvement
3.
Distribution of hypertrophy in the variant forms
of hypertrophic cardiomyopathy
‘How I do’ : CMR in HCM
Functional Assessment


Cine images are then acquired to determine if there is
SAM and LVOTO.
SSFP images with retrospective gating recommended
‘How I do’ : CMR in HCM
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.
‘How I do’ : CMR in HCM
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
‘How I do’ : CMR in HCM
Fibrosis imaging in HCM
Gd infarct imaging
HCM fibrosis imaging?
‘How I do’ : CMR in HCM
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
‘How I do’ : CMR in HCM
Fibrosis -not like IHD
Picro sirius red stains collagen red.
In-vivo vs exvivo match
‘How I do’ : CMR in HCM
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.
‘How I do’ : CMR in HCM
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.

‘How I do’ : CMR in HCM
Detection of Fibrosis: Inversion Recovery Sequence

Tips to confirm fibrosis and not artefact:
1.
Phase swap each slice
2.
If mid-wall enhancement is seen, ensure TI is optimal and if
need be, repeat the slice with a different TI
3.
Cross-cut through any areas of suspected mid-wall
enhancement
4.
If subendocardial enhancement is seen, reconsider the diagnosis
or assess if this reflects ‘bystander’ coronary disease
5.
It is common to see some fibrosis around the LVOT and at the
RV/LV septal insertion points
‘How I do’ : CMR in HCM
Assessment of Fibrosis
late enhancement in the septum reflecting fibrosis
‘How I do’ : CMR in HCM
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.
‘How I do’ : CMR in HCM
Other techniques: perfusion
Rest Perf
Late Gd
Perfusion defects in HCM – uncertain significance;
here matching enhancement
‘How I do’ : CMR in HCM
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
[email protected]
‘How I do’ : CMR in HCM