Assessment of Restrictive Cardiomyopathy


From the British Society of Echocardiography Education Committee: Lead Authors: Dr Daniel Knight, Dr. K. Patel, Dr. C. Whelan. Education Committee: Dr Rick Steeds (Chair), Dr Allan Harkness, Dr Richard Jones, Dr Prathap Kanagala, Dr Guy Lloyd, Dr Thomas Mathew, Dr Kevin O'Gallagher, Dr David Oxborough, Dr Bushra Rana, Dr Liam Ring, Julie Sandoval, Gill Wharton, Dr Richard Wheeler

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Introduction

1. Introduction

1.1 The BSE Education Committee has published a minimum dataset for a standard adult transthoracic echocardiogram, available on-line at www.bsecho.org. This document specifically states that the minimum dataset is usually only sufficient when the echocardiographic study is entirely normal. The aim of the Education Committee is to publish a series of appendices to cover specific pathologies to support this minimum dataset.

1.2 The intended benefits of such supplementary recommendations are to:

• Support cardiologists and echocardiographers to develop local protocols and quality control programs for adult transthoracic study;

• Promote quality by defining a set of descriptive terms and measurements, in conjunction with a systematic approach to performing and reporting a study in specific disease-states;

• Facilitate the accurate comparison of serial echocardiograms performed in patients at the same or different sites.

1.3 Understanding restrictive cardiomyopathy (RCM).

This document gives recommendations for the image and analysis dataset required in patients being assessed for restrictive cardiomyopathy (RCM). RCM is a functional classification that is made on the basis of adverse filling of the left ventricle and is therefore different from the structural changes that describe other forms of cardiomyopathy (such as hypertrophic or dilated). RCM can either be primary or more commonly secondary to various conditions (see table) adversely affecting the filling pattern of the left ventricle. The natural histories of conditions causing myocardial restriction exhibit a spectrum of cardiac pathophysiology from subclinical (including the early stages of diastolic dysfunction) through to severely restrictive diastolic filling patterns. Thus the operator should take care to interpret more subtle findings that may be the only manifestations of disease development, with novel deformation imaging assisting in the identification of early disease states.

The morphological and anatomical features of causative pathologies in RCM can be indicative but not specific of an underlying disease state. The majority of RCMs are secondary to systemic aetiologies, the commonest of which is amyloidosis. In contrast, idiopathic (primary) RCM is rare. The term amyloidosis describes a group of disorders caused by abnormal folding, aggregation and accumulation of certain proteins in the tissues, in an abnormal form known as amyloid deposits. This document gives recommendations for the image and analysis dataset required in patients being assessed for RCM with a particular reference to cardiac amyloidosis and the transthoracic echocardiography protocol performed at The UK National Amyloidosis Centre (NAC), with whom this guideline has been co-authored (http://www.ucl.ac.uk/medicine/amyloidosis).

While echocardiography allows a comprehensive assessment in RCM, it is important to remember the complementary role of other imaging modalities, including cardiac MRI.

Primary
Idiopathic
Secondary
Infiltrative disorders
  • Amyloidosis
  • AL: cardiac involvement common.
  • Transthyretin (ATTR): familial variant, usually autosomal dominant.
  • Age-related: senile in 25% aged > 80 years (Wild Type ATTR); atrial in 90% aged > 90 years (deposits derived from atrial natriuretic peptide, NP).
  • AA: cardiac involvement rare.
  • Haemosiderosis (for example: haemochromatosis, transfusion-related iron overload)
  • Sarcoidosis
Endomyocardial fibroelastosis
Scleroderma
Radiotherapy

Adapted from Nihoyannopoulos & Dawson, European Journal of Echocardiography (2009) 10, iii23-iii33

 

1.4 The distinction between concentric remodeling versus concentric hypertrophy (see figure) is an important concept that is poorly understood, but is of prognostic significance in patients with preserved left ventricular ejection fraction.

Still Image 1.4

 

The distinction requires the calculation of relative wall thickness (RWT) and LV mass using the following formulae:

RWT = (2 x LVPWd) ÷ LVIDd

LV mass = 0.8 x {1.04 x [(LVIDd + LVPWd + IVSd)3 - (LVIDd)3]} + 0.6 g

Where LVIDd = left ventricular internal dimension in diastole, LVPWd = left ventricular posterior wall width in diastole, IVSd = interventricular septal width in diastole.

RWT is increased (= 0.42) in both concentric remodeling and hypertrophy, but in infiltrative cardiomyopathy the important distinction is the increased left ventricular mass (>95 g/m2 in females, >115 g/m2 in males). Conversely, the measurement of RWT in cases of increased LV mass allows the distinction between concentric (relative wall thickness = 0.42) and eccentric (< 0.42) hypertrophy.

1.5 The views and measurements are focused upon RCM and are supplementary to those outlined in the minimum dataset. These are given assuming a full study will be performed in all patients.

1.6 When the condition or acoustic windows of the patient prevent the acquisition of one or more components of the supplementary Dataset, or when measurements result in misleading information (e.g. off-axis measurements) this should be stated.

1.7 This document is a guideline for echocardiography in the assessment of RCM and will be up-dated in accordance with changes directed by publications or changes in practice.

Abbreviations

References and Further Reading

 

A '*' indicates that these findings, particularly when found together within an individual echo study, are strongly suggestive of cardiac amyloidosis

  VIEW MODALITY MEASUREMENTS EXPLANATORY NOTE IMAGE

PLAX

2D/M-mode

LV dimensions (LVIDs, LVIDd)

LV cavity size may be normal or small

Click to enlarge

LV wall thickness

 

(IVSd, LVPWd)

May be normal

If > 12 mm concentric thickening in the absence of other pathology (for example, hypertension, HCM or significant aortic stenosis) may suggest infiltrative disease

Note: AL Amyloidosis particularly causes LV increased wall thickness in the mild to moderate range whereas TTR causes LV increased wall thickness in the moderate to severe range (although there is overlap)

LV mass

 

 

 

Relative wall thickness

LV mass = 0.8 x {1.04 x [(LVIDd + LVPWd + IVSd)3 - (LVIDd)3]} + 0.6g
Care should be taken to ensure accurate 2D measurements, as errors are amplified by cubing when calculating LV mass
Relative wall thickness = (2 x LVPWd) ÷ LVIDd
In infiltrative cardiomyopathy there is concentric hypertrophy

Click to enlarge

*Granular or speckled appearance of myocardium

Although this feature is known to be a characteristic feature of cardiac amyloidosis, it is not a specific finding and hence should not be used in isolation

Note: Low dynamic range, low grey scale compression and harmonic imaging can mimic this appearance. Turning off 'harmonic' settings may help to reduce over diagnosis

* Aortic and mitral valve leaflet thickening

Homogenous thickening of leaflets of all valves often seen in amyloidosis

Note: Caution should be taken in this qualitative assessment when using harmonic imaging, which may give rise to the appearance of valve leaflet thickening (see note above

* Pericardial and pleural effusions

Frequently, trace or small pericardial and pleural effusions are seen

PSAX

2D

LV wall thickness at 4 points using clock face as reference (12, 3, 6, 9)

2D frozen image at mid LV level at end diastole to demonstrate concentric increased wall thickness
Note: Avoid inclusion of papillary muscles when measuring LV wall thickness by 2D calliper

Click to enlarge

Apical 4CH

2D

EF (Simpson's Biplane)

Reduced in end stages, but may be normal or mildly reduced in early disease

* IAS thickening

Visual assessment

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*Mitral and tricuspid valve leaflet thickening

Visual assessment: homogenous thickening

Apical 4CH and 2CH

2D

RA adn AL volumes and areas

Measured at end ventricular systols and BSA indexed

 

Biatrial dilatation: RA area > 19cm2, LA volume > 28ml/m2

Click to enlarge

Apical 4CH

M mode

MAPSE

MAPSE <10mm

Reduced longitudinal function may be seen before deterioration in global function assessed by EF

Click to enlarge

Apical 4CH

PW Doppler

MV inflow pattern:

E/A ratio

Severe diastolic dysfunction is more suggestive of an underlying restrictive cardiomyopathy. Earlier in the natural history of restrictive disease, abnormalities of LV filling by PW Doppler of mitral inflow may be in the mild or moderate categories of diastolic dysfunction. Please refer to the BSE diastolic function assessment guidelines

Click to enlarge

E deceleration time

Short deceleration time

Note: normal diastolic filling sis extremely rare in cardiac amyloidosis

Apical 4CH

PW TDI

Mitral annulus:

 

e'

 

e'/a'

 

E/e' Sept and Lat

 

 

 

 

S'

In restrictive filling:

 

Restrictive filling pattern with low e'

 

e'/a' <<1

 

E/e' (average of septal and lateral mitral annulus) > 13

 

Earlier in the natural history of restrictive disease, abnormalities of mitral annular PW TDI may be in the mild or moderate categories of diastolic dysfunction. Please refer to the BSE diastolic function assessment guidelines

 

Reduced systolic velocity

 

Reductions in TDI systolic and diastolic indices typically occur earlier in the natural history of the amyloid disease process than traditional echocardiographic measures, and may be a subclinical marker when this condition is suspected

Click to enlarge

Click to enlarge

Apical 4CH

PW Doppler

PV flow:

PVs/PVd

PVa

adur - Adur

In restrictive filling:

PVs <<PVd

≥ 0.35 m/s

≥ 20 ms

Click to enlarge

Click to enlarge

Apical 5CH

PW or CW Doppler

IVRT

Short IVRT (<50ms) is in keeping with severe restrictive filling, but in earlier stages of the disease process may be prolonged or pseudonormal.  Please refer to the BSE diastolic function assessment guidelines

IVRT is quantified as the time interval between the end of LVOT ejection and the onset of mitral inflow. This can be quantified by PW or CW Doppler to record both mitral inflow and LVOT outflow velocity profiles:

- PW Doppler: position the sample volume within the LVOT, but in close proximity to the anterior mitral valve leaflet

- CW CW Doppler: position the Doppler beam in a hybrid position that captures mitral inflow and LVOT outflow

Click to enlarge

Subcostal

2D M mode

RV free wall thickness

M-mode or 2D frozen image with zoom at end-diastole at the level of the tricuspid valve chordae tendinae
≥ 5 mm RV free wall thickening is abnormal and is frequently seen in cardiac amyloidosis
The administration of intravenous agitated saline may assist in situations where endocardial definition is poor

Click to enlarge

Apical 4CH and 2CH

Deformation imaging

Global and peak longitudinal systolic strain (optional but extremely useful)

Reduced with relative apical sparing, giving rise to a characteristic 'bull's eye' appearance on speckle tracking software*

Ensure high quality, optimized views for speckle tracking post-processing. This should result in a frame rate that is commensurate with optimal speckle tracking (at least > 80 fps)

Reductions in strain indices typically occur earlier in the natural history of the amyloid disease process than traditional echocardiographic measures, and may be a subclinical marker when this condition is suspected

Due to inter-vendor variability, 'cut-off' values are not currently advised, but must be interpreted relative to normative data for individual speckle tracking packages

Click to enlarge

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Copyright © 2011 British Society of Echocardiography