3 Role of Each Diagnostic Modalities for HCM

14



Hypertrophic Cardiomyopathy



Fig. 14.1 Dynamic LVOT obstruction.

Asymmetric septal HCM with systolic anterior

motion (SAM) in a 74-year-old man who presented

with chest tightness. (a) Schematic illustration of

LVOT obstruction. (b) Four-chamber SSFP cine

MR images show systolic anterior motion (SAM)

of the anterior mitral valve leaflet (arrows)

accompanied by a signal void jet flow into the

LVOT. There is also a jet of mitral regurgitation

(arrowheads) into a moderately enlarged left

atrium



183



a

LA

Aorta

MR



SAM



LVOT

gradient



ASH



b



LV



184

Table 14.1 Relative merits of

each noninvasive imaging for the

assessment of hypertrophic

cardiomyopathy



E.J. Chun and S.I. Choi



LV volume

LV hypertrophy

Ejection fraction

Regional function

LV filling pressure

PA pressure

Dynamic obstruction

Mitral regurgitation

Ischemia/CFR

Monitoring of therapy

Tissue characterization

Preclinical diagnosis



Echocardiography

+++

+++

+++

+++

+++

+++

+++

+++

+

+++

++

++



MDCT

++

++++

+++

++

–

–

+

–

–

+

+

+++



MRI

++++

++++

++++

++++

++

+++

+++

++

++

+++

++++

+++



This table is referred by radiographics (ref; Chun et al. [5])

LV left ventricular, PA pulmonary artery, CFR coronary flow reserve



• Echocardiography has a limitation of operator and sonic

window dependency; it is sometimes unable to define the

endocardial border, especially the anterolateral free wall

of the left ventricle (LV) in the parasternal short-axis view

and apex.

• The degree of LVH could be underestimated by echocardiography, which, in fact, can delay proper treatment,

thereby failing to prevent a SCD.



14.3.1.2 MRI

• CMR has strength of 3D imaging technique with high

spatial and temporal resolution useful for detection of

focal LVH which may not be well visualized by 2D

echocardiography.

• SSFP cine MRI sequence produces sharp contrast between

the bright blood pool and the dark myocardium, including

accurate wall thickness and mass measurements with high

reproducibility.

• CMR is indicated in patients with suspected HCM when

echocardiography is inconclusive for diagnosis (Class I,

Level of Evidence B).

• CMR is reasonable in patients with HCM to define apical

HCM and/or aneurysm if echocardiography is inconclusive (Class IIa, Level of Evidence B).

14.3.1.3 MDCT

• MDCT has higher spatial resolution over MRI and echocardiography; it is at least equivalent or more likely superior with respect to HCM phenotype (LV thickness,

volume, EF, mass, etc.).

• MDCT provides complete tomographic coverage of the

entire myocardium because of isotropic imaging; it can

well assess all cardiac structures including papillary

muscles.

• MDCT may be reasonable in the patient who has contraindicated CMR (i.e., pacemaker or IDC implantation,

claustrophobia, etc.) or when patients cannot hold their

breath for long periods.



14.3.2 Assessment of LV Systolic

and Diastolic Function

14.3.2.1 Echocardiography

• Echocardiography is a validated method for a comprehensive approach of systolic and diastolic function including

LA and LV filling pressure.

• TTE is useful for myocardial function (Class IIa, Level of

Evidence C).

14.3.2.2 MRI

• CMR measurements of systolic function including ventricular volumes and EF are validated with high diagnostic accuracy and high reproducibility.

• CMR can measure mitral inflow, the pulmonary vein, and

LV filling.

14.3.2.3 MDCT

• CT provides an accurate assessment of systolic function

including LV volume and EF.

• CT is not indicated for the assessment of LV diastolic

function due to limited temporal resolution than MRI or

echocardiography.



14.3.3 Dynamic LVOT Obstruction and Mitral

Valve Abnormalities

14.3.3.1 Echocardiography

• Echocardiography is an initial modality for LVOT

obstruction or mitral regurgitation.

• Exercise TTE can be useful in the detection and quantification of dynamic LVOT obstruction (Class IIa, Level of

Evidence B).

14.3.3.2 MRI

• Cine MRI can accurately identify the presence of mitralseptal contact and regurgitant signal void jet.



14



Hypertrophic Cardiomyopathy



• Velocity encoding (VENC) sequence can measure the

peak velocity through the LVOT.

• However, it has limited that CMR-derived velocities can

be assessed only under basal conditions, because one

third of patients with HCM have LVOT obstruction only

during provocation.



14.3.3.3 MDCT

• CT is not indicated for dynamic obstruction of mitral

regurgitation although it can well evaluate the papillary

muscle or mitral valve apparatus.



14.3.4



Myocardial Ischemia



14.3.4.1 Echocardiography

• In general, there is a limited role for echocardiography in

diagnosing myocardial ischemia, although regional wall

motion abnormality is an indirect finding for ischemia.

14.3.4.2 MRI

• Stress perfusion MRI permits accurate qualitative and

quantitative assessment of myocardial blood flow at rest

and during pharmacologic stress, with superior spatial

resolution to PET.

• The severity of perfusion impairment in HCM is correlated with the degree of LVH.

14.3.4.3 MDCT

• In patients with HCM with coexistent epicardial coronary

disease, because epicardial coronary disease is one of the

several etiologic mechanisms that contribute to myocardial

ischemia in patients with HCM, it can be difficult to interpret whether ischemia is caused by HCM or by decreased

coronary flow reserve.

• Cardiac MDCT can provide useful information for the

noninvasive assessment of coexistent epicardial coronary

disease in patients with HCM [5].



14.3.5



Myocardial Fibrosis



14.3.5.1 Echocardiography

• Large areas of regional fibrosis can lead to segmental dysfunction manifested by reduced strain. However, it is limited for its low specificity for fibrosis.

14.3.5.2 MRI

• Late delayed gadolinium-enhancement (LGE) MRI techniques can provide unique information on tissue characterization, specifically for the identification of myocardial

fibrosis or scarring.

• Areas of LGE can be measured and the amount quantified

and expressed as a percentage of total LV mass.



185



• The prevalence of LGE in HCM is approximately

50–70 % and when present occupies on average 10 % of

the overall LV myocardial volume.

• The location of LGE is common at the confined area to

only the LV free wall or insertion points of the RV free

wall and ventricular septum. In addition, LGE tends to

locate in segments with hypertrophy or with large LV

mass.

• However, it still remains uncertain whether all LGE in

patients with HCM with normal or hyperdynamic EF represents myocardial fibrosis.

• CMR may be considered for risk stratification with late

gadolinium enhancement (LGE) and differential diagnosis

from other infiltrative disease including cardiac amyloidosis or Fabry disease (Class IIb, Level of Evidence C).



14.3.5.3 MDCT

• CT has no role at the present time for the evaluation of

myocardial fibrosis.



14.4



Classification of HCM by Phenotypes



• The usual diagnostic criterion for HCM is a maximal LV

wall thickness greater than or equal to 15 mm on enddiastolic phase.

• Although the morphologic expression of HCM is widely

variable and heterogeneous because HCM may affect any

portion of the LV, the classification according to distribution of LV hypertrophy is usual as follows (Fig. 14.2) [5, 6].



14.4.1 Asymmetric (Septal) HCM

• The most common form of the HCM with prevalence rate

of 60–70 %.

• Diagnosed when septal thickness is greater than or equal

to 15 mm or the ratio of septal to inferior wall of LV is

greater than 1.5 at mid-ventricular level (Fig. 14.3).

• The most common location of LVH is the anterior free

wall and contiguous basal anterior ventricular septum.

• The presence of LVOT obstruction, which is fixed or

dynamic, and the presence of associated mitral regurgitation should be checked for preventive implantation of ICD.



14.4.2



Apical HCM



• It typically shows hypertrophy of the myocardium predominantly involves the apex of the LV with diagnostic

criteria as absolute apical wall thickness of >15 mm or a

ratio of apical to basal left ventricular wall thicknesses of

1.3–1.5.



186



E.J. Chun and S.I. Choi



a



b



c



d



e



f



Fig. 14.2 Various phenotypes of HCM. The diagnostic criterion of

HCM is that maximal LV wall thickness is greater than or equal to 15 mm

on end-diastolic phase. (a) Normal, (b) asymmetric septal HCM with



LVOT obstruction, (c) asymmetric septal HCM without LVOT obstruction, (d) apical HCM, (e) symmetric HCM (concentric HCM), (f) midventricular HCM, (g) mass-like HCM, and (h) noncontiguous HCM