Last updated June 7, 2022

Multimodality Cardiovascular Imaging of Patients with Hypertrophic Cardiomyopathy

Cardiac Amyloidosis versus HCM

  • Echocardiography is the initial imaging modality for evaluation of the presence, magnitude, and pattern of LV hypertrophy and UEA should be used whenever needed.
  • CMR is indicated in patients with suboptimal echocardiographic images, and patients with borderline LV hypertrophy.
  • If CMR is contraindicated or could not be performed, cardiac CT is considered next.
  • Irrespective of which imaging modality is used, the report should comment on the pattern and extent of LV hypertrophy including maximum wall thickness.

Assessment of Left Ventricular Systolic Function

  • Assessment of LVEF should be performed in all HCM patients using echocardiography, with or without UEA, at the time of diagnosis and when there is a significant change in clinical condition. There should be a low threshold for using imaging modalities such as CMR or CT for LV systolic function assessment when echocardiographic images are suboptimal.
  • Assessment of global longitudinal strain adds important prognostic data and may be performed in centers with experience and expertise with using strain echocardiography.

Assessment of Left Ventricular Diastolic Function

  • A comprehensive approach is recommended for the evaluation of diastolic function in HCM.
  • Diastolic function assessment includes mitral inflow velocities recorded at annulus and leaflet tip levels, early diastolic velocity by tissue Doppler measured at septal and lateral sides of the mitral annulus, peak TR velocity obtained by CW Doppler from multiple windows, biplane LA maximum volume index, and pulmonary vein velocities.
  • A restrictive LV filling pattern and increased E/e’ ratio in HCM patients is associated with heart failure hospitalizations, reduced exercise tolerance in children and adults, and SCD.

Pitfalls and Challenges in the Evaluation of Left Ventricular Outflow Tract Obstruction

  • LVOT obstruction occurs in 70-75% of patients, where there is either a resting or provoked LVOT gradient. A systematic approach using provocative maneuvers can differentiate non-obstructive from obstructive phenotype.
  • Most patients with HCM and LVOTO have abnormalities of the mitral valvular and subvalvular apparatus. SAM is a result of drag forces on elongated mitral valve leaflets.
  • SAM/LVOTO is not specific for HCM and can occur in other conditions provoked by reduced afterload, reduced preload, and increased LV contractility.
  • CW Doppler shows a mid-to-late-systolic peaking, dagger-shaped spectral pattern characteristic of dynamic LVOTO. The LVOT gradient can be determined using the modified Bernoulli equation: LVOT gradient = 4 X (LVOT velocity)2
  • Dynamic LVOTO obstruction should be differentiated from fixed subvalvular, valvular, or supravalvular stenosis. The CW Doppler envelope in these latter conditions is usually early peaking.
  • The echocardiographic report, in addition to blood pressure, quantification of LVOT gradient, and mitral valve regurgitation severity, should contain a clear statement about the anatomy of the mitral valve, the presence of SAM, the effect of provocative maneuvers on LVOT gradient, and papillary muscle abnormalities if present.

Provoking Obstruction

  • In symptomatic patients, if a peak instantaneous gradient ≥50 mm Hg is not obtained, then provocative maneuvers should be pursued.

Mitral regurgitation in HCM

  • In most patients with obstructive HCM, mitral regurgitation is related to dynamic obstruction with a posteriorly and laterally directed eccentric jet.
  • In some patients, mitral valve prolapse or flail is the etiology of mitral regurgitation.
  • In some patients, TEE or CMR is needed for better evaluation of the mechanism of MR

Midventricular Obstruction and Apical Aneurysm

  • MVO is diagnosed with mid-cavitary obliteration and a systolic gradient ≥30 mm Hg at rest.
  • Echo with ultrasound enhancing agents or CMR can identify the presence of small apical aneurysms and apical clots. CTA can be used if needed.
  • MVO is associated with higher risk of ventricular arrhythmias and mortality

Tissue Characterization

  • LGE by CMR identifies areas of replacement fibrosis.
  • T1 mapping can be used to determine extracellular volume fraction in HCM patients.
  • LGE patterns and T1 mapping are of value in evaluation of patients with increased LV wall thickness.

Multimodality Imaging for risk stratification and prognostication

  • Imaging provides key data needed for risk stratification for SCD.
  • Maximum wall thickness ≥30 mm, apical aneurysm, LVEF ≤50%, LGE ≥15%, LVOT obstruction, and enlarged LA are imaging findings associated with higher risk of SCD.
  • An UEA is recommended for patients with MVO or apical HCM to evaluate for apical aneurysms.

Multimodality Imaging in Common Clinical Scenarios

  • CCTA can be used to noninvasively evaluate the coronary arteries in HCM patients.
  • PET and CMR are the preferred techniques for stress perfusion imaging.
  • Epicardial CAD in HCM patients is associated with worse outcomes.
  • Echocardiography is the initial imaging modality for HCM screening.
  • Periodic screening is recommended at intervals that depend on age, presence of a known pathogenic variant, and whether disease is early onset.
  • CMR should be considered in patients with technically challenging echocardiograms, and in patients in whom abnormal electrocardiographic findings are present despite an apparently normal echocardiogram.
  • For patients on oral allosteric modulators of cardiac β-myosin, monitoring of LVEF is essential to avoid the development of heart failure due to reduced EF.
  • Intraoperative TEE plays a critical role in guiding the management of HCM patients undergoing surgical myectomy.
  • Myocardial contrast echocardiography plays a critical role in intraprocedural guidance of alcohol septal ablation.
  • TEE is critical for intraprocedural guidance of TEER to treat obstructive HCM patients who are not candidates for septal reduction therapy.

Tables

Table 1. Typical Features and Findings in Phenocopies of HCM

Most Common Phenocopies Clinical Features Typical ECG Findings Typical Echo Findings Typical CMR Findings Genetics and Additional Features
Children/Adolescents
 Danon Disease Mild skeletal myopathy, ophthalmic abnormalities, intellectual disability. May reveal pre-excitation syndrome. Massive concentric LVH, occasionally dilated cardiomyopathy. LVH is often severe. LGE can be extensive, but often conspicuously sparing of the mid septum X-linked dominant disorder, although isolated cardiac form can present in older females. Diagnosis based on elevated CK, muscle biopsy, genetic testing (LAMP2 gene mutation)
Adults <40 years
 PRKAG2 Proximal myopathy, myalgia, epilepsy, early-onset hypertension Pre-excitation syndrome, bundle branch block, high voltages. Atrial fibrillation, atrial flutter. Advanced atrioventricular blocks, marked sinus bradycardia, or sinus block Variable degree of increased LV wall thickness. Diastolic and systolic dysfunction Highly variable findings from minimal asymmetric hypertrophy without LGE in early stages to severe hypertrophy with extensive LGE in advanced stages Autosomal dominant, PRKAG2 gene mutation
 Friedrichs Ataxia Progressive ataxia, loss of deep tendon reflexes, motor weakness, cerebral dysarthria, diabetes mellitus Lateral T wave flattening or inversion. Supraventricular and ventricular arrhythmia Mild concentric remodeling, followed by hypertrophy, less often eccentric, hypertrophy. Impaired relaxation. Ultimately dilatation with systolic dysfunction. Sparkling texture. In early and intermediate disease: concentric remodeling or hypertrophy. In late disease: replacement fibrosis. Autosomal recessive, serum alpha-tocopherol level, brain MRI
 Anderson- Fabry Disease Multi-system disease: peripheral neuropathy, cutaneous lesions, progressive renal insufficiency with proteinuria, coronary small vessel disease. LVH with repolarization abnormalities, conduction abnormalities, preexcitation, atrial and ventricular arrhythmia. Concentric, asymmetric, and eccentric hypertrophy. Impaired relaxation. Normal ejection fraction. Thinned basal inferolateral LV wall in advanced disease. RV hypertrophy. Prominent papillary muscle. Aortic dilatation. LGE typically involves the mid segments of the lateral wall with subendocardial sparing. Involvement of the basal third of other LV walls in severe cases. Short T1 relaxation time may be present in the septum. X-linked recessive, deficiency of alpha-galactosidase A activity. Males present at a younger age.
 Athlete’s Heart Asymptomatic Sinus bradycardia, LVH, early repolarization, first degree heart bock, Wenckebach, ectopic atrial or junctional rhythm. End-diastolic wall thickness typically below 15 mm. Balanced four chambers dilation. Normal/low-normal biventricular ejection fraction with normal/supranormal diastolic function. LGE absent except occasionally at the RV insertion points. Normal ECV. Supranormal functional capacity.
Adults > 40
 Hypertensive Heart Disease May be asymptomatic or develop heart failure symptoms related to diastolic dysfunction LVH (low sensitivity for detecting anatomic LVH), repolarization abnormalities, prolonged QTc and QRS duration Most commonly concentric hypertrophy or remodeling with varying degrees of diastolic dysfunction depending on the severity and duration of hypertension Patchy LGE can be seen. Increased extracellular volume fraction in some patients
 Cardiac Amyloidosis Clinical features include heart failure, peripheral neuropathy, atrial arrhythmias, and carpal tunnel syndrome Low QRS voltages relative to LV wall thickness. Conduction abnormalities, supraventricular arrhythmias. Concentric increase in LV wall thickness, sometimes with septal predominance. Restrictive LV filling pattern with more advanced disease. Normal to progressively reduced systolic function. Reduced global longitudinal strain with apical sparing. Bi-atrial dilatation. Thickening of valve leaflets. Small pericardial effusion. Subendocardial and transmural late gadolinium enhancement with relative apical sparing. Characteristic simultaneous myocardial and blood nulling or suboptimal myocardial nulling. Prolonged native myocardial T1 relaxation time. Increased extra-cellular volume fraction. Technetium-based bone scintigraphy for ATTR amyloidosis. Monoclonal proteins assay in blood and urine in patients with AL amyloidosis. Tissue biopsy may be needed.

Table 2. Differential Diagnosis of SAM and LVOTO

  • Elderly with hypertension, sigmoid septum and hyperdynamic LV function
  • Compensatory basal septal hypercontractility following acute myocardial infarction with apical dysfunction
  • Takotsubo cardiomyopathy with hyperdynamic basal LV function
  • Massive posterior mitral annulus calcification
  • After surgical and percutaneous mitral valve repair
  • After aortic valve replacement in patients with LVH and hyperdynamic LV
  • Elderly patients in ICU with anemia, volume depletion, tachyarrhythmias, sepsis
  • Medications eg: inotropes, vasodilators and sympathomimetics
  • Right ventricular pressure overload like acute COPD exacerbation and/or ARDS
  • Phenocopies of HCM such as cardiac amyloidosis or Anderson-Fabry disease

Table 3. Summary of Key Imaging Markers and Approach in SCD Risk Stratification

Imaging Parameter SCD risk threshold Imaging Approach Practical Points and/or Caveats
Established markers
 LV maximal wall thickness Highest risk in those with LVH ≥ 30 mm, although relationship between wall thickness and SCD is continuous Echo or CMR Limited negative predictive value of 30 mm threshold, most SCD occurs below this threshold
 Late gadolinium enhancement∗∗ Highest risk in those with LGE > 15%, although relationship between LGE and SCD is continuous CMR Abnormal threshold of >6SD above normal myocardium
 LVOT obstruction >30 mm Hg Echo Varies according to loading conditions and activities
 LV apical aneurysm Presence associated with increased risk even in those > 60 years old Echo or CMR CMR more sensitive, suspect in those with mid cavity obliteration
 Left atrial size LA volume (> 34 ml/m2) using biplane LA volumes or anteroposterior diameter (>48 mm) Echo Single 2-D measurement may erroneously estimate size
 LV ejection fraction LV ejection fraction <50% Echo or CMR Consider use of contrast echo or CMR to optimally assess LVEF
Emerging marker
 LV global longitudinal strain No clear threshold value, abnormal results portend a worse prognosis Echo (CMR approaches emerging) Further standardization needed between platforms
∗ Major risk factor for SCD and if present, is considered class IIA indication for ICD implantation.
∗∗ In HCM patients without major risk factors for SCD and uncertain on whether to implant ICD, decision on ICD implantation may be reached based on late gadolinium enhancement findings.

Recommendation Grading

Overview

Title

Multimodality Cardiovascular Imaging of Patients with Hypertrophic Cardiomyopathy

Authoring Organization

Endorsing Organizations

Publication Month/Year

June 1, 2022

Document Type

Guideline

Country of Publication

US

Document Objectives

Hypertrophic cardiomyopathy (HCM) is defined by the presence of left ventricular hypertrophy in the absence of other potentially causative cardiac, systemic, syndromic, or metabolic diseases. Symptoms can be related to a range of pathophysiologic mechanisms including left ventricular outflow tract obstruction with or without significant mitral regurgitation, diastolic dysfunction with heart failure with preserved and heart failure with reduced ejection fraction, autonomic dysfunction, ischemia, and arrhythmias. Appropriate understanding and utilization of multimodality imaging is fundamental to accurate diagnosis as well as longitudinal care of patients with HCM. Resting and stress imaging provide comprehensive and complementary information to help clarify mechanism(s) responsible for symptoms such that appropriate and timely treatment strategies may be implemented. Advanced imaging is relied upon to guide certain treatment options including septal reduction therapy and mitral valve repair. Using both clinical and imaging parameters, enhanced algorithms for sudden cardiac death risk stratification facilitate selection of HCM patients most likely to benefit from implantable cardioverter-defibrillators.

Inclusion Criteria

Male, Female, Adolescent, Adult, Child, Infant, Older adult

Health Care Settings

Hospital, Outpatient, Radiology services

Intended Users

Nurse, nurse practitioner, physician, physician assistant

Scope

Diagnosis, Assessment and screening

Diseases/Conditions (MeSH)

D002312 - Cardiomyopathy, Hypertrophic, D057791 - Cardiac Imaging Techniques

Keywords

hypertrophic cardiomyopathy, cardiovascular imaging

Source Citation

DOI: https://doi.org/10.1016/j.echo.2022.03.012