Hypertrophic Cardiomyopathy

Multimodality Imaging in HCM

HCM is defined by LV hypertrophy (≥15 mm) in the absence of other causative conditions. Prevalence: 1:200–1:500. Symptoms arise from LVOT obstruction, diastolic dysfunction, ischemia, and arrhythmias. Multimodality imaging is fundamental to diagnosis, risk stratification, and guiding treatment.

📋Diagnostic Criteria

Wall thickness ≥15 mm in any LV segment (no other cause) — diagnostic in adults

Wall thickness ≥13 mm — diagnostic if family history of HCM or known pathogenic mutation

Pediatrics: z-score >2 (size-specific; somatic growth must be considered)

Hypertrophy usually asymmetric, affecting non-contiguous LV segments; occasionally involves RV

≥13 mm + family Hx ≥15 mm diagnostic ≥30 mm massive LVH

🩻Imaging Modality Roles

TTE

First-line modality for diagnosis, LVH characterization, LVOT gradient, MV anatomy, diastolic function, and serial follow-up

CMR

LGE for fibrosis, tissue characterization (T1/T2 mapping/ECV), subaortic membrane and papillary muscle morphology, borderline LVH, suboptimal echo, MR perfusion stress for subendocardial ischemia indicative of microvascular dysfunction

CMR-incompatible devices, septal perforator mapping pre-ASA, CCTA for coronary anatomy (including myocardial bridging), 3D morphology

Nuclear

Myocardial perfusion (SPECT/PET), microvascular dysfunction; PET preferred for quantitative myocardial blood flow; Tc-based bone scintigraphy (Tc-PYP) for ATTR amyloidosis

🗺️HCM Phenotypic Patterns — Select to Explore

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Sigmoid

Basal anterior septum

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Reversed Curvature

Mid-septum; highest genetic yield

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Apical

Distal LV; deep T-wave inversions

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Mid-Cavity

MVO; aneurysm risk

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Concentric

Neutral; phenocopy overlap

ℹ️

Sigmoid Septum: Basal anterior septal bulge with ovoid LV cavity. Septal/posterior wall ratio >1.3 in a normotensive patient. Lowest genetic yield of all patterns — common in elderly hypertensive patients. Ensure RV trabeculations are not included in measurement (compare PLAX and PSAX).

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Reversed Septal Curvature: Crescent-shaped LV cavity with mid-septal hypertrophy. Highest yield for pathogenic sarcomere mutations. Patients with mutations have greater wall thickness than mutation-negative individuals, correlating with higher adverse event rates.

⚠️

Apical HCM: Hypertrophy confined to the distal LV. Associated with deep lateral T-wave inversions on ECG. Avoid LV foreshortening. Use UEA (ultrasound enhancing agent) to evaluate apex — low threshold given risk of missing apical aneurysm. CMR if still uncertain. Less LVOTO, higher prevalence in athletes with HCM.

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Mid-Cavity Obstruction (MVO): Systolic obliteration of LV cavity + gradient ≥30 mmHg at rest. High-risk phenotype — associated with refractory symptoms, ventricular arrhythmias, premature mortality. LV thrombus risk. MVO can be complicated by an apical aneurysm (~3% of CMR registry patients) — it is the apical aneurysm that is an established SCD risk marker and Class IIa consideration for prophylactic ICD, not MVO per se. Always use UEA or CMR to evaluate for apical aneurysm in any patient with MVO or apical HCM.

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Concentric/Neutral Pattern: Symmetric LVH. Key differential: hypertensive heart disease, cardiac amyloidosis, Fabry disease, PRKAG2. Integrate ECG, clinical history, and tissue characterization by CMR (LGE, T1 mapping, ECV) to differentiate HCM from phenocopies.

📊Class I Recommendations at a Glance

Initial Evaluation

TTE recommended for all suspected HCM

UEA when visualization is suboptimal

CMR for borderline LVH or suboptimal echo

Report: pattern, extent, max wall thickness at end-diastole

Established HCM Follow-up

Repeat TTE every 1–2 years if no clinical change

Prompt repeat TTE with any change in status

TTE at 3–6 months post septal reduction therapy

CMR every 3–5 years for SCD risk (Class IIb)

Assessment of LV Hypertrophy & Phenocopy Differentiation

Accurate quantification of the magnitude, location, and pattern of LVH is essential. The imaging report must include the pattern and distribution of hypertrophy, the location of maximum wall thickness, and the measurement at end-diastole.

📐Echocardiographic Pitfalls in Wall Thickness Measurement

RV trabeculations & structures ▼

Systematic exclusion of RV structures (trabeculations, moderator band, crista supraventricularis) is mandatory when measuring the IVS. Compare PLAX and PSAX views to differentiate true contractile IVS from RV trabeculation — the blue line measurement in the figure example inflated IVS from 10 mm to 13 mm.

Long-axis view overestimation ▼

Long-axis views can overestimate wall thickness due to tangential cuts through the wall. This applies to both echo and CMR. Always integrate and cross-reference short- and long-axis views for accurate measurements. CMR example: tangential long-axis cut produced 23 mm vs. true 18 mm on short-axis.

Apical and anterolateral walls ▼

Apical, anterior, and anterolateral walls are challenging to visualize and measure accurately. Use a low threshold for UEA — especially when pre-test probability is high (family member of gene-positive patient, concerning ECG patterns like deep lateral T-wave inversions). UEA measurements are more reproducible and better aligned with CMR.

3D echocardiography ▼

High-quality 3D echo is superior to 2D for LV mass and more closely correlates with CMR. RV free wall should be measured in subcostal views at end-diastole, avoiding epicardial fat inclusion.

🔬Differentiating HCM from Phenocopies — Key Features

Phenocopy	Population	Key ECG Finding	Key Echo/CMR Finding	Distinguishing Feature
Athlete's Heart	Young, trained	Sinus brady, early repolarization, LVH voltages	WT typically <12 mm (Caucasian), <15 mm (Black male); balanced 4-chamber dilation; supranormal diastolic function; no LGE	Normal/supranormal diastolic function; no SAM; regression with detraining (may occur in HCM too)
Cardiac Amyloidosis	Adults >40	Low QRS voltage relative to WT; pseudo-infarct pattern	Concentric LVH, restrictive filling, GLS apical sparing; diffuse subendocardial or transmural LGE; prolonged T1, elevated ECV	GLS apical sparing reclassifies 22% of cases; Tc pyrophosphate scan for ATTR
Hypertensive Heart Disease	Adults >40	LVH criteria, repolarization changes, prolonged QTc	Concentric hypertrophy or remodeling; varying diastolic dysfunction; patchy LGE possible	History of hypertension; no SAM; no mutation; increased ECV in some
Anderson-Fabry Disease	Adults	LVH + repolarization; preexcitation; arrhythmias	Concentric/asymmetric LVH; prominent papillary muscle; thinned basal inferolateral wall in advanced disease; LGE lateral mid-wall; short T1 in septum	Multi-system involvement; deficient α-galactosidase A; X-linked
Danon Disease	Children/adolescents	Pre-excitation (WPW); high voltages	Massive concentric LVH; extensive LGE sparing mid-septum	Elevated CK; LAMP2 mutation; X-linked dominant
PRKAG2	Adults <40	Pre-excitation; BBB; AF; AV block; sinus bradycardia	Variable LVH; from minimal to severe; variable LGE	Autosomal dominant; PRKAG2 gene mutation

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ECG Integration: Deeply inverted T-waves in lateral leads → suspect apical HCM. Low voltage QRS relative to wall thickness → suspect amyloidosis. Short PR or pre-excitation → consider Fabry, Danon, PRKAG2. Use Figure 4 algorithm integrating ECG + echo findings.

💪Athlete's Heart vs. HCM — Gray Zone Approach

Favors Physiologic Hypertrophy

WT <12 mm (Caucasian); <15 mm (elite Black male athletes)

Balanced 4-chamber dilation; uniform thickening (<2 mm difference)

Normal or supranormal diastolic function

No SAM; no LVOTO at rest or exercise

Preserved/supranormal functional capacity

No LGE by CMR (except occasional RV insertion points)

Favors HCM

Asymmetric or non-contiguous hypertrophy

Abnormal mitral valve/subvalvular anatomy; SAM

Pathologic ECG: inferolateral TWI, ST depression, Q waves

LGE on CMR; abnormally prolonged T1; increased ECV

Family history of HCM or SCD; known pathogenic mutation

Exercise-induced LVOTO in pediatric patients

⚠️

Note: Normal diastolic function and preserved functional capacity can occur in athletes with HCM. Regression of hypertrophy with detraining, while suggestive of physiologic adaptation, may also occur in HCM. Pursue CMR if concern persists after initial evaluation.

LVOT Obstruction & Mitral Valve Assessment

LVOTO occurs in 70–75% of HCM patients at rest or with provocation. SAM is driven primarily by drag forces on elongated mitral leaflets, not Venturi forces. A systematic Doppler approach with provocative maneuvers is essential.

📏LVOT Gradient Calculator

Peak LVOT Velocity (m/s)

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mmHg

Modified Bernoulli: Gradient = 4 × V²

<30: Not significant 30–49: Significant ≥50: CMI or invasive therapy threshold

🔄LVOT Gradient from MR Velocity

Peak MR Velocity (m/s)

Systolic BP (mmHg)

Assumed LAP (mmHg, typically 10–15)

Enter MR velocity and SBP to calculate estimated LVOT gradient.

⚠️

Caution: if velocity >5.5 m/s, verify this is LVOT signal and not MR. MR velocity is always higher than LVOT, peaks earlier, and has longer duration (spans isovolumic contraction & relaxation).

🔊Doppler Findings — Key Patterns

CW Doppler Patterns in LVOTO

Dagger-shaped: Mid-to-late systolic peaking; concave-to-the-left contour — classic LVOTO pattern

Lobster-claw: Seen when gradient >60 mmHg at rest; two low-velocity systolic components with mid-systolic drop

Early-peaking, triangular (low velocity): Reflects normal LVOT flow — not obstructive

High-velocity, parabolic/delayed acceleration time: Favors fixed obstruction (DSS, aortic stenosis) — contrast with the mid-to-late peaking dagger shape of dynamic LVOTO

Mid-cavity pattern: Intracavitary velocity peaking in mid-systole with abrupt deceleration — MVO

M-Mode & Color Doppler

M-mode SAM severity: Mild: SAM-septal distance >10 mm; Moderate: ≤10 mm or brief contact (<30% systole); Severe: contact ≥30% of systole

Mid-systolic aortic notch: M-mode sign of LVOT obstruction — premature aortic valve closure

Color Doppler: Localizes turbulent aliased flow; turbulence onset = anatomical level of obstruction

PW Doppler: Sequential sampling from LV apex to LVOT to localize obstruction level

🫀Mitral Valve Anatomy in Obstructive HCM

Structural Abnormalities

Elongated anterior mitral leaflet — extends past coaptation point, generating drag-force SAM

Anterior/apical papillary muscle displacement — 70% have bifid papillary muscle on CMR

Anomalous insertion of papillary muscle directly into anterior leaflet (~13%)

Leaflet >16 mm/m² considered elongated; may require plication at surgery

MR in Obstructive HCM

SAM-related MR: typically posteriorly or laterally directed eccentric jet; mid-to-late systolic

Central or anterior jet → evaluate for intrinsic valve pathology (prolapse, flail, chordal rupture)

Quantify MR as: LV SV (2D) minus RVOT stroke volume (in absence of significant AR)

PISA method unreliable for eccentric jets — use volumetric approach

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Echocardiographic report must include: (1) quantification of LVOT gradient and MR severity, (2) mitral valve anatomy, (3) degree and duration of SAM, (4) papillary muscle morphology, (5) effect of provocative maneuvers on gradient.

⚡Provocative Maneuvers Algorithm

Resting TTE

Measure peak LVOT gradient at rest. Gradient ≥30 mmHg is significant; ≥50 mmHg is the threshold for CMI or invasive therapy consideration.

If Resting Gradient <50 mmHg → Provocation

Valsalva (strain phase): Goal-directed approach — maintain >40 mmHg for >10 sec. Less effective than exercise. Squat-to-stand: 5 cycles of squat (3 sec) then stand. Amyl nitrite: Vasodilator; limited supply in many centers.

If Bedside Provocation Fails → Exercise Stress Echo

Most physiologic provocation. Upright (treadmill/upright bike) preferred — higher gradients than supine. Measure gradient immediately post-exercise in supine position. Dobutamine stress echo is NOT recommended — non-physiologic; can provoke gradients in normal subjects. Post-prandial state may also reveal latent obstruction and can be assessed when resting and provoked gradients are otherwise borderline.

Gradient ≥50 mmHg + Drug-Refractory Symptoms

Threshold for consideration of cardiac myosin inhibitor (CMI) therapy or invasive septal reduction therapy (SRT). Beta blockers and non-DHP calcium channel blockers should not be withheld prior to exercise testing. Pediatric patients: exercise echo preferred (≥8 years, cooperative).

⚙️Differential Diagnosis of SAM/LVOTO

⚠️

SAM is not specific for HCM. Other causes include: elderly with sigmoid septum + hyperdynamic LV; compensatory basal hypercontractility post-MI; Takotsubo cardiomyopathy; post-mitral valve repair; post-AVR with LVH; ICU patients with anemia/volume depletion/tachycardia; inotropes/vasodilators; RV pressure overload (COPD/ARDS exacerbation); cardiac amyloidosis; Anderson-Fabry disease.

Diastolic Function Assessment in HCM

Diastolic dysfunction in HCM is driven by impaired LV relaxation, increased myocyte/chamber stiffness, and abnormal LA function from an atrial myopathy. It contributes to symptoms even in non-obstructive HCM. A comprehensive approach is required.

🩺Required Parameters for HCM Diastolic Assessment

Essential Measurements

Mitral inflow: Record at leaflet tips (E, A velocities) AND at annulus level (for Ar duration)

Tissue Doppler: Septal e' and lateral e' at mitral annulus → calculate average E/e' ratio

TR velocity: CW Doppler from multiple windows; correlates with mean LAP

Biplane LA maximum volume index: More accurate than anteroposterior diameter

Pulmonary vein velocities: Especially Ar-A duration — Ar-A >30 ms → elevated LVEDP

LA Pressure Estimation Thresholds

LA max volume index >34 mL/m² Average E/e' ratio >14 Peak TR velocity >2.8 m/s

3/3 or 2/2 abnormal → LA pressure elevated
3/3 or 2/2 normal → LA pressure normal
Only 1 feasible or conflicting → Indeterminate

ℹ️

In the presence of ≥moderate MR, E/e' and LA volume are unreliable. Use peak TR velocity and Ar-A duration preferentially.

📈LA Strain & Advanced Diastolic Parameters

LA reservoir, conduit, and pump strain associated with reduced exercise tolerance and new-onset AF in HCM

Serial LA strain analysis by the same software for a given patient is reasonable (inter-vendor differences exist)

CMR: High burden of atrial fibrosis in HCM patients — accounts for abnormal LA function and predisposition to AF

Shear wave imaging: Propagation speed higher in HCM vs. controls — reflects increased myocardial stiffness; currently investigational

Restrictive filling pattern + elevated E/e' in HCM associated with: HF hospitalizations, reduced exercise tolerance in children & adults, and SCD

Pediatrics: Adult guidelines should NOT be applied. Normal ranges are very wide; use age-specific values

📉LV Systolic Function Assessment

EF Assessment

LVEF is normal to hyperdynamic in most HCM patients

LV dysfunction (EF <50%) in 4–9% of cohorts; associated with high all-cause mortality and transplant/LVAD rates

Endorsed lower limit of normal: 50% (2D or 3D echo) given absence of HCM-specific data

Use UEA when images suboptimal; CMR or CT if still inadequate

Global Longitudinal Strain (GLS)

Strain abnormalities co-locate with regions of hypertrophy (septum in classic HCM; apex in apical variant)

GLS predicts event-free survival in HCM patients with normal EF

Systolic strain rate augmentation is blunted with exercise — in both obstructive and non-obstructive HCM

FT-CMR strain inversely related to LGE burden (%); no additional acquisition needed for post-processing

SCD Risk Stratification & Imaging Markers

Overall SCD risk in HCM is approximately 0.5%/year. Imaging provides key risk markers. The ESC HCM Risk-SCD calculator incorporates age, max wall thickness, LA diameter, max LVOT gradient, family history, NSVT, and unexplained syncope.

🎯SCD Risk Assessment Tool

Check all applicable risk factors for this patient:

Major Risk Factors (Class IIa for ICD)

Massive LVH ≥30 mm

(~10% of HCM; continuous relationship between WT and risk)

LV Apical Aneurysm

Independent of size; adverse event rate 5–15%/year; Class IIa ICD

LVEF <50%

Class IIa for ICD; consider CMR for accurate EF assessment

Additional Imaging Risk Markers

Extensive LGE ≥15% of LV mass

6SD or FWHM technique; LGE present in ~50% of HCM but SCD prevalence far lower

LVOT Obstruction ≥30 mmHg

Resting gradient; stronger association than latent gradient for SCD

Enlarged LA (diameter ≥48 mm or volume index >34 mL/m²)

Included in ESC HCM Risk-SCD calculator as continuous variable

Select risk factors above to see guidance.

🔬LGE by CMR — Imaging Details

Present in ~50% of HCM patients; typically patchy, mid-myocardial, within segments of maximal hypertrophy

LGE ≥15% of LV mass (6SD technique) associated with increased SCD risk; use for "gray zone" patients without major ACC/AHA risk factors

Quantification: either 6 SD or FWHM technique preferred in HCM; both superior to 2SD

Isolated LGE at RV insertion points — not associated with increased risk

Repeat CMR every 3–5 years — evaluate changes in WT, LGE magnitude, new apical aneurysms, LVEF changes

LGE Patterns in HCM

RV insertion points: Not independently associated with increased risk (most common pattern)

Patchy mid-ventricular (hypertrophied septum): Non-ischemic pattern; most prognostically significant

Apical transmural LGE: Associated with apical aneurysm; high thromboembolic risk; Class IIa ICD

T2 signal: Increased signal = edema/inflammation; potentially increased SCD risk (limited data)

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T1 Mapping & ECV: Native T1 correlates with areas of increased wall thickness and LGE in HCM. ECV quantifies diffuse interstitial expansion. Helps differentiate HCM from HHD, athlete's heart, Fabry disease, and cardiac amyloidosis. Associated with adverse outcomes.

📋Summary: Key Imaging Markers for SCD Risk

Imaging Parameter	SCD Risk Threshold	Modality	Key Caveat
LV Max Wall Thickness*	Highest risk ≥30 mm; relationship is continuous	Echo or CMR	Most SCD occurs below 30 mm threshold; limited negative predictive value
Late Gadolinium Enhancement**	Highest risk >15%; continuous relationship	CMR	Threshold >6 SD above normal myocardium; no single recommended technique
LVOT Obstruction*	Resting gradient ≥30 mmHg	Echo	Varies with loading conditions; dynamic nature limits use as sole marker
LV Apical Aneurysm*	Any size associated with risk	Echo (UEA) or CMR	CMR more sensitive; suspect in mid-cavity obliteration; Class IIa ICD
LA Size	Volume >34 mL/m² or diameter ≥48 mm	Echo	Included in ESC calculator; volume more accurate than single 2D measurement
LVEF*	EF <50%	Echo or CMR	Class IIa ICD; consider CMR for optimal EF assessment
LV GLS (emerging)	No clear threshold; abnormal = worse prognosis	Echo (CMR emerging)	Further standardization needed between platforms

*Major risk factor — Class IIa indication for ICD if present. **Used in "gray zone" patients without major risk factors for shared decision-making.

Imaging for Treatment Selection & Monitoring

Imaging guides every phase of HCM management — from selection of septal reduction therapy to intraoperative guidance, post-procedure assessment, and monitoring of novel pharmacologic therapies.

🔪Surgical Septal Myectomy — TEE Role

Pre

Pre-Bypass Assessment

IVS max thickness (anteroseptal + inferoseptal walls at end-diastole); longitudinal extent of septal thickness; distance from right coronary cusp to AML-septal contact point; anterior leaflet length (>16 mm/m² = elongated); rule out subaortic membrane and aortic stenosis. Best views: ME 4C and long-axis.

Post

Post-Bypass Assessment

Pharmacologic challenge (isoproterenol or dobutamine) to evaluate residual obstruction. LVOT velocity >3 m/s or significant SAM on provocation → return to bypass. Exclude complications: aortic regurgitation, VSD, coronary cameral fistula. Note: IVS measurements post-bypass may be inaccurate due to tissue edema.

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Extended myectomy required when hypertrophy extends to mid-LV or when MVO is present. Papillary muscle abnormalities (anomalous insertion, bifid) need unique treatment — papillary muscle release and realignment.

🍺Alcohol Septal Ablation — MCE Guidance

Identify Target Septal Perforator

Coronary CT angiography may pre-identify candidate vessel. At catheterization: balloon inflated in candidate perforator, contrast injected through balloon catheter.

Myocardial Contrast Echo (MCE) Verification

1–2 mL diluted agitated contrast + saline flush under continuous imaging. Target: basal septum opacification corresponding to SAM-septal contact zone. Document absence of perfusion in: LV anterolateral wall, RV free wall, papillary muscles.

Post-Procedure Imaging

Evaluate: septal thickness changes, LV dimensions and mass, systolic and diastolic function, MR degree, possible VSD. MCE use → shorter intervention time, less ethanol, lower heart block rate, higher success.

⚠️

Inappropriate targets (must not be opacified): distal septum, LV papillary muscles, RV papillary muscles. If MCE shows inappropriate opacification → abort or select different vessel.

💊Medical Therapy Monitoring

Standard Medical Therapy

Beta blockers & non-DHP calcium channel blockers — titrate based on clinical response; monitor for bradycardia and AV block

If symptomatic despite max β-blocker/CCB ± disopyramide → repeat echo to document resting/provocable gradient ≥50 mmHg before proceeding to CMI or SRT discussion

Reduced EF on GDMT: repeat echo to assess reverse remodeling, LV filling pressures, PA pressures. Repeat TTE every 1–2 years if stable.

Novel Therapies (Cardiac Myosin Inhibitors)

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Oral allosteric cardiac myosin inhibitors (CMIs): A new drug class that resets the equilibrium between the on and off state of myosin heads → reversible inhibition of actin-myosin cross-bridging, reducing LVOT obstruction.

LVEF monitoring is mandatory — risk of HF with reduced EF. Specific monitoring frequency and clinically relevant LVEF thresholds remain to be determined per evolving guidelines. Monitor LVEF at each dose titration and at regular intervals.

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Emerging evidence (beyond 2022 ASE guidelines): CMIs may be considered as an alternative to AV nodal therapies in patients who experience exertional limitations due to chronotropic incompetence while on AV nodal therapies. The MAPLE-HCM trial demonstrated superiority of CMIs vs. beta-blockers in head-to-head comparison, with beta-blockers causing functional/exercise capacity decrements — likely due to a dampened heart rate response. This is not reflected in the 2022 ASE guidelines but is supported by more recent evidence.

🔧TEER & Pacing — Imaging Role

Transcatheter Edge-to-Edge Repair (TEER)

Off-label in HCM; considered for patients with refractory symptoms, unacceptable surgical risk, and septal thickness <1.5 cm

Favorable baseline findings: SAM-related LVOTO, no calcification in grasping zone, mean transmitral gradient <5 mmHg, MVA ≥4 cm²

TEE critical for intraprocedural guidance — deep transgastric view to measure LVOT gradient before and after

Dual-Chamber Pacing

Not recommended for most HCM patients — may be considered in select patients with drug-refractory symptoms who are NOT candidates for SRT

Apical RV lead placement is optimal (maximally reduces LVOT gradient); TEE guidance can be used

CRT-D: echo supportive for response evaluation and AV delay optimization

Family Screening & Ischemia Assessment

Screening recommendations depend on age, presence of a known pathogenic variant, and whether there is early-onset disease in the family. Echocardiography is the initial imaging modality for all HCM screening.

🗺️Recommended Evaluation & Testing — HCM Family Screening

Adapted from the 2020 AHA/ACC HCM Guideline (Ommen et al.) and the ASE HCM Poster.

👨‍👩‍👧‍👦Screening Intervals — First-Degree Relatives

Age Group	Condition	Initiation	Interval
Children & adolescents	Genotype-positive family AND/OR early-onset HCM	At time of diagnosis in family member	Every 1–2 years
Children & adolescents	Without above 2 conditions	Any time after diagnosis in family (no later than puberty)	Every 2–3 years
Adults	Any first-degree relative	At time of diagnosis in family member	Every 3–5 years

Key Screening Points

All myocardial segments carefully examined for hypertrophy — no segment can be assumed normal

CMR if: technically challenging echo, abnormal ECG with apparently normal echo, or borderline LVH on echo

Genotype-positive / phenotype-negative individuals: crypts, increased WT/LVEDD ratio, elevated ECV, abnormal segmental strain may be early markers — limited data relating these to development of LVH

If family has known pathogenic/likely pathogenic variant → patient genetic testing first; if negative → no further testing (Class III: no benefit)

🫁Ischemia Assessment in HCM

Mechanisms of Ischemia

Increased O₂ demand: larger myocardial mass, elevated filling pressures

Decreased O₂ supply: microvascular dysfunction, medial hypertrophy of intramural arterioles

Myocardial bridges common (~50% on CCTA); may prolong coronary compression into diastole

CFR by PW Doppler in mid-LAD: reduced CFR associated with worse outcomes

Preferred Stress Perfusion Modalities

PET: preferred — attenuation correction, quantitative myocardial blood flow, shorter duration. Abnormal MBF reserve = independent predictor of clinical deterioration CMR Perfusion: high spatial resolution; correlates well with PET-derived MBF; multiparametric approach (perfusion + LGE + ECV) SPECT: limited by attenuation artifacts; suboptimal for wall motion assessment post-stress; relative (not absolute) perfusion only Stress Echo: wall motion abnormalities in HCM are multifactorial; NOT a reliable predictor of epicardial CAD

🩻Coronary Artery Disease Evaluation in HCM

Low

Low Pre-Test Probability (<15%)

Conservative initial approach; diagnostic yield is low. Consider calcium scan — clinically relevant CAD very rare without detectable coronary calcium. Persistent symptoms may necessitate further testing.

Int

Low-to-Intermediate Probability (15–50%)

CCTA preferred — evaluates epicardial CAD and myocardial bridging. Reference standard for anomalous coronary anatomy. Diagnostic performance in HCM similar to general cohorts. Note: CCTA tends to overestimate severity vs. invasive angiography.

High

High Probability or Known CAD (>50%)

Functional test (quantitative PET or CMR perfusion preferred over SPECT/stress echo). Reserve invasive angiography for severe CAD on CCTA (left main, triple vessel) or persistent symptoms. Functional assessment (FFR or CT-FFR) recommended before revascularization.

⚠️

Preprocedural nitroglycerin should be avoided when severe LVOTO is present before cardiac CT. CT-FFR not validated specifically in HCM — patients with higher myocardial mass may have lower CT-FFR values in distal vessels even without significant CAD.

Citation: Nagueh SF, Phelan D, Abraham T, et al. Recommendations for Multimodality Cardiovascular Imaging of Patients with Hypertrophic Cardiomyopathy: An Update from the American Society of Echocardiography, in Collaboration with the American Society of Nuclear Cardiology, the Society for Cardiovascular Magnetic Resonance, and the Society of Cardiovascular Computed Tomography. J Am Soc Echocardiogr. 2022;35:533–569.

📄 DOI: 10.1016/j.echo.2022.03.012 | American Society of Echocardiography

This interactive tool is for educational and clinical reference purposes only. It does not replace clinical judgment or individualized patient assessment. Always refer to the full guideline document for complete recommendations. Content © 2022 American Society of Echocardiography.