HOCM

Question 1

What is the diagnostic definition of hypertrophic cardiomyopathy (HCM)?

Answer 1

Left ventricular (LV) hypertrophy ≥15 mm without identifiable cause (e.g., no valvular disease or severe hypertension).

Question 2

What percentage of HCM cases are familial, and what is the inheritance pattern?

Answer 2

50% are familial, inherited in an autosomal dominant pattern with high penetrance.

Question 3

What is the prevalence of HCM in the general population?

Answer 3

Approximately 1 in 500.

Question 4

What is the typical septal thickness in HCM, and when is 13–14 mm diagnostic?

Answer 4

≥15 mm is typical; 13–14 mm is diagnostic if there is a family history or positive genetic test.

Question 5

What is the typical septal-to-posterior wall thickness ratio in HCM?

Answer 5

> 1.3:1, or more specifically >1.5:1.

Question 6

Which LV wall is least frequently involved in HCM?

Answer 6

The posterior wall.

Question 7

What is concentric hypertrophy, and how often does it occur in HCM?

Answer 7

Symmetric thickening involving the posterior wall; occurs in 10–20% of cases.

Question 8

What is the mechanism of LVOT obstruction in HOCM?

Answer 8

Systolic anterior motion (SAM) of the anterior mitral leaflet causes dynamic narrowing of the LVOT.

Question 9

What defines significant LVOT obstruction?

Answer 9

Resting gradient >30 mmHg or >50 mmHg with provocation.

Question 10

What percentage of HCM patients have resting obstruction?

Answer 10

About 30%

Question 11

What percentage of HCM patients show obstruction only with provocation?

Answer 11

About 45%.

Question 12

What is the primary mechanism of MR in HOCM?

Answer 12

SAM of the anterior mitral leaflet causes posteriorly directed MR.

Question 13

When is MR severe in HOCM?

Answer 13

When the posterior leaflet is too short to coapt with the anterior leaflet.

Question 14

What murmur is associated with MR in HOCM?

Answer 14

Holosystolic, blowing murmur at the apex, worsened by Valsalva.

Question 15

Name three structural mitral valve abnormalities that aggravate SAM.

Answer 15

Anterior leaflet elongation >30 mm
Anterior/central papillary muscle malposition
Chordal insertion at the leaflet base

Question 16

What type of mitral valve abnormality may directly cause obstruction?

Answer 16

Papillary muscle insertion directly onto the anterior leaflet.

Question 17

What characterizes apical HCM?

Answer 17

Apical thickening, more common in Asians, may evolve into aneurysm, mortality up to 4% yearly.

Question 18

At what age does the HCM phenotype typically develop?

Answer 18

Late adolescence or early adulthood.

Question 19

Class IIb indication for ICD in HOCM?

Answer 19

NSVT (≥10 beats, fast, ≥3x in 48h), or LGE ≥15% on MRI.

Question 20

Class IIa indications for ICD in HOCM?

Answer 20

Family history of SCD
Massive LVH ≥30 mm
Recent unexplained syncope
LVEF <50% or apical aneurysm

Question 21

Absolute indication (Class I) for ICD in HCM?

Answer 21

Prior SCD or sustained VT.

Question 22

In which patients is alcohol ablation less effective?

Answer 22

Age <65, septal thickness >25 mm, LVOT gradient >100 mmHg.

Question 23

What complication is more common with alcohol septal ablation?

Answer 23

RBBB, AV block, VT/VF.

Question 24

Which has better symptom control and lower recurrence?

Answer 24

Surgical myectomy (>90% success, lower arrhythmia risk).

Question 25

Indications for septal reduction therapy in HOCM?

Answer 25

NYHA III/IV symptoms, gradient >50 mmHg, septal thickness ≥16 mm, recurrent syncope.

Question 26

What is avoided in acute decompensated HOCM?

Answer 26

Inotropes (increase obstruction).

Question 27

What if hypotension is also present?

Answer 27

IV fluids + α-agonists (increase afterload → ↓ LVOT obstruction)

Question 28

First-line acute treatment for HOCM with pulmonary edema?

Answer 28

IV β-blockers.

Question 29

What antiarrhythmic is avoided in HCM with AF and why?

Answer 29

Digoxin—due to its positive inotropic effect.

Question 30

Should anticoagulation be used in HCM with AF regardless of CHADS2?

Answer 30

Yes, lifelong anticoagulation is warranted.

Question 31

What is the preferred management strategy for AF in HCM?

Answer 31

Rhythm control (amiodarone, disopyramide, ablation).

Question 32

What is the exception for diuretics in HOCM?

Answer 32

Small doses may be used cautiously in HTN or volume overload (Class IIb).

Question 33

Why should vasodilators and diuretics be avoided in HOCM?

Answer 33

They reduce preload/afterload → worsen LVOT obstruction.

Question 34

What novel drug reduces LVOT gradients in HOCM?

Answer 34

Mavacamten (myosin inhibitor).

Question 35

Which drug is added to β-blockers for high resting gradients?

Answer 35

Disopyramide (potent negative inotrope).

Question 36

When is verapamil preferred over β-blockers?

Answer 36

In patients with mild gradients or β-blocker intolerance (avoid in severe HF).

Question 38

What is the first-line medication for HOCM?

Answer 38

β-blockers (target HR ~60 bpm).

Question 39

What ECG feature helps differentiate amyloidosis from HCM?

Answer 39

Low voltage on ECG (seen in amyloidosis).

Question 40

How often should first-degree relatives be screened if genotype is unknown?

Answer 40

Yearly from adolescence to 21, then every 5 years.

Question 41

What should be done if an index patient tests positive genetically?

Answer 41

First-degree relatives should be tested for that specific mutation.

Question 42

Does a dobutamine-induced gradient confirm HCM?

Answer 42

No; it may appear in normal patients.

Question 43

What LA finding supports HCM diagnosis?

Answer 43

Left atrial enlargement (normal LA makes HCM unlikely).

Question 44

What does SAM look like on M-mode echo?

Answer 44

Anterior mitral leaflet contact with septum for >30% of systole.

Question 45

What is the Brockenbrough phenomenon?

Answer 45

Aortic pulse pressure falls after a premature beat in HOCM, due to increased obstruction.