Hypertrophic Obstructive Cardiomyopathy

Question 1

3 features of HOCM

Answer 1

1. Assymetic septal hypertrophy
   -The septal thickness is usually greater than 15 mm.
   -The hypertrophy is usually asymmetric involving the septum and the anterolateral wall with a septal-to-posterior wall thickness ratio of greater than 1.3:1, and more specifically greater than 1.5:1
2. LVOT obstruction
   -Characterized by septal hypertrophy that narrows the LVOT
   -The obstruction is dynamic, and worsens with reduced LV volume or increased LV contractility
   -A significant obstruction is characterized by a resting gradient greater than 30 mmHg or a gradient greater than 50 mmHg with provocative maneuvers
3. Systolic anterior motion of the MV
   -The increased velocity across the LVOT draws the anterior mitral leaflet during systole, which further narrows the LVOT and creates LVOT obstruction.

Question 2

How to get HOCM gradient

Answer 2

Presence of a gradient between the LV and the aorta

Endhole catheter and slowly pullback across the LV to localize the pressure gradient.

Question 3

Hemodynamics of HOCM in terms of LV and aortic pressure tracing

Answer 3

1. Aortic pressure - SPIKE AND DOME
   -LVOT obstruction is dynamic and is less severe in early systole when LV volume is largest, explaining the “peak” in aortic pressure. Obstruction is worst in mid and late systole when LV volume is reduced
2. LV pressure - DAGGER SHAPE
   -Because the LV obstruction is worse in late systole, LV pressure proximal to the obstruction peaks late and has a late-peaking “dagger” shape

Question 4

Difference of HOCM in AS in terms of AS and LV tracing

Answer 4

In HOCM - early aortic pressure peaking, the late LV pressure peaking, and the late gradient in HOCM

In AS - aortic pressure peaks late and the LV pressure peaks sooner.

Question 5

After a premature beat, LV volume increases leading to increased LV contractility and therefore increased LVOT obstruction. While LV pressure increases, the stroke volume decreases and thus the aortic pulse pressure decreases

Answer 5

Braunwald-Brockenbrough-Morrow sign

Question 6

In general, the gradient in HOCM increases
1.
2.
3.

Answer 6

1. Decreased preload (Valsalva maneuver, hypovolemia, NTG)
2. Decreased afterload (Vasodilators)
3. Increased contratility (Exercise, inotropic drugs such as Dobutamine)

Question 7

Predictors of SCD in adult patientsnwith HOCM

Answer 7

1. Massive hypertrophy (wall thickness approaching or exceeding 30 mm)
2. Family history of SCD in first-degree relatives younger than the age of 40 to 50
3. Arrhythmogenic syncope
4. LV systolic dysfunction
5. LV apical aneurysm
6. NSVT (more important for younger patients or when the runs of NSVT are frequent, longer, and/or faster.)
7. Extensive late gadolinium enhancement (LGE) on CMR indicates scarring in the LV wall

Question 8

Myectomy or alcohol septal ablation is indicated for a peak instantaneous LVOT gradient ____________ at rest or with physiological maneuvers (even if there is no gradient at rest), septal hypertrophy >18 mm, and refractory symptoms despite medical treatment.

Answer 8

> 50 mm Hg

Question 9

Adequate response to septal ablation in HOCM

Answer 9

A reduction of the resting gradient to <30 mmHg and a greater than 50% reduction of the provocable gradient

A biphasic response of the gradient is observed after alcohol septal ablation. An acute response with a striking gradient reduction (probably due to stunning of the myocardium) is followed by a gradient rise to about 50% of the preprocedural level the next day, then a progressive septal remodeling and great reduction of the gradient over 6 to 12 months.