Hypertrophic CM Flashcards
What characterizes hypertrophic cardiomyopathy?
LV hypertrophy + absence of another cardiac, systemic, or metabolic disease producing the magnitude of hypertrophy
What is the prevelance of hypertrophic CM?
0.20%
How is hypertrophic CM passed on?
Autosomal dominant with variable expression and age-releated penetrance
What is the pathophysiology of hypertrophic CM?
11 different sarcomeric mutations have been identified but only 30% of hypertrophic CM patients have a genetic etiology
Who should get tested for hypertrophic CM?
Hypertrophic CM screening is recommended for 1st-degree and other close relatives; they should get an echo and a cardiac MRI (not genetic testing)
What is the histologic pathognomonic finding for hypertrophic CM?
Myocardial fiber disarray with interstitial and perivascular fibrosis
What is the most common phenotypic variant for hypertrophic CM?
Asymmetric hypertrophy (septum and anterior wall, 70%) > isolated basal septal hypertrophy (15-20%) > midventricdular septal hypetrophy (8-10%) > apical hypertrophy (<2%)
Who do you see apical hypertrophy more often in?
East Asian patients (<2% of overall patients)
What is the most common location of hypertrophy in hypertrophic CM?
Basal anterior septum with continuity with the anterior free wall
What are patients with hypertrophic CM at risk for?
Sudden cardiac death, LVOT obstruction, diastolic dysfunction, heart failure with systolic dysfunction, ventricular arrhythmias, atrial fibrillation with increased risk of stroke
What imaging findings are suggestive of increased risk of sudden cardiac death in patients with hypertrophic CM?
- Massive LVH (>/= 30mmHg)
- LV apical aneurysm
- systolic dysfunction (LVEF <50%)
- history of suspected cardiac syncope or family history of sudden cardiac death
Which patients with hypertrophic CM are at a higher risk of lifelong adverse events?
Patients with pathogenic sarcomeric gene variants and those diagnosed earlier in life
What % of patients have LVOT obstruction with hypertrophic CM?
75%
What is the peak LVOT gradient indicative of obstruction?
> /= 30mmHg (>/= 50mmHg is severe obstruction)
What is the most common cause of obstruction in hypertrophic CM?
Mitral-septal contact secondary to systolic anterior motion (SAM)
What are the principal mechanisms responsible for LVOT obstruction?
- Septal hypertrophy with narrowing of the LVOT; 2. Anatomic alterations in the MV apparatus (i.e. longer leaflets, anterior displacement of the pap muscles and MV apparatus)
What does systolic anterior motion of the MV lead to?
LVOT obstruction and MR (due to loss of leaflet coaptation)
What do you see on CW through the AV with LVOT obstruction?
Dagger-shaped or Shark-toothed profiled
What are other causes of LVOT obstruction outside of SAM?
- Anomalous papillary muscle (causes obstruction because of systolic apposition of the pap muscle and septum); 2. Apical hypertrophic CM (systolic apposition of the mid-LV walls leads to apical blood trapping with high apical chamber pressures leading to apical akinesis)
Why does diastolic dysfunction occur with hypertrophic CM?
Secondary to myocardial hypertrophy + ischemia + fibrosis + delayed inactivation from abnormal intracellular Ca reuptake + altered systolic-diastolic coupling
What does the MR jet look like with SAM?
The regurgitant jet is during mid-systole and posteriorly or laterally directed
Why do you get myocardial ischemia with hypertrophic CM?
Mismatch between O2 supply and demand; there is hypertrophy and microvascular dysfunction with impaired coronary flow reserve + arteriolar intimal and medial hyperplasia + myocardial bridging
What is myocardial bridging?
Overlying myocardial causing systolic compression of an epicardial coronary artery (can impair blood flow and cause ischemia)
What types of autonomic dysfunction do you see with hypertrophic CM?
Impaired HR recovery + inappropriate vasodilation + abnormal BP response to exercise (failure to increase SBP by 20mmHg or a drop in SBP during exercise > 20mmHg is a poor prognostic factor)
What is the rate of cardiac death due to hypertrophic CM in young athletes?
1/3 of non-trauma-related sudden cardiac death in young, asymptomatic athletes
How is hypertrophic CM diagnosed?
Echo and/or cardiac MRI
What increases your risk of LVOT obstruction?
Increased contractility (i.e. high catecholamine states) + decreased preload + decreased afterload + increased HR + absence of atrial kick
What do you see on echo in hypertrophic CM?
Increased LV wall thickness + LVOT obstruction + quantitative peak LVOT gradients + MR
What do you see on cardiac MRI in hypertrophic CM?
- Increased ventricular wall thickness (better than echo)
- Morphologic features in gene carriers with LVH (i.e. blood-filled myocardial crypts, elongated mitral leaflets, expanded extracellular space)
- Quantify LV mass
- Myocardial tissue scarring/fibrosis via late gadolinium enhancement
What are common pharmacologic interventions to treat hypertrophic CM patients?
Beta blockers (first line), calcium channel blockers, disopyramide
What procedures can help with hypertrophic CM patients?
Septal reduction therapy such as surgical septal myectomy or alcohol septal ablations + dual chamber pacing (via a short AV delay –> significantly reduces outflow tract gradients; not a first line treatment though)
What treatment option for hypertrophic CM prolongs life expectancy?
ICD therapy (Class 1a in patients with hypertrophic CM with cardiac arrest or sustained VT and Class 2a in patients with one of the following: massive LV hypertrophy (>/= 30mm), history of suspected cardiac syncope, LV apical aneurysm, systolic dysfunction with LVEF < 50%, or family history of sudden cardiac death due to hypertrophic CM)
When is an ICD placement considered a Class 2b indication for hypertrophic CM?
In adults with non-sustained VT or in patients with extensive late gadolinium enhancement on cardiac MRI
Should you place an ICD in a child who has non-sustained VT due to hypertrophic CM?
Class 2a so it is reasonable to
What are the indications for surgical myectomy for hypertrophic CM?
NYHA functional class III or IV AND severe resting or provoked LVOT obstruction (>/= 50 mmHg) despite maximal medical treatment
What is the mortality rate of a septal myectomies at experienced centers?
<1%
What are the complications of septal myectomies?
Complete heart block + LBBB + VSDs
On TEE after septal myectomies, how do you tell the difference between a VSD and septal perforators?
Septal perforators will show color flow during diastole while VSDs will have color flow during systole
When should a patient get an alcohol septal ablation for hypertrophic CM?
Severe symptoms despite optimal medical therapy + poor surgical candidates
What is better, septal myectomies or alcohol septal ablations?
Septal myectomies are superior
How is an alcohol septal ablation performed?
Prominent anteroseptal-perforating branch of the LAD supplying the hypertrophied portion of basal septum is injected with 1-3cc of ethanol
What are complications of alcohol septal ablations?
Increased risk of AV block (mostly RBBB) + LAD dissection + reflux of alcohol back into the LAD resulting in massive anterior infarction
