Basics
Description
- Hypertrophic cardiomyopathy (HCM):
- Genetic disorder affecting the sarcomere:
- Various mutations
- Many phenotypic variations
- Hypertrophied (regionally or globally), nondilated left or, rarely, right ventricle in the absence of another cause of degree of hypertrophy observed, such as hypertension or aortic stenosis
- 2 general types:
- Nonobstructive (HCM)-75% of patients. Estimated around 1% annual mortality
- Obstructive (HOCM)-25% of patients. More severe-estimated 2% annual mortality
- Manifests at all ages, from neonate to elderly:
- Most manifest in childhood and adolescence-pubertal growth spurt
- Usually more severe when diagnosed at younger age
- Small percent progress to reduced LV function
- Clinical presentation in mid and late life not uncommon
- May initially be misdiagnosed as asthma, COPD, deconditioning or sleep apnea
- Lethal arrhythmias more common in younger patients
- Most common cause of atraumatic death in young (<35 yo) athletes
- Supraventricular arrhythmias common with incidence increasing with age
- Atrial fibrillation both common and poorly tolerated
- Prevalence ~1 in 500 adults general population:
- Based on echocardiographic diagnosis
- Structural pathology:
- Irregular, marked ventricular wall thickening with disarray of myofibrils in the thickened regions and fibrin deposition:
- Affects higher-pressure LV more than right and, in obstructive form, if obstruction removed, hypertrophy decreases
- Some phenotypes have progressive wall thinning with age-usually associated with thicker wall early
- Thickening usually asymmetric involving the septum to a greater extent than the free ventricular wall
- Atrial dilatation secondary to diastolic filling stiffness
- Impaired microvascular dilation associated with intimal thickening and perivascular collagen deposition
- Outpatient long-term management
- Avoidance of volume depletion and elevated cardiac demand-depending on degree and location of hypertrophy
- Pharmacologic
- β-Blockers or verapamil to slow and control rate, thus prolonging diastole
- Implantable cardiac defibrillator
- In patients with history of syncope, cardiac arrest, family member with sudden death, asymptomatic nonsustained ventricular tachycardia (VT), abnormal BP response to exercise, massive hypertrophy
- Alcohol ablation of hypertrophic outflow-obstructing septal tissue
- Surgical septal myectomy-improving statistics with more centers performing
Risk Factors
Genetics
- 1st cardiac disorder for which genetic basis identified (1989)
- Autosomal-dominant inheritance:
- >10 associated genes found:
- Most encode proteins for sarcomere
- >700 distinct mutations recognized
- High penetrance
- Variable phenotypic expression
- Some genotypes significantly more lethal:
- Routine screening impractical at present
- Increasing complexity with more understanding of interplay between primary sarcomere abnormalities and other genetic and nongenetic factors
- Some mutations affect cell wall pumps-thus, association with dysrhythmias.
Etiology
See "Genetics."Ł á
Diagnosis
Signs and Symptoms
History
- Obstructive symptoms correlate with exertion or suddenly assuming upright position-activities that decrease venous return or ventricular filling.
- Severity depends on the location and degree of ventricular wall thickening.
- Shortness of breath
- Dyspnea on exertion
- Exertional or postprandial angina
- Presyncope
- Syncope
- CHF
- Cardiovascular collapse
- Dysrhythmias:
- Paroxysmal atrial fibrillation:
- Often leads to significant, rapid clinical deterioration when present with CHF
- Elevated CVA risk from clots
- Supraventricular tachycardia
- Nonsustained VT
- Bradydysrhythmia rare
- VT or ventricular fibrillation may lead to sudden death.
- Prior therapy for known HCM might include surgery or alcohol injection to reduce septal bulk:
- Potential for conduction blocks
- Potential septal rupture
- Known cases with higher risk of arrhythmia may have implanted defibrillators.
- Family history of sudden death without apparent cause or known HCM
Due to potential increasing severity in adolescence, any young child with syncope without clear cause, or in association with exercise, should have more extensive, focused history for familial sudden death (standard is 3 generations) and possible referral for evaluation. á
Physical Exam
- No or subtle physical findings
- Most findings in patients with outflow tract obstruction, variably:
- Loud, left-sided S4
- Double apical cardiac impulse at the mid to upper sternum
- Murmur:
- Crescendo-decrescendo midsystolic murmur at the left sternal edge
- Radiation to aortic and mitral areas, not to neck or axilla
- Increasing in intensity with Valsalva maneuver or standing up
- Quieter with recumbency, squatting, or handgrips
- Frequent associated mitral regurgitation
- With more severe obstruction, a more apparent murmur with radiation to the left sternal border
- Radiation to the axilla if there is associated mitral insufficiency
Diagnosis Tests & Interpretation
ECG findings: á
- Abnormal in >90% pts with HCM
- T-wave inversion >1 mm 2 or + leads V2-V6, II and aVF, or I and aVL or deep TWI in V4-V6 in non-African-Caribbean descent athletes >16 yo
- ST-segment depression >0.5 mm in 2 or more leads requires further investigation
- Q-waves >3 mm in depth or >40 ms duration in at least 2 leads other than III & aVR
- P-wave >120 ms leads I or II with negative portion ≥1 mm and ≥40 ms in lead V1
- Nonspecific IVCD >140 ms
Lab
- Clinical lab testing is of no assistance.
- Genetic testing may help in outpatient workup, but not in ED.
Imaging
- CXR:
- Normal in the vast majority
- Bulge along left heart border representing hypertrophy of free wall of LV
- Right or left atrial enlargement
- Pulmonary vascular redistribution
- Transthoracic cardiac echo/Doppler:
- LV wall >15 mm, with normal or small LV cavity (13-14 mm with other features; e.g., family
history in adults), in children ≥2 times standard deviation above mean for age, sex, size - Systolic outflow obstructions
- Diastolic filling abnormalities
- Cardiovascular magnetic resonance (CMR)
- Supplements ECHO
- Allows more structural detail for evidence of fibrosis
- Stress thallium and PET evaluate ischemia.
Diagnostic Procedures/Surgery
No ED-based procedures are of diagnostic utility. á
Differential Diagnosis
- Vagal and other causes of syncope and presyncope
- Heatstroke
- Aortic stenosis
- Pulmonic stenosis
- Ventricular septal defect
- Mitral regurgitation
- Mitral valve prolapse
- Arteriosclerotic coronary vascular disease
- Differentiate in patients presenting with CHF or angina:
- More ominous in the setting of HCM
Treatment
Consider HCM in patients who decompensate during standard treatments for CHF, ischemia, or supra-VT, and in young athletes who collapse during or just after exertion-rule out heat stroke. HCM patients may decompensate with IV fluids due to diastolic stiffness. á
Initial Stabilization/Therapy
- ABCs
- IV catheterization
- Supplemental oxygen
- Cardiac monitor
- Pulse oximetry
Ed Treatment/Procedures
- Depends on type of presentation: Dysrhythmia, cardiac failure, chest pain or ischemia
- Underlying principle to understand sensitivity to any situation that may impair cardiac filling.
- Patient may need to remain supine.
- Standard CHF or anginal vasodilator therapy may lead to cardiovascular collapse; if this occurs, treat with fluid bolus.
- Attention to any hypovolemia as small degree may significantly impair cardiac output.
- Control rate and improve diastolic filling (underlying principle in treating HCM-associated CHF and angina):
- β-Blockers:
- Mainstay of therapy
- Decrease dysrhythmias and lower elevation of pressure gradient across the LV outflow tract
- Calcium channel blockers:
- Verapamil reduces obstruction by decreasing contractility and improving diastolic relaxation and filling.
- Nifedipine relatively contraindicated due to vasodilatation
- Dysrhythmia management:
- β-Blockers and calcium channel blockers 1st line for supraventricular dysrhythmias
- Amiodarone:
- Drug of choice for ventricular dysrhythmias
- Used when β-blockers and calcium channel blockers fail
- Electrical cardioversion:
- Use early in HCM with new atrial fibrillation and CHF
Medication
All medications must be assessed for effect in face of possible outflow track restriction á
- Amiodarone: 150 mg over 10 min, then 360 mg over 6 hr, then 540 mg over next 18 hr (peds: 5 mg/kg IV rapid IV/IO bolus, off-label use per manufacturer, but class IIb for VT with a pulse and class indeterminate for VF and pulseless VT, per American Heart Association. Do not use in infants.)
- Propranolol: 1-3 mg (peds: 0.01-0.1 mg/kg slow IV push over 10 min; not to exceed 1 mg/dose) slow IV bolus
- Verapamil: 2.5 mg (peds: >1 yr: 0.1-0.2 mg/kg/dose over 2 min; repeat q10-30min as needed; not to exceed 5 mg/dose [1st dose] or 10 mg/dose [2nd dose]) IV bolus over 1-2 min, may repeat as 5 mg in 15-30 min
- Phenylephrine: 0.1-0.2 mg (peds: 1-20 ╬╝g/kg) IV slow bolus for severe hypotension (shock) not responding to fluid bolus. Repeat in 10-15 min as needed or start IV drip to titrate to BP; or other pure vasoconstrictor (i.e., no inotropic effect). Maintenance dose: 0.05 ╬╝g/kg/min (peds: 0.1-0.5 ╬╝g/kg/min) IV
First Line
N/A á
Second Line
Diltiazem: 0.25 mg/kg (peds: Contraindicated <12 yr old) IV over 2 min; may repeat in 15 min at 0.35 mg/kg á
Follow-Up
Disposition
Admission Criteria
- Unexplained syncope, especially in younger adults.
- ICU admission:
- Syncopal episodes
- CHF
- Angina
- Hemodynamically significant tachydysrhythmia
Discharge Criteria
When increased myocardial wall thickness is an incidental finding during the ED evaluation for another presentation with: á
- No history of familial sudden death (proposed guidance-3 generations to rule out in face of suspicion) or personal history of syncope
- Need urgent follow-up with a cardiologist
- Counsel against any activities that may decrease diastolic filling pending follow-up:
- Counsel against physical exertion until evaluated by cardiologist
Issues for Referral
See "Discharge Criteria."Ł á
Followup Recommendations
See "Discharge Criteria."Ł á
Pearls and Pitfalls
- Increasing awareness of genetic and phenotypic variants with implications in definition of "normal variant"Ł:
- Some authors advocate cardiac ECHO screening for any youth participation in sports.
- Some authors advocate AICD at diagnosis.
- If HCM is considered in a patient with syncope, it must be ruled out because it is much more likely to be fatal with repeat episodes.
Additional Reading
- Bos áJM, Ommen áSR, Ackerman áMJ. Genetics of hypertrophic cardiomyopathy: One, two, or more diseases? Curr Opin Cardiol. 2007;22(3):193-199.
- Drezner áJA, Ashley áE, Baggish áAL, et al. Abnormal electrocardiographic findings in athletes: Recognising changes suggestive of cardiomyopathy. Br J Sports Med. 2013;47(3):137-152.
- Elliott áP, McKenna áWJ. Hypertrophic cardiomyopathy. Lancet. 2004;363(9424):1881-1891.
- Gersh áBJ, Maron áBJ, Bonow áRO, et al. 2011 ACCF/AHA guideline for the diagnosis and treatment of hypertrophic cardiomyopathy: A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. J Thorac Cardiovasc Surg. Vol 142. United States 2011:e153-e203.
- Maron áBJ, McKenna áWJ, Danielson áGK, et al. American College of Cardiology/European Society of Cardiology clinical expert consensus document on hypertrophic cardiomyopathy. A report of the American College of Cardiology Foundation Task Force on Clinical Expert Consensus Documents and the European Society of Cardiology Committee for Practice Guidelines. J Am Coll Cardiol. 2003;42(9):1687-1713.
- Maron áBJ, Seidman áJG, Seidman áCE. Proposal for contemporary screening strategies in families with hypertrophic cardiomyopathy. J Am Coll Cardiol. 2004;44(11):2125-2132.
- Roberts áR, Sigwart áU. Current concepts of the pathogenesis and treatment of hypertrophic cardiomyopathy. Circulation. 2005;112(2):293-296.
- Spirito áP, Autore áC. Management of hypertrophic cardiomyopathy. BMJ. 2006;332(7552):1251-1255.
Codes
ICD9
425.18 Other hypertrophic cardiomyopathy á
ICD10
I42.2 Other hypertrophic cardiomyopathy á
SNOMED
- 233873004 Hypertrophic cardiomyopathy (disorder)