Cardiomyopathy, Hypertrophic
Basics
Description
Description
- Genetic disorder affecting the sarcomere
- Clinical diagnostic criteria: Hypertrophied (regionally or globally), nondilated left in the absence of another cause of degree of hypertrophy observed, such as hypertension or aortic stenosis
- Hypertrophic cardiomyopathy (HCM) unifies over 75 different names historically used
- 2 general types:
- Obstructive – ≥30 mm Hg left ventricular outflow tract gradient:
- 67% of patients
- More severe – estimated 2% annual mortality
- Nonobstructive – <30 mm Hg gradient:
- 33% of patients
- Estimated around 1% annual mortality
- Obstructive – ≥30 mm Hg left ventricular outflow tract gradient:
- Global disease – >50 countries, all race/ethnic groups
- 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
- Average age of diagnosis in fifth decade:
- CHF 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) persons, not just athletes
- Most common cause of sudden death in athletes
- Supraventricular arrhythmia incidence increases with age:
- Atrial fibrillation both common and poorly tolerated
- Stroke is a high-risk complication
- Prevalence at least 1 in 500 adults:
- Based on echocardiographic population studies
- Much smaller number present for care, suggesting many undiagnosed with possible minimal to no adverse effect from phenotypic variety
- 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 outflow obstruction
- Atrial dilatation secondary to diastolic filling stiffness increased risk for atrial fibrillation
- Impaired microvascular dilation associated with intimal thickening and perivascular collagen deposition increased risk for angina
- Irregular, marked ventricular wall thickening with disarray of myofibrils in the thickened regions and fibrin 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
GeneticsRisk Factors
- First cardiac disorder for which genetic basis identified (1989)
- Autosomal-dominant inheritance:
- >10 associated genes found:
- Encode proteins of cardiac sarcomere
- >1,500 distinct mutations recognized
- High penetrance
- >10 associated genes found:
- Highly variable phenotypic expression
- Some genotypes significantly more lethal:
- Routine screening impractical at present:
- Mutations do not predict individual clinical course
- Screening routine for patient family members
- Mutation negative – no need for further evaluation or follow-up
- Mutation positive w/no LV hypertrophy – very likely to develop phenotypic manifestation in adulthood – close follow-up recommended, possible intervention
- 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
Etiology
See Genetics
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Citation
Schaider, Jeffrey J., et al., editors. "Cardiomyopathy, Hypertrophic." 5-Minute Emergency Consult, 6th ed., Lippincott Williams & Wilkins, 2020. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307578/all/Cardiomyopathy__Hypertrophic.
Cardiomyopathy, Hypertrophic. In: Schaider JJJ, Barkin RMR, Hayden SRS, et al, eds. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307578/all/Cardiomyopathy__Hypertrophic. Accessed December 5, 2024.
Cardiomyopathy, Hypertrophic. (2020). In Schaider, J. J., Barkin, R. M., Hayden, S. R., Wolfe, R. E., Barkin, A. Z., Shayne, P., & Rosen, P. (Eds.), 5-Minute Emergency Consult (6th ed.). Lippincott Williams & Wilkins. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307578/all/Cardiomyopathy__Hypertrophic
Cardiomyopathy, Hypertrophic [Internet]. In: Schaider JJJ, Barkin RMR, Hayden SRS, Wolfe RER, Barkin AZA, Shayne PP, Rosen PP, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. [cited 2024 December 05]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307578/all/Cardiomyopathy__Hypertrophic.
* Article titles in AMA citation format should be in sentence-case
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