Hypertrophic cardiomyopathy natural history

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [mailto:mgibson@perfuse.org];

Overview
The natural history of hypertrophic cardiomyopathy is quite variable. Signs and symptoms range from none, to atrial fibrillation, to heart failure, to embolic stroke, to sudden cardiac death. Signs and symptoms are quite variable from individual to individual but are also quite variable within a given family (all of whom carry the same mutation). The disease is quite variable in the timing of its appearance and may appear anywhere from infancy to late in adult life. About 25% of HCM patients achieve normal longevity. The myosin binding proteins C genetic variant carries a good prognosis. The presence of VT / VF carries the poorest prognosis. The severity of the outflow gradient is also related to prognosis. Athletes should be screened for HOCM based upon a family history of sudden cardiac death and a murmur on physical examination. Electrocardiograms and echocardiograms are not cost effective screening tools in this population with a low pre-test probability of disease.

Time and Age Dependent Appearance of Left Ventricular Hypertrophy
Left ventricular hypertrophy may be absent in childhood. It may then appear following the rapid growth of adolescence and may first appear at age 17 to 18.

Sudden Cardiac Death
The incidence of sudden cardiac death (SCD) in patients with HCM is 2 to 4 percent per year in adults, and a 4 to 6 percent per year in children and adolescents.

Among end stage patients with a left ventricular ejection fraction < 50%, the risk of SCD over 5 years may be as high as 47%. In this population, syncope has been identified as an independent correlate of sudden cardiac death (hazard ratio = 6.15; 95% confidence interval, 2.40-15.75; P < .001).

A review of 78 patients with HCM who died suddenly or survived a cardiac arrest episode showed that 71 percent were younger than 30 years of age, 54 percent were without functional limitation, and 61 percent were performing sedentary or minimal physical activity at the time of cardiac arrest.

Predictors of Sudden Cardiac Death
There are few predictors of SCD in patients with HCM.
 * Onset of symptoms in childhood.
 * A clinical history of spontaneous, sustained monomorphic ventricular tachycardia (VT) or sudden death in family members.
 * History of impaired consciousness
 * Syncope
 * Atrial arrhythmias
 * Development of systolic dysfunction
 * Non-sustained ventricular tachycardia (NSVT) in patients with symptoms
 * Left ventricular wall thickness >30 mm. A recent report of 480 patients showed that left ventricular wall thickness was useful in identifying patients at high risk for sudden cardiac death. However, sudden cardiac death can occur in children and adolescents in the absence of left ventricular hypertrophy as well.

Prognosis in Survivors of Sudden Cardiac Death
Survivors of SCD have a poor prognosis. Event free survival at 1,5 and 10 years was 83, 65 and 53 percent respectively.

2011 ACCF/AHA Guideline Recommendations: SCD Risk Stratiﬁcation
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Class I
1. All patients with HCM should undergo comprehensive SCD risk stratiﬁcation at initial evaluation to determine the presence of the following: (50,53,55,127,128,386–392)


 * a. A personal history for ventricular ﬁbrillation, sustained VT, or SCD events, including appropriate ICD therapy for ventricular tachyarrhythmias.† (Level of Evidence: B)


 * b. A family history for SCD events, including appropriate ICD therapy for ventricular tachyarrhythmias.† (Level of Evidence: B)


 * c. Unexplained syncope. (Level of Evidence: B)


 * d. Documented NSVT deﬁned as 3 or more beats at greater than or equal to 120 bpm on ambulatory (Holter) ECG. (Level of Evidence: B)


 * e. Maximal LV wall thickness greater than or equal to 30 mm. (Level of Evidence: B)

Class IIa
1. It is reasonable to assess blood pressure response during exercise as part of SCD risk stratiﬁcation in patients with HCM.(89,127,390) (Level of Evidence: B)

2. SCD risk stratiﬁcation is reasonable on a periodic basis (every 12 to 24 months) for patients with HCM who have not undergone ICD implantation but would otherwise be eligible in the event that risk factors are identiﬁed (12 to 24 months).(Level of Evidence: C)

Class IIb
1. The usefulness of the following potential SCD risk modiﬁers is unclear but might be considered in selected patients with HCM for whom risk remains borderline after documentation of conventional risk factors:


 * a. CMR imaging with LGE.(184,188) (Level of Evidence: C)


 * b. Double and compound mutations (i.e., >1). (Level of Evidence: C)


 * c. Marked LVOT obstruction.(45,127,143,390) (Level of Evidence: B)

Class III (Harm)
1. Invasive electrophysiologic testing as routine SCD risk stratiﬁcation for patients with HCM should not be performed. (Level of Evidence: C)}}

Guideline Resources
2011 ACCF/AHA Guideline for the Diagnosis and Treatment of Hypertrophic Cardiomyopathy