Burned-out phase of hypertrophic cardiomyopathy
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The burned-out phase of hypertrophic cardiomyopathy refers to the end-stage of hypertrophic cardiomyopathy and is characterized by myocardial fibrosis, systolic dysfunction and left ventricular wall thinning.
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The burned-out phase can be seen in 3-5% of patients with hypertrophic cardiomyopathy 1-3.
In patients with a known diagnosis of hypertrophic cardiomyopathy the burned-out phase can be made by the development of systolic dysfunction (left ventricular ejection fraction <50%) 1-4.
In patients in which the clinical history of hypertrophic cardiomyopathy is not known, this is a diagnosis of exclusion 1.
Patients with burned-out or end-stage hypertrophic cardiomyopathy may present with variable symptoms including palpitations, dyspnea on exertion, syncope or cardiac arrest 1.
Complications of burned-out phase hypertrophic cardiomyopathy include 1-5:
- atrial fibrillation
- thromboembolic events
- progressive heart failure
- ventricular tachyarrhythmias
- sudden cardiac death
The late stages of hypertrophic cardiomyopathy are characterized by progressive adverse cardiac remodeling and myocardial fibrosis leading to the following features 1-4:
- decreased contractility and impaired systolic function
- decreased wall-thickness and wall-thinning
- increased end-systolic dimensions
- the disappearance of left ventricular gradients
Hypertrophic cardiomyopathy can progress to the following burned-out phase subtypes 1,3:
- dilated form with left ventricular dilation
- restrictive form with atrial dilation
Imaging findings at this stage are heterogeneous and can be non-specific, the cardiac wall might not be thickened and hypertrophic anymore but dilated and thin or might show a mixture of thickened and thinned wall elements 1-4.
Echocardiography serves as a first-line method. It will reveal both diastolic and systolic dysfunction 1,5 and might show a decrease in left ventricular gradients. It might be the only available method in unstable patients or those in critical clinical condition 1.
Cardiac MRI will reveal cardiac dysfunction and extensive late gadolinium enhancement indicating replacement fibrosis or myocardial scarring 1,3-7.
- wall motion abnormalities
- decreased ejection fraction
cardiac tissue characterization
- T1 mapping: increased native T1 values
- ECV: increased
- diffuse and extensive late gadolinium enhancement
- might show complications as intracardiac thrombi
The radiological report should include a description of the following 1:
- cardiac volumes and measurements including left ventricular mass
- cardiac wall motion abnormalities
- the extent of myocardial fibrosis and myocardial scarring
- complications as intracardiac thrombus formation
Treatment and prognosis
Not unexpected the burned-out phase features an unfavorable outcome with increased mortality of approximately 10-12% per year due to thromboembolic complications, progressive heart failure and an increased incidence of sudden cardiac death 1. Diffuse and extensive myocardial fibrosis visualized by late gadolinium enhancement (>15% wall mass) is associated with an increased risk of sudden cardiac death 8.
Management comprises pharmacotherapy including ACE inhibitors, β-blockers and diuretics. Patients might also benefit from an implantable cardioverter-defibrillator especially in the setting of concomitant arrhythmia. Cardiac transplantation might be considered as definite therapy at this stage 1,3.
Conditions that might mimic the clinical presentation or imaging appearance of burned-out phase hypertrophic cardiomyopathy include 1,5-7:
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