Question: which are the risk factors for sudden cardiac death in patients with hypertrophic cardiomyopathy?

Context:
Cardiac magnetic resonance (CMR) is used in the diagnosis and risk stratification of hypertrophic cardiomyopathy (HCM) and can detect myocardial replacement fibrosis (anindependent predictor of adverse cardiac outcomes) using late gadolinium enhancement (LGE). 
J wave is associated with increased risk of sudden cardiac arrest in patients with hypertrophic cardiomyopathy.
The J wave may be a risk factor for SCA in patients with HCM.
Extreme left ventricular hypertrophy was the most common risk factor present (alone or in combination with other markers) in patients experiencing primary prevention interventions (17 of 26 [65%]).
Extreme left ventricular hypertrophy was most frequently associated with appropriate interventions.
In conclusion, it is demonstrated that LGE has incremental value in addition to clinical risk factors for risk stratification and management of patients with HC.
Fibrosis as detected by CMR should be evaluated as an additional risk factor to further delineate risk of SCD in carriers of an HCM causing mutation.
Nonsustained VT was the only predictive risk factor (RF) for an appropriate ICD intervention in the PP (positive predictive value 22%, negative predictive value 96%).
Nonsustained ventricular tachycardia seems to be the most predictive RF for appropriate device discharges. 
However, LGE was strongly associated with surrogates of arrhythmia and remained a significant associate of subsequent SCD and/or ICD discharge after controlling for other variables. If replicated, LGE may be considered an important risk factor for sudden death in patients with HCM.
In conclusion, our cohort study results do not support LVOTO as an independent risk factor for SD in patients with hypertrophic cardiomyopathy.
The appearance of a "hump" at the ST segment during exercise testing appears to be a risk factor for SCD in patients with HCM. However, further studies are necessary to validate this finding in larger populations and to elucidate the mechanism of the appearance of the "hump."
The ICD is definitely indicated for secondary prevention of sudden death in patients with HCM who have survived a cardiac arrest with documented ventricular fibrillation, or experienced one or more episodes of sustained ventricular tachycardia.
A number of risk markers are used to assess the magnitude of risk, including family history of premature sudden death; extreme left ventricular (LV) hypertrophy (> 30 mm) in young patients; nonsustained ventricular tachycardia on Holter electrocardiographic recording; unexplained (not neurally mediated) syncope, particularly in young patients; and blood pressure decrease or inadequate increase during upright exercise.
Measured risk factors for sudden death included family history of sudden death, massive left ventricular hypertrophy, nonsustained ventricular tachycardia on Holter monitoring, and unexplained prior syncope.
The following risk factors were analyzed: 1) previous cardiac arrest or sustained ventricular tachycardia; 2) family history of sudden cardiac death; 3) high-risk genetic mutations; 4) syncope; 5) non-sustained ventricular tachycardia; 6) hypotensive response to exercise; and 7) marked left ventricular hypertrophy.
Family history of sudden death was associated with a positive predictive value of 25% for appropriate therapies, 40% for syncope and 50% for non-sustained ventricular tachycardia. 
In patients with an implantable cardioverter-defibrillator for primary prevention, non-sustained ventricular tachycardia was the risk factor with the highest predictive value. 
It is concluded that there is an association of the mutation Arg719Trp in the beta-myosin heavy chain with sudden cardiac death in a young child. 

Answer: The following risk factors for sudden cardiac death in patients with hypertrophic cardiomyopathy have been identified: 1) previous cardiac arrest; 2) sustained ventricular tachycardia; 3) family history of sudden cardiac death; 4) high-risk genetic mutations; 5) unexplained syncope; 6) non-sustained ventricular tachycardia; 7) hypotensive response to exercise; 8) marked left ventricular hypertrophy; 9) J-wave on ECG and 10) myocardial fibrosis using late gadolinium enhancement
Exact answer: myocardial fibrosis using late gadolinium enhancement
J-wave on ECG
Extreme left ventricular hypertrophy (>30mm)
Nonsustained ventricular tachycardia
Sustained ventricular tachycardia
previous cardiac arrest
family history of sudden cardiac death
unexplained syncope
hypotensive response to exercise
high-risk genetic mutations