Table 7.

Major and possible risk factors for SCD in patients with HCM. Adapted from Elliot PM et al. [25].

Major risk factors
1. Family history of sudden death (<50 years).
2. Unexplained and recurrent syncope.
3. Ventricular wall thickness ≥30 mm.
4. Documented nonsustained ventricular tachycardia (NSVT) (>three beats with heart rate >120 bpm)*
5. Systolic blood pressure drop ≥20 mmHg on exertion*
Number of major risk factors	Estimated 6-year survival from SCD (%)
•0	95
•1	93
•≥2	82

Possible risk factors: LVOT gradient ≥30 mmHg; high-risk genetic mutation; myocardial fibrosis (>15% LV mass) on CMR, LV apical aneurysm.

Low risk (SCD incidence 0.2–0.4% per year): Absence of established risk factors; absent or mild symptoms; left atrium ≤45 mm; ventricular wall thickness ≤20 mm; LVOT gradient <50 mmHg.

^*Only when associated with other possible risk factors.