Table 2

Major clinical markers recommended for current HCM risk stratification*†21

Family history of SD†3 6 Sudden death judged definitively or likely due to HCM, generally considered occurring in ≥1 first degree, or other close relatives, <50 years of age.
Extreme LV hypertrophy†9 42 Wall thickness ≥30 mm in any LV segment by echocardiography and/or CMR; consideration for this morphological marker is also given to borderline values of 28 mm or 29 mm in individual patients, at the discretion of the treating cardiologist.‡
Unexplained recent syncope†43 One or more recent and otherwise unexplained events involving loss of consciousness, judged by history unlikely to be neurally mediated (vasovagal) syncope.§
Non-sustained ventricular tachycardia (NVST)¶3 6 Three or more brief episodes of consecutive ventricular beats and/or ≥1 prolonged burst of ≥10 beats, at a rate of >130/min, usually over 24–48 hours continuous ambulatory ECG monitoring.
LGE (fibrosis)39 Diffuse and extensive LGE distribution representing fibrosis, either quantified or estimated by visual inspection as comprising about ≥15% of LV mass, either alone or in association with other risk markers, and a likely source of ventricular tachyarrhythmias.**
End-stage HCM38 Systolic dysfunction with ejection fraction <50% by echocardiography or CMR, usually in symptomatic patients without outflow obstruction who may be considered potential heart transplant candidates.
LV apical aneurysm37 Of variable size and characterised by akinetic-dyskinetic thinned wall. Usually identified by CMR (or contrast-enhanced echocardiography), with contiguous ‘border-zone’ myocardial scarring, often associated with apical hypertrophy and malignant ventricular tachyarrhythmias.
  • *Two other variables, abnormal blood pressure response to exercise and LV outflow obstruction (gradient ≥50 mm Hg at rest), can be used to selectively support ICD decisions in some patients with ≥1 other risk markers, but alone are not usually considered sufficient evidence to support ICD recommendations.

  • †Most important in risk stratification of children and adolescents.

  • ‡Relationship between LV thickness and SD risk is linear, although mild LVH does not necessarily exclude SD risk; pattern of LVH does not predict HCM outcome, including development of heart failure.

  • §Episodes of near-syncope can also be considered, if judged likely to be arrhythmic in origin.

  • ¶Prognostic power of NSVT as a risk factor is probably greater when associated with other markers, particularly substantial LGE, which can be responsible for ventricular tachyarrhythmias: it is also intuitive that long NSVT runs (≥ 10 beats) convey greater risk than brief runs.6 21 Caution is appropriate when prognostic judgements rely solely on NSVT as an isolated risk factor because of its variability and also the difficulty in standardising for length of the monitoring period. Prolonged, frequent periods of palpitations can represent important ventricular tachyarrhythmias, particularly when associated with impaired consciousness but require documentation by ECG monitoring.

  • **In addition to the arbitrary cut-off of ≥15% of LV mass (exclusive of right ventricular insertion areas), a linear relationship is demonstrated between SD risk and LGE extent, suggesting that LGE of 10%–15% can be clinically relevant in some patients; absent or focal LGE (<5% of LV mass) is generally regarded as most consistent with low risk.

  • HCM, hypertrophic cardiomyopathy; ICD, implanted cardioverter-defibrillator; LGE, late gadolinium enhancement; LVH, left ventricular hypertrophy; SD, sudden death.