HCM Risk-SCD Calculator

Input HCM Parameters:

Clinical History

Predicting Sudden Cardiac Death in Hypertrophic Cardiomyopathy (HCM)

Hypertrophic Cardiomyopathy (HCM) is a genetic cardiomyopathy characterized by left ventricular hypertrophy. It is the most prevalent cardiomyopathy worldwide, affecting 1 in 500 individuals in most societies. HCM is also the most common cause of sudden cardiac death (SCD) in young individuals and during exercise. The risk of ventricular arrhythmias correlates with the degree of hypertrophy, the extent of ventricular fibrosis, LVOT obstruction, age, and left ventricular function. The HCM Risk-SCD score aims to identify individuals with a high risk of SCD and determine whether an implantable cardioverter-defibrillator (ICD) is warranted. The HCM Risk-SCD calculator is validated to estimate the 5-year risk of SCD in patients with HCM.

What is the HCM Risk Calculator?

The HCM Risk Calculator is based on the HCM Risk-SCD formula, a validated risk prediction model developed I relatively large patient cohorts. It incorporates key clinical and echocardiographic parameters to calculate an individual’s risk of SCD over the next 5 years. The calculator is widely used in clinical practice and is endorsed by major cardiology guidelines, including those from the European Society of Cardiology (ESC), American College of Cardiology (ACC) and American Heart Association (AHA).

The formula takes into account the following variables:

  1. Maximum Left Ventricular Wall Thickness (MaxLVWT): Hypertrophy is a hallmark of HCM and is associated with increased arrhythmic risk.
  2. Left Atrial Diameter (LA): Enlargement of the left atrium is a marker of elevated left ventricular filling pressures and is linked to adverse outcomes.
  3. Left Ventricular Outflow Tract Gradient (LVOTG): LVOT obstruction is a risk factor for heart failure and arrhythmias.
  4. Family History of Sudden Cardiac Death (FHSCD): A history of SCD in close relatives suggests a genetic predisposition to arrhythmias.
  5. Non-Sustained Ventricular Tachycardia (NSVT): Episodes of VT are a strong predictor of SCD.
  6. Unexplained Syncope: Syncope without a clear cause may indicate underlying arrhythmias.
  7. Age: Younger patients are generally at higher risk of SCD due to the progressive nature of HCM.

By combining these factors, the calculator generates a 5-year SCD risk percentage, which helps clinicians stratify patients into low, intermediate, or high-risk categories.

A significant shortcoming of the HCM Risk-SCD Score is the absence of magnetic resonance imaging parameters (extent of myocardial fibrosis).

Risk stratification

The calculator helps identify patients at high risk of SCD who may benefit from preventive interventions, such as ICD implantation. For example:

  • A 5-year SCD risk ≥ 6% is considered high risk, and ICD implantation is typically recommended.
  • A risk between 4% and 6% is considered intermediate, and additional clinical judgment is required.
  • A risk < 4% is considered low risk, and routine follow-up is usually sufficient.

Shared decision-making

The calculator provides a quantitative estimate of SCD risk, which facilitates informed discussions between clinicians and patients. This is particularly important when considering ICD implantation, as the procedure carries both benefits (life-saving therapy) and risks (e.g., device-related complications).

Monitoring disease progression

By periodically recalculating the SCD risk, clinicians can monitor changes in a patient’s condition over time. For instance, an increase in left atrial size or the development of NSVT may warrant closer surveillance or a reassessment of treatment strategies.

References

O’Mahony C, Jichi F, Pavlou M, et al. A novel clinical risk prediction model for sudden cardiac death in hypertrophic cardiomyopathy (Hcm risk-scd). European Heart Journal. 2014;35(30):2010-2020.

Vriesendorp PA, Schinkel AFL, Liebregts M, et al. Validation of the 2014 European Society of Cardiology guidelines risk prediction model for the primary prevention of sudden cardiac death in hypertrophic cardiomyopathy. Circ Arrhythm Electrophysiol. 2015;8(4):829-835.O’Mahony C, Jichi F, Ommen SR, et al. International external validation study of the 2014 european society of cardiology guidelines on sudden cardiac death prevention in hypertrophic cardiomyopathy(Evidence-hcm). Circulation. 2018;137(10):1015-1023.

Zeppenfeld K, Tfelt-Hansen J, de Riva M, et al. 2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Eur Heart J. 2022;43(40):3997-4126.Authors/Task Force members, Elliott PM, Anastasakis A, et al. 2014 esc guidelines on diagnosis and management of hypertrophic cardiomyopathy: the task force for the diagnosis and management of hypertrophic cardiomyopathy of the european society of cardiology(Esc). Eur Heart J. 2014;35(39):2733-2779.Monda E, Limongelli G. Integrated sudden cardiac death risk prediction model for patients with hypertrophic cardiomyopathy. Circulation. 2023;147(4):281-283.

Updated on 2025-02-03