According to a paper published last week in JAMA Cardiology, doctors at Tufts University’s HCM Center have been able to identify 95% of their patients at high risk of sudden cardiac death (SCD) from HCM. Tufts applied an updated and modified version of the risk factors enumerated in the American College of Cardiology/American Heart Association Guidelines promulgated in 2011.
Who Was Included in this Study:
The study looked retrospectively at 2094 patients seen at Tufts over a 17 year period.
- Of 527 patients who received ICDs for primary prevention (i.e. as a preventative measure, having never suffered a cardiac arrest) 82 or 15.6% had an appropriate device discharge.
- In the 1567 patients who did not receive ICDs, there were 5 HCM related sudden deaths. This group included 2 individuals who declined an ICD following recommendation of an implant.
Risk Factors Used To Evaluate Need for ICD:
The seven factors used evaluate the patients’ need for ICDs were:
- Family History of SCD in 1 or more close relatives age 50 or less
- Left ventricular hypertrophy of ≈30 mm or greater
- Unexplained syncope (fainting)
- Late gadolinium enhancement (LGE) identified fibrosis with diffuse and extensive distribution of ≥ 15% of left ventricular mass
- 3 or more incidents of non-sustained ventricular tachycardia of 3 or more consecutive beats. Longer episodes of 10 beats or more had greater significance, especially when combined with another risk factor, especially LGE.
- End-stage disease with ejection fraction of < 50%
- Left ventricular apical aneurysm
The following additional criteria were sometimes used to supplement the above risk factors:
- Abnormal blood pressure response to exercise
- Left ventricular outflow tract gradient of ≥ 50 mmHg
- Moderate degree of LGE
In this study, genetic mutations were not used as a risk factor. And, because age ≥ 60 is associated with low risk of SCD, decisions to implant ICDs in this group of patients were made on a case-by-case basis only when other risk factors were significant enough to justify.
ESC Risk Assessment Tool Found to Be Inferior
Interestingly, this study found that if the European Society of Cardiology (ESC) risk calculator had been used, it would have identified only 34% of the individuals who experienced a ventricular arrhythmia terminated by an ICD or a SCD.
Invited Commentary to Article by Dr. Steve Ommen of the Mayo Clinic HCM Center
In a commentary to the study by Dr. Steve Ommen, Director of Mayo Clinic’s Hypertrophic Cardiomyopathy Center, Ommen pointed out that individual risk assessment involves more than just a straight application of risk factors to test results. He emphasized that the ultimate choice whether or not to get an ICD lies with the patient, and that doctors must consider the patient’s unique level of risk tolerance. Shared decision making between physician and patient is paramount.
Previous HCMBeat Blog Posts Re: Risk Assessment for SCD
Here are some past HCMBeat discussions of risk stratification which give some background and provide some context for this study.