Conway J, Min S, Villa C, Weintraub RG, Nakano S, Godown J, Tatangelo M, Armstrong K, Richmond M, Kaufman B, Lal AK, Balaji S, Power A, Baez Hernandez N, Gardin L, Kantor PF, Parent JJ, Aziz PF, Jefferies JL, Dragulescu A, Jeewa A, Benson L, Russell MW, Whitehill R, Rossano J, Howard T, Mital S.
Take Home Points:
- Children with HCM are at increased risk for lower transplant-free survival and SCD. Exercise testing is commonly performed but rarely utilized for risk assessment.
- Of exercise test-related abnormalities, an ischemic response was independently associated with adverse cardiovascular outcomes, including worse transplant free survival and SCD.
- Abnormal BP response predicted worse transplant-free survival but not SCD in this study cohort.
Commentary by Dr. Jeremy Moore (Los Angeles) Congenital and Pediatric Cardiac EP section editor:
Pediatric patients with HCM are at risk for sudden cardiac death and mortality related to progressive heart failure. Although exercise stress testing has been used in adults for risk stratification, there are few data in children with HCM. This study from the international PRiMaCY cohort evaluated the results of exercise stress testing in a subgroup of 630 children 8 years of age. Of these, 175 (28%) exercise tests were classified as abnormal (due to either blunted BP response, ischemia or complex ventricular ectopy) and was more frequently observed among those with prior septal myectomy, higher mean LV septal z score, LA diameter z score, LVEF and greater LVOTO (p=0.001). Patients with an abnormal exercise stress test were more likely to receive an ICD and were more likely to receive ICD shocks; although they were not at greater risk of SCD, they experienced worse transplant free survival (HR 2.97, p=0.007) during follow up.
When examining the specific type of exercise test abnormality and all-cause mortality, those with abnormal BP response were at greatest risk (rate 4.6 per 100 pt-years) followed by ischemia (2.9 per 100 pt-years). Those with complex ventricular arrhythmia did not experience any events. Compared with those with normal exercise testing, there was a significantly higher hazard of all-cause mortality or transplant in those with an abnormal BP response (HR, 3.2, p=0.010) and in those with an ischemic response (HR, 4.86, p=0.003) both of which persisted in multivariate analysis that included echocardiographic indices. For SCD, the greatest risk was observed for those with ischemia (rate 5.9 per 100 pt-years) followed by abnormal BP response (1.7 per 100 pt-years); again no events were observed among those with complex ventricular ectopy. On multivariable analysis, only exercise-induced ischemia remained independently associated with SCD (HR, 3.3, p=0.014). When compared by exercise response category, there was a greater risk for appropriate ICD shocks among those with exercise-induced ischemia (HR, 5.8, p=0.054) and in those with ectopy (HR, 5.7, p=0.056) compared with those with a normal exercise test result, but these differences were not statistically significant
The authors conclude that exercise testing is valuable for pediatric patients with HCM and that an ischemic response predicts both worse transplant-free survival and SCD risk.
