Characteristics and Longer-Term Outcomes of Contemporary Patients <18 Years of Age With Hypertrophic Cardiomyopathy

We describe characteristics and outcomes of contemporary pediatric hypertrophic cardiomyopathy (PHC) patients. We studied 398 consecutive pediatric HC patients (<18 years, median 14 years, 65% boys) seen at our center between 2002 and 2018. Baseline clinical and pediatric echocardiographic data was collected. Left ventricular outflow tract gradient (LVOTG), LV fractional shortening and Z-score for left ventricular (LV) wall thickness were calculated. Sudden cardiac death (SCD), appropriate internal defibrillator discharge (ICD), myectomy, and orthotopic heart transplant (OHT) were composite primary endpoint. A total of 133 (33%) had symptoms (71 [18%] dyspnea, 77 [19%] angina, and 19 [5%] syncope), 109 (27%) were on beta-blockers; 179 (45%) had family history of HC. A total of 146 (37%) underwent genetic testing (of which 91 (62%) were HC-gene positive). Basal septal LV thickness, septal LV z-score and fractional shortening were 1.2 ± 0.6 cm, 4.8 ± 5.6, and 42% ± 8, whereas 23% had extreme LV hypertrophy (z-score > 6) and 8% had LVOTG >30 mm Hg (range 0 to 139 mm Hg). At a median of 5.9 years (interquartile range 2.4, 9), there were 23 (6%) ICD's placed, and 47 (12%) primary composite events (9 [2%] deaths, 3 [1%] appropriate ICD discharge, 29 [7%] myectomy, and 8 [2%] OHT). There were no in hospital deaths following myectomy/OHT. Presence of symptoms (Hazard ratio or HR 2.45), ventricular tachycardia (HR 1.52), and higher basal septal LV z-score (HR 1.10) were independently associated with primary composite outcomes. LV septal z-score >4 was independently associated with events on spline analysis. Rate of SCD/appropriate ICD discharge was 0.5%/year. In conclusion, contemporary PHC patients seen at an experienced center have excellent outcomes with presence of symptoms and higher LV septal thickness associated with primary composite events.