NPPB and hypertrophic cardiomyopathy: HCM: hypertrophic cardiomyopathy; HOCM: hypertrophic obstructive cardiomyopathy; SRT: septal reduction therapy; VO2: oxygen consumption; NYHA: New York Heart Association; LVOT: left ventricular outflow tract; KCCQ: Kansas City Cardiomyopathy Questionnaire; NT-proBNP: N-terminal pro-B-type natriuretic peptide; LVEF: left ventricular ejection fraction.