NPPB and cardiomyopathy: Repeated-measures analysis after the initiation of MEKi showed significant improvement of the laboratory heart failure biomarker NT-proBNP and individual echocardiographic parameters of cardiomyopathy (peak outflow tract gradient, maximal end-diastolic wall thickness z-score, left ventricular end-diastolic diameter, and left ventricular mass indexed to body surface area) over time (Supplemental Table 1, Supplemental Figure 3, line plots; example echocardiography in Figure 3).