Efficacy, Safety, and Pharmacokinetics of Vericiguat in Pediatric Participants With Heart Failure Due to Left Ventricular Systolic Dysfunction (MK-1242-036)

Inclusion Criteria: * Has symptomatic chronic heart failure (HF) resulting from systemic left ventricular (LV) systolic dysfunction. * Has biventricular physiology with a morphologic systemic left ventricle. * Is currently receiving stable medical therapy for HF. * Has left ventricular ejection fraction (LVEF) \<45% assessed within 3 months before randomization. * Is of any sex/gender, from \>28 days to \<18 years of age inclusive. Must weigh ≥3 kg to participate. * Female is eligible to participate if not pregnant or breastfeeding, and at least one of the following: is not a participant of childbearing potential (POCBP); or is a POCBP who uses a highly effective contraceptive method; has a negative highly sensitive pregnancy test; abstains from breastfeeding during the study intervention period and for at least 30 days after study intervention; and their medical history; their menstrual history, and recent sexual activity has been reviewed. * Extension Period: Was randomized, received at least 1 dose of study intervention (vericiguat or placebo), did not permanently discontinue study intervention, and completed the Week 52 visit and safety follow-up period of the Base Period Exclusion Criteria: * Is clinically unstable-with at least one of the following: has symptomatic hypotension or is hypotensive for age, recent use of intravenous (IV) inotrope and/or IV vasodilator, or recent IV diuretic. * Has a known allergy or sensitivity to vericiguat, any of its constituents, or …