Treating Heart Dysfunction Related to Cancer Therapy With Sacubitril/Valsartan

Inclusion Criteria:

* Age \</= 39 years old at time of cancer diagnosis
* Clinical records adequate to determine diagnosis and treatment regimen
* Previous anthracycline chemotherapy
* Global longitudinal strain \<18% and/or
* Left ventricular ejection fraction (LVEF) below the institutional lower limit of normal but \>/=40% on echocardiogram or cardiac magnetic resonance imaging (MRI)
* No symptoms of heart failure (shortness of breath, fatigue, swelling). Ordinary physical activity does not cause undue fatigue, palpitation, dyspnea (shortness of breath).

Exclusion Criteria:

* -Age \<18 years
* Inability to obtain consent from patient or legally authorized representative
* Active acute or chronic psychiatric illness that in the opinion of the investigator may prevent compliance with study instructions
* Limited English or Spanish proficiency that in the opinion of the investigator may prevent understanding the content of the informed consent form or safely completing the study procedures
* Participation in another concurrent intervention study within 30 days or treatment with an investigational drug within 5 half-lives prior to randomization
* Greater than mild mitral or aortic valve regurgitation/stenosis known pre-cancer therapy
* Severe kidney disease (glomerular filtration rate (GFR) \<30 milliliters (mL)/minute (min)/1.73 meters squared (m2))
* Chronic hyperkalemia (\>5millimoles per liter (mmol/L))
* Evidence of Coronavirus (COVID-19) within the last 60 days or recent (21 days) exposure to close personal contact with COVID-19.
* Greater than moderate tricuspid or pulmonary valve regurgitation/stenosis known pre-cancer therapy
* Hemodynamically significant congenital heart disease in the opinion of the investigator (not including patent foramen ovale (PFO)/small atrial septal defect (ASD) or small ventricular septal defect (VSD))
* Greater than moderate pericardial effusion
* Constrictive cardiomyopathy diagnosed pre-cancer therapy
* Family history of genetic cardiomyopathy
* Evidence of infiltrative cardiomyopathy
* Symptomatic heart disease based on New York Heart Association (NYHA) classification
* Allergy to valsartan or sacubitril
* Inability to complete cardiac magnetic resonance (CMR) or 6-minute walk test
* Inability to measure non-invasive blood pressure and heart rate in the ambulatory/home setting
* Pregnant/lactating
* History of severe hypersensitivity reactions to gadolinium-based contrast agents (will perform limited cardiac imaging without contrast)
* Concomitant use of other angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs), aliskiren, non-steroidal anti-inflammatories (NSAIDs) or lithium or the inability to stop these medications for the study