Participants with known congestive heart failure (CHF); if known, patients with left ventricular ejection fraction (LVEF) =< 40% are excluded Left ventricular ejection fraction (LVEF) >= 55% Pediatric patients: normal left ventricular function with ejection fraction > 55% or shortening fraction >= 27% Left ventricular ejection fraction (LVEF) >= institutional lower limit of normal Left ventricular ejection fraction >= 45% Systolic cardiac function will be assessed at screening if clinically indicated by history and physical; only patients with left ventricular ejection fraction (LVEF) >= 50% will be eligible for enrollment Left ventricular ejection fraction (LVEF) >= 50% (measured within 28 days of study entry) Patients must have left ventricular ejection fraction (LVEF) > 45% or within institutional normal limits Left ventricular ejection fraction (LVEF) < 50%, regardless of whether there are symptoms of heart failure Left ventricular ejection fraction (LVEF) >= 50% If cardiac function assessment is clinically indicated or performed: participants will be ineligible if left ventricular ejection fraction (LVEF) is less than normal per institutional guidelines, or < 55%, if the threshold for normal is not otherwise specified by institutional guidelines