A Study of LY3971297 in Participants With Heart Failure

Inclusion Criteria: * Are diagnosed with chronic heart failure with New York Heart Association Class II-III (Heart Failure) HF symptomatology at screening and on guideline-directed HF therapy for at least 6 months prior to screening. * Have not changed optimal guideline-directed HF therapy, either medication or medication dose, in the last 4 weeks prior to screening and during screening period, and do not plan to change HF therapy for the next 90 days. * Must be on a stable dose of vasodilator therapy for at least 4 weeks prior to screening, with no dose adjustments planned during the study. * Have an estimated glomerular filtration rate of greater than or equal to (≥) 30 milliliter per minute per 1.73 square meters (mL/Minute/1.73m²) at screening. * Are between 30 days and within 12 months from recent heart failure hospitalization to screening. * Have systolic blood pressure (SBP) greater than (\>) 110 millimeters of mercury (mmHg) at screening and at enrollment. * Have a body mass index within the range of 18.5 to 40 kilograms per square meter (kg/m²) (inclusive). * Are individuals assigned male or female at birth, who are not of childbearing potential. * Have venous access sufficient to allow blood sampling. * Applicable to heart failure with preserved ejection fraction (HFpEF) participants only * Have left ventricular ejection fraction (LVEF) \>45 percent (%). * Left atrial volume index \>34 milliliters per square meter (mL/m²) in participants in sinus rhythm, or \>…