A Research Study to Look at Long-term Treatment With a Medicine Called NNC6019-0001 for People Who Have Heart Failure Due to Transthyretin Amyloidosis

Inclusion Criteria: * Completed study intervention in NN6019-4940 and attended the last study visit (week 64; visit 16), and no later than 12 weeks after visit 16. * Expected to be on stable doses of cardiovascular medical therapy 6 weeks prior to the enrolment visit. Exclusion Criteria: * A prior solid organ transplant. * Presence or history of malignant neoplasm (other than basal or squamous cell skin cancer, in-situ carcinomas of the cervix, or in-situ/high grade prostatic intraepithelial neoplasia (PIN) or low-grade prostate cancer) within 5 years before screening. * Current treatment with calcium channel blockers with conduction system effects (e.g., verapamil, diltiazem). The use of dihydropyridine calcium channel blockers is allowed. The use of digoxin will only be allowed if required for management of atrial fibrillation with rapid ventricular response. * Body weight greater than (\>) 120 kilograms (kg) (264.6 pounds \[lb\]) at screening.