Find anatomical drawings of the human heart by referencing the seminal medical illustration book, Gray’s "Anatomy of the Human Body." There are many other medical texts and websites available that feature anatomical illustrations, such as the Mayo Clinic and Nucleus Medical Catalog.
Henry Gray's "Anatomy of the Human Body" is considered a classic in medical illustration and has been used for many years to teach medical students anatomy. An online version of the work is available on Bartleby.com, but many libraries carry it as well. It contains a chapter on the human heart, under section V, Angiology, Part 4, The Thoracic Cavity. This chapter contains many hand-drawn illustrations in a variety of different angles and views.
You can also view medical illustrations at a number of online sites. For example, the Mayo Clinic website, MayoClinic.org, has many illustrations of anatomical organs, including a cross-section of the heart. The Nucleus Medical Catalog, NucleusCatalog.com, has several copyrighted anatomical illustrations of the heart that you can request to use for a fee.