Final answer:
Janeway's lesions on the palms are the most important assessment finding to communicate to the health care provider in a patient with infective endocarditis, as they indicate systemic involvement and the possibility of embolic phenomena.
Step-by-step explanation:
The most important assessment finding in a patient who is admitted with infective endocarditis (IE) to communicate to the health care provider is Janeway's lesions on the palms. Janeway's lesions are painless, erythematous or haemorrhagic macular or nodular lesions on the palms or soles and are considered pathognomonic for infective endocarditis. These manifestations are suggestive of emboli to the skin and are important for diagnosis, indicating a more systemic involvement of the infection including possible embolic phenomena.
While flank pain, muscle aching, and fever are also symptoms to be concerned about, the presence of Janeway's lesions is a more specific sign of IE. Fever is an expected finding in IE but it is non-specific. It's also significant to note that the temperature of 100.7° F (38.1° C) should still be monitored as it indicates ongoing infection.