In simple words: The patient has a sudden worsening of heart failure symptoms, on top of long-term heart failure where the heart's ability to pump blood effectively is reduced.

Acute on chronic systolic (congestive) heart failure. This code signifies that the patient is experiencing an acute episode of heart failure, superimposed on a pre-existing condition of chronic systolic heart failure.

Example 1: A patient with a history of chronic systolic heart failure presents to the emergency department with shortness of breath, edema, and orthopnea. These symptoms represent an acute exacerbation of their underlying chronic condition. Therefore, I50.23 is the appropriate code., A patient with known chronic systolic heart failure develops sudden and severe shortness of breath following a respiratory infection. The infection has triggered an acute episode of heart failure on top of their chronic condition, justifying the use of I50.23., A patient with stable chronic systolic heart failure experiences a rapid decline in heart function after discontinuing their medication. This acute decompensation, occurring in the context of chronic heart failure, warrants the use of I50.23.

Documentation should clearly specify "acute on chronic systolic (congestive) heart failure."Supporting documentation should include symptoms, signs, and diagnostic test results, such as echocardiograms, BNP levels, and chest X-rays. Any precipitating factors, such as infections or medication non-compliance, should also be documented.