Final answer:
The most appropriate referral for a client diagnosed with a myocardial infarction is cardiac rehabilitation.
Step-by-step explanation:
The most appropriate referral for a client diagnosed with a myocardial infarction, commonly known as a heart attack, would be cardiac rehabilitation. Cardiac rehabilitation programs are specifically designed to help individuals recover from a heart attack and improve their heart health. They typically include medically supervised exercises, counseling, and education on heart-healthy lifestyle changes.