Final answer:
Considering the age of the client and the physical exertion after a long period of inactivity, the pain could indicate a heart attack. Immediate medical attention is required for pain that could be associated with referred pain in the left shoulder and chest after strenuous activity.
Step-by-step explanation:
When a 63-year-old male client complains of pain in his left shoulder and chest after shoveling snow for an extended period, especially after not having done so in over 20 years, the best consideration may be that he is experiencing referred pain, which could indicate a more serious condition such as a heart attack. This type of pain is a common symptom and warrants immediate medical attention. It is important to consider the client's age and the physical exertion required to shovel snow, which has a low efficiency and can be very taxing on the body.