Final answer:
Patients with heart failure should report weight gain of 2 pounds in a week or persistent shortness of breath and chest pain immediately, as the latter may indicate serious complications such as pulmonary edema or cardiac events.
Step-by-step explanation:
A nurse instructing a client who has heart failure should emphasize the importance of reporting certain symptoms immediately to their healthcare provider. Among these symptoms, a weight gain of 2 pounds in a week can indicate worsening heart failure due to fluid retention.
However, the most critical symptoms that warrant immediate medical attention are persistent shortness of breath and chest pain, as they may signify acute decompensation of heart failure or other serious conditions such as pulmonary edema or a cardiac event.