Best cardiac doctors near me What are symptoms of weak heart? Heart failure - Symptoms and causes - Mayo Clinic Symptoms Shortness of breath with activity or when lying down. Fatigue and weakness. Swelling in the legs, ankles and feet. Rapid or irregular heartbeat. Reduced ability to exercise. Wheezing. A cough that doesn't go away or a cough that brings up white or pink mucus with spots of blood. Swelling of the belly area.