Unroofed coronary sinus (UCS) is a rare birth defect in which the wall between the coronary sinus and the left atrium is missing, creating a left-to-right shunt. Blood takes a short-cut, so symptoms depend on how big the hole is and whether other heart anomalies are along for the ride. Shortness of breath leads the pack. Patients pant faster than peers, tire on stairs, or need extra pillows to sleep—classic signs of right-sided volume overload. Heart murmur is common. A soft whoosh or loud washing-machine sound is heard even without a stethoscope. Poor weight gain shows up early. Babies fall... Learn more