After several hours, the patient's condition worsened: the left side of his chest became dull to percussion; his temperature and pulse rate rose; his breathing became shallow; and he complained of considerable pain.

After tying the severed intercostal artery to control bleeding and removing the blood from the pleural cavity, Dalton observed a transverse wound of the pericardium about 2 inches (5 cm) in length.

With a sharply curved needle and catgut, he closed the wound by continuous suture, overcoming great difficulty caused by the heart pulsations.

[7][8] On July 10, 1893 African American surgeon Daniel Hale Williams became the first on record to replicate Dalton's success, repairing the torn pericardium of knife wound patient James Cornish.

[10][11] The first successful surgery of the heart, performed without any complications, was by Dr. Ludwig Rehn of Frankfurt, Germany, who repaired a stab wound to the right ventricle on September 7, 1896.