Playfair showed the heart of a child which had lived nine months in which one ventricle was absent.

In King's College Hospital in London there is a heart of a boy of thirteen in which the cavities consist of a single ventricle and a single auricle.
Duplication of the heart, notwithstanding the number of cases reported, has been admitted with the greatest reserve by Geoffroy-Saint-Hilaire and by a number of authors.

Among the celebrated anatomists who describe duplex heart are Littre, Meckel, Collomb, Panum, Behr, Paullini, Rhodins, Winslow, and Zacutus Lusitanus.
The Ephemerides cites an instance of triple heart, and Johnston has seen a triple heart in a goose.
The phenomenon of "blue-disease," or congenital cyanosis, is due to the patency of the foremen ovale, which, instead of closing at birth, persists sometimes to adult life.
Perhaps the most unique collection of congenital malformations of the heart from persons who have reached the age of puberty was to be seen in London in 1895.

In this collection there was an adult heart in which the foremen ovale remained open until the age of thirty-seven; there were but two pulmonary valves; there was another heart showing a large patent foramen ovale from a man of forty-six; and there was a septum ventriculorum of an adult heart from a woman of sixty-three, who died of carcinoma of the breast, in which the foremen ovale was still open and would admit the fore-finger.

This woman had shown no symptoms of the malformation.