The Boot-shaped Heart Sign

The boot-shaped heart sign or coeur en sabot in a patient with TOF.
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TOF has 4 components:
(1) obstruction of the right ventricular outflow tract, which may be below the pulmonic valve in the infundibulum of the right ventricle;
(2) ventricular septal defect (VSD);
(3) overriding of the aorta above the VSD
(4) right ventricular hypertrophy.
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The toe of the boot is formed by the upward pointing cardiac apex, which makes an acute angle with the diaphragm.The upturned cardiac apex is ascribed to right ventricular hypertrophy.The narrower upper part of the boot results from a small or absent main pulmonary artery partly caused by a narrow infundibulum and hypoplastic main pulmonary artery.The sign is accentuated by a large lung volume, a small thymus, and the lordotic projection.
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