The "straight back" refers to a lack of the normal kyphosis seen in the thoracic spine. This can be demonstrated in a lateral chest X-ray by:
(1) Draw a vertical line from the middle of the anterior surface of the T4 vertebra to the middle of the anterior surface of the T12 vertebra.
(2) Draw a horizontal line from the middle of the anterior surface of the T8 vertebra to this line.
(3) The distance along this horizontal line will be less than 1.2 cm in a patient with a straight back.
A patient with a straight back tends to have a narrow chest from anterior to posterior (sagittal axis). The heart may be compressed between the sternum and vertebrae.
Clinical features:
(1) variable chest pain
(2) variable palpitations
(3) often a family history with an autosomal dominant inheritance
(4) systolic heart murmur
(5) physiologic splitting of the second heart sound
Changes seen in the ECG may include:
(1) incomplete right bundle branch block
(2) vertical QRS axis
The murmur may be a benign flow murmur or it may be due to an underlying valve disorder. The most common valve disorders are:
(1) mitral valve prolapse
(2) bicuspid aortic valve
