Dissecting aortic aneurysm associated with a midsystolic click.

A midsystolic click occurred in a patient with a type 1 dissecting aneurysm. The mechanism of production of the systolic click may be related to rapid deceleration of blood against the intimal flap. Combined phonocardiography and echocardiography (using a new second right intercostal space approach) proved to be helpful in differentiating this sound from an aortic and pulmonary ejection click. In addition, other causes of midsystolic clicks, such as mitral and tricuspid valve prolapse, were excluded.