Echocardiography and the small aortic root.

Two-dimensional echocardiography gives an estimate of the diameter of the annulus or sinotubular junction accurate to one millimeter. The diameter of the aortic annulus is related to body surface area or height, while the sinotubular junction is related additionally to age with a small effect from blood pressure and gender. A small aortic root may be defined theoretically as an annulus or sinotubular junction smaller than 1.0 cm/m2. If the aorta and replacement valve are considered as a unit, the effective area should be no less than 1.2 cm2/m2. The first gives an over-exclusive, the second an over-inclusive definition of prosthesis-patient mismatch. However, attention to hemodynamic or anatomic parameters alone may be biologically simplistic. We should probably incorporate an assessment of exercise ability, morbidity, mortality, LVH and measures of dynamic left ventricular diastolic and systolic function in the definition of patient-prosthesis mismatch.