Usefulness and Limitations of Assessment of Internal Shortening Velocity by Ultrasound in Man

Abstract

Measurement of circumferential shortening velocity offers an attractive method for assessing left ventricular performance during ejection since both the extent of shortening and the time factor ( i e , the rate of shortening) are considered. Initially, a complex angiographic approach utilizing frame-byframe analysis of the left ventricular cavity silhouette was employed.' It was postulated that at the time of maximum wall stress during ejection, the rate of series elastic extension should-be zero, and therefore the instantaneous shortening velocity at peak wall tension should be equal to contractile element velocity ( Vce ) . Since intraventricular pressure, chamber radius and wall thickness can be measured throughout systole, instantaneous velocity for any given wall stress can be derived. In each instance, velocity was by dividing the corresponding instantaneous circumference so that chambers of different size could be compared. This method proved fruitful and it was possible to separate patients with normal from those with impaired left ventricular performance. Mirsky andhis colleagues2 have provided a mathematical rationale for the normalized velocitv concept. The behavior of heart muscle can be described using exponential stress-strain characteristics