Combined hemodynamic-ultrasonic method for studying left ventricular wall stress: comparison with angiography

Calculation of left ventricular wall stress in man has traditionally required angiographic and left ventricular pressure measurement, making study of interventions difficult. We have developed a combined hemodynamic-ultrasonic technique for measuring left ventricular meridional wass stress (sigma m) throughout the cardiac cycle. Simultaneous measurements of left ventricular pressure, ultrasonically determined wall thickness (h[echo]), and minor axis (D[echol]) were made during cardiac catheterization in nine subjects, three with chronic left ventricular pressure overload, four with left ventricular volume overload and two with normal left ventricular function. Within 30 minutes, left ventricular cineangiography was performed in each subject and angiographic wall thickness (h[angio]) and minor axis (D[angio]) were measured. Comparison of values for each subject throughout the cardiac cycle (average 18 data points/cycle) yielded close correlation: For D(echo) versus D(angio), r values ranged from 0.82 to 0.98 whereas for h(echo) versus h(angio), r values ranged from 0.56 to 0.98 for the nine subjects. Meridional wall stress was calculated after the method of Sandler and Dodge as PRi2/h(2Ri + h), where Ri equals the inner wall radius, calculated as D/2 for both ultrasonic and angiographic methods. Agreement between ultrasonic and angiographic methods was excellent in each subject, with close superimposition of the stress-time plots constructed by the different techniques. In summary, a new method for measurement of left ventricular wall stress has been developed and validated by comparison with an angiographic reference standard. This method has potential advantages, including the ability to study meridional wall stress continuously and to assess its response to serial interventions.