Postoperative assessment of left ventricular function
The evaluation of left ventricular function in man by invasive means presently is accomplished by two major techniques. First, the recording of left ventricular pressure and second, the performance of left ventriculography. Although some of the parameters derived from these techniques are based upon current concepts of myocardial muscle mechanics and others assess characteristics of left ventricular performance, all methods have both theoretical and practical limitations. In general, it can be said that resting measurements of contractile indexes such as V max, Max dp/dt at developed pressure, Vcf and mean systolic ejection rate have proven to be an insensitive way to assess dysfunction except when the impairment is advanced. Measurement of these indexes during exercise may prove more sensitive and is presently being evaluated. The ejection fraction and regional wall motion studies have demonstrated improvement of ventricular performance after bypass surgery when ejection fraction is depressed and regional wall motion abnormalities represent hypokinetic as compared to akinetic areas.
Our largest experience and emphasis since the beginning of bypass surgery have been the assessment of left ventricular performance under various types of stress, such as increased afterload, volume loading, angiographic stress, handgrip, atrial pacing, and exercise. I believe that the most sensitive and rewarding relate to the stress of exercise and particularly the use of ventricular performance curves. Starling left ventricular function curves define the relationship between the left ventricular stroke work index on the vertical axis and left ventricular enddiastolic pressure on the horizontal axis. A family of functional curves . . .