CORRELATION OF VENTRICULAR AREA, PERIMETER, AND CONOTRUNCAL DIAMETER WITH VENTRICULAR MASS AND FUNCTION IN THE CHICK-EMBRYO FROM STAGES 12 TO 24

Ventricular form and function are interrelated during cardiovascular development. The study of muscle mechanics requires the real-time measurement of length, area, or volume. Because volume measures are not currently possible in the embryonic heart, we tested the hypothesis that end-diastolic (ED) and end-systolic (ES) ventricular perimeter, area, and conotruncal diameter correlate with ventricular mass and function in the stage 12 to stage 24 white Leghorn chick embryo. Video images of the contracting heart were recorded at 60 Hz on 1/2 ' videotape and studied with a custom image-analysis workstation. ED and ES video fields were selected by maximum and minimum ventricular area and were planimetered for epicardial ventricular perimeter, area, and conotruncal diameter. Data are reported as (mean ± SEM, n ≥8) and were tested by analysis of variance and regression analysis. Heart rate calculated from cycle length increased from 78 ± 6 beats/min at stage 12 to 162 ± 5 beats/min at stage 24. ED and ES area increased geometrically versus stage (y = 0.53 - 0.08χ + 0.004χ2, r = 0.96, p < 0.001; and y = 0.60 - 0.09χ + 0.004χ2, r = 0.98, p < 0.001, respectively). ED and ES perimeter and conotruncal diameter increased linearly versus stage (r = 0.95, p < 0.001; r = 0.96, p < 0.001; and r = 0.93, p < 0.001; r = 0.93, p < 0.001, respectively). Shortening fraction for each measurement increased from stage 12 to 16 or 18 then decreased. ED and ES perimeter, area, and conotruncal diameter also correlated with stroke volume, ventricular wet weight, and embryo and extraembryonic vascular bed wet weight (r > 0.90 and p < 0.001 for each measurement). Thus, epicardial ventricular measurements accurately reflect ventricular mass and function in the embryonic heart.