Systolic thickening increases from subepicardium to subendocardium

Study objective - The aim was to determine the relation between systolic function and depth below the epicardial surface, using pulsed Doppler crystals.Design - Systolic excursion in mm was measured at multiple depths below the epicardial surface. Measurements were made during control conditions.Subjects - Thirty four anaesthetised mongrel dogs were studied.Measurements and main results - A total of 333 measurements of systolic excursion were made during control conditions at 1 to 3 crystal sites per dog. Two models were constructed; the model which assumed a quadratic relation between depth (d) and systolic excursion (EX) (EX = 0.498 + 0.176d + 0.006d²) fit the data better than did a model which assumed a linear relation (EX = -0.0716 + 0.254d).Conclusions - These data support the prediction from geometric models that systolic excursion increases in a non-linear fashion from subepicardium to subendocardium.