11 November 2008
In order to study the influence of sudden left ventricular pressure rise on the calibrated apexcardiogram, 181 acute aortic occlusions were performed during systole in 7 dog experiments. For each beat preceding (CO) an occlusion and each occlusion (OC), peak systolic amplitude of left ventricular pressure (CO: 118.5 ± 17.8 mm Hg; OC: 205.8 ± 38.7 mm Hg) and apexcardiogram (CO: 48.8 ± 16.7 mm Hg; OC: 63.0 ± 25.8 mm Hg) were measured. Pressure gradients, ratios and surface areas of all tracings were digitally calculated. The cross-correlation function between pressure and apexcardiogram was also calculated in order to determine time lags. Significant correlations were found: between surface ratios and pressure gradient of pressure (r = 0.80, p < 0.001) and of apexcardiogram (r = 0.79, p < 0.001); between surface ratios of pressure and surface of apexcardiogram (r = 0.52, p < 0.001). The data suggest that during isovolumic systole, the time integral of the left ventricular pressure and its change during the ejection phase define to a large extent the general shape and size of the apexcardiogram.