The relationship between vascular expansion of the aorta and pulmonary artery and the genesis of the impedance cardiogram using the technique of sonomicrometry

Primary objective: This prospective animal study aims to evaluate the contribution of the pulmonary artery (PA) and aorta on the morphology of the impedance cardiogram using sonomicrometry.Methods: Impedance electrodes were placed around the thorax, aorta and in the oesophagus of five dogs. Sonomicrometry crystals were mounted on the PA and aorta for tracking vascular distension while a Doppler flow probe measured aortic blood flow.Results: No significant differences (p > 0.05) were recorded between the onset of aortic expansion, aortic blood flow and the start of the impedance dZ/dt signal. Significant differences (p > 0.001) were recorded between the onset of PA expansion and the dZ/dt signal. PA expansion began 41.6 ± 6.0 ms, 60.7 ± 7.2 ms and 42.2 ± 4.9 ms respectively, before surface, aortic and oesophageal impedance recordings.Conclusion: The genesis of the impedance cardiogram is attributed to volumetric expansion of the aorta.