Comprehensive analysis of effective reflection distance and its association with wave reflection strength under diverse hemodynamic conditions in anesthetized dogs

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Pressure wave reflection is associated with cardiovascular risk. The conceptual distance to a theoretical major reflection site, termed effective reflection distance (ERD), has been associated with aging and augmentation index (AIx) clinically. However, it remains unclear whether and how ERD varies and associates with AIx when the hemodynamic condition is acutely perturbed in a patient. The objective of this study was to address this issue in rigorously controlled animal experiments. In 13 anesthetized dogs, we measured arterial pressure, aortic flow and femoral arterial flow, while altering the hemodynamic condition over wide ranges by administering zatebradine (bradycardic agent), nitroprusside (vasodilator), noradrenaline (vasoconstrictor), dobutamine (inotrope), and dextran (volume-expander). Using the measured data, we determined ERD based on an arterial model comprising a tube with a complex frequency-dependent load (ERDTL), which has been considered a physiologically valid model. We also determined ERD based on wave separation (ERDWSA) and pressure-based analyses (ERDAW). ERDTL was shortened significantly in response to nitroprusside or dobutamine infusion, and was significantly and negatively associated with AIx in multiple regression analysis using pooled data. ERDWSA or ERDAW did not necessarily correlate with ERDTL in terms of responses to drug administration or association with AIx. In conclusion, under diverse hemodynamic conditions, ERDTL changes sensitively and shows physiologically reasonable association with AIx. This result substantiates the importance of paying close attention to medications during clinical analysis of wave reflection. Caution is required when using ERDWSA or ERDAW as an alternative to ERDTL.