High-Frequency Fluctuation Intensity as a Predictor of Post-Stenotic Dilatation in Swine

Objective: To identify the turbulent components of blood flow facilitating aortic lumen dilatation in a post-stenotic dilatation (PSD) porcine model. Methods: The porcine abdominal aorta (AA) was moderately coarctated to induce overt flow turbulence in the downstream region and to lead to dilatation in time periods between four and twelve weeks. We propose a new metric, fluctuation intensity (FI), to quantify turbulent fluctuations of pulsatile aortic flow measured within twenty minutes post-coarctation. Lumen perimeter ratio (LPR) of the distal-to-suprarenal AA was used to assess the degree of PSD. Using k-means clustering analysis, we first divided FI frequency spectrum into low- and high-frequency fluctuation intensity (LFFI and HFFI), and subsequently grouped animals with coarctation. Receiver operating characteristic (ROC) analysis was performed to evaluate the ability of the proposed metric to predict PSD. Results: The frequency band of the FI spectrum in facilitating aortic lumen dilatation was identified to be 40∼200 Hz. Using sham group as the reference, pigs receiving coarctation were clustered into two groups with (group A) and without (group B) increases in HFFI values. Coarctation significantly increased LPR values in group A, but not in group B. Moreover, group A exhibited a high probability density distribution on severe elastic fiber fragmentation. ROC analysis indicated HFFI to be capable of predicting PSD with excellent sensitivity and specificity. Conclusion: High-intensity, high-frequency components of blood flow fluctuations induced by moderate coarctation promote elastic lamella degradation and aortic lumen dilatation. Significance: HFFI application in flowmeter programs may provide a useful predictor of PSD.