Left Ventricular Dysfunction Following Repair of Ventricular Septal Defects in Infants.

Left ventricular systolic dysfunction (LVSD) is frequently observed following repair of ventricular septal defects (VSD), although little is known about its incidence, time course, or risk factors. Among infants undergoing VSD repair, for postoperative LVSD, we sought to determine (1) incidence, (2) predictors, and (3) time to resolution. We queried our institution's surgical database for infants who underwent repair of isolated VSDs from November 2001 through January 2019. The primary outcome was postoperative LVSD, which was defined as a shortening fraction (SF) of <26% by M-mode. Postoperative echocardiograms were reviewed, and measurements were made using standard methods. Receiver operating characteristic analysis was generated to determine the preoperative left ventricular internal dimension (LVIDd) z-score most predictive of LVSD. Multivariable analysis was conducted to determine associations with LVSD; covariates in the model were weight percentile, genetic syndrome, preoperative diuretic, VSD type, and preoperative LVIDd z-score. Of the 164 patients who met inclusion criteria, 62 (38%) had postoperative LVSD. Fifty-eight (94%) of patients had resolution of LVSD within 9 months of surgery. Preoperative LVIDd z-score of >3.1 was associated with both an increased incidence of postoperative LVSD and prolonged time to resolution. Multivariable logistic regression analysis showed only preoperative LVIDd z-score was independently associated with postoperative LVSD. LVSD following VSD closure is common, but nearly all cases resolve by 9 months postoperatively. Elevated LVIDd prior to surgery is associated with postoperative LVSD. These data suggest VSD closure should be considered prior to the development of significant left ventricular dilation.

Flux or speed? Examining speckle contrast imaging of vascular flows.

Speckle contrast imaging enables rapid mapping of relative blood flow distributions using camera detection of back-scattered laser light. However, speckle derived flow measures deviate from direct measurements of erythrocyte speeds by 47 ± 15% (n = 13 mice) in vessels of various calibers. Alternatively, deviations with estimates of volumetric flux are on average 91 ± 43%. We highlight and attempt to alleviate this discrepancy by accounting for the effects of multiple dynamic scattering with speckle imaging of microfluidic channels of varying sizes and then with red blood cell (RBC) tracking correlated speckle imaging of vascular flows in the cerebral cortex. By revisiting the governing dynamic light scattering models, we test the ability to predict the degree of multiple dynamic scattering across vessels in order to correct for the observed discrepancies between relative RBC speeds and multi-exposure speckle imaging estimates of inverse correlation times. The analysis reveals that traditional speckle contrast imagery of vascular flows is neither a measure of volumetric flux nor particle speed, but rather the product of speed and vessel diameter. The corrected speckle estimates of the relative RBC speeds have an average 10 ± 3% deviation in vivo with those obtained from RBC tracking.