Comprehensive characterization of the postoperative pericardial inflammatory response: Potential implications for clinical outcomes

The inflammatory mediators that are present in the pericardial space after surgery.

Figure 1. The inflammatory mediators that are present in the pericardial space after surgery. MMP, Matrix metalloproteinase; TIMP, tissue inhibitor of metalloproteinase; TGFβ, transforming growth factor beta; IL, interleukin.

Figure 2. The immune cell profile that is present in the pericardial space changes postsurgery. A, Representative t-distributed stochastic neighbor embedding plots showing the immune cell profile present in native PF (left), at 4 (middle left), 24 (middle right), and 48 hours' post-CPB (right). The figure was prepared by using Adobe Illustrator 2022. B, Overview of the immune cells present in the pericardial space as total numbers per milliliter in native PF and at the postoperative time points. C, Proportional quantification of the immune cells that are present in native and postsurgical PF, presented as percentage of CD45+ cells. Comparisons for neutrophils, CD163hi and lo Mφ, cDC2, Inf DC, B cells, T-cells, CD16+ and CD16– NKs are included. Each comparison represents n = 36 for native PF, n = 43 for 4, 24, and 48 hours' post-CPB. Box and whisker plots indicate median with minimum ± maximum. The lower and upper borders of the box represent the lower and upper quartiles (25th percentile and 75th percentile). The middle horizontal line represents the median. The lower and upper whiskers represent the minimum and maximum values of nonoutliers. For statistical analysis 2-way analysis of…

Figure 3. Cytokines, MMPs, TIMPs, and TGFβ are present in the pericardial space post-surgery and their relative concentrations change over time. A, Heatmap representation of the cytokines that are present in the pericardial space at 4, 24, and 48 hours' post-CPB in pg/mL. The cytokine with the highest expressed level is at the top, and the lowest is at the bottom. Each comparison includes n = 27 for 4, 24, and 48 hours' post-CPB. B, Heatmap representation of the MMPs that are present in the pericardial space at 4, 24, and 48 hours' post-CPB in pg/mL. The highest MMP is at the top, the lowest at the bottom. Each comparison includes n = 27 for 4, 24, and 48 hours' post-CPB, except MMP-12 with n = 20 for each time point. C, Heatmap representation of the TIMPs that are present in the pericardial cavity at 4, 24, and 48 hours post-CPB in pg/mL. The highest TIMP is at the top, the lowest at the bottom. D, Heatmap representation of the TGFβs that are present in the pericardial cavity at 4, 24, and 48 hours post-CPB in pg/mL. The highest TGFβ is at the top, the lowest at the bottom. For statistical analysis 2-way variance analysis with the Tukey post hoc test was performed to determine difference…

Figure 4. Assessment of postoperative pericardial MMP/TIMP ratios. Quantitative comparison of postsurgical pericardial MMP/TIMP ratios at 4, 24, and 48 hours' post-CPB with respect to each time point. Analysis and comparison of MMPtot to TIMPtot ratio when considering the time point after surgery (left), MMP-2/TIMPtot (second left), MMP-3/TIMPtot (middle), MMP-8/TIMPtot (second right), and MMP-9/TIMPtot (right). Time-point comparisons contain n = 27 for 4, 24, and 48 hours' post-CPB. For statistical analysis 2-way variance analysis with the Tukey post hoc test was performed to determine difference between time points. Box and whisker plots indicate median with minimum ± maximum. The lower and upper borders of the box represent the lower and upper quartiles (25th percentile and 75th percentile). The middle horizontal line represents the median. The lower and upper whiskers represent the minimum and maximum values of nonoutliers. ∗∗P ≤ .01. ∗∗∗P ≤ .001. ∗∗∗∗P ≤ .0001. MMP, Matrix metalloproteinase; TIMP, tissue inhibitor of metalloproteinase; CPB, cardiopulmonary bypass; tot, total.

Figure 5. Comparison between sAVR and RAMT-AVR output volume of the fluid that is present in the pericardial space postoperatively. A, Schematic diagram showing the 2 surgical approaches: sAVR is at the top (in red) and RAMT-AVR is at the bottom (in blue). Postoperative pericardial fluid was collected at 4, 24, and 48 hours after the patient was weaned off CPB. B, The total postsurgical pericardial drain output in mL is shown at 4, 24, and 48 hours' post-CPB. Comparison includes n = 8 for each group at each time-point. Statistical analysis was performed at each time point using an unpaired Student t-test. Lines show mean ± standard error of mean. ∗∗P ≤ .01. ∗∗∗P ≤ .001. sAVR, Conventional full median sternotomy surgical aortic valve replacement; RAMT-AVR, right anterior mini-thoracotomy aortic valve replacement; CPB, cardiopulmonary bypass.

Figure 6. sAVR and RAMT-AVR elicit differences in the post-operative pericardial immune cell profile. A, Comparison of CD45+ cell number per milliliter of postsurgical pericardial fluid in sAVR versus RAMT-AVR at 4, 24, and 48 hours' post-CPB. For statistical analysis an unpaired Student t-test was performed to determine differences between sAVR and RAMT-AVR at each time point. Box and whisker plots indicate median with minimum ± maximum. The lower and upper borders of the box represent the lower and upper quartiles (25th percentile and 75th percentile). The middle horizontal line represents the median. The lower and upper whiskers represent the minimum and maximum values of nonoutliers. B, Proportional quantifications of immune cell populations at 4, 24, and 48 hours' post-CPB comparing sAVR versus RAMT-AVR, including neutrophils (top row left), macrophages with CD163hi Mφ (top row middle) and CD163lo Mφ (top row right), dendritic cells with cDC2 (middle row left) and Inf DC (middle row middle), B cells (middle row right), T cells (bottom row left), and NK cells with CD16+ NKs (bottom row middle) and CD16– NKs (bottom row right). Each comparison includes n = 8 for sAVR and n = 8 for…

Figure 7. Forty-three patients undergoing cardiac surgery were enrolled in the study. After removing each patient's native pericardial fluid, a drain was placed in the pericardial space to allow for collecting postoperative pericardial fluid. The collected fluid was analyzed for immune cells and inflammatory mediators, including cytokines, matrix metalloproteinases, tissue inhibitors of metalloproteinases, and growth factors. Furthermore, to determine how pericardial handling affects the local postoperative inflammatory response, postoperative pericardial fluid was compared between patients undergoing conventional aortic valve replacement and right anterior mini thoracotomy aortic valve replacement. The local postoperative inflammatory profile may have important clinical implications, where certain factors can contribute to postoperative atrial fibrillation, postsurgical pericardial adhesion formation, and postpericardiotomy syndrome. PF, Pericardial fluid; CPB, cardiopulmonary bypass; IL, Interleukin; MMP, matrix metalloproteinase; TIMP, tissue inhibitor of metalloproteinase; TGFβ, transforming growth factor beta.

Figure E1. Flowchart depicting the patient selection process as per Strengthening the Reporting of Observational Studies in Epidemiology recommendation. VADs, Ventricular assist devices; CPB, cardiopulmonary bypass.

Figure E2. Comparison between sAVR and RAMT-AVR and the concentrations of cytokines, MMPs, and TIMPs. A, Comparison of the concentration of 3 cytokines in sAVR versus RAMT-AVR groups at 4, 24, and 48 hours' post-CPB. Cytokines being presented include IL-6 (left), IL-8 (middle), and IL-10 (right) where concentrations are shown in pg/mL. Each panel represents n = 8 for sAVR and n = 8 for RAMT-AVR. For statistical analysis, an unpaired Student t-test was performed to determine differences between sAVR and RAMT-AVR at each time point. Lines represent mean ± standard error. ∗∗P ≤ .01. B, Comparison of MMP levels in sAVR versus RAMT-AVR at 4, 24, and 48 hours post-CPB. MMP-1 (left), MMP-10 (middle), and MMP-12 (right) are shown where concentrations are shown in pg/mL. MMP-1 (left) and MMP-10 (middle) represent n = 8 for sAVR and n = 8 for RAMT-AVR, while MMP-12 (right) shows n = 5 for sAVR and n = 4 for RAMT. For statistical analysis, an unpaired Student t-test was performed to determine differences between sAVR and RAMT-AVR at each time point. Lines represent mean ± standard error. ∗P ≤ .05. C, Comparison of TIMP-1 (left), TIMP-2 (middle), and TIMP-4 (right) concentration levels in postsurgical…

Figure E3. Assessment of postoperative pericardial MMP/TIMP ratios in patients undergoing sAVR versus RAMT-AVR. Quantitative comparison of postsurgical pericardial MMP/TIMP ratios at 4-, 24-, and 48-hours post-CPB with respect to surgical approach. Analysis and comparison of MMPtot to TIMPtot ratio when considering sAVR versus RAMT-AVR (left), MMP-2/TIMPtot (second left), MMP-3/TIMPtot (middle), MMP-8/TIMPtot (second right), and MMP-9/TIMPtot (right). Comparisons represent n = 8 for sAVR and n = 8 for RAMT-AVR. For statistical analysis unpaired Student t-test was performed to determine differences between sAVR and RAMT-AVR at each time-point. Lines present mean ± standard error. ∗P ≤ .05. MMP, Matrix metalloproteinase; TIMP, tissue inhibitor of metalloproteinase; sAVR, conventional full median sternotomy surgical aortic valve replacement; RAMT-AVR, right anterior mini thoracotomy aortic valve replacement; CPB, cardiopulmonary bypass; tot, total.