Fat is something that we see as surgeons and we are almost oblivious to the fact that other physicians do not see it the same way. Interestingly, most imaging techniques are not good at viewing fat, classifying it or quantifying it. Fat when looked at, through conventional pathology, is usually a "negative" because fat or lipids get destroyed in the preparation processes (which include the use of formalin and paraffin wax). Special stains such as Oil Red O are used to look for fat but do not give much more information. Since a lot of our cellular and tissue structures are made of lipids, lipoproteins and lipid associated molecules, all of this data is lost. So, imagine our great surprise when we saw Lipids beautifully auto-fluorescing with Raman Spectroscopy! There have been wonderful papers on Near-Infrared. Autofluorescence in Atherosclerosis by Albadhdadi, et al (1). There is very little on actual lipid detection, quantification, delineation and distribution. We recently published a review on increased Epicardial Adipose Tissue (EAT) in atria of patients with atrial fibrillation (2). So, fat is definitely a tissue biomarker for AF. However, what is the threshold? How much? What kind? Where?
We often see fat on the epicardial surface of the heart and have made observations about how epicardial coronary arteries are more prone to atherosclerotic plaques. We often note that coronary arteries are often spared these obstructive lesions in their intra-myocardial course. So, many researchers have postulated that EAT might carry mediators of "badness", adipokines or messengers that predispose to plaque formation.
Increased lipid accumulation in the myocardium has been associated with myocardial disarray, fibrosis and apoptosis, leading to heart failure and atrial fibrillation (3,4).
Several studies have highlighted the use of EAT measurement in predicting outcomes after catheter ablation for paroxysmal or persistent atrial fibrillation (95,96). Peri-atrial EAT volume is greater in patients with atrial fibrillation and is associated with recurrence after catheter ablation (95–98). EAT volume is associated with atrial fibrillation persistence independent of other risk factors or BMI (99).
In any, fat in the heart is key and our very exciting findings relate to epicardial fat in the atrial appendages! Fat, even when NOT clearly visible to the educated surgical eye, can be detected with Vibrational Spectroscopy. This is extremely accurate and quick.
More about this in the next edition!
References:
1. Albaghdadi MS, Ikegami R, Kassab. MB, Gardecki JA, et al: Near-Infrared. Autofluorescence Associates with Ceroid and Is Generated by Oxidized Lipid-Induced Oxidative Stress. AthThromVascBiol.2021;41:e385-e398. doi: 10.1161/ATVBAHA.120.315612.
2.Krishnan, A.; Chilton, E.; Raman, J.; Saxena, P.; McFarlane, C.; Trollope, A.; Kinobe, R.; Chilton, L. Are Interactions between Epicardial Adipose Tissue, Cardiac Fibroblasts and Cardiac Myocytes Instrumental in Atrial Fibrosis and Atrial Fibrillation?. Cells 2021, 10(9), 2501; https://doi.org/10.3390/cells10092501.https://www.mdpi.com/2073-4409/10/9/2501.
3. Neeland, I. J., Poirier, P. & Després, J. P. Cardiovascular and metabolic heterogeneity of obesity: clinical challenges and implications for management. Circulation 137, 1391–1406 (2018).
4. Oikonomou, E. K. & Antoniades, C. The role of adipose tissue in cardiovascular health and disease. Nat. Rev. Cardiol. 16, 83–99 (2019).
5. Tsao, H. M. et al. Quantitative analysis of quantity and distribution of epicardial adipose tissue surrounding the left atrium in patients with atrial fibrillation and effect of recurrence after ablation. Am. J. Cardiol. 107, 1498–1503 (2011).
6. Chao, T.-F. et al. Epicardial adipose tissue thickness and ablation outcome of atrial fibrillation. PLoS ONE 8, e74926 (2013).
7. Kocyigit, D. et al. Periatrial epicardial adipose tissue thickness is an independent predictor of atrial fibrillation recurrence after cryoballoon-based pulmonary vein isolation. J. Cardiovasc. Comput. Tomogr. 9, 295–302 (2015).
8. Masuda, M. et al. Abundant epicardial adipose tissue surrounding the left atrium predicts early rather than late recurrence of atrial fibrillation after catheter ablation. J. Interv. Card. Electrophysiol. 44, 31–37 (2015).
9. Iacobellis, G., Zaki, M. C., Garcia, D. & Willens, H. J. Epicardial fat in atrial fibrillation and heart
Comments