CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 5, September/October 2022 246 AFRICA of atherosclerosis. Moreover, compared with all other arterial and venous conduits, it shows increased production of antiinflammatory and vaso-active molecules, particularly nitric oxide.8 However, the ITA is more vulnerable to traction injury, which is associated with intimal fracture, creating an intimal flap that may restrict flow or initiate a subintimal dissection. This lesion is specific to the ITA and may decrease its long-term patency.3,9 MEC is a basic tool for precise, fast and bloodless preparation of both pedicular and skeletonised ITA grafts in cardiac surgery. The fundamental performance of electrocautery dissection is created by continuous thermal energy from an electric current to the conductive tissue, which leads to vapourisation and ionisation of the water content in the tissue adjacent to the electrode and ultimately ablates the soft tissue. Several factors might be blamed for ITA endothelial injury. The leading cause is direct touching of the cautery tip with the ITA or the metallic clip, which causes a gross diathermal injury. Secondly, we believe improper use of the MEC causes an invisibleburndepth injury totheendothelium.The transformation of electrical energy into heat occurs in the following Joules law, which is the core principle of all electrosurgery devices: energy = 2 × (current/cross-sectional area) × resistance × time. Low cautery requires a longer time to produce dissectible energy, during which time it creates an unpredictably high temperature, which causes ITA injury.10 The time needed for preparation of the ITA with low cautery was significantly longer in our study, which confirms this. Finally, tissue around the ITA consists of endothoracic fascia, fatty tissue and intercostal muscle, which have different impedances to electrical current. Fatty tissue requires higher threshold energy to be dissected in comparison with muscle due to its higher resistance to electric current. Instead of blunt dissection, cauterising for a more extended time may cause burn depth of the ITA pedicle. Moreover, at a higher power of cautery (40W), it was possible to divide the ITA branches by direct contact with a 3–5-mm distance from the ITA main trunk without clips. This technique can provide optimal haemostasis. Placing haemostatic clips onto the stumps of the ITA branches after the ITA is completely dissected also eliminates the risk of contact injury. Our study result was inconsistent with other studies withMEC, in that both indicated that there was endothelial damage.3,11,12 The question of whether endothelial injury regresses later or causes stenosis or occlusion is not known. In our study, the absence of stenosis or occlusion may be explained by the fact that the endothelial injury detected by histopathological investigation was too trivial to trigger the endothelial coagulation cascade, or the injury could spontaneously have lessened over time. But further investigation and long-term follow ups are necessary to confirm this theory. This study has some limitations. It included only a limited number of patients. The histopathological observation at the distal end of the ITA may not be consistent with the integrity of the entire length of ITA. Therefore, it was not possible to prove it in vivo. Finally, since there is no globally recognised scoring or grading system of ITA endothelial injury, the severity of ITA endothelial injury could not be graded in detail. Further investigation and long-term patency are required before widespread use of this technique. Conclusion Low cautery power (20W) may not be safe for harvesting pedicular ITA. Morphological integrity of the ITA endothelium was better preserved with 40W output, and it also enabled the operator to harvest faster. Endothelial injury caused by the MEC below 40W did not have any adverse effect on ITA free flow and one-year patency. References 1. Waheed A, Klosterman E, Lee J, Mishra A, Narasimha V, Tuma F, et al. Assessing the long-term patency and clinical outcomes of venous and arterial grafts used in coronary artery bypass grafting: a meta-analysis. Cureus 2019; 11: 9. 2. Ali E, Saso S, Ashrafian H, Athanasiou T. Does a skeletonized or pedicled left internal thoracic artery give the best graft patency? Interact Cardiovasc Thorac Surg 2010; 10: 97–104. 3. Lehtola A, Verkkala K, Järvinen A. Is electrocautery safe for internal mammary artery (IMA) mobilization? A study using scanning electron microscopy (SEM). Thorac Cardiovasc Surg 1989; 37: 55–57. 4. Lamm, P, Juchem, J, Weyrich, P, Schutz, A, Reichart, B. The harmonic scalpel (optimizing the quality of mammary artery grafts). Ann Thorac Surg 2000; 69: 1833–1835. 5. Bilgen F, Yapici MF, Serbetçioğlu A, Tarhan IA, Coruh T, Ozler A. Effect of normothermic papaverine to relieve intraoperative spasm of the internal thoracic artery. Ann Thorac Surg 1996; 62: 769–771. 6. Windecker S, Kolh P, Alfonso F, Collet JF, Cremer J, Falk V, et al. ESC/ EACTS Guidelines on myocardial revascularization. Eur Heart J 2014; 35: 2541–2619. 7. Galbut DL, Kurlansky PA, Traad EA, Dorman MJ, Zucker M, Ebra G. Bilateral internal thoracic artery grafting improves long-term survival Fig. 4. Angiographic view of ITA one year after operation. A: ITA harvested with 20W cautery, very few haemoclips were used. B: ITA harvested with 40W cautery, multiple haemoclips were used. A B
RkJQdWJsaXNoZXIy NDIzNzc=