Although invasive coronary angiography (ICA) still represents the gold standard in the assessment of CABG patency, it is associated with potential complications ranging 1–5%[3, 4], such as bleeding, dissection, pseudoaneurysm, cardiac arrhythmia and stoke, and it is technically more difficult than MDCT in the depiction of correct anatomy of grafts, particularly in complex revascularization patients, which would undoubtedly limit its application in the routine follow-up of graft patency. MDCT could be a suitable candidate due to its noninvasive and less expensive characteristics, and it requires lower technical difficulty and shorter operating time than ICA. Moreover, MDCT could provide more additional information, such as the diagnosis of early and late complications including sternal infection and pericardial or pleural effusion, the evaluation of aortic and valvular lesions, delineation of the anatomical course of bypass conduits and their topographic relationship to vital mediastinal structures; these findings could assist in the preoperative planning of redo cardiac surgery and thus reduce the incidence of graft damage.
There are still only a few studies that evaluate the patency of grafts with MDCT after CABG, although it can bring excellent diagnostic accuracy. A systemic review of Chan and colleagues involving 1975 patients and 5364 grafts demonstrated that MDCT had the aggregated sensitivity and specificity of 98% (95% CI: 97–99%) and 98% (95% CI: 96–98%) in the assessment of bypass graft occlusion and stenosis. Similarly, a study of Barbero and colleagues concluded that the diagnostic sensitivity and specificity for combined assessment of occlusion and stenosis were both over 98%. Although MDCT could not replace ICA in conduit patency assessment after CABG at present, MDCT can obtain clear graft images and plays a crucial role in the evaluation of grafts, especially for asymptomatic patients. However, with future improvement in CT technologies, MDCT can provide better cardiac visualization in shorter time and might supersede ICA for graft assessment in the near future.
Despite of the recommendation of current guidelines to replace the SVG with the RA in patients with high-degree coronary artery stenosis, few surgeons were willing to choose the RA as their preferred materials; in addition to a LIMA to the left anterior descending artery (LAD), the majority of patients received the SVG. A report from STS ACSD showed that RA grafts were used in only 6.5% of all primary isolated CABG patients in the United States between 2004 to 2015, with a gradual decrease. There are several reasons for its limited utilization such as few studies reporting a mean follow-up of over 10 years and possible harm to the forearm circulation. Therefore, we describe the preliminary short-term follow-up outcomes of 41 patients who underwent CABG with the RA in order to promote the use of the RA in CABG.
Multiple studies indicated that the RA had better early-, mid- and long-term patency than the SVG, and could provide better late-term survival for CABG patients[9–13]. Recent guidelines also recommend the RA as one of the second-best arterial conduits for CABG surgery. The RA has the advantage of easy obtaining and excellent length (20-22cm), which could reach nearly all the coronary territories and result in few site-related complications. In this study, no mortality events occurred without postoperative myocardial infarction or repeat revascularization events. During the follow-up, the RA had the slightly better patency rate (84.4%) than that of the RIMA (80.0%) and SVG (81.1%).
The CCB played an important role in RA patency and long-term survival. A report of Gaudino et al. showed that CABG with the RA and postoperative CCB utilization could result in better midterm results, higher RA graft patency and lower incidence of major adverse cardiac events compared with the group without CCBs. Moreover, the Society of Thoracic Surgeons Clinical Practice Guidelines on Arterial Conduits recommended to use pharmacologic agents to reduce acute intraoperative and perioperative spasm for RA grafts. In this study, patients were prescribed with CCBs for 1 year after surgery. Meanwhile, surgeons should avoid touching and clamping the RA to prevent spasm during RA harvesting.
The RA bypassed to the LCAS might provide better patency than the RA bypassed to the RCAS. And the 2018 ESC/EACTS Guidelines on myocardial revascularization also indicated that the RA for non-LAD targets could provide better patency than the SVG, particularly for the LCAS. In this study, the patency rate of RA-LCAS was 86.2%, while the patency of RA-RCAS was only 81.3%; and this characteristic of arterial grafts has been confirmed by previous literature. One explanation might be the competitive flow and different diameters of coronary arteries. Arterial grafts could autoregulate blood flow according to different metabolic needs[16–19], and the main RCA has relatively large diameter; therefore, the same stenosis degree could result in a larger residual lumen in the RCAS, which could provide a larger blood supply and decrease the blood flow demand from the RA. These events could cause RA graft constriction and, over time, increase the risk of RA graft atrophy and occlusion. The 2011 ACCF/AHA CABG Guideline also indicated different recommendation criteria for the application of the RA in the LCAS and RCAS; it might be reasonable to use RA grafts when grafting arteries of the LCAS with > 70% stenosis and arteries of the RCAS with > 90% stenosis. Therefore, we think that the application indication of arterial conduits in the RCAS should be stricter compared with the LCAS; stenosis more than 90% of the RCAS may lead to better patency.
The forearm brachial artery and ulnar artery have good blood flow reserve capacity; after RA removal, the total blood flow of the forearm has no significant difference as compared with the non-RA removal group, and the RA removal has no significant effect on the patient’s forearm mobility and survival[12, 21–23]. In a report of Royse et al. on a 22-year follow-up after the RA harvesting, there was no difference in the total blood flow in the forearm between the RA-harvested side and the control side, and the increase of dynamic blood flow during exercise had no significant difference between the two group. Furthermore, a 20-year follow-up study of Gaudino et al. reported the increase of the ulnar artery diameter in the operated arm without hand or forearm symptoms. In this study, 2 patients developed hand paresthesia after operation, which might result from surgical trauma or ischemia neuropathy, and the hand paresthesia symptom of 1 case disappeared during follow-up.
A limitation of this study is the relatively limited sample size and short follow-up time, compared with other larger studies. Another limitation is the lack of the assessment of CABG patency with the reference standard of ICA, and there is no comparison between MDCT and ICA. However, considering the excellent accuracy of MDCT in diagnosing patency of CABG grafts, we consider it unnecessary to correlate with ICA. Moreover, it should be stressed that the main goal of this study is to evaluate the quality of RA, not to determine the diagnostic accuracy of MDCT.