Impact of renal dysfunction on arch replacement in a database study

Preoperative renal dysfunction is associated with adverse outcomes after cardiac surgery [1]. In addition, patients with end-stage renal disease (ESRD) on dialysis have been considered high-risk candidates for cardiac surgery [2]. On the other hand, with the progress of brain protection, aortic arch replacement has dramatically improved in safety over the last 30 years and has become established as a standard, safe surgical procedure. As with other cardiovascular surgical procedures, many reports indicate that the results of arch replacement differ depending on the degree of renal dysfunction, but most of the reports came from single institutions [3–5]. This issue features a report by Saito et al. [6], who analysed data regarding the relationship between renal dysfunction and the surgical outcomes of arch replacement from the Japanese cardiovascular surgery database, a national database similar to the Society of Thoracic Surgeons database, in which 99% of cardiovascular surgical procedures in Japan are registered. The enrolment is this study was limited to 4 years from 2014; a total of >5000 cases of elective aortic arch replacements were included.

In peripheral anastomosis of aortic arch replacement, it is standard to use hypothermic circulatory arrest (HCA). With the progress in brain protection, the minimum body temperature at the time of circulatory arrest has been raised in recent years. When using HCA, there is no direct perfusion of the renal arteries, as is done in thoraco-abdominal aortic replacement, and the temperature setting during HCA has a significant effect on postoperative renal function. The intraoperative renal protective effect of hypothermia is a well-known fact, but the relationship between temperature setting and postoperative renal function has not been investigated. In this respect, it was a significant limitation that the data regarding the lowest temperature and the length of the circulatory arrest in the lower body were not included.

The title of this paper indicates the result of aortic arch replacement in patients undergoing dialysis, but this paper discusses the effects of renal function on the outcome of aortic arch replacement, not just in relation to dialysis. It also describes the factors that cause acute renal failure after surgery. It is interesting that the rate of prolonged ventilation increases in proportion to the deterioration of renal function. The rate of deep sternal wound infection is also roughly proportional to the deterioration of renal function. The rate of postoperative stroke showed a similar tendency, and the rate of stroke was increased even with mild renal dysfunction. These tendencies were also shown in the risk-adjusted analyses. More interestingly, the number of surgically related deaths and strokes were not the highest in the group undergoing dialysis. It is worth noting that the poorest results were found in patients with impaired renal function before dialysis, even if the differences in the numbers of cases and the numbers of events in each group must be considered in the statistical analysis.

Regarding arteriosclerosis of coronary arteries, it is known that the calcification component increases as the chronic kidney disease stage progresses, which leads to the stabilization of plaque. However, in the process, mild to moderate calcification is known to destabilize plaque [7].

Although it may not be possible to use the same argument that one uses for arterial wall changes in the aorta, one may assume that changes in atherosclerotic lesions due to exacerbation of renal function affect the incidence of cerebral infarctions. A similar relationship between coronary plaque and renal function was reported as a subanalysis of the recently reported CT imaging study, the PARADIGM (Progression of AtheRosclerotic PlAque DetermIned by Computed TomoGraphic Angiography IMaging) trial [8]. According to the results of the study, plaques grew rapidly as renal function declined but not in patients with chronic renal failure. Griffin et al. [9] even reported that patients with ESRD who were stable were not at increased risk of major postoperative complications after cardiac surgery compared to those without ESRD. It goes without saying that sufficient caution is required for patients on dialysis because multiple organs might be damaged, but these data may suggest that we have to pay the most attention to patients with severe chronic kidney disease who do not require dialysis at surgery.

In conclusion, this paper revealed several interesting facts regarding the effect of deteriorated renal function on the results of aortic arch replacement. I would like to commend the authors from the bottom of my heart, and I look forward to further research and analysis for our patients.

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