4 | DISCUSSION
To the best of our acknowledgement, this is the first study that compares different definitions of CR in the same patient, abolishing all confounding variables of multi-person analysis. In this series, a complete functional revascularization (all viable myocardial territories are reperfused) was the only definition with increased long-term survival after coronary surgery. According to recent studies, CR based on the functional definition is the preferred strategy for PCI [1]. However, the role of functional revascularization for CABG is not so obvious [12-14]. For example, the substudy of the STITCH TRIAL failed to prove that a functional revascularization was associated with a greater likelihood of survival in ischemic left ventricular dysfunction, when adjusted for patients’ baseline variables [12]. Toth et al [13] did not find a significant difference of adverse cardiovascular events at 3 years between patients with fractional flow reserve-guided CABG and angiography-guided CABG.
In literature, there are many different definitions of CR [11]. Probably the most used definition is the anatomical conditional revascularization, where all epicardial vessels with a diameter exceeding ≥1.5 mm and a luminal reduction of ≥50% in at least one angiographic view are revascularized. Recent studies supported by this definition have reported conflicting results. An example is two different post hoc analysis of the SYNTAX trial data, with one study concluding that incomplete surgical revascularization did not impact outcomes, while the other study found relation between incomplete revascularization and adverse outcomes [4,5]. In this study, an incomplete anatomical conditional revascularization was not associated with an increased follow-up mortality.
Complete anatomical unconditional revascularization (all stenotic vessels are revascularized, irrespective of size and territory supplied) is very difficult to achieve as seen in our study with only 13% of the patients. Most common reasons are calcified/diffusely diseased small vessels, difficult exposure, hemodynamic instability, porcelain aorta and limited conduits. Furthermore, this definition has not beeing associated with increased survival in literature [8]. Our research reached the same conclusion. From a survival perspective, the added effort to bypass all branch vessels may not be necessary.
This series validated that numerical revascularization - number of stenotic vessels equals to the number of distal anastomoses - is not relevant in clinical practice.
Our study also verified that age and cardiac dysfunction are independent predictors of late mortality, as seen in earlier studies [3].
There are limited data regarding the relation between CR and perioperative outcomes. Lee et al found a relation between incomplete revascularization and MACCE in patients with left ventricular dysfunction [10]. In this research, the definition of complete revascularization did not have an impact on MACCE, possibly indicating the impact of complete revascularization appears to be maximal in the long term.
The need to repeat revascularization was not associated with any definition of CR. A low number of events can explain this result.
This study has multiple limitations. It is based on the retrospective analysis of a population determined by having or not a myocardial perfusion scintigraphy prior to CABG. For that reason, it is a small sample size with low number of events. Surgery was carried by different surgeons and the revascularization was dependent on their clinical assessment. It was not possible to evaluate the reasons for incomplete revascularization. The constrained access to other institutions’ records limited us to accurately identify morbidity during follow-up.