Current practice and inconsistency in guidelines
diabetic, chronic kidney disease, PCI.In
COMPLICATION
Current clinical practice guidelines only marginally take into account the evidence provided thus far, probably reflecting the fear of M-ALA and its related mortality and the limitations of the studies evaluating the risk of metformin continuation in patients undergoing coronary angiography and PCI. In addition, guidelines are inconsistent in several aspects, such as timing to stop and restart metformin and to check creatinine and eGFR before and after the procedure [Our study provides evidence-based support to the current European guidelines on myocardial revascularization, which recommend checking renal function in patients assuming metformin and withhold metformin if renal function deteriorates (class of recommendation I, level of evidence C). The findings from our prospective study shows that—in case of limited risk for metformin accumulation—metformin continuation does not lead to a significant increase of lactate levels at 72 h as compared to preprocedural levels and that creatinine assessment before and at 72 h after coronary angiography and PCI ensures the safety of metformin continuation. Moreover, we observed that metformin continuation is associated with adequate glycemic control and with a low risk for CA-AKI. Based on our findings, metformin should not be discontinued prior to coronary angiography and PCI. Creatinine assessment at 72 h after the procedure assures to identify all patients with CA-AKI and subsequent risk of metformin accumulation.The present study should be interpreted considering some limitations. First, despite the prospective collection of procedural, pharmacologic, and clinical features, our results can only be considered hypothesis-generating, and a randomized controlled trial is required for a definite confirmation. However, a randomized trial aiming at evaluating the risk of M-ALA as compared to placebo is unfeasible, considering the excessively large sample size needed. A randomized trial powered to detect differences in a surrogate marker of M-ALA, such the increase of lactate, could be the best option to definitely quantify the risk of this complication among patients assuming metformin and scheduled for coronary angiography and PCI. Second, based on the study exclusion criteria, our findings cannot be applied to high-risk patients, such as those with severely reduced ejection fraction or severe chronic kidney disease. However, most patients presenting one or more exclusion criteria are not eligible for metformin therapy, rendering our findings generalizable to the large majority of patients treated with metformin undergoing coronary angiography and PCI.In conclusion, metformin continuation prior to coronary angiography and PCI is not associated with increased levels of lactate or decline in renal function in diabetic patients without high-risk features for its accumulation, such as severely reduced ejection fraction or severe chronic kidney disease, suggesting that metformin suspension before coronary angiography and PCI is not necessary.