To the best of our knowledge, this is the first nationwide cohort study to compare the cardiovascular and limb outcomes of SGLT2i and DPP4i administered to patients with T2D who had undergone PAD revascularization. The main findings of this study are that compared with DPP4i, SGLT2i were associated with comparable risks of IS, AMI, and HFH but were not associated with a higher risk of repeated revascularization or lower limb amputation. However, SGLT2i were associated with lower risks of cardiac death and composite renal outcomes compared with DPP4i. These observations persisted among several major subgroups.
Although SGLT2i and DPP4i are both commonly prescribed as second-line agents for glycemic control in patients with T2D (with metformin as the first-line agent), our study revealed differences in preferences in the prescription of these agents in our cohort. Specifically, we observed that the SGLT2i group exhibited higher prevalence of ischemic heart disease, hypertension, dyslipidemia, and history of percutaneous coronary intervention but a lower prevalence of CKD. A likely explanation is that SGLT2i were prescribed to patients at a high risk of cardiovascular events because these agents are beneficial for reducing the risks of cardiovascular events; they were not prescribed to patients with advanced kidney disease because they engender glycuresis through the kidneys [10]. We observed that SGLT2is reduced the risk of AMI, cardiac death, and composite renal outcomes in patients without concomitant metformin therapy but not in those with metformin therapy in subgroup analysis. Although metformin had been reported to have cardioprotective effects, it may increase the risk of lactate acidosis in patients with CKD and the risk of acute kidney injury during revascularization with contrast medium administration that contribute to the worse outcomes in our study population [19].
Patients with T2D and concomitant PAD have a higher risk of mortality and amputation than do those with T2D or PAD alone [11, 20]. PAD revascularization was suggested for patients who exhibited claudication or critical limb ischemia despite optimal medical therapy [2]. Notably, patients with T2D who have received PAD revascularization are generally considered to have advanced-stage PAD, which is associated with poor cardiovascular and limb outcomes [21–23]. Previous studies have revealed that intensive glycemic control may improve outcomes in this high-risk group [24–26], but few studies have investigated the outcomes of different antihyperglycemic agents in patients with T2D who have undergone PAD revascularization. Several large-scale clinical trials have indicated that DPP4i had a neutral effect on cardiovascular composite outcomes in patients with T2D [6–9]; nevertheless, these trials did not explore the outcome of adverse lower limb events. Other landmark clinical trials have demonstrated that SGLT2i are beneficial in reducing the risks of HFH and other major adverse cardiovascular events [3–5]. However, the CANVAS trial reported a higher rate of amputations in the canagliflozin (SGLT2i) group compared with the placebo group (0.63 vs. 0.34 per 100 person-year, p < 0.001) [3]. This adverse reaction can be attributed to the diuretic effect of SGLT2i, which caused volume depletion, leading to inadequate circulation in the distal peripheral vasculature [3, 27]. In addition, previous cohort studies including patients with T2D have revealed that SGLT2i were associated with an increased risk of amputation compared with other antihyperglycemic agents [28–30]. By contrast, a meta-analysis revealed no significant association between SGLT2is and an increased risk of amputation [31]. A large-scale observational study of patients with T2D and concomitant PAD reported that SGLT2i were associated with lower risks of adverse lower limb events compared with DPP4i [32]. Accordingly, evidence concerning the association between SGLT2i use and the risk of lower limb amputation is inconclusive. Our data reveal that the SGLT2i and DPP4i groups had similar incidence rates of repeated revascularization (5.63 and 6.67 per 100 person-years, respectively) and lower limb amputation (1.25 and 1.60 per 100 person-years, respectively), to the findings of a relevant study that included patients who had received PAD revascularization [23]. These findings in such a high-risk population support that SGLT2i are safe glycemic control agents for patients with T2D and concomitant PAD, even after revascularization.
A previous meta-analysis of three clinical trials revealed the benefit of SGLT2i in reducing the risk of cardiovascular death [33]. Other meta-analyses have also reported that SGLT2i reduced the risk of adverse kidney outcomes [34, 35]. These findings are consistent with those of our study, further demonstrating that SGLT2i are associated with lower risks of cardiovascular death and composite renal outcomes in patients with T2D who have received PAD revascularization. Regarding renal dysfunction in patients after PAD revascularization associated with higher risks of adverse cardiovascular, limb, and all-cause mortality events [12, 13], renal protection should be an important issue, that our data indicating the benefits of renal outcomes of SGLT2i. Our study indicated that SGLT2i were not associated with a lower risk of HFH compared with DPP4i, which is inconsistent with the results of previous landmark research [33]. A possible explanation for no reduction in HFH could be the fact that after propensity matching, on similar 6 to 7% in both cohorts had heart failure. Nevertheless, our previous study including a cohort of patients with T2D and concomitant PAD selected from the Taiwan NHIRD reported that compared with DPP4i, SGLT2i were associated with a lower risk of HFH [32]. Therefore, the inconsistency between the findings of the present study and those of the aforementioned landmark research may be due to differences in study design and settings or may be due to the fact that the benefits of SGLT2i over DPP4i in patients with advanced-stage PAD requiring revascularization are limited. Additional randomized and prospective studies are should be conducted to investigate the effects of SGLT2i on HFH in patients with T2D and advanced-stage PAD requiring revascularization.
This study has several limitations. First, although PSM was useful for balanced comparisons, it could not account for unknown confounders such as unmeasured variables, prescribing behavior, and medical adherence in this retrospective cohort study. In addition, the findings of observational studies should be interpreted with caution because they might be subject to time-related biases such as immortal time and time-lag biases, which may exaggerate the mortality effects. Accordingly, to avoid immortal time bias, we included only new prescriptions for SGLT2i or DPP4i after the date of PAD revascularization [36, 37]. Furthermore, to avoid time-lag bias from the prescriptions for the study drugs, we selected the same DPP4i agents as the comparator and included study patients with a similar disease stage such as that requiring PAD revascularization [29, 37]. Second, the NHIRD does not contain laboratory data such as glycohemoglobin (HbA1c) or serum creatinine levels. HbA1c levels have been reported to be associated with the risk of cardiovascular and limb events in patients with T2D [24–26, 38]. In addition, even after adjustment for CKD, the diagnosis of CKD based on coding could not represent the severity of CKD, which may influence the outcomes in patients with T2D [39]. Third, miscoding and misclassification of underlying comorbidities and outcomes registered by each physician are another limitation of the study. Therefore, to improve the accuracy of study outcomes, we considered only primary discharge diagnoses in the cohort. Finally, we investigated only Asian patients, and whether our results can be extrapolated to other races remains unclear.
In conclusion, we observed that compared with DPP4i, SGLT2i were associated with lower risks of cardiac death and composite renal outcomes but were not associated with increased risks of adverse limb events in patients with T2D who had received PAD revascularization. Our study findings suggest that SGLT2i constitute an effective and safe alternative to DPP4i in such a high-risk population.