Abstract: We identified 31 studies (44 reports) including 27,071 participants and two ongoing studies. The risk of bias in the studies was low or unclear for several domains. Compared to the transfemoral approach, the transradial approach reduced short-term net adverse clinical events (NACE) (i.e. assessed during hospitalisation and up to 30 days of follow-up) (RR 0.76, 95% CI 0.61 to 0.94; 17,133 participants; 4 studies; moderate quality evidence), cardiac death (RR 0.69, 95% CI 0.54 to 0.88; 11,170 participants; 11 studies; moderate quality evidence). However, short-term myocardial infarction was similar between both groups (RR 0.91, 95% CI 0.81 to 1.02; 19,430 participants; 11 studies; high quality evidence). The transradial approach had a lower procedural success rate (RR 0.97, 95% CI 0.96 to 0.98; 25,920 participants; 28 studies; moderate quality evidence), but was associated with a lower risk of all-cause mortality (RR 0.77, 95% CI 0.62 to 0.95; 18,955 participants; 10 studies; high quality evidence), bleeding (RR 0.54, 95% CI 0.40 to 0.74; 23,043 participants; 20 studies; low quality evidence), and access site complications (RR 0.36, 95% CI 0.22 to 0.59; 16,112 participants; 24 studies; low quality evidence). Transradial approach for diagnostic CA or PCI (or both) in CAD may reduce short-term NACE, cardiac death, all-cause mortality, bleeding, and access site complications. There is insufficient evidence regarding the long-term clinical outcomes (i.e. beyond 30 days of follow-up).

Plain-language summary: Our search yielded 31 eligible studies comparing the transradial approach to the transfemoral approach in people undergoing diagnostic or therapeutic (or both) coronary catheterisation procedures in different settings, whether urgent (during heart attacks (myocardial infarctions)) or elective (planned procedure). The trials were carried out in many countries and regions, including Canada, China, Europe, Japan, and USA. We also identified two ongoing studies. The evidence was current to October 2017. Transradial access was associated with a reduction in the composite outcome (comprising two or more combined outcomes) of net adverse clinical events (NACE), including death from cardiac causes, myocardial infarction (injury of the heart muscle), stroke (insult to the brain), need to reintervene on the same site of coronary artery stenosis (narrowing), and bleeding during the first 30 days following intervention. When assessing individual outcomes, the risk of myocardial infarction and stroke was similar between groups. Transradial access reduced death from cardiac causes, death from all causes during the first 30 days following intervention, bleeding, and local complications at the access site. The transradial approach shortened the length of stay in hospital, but was associated with a higher radiation exposure and more technical failures requiring an alternate vascular access route. We rated the quality of the evidence for short-term myocardial infarction and all-cause death as high. We rated short-term NACE, cardiac death, and success of the procedure as moderate quality evidence. Evidence for bleeding and access site complications was low quality.