Fig. 8
Subgroup analysis of the association between restenosis and different continents. The vertical dashed lines indicate the pooled summary estimate (95% CI) for all studies in Fig. 8 (‘Europe’ subgroup, RR = 1.43, 95% CI, 1.21–1.69; I2 = 49.6%, P < 0.05. ‘America’ subgroup, RR = 1.53, 95% CI, 1.22–1.92; I2 = 68.2%, P = 0.004.). The area of each square is proportional to the inverse variance of the estimate. The horizontal lines indicate the 95% confidence intervals of the estimate