Subgroup analyses
Subgroup analyses were performed using the stent length (≤10 cm versus
>10 cm), the stent type (Thoraflex®Hybrid, E-vita®, Frozenix®, and
Cronus®), male predominance (≤74% versus
>74% male), and the chronicity of the operation (elective
versus non-elective). The categorization by the stent length led to
pooled estimates associated with a lower heterogeneity regarding
reoperation for bleeding among those implanted longer device (6%
[95% CI 2 to 10]; I2 = 79.36% in ≤10 cm versus
8% [95% CI 5 to 11]; I2 = 65.74% in
>10 cm); however, the test of group differences for
reoperation for bleeding was non-significant (p=0.45; Figure 4). The
subgroup by the stent type showed substantial decrease in the
heterogeneity (I2 = 0.01% for Thoraflex Hybrid,
I2 = 53.95% for Evita, I2 = 0.01%
for Frozenix, and I2 = 54.41% for Cronus; Figure 5)
and a significant difference between groups (p = 0.001). However, no
effect on heterogeneity was observed in subgroups by the male
predominance (Figure 6). The subgroup by the chronicity of operation
also resulted in less heterogeneity among patients undergoing elective
compared to non-elective operations (8% [95% CI 3 to 13];
I2 = 29.22% in elective versus 6% [95% CI 3 to
9]; I2 = 80.56% in non-elective; Figure 7). The
effect of subgroup analyses on the pooled rate of in-hospital mortality
was more pronounced. The heterogeneities improved among patients
implanted stent >10 cm compared to those implanted stent
≤10 cm (I2 = 0.06% versus I2 =
81.90%; Supplementary Figure 2-A). The categorization by the stent type
led to substantial improvement of heterogeneity (I2 =
0% for Thoraflex Hybrid, I2 = 0.06% for Frozenix,
I2 = 0.01% for Evita and I2 =
42.48% for Cronus®, Supplementary Figure 2-B).
However, the subgroups by the male predominance did not significantly
decrease the heterogeneity (Supplementary Figure 2-C). Moreover, it
disappeared among patients undergoing elective surgeries compared to
those undergoing non-elective surgeries (I2 = 0%
versus I2 = 66.18%; Supplementary Figure 2-D). When
excluding two of five studies with a wide 95% CI for the number of
patients with postoperative
bleeding,31,44the heterogeneity was significantly improved 11% (95% CI 8 to 15;
I2 = 12.97%).