Flow-mediated dilation
Seven articles containing 301 participants compared the FMD between 190 patients with CHF and 111 normal subjects. Based on a random-effects model, FMD was significantly lower in patients with CHF (SMD: -1.70%, 95% CI: -2.63 to -0.77, P < 0.001) (Fig. 4). At 13.7% relative risk reduction (RRR), TSA showed that the mean difference (MD) was − 2.63%, and the TSA-adjusted CI was − 3.25 to -1.96 (P < 0.0001). Based on a random-effect model, the blue z-curve crossed trial sequential monitoring (TSM) boundary in the graph above and the green z-curve after penalized tests crossed conventional (CON) boundary in the following graph comparing FMD between patients with CHF and normal participants (eFigure 2). In the subgroup analyses, meta-analysis indicated that there were significant differences between HFrEF groups and control groups (six trials, n = 185, SMD: -2.28%, 95% CI: -3.47 to -1.08, P < 0.001), while there were no significant differences between HFpEF groups and control groups (two trials, n = 116, SMD: -0.20%, 95% CI: -0.59 to 0.18, p = 0.299). For further validation, subgroup analyses were performed using TSA as well. As illustrated in eFigure 3, z-curve trends related to compare patients with HFrEF and normal subjects were the same as the trends in eFigure 2 (MD: -2.83%, TSA-adjusted CI: -3.42 to -2.31, P < 0.0001). However, z-curves did not cross CON and TSM boundaries in patients with HFpEF compared with normal participants (eFigure 4) (MD: -0.45%, TSA-adjusted CI: -4.14 to 3.24, P = 0.33). In conclusion, FMD was significantly higher in normal populations than patients with HFrEF, while in patients with HFpEF, further high-quality studies are needed.
Six articles, including 270 patients with CHF, compared FMD in the situations of exercise and non-exercise, wherein the overall numbers in both situations were equal. The increases of FMD value were statistically significant in the cases of exercise training (SMD: 4.36%, 95% CI: 2.25 to 6.46, P < 0.001) based on a random-effects model. At 13.7% RRR, TSA showed that the MD was 3.75, and the TSA-adjusted CI was 1.88 to 5.63 (P < 0.0001). Based on a random-effect model, the blue z-curve crossed the TSM boundary in the graph above, and the green z-curve after penalized tests crossed the CON boundary in the following graph comparing FMD between patients with CHF and normal participants (eFigure 5). We performed two subgroup analyses using meta-analysis, wherein one was based on types of CHF, and the other was made on exercise intensity. In the first subgroup meta-analysis, there were significant differences in patients with HFrEF after exercise training (six trials, n = 172, SMD: 5.96%, 95%CI: 2.81 to 9.05, P < 0.001), while there were no significant differences in patients with HFpEF (two trials, n = 98, SMD: 0.19%, 95%CI: -0.21 to 0.59, p = 0.348) (Fig. 5). In the second subgroup meta-analysis, there were statistically significant differences after both MIT (five trials, n = 226, SMD: 3.66%, 95%CI: 1.43 to 5.88, P = 0.001) and HIT (two trials, n = 44, SMD: 6.56%, 95%CI: 5.00-8.11, P < 0.001) in patients with CHF (Fig. 6). For further verification, we also performed TSA on these two subgroups. For the former subgroup, as showcased in eFigures 6 and 7, there was statistically significant improvement of FMD in patients with HFrEF after exercise training (MD: 5.04%, TSA-adjusted CI: 3.16 to 6.91, P < 0.0001), while further high-quality studies are still needed in patients with HFpEF (MD: 0.15%, TSA-adjusted CI: -1.10 to 1.40, P = 0.330). For the latter subgroup, as shown in the eFigures 8 and 9, the blue z-curve crossed the CON boundary, however, after one or two trials the z-curve went below the TSM boundary again, besides, the green z-curve after penalized tests went below the CON boundary again as well. No firm conclusions can be drawn, and further high-quality studies are needed in both MIT(MD: 3.04%, TSA-adjusted CI: -0.18 to 6.26, P = 0.006) and HIT (MD: 5.9%, TSA-adjusted CI: -5.29 to 17.12, P = 0.021) exercise. In conclusion, FMD significantly improved after exercise training in patients with HFrEF. However, although we got the negative result that there were no significant differences after exercise training in patients with HFpEF and positive results that MIT and HIT were beneficial to the improvement of FMD in patients with CHF, TSA did not further identify these outcomes. Further high-quality studies are needed.
There were two articles that compared 32 patients with CHF between MIT and HIT exercises. Based on a random-effects model, the improvement of FMD was significantly better in patients with CHF after HIT exercise compared with MIT (SMD: 2.88%, 95% CI: 1.78 to 3.97, P < 0.001) (Fig. 7). At 13.7% RRR, MD was 3.68%, and the 95% CI was 2.23 to 5.13 (P < 0.0001). Based on a random-effect model, the blue z-curve crossed the TSM boundary in the graph above, and the green z-curve after penalized tests crossed the CON boundary in the following graph (eFigure 10). In conclusion, the improvement of FMD was significantly better in patients with CHF after HIT exercise compared with the patients with CHF after MIT exercise.