High-intensity interval aerobic exercise improves brachial FMD in coronary artery disease and heart failure

This network meta-analysis evaluated the impact of various exercise modalities on brachial flow-mediated dilation (FMD) in a population of 6,818 adults diagnosed with coronary artery disease or chronic heart failure. The study aimed to compare several distinct protocols against usual care (UC) to determine which interventions most effectively promote vascular adaptation.

The included interventions were categorized into aerobic exercise (AE), resistance exercise (RE), and combined exercise (CE). Specific modalities included moderate-intensity AE (MAE), high-intensity interval AE (HIIE), moderate-intensity RE (MRE), high-intensity RE (HRE), moderate-intensity CE (MCE), and high-intensity CE (HCE). These were compared against standard usual care protocols to assess changes in FMD, a key indicator of endothelial function.

Primary outcome results indicated that MAE, HIIE, MCE, and HCE all significantly improved brachial FMD compared to usual care. Specifically, the improvements were: MAE (2.04%, 95% CI: 1.01-3.07), HIIE (3.47%, 95% CI: 2.02-4.92), MCE (2.71%, 95% CI: 0.05-5.36), and HCE (8.25%, 95% CI: 3.18-13.32). In contrast, moderate-intensity RE (MRE) did not show a significant improvement in FMD compared to usual care. When comparing specific modalities, HIIE outperformed MAE by 1.43% (95% CI: 0.09-2.78).

To assess the robustness of these interventions, a Surface Under the Cumulative Ranking Curve (SUCRA) analysis was performed. HIIE was identified as the most robust high-performing intervention with a SUCRA value of 84.0%. While HCE demonstrated the highest SUCRA value at 98.2%, this finding was noted to be less stable because it relied on data from only a single group. Other modalities showed lower robustness scores, with MRE at 61.6% and MCE at 61.3%.

Safety and tolerability data were not reported in the included studies for any of the exercise modalities. Consequently, specific adverse event rates or discontinuation rates are unknown from this analysis. The study notes that because it includes both randomized and non-randomized trials, the results represent an association/effect of exercise modalities on FMD rather than a definitive causal link established solely through controlled trials.

Methodological limitations include the fact that HCE results were based on a single group, which may limit the generalizability of its high SUCRA ranking. Furthermore, because the analysis includes non-randomized data, some bias may be present in the reported effect sizes for certain modalities. These findings should be viewed as evidence supporting the efficacy of specific intensities rather than an absolute confirmation of all combined protocols.

Clinically, these results suggest that HIIE is a supported primary strategy for promoting vascular adaptation in patients undergoing cardiac rehabilitation. While multiple forms of exercise provide some benefit over usual care, high-intensity interval aerobic training shows more robust evidence for improving endothelial function. However, because randomized trials are still needed to confirm the efficacy of high-intensity combined protocols (HCE), clinicians should proceed with caution when prescribing HCE specifically.

Questions remain regarding the long-term sustainability of these FMD improvements and the specific optimal duration for each modality. Additionally, more randomized controlled trials are necessary to isolate the effects of combining resistance and aerobic components in patients with heart failure compared to isolated high-intensity aerobic training.