Background: The efficacy of external counterpulsation (ECP) on coronary collateral growth has not been investigated in a controlled randomized study.
Methods: In 20 patients with chronic stable coronary artery disease (CAD), the hypothesis was tested that ECP augments collateral function during a 1-minute coronary balloon occlusion. Before and after 30 hours of randomly allocated ECP (20 90-minute sessions over 4 weeks at 300mmHg inflation pressure) or sham ECP (same setting at 80mmHg inflation pressure), invasive collateral flow index (CFI, no unit) was obtained in 34 vessels without coronary intervention. CFI was determined by the ratio of mean distal coronary occlusive to mean aortic pressure both subtracted by central venous pressure. Additionally, coronary collateral conductance (occlusive myocardial blood flow per aorto-coronary pressure drop) was determined by myocardial contrast echocardiography, and brachial artery flow-mediated dilation (FMD) was obtained.
Results: CFI changed from 0.125 (0.073; interquartile range) at baseline to 0.174 (0.104) at follow-up in the ECP group (p=0.006), and from 0.129 (0.122) to 0.111 (0.125) in the sham ECP group (p=0.14). Baseline to follow-up change of coronary collateral conductance was from 0.365 (0.268) to 0.568 (0.585)ml/min/100mmHg in the ECP group (p=0.072), and from 0.229 (0.212) to 0.305 (0.422) ml/min/100mmHg in the sham ECP group (p=0.45). There was a correlation between the FMD change from baseline to follow-up and the corresponding CFI change (r=0.584, p=0.027).
Conclusions: ECP appears to be effective in promoting coronary collateral growth. The extent of collateral function improvement is related to the amount of improvement in systemic endothelial function.
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