A Pilot Study of External Counterpulsation on Reactive Hyperemia, Levels of Glycemia and Metabolic Parameters in Type 2 Diabetes Mellitus

Introduction: External counter-pulsation (ECP) involves cuff inflation over the lower extremities to generate sheer stress, thereby improving endothelial function and anginal symptoms in coronary artery disease. Endothelial dysfunction is also involved in the pathogenesis of T2DM. We hypothesized that 1) ECP will be associated with an improvement in endothelial function in T2DM as measured by peripheral artery tonometry, and 2) explored whether this would vary with different dose and frequency regimens. A shorter or less intensive regimen could potentially reduce cost and improve patient compliance if a similar therapeutic response is achieved. Methods: This single-center prospective study in a tertiary institute in Singapore involving 46 adults with T2DM of HbA1c between 7 to 10%, who were randomly assigned to receive 35 sessions of ECP at different regimens and duration. Subjects in arm 1 received 1-hour daily sessions 5x per week for 7 consecutive weeks, subjects in arm 2 received 0.5-hour sessions 5x per week for 7 consecutive weeks, and subjects in arm 3 received 1-hour sessions 3x per week for 12 consecutive weeks. Endothelial function was evaluated by reactive hyperemia index (RHI) via peripheral arterial tonometry measured at the start, midpoint and end of study. Other secondary outcomes included fasting glucose, homeostatic model assessment of insulin resistance (HOMA-IR), HbA1c, blood pressure, lipid profile, weight and vibration sense. Results: 42 subjects completed the 35-session course of ECP. Mean age was 56.1±9.3 years, duration of diabetes 8.8±4.7 years, baseline RHI 2.0 (1.3–3.7) and baseline HOMA-IR was 3.1 (0.5–18.7). All regimes of ECP were well-tolerated. There was no change in RHI across all 3 regimens of ECP individually or collectively at the end of the study (ΔRHI +0.01%, p=0.458). Glycaemic markers of fasting glucose, HbA1c and HOMA-IR, as well as blood pressure, lipid profile, weight and vibration sense also remained unchanged at endpoint. Subgroup analysis showed a significant improvement in RHI (ΔRHI +20.6%, p=0.0178) in 7 subjects with more severe endothelial dysfunction (defined by RHI<1.67) at baseline who had a trend to having a longer duration of diabetes, however there was no improvement in fasting glucose, HbA1c, HOMA-IR or metabolic parameters in this group. Conclusion: ECP did not show a beneficial effect on endothelial function, glycemic control or metabolic parameters in this South-East Asian population with T2DM at any of the three regimens. This may partly be explained by less severe endothelial dysfunction and less insulin resistance in our population at baseline. Future studies of ECP may investigate its potential benefits in a larger population of T2DM with more severe endothelial dysfunction, higher insulin resistance and/or longer duration of diabetes at baseline.