P038 Characterising Pulse Wave Amplitude Drops in Patients with Acute Coronary Syndrome

Pulse wave amplitude derived from photoplethysmography signals is a surrogate measure of autonomic function and vascular response. Recent studies have demonstrated low pulse wave amplitude drop(PWAD) index to be associated with increased cardiovascular risk in obstructive sleep apnoea(OSA). The nature of PWAD in patients with cardiovascular disease remains unknown. We aimed to characterize PWAD in patients with acute coronary syndrome(ACS) diagnosed with OSA in terms of cardiovascular measures. We studied 70 patients with ACS (age:58[52,63]years, BMI:27[24,30]kg/m2). A level 2 polysomnogram was conducted to confirm OSA diagnosis within 6 months after discharge. Cardiovascular measures of heart rate variability(HRV), baroreflex sensitivity, pulse wave velocity (PWV) and endothelial function(FMD) were measured. PWAD was analysed using a validated algorithm. PWAD with an amplitude reduction of >30% from baseline and a duration >4 heartbeats were identified. PWAD frequency, duration, amplitude, area under the curve(AUC), descending and ascending slopes were calculated. There was no relationship between PWAD frequency and AHI (r=0.057, p=0.642). PWAD amplitude (rs= 0.308, p=0.031) and duration (rs= -0.319, p= 0.025) correlated with baroreflex effectiveness index. After controlling for age, gender and BMI, baroreflex effectiveness index was associated with PWAD duration (β±SE: -0.009±0.003, p=0.009). Aortic augmentation index correlated with PWAD duration (rs= 0.3565, p=0.0041). HRV parameters, FMD and PWV did not correlate with PWAD parameters (data not shown). These preliminary findings suggest PWAD duration and amplitude are not associated with OSA severity in patients with ACS. However PWAD may be appropriate markers of vascular and autonomic nervous system response in patients with cardiovascular disease.