Detecting Mechanical Alternans in the Photoplethysmography

Tudor Besleaga1, Nicola Toschi2, Antonio Canichella2, Andreas Demosthenous3, Pier Lambiase4, Michele Orini5
1University College London, 2Medical Physics, Department of Biomedicine and Prevention, University of Rome, 3Department of Electronic and Electrical Engineering, University College London, 4Institute of Cardiovascular Science, University College London, 5University College London, Department of Mechanical Engineering

Abstract

Mechanical alternans (MA) is a biomarker associated with mortality in heart failure patients. Its detection through continuous blood pressure (BP) monitoring is costly and impractical. In this work, we propose the use of photoplethysmography (PPG) as a non-invasive solution for MA detection. Continuous invasive BP and PPG were recorded and analyzed during ventricular pacing in 10 patients. The presence of MA was evaluated in BP and in features characterizing the PPG pulse morphology. Mechanical alternans was defined as an alternation in maximum dP/dt for a duration of 20 consecutive heart beats or more. Mechanical alternans was observed in BP in 5 patients (50%). The PPG-based MA surrogates showing the highest detection accuracy, were the maximum of the first derivative of the PPG pulse (V’M), and the pulse amplitude (A). Both features allow detection of MA positive patients with 100% sensitivity and 100% specificity. The magnitude of MA was correlated between BP and V’M PPG (R=0.92, p<0.001) and between BP and A PPG (R=0.89, p<0.001). In conclusion, MA can be accurately detected noninvasively through the PPG.