title: A portable infrared photoplethysmograph: heartbeat of Mytilus galloprovincialis analyzed by MRI and application to Bathymodiolus septemdierum.
abstract: Infrared photoplethysmogram (IR-PPG) and magnetic resonance image (MRI) of the Mytilus galloprovincialis heart were obtained simultaneously. Heart rate was varied by changing temperature, aerial exposure and hypoxia. Higher heart rates (35-20 beat min-1) were usually observed at 20°C under the aerobic condition, and typical IR-PPG represented a single peak (peak v). The upward and downward slopes of the peak v corresponded to the filling and contracting of the ventricle, respectively. A double-peak IR-PPG was observed in a wide range of heart rates (5 to 35 beats min-1) under various conditions. The initial peak v corresponded to the filling of the ventricle, and the origin of the second peak (v') varied with the heart rate. A flat IR-PPG with a noise-level represented cardiac arrest. Although large movement of the shells and the foot caused slow waves or a baseline drift of the IR-PPG, the heart rate can be calculated from the v-v interval. Based on these results, we assembled a portable IR-PPG recording system, and measured the heartbeats of Bathymodiolus septemdierum (Mytilidae) for 24 h on a research vessel just after sampling from the deep sea, showing that IR-PPG is a noninvasive, economical, robust method that can be used in field experiments.
authors.affiliation: Department of Marine Ecosystem Dynamics, Division of Marine Life Science, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa 277-8564, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Seo
authors.affiliation: Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki 444-8787, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Sazi
authors.affiliation: Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki 444-8787, Japan.
authors.forename: Morio
authors.initials: M
authors.lastname: Togawa
authors.affiliation: Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki 444-8787, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Nagata
authors.affiliation: Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki 444-8787, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Murakami
authors.affiliation: Department of Marine Ecosystem Dynamics, Division of Marine Life Science, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa 277-8564, Japan.
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Kojima
authors.affiliation: Department of Regulatory Physiology, Dokkyo Medical University School of Medicine, Tochigi 321-0293, Japan yseo@dokkyomed.ac.jp.
authors.forename: Yoshiteru
authors.identifier: http://orcid.org/0000-0001-9775-4738
authors.initials: Y
authors.lastname: Seo
keywords: Arrhythmia; Bivalve; Cardiac arrest; Cardiac cycle; MRI; Plethysmography