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Biomedical Sensors and Data Acquisition
Published in Rajarshi Gupta, Dwaipayan Biswas, Health Monitoring Systems, 2019
In Figure 2.21, the R-peak position is considered the beginning of ventricular systole, representing closure of AV valves (tricuspid and mitral), also known as isovolumetric ventricular contraction. This generates the first component S1 of the PCG, audible as ‘lub’. This can be decomposed into four subcomponents. The initial component is due to shifting of ventricular blood toward the atria, closing both AV valves. The second component is due to abrupt tension in closed AV valves, slowing down the blood inside ventricles. The third component of S1 is due to oscillations of blood between root of aorta and ventricular walls. The fourth component is due to oscillations caused due to turbulent blood in the aorta and pulmonary valve. After the end of ventricular ejection, isovolumetric ventricular relaxation starts, represented by the T-wave of the ECG. This causes the fall of BP inside the ventricles below the large arterial pressure, resulting in the closure of aortic and pulmonary valves. The second PCG component, S2, audible as ‘dub’, starts after the end of T-wave. Its two subcomponents represent the closure of aortic valve (louder) and closure of pulmonary valve. The third heart sound component, S3, is due to rapid filling of blood from atria to ventricles, with both AV valves open. This causes the ventricular walls to vibrate. The final and fourth heart sound, S4, also known as atrial heart sound and occurs during atrial contraction, synchronous to the PQ segment of ECG. It is not audible [1].
Noninvasive Diagnosis Using Sounds Originating from within the Body
Published in Robert B. Northrop, Non-Invasive Instrumentation and Measurement in Medical Diagnosis, 2017
The third heart sound, S3, is a weak, very low-frequency sound caused by atrial blood being forced into the ventricles. It is considered normal in children and young adults, but can indicate left-ventricular hypertrophy or ventricular dysfunction in adults over 40. S3 occurs in the last third of diastole (Tilson-Chrysler 1994).
Heartlogic
TM: ready for prime time?
Published in Expert Review of Medical Devices, 2022
Ward A. Heggermont, Koen Van Bockstal
HeartLogicTM is a multiparametric algorithm of which the precise mathematical formula is unknown to its users. The algorithm has the following parameters embedded in its formula: a mathematical inference of the first and third heart sound (S1 and S3); thoracic impedance; respiratory parameters (more precisely: respiratory rate, respiratory volume, and respiratory volume variation); patient activity; and nightly heart rate and arrhythmias. All these parameters are analyzed and combined into a unitless number. When this number crosses a certain predefined threshold, this triggers an alert warning (Figure 1). When a patient is in alert state, the risk of impending WHF is strongly elevated [17]. When the HeartLogicTM number is below the threshold, the risk for WHF is very low (Figure 1). One of the crucial findings from the MultiSENSE study [17] is that the median time between the occurrence of an alert and the actual clinically relevant event (WHF) was 34 days, creating an important time window for therapeutic action [17].
Remote monitoring of implantable electronic devices to predict heart failure decompensation
Published in Expert Review of Medical Devices, 2021
Francesco Maria Brasca, Giovanni Battista Perego
The manufacturer Boston Scientific implemented its CIEDs with a specific algorithm for HF detection, named HeartLogicTM, combining first and third heart sound (S1 and S3), S3/S1 ratio, thoracic impedance, respiration, night heart rate, and patient activity.