Kino-cardiography (KCG) is a non-invasive and non-obtrusive technique based on the measure of body vibrations produced by the myocardium contraction and movements of the blood through the aorta. It is based on accelerometers/gyroscopes placed on the thorax (Seismocardiography) and in the lumbar region (Ballistocardiography). It measures the total heart kinetic energy (HK), which is hypothesized to be a proxy measure of Stroke Volume (SV). This study compares KCG to Echocardiography.
The study is a double blind cross-over setting where infusions of Dobutamine and placebo were performed on 34 healthy volunteers (18 females). Mean age was 25 years (± 2), mean BMI was 22 kg/m2 (± 2). A baseline record was followed by 3 sessions of increasing doses of Dobutamine or saline solution (5, 10, 20 μg/kg.min). During each of the 8 sessions, a classical Echocardiography was followed by a 90 s recording of KCG. The subjects were randomly assigned to group 1 (18 subjects) receiving the Dobutamine injections first, or group 2 (16 subjects) receiving the injections in the opposite order.
Linear and rotational kinetic energies were measured on KCG and summed to obtain total heart kinetic energy (HKtot); SV and CO were assessed through Echocardiography.
Analysis was done in full blind: for each subject, the total HK was sorted in ascending order; the 3 highest HK were then supposed to correspond to the 3 doses of Dobutamine. A global sensitivity of 96.91% and a specificity of 98.01% are found. Furthermore, a significant (p < 0.0001) correlation of 0.59 is found between Cardiac Output (CO) measured by Echocardiography and Kinetic Energy (HKtot) measured by KCG. Moreover, interesting trends of HKtot and SV is observed, on Figure 1, as they increase with Dobutamine levels and remain stable with placebo (saline solution).
The promising results of this study allow us to believe that Kino-Cardiography could be a powerful tool to monitor and screen different pathologies characterized by inotropic cardiac state impairments. Additional clinical validations are also planned with patients suffering from hypertension or heart failure.
1Université Libre de Bruxelles, Brussels, Belgium
2Cardiology Dept, Hôpital Erasme, Brussels, Belgium