Method for Determining the Stroke Volume of a Heart, Method for Determining the Electrode Positions Therefor, and Sheet Shaped Device Therefor

A method for determining the stroke volume of a heart of a human or animal body, wherein the heart is comprised in the thorax of the body, the method comprising:

• attaching electrodes to the front legs or arms or head, and the hind legs of the body;
• connecting an alternating current source to the left pair of front legs/arms or head, and hind legs;
• connecting an alternating current source to the right pair of front legs/arms or head, and hind legs;
• attaching a number of electrode pairs to the thoracic skin, such that the electrodes are in contact with the skin of the thorax at predetermined positions, wherein the electrode pairs are each connected to an independent input of a data acquisition/calculation device;
• determining the beginning the cardiac cycle and measuring with the number of electrode pairs on the thorax the voltage at the beginning of the cardiac cycle at the predetermined positions;
• measuring during the cardiac cycle with the number of electrode pairs on the thorax the voltages at the predetermined positions and determining the voltage changes vmeas(T) compared to the voltage at the beginning of the cardiac cycle;
• decomposing the vector of voltage changes vmeas(T) into an atrial component α(T) and ventricular component ψ(T), wherein both components are proportional to the vector of measured thorax voltages vmeas(T) by a weight factor wA and wV respectively;
• converting the ventricular component ψ(T) to a ventricular stroke volume, by multiplying the ventricular component with a constant, the constant being a predetermined volume change Vcalib divided by a ventricular component φcalib of a predetermined calibration measurement.

A sheet shaped device comprising exactly three electrodes:

• a ventricular electrode (V3),located near the caudal side of the heart in order to be located on or near the region of the thoracic skin having the largest voltage shift due to ventricular filling of emptying;
• an atrial electrode (A3),at a distance between 80 and 150 mm from the ventricular electrode (V3);
• and
• a reference electrode near the incisura jugularis on the cranial end of the sternum.