Development of Measurement Concepts for Canine Dry Electrode Electrocardiogram and Human Cardiac Construct Contraction Force Measurements

Interest towards personal health has been growing during recent years. Heart rate (HR) monitoring has become an everyday life practice. The importance of this can be put to a context with the fact that approximately 40% of human deaths are caused by cardiac diseases. In its most basic forms HR monitoring does not reveal all information which would be available with methods such as electrocardiogram (ECG).

The trend of health monitoring is also becoming more and more common with pets and animals. HR monitoring systems are available for these applications but as with humans they seldom offer opportunity to explore the ECG outside the clinical environment. There the equipment can be bulky and require attention to operate properly. Known issues with the ECG electrodes in animal applications are that they may require shaving, use of electrically conductive gel or may be painful for the animal. Therefore, low maintenance dry ECG electrodes would be beneficial for these applications.

Cardiac diseases can be treated with various therapy methods which often involve the use of cardiac drugs. Drug development however is expensive and time consuming. The development work includes drug toxicity testing which has been carried out with, for example, animal testing. This raises ethical questions in the development work. Also, it has been proven that these toxicity research results may not provide accurate information about the cardiac drug toxicity to humans; in addition, the efficiency of the drug may often vary from patient to patient. Advances in stem cell culturing has enabled the opportunity to fabricate human genome cardiac constructs which can be used in the drug testing. Action- and biopotential measurements can be carried out in the drug development testing procedures. However cardiac contraction force measurement has been proposed to reveal more information about the drug efficacy and toxicity than the biopotential measurements.

In this thesis two cardiac cycle measurement topics were studied 1) the dry canine ECG electrodes and 2) contraction force measurement system for human induced cardiac constructs. In order to study anomalies and abnormalities of the measured cardiac cycles, a pattern matcher analysis method is proposed for a classification and detection of those.

Five different dry canine ECG electrodes were constructed, and their performance was tested. None of these ECG electrodes required shaving or application of electrically conductive gel. The testing procedure was used to resemble everyday use of the electrodes. The highest average proportion of the correctly detected heartbeats of 95% was achieved with gold plated electrodes in a standing and sitting posture while the lowest figure was 41% with 12- pin polymeric electrode during walking.

Cardiac construct contraction force was studied with a single and dual axis piezoelectric cantilever force measurement systems. These were developed, fabricated, and evaluated for contraction force measurement of cardiac constructs in vitro. Maximum measured contraction forces ranged from 3.0 to 11.2 µN during the cycle. The coefficient of variation of these force measurements varied from 1.0% to 16.8% depending on the configuration of the measurement.