Stroke Risk Analyser SRA II

Atrial Fibrillation (AF) is a pathology of the heart rhythm: the atria are contracting permanently or in the form of attacks at a rate of more than 350 contractions per minute. At the same time the coordination of the actions of atria and heart chambers is disturbed or completetly interrupted. Consequently the performance of the heart decreases while the risk of forming blood clots within the quickly moving atria increases. Such blood clots could move through the vessels into the brain for example, where they can cause a stroke.

The most precise way to diagnose atrial fibrillation is using the electrocardiogram (ecg), that is the recording of the electrical field created by the activity of the heart muscle. The various phases of this activity shine up as a typical shape in the ecg called the PQRST-complex. In the subsequent depiction of an ecg of two heart beats one can easily identify the so-called P-wave, that is caused by the electric excitation of the atria. The dominant R-peak corresponds to the full excitation of the heart chambers during their contraction phase.

ecg of 2 heart beats without arrhythmia

During atrial fibrillation the PQRST-complex is deformed in a specific way, that is used in the diagnosis of AF. In the subsequent graphic of an ecg during atrial fibrillation two phenomena are visible: the P-wave cannot be marked off clearly or is missing and the so-called isoelectric line, which corresponds to the heart muscle in rest, is absent.

 

 

ecg during atrial fibrillation

The disturbance of the coordination between atria and heart chambers causes characteristic changes in the morphology of the ecg's Lorenz plot (see the project Computer-aided detection of heart beat arrhytmias utilizing the electrocardiogram Computer-aided detection of heart beat arrhytmias utilizing the electrocardiogram).

 

 

2-dim. Lorenz plot during atrial fibrillation

In the project an algorithm for the detection of such morphological patterns was developed. This algorithm was implemented into the Stroke Risk Analyser II built by the enterprise apoplex medical GmbH, a hand-held device for the diagnosis of atrial fibrillation based on a 1-hour-ecg.