The heart rhythm as detected by an ECG is the result of the conduction system which is used by the heart to coordinate the heart beat. The electrical impulse is started by the SA node at the top of the heart. At this point the conduction system of the heart passes the impulse across both atria (top chambers of the heart) and to the AV node. The AV node acts as a time delay and then passes the impulse on to the conduction system in the Ventricles (lower chambers of the heart). The ventricles are larger than the atria because they actually pump the blood out of the heart and to the lungs or the rest of the body. Due to their larger size their depolarization produces the largest deflection on the ECG reading. This large deflection is referred to as the ventricular complex or the QRS complex. After the heart is done contracting the tissue must repolarize so that it will be ready to contract again. This repolarization shows up on the monitor as the "T" wave, or the final wave after the large QRS complex.

The two lethal rhythms mentioned earlier, V-Tach and V-Fib, both cause death by interfering with the standard electrical coordination of the heart.

If either of these rhythms is left untreated they will rapidly degenerate to asystole or flatline. In asystole the electrical activity of the heart has stopped and defibrillation is no longer capable of restarting it. At this point the only hope for survival is aggressive pharmaceutical action through Advanced Cardiac Life Support algorithms, but even these methods are often ineffective.

In addition to identifying cardiac rhythms that present the possibility of death within the next few minutes, signal analysis could also identify potentially life threatening conditions before they reach a state of cardiac arrest. Acute Myocardial Infarctions (AMIs) or Heart Attacks are among the top causes of death in the United States. While many people become aware of their AMI through clinical signs such as chest pain, other conditions such as Diabetes or pain from other illnesses may mask the presence of an AMI. In the hospital an AMI can be detected through its effect on the conduction system of the heart as shown by an ECG. An active AMI will result in a lack of Oxygen to some of the myocardium. The ischemic tissue has different conductive properties; as a result of these changes the T-wave of a patient suffering from Ischemia in the Myocardium will be inverted. By detecting this rhythm we would allow patients to be alerted of their problem before they have reached a state of full arrest.

With the increasing use of electrocardiograms and the application of devices such as defibrillators, proper measurement and identification of ECG signals is extremely important. However with such signals on the order of microvolts, significant levels of noise corruption make this very difficult. Having proper filters to remove such noise and allow for proper signal identification is crucial. This project aims to apply filtering algorithms in hopes of identifying some of the most common types of ECG signals.

In addition to V-Tach and V-Fib the program identifies the following rhythms:

Figure 1

Figure 2

Figure 3

Footer

This work is licensed by _ under a Creative Commons Attribution License (CC-BY 2.0), and is an Open Educational Resource.

Last edited by _ on Dec 13, 2005 11:59 pm US/Central.