Thesis - Instituto de Telecomunicações

50 CHAPTER 3. INFORMATION SOURCESFigure 3.9: Diagram of an ECG signal with the notable complexes identified according tothe standard notation.(a) normal sinus rhythm - between 60 and 100 BPM - normal heart beat during most ofthe time;(b) sinus bradycardia - less than 60 BPM - slow heart beat;(c) sinus tachycardia - more than 100 - fast heart rhythm due to exercise, stress, or somepathological condition.The ECG is widely used for detection of cardiac pathological states such as [28]:(a) arrhythmia - where the sinus tachycardia can be considered as an anomaly if the personis not in exercise;(b) hypertrophy - is caused by overload of the heart valves;(c) ischemia and infarction - when the muscle has lack of oxygen (ischemia) or the muscleis already dead. In these cases, an area of the heart is electrically silent.The ECG signal can also be used to extract information related to the heart function:(a) pace maker rhythm - for diagnosing the regular functioning of a pacemaker;