Electrocardiogram (ECG) is one of the most simple, easily accessible, affordable,
feasible and non-obtrusive examinations that evaluate the heart's electrical system to
detect heart diseases. The chronic disease that causes the most number of deaths
worldwide is Cardiovascular Diseases (CVD). It isn‟t only a concern of developed
nations but also the contrary. In a report authored by the WHO in 2005, it is mentioned
that about 80 percent of deaths throughout the world caused by cardiovascular disease
happen in low-income and middle income nations. Heart Sound (HS) and
ElectroCardioGram (ECG) auscultation are the most commonly used tools for the
diagnosis of cardiovascular diseases, providing complementary information like
facilitating evaluation of the electrical action of the heart (ECG) and providing
information about the mechanical action of the heart (HS).
Some of the other signals like PPG (PhotoPlethysmoGram) and ICG (Impedance CardioGram) are still employed
in research scenarios but less used in day-to-day practice. ECG as shown in figure 1 is a graphical representation of heart muscle electrical
Activation (Depolarization) and Relaxation (Repolarization). It is represented by
various waves, segments and intervals. "P‟ wave depicts atrial (upper chamber of the
heart) depolarization. "PR‟ interval gives information about the conduction of electrical
impulse from upper chamber to lower chamber of the heart. "QRS‟ wave depicts
depolarization of Ventricle (lower chamber of the heart). "ST‟ segment and "T‟ wave
give information about repolarisation of the Ventricle (lower chamber of the heart).
Predominant part of the ECG which depicts blockage is "ST segment‟. Commonly,
ECG is taken in 12 lead formats. There are many more leads, taken in specific
circumstances. Different lead views of cardiac electrical activity from various directions
in both horizontal and frontal axis can also be captured for identifying and localizing the
problem with reasonable accuracy.
