Table 4: System objective classification and the number of classes.

Aim/N of classes	2 classes	3 classes	5 classes	6 classes
Diagnosis of CAD	[13, 36, 38, 39, 41, 42]	[37, 40]	-	-
Risk or mortality prediction	[18, 19, 28-34]	[27]	[16]	[35]
Classification of cardiac alarm as true or false	[20, 21]	-	-	-
ECG signal and heart sound classification	[23]	-	[43]	-
Other	[24-26]	-	-	-