​Differential diagnosis of ST segment elevation on ECG are : 
-ischemic heart disease
-acute pericarditis 
-vagotonia 
-pulmonary embolism 
-hypothermia 
-advanced hypokalemia 
-left bundle branch block 
-left ventricular hypertrophy 

​Differential diagnosis of systemic diseases causing ST segment depression on ECG are : 
-dermatomyositis
-systemic lupus erythematosus 
-rheumatoid arthritis 

​Differential diagnosis of drugs / toxins causing ST segment depression on ECG are : 
-Thallium 
-Quinine 
-digitalis 
-carbon monoxide
-barbiturates 
-anti arrhythmics
-mushroom toxins 
-nicotine 

​Differential diagnosis of intraventricular blocks causing non ischemic causes of ST segment depression on ECG are : 
-Wolff Parkinson White Syndrome  
-left bundle branch block 
-right bundle branch block 

​Differential diagnosis of non ischemic causes of ST segment depression on ECG are : 
-myocarditis 
-right ventricular hypertrophy 
-left ventricular hypertrophy 
-mitral valve prolapse
-intraventricular blocks
-drugs
-toxins 
-central nervous system disease
-hypokalemia 
-systemic diseases
-pheochromocytoma 
-hyperthyroidism 

​Differential diagnosis of normal variants causing ST segment depression on ECG are : 
-hyperventilation 
-sinus tachycardia 
-pseudo ST depression 

​Differential diagnosis of sub endocardial ischemia causing ST segment depression are : 
-angina attack 
-exercised induced 

​Differential diagnosis of ischemic heart disease causing ST segment depression are : 
-non Q wave myocardial infarction 
-subendocardial ischemia 
-acute Q wave myocardial infarction 

​Differential diagnosis of ST segment depression are : 
-ischemic heart disease
-non ischemic causes 
-normal variant 

​Differential diagnosis of antihistaminics causing long QT interval on ECG are : 
-astemizol 
-terfenadine