Rhytham strip ;- To determine heart rate and rhythm
cardiac axis ;- normal QRS complex +ve in leads I and II
P-wave space ;- tall P waves denotes right atrial enlargement(p pulmonale) and nothed p waves denotes lerft artial enlargement
PR intreval ;- Normal=0,12-0.20secs. prolongation denotes impaored av node conduction, A short PR interval occurs in "wolf prkinsns white syndrome"
QRS duration ;- If >0.12 sercs then venticular conducrion is abnormal(left or right bundle block)
QRS ampitude ;- Large QRS complex occcur in slim young patients and in patient with left ventricular hypertrophy
Q waves ;- may signify previous myocardial infraction(MI)
ST segment ;- ST elevation may signify MI, pericarditis or left ventricular aneurysm ST depression may signify MI 0r ischemia
T waves ;- T wave inversion has a many causes including myocardial infraction or ischemia and electrolytes disturbance
QT interval ;- Normal 0.42 secs . QT prolongation may occur with congenital long QT syndrome, low k+ mg2+ or ca2+, and some drugs
ECG convention
Depolarizatoin towards electrode: p0sitive deflection
Depolrisation away from electrode: negative deflection
Sensitivity: 10mm=1mV
Paper speed: 25mm/s
Each large (5mm) square=0.2s
Each small (1mm)square =0.04s
Heart rate= 1500/RR interval(i.e. 300/numbers of large squires between beats
