6.8.2013 Flashcards
J point in ECG corresponds to which phases of cardiac action potential
Phase 1 and early phase 2
Action potential of epicardial and endocardial cells
Epicardial action potential is shorter because outward K+ movement of phase 1 is prominent in it
ST segment of ECG corresponds to which phase of cardiac action potential
Phase 2
Cause of spontaneous diastolic depolarisation
Funny channel
Ion responsible for phase 0 of pacemaker action potential
Calcium
RMP of pacemaker cells
-60mV
ECG marker of sinus node discharge
None
Components of P wave
First half is due to rt atrial activity,second half is due to left atrial activity
Duration and amplitude of p wave
Less than 2.5 boxes(0.10S and 0.25mV)
Duration of QRS complex
0.06-0.10S
Normal PR interval
0.12-0.20 s
Causes of QRS prolongation
Ventricular hypertrophy
Bundle branch block
Premature activation of ventricles by accessory pathway
QT interval
Longest QT that can be recorded in 12 lead ECG
Rule of thumb for QT interval for HR more than 70bpm
QT interval is equal to or less than half of RR interval
Bazett formula
QT interval in seconds/root of RR interval
Normal QTc
Men- 0.42s
Women- 0.44s
Prolonged QTc interval
Men- more than 0.44s
Women and children- more than 0.46s
Relationship between QT interval and action potential
Total duration of action potential
Calculation of QTc,which RR interval is measured
Preceding RR interval
U waves are best visible in which leads
V2 and V3
U waves and heart rate
Visible when heart rates are less than 65
Rarely visible in heart rates above 95
Mechanism of U wave
Repolarisation of HIS Purkinje system
Abnormal U wave
When they are equal to or exceed the T wave
In ECG phase 4 of action potential is reflected by
TQ segment
Osborne wave is also known as
J wave
What is Osborne wave?
Marked elevation of j point that results in h shaped QRS
Cause of Osborne wave
Hypothermia
Hypercalcemia
Epsilon waves
Notch in the end of QRS seen in V1-V3 in arrythmogenic rt ventricular dysplasia
Most upright p wave deflection is seen in
Lead 2
Measurement of duration of p wave
Atleast 3 leads that are measured simultaneously
Leads 1,2,V1
Cause of prolonged p wave
Lt atrial hypertrophy
Intraatrial block
Atrial Repolarisation wave
Ta wave
Prolonged PR interval
The whole 12-lead ECG is measured for the longest PR interval preferably leads I, II, and V1
Duration of QRS complex
0.06-0.10s
Low voltage QRS complexes
Tallest QRS in limb lead is less than 5mm and in chest leads is less than 10mm
Causes of low voltage QRS complexes
Peripheral Edema Anasarca Ascites Pericardial effusion Pleural effusion Obesity Emphysema
Prolonged QTc in bundle branch block or intra ventricular conduction defect of more than 0.12s
QTc more than 0.50s
QT dispersion
Difference btw longest and shortest QT interval
If more than 100ms,predisposition for ventricular arrythmia
J point elevation
Seen in normal individuals
Due to difference in potentials during early repolarisation and resultant current flow btw epicardium and endocardium
Normal ST elevation is seen in
Younger healthy males
Morphology of normal ST elevation
Concave
Seen more prominently in V2
Male pattern of ST elevation
More than 1mm
Sharp take off of more than 20 degrees
ST elevation due to early Repolarisation
Associated with j point
Commonly seen in V4
Frequently accompanied by tall and peaked T waves
ST elevation with inversion of T waves in precordial leads V3-V4
Normal variant
Causes of abnormal ST elevation
MI coronary vasospasm Acute pericarditis Ventricular aneurysm Ventricular hypertrophy Hyperkalemia Brugada syndrome Left bundle branch block
Repolarisation of M cells
End of T wave
Abnormal T waves
Notched
More than 5mm in limb leads or more than 10mm in chest leads
Symmetrical
Inverted
Causes of prominent U waves
Quinidine
Hypokalemia
Causes of inverted U waves
Myocardial ischemia
Hypertension
Valvular regurgitation
Mechanism of epsilon wave
Post excitation of free wall of right ventricle
