ECG And Rhythm Disorders Flashcards
Relevance of ECG
Detects conduction abnormalities,structural abnormalities and perfusion abnormalities
Relatively cheap and easy to undertake,reproducible between people and centers,quick turnaround on results
Vector
Has both magnitude and direction
The greater rhe deflection the more muscle
P,QRS,T waves
P wave is electrical signal that stimulates contraction of atria
QRS is electrical signal that stimulates contractions of ventricles
T wave signifies relaxation of ventricle
Cardiac vectors
SAN:
autorhytmic myocytes,atrial depolarization (p wave)
AVN:
Isoelectric ecg, slow signal transduction and protective
Bundle of his:
Rapid conduction,insulated
Bundle branches:
Septal depolarization AVN (Q)
Purkinje fibres 1
Ventricular depolarization (R)
Purkinje 2
Late ventricular depolarization (s)
Fully depolarized ventricles show isoelectric ECG
Repolarisation seen as T wave
Where do the leads measure activity from
Lead I from right arm to left arm
Lead II from right arm to left leg
Lead III from left arm to left leg
Placement of leads on chest
V1-right eternal border in 4 ICS
V2-left eternal border in 4 ICS
V4-mid claviculad line in 5th ICS
V3-halfway between V2 and V4
V5-Anterior axillary line at level of V4
V6-mid axillary line at level of V4
Polarity of leads
lead I,II,III are bipolar
Rears are unipolar
Plane of chest vs limb leads
Chest leads are horizontal limb leads coronal
Cardiac axis
Work out positive and negative deflections for both leads,draw triangle and find angle using tan
ECG reporting procedure
Recording correct
Review signal and quality of leads
Edify voltage and paper speed
Review patient background
Sinus rhythm
Normal
Each p wave followed by QRS
rate regular and normal
Sinus bradycardia
Each p wave followed by QRS
Rate regular and slow
Can be healthy caused by medication or vagal stimulation
Sinus tachycardia
Each p wave followed by QRS
Rate regular and fast
Often physiological response eg running
Sinus arrhythmia
Each p wave followed by QRS
rate is irregular and normalish rate
R-R varies with breathing cycle
When breathing out PNS activated causing decreased HR
When breathing in SNS activated causing increased HR
Atrial fibrillation
No distinct p wave
Ossicikatinf baseline as atria contract asynchronously
Turbulent flow pattern increases clot risk
Atria not essential for cardiac cycle due to effect of gravity that can allow ventricles to fill naturally
Rhythm can be irregular and rate slow
Atrial flutter
Regular saw tooth pattern in baseline (II,III,aVF)
Atria to ventricular beats at a 2:1 ratio or higher
Saw tooth not always visible in all leads
First degree heart block
Persistent prolongation of PR interval caused by slow AVN conduction
Regular rhythm
Most benign heart block and progressive disease of ageing
Second degree heart block (Mobitz I)
Progressive prolongation of PR interval until best skipped (gets longer and longer and gone)
Most p waves followed by QRS
regularly irregular caused by diseased AVN
Aka wenckebach
Second degree mobits II
p waves are regular but only some followed by QRS
No P-R prolongation
Regularly irregular (successes to failures or random)
Can rapidly deteriorate into third degree
Third degree (complete)
P waves and QRS are regular but no relationships
P waves can be hidden
Non sinus rhythm
Ventricular tachycardia
P waves hidden-dissociated atrial rhythm
Rate regular and fast
At high risk of deteriorating into fibrillation
Shockable rhythm
Ventricular fibrillation
Heart rate irregular and 250bpm and above
Heart unable to generate output
Shockable rhythm
ST elevation
P waves visible and followed by QRS
Rhythm regular and rate normal
ST segment elevated above isoelectric line
caused by infarction -tissue death by hypoperfusion
ST depression
P waves visible and followed by QRS
Rhythm regular and rate normal
ST depressed below isoelectric line
Caused by myocardial ischemia,hypokalaemia or reciprocal changes
What causes differences in ecg cardiac axis
Height to width ratio
As people grow the heart size changes ,ratio not the same so cardiac axis difference
What’s normal cardiac axis
-30 to 90 degrees
Degrees for each lead
0 lead I
60 lead II
90 avf (points at foot)
120 lead III
-150 avr (right foot)
-30 AVL (left arm)
What leads measure RCA
lead II,III,AVF
What leads measure LAD
V1,V2,V3,V4
What measures left coronary artery
Lead I,aVL,V5,V6
RAD axis
90 to 180
LAD
-30 to -90
Extreme axis deviation
-90 to 180 degrees
