ECG & rhythm disorders Flashcards
What can be spotted on an ECG?
Conduction Abnormalities
Structural abnormalities
Perfusion abnormalities
What do upward and downward deflections signify?
Upward deflections are towards the +ve electrode
Downward deflections are towards the -ve electrode
What does the isoelectric line represent?
no net change in voltage, vectors are perpendicular to the lead.
What do steepness and width of the line denote?
Steepness - velocity
Width - duration
What does the P wave represent?
The electrical signal that stimulates contraction of the atria (atrial systole).
What does the QRS complex represent?
The electrical signal that stimulates contraction of the ventricles (ventricular systole)
What does the T wave represent?
The electrical signal that signifies relaxation of the ventricles.
Ventricular repolarisation
What does the Q wave represent?
Septal depolarisation
What does the R wave represent?
Ventricular depolarisation
What does the S wave represent?
Late ventricular depolarisation
Where do you place the first 3 leads?
Lead 1 - right arm to Left arm
Lead 2 - right arm to Left Leg
Lead 3 - Left arm to Left Leg
number of L’s represents the lead number
Where do you place V1?
Right sternal border in the 4th intercostal place
Where do you place V2?
Left sternal border in the 4th intercostal place
Where do you place V3?
Halfway between V2 & V4
Where do you place V4?
Mid clavicular line in the 5th intercostal place
Where do you place V5?
Anterior axillary line at the level of V4
Where do you place V6?
Mid axillary line at the level of V4
How many seconds does a square on an ECG represent?
0.04 seconds
What are the 5 steps of ECG interpretation?
Rate & Rhythm P wave & PR interval QRS duration QRS axis ST segment
What is the procedure for ECG implementation?
Is it the correct recording
Review the signal and quality of the leads
Verify voltage and paper speed
Review the patient background if available
What does the Cardiac axis show?
Cardiac axis gives the net vector of the R-wave, which is usually the largest electrical event as it is the biggest amount of muscle – normal range is -30 to +90 degrees
NEED TO KNOW HOW TO WORK IT OUT
What is normal sinus rhythm?
Each P wave is followed by a QRS wave 1:1
Rate is regular and normal 60-100
What is sinus bradycardia?
Each P wave is followed by a QRS wave 1:1
Rate is regular and slow e.g 56 bpm
What is sinus tachycardia
Each P wave is followed by a QRS wave 1:1
Rate is regular and fast e.g 110 bpm
What is sinus arrhythmia?
Each P wave followed by QRS wave
Rate in irregular and relatively normal
R-R interval varies with breathing cycle due to vagal nerve stimulation which reduces heart rate. arrhythmia is normal and probably present in half of us
What is atrial fibrillation?
Oscillating baseline - atria are contracting asynchronously
Rhythm can be irregular and rate may be slow
Turbulent flow pattern increases clot risk
Atria not essential for cardiac cycle
What is Atrial flutter?
Regular saw tooth pattern in baseline
Atrial to ventricular beats at a 2:1, 3:1 ratio or higher
Saw tooth not always visible in all leads
What are the characteristic’s of first degree heart block?
Prolonged PR segment/interval caused by slower AV conduction.
Regular rhythm
Most benign heart block but is a progressive disease of ageing.
What is second degree heart block Mobitz type 1?
Gradual lengthening of the PR interval until a beat is skipped
Most P waves followed by QRS; but some P waves are not.
Regularly irregular; Caused by a diseased AV node
Also known as Wenckebach
What is second degree heart block Mobitz type 2?
P waves are regular, but only some are followed by QRS.
No P-R prolongation
Regularly irregular, 2:1 successes to failures or random
Can rapidly deteriorate into third degree heart block
What is third degree heart block?
P waves are regular, QRS are regular, but no relationship.
P waves can be hidden within bigger vectors.
Non-sinus rhythm - back up pacemaker in action.
What is ventricular tachycardia?
P waves hidden - dissociated atrial rhythm
Rate is regular and fast 100-200
At high risk of deteriorating into fibrillation (cardiac arrest)
Shockable rhythm - defibrillators widely available
What is ventricular fibrillation?
Heart rate irregular and 250 bpm or above
Heart unable to generate an output
Shockable rhythm
What is ST elevation?
P waves visible and always followed by QRS
Rhythm is regular and rate is normal
ST segment elevated >2mm above the isoelectric line
Caused by infarction - tissue death caused by hypoperfusion
What is ST depression?
P waves visible and always followed by QRS
Rhythm is regular and rate is normal
ST segment is depressed >2mm below the isoelectric line
Caused by myocardial ischaemia (coronary insufficiency)
