EKG interpretation

Question 1

SA node

Answer 1

Pacemaker of the heart

Automaticity- regular waves of depolarization, multidirectional stimulates atrial contraction, P wave

Question 2

AV node

Answer 2

sole conduction pathway from atria to ventricles
Mitral and tricuspid valves are electrical insulation

Depolarization thru AV node is slow, Pause (blood passes thru AV valves, delap after the p wave)

Question 3

Ventricular conduction system

Answer 3

initiated in the His bundle and quickly moves into bundle branches and purkinje fibers

Rapidly depolarizes ventricles

Question 4

Naming QRS

Answer 4

Q: 1st downward deflection
R: 1st upward deflection
S: ANY downward deflection after an upward deflection

Question 5

Ventricular repolarization

Answer 5

plateau phase ST segment
Rapid phase phase : T wave

Ventricular contraction persists thru complete repolarization: QT interval

Question 6

EKG leads

Answer 6

Limb leads: AVL AVR and AVF (positives)

Augmented limb leads: 1 (at positive across chest to Larm), 2 (at positive Foot from r arm), 3 (at positive foot from left arm)

Precordial leads: cross section from center of body (V1 to left side V6)

Question 7

Rate

Answer 7

Normal resting heart at rest 60-100 bpm (due to SA node automacity)

Bradycardia is <60 bpm (parasympathetic excess, young athletes vagal maneuvers)
Tachychardia is >100 bpm (sympathetic stimulation of SA node, exersice, stress)

If SA node fails, another pacemaker takes over (Atria-60-80 bpm, Junctional AV node- 40-60 bpm, Ventricular purkinje fibers-20-40bpm)

Overdrive suppression: automaticity focus (SA node usually) will suppress all slower foci, SA node»>Atrial focus»>Junctional»>Ventricular foci

Question 8

Rate on EKGs

Answer 8

Choose a QRS (ideally on a bold line), then use the 300 rule (300/# of big boxes between QRSs), box countdown (300 150 100 etc)

Irregular: recognize potential for inaccuracies and investigate further, calculate range and mean

Question 9

Rhythm

Answer 9

Is it normal sinus rhythm (coming from the sinus node, regular, constant cycles of equal length, best visualization in lead 2 (must be a p wave before every QRS, is there a QRS after every P

Sinus arrhythmia- common in young healthy, normal variation of HR with respiration (inspiration–> increased HR, decreased vagal tone–> sympathetic stim SA node), (exhalation–>decreased HR, increased vagal tone, parasympathetic inhib of SA node)

Question 10

Axis

Answer 10

look at QRS leads 1 and AVF, sometimes lead 2

Lead 1 should be positive and lead AVF should be positive

If 1 is negative but AVF is positive: Righat axis deviation (RAD)

if both neg: FAR RAD

If Lead 1 is positive but lead AVF is negative (next look at lead 2, + normal, - LAD)

Question 11

PR interval

Answer 11

Atrial depolarization and conduction into av node
Normal is .12 ro .2 s (3 to 5 little boxes)

Short: Wolf parkinson white
Prolonged: PR interval is 1st degree AV block, asymptomatic

Question 12

QRS interval

Answer 12

Ventricular depolarization

Normal

Question 13

QT interval

Answer 13

initiation of ventricular depolarization thru complete repolarization

Normal (

Question 14

St segment and T wave

Answer 14

ST segment: Plateau phase of ventricular repolarization, baseline with PR interval,

T wave: rapid phase of ventricular repolarization T waves are typically upright, Wave of repolarization traveling away from electrodes