lecture-9-ECG recognition

Question 1

ATRIAL premature beats

Answer 1

P wave morphology Different shapes in same lead

Question 2

Supraventricular Premature Beats (atrial premeture beat?)

Answer 2

Can precede other supraventricular arrhythmias - In atrial premature beat (APB), atrial depolarization occurs before next sinus p wave, termed p’ wave - QRS complex of APB preceded by P wave that looks different from other P waves on strip (different morphology or PR interval); PR interval may be longer or short; P wave could be obscured by T wave - After APB, a slight pause occurs before the normal sinus beat resumes (contrasted to the fully compensatory pause often seen after ventricular premature beats) - QRS complex will be narrow (if no additional defects are present) - May reach junction during refractory period and be blocked

Question 3

Junctional Rhythms

Answer 3

• Retrograde P wave (reversed atrial depolarization vector), can be prominent in lead aVR (positive P wave) and lead II (negative P wave) - Ventricles and atria receive depolarization impulse simultaneously: P wave can occur just before QRS (with a short PR interval), inside QRS complex (P wave buried), or just after QRS. If after QRS, “pseudo-S” waves (in leads II, III, aVF) or “pseudo-R” waves (in leads V1 and aVR) can be seen. - Junctional “escape” rhythm can follow sinus arrest - QRS complex will be narrow (if no additional defects are present)

Question 4

JUNCTIONAL premature beat

Answer 4

absent of inverted P wave in lead II

Question 5

Atrial Premature beat

Answer 5

Question 6

Multifocal Atrial Tachycardia

Answer 6

• multiple sites of atrial stimulation (ectopic foci)
• 3 or more consecutive non-sinus P waves with different shapes
• PR intervals vary
• Ventricular rate is irregular (some beats get through, some do not) and rapid.
• MAT can compromise filling and clinical symptoms of reduced perfusion (dizziness, shortness of breath) may be seen

Question 7

Atrial Fibrillation

Answer 7

Fibrillation (f) waves vary in shape and polarity (come from multiple sites throughout atrial muscle)
- Irregularly irregular: variable f-f intervals and irregular ventricular (QRS) response
- Differentiate from atrial flutter
o Identical flutter (F) waves that time out regularly
o Constant QRS response (e.g. 2 F:1 QRS or 4 F:1 QRS)
- Can increase risk for thrombo-embolus, due to uncoordinated movement of blood (especially stroke) and heart failure, due to short-term decrease in cardiac output and long-term mechanisms activated to compensate for reduced cardiac output
- Control rate, by pharmaceuticals or pacemaker; control rhythm, by ablation or cardioversion

Question 8

First Degree AV Block

Answer 8

• P wave (usually sinus) followed by QRS complex with a PR interval > 200 msec
• PR interval is uniformly prolonged; all PR intervals are similar
• The number of P waves equals the number of QRS complexes

Question 9

First Degree AV Block:

Answer 9