Understanding Heart Rhythms: A Paramedic's Guide to ECG Analysis

Paramedics must rapidly identify key cardiac rhythms on ECG. Here are the essential patterns:

1. Sinus Rhythm (Normal)

• Rate: 60–100 bpm
• Regular rhythm
• P wave before each QRS; upright in lead II
• PR interval 0.12–0.20 sec; QRS <0.12 sec

2. Atrial Fibrillation (AFib)

• Irregularly irregular rhythm
• No distinct P waves; fibrillatory baseline
• Rate: often rapid (100–175 bpm) but can be controlled
• Narrow QRS (unless bundle branch block)

3. Atrial Flutter

• Regular atrial rate ~250–350 bpm
• Sawtooth flutter waves (best in II, III, aVF, V1)
• Ventricular response often 2:1 (~150 bpm) or variable

4. Ventricular Tachycardia (VTach)

• Wide QRS (>0.12 sec), bizarre morphology
• Rate: 100–250 bpm, usually regular
• AV dissociation (P waves independent of QRS)
• Treat as pulseless VT if no pulse—shock immediately.

5. Ventricular Fibrillation (VFib)

• Chaotic, disorganized waveform; no identifiable QRS or P waves
• No effective cardiac output
• Immediate defibrillation + CPR.

6. Asystole

• Flat line (no electrical activity)
• Confirm in 2 leads; check gain/leads
• CPR + epinephrine; do NOT shock.

7. Pulseless Electrical Activity (PEA)

• Organized electrical activity but no palpable pulse
• Search for reversible causes (H's & T's: Hypovolemia, Hypoxia, Hydrogen ion, Hypo/hyperkalemia, Hypothermia, Tension pneumothorax, Tamponade, Toxins, Thrombosis)

8. Bradycardia (<60 bpm)

Symptomatic? → Atropine, pacing, treat cause (meds, MI, hypoxia).

9. Tachycardia (>100 bpm)

Narrow vs. wide QRS determines algorithm. Stable vs. unstable dictates urgency.

Key: Always correlate rhythm with clinical presentation. Treat the patient, not the monitor.