,CHAPTER 1: Understanding Cardiac Dysrhythmias
What are Dysrhythmias?
Dysrhythmias (or arrhythmias) are abnormal rhythms of the heart caused by
disturbances in impulse formation or conduction. They can be harmless or life-
threatening. They can:
1. Reduce cardiac output
2. Cause hypotension, syncope, chest pain, or cardiac arrest
3. Range from benign to life-threatening
👉 Exam Focus:
1. Identify rhythm on ECG
2. Assess patient symptoms/ Hemodynamic impact on the patient
3. Act with correct interventions (drugs, defibrillation, pacing)
1.1 Basic ECG Components
P wave → Atrial Depolarization
PR interval (0.12–0.22s) → Conduction from Atria → Ventricles
QRS complex (<0.12s) → Ventricular Depolarization
ST segment → Early Repolarization
T wave → Ventricular Repolarization
ECG paper Key
Thin Lines: 1 mm intervals or 0.04
sec
Thick lines: 5 mm intervals or .2sec
1 thick lined box (5 small boxes) =
.20 sec or 5mm
5 thick lines boxes (25 small boxes)
= 1 second
10 mm = 1 Mv
Tick Marks on ECG paper rhythm
strip: 3 secs
Always check:
Normal Intervals Rate → Rhythm → P waves → QRS
width → Symptoms.
,Drills (Fill-in-the-Blank)
1. The QRS complex represents ____________________.
2. The P wave shows ____________________.
3. A prolonged PR interval indicates ____________________.
4. The normal heart rate range is ____________________.
5. The first step in interpreting an ECG is ____________________.
Mini Clinical Case Example
Patient: 56-year-old male, ECG shows rate 48 bpm, regular rhythm, P waves
upright before each QRS, asymptomatic.
Likely rhythm: Sinus bradycardia
Rhythm: Regular
Rate: 50bpm (norml range=60-100bpm)
P Waves: Upright and Regular
P-R Interval: 0.16 sec (normal range=0.12-0.20), one P wave for each QRS
QRS: 0.08 sec (normal range=0.04-0.12)
Management: Observe if asymptomatic.
If symptomatic, give Atropine 0.5mg IV. Or pacing
, NCLEX/Relias-Style Questions (30)
Section A: General ECG Knowledge
Q1. Which part of the ECG represents atrial depolarization?
A. P wave
B. PR interval
C. QRS complex
D. T wave
✅ Answer: A. P wave
Q2. The normal PR interval is:
A. 0.04–0.10s
B. 0.12–0.20s
C. 0.20–0.30s
D. 0.30–0.40s
✅ Answer: B. 0.12–0.20s
Q3. A widened QRS (>0.12s) usually indicates:
A. Atrial problem
B. Ventricular conduction delay
C. Normal finding
D. SA node block
✅ Answer: B. Ventricular conduction delay
Q4. Which electrolyte abnormality can cause peaked T waves?
A. Hypokalemia
B. Hyperkalemia
C. Hypocalcemia
What are Dysrhythmias?
Dysrhythmias (or arrhythmias) are abnormal rhythms of the heart caused by
disturbances in impulse formation or conduction. They can be harmless or life-
threatening. They can:
1. Reduce cardiac output
2. Cause hypotension, syncope, chest pain, or cardiac arrest
3. Range from benign to life-threatening
👉 Exam Focus:
1. Identify rhythm on ECG
2. Assess patient symptoms/ Hemodynamic impact on the patient
3. Act with correct interventions (drugs, defibrillation, pacing)
1.1 Basic ECG Components
P wave → Atrial Depolarization
PR interval (0.12–0.22s) → Conduction from Atria → Ventricles
QRS complex (<0.12s) → Ventricular Depolarization
ST segment → Early Repolarization
T wave → Ventricular Repolarization
ECG paper Key
Thin Lines: 1 mm intervals or 0.04
sec
Thick lines: 5 mm intervals or .2sec
1 thick lined box (5 small boxes) =
.20 sec or 5mm
5 thick lines boxes (25 small boxes)
= 1 second
10 mm = 1 Mv
Tick Marks on ECG paper rhythm
strip: 3 secs
Always check:
Normal Intervals Rate → Rhythm → P waves → QRS
width → Symptoms.
,Drills (Fill-in-the-Blank)
1. The QRS complex represents ____________________.
2. The P wave shows ____________________.
3. A prolonged PR interval indicates ____________________.
4. The normal heart rate range is ____________________.
5. The first step in interpreting an ECG is ____________________.
Mini Clinical Case Example
Patient: 56-year-old male, ECG shows rate 48 bpm, regular rhythm, P waves
upright before each QRS, asymptomatic.
Likely rhythm: Sinus bradycardia
Rhythm: Regular
Rate: 50bpm (norml range=60-100bpm)
P Waves: Upright and Regular
P-R Interval: 0.16 sec (normal range=0.12-0.20), one P wave for each QRS
QRS: 0.08 sec (normal range=0.04-0.12)
Management: Observe if asymptomatic.
If symptomatic, give Atropine 0.5mg IV. Or pacing
, NCLEX/Relias-Style Questions (30)
Section A: General ECG Knowledge
Q1. Which part of the ECG represents atrial depolarization?
A. P wave
B. PR interval
C. QRS complex
D. T wave
✅ Answer: A. P wave
Q2. The normal PR interval is:
A. 0.04–0.10s
B. 0.12–0.20s
C. 0.20–0.30s
D. 0.30–0.40s
✅ Answer: B. 0.12–0.20s
Q3. A widened QRS (>0.12s) usually indicates:
A. Atrial problem
B. Ventricular conduction delay
C. Normal finding
D. SA node block
✅ Answer: B. Ventricular conduction delay
Q4. Which electrolyte abnormality can cause peaked T waves?
A. Hypokalemia
B. Hyperkalemia
C. Hypocalcemia
