1. EFFECT OF ELECTROLYTES
ON CARDIAC RHYTHM
Prepared by: Ahmad Thanin

2. OBJECTIVES:
By the end of session learners will be able to:
• Define Electrolytes.
• Discuss the function of electrolytes
• Describe the relationship of electrolyte with
heart
• List down common electrolytes
responsible for cardiac function
• Explain the effect of electrolytes on heart
• Interpret the ECG features of different
electrolyte imbalances
• Summarize the main key points of the
session

3. What are Electrolytes?
Chemically, electrolytes are substances that
become ions in solution and acquire the
capacity to conduct electricity. Electrolytes
are present in the human body, and the
balance of the electrolytes in our bodies is
essential for normal function of our cells and
our organs.

4. FUNCTIONS:

5. Electrolytes and Heart:
• The normal state of cardiac cell membrane polarization
is dependent upon the maintenance of a normal ionic
balance across the membranes

6. Common Electrolytes responsible for
cardiac arrhythmias
• Potassium
• Magnesium
• Calcium

7. HYPERKALEMIA
Background
•Potassium is vital for regulating the normal electrical
activity of the heart.
•Increased extracellular potassium reduces myocardial
excitability, with depression of both pacemaking and
conducting tissues.
•Progressively worsening hyperkalemia leads to
suppression of impulse generation by the SA node and
reduced conduction by the AV node and His-Purkinje
system, resulting in bradycardia and conduction blocks and
ultimately cardiac arrest.

8. ECG features of Hyperkalemia:
• Rhythm: Atrial and ventricular rhythms are regular
• Rate: Atrial and ventricular rates are within normal limits
• P Wave: Mild-low amplitude, moderate-wide flattened,
severe-indiscernible
• PR interval: Normal or prolonged; unmeasureable if P
wave cant be detected
• QRS complex: Widened because ventricular
depolarization takes longer
• QT interval: Shortened
• ST segment: May be elevated in severe hyperkalemia
• T wave: Tall, Peaked.

9. Peaked T waves in Hyperkalemia
Prolonged PR segment in Hyperkalemia

10. Broad P waves and QRS complexes
Loss of P waves

11. Bradycardia

12. HYPOKALEMIA
Background
•Potassium is vital for regulating the normal electrical
activity of the heart
•Decreased extracellular potassium causes myocardial
hyper excitability with the potential to develop re-entrant
arrhythmias

13. ECG features of Hypokalemia:
• Rhythm: : Atrial and ventricular rhythms are regular
• Rate: Atrial and ventricular rates are within normal limits
• P Wave: Usually normal size and configuration
• PR interval: May be prolonged
• QRS complex: Within normal limits or possibly widened;
prolonged in hypokalemia
• QT interval: Usually indiscernible as T wave flattens
• ST segment: Depressed
• T wave: Amplitude is decreased. Inverted T wave U
wave may appear.

14. T inversion and prominent U wave in Hypokalemia
Long QT interval in Hypokalemia

15. HYPOCALCEMIA
Background
•Calcium is important in cardiac function; it exerts a positive
inotropic effect on heart
•Decreased calcium levels may cause decreased
myocardial contraction.

16. ECG features of Hypocalcaemia:
• Rhythm: Atrial and ventricular rhythms are regular
• Rate: Atrial and ventricular rates are within normal limits
• P Wave: Normal size and configuration
• PR interval: Within normal limits
• QRS complex: Within normal limits
• QT interval: Prolonged
• ST segment: Prolonged
• T wave: Normal size and configuration, may be flattened

17. Prolong QT interval in Hypocalcaemia

18. HYPERCALCAEMIA
Background
•Calcium is important in cardiac function; it exerts a positive
inotropic effect on heart
•Increased calcium levels may block the conduction
pathways of electrical impulse.

19. ECG features of Hypercalcemia:
• Rhythm: Atrial and ventricular rhythms are regular
• Rate: Atrial and ventricular rates are within normal limits,
bradycardia or heart block may occur
• P Wave: Normal size and configuration
• PR interval: May be prolonged.
• QRS complex: Within normal limits, may be prolonged
• QT interval: Prolonged
• ST segment: Normal
• T wave: Normal size and configuration; may be
depressed.

20. Shortened QT interval in Hypercalcemia

21. HYPOMAGMESAEMIA
Background
•Magnesium is required to support the heart muscle’s
normal contraction-relaxation actions.
•Decreased magnesium levels may cause irregular
contraction of ventricles leading to arrhythmias.

22. ECG features of Hypomagnesaemia:
• Rhythm: Irregular ventricular rhythm
• Rate: Atrial and ventricular rates may be regular
• P Wave: May be normal
• PR interval: Normal
• QRS complex: Normal
• QT interval: Normal
• ST segment: Depressed
• T wave: Tall T waves

23. Tall T waves in Hypomagnesaemia
Torsades de pointes

24. Depressed ST segment in Hypomagnesaemia

25. HYPERMAGMESAEMIA
Background
•Magnesium is required to support the heart muscle’s
normal contraction-relaxation actions.
•Increased magnesium levels may cause delayed
conduction of electrical impulse.

26. ECG features of Hypermagnesemia
• Rhythm: Atrial or ventricular rhythm may be regular
• Rate: Atrial and ventricular rates may be regular
• P Wave: May be normal
• PR interval: prolonged
• QRS complex: Widened
• QT interval: Normal
• ST segment: Normal
• T wave: Normal

27. Prolonged PR interval in Hypermagnesemia
Wide QRS complex in Hypermagnesemia

28. In a nut
shell
Hypocalcaemia- Prolonged ST and QT
intervals
Hyperkalemia- shortened ST segment
- widened T wave
Hypokalemia- ST depression
- shallow, flat, inverted T wave
- Prominent U wave
Hyperkalemia- Tall, peaked T waves
- Flat P waves
- widened QRS complex
- Prolonged PR interval
Hypomagnesaemia- Tall T waves
- Depressed ST segment
Hypermagnesemia- Prolonged PR interval
- widened QRS complexes

29. Treatment:
• Hyperkalemia Cocktail
• Hypokalemia Potassium replacement
• Hypercalcemia Magnesium
• Hypocalcemia Calcium replacement
• Hypermagnesemia Calcium
replacement
• Hypomagnesaemia Mg replacement