Page 146 - Physiology and Pathophysiology MNU 2024-2025 نظرى

Clinical pharmacy 2024/2025 Level 2 Pharm D Physiology and Pathophysiology (MD303)
Electrocardiogram Measurement of electrical activity of the heart
Wave Meaning
✓ Depolarization of the atria (contraction)
P-Wave
 Duration of P wave ➔ correlate with conduction time through the atria

QRS complex Depolarization of the ventricles (contraction)

T wave Repolarization of the ventricles (relaxation)
repolarization of atria not appear, as it occur during QRS

Interpretation of ECG interval

 Time from initial depolarization of atria ➔ to initial depolarization of ventricles [0.2 sec] ➔
PR interval  Inversely correlates with Conduction velocity through AV node.
 ↑ PR interval ➔ ↓ conduction velocity through AV node [heart block]
☺ The time from first ventricular depolarization [contraction] to last ventricular repolarization [complete relaxation] (beginning
QT Interval  end).
 QT interval includes  QRS complex & ST segment & T wave.

ST segment ☺ The Period when the ventricles are depolarized (Contraction).
Large PR Problem in conduction (like heart Block).
Large QT long QT syndrome " blockade or low number of K channel ➔ need more time to occur"

Calculation OF Heart Rate from ECG

Calculation of Heart Heart rate (beat/min)
rate from ECG

Heart rate is the number = 1/cycle length x 60
of QRS complexes (or R Cycle length ➔ is R-R interval (0.8 sec)
waves) per minute.
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