ECG Fundamentals: Speed, Rate & Rhythm

Study Notes

ECG Basics

Sinoatrial node (Puran) initiates the heart's electrical impulses; cycle duration is 0.20 seconds.
Horizontal length of a large box on ECG paper equals 0.20 seconds; useful for timing.
Vertical height of QRS complex on a large box measures 5mm, indicating the amplitude of ventricular depolarization.

Waves and Segments

P wave indicates atrial depolarization, a crucial phase for heart contraction.
QRS complex represents ventricular depolarization, a key component of heart activity.
ST segment reflects the period when the ventricles are contracting and emptying.
T wave signifies ventricular repolarization, restoring the resting state.
U wave may represent Purkinje fiber repolarization, appearing occasionally after the T wave.

Heart Rate

Normal heart rate ranges from 60 to 100 beats per minute (BPM).
Bradycardia occurs when the heart rate drops below 60 BPM.
Tachycardia is identified when the heart rate exceeds 100 BPM.
To estimate heart rate:
- Count the number of QRS complexes over 6 seconds and multiply by 10.
- Alternatively, use the formula: Rate = 60 / (R-R interval time).
- Another method: Rate = 300 / (number of large boxes between R-R intervals).

Rhythm Assessment

Sinus rhythm: Waves occur in consistent positions.
Sinus Tachycardia: Heart rate exceeds 100 BPM, with regular P waves preceding each QRS complex.
Sinus Bradycardia: Heart rate is at or below 60 BPM, with regular rhythm.
Sinus Arrhythmia: Irregular heart pattern observed despite normal structure.

Other Rhythms

Atrial Fibrillation: Irregular and often rapid heart rate originating from chaotic electrical signals.
Atrial Flutter: Regular but rapid heart rhythm due to reentrant circuits in the atria.
Premature Atrial Contraction (PAC): Extra heartbeats originating in the atria.
Premature Ventricular Contraction (PVC): Extra heartbeats originating in the ventricles.

Intervals and Durations

PR Interval: Normal duration is between 0.12 to 0.20 seconds, reflecting atrial depolarization and conduction through the AV node.
QRS Duration: Ranges from 0.07 to 0.10 seconds; indicates the time taken for ventricular depolarization.
QT Interval is critical for assessing the heart's electrical recovery:
- Normal duration is ≤0.44 seconds.
- Males: ≤0.45-0.46 seconds.
- Females: ≤0.47-0.48 seconds.

Description

Test your knowledge on the concepts of ECG, including speed, rate, and rhythm. This quiz covers essential components like the P wave, QRS complex, and intervals crucial for understanding cardiac depolarization and repolarization. Ideal for students and professionals in the medical field.