Question

The QRS complex in a standard ECG represents:

• A. Depolarisation of auricles
• B. Depolarisation of ventricles
• C. Repolarisation of auricles
• D. Repolarisation of ventricles

Answer 1

Answer:

B. Depolarisation of ventricles

• The QRS complex on an electrocardiogram (ECG) is a crucial component that signifies a significant event in the cardiac cycle.
• It specifically represents the depolarization of the ventricles, which are the heart's lower chambers responsible for pumping blood to the rest of the body.
• Ventricular depolarization is the electrical event that leads to the contraction of the ventricles, a process known as ventricular systole.
• The P wave on an ECG precedes the QRS complex and represents the depolarization of the atria (upper chambers of the heart).
• The T wave, which follows the QRS complex, represents the repolarization of the ventricles, where the heart muscle cells recover electrically.
• Abnormalities in the QRS complex, such as widening or increased amplitude, can indicate various cardiac conditions, including ventricular hypertrophy, myocardial infarction, or bundle branch blocks.
• In competitive exams, understanding the sequence and meaning of ECG waveforms (P wave, QRS complex, T wave) is vital for diagnosing and interpreting cardiac abnormalities.
• The duration of the QRS complex is typically between 0.06 to 0.10 seconds. A QRS duration longer than 0.12 seconds often suggests a conduction delay within the ventricles.
• The electrical activity captured by the QRS complex is the sum of the electrical potential of all ventricular cells, making it the largest and most prominent deflection on a standard ECG.