ECG Leads and Basic Interpretation Quiz

What is the purpose of an Electrocardiogram (ECG)?

• Assess lung function

• Monitor oxygen levels

• Record cardiac conduction

• Measure blood pressure

Answer explanation

The purpose of an Electrocardiogram (ECG) is to record cardiac conduction, not to assess lung function, monitor oxygen levels, or measure blood pressure.

How is the Q-T interval defined in an ECG recording?

• From start of atrial depolarization to start of QRS

• Time required for ventricles to undergo a single cycle of depolarization and repolarization

• Measured from end of P-R to end of T

• From the end of one wave to the start of another

Answer explanation

Measured from end of P-R to end of T

What does the (5 x 5) mm square on ECG graph paper represent?

• 0.04 seconds

• 0.1 mV

• 0.2 seconds

• 0.5 mV

Answer explanation

The (5 x 5) mm square on ECG graph paper represents 0.2 seconds.

How can heart rate be calculated using Method 1 in ECG analysis?

• Count the number of small (0.04-second) time boxes between two successive R waves and divide by 300

• Count the number of cardiac cycles that occur every 6 seconds and multiply by 10

• Count the number of large (0.2-second) time boxes between two successive R waves and divide by 1500

• Count the number of large (0.2-second) time boxes between two successive R waves and divide by 300

Answer explanation

Count the number of small (0.04-second) time boxes between two successive R waves and divide by 300

What defines a sinus rhythm in ECG analysis?

• QRS up in I and down in aVF

• Variable PR interval

• P wave is negative in lead I, II

• Each P wave is followed by QRS

Answer explanation

Each P wave is followed by QRS, which defines a sinus rhythm in ECG analysis.

What is the significance of the P wave in an ECG recording?

• Represents atrial depolarization

• Indicates ventricular repolarization

• Reflects ventricular depolarization

• Measures atrial repolarization

Answer explanation

The P wave in an ECG recording represents atrial depolarization, making it the correct choice.

How is the ST segment interpreted in ECG analysis?

• Represents ventricular depolarization

• Indicates atrial repolarization

• Reflects ventricular repolarization

• Measures atrial depolarization

Answer explanation

The ST segment in ECG analysis reflects ventricular repolarization, not atrial depolarization or other cardiac events.

What does the T wave signify in an ECG reading?

• Represents atrial repolarization

• Indicates ventricular depolarization

• Reflects atrial depolarization

• Measures ventricular repolarization

Answer explanation

The T wave in an ECG reading measures ventricular repolarization, indicating the recovery phase of the ventricles.