Electrocardiogram Basics Quiz

An electrocardiogram (ECG) is a recording of the electrical activity of the heart, captured by placing electrodes on the skin.

The normal ECG is composed of three main waves: the P wave, the QRS complex, and the T wave. These waves represent different phases of the heart's electrical activity.

The P wave represents atrial depolarization, which is the electrical signal that causes the atria to contract.

The QRS complex represents ventricular depolarization, which is the electrical signal that causes the ventricles to contract.

The T wave represents ventricular repolarization, which is the electrical recovery of the ventricles following contraction.

Depolarization involves a change in electrical potential across a cell membrane, resulting in a positive charge inside the cell and a negative charge outside.

Repolarization is the return of a cell to its resting state, where the inside is negative and the outside is positive.

The ECG uses electrodes to detect the electrical potential differences generated by the heart. These differences are recorded as waveforms on the ECG graph.

The process of the muscle fiber membrane becoming more positive, initiated by the influx of sodium ions.

The process of the muscle fiber membrane returning to its resting negative state, following the influx of potassium ions.

The electrical signal representing depolarization and repolarization of the heart muscle, measured and displayed as a graph.

The electrical waveform in the EKG that represents the depolarization of the atria, the upper chambers of the heart.

The electrical waveform in the EKG that represents the depolarization of the ventricles, the lower chambers of the heart.

The electrical waveform in the EKG that represents the repolarization of the ventricles, as they return to their resting state.

The electrical signal representing the repolarization of the atria but is usually obscured by the QRS complex. It's not usually visible in the EKG

The electrical waveform in the EKG that specifically represents repolarization of the ventricles.

The repolarization of ventricular muscle takes about 0.15 seconds and is represented by the T wave in the electrocardiogram.

The T wave is a prolonged wave with a lower voltage than the QRS complex due to its longer duration.

Standard electrocardiogram calibration lines are arranged so that 10 small divisions equal 1 millivolt, with upward representing positivity and downward representing negativity.

A standard EKG is run at 25 mm/s, with each 25 mm representing 1 second. Each 5-mm segment represents 0.20 seconds.

The voltage of the QRS complex can reach 3 to 4 millivolts when the electrodes are placed directly over the ventricles.

The period between the start of the P wave and the start of the QRS complex is the P-Q interval, representing the time from atrial to ventricular excitation. It is normally about 0.16 seconds and often called the P-R interval.

The time between the beginning of the Q wave and the end of the T wave represents ventricular contraction, lasting around 0.35 seconds.

The heart rate can be determined by calculating the reciprocal of the time interval between two consecutive heartbeats.

The time interval between two heartbeats on an ECG, used to calculate heart rate. A 1 second interval indicates a heart rate of 60 beats per minute.

The normal time period between two QRS complexes in a healthy adult is 0.83 seconds, resulting in a heart rate of about 72 beats per minute.

The process of a heart muscle cell changing from a polarized state (resting) to a depolarized state (active), with negative charges moving to the outside and positive charges moving to the inside.

During most of the heart's depolarization, electrical current flows from the base of the heart towards the apex. However, just before depolarization is complete, the current briefly reverses direction, flowing from the apex to the base.

A bipolar lead in an EKG is a measurement taken between two electrodes placed on different parts of the body, typically on the limbs.

Different parts of the heart become electrically negative (depolarized) and positive (polarized) during a heartbeat, creating a potential difference that can be measured.

The body's fluids, including those surrounding the heart, conduct electricity, allowing electrical activity to spread throughout the heart.

Lead I is a bipolar lead measured between the right arm and the left arm.

The electrocardiograph records a positive reading in Lead I when the right arm is electronegative relative to the left arm.

The direction and pattern of electrical current flow through the heart, shaped by the depolarization and polarization of muscle fibers, generating measurable electrical signals.

The electrical impulse initiating a heartbeat first reaches the septum and then spreads to the ventricular walls, creating a specific pattern of negativity and positivity within the ventricle.

Lead II is a bipolar lead measured between the right arm and the left leg.

The average electrical current flow in the ventricles, with negative charges toward the base and positive charges towards the apex, contributing to the overall EKG signal.

The electrocardiograph records a positive reading in Lead II when the right arm is electronegative relative to the left leg.

In a typical EKG, the electrode positioned near the base of the heart will register a negative potential, while the electrode near the apex will register a positive potential.

Electrodes used in EKG are connected to the body and form a circuit that measures electrical activity of the heart, which is then represented as an electrocardiogram.

Lead III records the electrical potential difference between the left arm (negative) and the left leg (positive). It detects if the left arm is electrically negative relative to the left leg.

Chest leads (V1-V6) are placed on the anterior chest wall, each recording the electrical activity of the heart muscle directly beneath it.

Leads V1 and V2 are closer to the heart's base, where depolarization is mainly negative, leading to predominantly negative QRS recordings.

Leads V4, V5, and V6 are closer to the heart's apex, where depolarization is mainly positive, leading to predominantly positive QRS recordings.

Augmented unipolar limb leads (aVR, aVL, aVF) use two limbs as a reference point (negative) and one limb as the active electrode (positive).

aVR uses the right arm as the positive electrode, aVL uses the left arm, and aVF uses the left leg.

Leads V1 and V2 are placed on the right side of the chest near the sternum.

Leads V4, V5, and V6 are placed on the left side of the chest, moving down the chest toward the armpit.