ECG

Front

Electrocardiogram Noun

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[uh-lek-troh-kahr-dee-uh-gram]

Back

Electrocardiogram

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A noninvasive test that records the heart's electrical activity to help diagnose various common heart problems and conditions.

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Example: This image shows three different advanced methods for calculating a person's heart rate in beats per minute (bpm) by analyzing the waves on an electrocardiogram strip.

Front

SA node Noun

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[es-ey nohd]

Back

SA node

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The heart's natural pacemaker, which spontaneously generates electrical impulses to establish the normal heart rate and rhythm.

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Example: This diagram shows the SA node, the heart's natural pacemaker, located in the upper right chamber, initiating the electrical signal for a heartbeat.

Front

Purkinje fibers Noun

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[per-kin-jee fahy-berz]

Back

Purkinje fibers

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Specialized fibers that transmit electrical impulses to the ventricular muscle cells, causing them to contract and pump blood.

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Example: This diagram shows the heart's electrical system, where Purkinje fibers are the final pathways that make the ventricles contract and pump blood.

Front

Depolarization Noun

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[dee-poh-ler-uh-zey-shuhn]

Back

Depolarization

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The electrical event that triggers the contraction phase, known as systole, of the heart muscle cells.

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Example: This graph shows depolarization as the rapid increase in a cell's electrical voltage, which is the fundamental electrical event that creates a heartbeat.

Front

Repolarization Noun

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[ree-poh-ler-uh-zey-shuhn]

Back

Repolarization

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The electrical event that leads to the relaxation phase, known as diastole, of the heart muscle cells.

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Example: This graph shows how a heart cell's electrical charge changes. Repolarization is the phase where the charge returns to its resting level after a peak.

Front

Systole Noun

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[sis-tuh-lee]

Back

Systole

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The phase of the cardiac cycle during which the heart muscle contracts to pump blood out of the chambers.

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Example: This image shows the heart during systole, the pumping phase, where the ventricles contract to push blood out to the body and lungs.

Front

Diastole Noun

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[dahy-as-tuh-lee]

Back

Diastole

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The phase of the cardiac cycle when the heart muscle relaxes, allowing the chambers to fill with blood.

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Example: This diagram shows diastole, the phase where the heart muscle relaxes and its chambers (ventricles) fill with blood before the next contraction.

Front

P-Wave Noun

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[pee weyv]

Back

P-Wave

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The initial wave on an ECG tracing that represents the electrical depolarization and subsequent contraction of the atria.

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Example: This diagram shows a heartbeat's electrical signal (ECG). The first bump, labeled 'P', is the P-wave, representing the signal that starts the heartbeat.

Front

QRS Complex Noun

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[kyoo-ahr-es kom-pleks]

Back

QRS Complex

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A series of waves on an ECG that represents the rapid electrical depolarization and contraction of the ventricles.

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Example: This diagram shows a normal heartbeat on an ECG. The tall, sharp spike (QRS complex) represents the powerful electrical pulse that makes the ventricles pump blood.

Front

T-Wave Noun

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[tee weyv]

Back

T-Wave

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The wave on an ECG tracing that represents the electrical repolarization, or relaxation, of the ventricles after contraction.

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Example: This diagram shows a standard ECG waveform, where the T-wave, highlighted in red, represents the electrical recovery of the heart's lower chambers (ventricles).