Heart Anatomy & Electrocardiogram (ECG/EKG)

Heart (what, does what & structures)

• 4-chambered muscular organ

• to pump blood throughout body

• right & left atria, right & left ventricles & interventricular septum

Heart valves (function, names & locations)

to prevent blood backflow

1. tricuspid (between right atrium & ventricle)

2. pulmonary semi-lunar (between right ventricle & pulmonary trunk/artery)

3. bicuspid/mitral (between left atrium & ventricle)

4. aortic semi-lunar (between left ventricle & aorta)

1. superior vena cava (SVC)

2. right atrium

3. tricuspid valve

4. right ventricle

5. papillary muscles

6. aorta (arch)

7. pulmonary trunk (artery)

8. left atrium

9. bicuspid (mitral) valve

10. interventricular septum

2 phases of the heartbeat

Systole: contraction of ❤, valves close & blood is pumped out

Diastole: relaxation of the ❤, valves open & blood enters ventricles

What triggers the heart to beat?

4 masses of conductive tissue with electrical impulses placed throughout the heart

1. sinoatrial node: pacemaker of the ❤; ORIGIN of heart beat (upper portion of right atrium)

2. atrioventricular node: starts venticular contraction (margin of the right atrium and ventricle)

3. Bundle of His: takes electrical signal from the AV node & sends to the bottom of the ❤

4. Purkinje (pur-KINGE-jee) fibers: carry electrical impulse to the muscle fibers; causing contraction (smaller nerve fibers branching from the bundle of His

ECG (electrocardiogram)

A transthoracic interpretation of the electrical activity of the heart over time, captured and externally recorded by skin eletrodes

How does an ECG work?

The ❤’s conduction system uses electrical current to stimulate contraction, and these weak electrical currents are detected on the skin surface by placing electrodes in specific areas

The more leads, the…

more & better data collected

3 leads → monitoring

4-5 leads → specific information

12 leads → the electrical conduction of the ❤ beat

Sine wave

demonstrates the electrical conduction of the heartbeat

P - SA node activated

QRS - AV node fires & travels through Bundle of His & out to the Purkinje fibers

T - SA & AV nodes reset to get ready to fire again

Waves

P wave - contraction (depolarization) of both atria

QRS complex - contraction of both ventricles (depolarization)

ST-T wave - ventricular relaxation (repolarization)

U wave - found between T&P waves (ORIGIN not clear but ~ represents “after depolarization” in ventricles

Intervals

PR interval - time from atrial contraction (P wave) to ventricular contraction (QRS complex)

QRS duration - duration of ventricular muscle contraction

QT interval - duration of ventricular contraction & relaxation

RR interval - duration of ventricular cardiac cycle (indicator of ventricular rate)

PP interval - duration of atrial cycle