Cardiac Graphs

Parts of the ECG Wave

The heart is stimulated electrically as it contracts.

P

Q

R

S

T

lub

dupp

The lub sound is the closing of the AV valves, while the dupp sound is the slamming shut of the semilunar valves.

We can remember that the P spike is the atrial depolarization, while the QRS complex depicts ventricular depolarization.

Pressure graphs

Some key terminology to remember: systole refers to when the chambers of the heart contract and thus pump blood, while diastole refers to the relaxation of the chambers that allows filling with blood.

Also, remember that these graphs are all plotted against the same time interval.

Aorta

We can follow the pressure changes in the aorta with the green curve.

dicrotic notch

80

pressure (mmHg)

40

Left atrium

We can follow the pressure changes in the left atrium with the magenta curve.

atrial systole

80

pressure (mmHg)

40

Left ventricle

We can follow the pressure changes in the left ventricle with the blue curve.

ventricular systole

80

pressure (mmHg)

40

Volume graph

As the heart contracts and relaxes, the volume of the chambers of the heart change. Here, we analyze the volume of the ventricles.

1

2

end systolic volume

end diastolic volume

stroke volume

ventricular volume (mL)

120

30

1. Isovolumetric contraction
2. Isovolumetric relaxation

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