33.4b Electrocardiogram

electrocardiogram (ECG)

The (?) is a graphic record of the heart’s electrical activity.

heart’s pumping ability

However, it tells you nothing about the (?) , which you must evaluate by taking the pulse and blood pressure.

Willem Einthoven

The electrocardiogram was invented by the Dutch physiologist Dr. (?) in 1903.

elektrokardiograaf

The device was first described in Dutch and referred to as an (?), and thus the abbreviation EKG was applied.

EKG

The abbreviation (?) is often interchanged with the English abbreviation ECG.

P, Q, R, S, and T

Interestingly, Einthoven chose the letters (?), (?), (?), (?), and (?) to describe points along the ECG waveform simply because they were in the middle of the alphabet and would not be confused with mathematic variables and similar commonly used letters.

giant conductor of electricity

The body acts as a (?) , and the heart is its largest generator of electrical energy.

Electrodes

Electrodes on the skin can detect the total electrical activity within the heart at any given time.

very low voltage

The electrical impulses on the surface of the skin have a (?).

ECG machine

The (?) amplifies these impulses and records them over time on ECG graph paper or a monitor.

upward deflections, downward deflections

Positive impulses appear as (?) on the paper and negative impulses appear as (?).

isoelectric line

The absence of any electrical impulse produces an (?), which is flat.

Artifacts

(?) are deflections on the ECG produced by factors other than the heart’s electrical activity.

muscle tremors, shivering, patient movement, loose electrodes, 60-hertz interference, machine malfunction

Common causes of artifacts include: (?), (?), (?), (?), (?), and (?).

free of artifacts

It is important for ECGs to be (?).

eliminate it

When an artifact is present, you must first try to (?) before recording the ECG.

Loose electrodes

(?) should be replaced.

diaphoretic

Occasionally, patients can be quite (?), thus preventing the electrodes from adhering well to the skin.

wipe the skin and apply tincture of benzoin

In these cases, you should (?) before applying the electrode.

voltage change

You can obtain many views of the heart’s electrical activity by monitoring the (?) through electrodes placed at various places on the body surface.

lead

Each pair of electrodes is a (?).

12 leads

In hospitals, (?) are normally used.

3 leads

As a rule, most EMS systems use only (?) in the field.

single lead

In fact, a (?) is adequate for detecting life-threatening arrhythmias.

12-lead ECGs

With the advent of fibrinolytic therapy and computer interpretation, however, (?) are commonly used in the field especially in rural EMS systems.

bipolar, augmented, and precordial

The three types of ECG leads are (?), (?), and (?).

Bipolar leads

(?), the type most frequently used, have one positive electrode and one negative electrode.

positive (upward) deflection

Any electrical impulse moving toward the positive electrode causes a (?) on the ECG paper.

negative (downward) deflection

Any electrical impulse moving toward the negative electrode causes a (?).

no electrical impulse, impulse is moving perpendicular to the lead

The absence of a positive or negative deflection means either that there is (?) or that the (?).

Leads I, II, and III

(?), commonly called limb leads, are bipolar.

most frequently used leads in the field

They are the (?).

Table 33-2

Table 33-2 lists their placement sites.

Einthoven’s triangle

These three bipolar leads form (?), named after the inventor of the ECG machine (Figure 33-17).

lead’s axis

The direction from the negative to the positive electrode is the (?).

different axis

Each lead shows a different axis of the heart.

0°

Lead I, at the top of Einthoven’s triangle, has an axis of (?).

60°

Lead II forms the right side of the triangle and has an axis of (?).

120°

Lead III forms the left side of the triangle and has an axis of (?).

three views

The bipolar leads provide only (?) of the heart.

Augmented leads

(?), or unipolar leads provide additional views that are sometimes useful.

same electrodes

Although these leads evaluate different axes than bipolar leads do, they use the (?).

electronically combining the negative electrodes of two of the bipolar leads

They do this by (?) to obtain an axis.

aVR, aVL, and aVF

These augmented leads are designated (?).

a

The letter (?) indicates that the lead is augmented.

V

The letter (?) identifies it as a unipolar lead.

R, L, and F

The (?), (?), and (?) identify the extremity on which the lead is placed.

R = right arm, L = left arm, F = left foot

(?) .

six precordial leads (chest leads)

In addition, (?) can be placed across the surface of the chest to measure electrical cardiac activity on a horizontal axis.

left ventricle and septum

These leads help in viewing the (?).

V1 through V6

They are designated (?) with the letter V identifying them as unipolar leads.