Functions of The ECG Machines

Q-T interval

(Less than .40) Count the number of small boxes from Q-wave to the end of the T-wave and multiply by .04. A Q-T grater than .40 indicates Hypertrophy or Cardiomegaly.

Absent

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C. P-wave configurations

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F. T-wave

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Interpretations

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Inverted or Negative

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Measure all PR intervals on the EKG

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Notched

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Peaked

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QRS complex

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Unique Quantities of the Heart

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QRS complex (Intervals)

.04- .12 Count the number of small boxes from the Q to the S and multiply by .04. QRS complex determines if a Bundle Branch Block is present.

PR intervals

.12 through .20 count the number of small boxes from the beginning of the P wave to the beginning of the QRS wave and multiply the number by .04. The PR interval is used to determine if a first, second or third AV block is present.

Speed

25 mm per second is the most commonly used, use 50 mm per second if there is a rapid heartbeat.

Normal is

60 to 100 bpm

Tachycardia

Above 100 bpm

G. U wave

Appears in Hypokalemia (low potassium)

LCD Display

Area where you can view the patients information that you have entered and the ECG computer is displayed.

A. Rates

Atrial and ventricular

Bradycardia

Below 60 bpm

Artifact Filter

Between 40 Hz and 150 Hz is the normal setting. 40 Hz is normally used to reduce artifacts or abnormal marks on the ECG tracing due to muscle tremors or patient movements.

Ventricular Rate

Count the number of small boxes from a R-wave and divided.

Atrial Rate

Count the number of small boxes from the beginning of a P-wave to the beginning of the next P-wave and divide 1500 by that number.

Stylus

Creates the tracing on the ECG paper, which is treated to the heated stylus. When the heat is truned up the stylus will produce a darker tracing, and a lighter tracing when it is truned down.

E. St Segment

Determines Ischemia

Heart Rate Limits

ECG machine can be set to interpret "Bradycardia" and "Tachycardia" An alarm will sounds if the heart rate goes above or below the number set.

B. Rhythm

Either regular or irregular ( use plain paper and measures points of the R-wave)

Input

Electrode placed on the skin direct the impulses to the ECG Machine

Standardization

Ensures that the machine is recording correctly. 10 mms is the normal setting.

S-Wave

First negative deflection after the R-wave.

R-wave

First positive deflection in the QRS complex.

Output display

If the printed ECG tracing.

2. Negative

Injury

There are three basic functions

Input, signal processing, and output display.

Contractility

Is the ability of the cardiac cells to shorten in response to an electrical stimulus.

Conductivity

Is the ability of the heart cells to receive and transmit an electrical impluse.

Excitability

Is the ability of the heart muscle cells to respond to an impluse or stimulus.

Automaticity

Is the ability of the heart to initiate an electrical impulse without being stimulated by another or independent source. Heart muscle tissue can initiate it's own electrical impulse.

P-wave

Is the first positive deflection, usually upright and rounded.

Lead Selector

Is used to run each lead individually or separately.

D. Intervals: P-R, QRS, and Q-T

Multiple by .04

Q-wave

Negative deflection before the R-wave.

1. Positive

Normal

Signal processing

Occurs inside the ECG machine. And amplifies the electrical impulses and converts it into a mechanical action on the display. A complex collection of Transistors, Resistors and Circuitry amplify and prepare the signal for transfer to the output display.

Irregular Rhythm

Only if the Rhythm is more than 3 boxes off. An irregular Rhythm is Arrhythmia or Dysrhythmia.

Second degree AV block

PRI will vary from one measurement to the next, PRI will be progressively longer with each subsequent conducted P-wave until the QRS wave is dropped. The PRI will be short, then the cycle will begin again (MOBITZ 1.) The rhythm will be irregular.

T-wave

Positive deflection following the QRS complex.

Deflections on an ECG

Positive deflections are pointed upward and negative d eflections are pointed downwards

First degree AV block

Pri is greater than .20 remains consistent and the rhythm is regular.

2. Left Bundle Branch Block (LBBB)

QRS is grater than .12 and negative.

1. Right Blundle Branch (RBBB)

QRS is grater than .12 and positive.

Gain

Regulates the output or height of the ECG wave form. 10 Mm /m is the normal setting.

U-wave

Small positive deflection following the T-wave.

Controls

Speed, gain an artifact filter are the three most important controls.

2. Elevated

St Segment is above the isoelectric line. (Ischemia)

3. Depressed

St Segment is below the isoelectric line. (Ischemia)

1. Normal

St Segment is flat

Third Degree Av Block

The PRI will vary from one measurement to the next. PRI will be long (more then .20) followed by a short PRI. The atrial rate will be normal (60-100 bmp) but the ventricular rate will be between 20- 40 bpm. There will be more P-wave than QRS complexes.

Normal

Upright and rounded.