The horizontal axis of the ECG strip represents time. Each small block0.04 secon
ID: 3480351 • Letter: T
Question
The horizontal axis of the ECG strip represents time. Each small block0.04 second, and five small blocks form a large block, which equals o.2 second (determined by multiplying o.o4 second of one small block by 5, the number of small blocks in a large block). Therefore, five large blocks 1 second (5 x o.2). When calculating a patient's heart rate, 1 6-second strip consisting of 30 large blocks is typically used. The vertical axis of the ECG strip measures amplitude in millimeters (mm) or electrical voltage (mV). Each small block-1 mm or 0.1 mV, each large block = 5 mm or 0.5 mV To determine the amplitude of a wave, segment, or interval, count the number of small blocks from the baseline to the highest or lowest point of the wave, segment, or interval. Things to remember when interpreting ECGs: pay special attention to the duration and configuration when evaluating a QRS complex (normal complex - follows PR interval, 5-30 mm high, o.o6-0.10 sec or half the PR interval), if no P wave appears with the QRS complex then the electrical impulse may have originated in the ventricles (indicating ventricular arrhythmia which often occurs in older adults), deep and wide Q waves may represent myocardial infarction (amplitude is 25% of R wave amplitude or greater than o.04 sec.), a notched R wave may signify bundle-branch block, a widened QRS complex (greater than o.12 sec.) may signify ventricular conduction delay, and a missing QRS complex may indicate AV block. Tall, peaked T waves indicate myocardial injury. After the T wave, a U wave can sometimes be observed, this represents the recovery period of the Purkinje fibers or ventricular conduction fibers. A prominent U wave may be due to hypercalcemia or digoxin toxicity The 8-step method is a thorough way of evaluating ECGs. 1. Determine ECG rhythm. For atrial rhythm, measure the P-P intervals (interval between consecutive P waves). Consistently similar P-P intervals indicates regular atrial rhythm. To determine ventricular rhythm, measure intervals between consecutive R waves in the QRS complexes; they should occur regularly. Variations of up to o.04 second are normal. Trick: place the straight edge of a piece of paper along the strip's baseline. Copy two consecutive P waves with a pencil. Move the paper and compare to subsequent P-P intervals to determine ifatrial rhythm is regular or irregular. Do the same for the R-R intervals. Determine atrial and ventricular rate. The easiest way to calculate heart rate is the 10-times method. ECG paper is marked in increments of 3 seconds (15 large boxes). To determine atrial rate, obtain a 6-second strip, count the number of P waves, and multiply by 1o. Ten 6-second strips represent i minute. Calculate ventricular rate the same way, using R waves. Evaluate the P wave. Are P waves present? Do they all have normal configurations? Do they all have a similar size and shape? Is there one P wave for every QRS complex? Determine the duration of the PR interval. Count the small squares between the start of the P wave and the start of the QRS complex (see diagram to the right); then multiply the number of squares by o.o4 sec. Is the duration normal (o.12 -o.20 sec.)? Is the PR interval consistent? 2. 3. 4.Explanation / Answer
STRIP 3:
Atrial rhythm: regular
Ventricular rhythm: Regular
Atrial rate:125beats per minute
Ventricular rate:125beats per minute
P wave: Normal, One P wave for every QRS Complex. normal size and shape of p wave.
PR interval: it is in the normal range. 0.12 sec.
QRS complex:It lies in the normal range 0.8 sec.
T wave: T wave is normal and all the amplitude is same in the given strip.
QT interval: It is in the normal range that is 0.36 sec
other observations: the Amplitude of R wave is reduced.
interpretation: ECG in strip 3 is normal. it shows normal regular rhythm with all normal waves, intervals and segments.
Strip 4:
Atrial rhythm: Irregular
Ventricular rhythm: Regular
Atrial rate:100 to 125beats per minute
Ventricular rate:125beats per minute
P wave: Normal, One P wave for every QRS Complex. normal size and shape of p wave.
PR interval: it is in the normal range. 0.12 sec.
QRS complex:It lies in the normal range 0.8 sec.
T wave: T wave is normal and all the amplitude is same in the given strip.
QT interval: It is in the normal range that is 0.4 sec
other observations: Compensatory pause seen
interpretation: ECG in strip 4 shows non compensatory pause following atrial premature complex
Strip 5:
Atrial rhythm:not present
Ventricular rhythm: Irregular
Atrial rate:60 to 100 beats per minute
Ventricular rate:130 to 160 beats per minute
P wave: Not seen
PR interval: cannot be measured.
QRS complex:it is abnormal and bizarre. No proper alignment of QRS complex
T wave: T wave is superimposed with QRS complex
QT interval: It is irregular and abnormal. It is widened.
other observations: nil
interpretation: Monomorphic ventricular tachycardia
Strip 6:
Atrial rhythm:Regular
Ventricular rhythm: Regular
Atrial rate:94beats per minute
Ventricular rate:94 beats per minute
P wave: present and normal. It is seen with every QRS complex
PR interval: It is abnormal.0.28 sec. but consistent
QRS complex:it is in the normal range. o.o8 sec. and occurs with every P wave
T wave: T wave is normal . It has normal shape and occurs with every QRS complex.
QT interval: It is regular. It lies in the normal range o.36 sec.
other observations: Increased R wave amplitude
interpretation:Prolonged PR Interval suggesting first degree AV block.
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