Cardiac Rhythms

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Premature Ventricular Complex (PVC)

Look for rhythm that is irregular, with heart rate that is the underlying rate. Notice that the P wave is absent. The PR interval is not measurable. The QRS is typically wide (> 0.10 sec), bizarre appearance. Two PVCs together are termed a couplet while three PVCs in a row with a fast rhythm is ventricular tachycardia.

RhythmIrregularRateThe underlying rateP WaveAbsentPR IntervalNot measurableQRSWide (> 0.10 sec), bizarre appearanceNotesTwo PVCs together are termed a couplet while three PVCs in a row with a fast rhythm is ventricular tachycardia

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Atrial Fibrillation

Look for rhythm that is irregular, with heart rate that is very fast (> 350 bpm) for atrial, but ventricular rate may be slow, normal or fast. Notice that the P wave is absent - erratic waves are present. The PR interval is absent. The QRS is typically normal but may be widened if there are conduction delays.

RhythmIrregularRateVery fast (> 350 bpm) for Atrial, but ventricular rate may be slow, normal or fastP WaveAbsent - erratic waves are presentPR IntervalAbsentQRSNormal but may be widened if there are conduction delays

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Supraventricular Tachycardia (SVT)

Look for rhythm that is regular, with heart rate that is fast (150-250 bpm). Notice that the P wave is merged with t wave. The PR interval is normal (0.12 sec). The QRS is typically normal (.10 sec). PR interval can be difficult to measure.

RhythmRegularRateFast (150-250 bpm)P WaveMerged with T wavePR IntervalNormal (0.12 sec)QRSNormal (.10 sec)NotesPR interval can be difficult to measure

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Second Degree Heart Block Type 1

Look for rhythm that is irregular but with progressively longer pr interval lengthening, with heart rate that is the underlying rate. Notice that the P wave is normal. The PR interval is progressively longer until a qrs complex is missed, then cycle repeats. The QRS is typically normal (0.06-0.10 sec).

RhythmIrregular but with progressively longer PR interval lengtheningRateThe underlying rateP WaveNormalPR IntervalProgressively longer until a QRS complex is missed, then cycle repeatsQRSNormal (0.06-0.10 sec)

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Idioventricular Rhythm

Look for rhythm that is regular, with heart rate that is slow (20-40 bpm). Notice that the P wave is absent. The PR interval is not measurable. The QRS is typically wide (>0.10 sec), bizarre appearance.

RhythmRegularRateSlow (20-40 bpm)P WaveAbsentPR IntervalNot measurableQRSWide (>0.10 sec), bizarre appearance

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Sinus Arrest

Look for rhythm that is irregular due to pause, with heart rate that is normal to slow. Notice that the P wave is normal. The PR interval is normal (0.12-0.20 sec). The QRS is typically normal (0.06-0.10 sec). Pause time is not an integer multiple of the P-P interval.

RhythmIrregular due to pauseRateNormal to slowP WaveNormalPR IntervalNormal (0.12-0.20 sec)QRSNormal (0.06-0.10 sec)NotesPause time is not an integer multiple of the P-P interval

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Atrial Flutter

Look for rhythm that is regular or irregular, with heart rate that is fast (250-350 bpm) for atrial, but ventricular rate is often slower. Notice that the P wave is not observable, but saw-toothed flutter waves are present. The PR interval is not measureable. The QRS is typically normal (0.06-0.10 sec).

RhythmRegular or irregularRateFast (250-350 bpm) for Atrial, but ventricular rate is often slowerP WaveNot observable, but saw-toothed flutter waves are presentPR IntervalNot measureableQRSNormal (0.06-0.10 sec)

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Third Degree Heart Block

Look for rhythm that is regular, but atrial and ventricular rhythms are independent, with heart rate that is characterized by atrial rate usually normal and faster than ventricular rate. Notice that the P wave is normal shape and size, may appear within qrs complexes. The PR interval is absent: the atria and ventricles beat independently.. The QRS is typically normal, but wide if junctional escape focus.

RhythmRegular, but atrial and ventricular rhythms are independentRateCharacterized by Atrial rate usually normal and faster than ventricular rateP WaveNormal shape and size, may appear within QRS complexesPR IntervalAbsent: the atria and ventricles beat independently.QRSNormal, but wide if junctional escape focus

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Sinus Tachycardia

Look for rhythm that is regular, with heart rate that is fast (> 100 bpm). Notice that the P wave is normal, may merge with t wave at very fast rates. The PR interval is normal (0.12-0.20 sec). The QRS is typically normal (0.06-0.10 sec). QT interval shortens with increasing heart rate.

RhythmRegularRateFast (> 100 bpm)P WaveNormal, may merge with T wave at very fast ratesPR IntervalNormal (0.12-0.20 sec)QRSNormal (0.06-0.10 sec)NotesQT interval shortens with increasing heart rate

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First Degree Heart Block

Look for rhythm that is regular, with heart rate that is the underlying rate. Notice that the P wave is normal. The PR interval is prolonged (>0.20 sec). The QRS is typically normal (0.06-0.10 sec). A first degree AV block occurs when electrical impulses moving through the Atrioventricular (AV) node are delayed (but not blocked). First degree indicates slowed conduction without missed beats.

RhythmRegularRateThe underlying rateP WaveNormalPR IntervalProlonged (>0.20 sec)QRSNormal (0.06-0.10 sec)NotesA first degree AV block occurs when electrical impulses moving through the Atrioventricular (AV) node are delayed (but not blocked). First degree indicates slowed conduction without missed beats.