Rate: 60-100

Rhythm: regular

Pacemaker site: SA node

P waves: upright and normal in morphology

PR interval: normal (0.12-0.20 second) and constant

QRS complex: normal (0.04-0.12 second)

Rate: less than 60

Rhythm: regular

Pacemaker site: SA node

P waves: upright and normal in morphology

PR interval: normal

QRS complex: normal

Rate: greater than 100

Rhythm: regular

Pacemaker site: SA node

P waves: upright and normal in morphology

PR interval: normal

QRS complex: normal

Rate: 60-100 (varies with respirations)

Rhythm: irregular

Pacemaker site: SA node

P waves: upright and normal in morphology

PR interval: normal

QRS complex: normal

Rate: normal to slow, depending on the frequency and duration of the arrest

Rhythm: irregular

Pacemaker site: SA node

P waves: upright and normal in morphology

PR interval: normal

QRS complex: normal

Rate: normal to slow, depending on the frequency and duration of the arrest

Rhythm: regular

Pacemaker site: SA node

P waves: upright and normal in morphology

PR interval: normal

QRS complex: normal

Rate: normal to slow, depending on the frequency and duration of the arrest

Rhythm: irregular

Pacemaker site: SA node

P waves: upright and normal in morphology

PR interval: normal

QRS complex: normal

Rate: extremely variable

Rhythm: irregular

Pacemaker site: SA node

P waves: upright and normal in morphology

PR interval: normal

QRS complex: normal

Rate: usually normal

Rhythm: slightly irregular

Pacemaker site: varies among the SA node, atrial tissue, and the AV junction

P waves: morphology changes from beat to beat, P waves may disappear entirely

PR interval: varies, may be less than 0.12 second, normal or greater than 0.20 second

QRS complex: normal

Rate: more than 100

Rhythm: irregular

Pacemaker site: ectopic sites in atria

P waves: organized, discrete nonsinus P waves with at least three different forms

PR interval: varies

QRS complex: may be less than 0.12 second, normal, or greater than 0.20 second, depending on the AV node's refractory status when the impulse reaches it

Rate: depends on the underlying rhthym

Rhythm: depends on the underlying rhthym, usually regular except for the PAC

Pacemaker site: ectopic focus in the atrium

P waves: the P wave of the PAC differs from the P wave of the underlying rhythm. It occurs earlier than the expected P wave and may be hidden in the preceeding T wave.

PR interval: usually normal, can vary with the location of the ectopic focus. Ectopic foci near the SA node will have a PR interval of 0.12 second or greater, whereas ectopic foci near the AV node will have a PR interval of 0.12 second or less.

QRS complex: usually normal, may be greater than 0.12 second if the PAC is abnormally conducted through partially refractory ventricles. In some cases, the ventricles are refractory and will not depolarize in response to the PAC. In these cases, the QRS complex is absent.

Paroxysmal Supraventricular Tachycardia

Rate: 150-250 per minute

Rhythm: characteristically regular, except at onset and termination

Pacemaker site: in the atria outside of the SA node

P waves: The P wave is often buried in the preceding T wave. The P wave may be impossible to see, especially if the rate is rapid. Turning up the speed of the graph paper or oscilloscope to 50 mm/second spreads out the complex and can help identify P waves.

PR interval: usually normal, however it can vary with the location of the ectopic pacemaker. Ectopic pacemakers near the SA node will have PR intervals close to 0.12 second, whereas ectopic pacemakers near the AV node will have PR intervals of 0.12 second or less.

QRS complex: normal

Rate: 150-250 per minute

Rhythm: characteristically regular, except at onset and termination

Pacemaker site: in the atria, outside the SA node

P waves: The P wave may be impossible to see especially if the rate is rapid. Turning up the speed of the graph paper or oscilloscope to 50 mm/second spreads out the complex and can help identify P waves.

PR interval: Usually normal, however it can vary with the location of the ectopic pacemaker. Ectopic pacemakers near the SA node will have PR intervals close to 0.12 second, whereas ectopic pacemakers near the AV node will have PR intervals of 0.12 second or less.

QRS complex: normal

Rate: atrial rate is 250-350 per minute. Ventricular rate varies with the ratio of AV conduction.

Rhythm: atrial rhythm is regular, ventricular rhythm is usually regular, but can be irregular if the block is variable.

Pacemaker site: sites in the atria, outside the SA node

P waves: flutter (F) waves are present, resembling a sawtooth or picket-fence pattern. This pattern is often difficult to identify in a 2:1 flutter. However, if the ventricular rate is approximately 150, suspect 2:1 flutter.

PR interval: Usually constant but may vary

QRS complex: normal

Rate: atrial rate is 350-750 per minute (cannot be counted) , ventricular rate varies greatly, depending on conduction through the AV node

Rhythm: irregularly irregular

Pacemaker site: numerous ectopic foci in the atria

P waves: none discernible. Fibrillation (f) waves are present, indicating chaotic atrial activity.

PR interval: none

QRS complex: normal

Rate: depends on the underlying rhythm

Rhythm: usually regular, can be slightly irregular

Pacemaker site: SA node or atria

P waves: normal

PR interval: greater than 0.20 second (diagnostic)

QRS complex: usually less than 0.12 second, may be bizarre in shape if conductive system disease exists in the ventricles

Rate: atrial rate is unaffected, the ventricular rate may be normal or slowed

Rhythm: atrial rhythm is typically regular, ventricular rhythm is irregular because of the nonconducted beat

Pacemaker site: SA node or atria

P waves: normal, some P waves are not followed by QRS complexes

PR interval: becomes progressively longer until the QRS complex is dropped, the cycle then repeats.

QRS complex: usually less than 0.12 second, may be bizarre in shape if conductive system disease exists in the ventricles

Rate: atrial rate is unaffected, ventricular rate is usually bradycardic

Rhythm: regular or irregular depending on whether the conduction ratio is constant or varied

Pacemaker site: SA node or the atria

P waves: normal, some P waves are not followed by QRS complexes

PR interval: constant for conducted beats, may be greater than 0.20 second

QRS complex: may be normal, however it is often greater than 0.12 second because of abnormal ventricular depolarization sequence

Rate: atrial rate is unaffected, ventricular rate is usually bradycardic

Rhythm: regular

Pacemaker site: SA node or atria

P waves: 2 P waves for every QRS complex

PR interval: constant for conducted beats, may be greater than 0.20 second

QRS complex: may be normal, however it is often greater than 0.12 second because of abnormal ventricular depolarization sequence.

Rate: atrial rate is unaffected. Ventricular rate is 40-60 if the escape pacemaker is junctional, less than 40 if the escape pacemaker is lower in the ventricles

Rhythm: both atrial and ventricular rhythms are usually regular.

Pacemaker site: SA node and AV junction or ventricle

P waves: normal, P waves show no relationship to the QRS complex, often falling within the T wave and QRS complex.

PR interval: no relationship between P waves and R waves

QRS complex: greater than 0.12 second if pacemaker is ventricular, less than 0.12 second if pacemaker is junctional

Rate: depends on the underlying rhythm

Rhythm: depends on the underlying rhythm, usually regular except for the PJC

Pacemaker site: ectopic focus in the AV junction

P waves: inverted, may appear before or after the QRS complex. P waves can be masked by the QRS complex or be absent.

PR interval: if the P wave occurs before the QRS complex, the PR interval will be less than 0.12 second, if the P wave occurs after the QRS complex then technically it is an R-P interval.

QRS complex: usually normal, may be greater than 0.12 second if the PJC is abnormally conducted through partial refractory ventricles.

Rate: 40-60 per minute

Rhythm: irregular in single junctional escape complex, regular in junctional escape rhythm.

Pacemaker site: AV junction

P waves: inverted, may be appear before or after the QRS complex. The P waves can be masked by the QRS or be absent.

PR interval: if the P wave occurs before the QRS complex, the PR interval will be less than 0.12 second. If the P wave occurs after the QRS complex technically it is an R-P interval.

QRS complex: usually normal, may be greater than 0.12 second

Rate: less than 40 per minute

Rhythm:irregular in single junctional escape complex, regular in junctional escape rhythm

Pacemaker site: AV junction

P waves:inverted, may be appear before or after the QRS complex. The P waves can be masked by the QRS or be absent.

PR interval: if the P wave occurs before the QRS complex, the PR interval will be less than 0.12 second. If the P wave occurs after the QRS complex technically it is an R-P interval.

QRS complex: usually normal, may be greater than 0.12 second

Rate: 60-100 per minute

Rhythm: normal

Pacemaker site: AV junction

P waves: inverted, may be appear before or after the QRS complex. The P waves can be masked by the QRS or be absent.

PR interval: if the P wave occurs before the QRS complex, the PR interval will be less than 0.12 second. If the P wave occurs after the QRS complex technically it is an R-P interval.

QRS complex: normal

Rate: 40-60 per minute (occasionally less)

Rhythm: the rhythm is irregular in a single escape complex. ventricular escape rhythms are usually regular unless the pacemaker site is low in the ventricular conductive system. such placement makes regularity unreliable

Pacemaker site: ventricles

P waves: none

PR interval: none

QRS complex: greater than 0.12 second and bizarre in morphology

Rate: 60-110 beats per minute

Rhythm: the rhythm is irregular in a single escape complex. ventricular escape rhythms are usually regular unless the pacemaker site is low in the ventricular conductive system. such placement makes regularity unreliable

Pacemaker site: ventricles

P waves: none

PR interval: none

QRS complex: greater than 0.12 second and bizarre in morphology

Rate: 100-250 (approximately)

Rhythm: usually regular, can be slightly irregular

Pacemaker site: ventricle

P waves: if present, not associated with the QRS complexes

PR interval: none

QRS complex: greater than 0.12 second and bizarre in morphology

Rate: depends on underlying rhythm and rate of PVCs

Rhythm: interrupts regularity of underlying rhythm, occasionally irregular

Pacemaker site: ventricle

P waves: none, however a normal sinus P wave (interpolated P wave) sometimes appears before a PVC

PR interval: none

QRS complex: greater than 0.12 second and bizarre in morphology

Rate: no organized rhythm

Rhythm: no organized rhythm

Pacemaker site: numerous ectopi foci throughout the ventricles

P waves: usually absent

PR interval: absent

QRS complex: absent

Rate: no organized rhythm

Rhythm: no organized rhythm

Pacemaker site: numerous ectopi foci throughout the ventricles

P waves: usually absent

PR interval: absent

QRS complex: absent

Rate: no electrical activity

Rhythm: no electrical activity

Pacemaker site: no electrical activity

P waves: usually absent, but in certain cases only P waves will be seen (no QRS complexes)

PR interval: absent

QRS complex: absent

Rate: varies with the preset rate of the pacemaker

Rhythm: regular if pacing constantly, irregular if pacing on demand

Pacemaker site: depends on electrode placement

P waves: none produced by ventricular pacemakers. Sinus P waves may be seen but are unrelated to the paced QRS complexes. Dual-chambered pacemakers produce a P wave behind each atrial spike. a pacemaker spike is an upward or downward deflection from the baseline, which is an artifact created each time the pacemaker fires. The pacemaker spike tells you only that the pacemaker is firing. It reveals nothing about ventricular depolarization.

PR interval: if present, varies

QRS complex: the QRS complexes associated with pacemaker rhythms are usually longer than 0.12 second and bizarre in morphology. They often resemble ventricular escape rhythms. A QRS complex should follow each pacemaker spike. If so, the pacemaker is said to be "capturing". With demand pacemakers, some of the patient's own QRS complexes may appear. A pacemaker spike should not be associated with these complexes.