compensatory

PVC

Figure 61 Mechanism of Premature Ventricular Complex

Rate: depends on

underlying rhythm

Pacemaker: an irritable

focus within the ventricles

Regularity: the ectopic

interrupts the regularity of

the underlying rhythm

Conduction: conduction

through the ventricles is

prolonged

A single irritable focus within the ventricles that fires prematurely to initiate an ectopic complex.

This is a single beat, not an entire rhythm; the underlying rhythm also must be identified.

Figure 62 T Wave Configuration in PVCs

(a)

T

QRS

(b)

T

QRS

Ventricular Rhythms 217

Figure 63 Examples of Typical PVC Configurations

(b)

X

X

(a)

(d)

X

(c)

X

(e)

X

(g) (h)

X

(f)

X

X

218 Chapter 8

2 times R-R interval

PVC with compensatory pause

Figure 64 Compensatory Pause

10. Although it is most common for PVCs to be followed by compensatory pauses, this

is not a rigid requirement. An alternative configuration possibility is that the PVC be

followed by no pause whatsoever. This occurs when the PVC squeezes itself in between

two regular complexes and does not disturb the regularity of the sinus node. This is

called an interpolated PVC, because the PVC inserts itself between two regular beats

(Figure 65). With an interpolated PVC, the R–R interval remains ,

since the PVC does not interrupt the sinus rhythm.

11. If a PVC is followed by a pause before the next sinus beat, leaving a distance

between the sinus beat before the PVC and the sinus beat following the PVC,

which measures exactly twice the normal R–R interval, you would call this a

 pause. However, if the PVC falls between two sinus

beats, without interrupting the regularity of the underlying rhythm, you would call

this an PVC.

12. As with other types of ectopics, a PVC will interrupt the underlying rhythm.

In interpreting the rhythm strip, it is important to identify both the ectopic and the

underlying arrhythmia. For example, the arrhythmia might be Sinus Tachycardia with

a PVC. When you are reporting a PVC, you should convey as much information about

the disorder as possible, including identifying the rhythm.

13. Several other items should be noted about a PVCs. Since PVCs are an indication

of myocardial irritability, it is important to note how frequently they are occurring.

If the patient is having only an occasional PVC, this may be a normal rhythm

regular

compensatory

interpolated

underlying

Figure 65 Interpolated PVC

1 times R-R interval

Interpolated PVC

Ventricular Rhythms 219

for that person. But if the frequency picks up so that you are seeing 5–10 per minute,

you would suspect that the ectopics were an indication of increasing myocardial

. If the patient is experiencing chest pain of any sort, even a

single PVC could be ominous. It is important that you note not only the presence of

PVCs, but also the of occurrence.

Unifocal vs. Multifocal

14. If a single focus within the ventricles is the source of the PVCs, all of these ectopics

will have an identical appearance. That is, if one PVC first has a positive deflection,

and then a wide negative deflection, all other PVCs from that single focus will have

that same configuration. These would be considered unifocal PVCs (Figure  66),

because they all came from a focus and are all uniform in

configuration. If all the PVCs on a rhythm strip had similar appearances, you would

assume that they all originated from a ectopic focus and would

call them PVCs.

15. In cases of greater irritability, several ventricular foci might begin to initiate

ectopics. In that case, the PVCs would have a variety of configurations (Figure 67).

If two foci were initiating PVCs, all of the PVCs would have one of two configurations.

irritability

frequency

single

single

unifocal

Figure 66 Unifocal PVCs

Figure 67 Multifocal PVCs

220 Chapter 8

If more sites were irritable, there would be a greater variety of .

When PVCs have multiple configurations, they are called multifocal because the heart

is so irritable that multiple foci are initiating the ectopics. Since they originate from

multiple foci, PVCs are more serious than unifocal PVCs

because they are associated with a more irritable myocardium.

16. If the PVCs on a rhythm strip all had the same basic configuration, they would

be considered . If the PVCs had differing configurations, they

would be considered .

The terms unifocal and multifocal are used to describe whether ectopics have a consistent

configuration or varying morphologies. These terms are based on the presumption that

uniform shapes result from a single irritable focus, whereas varying configurations are

caused by multiple irritable foci. You may hear other terms used for the same purpose:

uniformed for ectopics with one shape and multiformed for ectopics with varying shapes.

For our purposes, you may consider unifocal and uniformed to be synonymous. Consider

multifocal and multiformed synonymous as well.

R on T Phenomenon

17. PVCs represent a major electrical force, since they reflect a premature depolarization

of the ventricles. Because they come prematurely, they often fall near the end of the

preceding QRS complex. If you recall, in Chapter  2, we learned that a portion of

the T wave is considered a vulnerable area, because an electrical impulse falling

during that vulnerable phase could cause an aberrant depolarization of the heart. If a

PVC occurs during the phase, it could throw the heart into an

uncontrolled repetitive pattern. For this reason, it is important to note any PVC that falls

on or near the wave of the preceding beat. This phenomenon

is called R on T because the R wave of the PVC is hitting on the T wave of the preceding

complex (Figure 68). If you see PVCs creeping up on the preceding T wave, you would

call this an phenomenon and know that it represents a very

serious situation.

18. The R on T phenomenon exists when the R wave of a falls

on or near the vulnerable phase of the cardiac cycle. The vulnerable phase, or relative

refractory period, is located on the downslope of the wave.

(Note: If you have forgotten this material, turn back to Chapter 2, Frames 51–57, for a

quick review.)

configurations

multifocal

unifocal

multifocal

vulnerable

T

R on T

PVC

T

Figure 68 R on T Phenomenon: Ectopic A exhibits R on T phenomenon; Ectopic B does not

A B

Ventricular Rhythms 221

Runs and Couplets

19. Another sign of increasing myocardial irritability is when PVCs occur in immediate

succession, without a normal beat intervening. If only two PVCs occur before the

normal pattern resumes, you would see two PVCs attached to each other. This is called

a couplet (Figure 69), but if you see three or more PVCs occurring in succession, this

would be called a run of PVCs (Figure 70). The important distinction here is that several PVCs have fired without allowing the normal pacemaker to resume pacemaking

responsibility. This is an indication of significant . Regardless of

whether you call this pattern a couplet or a run of PVCs, you should note that the PVCs

are occurring in immediate succession and indicate the number of PVCs observed.

Technically, two successive PVCs would be called a , but it is

sufficient to call any number of successive PVCs a of PVCs and

then indicate the number of PVCs involved.

20. A pair of PVCs in immediate succession could be called either a

 or a of two PVCs. But if there were

three or more PVCs in a row, it should be called a of three

(or more) . The important thing here is to note that an

increasing number of PVCs indicates increasing myocardial .

irritability

couplet

run

couplet

run

run

PVCs

Figure 69 PVCs Occurring as a Couplet (Pair)

Figure 70 PVCs Occurring in a Run

222 Chapter 8

Grouped Beating

21. Sometimes, frequently occurring PVCs will fall into a pattern with the surrounding

normal beats. This is called grouped beating. For example, you may see a PVC, then a

normal beat, then a PVC, then a normal beat, and so on. When the PVCs are falling in a

pattern of “every other beat” (Figure 71) with the normal beats, this is called bigeminy

(pronounced bī-jem’-eny). Bigeminy refers to a repetitive pattern of grouped beating

(e.g., one normal and one PVC) across the entire strip. When you see a pattern of one

PVC, then one normal beat, then one PVC, then one normal beat, and this pattern

continues across the strip, you would call the rhythm of PVCs. bigeminy

Figure 71 Patterns of Grouped Beating

(a)

Bigeminy

(b)

Trigeminy

(c)

Quadrigeminy

Ventricular Rhythms 223

22. Don’t forget, though, to include the identification of the underlying rhythm.

For example, if you saw a sinus beat, then a PVC, then a sinus beat, then a

PVC, across the strip, you would call this Sinus Rhythm with bigeminy of

.

23. Several other patterns of grouped beating that are very similar to bigeminy

result from PVCs falling into a rhythm with normal beats. For example, if you

saw a PVC followed by two sinus beats, then another PVC followed by two

sinus beats, you would have a repetitive cycle of three beats: one PVC, and

two sinus beats. This pattern is called trigeminy, since the cycle contains three beats.

Such a rhythm would be called Sinus Rhythm with

of PVCs.

24. Another such pattern is quadrigeminy, where a pattern of four beats consists of

one PVC and three normal beats. If you had a long enough rhythm strip, you could

probably map out patterns of as many as eight, nine, or more beats to a cycle.

However, the most common are bigeminy, a cycle consisting of one PVC and

one normal beat; trigeminy, a cycle including one PVC and two normal beats; and

, where there are four complexes to the cycle: one PVC,

and three normal beats.

25. Patterns such as bigeminy, trigeminy, and quadrigeminy can be found with other

ectopics as well as PVCs. For example, you can have bigeminy of PACs or quadrigeminy of PJCs. But to qualify as a true patterned beat, the grouping should continue

across the entire strip. Just because you happen to have two PACs on the strip with a

single normal beat between them, you could not necessarily call this bigeminy. But if

the pattern continued regularly across the strip, you would call it Sinus Rhythm with

bigeminy of .

26. You now know quite a few things about PVCs. They are wide and bizarre, with

a QRS measurement of . Frequently, the T wave will be in

the opposite direction of the . PVCs are a sign of myocardial

, so you should note how frequently they are occurring. You

should also note if they are all coming from a single focus, in which case you would

call them . If they are coming from more than one focus, you

would call them .

27. You should be very cautious with a PVC that is falling near the downslope of

the wave, since this is the vulnerable phase of the cardiac

cycle. This is called phenomenon and is dangerous because it

could throw the heart into an ineffective repetitive pattern.

28. If the myocardium is irritable enough, you may notice PVCs falling in succession,

without an intervening normal beat. If there were several PVCs connected in this

manner, you would call it a of PVCs and would note how

many ectopics were involved. If there were only two PVCs paired, you might call this

a .

29. Finally, you know that PVCs can fall into patterns with the underlying normal

beats. If it is a pattern of twos (i.e., one normal, one PVC), you would call this

. If it is a pattern of threes, it is called ,

and it is called quadrigeminy if there are complexes in

the pattern.

PVCs

trigeminy

quadrigeminy

PACs

0.12 second or more

QRS complex

irritability

unifocal

multifocal

T

R on T

run

couplet

bigeminy; trigeminy

four

224 Chapter 8

30. Here are the rules for PVCs (Figure 72):

Regularity: ectopics will disrupt regularity of underlying rhythm

Rate: depends on underlying rhythm and number of ectopics

P Waves: will not be preceded by a P wave; dissociated P wave may be seen

near PVC

PRI: since the ectopic comes from a lower focus, there will be no PRI

QRS: wide and bizarre; 0.12 second or greater; T wave is usually in opposite

direction from R wave

Ventricular Tachycardia (VT)

31. If the myocardium is extremely irritable, the ventricular focus could speed up and

override higher pacemaker sites. This would create what is essentially a sustained run

of PVCs. This rhythm is called Ventricular Tachycardia (VT) (Figure 73). In fact, a

run of PVCs is often called a short burst of VT. They both result from myocardial

, and they both fit the same rules. However, PVCs are

 ectopics, whereas VT is an actual arrhythmia. In VT you will

see a succession of PVCs across the strip at a rate of about 150–250 bpm. This arrhythmia

usually has a very uniform appearance, even though the R–R interval may be slightly

irregular. It is possible for VT to occur at slower rates, but when it does, it is qualified

by calling it a slow VT. A true VT has a ventricular rate of bpm.

irritability

single

150–250

Figure 72 Rules for Premature Ventricular Complex

Premature Ventricular Complex

Regularity: The underlying rhythm can be regular or irregular. The ectopic PVC will interrupt the regularity of the

underlying rhythm (unless the PVC is interpolated).

Rate: The rate will be determined by the underlying rhythm. PVCs are not usually included in the rate

determination because they frequently do not produce a pulse.

P Waves: The ectopic is not preceded by a P wave. You may see a coincidental P wave near the PVC, but it is

dissociated.

PRI: Since the ectopic comes from a lower focus, there will be no PRI.

QRS: The QRS complex will be wide and bizarre, measuring at least 0.12 second. The configuration will

differ from the configuration of the underlying QRS complexes. The T wave is frequently in the opposite

direction from the QRS complex.

Ventricular Rhythms 225

32. Each of the other rules for a PVC also applies to VT. The QRS complex will be

0.12 second or greater, and the complex will be and bizarre,

with the T wave usually in the opposite direction of the wave.

Since this rhythm originates from a focus, you will not see

a P wave in front of the QRS complex. However, this is another form of AV dissociation, so you may see an occasional P wave coincidentally occurring near the QRS

complex. As with PVCs, VT will have a QRS measurement of

second or greater, with a bizarre configuration of the

complex and T wave, and there will be no waves preceding

the QRS complexes.

33. Ventricular Tachycardia is caused by a focus in the

ventricles that fires at a tachycardia rate to override the higher pacemaker sites

and take over control of the heart. It is also possible for the ventricular focus to

change to a flutter mechanism, which would result in an arrhythmia very similar to

VT but with a ventricular rate of more than 300. When the ventricles depolarize at

such a rapid rate, the resultant EKG pattern becomes a very uniform, regular tracing and looks almost like a coiled spring. There is very little difference between

VT and Ventricular Flutter, except for the rate. Most clinicians choose to consider

Ventricular Flutter in with VT and eliminate this academic distinction. For our

purposes, we will consider Ventricular Flutter a rapid form of VT. We will not make

a distinction between the two, since the only real difference is in the ventricular

.

34. Here are the rules of Ventricular Tachycardia (Figure 74):

Regularity: usually regular; can be slightly irregular

Rate: 150–250 bpm; can exceed 250 bpm if the rhythm progresses to

Ventricular Flutter; may occasionally be slower than 150 bpm,

in which case it is called slow VT

P Waves: will not be preceded by P waves; dissociated P waves may be seen

PRI: since the focus is in the ventricles, there will be no PRI

QRS: wide and bizarre; 0.12 second or greater; T wave is usually in opposite

direction from R wave

wide

R

ventricular

0.12

QRS

P

single

rate

Figure 73 Mechanism of Ventricular Tachycardia

Pacemaker: an irritable

focus within the ventricles

Rate: 150–250 bpm

Conduction: conduction

through the ventricles is

prolonged

Regularity: regular, can be

slightly irregular

An irritable focus within the ventricles fires regularly at a rapid rate to override higher sites for control

of the heart.

226 Chapter 8

Ventricular Fibrillation

35. In extreme myocardial irritability, the electrical foci in the ventricles can begin firing

in a rapid, disorganized manner. This rhythm is called Ventricular Fibrillation

(Figure 75). The ventricles can’t respond to such chaotic signals, and thus can’t pump

blood effectively. Ventricular Fibrillation is a lethal arrhythmia, because the heart’s

pumping function is totally .

36. Ventricular Fibrillation (VF) is probably the easiest of all the arrhythmias to

recognize. This is because there are no discernible complexes or intervals and the entire

rhythm consists of chaotic, irregular activity. Since there are no identifiable complexes

or wave forms, the EKG pattern of VF is simply a grossly

fibrillatory pattern.

ineffective

chaotic

Figure 74 Rules for Ventricular Tachycardia

Ventricular Tachycardia

Regularity: This rhythm is usually regular, although it can be slightly irregular.

Rate: Atrial rate cannot be determined. The ventricular rate range is 150–250 bpm. If the rate is below 150 bpm,

it is considered a slow VT. If the rate exceeds 250 bpm, it is called Ventricular Flutter.

P Waves: None of the QRS complexes will be preceded by P waves. You may see dissociated P waves

intermittently across the strip.

PRI: Since the rhythm originates in the ventricles, there will be no PRI.

QRS: The QRS complexes will be wide and bizarre, measuring at least 0.12 second. It is often difficult to

differentiate between the QRS and the T wave.

Figure 75 Mechanism of Ventricular Fibrillation

Pacemaker: multiple

irritable foci within the

ventricles

Rate: unable to determine

Conduction: prolonged to

the point that actual QRS

complexes are not

Regularity: grossly distinguishable

chaotic; no pattern of

electrical activity

Multiple foci within the ventricles become irritable and generate uncoordinated, chaotic impulses

that cause the heart to fibrillate rather than contract.

Ventricular Rhythms 227

37. VT is distinguishable from VF because Ventricular Tachycardia has wide, bizarre

complexes, but they are uniform and measurable. VF has no measurable waves

or .

38. Here are the rules for Ventricular Fibrillation (Figure 76):

Regularity:

Rate:

P Wave:

PRI:

QRS:

totally chaotic with no discernible waves or complexes

































Idioventricular Rhythm

39. So far, you have learned three ventricular arrhythmias, all of which are the result

of ventricular irritability. These are PVCs, Ventricular Tachycardia, and Ventricular

Fibrillation. It is also possible for a ventricular rhythm to be produced by an escape

mechanism. If a higher pacemaker site fails, a ventricular focus can step in to take

over pacemaking responsibility. There are two ways a ventricular focus can assume

control of the heart. One is irritability and the other is

mechanism.

40. A ventricular escape rhythm is one that takes over pacemaking in the absence

of a higher focus and depolarizes the heart at the inherent rate of the ventricles, which

is bpm. This rhythm is called Idioventricular Rhythm

(Figure 77) because the ventricles are initiating the rhythm on their own, without a

conducted stimulus from a higher focus. The rate for Idioventricular Rhythm would

be bpm.

complexes

escape

20–40

20–40

Figure 76 Rules for Ventricular Fibrillation

Ventricular Fibrillation

Regularity: There are no waves or complexes that can be analyzed to determine regularity. The baseline is totally

chaotic.

Rate: The rate cannot be determined since there are no discernible waves or complexes to measure.

P Waves: There are no discernible P waves.

PRI: There is no PRI.

QRS: There are no discernible QRS complexes.

228 Chapter 8

41. You can consider Idioventricular Rhythm to be a ventricular escape rhythm, since

it is a fail-safe rhythm that takes over when pacemaker sites

fail. A ventricular focus firing within the inherent rate range of the ventricles would

produce a rhythm called Rhythm.

42. You should not see P waves in an Idioventricular Rhythm, since the escape mechanism would take over only if the supraventricular pacemaker sites had failed. What you

will see is a rhythm of very slow ventricular complexes, usually in a regular rhythm,

although it is possible for such an unreliable pacemaker to discharge irregularly. An

Idioventricular Rhythm will not have waves. Instead, you will

see ventricular complexes measuring at least second, firing at

a rate of 20–40 bpm.

43. Idioventricular Rhythm is initiated by the very last possible fail-safe mechanism

within the heart. This means that it is frequently an unreliable focus. It may fire a little

irregularly, and the rate may be less than 20 bpm, even though the intrinsic ventricular

rate is supposed to be 20–40 bpm. When the rhythm is in its terminal stages—that is, as

the patient is dying—the complexes can lose some of their form and be quite irregular.

In this stage, the arrhythmia is said to be agonal, or a dying heart. The word agonal is

used to describe a terminal, lethal arrhythmia, especially when it has stopped beating

in a reliable pattern. Idioventricular Rhythm is an rhythm,

especially when the rate drops below 20 bpm and the pattern loses its uniformity.

44. Here are the rules for Idioventricular Rhythm (Figure 78):

Regularity: usually regular

Rate: 20–40 bpm; can drop below 20 bpm

P Waves: none

PRI: none

QRS: wide and bizarre; 0.12 second or more

Asystole

45. The last stage of a dying heart is when all electrical activity ceases. This results in

a straight line on the EKG, an arrhythmia called Asystole (pronounced ā · siś-toe-lee)

(Figure 79). Asystole is a period of absent electrical activity, seen on the EKG as a

 line, possibly with some undulations in it. Asystole is a lethal

arrhythmia that is very resistant to resuscitation efforts.

higher

Idioventricular

P

0.12

agonal

straight

Figure 77 Mechanism of Idioventricular Rhythm

Conduction: prolonged

conduction through the

ventricles

Pacemaker: escape focus

within the ventricles

Rate: usually 20-40 bpm,

but often falls below 20

bpm

Regularity: usually regular,

but can be regular at

slower rates

In the absence of a higher pacemaker, the ventricles initiate a regular impulse at their inherent rate to

take control of the heart.

Ventricular Rhythms 229

46. The absence of cardiac electrical activity will cause a straight line on the EKG. This

rhythm is called . To be certain there is no electrical activity,

you should first make sure the machine is not malfunctioning, then view the rhythm

in more than one lead.

Here are the rules for Asystole (Figure 80):

Regularity:

Rate:

P Wave:

PRI:

QRS:

straight line indicates no electrical activity

































47. A straight line on the EKG would suggest that there is no electrical activity left in

the heart. This rhythm would be called .

Asystole

Asystole

Figure 78 Rules for Idioventricular Rhythm

Idioventricular Rhythm

Regularity: This rhythm is usually regular, although it is less reliable as the heart dies.

Rate: The ventricular rate is usually 20–40 bpm, but it can drop below 20 bpm.

P Waves: There are no P waves in this arrhythmia.

PRI: There is no PRI.

QRS: The QRS complex is wide and bizarre, measuring at least 0.12 second.

Figure 79 Mechanism of Asystole

Pacemaker: no pacemaker

is firing

Rate: no rate because no

pacemaker is firing

Conduction: no electrical

activity

Regularity: no electrical

activity

The heart has lost its electrical activity. There is no electrical pacemaker to initiate electrical flow.

230 Chapter 8

48. If the EKG only has ventricular complexes at a rate between 20 and 40 bpm, with

no P waves, you would call the arrhythmia Rhythm.

49. An EKG that is totally chaotic, with no discernible waves or complexes, and nothing

but a lot of irregular undulations, would fit the rules of .

50. Ventricular Tachycardia is a very rapid rhythm with wide, bizarre QRS complexes,

and no waves.

51. A single ectopic with a QRS greater than 0.12 second, with a T wave in the opposite

direction of the R wave and having no P wave preceding it, would be called a

Premature Complex.

52. You now have all the information you need to approach ventricular rhythms. Turn

to the Practice Strips at the end of this chapter and apply your new knowledge until

you feel very comfortable in this area.

Pulseless Electrical Activity (PEA)

53. There is a condition in which the EKG shows electrical activity that should

produce a pulse, but no pulse can be detected in the patient. This is not a rhythm itself;

it is a condition called Pulseless Electrical Activity. PEA can be seen in many rhythms,

including NSR, tachycardias, and bradycardias. PEA occurs when a heart rhythm on

the EKG does not produce the expected pulse. The key to a quick diagnosis is to take

the patient’s to see if the electrical activity is generating a

mechanical response.

Idioventricular

Ventricular Fibrillation

P

Ventricular

Practice Strips

pulse

Figure 80 Rules for Asystole

































Regularity:

Rate:

P Wave:

PRI:

QRS:

straight line indicates absence of electrical activity

Ventricular Rhythms 231

54. PEA cannot be detected by looking at the EKG alone. It is necessary to take the

patient’s before the diagnosis can be made.

55. PEA often has a treatable underlying cause. One of the most common causes, and

most treatable, is hypovolemia. In order to diagnose PEA, it is necessary to look at

the while checking the patient for a corresponding

.

56. If no cause for PEA can be found, it should be treated as Asystole.

pulse

EKG

pulse

232