Page 74 - Basic Monitoring in Canine and Feline Emergency Patients

Are P waves
VetBooks.ir present?

No Yes

How are P waves
Atrial standstill related to QRS
(see Fig. 3.18)
complexes?

All P waves followed Nonconducted P
by QRS compexes waves present

2nd or 3rd degree
What is the timing AV block
of R–R intervals?
(see Figs. 3.15 and 3.16)

Periods of sinus
Regular R–R >10% variation in arrest (> 2 R–R
intervals R–R intervals
intervals)

Sinus node
Sinus arrhythmia
Sinus bradycardia dysfunction (see
(see Fig. 3.7)
Fig. 3.17)
Fig. 3.19. Algorithm for ECG diagnosis of bradyarrhythmias.

drive excess potassium intracellularly include dex- AV block, SND, atrial standstill arrhythmias, and
trose ± exogenous insulin, β2-agonists such as sinus arrhythmia using ECG findings (see Fig. 3.19).
albuterol, and sodium bicarbonate; the underlying
disease should then be addressed (see Chapter 8). 1. Are P waves present? The presence of P waves
For dogs with primary atrial myopathy, treatment demonstrates that the atrial myocytes are capable of
of atrial standstill involves permanent pacemaker depolarization. Complete absence of P waves is sug-
implantation. gestive of atrial standstill; all other bradyarrhyth-
mias will have presence of at least some P waves.
2. How are P waves related to QRS complexes? If
P waves are present, the next step is to determine
their relationship to QRS complexes. If there are
Basic algorithm for differentiating
bradyarrhythmias any P waves that are not followed by QRS com-
plexes, this suggests that those P waves are not
The following algorithm can help to differentiate the being conducted through the AV node to the ventricles.
five common bradyarrhythmias (sinus bradycardia, Presence of nonconducted P waves is characteristic

66 J.L. Ward