b. Wandering Pacemaker.
(1) Analysis. The rhythm is slightly irregular with a normal heartbeat rate of
from sixty to one hundred beats per minute. The P wave may change from heartbeat to
heartbeat. The PR interval is less than 0.20 of a second and may vary. The QRS is
less than 0.12 of a second. If the cardiac output falls, sympathomimetic or
parasympatholytic drugs can be given.
(2) Treatment. There is no treatment. The pacemaker shifts between the
SA node and the atria. This shift causes each P wave to differ slightly from the P waves
Figure 2-15. Wandering pacemaker.
c. Premature Atrial Contractions.
(1) Analysis. Premature Atrial Contractions (PACs) are single heartbeats
that originate in the atria and come early in the cardiac cycle. The rhythm depends on
the underlying rhythm that will usually be regular except for the premature atrial
contraction. The heartbeat rate is usually normal depending on the underlying rhythm.
The P waves of the early beat differ from sinus P waves. These P waves can be
flattened or notched and thus lost in the preceding T wave. The P-R interval is 0.12 to
0.20 of a second but can be greater than 0.20 of a second. The QRS is less than 0.12
of a second. Isolated PACs may occur in "normal' cardiovascularly healthy people.
Frequent PACs may indicate organic heart disease and possibly initiate atrial
(2) Treatment. The patient should be sedated. Stimulants such as alcohol,
caffeine, and tobacco should be eliminated.