Figure 2-16. Premature atrial contraction (PAC).
d. Atrial Tachycardia.
(1) Analysis. Atrial tachycardia (AT) is caused when a single focus in the
atria fires very rapidly and overrides the SA node. The rhythm is regular and the
heartbeat rate is 150 to 250 beats per minute. The atrial P wave differs from the sinus
P wave and can be lost in the preceding T wave. The PR interval is 0.12 to 0.20 of a
second with the QRS less than 0.12 of a second. There are two forms of clinical atrial
tachycardia: paroxysmal AT/supraventricular tachycardia (PAT/PSVT) and
nonparoxysmal AT. Paroxysmal AT/supraventricular tachycardia is characterized by
repeated episodes of atrial tachycardia. The episodes may begin abruptly and last from
a few seconds to many hours. Nonparoxysmal atrial tachycardia is an abnormal heart
problem that is secondary to some other problem.
(2) Treatment. Treatment for nonparoxysmal AT is the same as for sinus
tachycardia. See paragraph 2-7c. Treatment for PAT/PSVT is as follows:
(a) Unstable patient (blood pressure less than 90 mm Hg, systolic):
1 Administer synchronized cardioversion of 75 to 100 joules.
2 If there is no response, repeat at 200 joules.
3 If there is still no response, repeat synchronized cardioversion
at 360 joules.
4 Correct any underlying abnormalities.
5 Give pharmacological therapy; perform cardioversion.