CHAPTER 22: Atrioventricular Block
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A second-degree AV block may be intermittent (Fig. 22.4A) or continuous (see Fig. 22.4B).
Note that in Figure 22.4A, the second-degree block occurs only after a sequence of six con-
ducted beats, of which the first shows no AV block and the latter five show first-degree
block (7:6 block). In Figure 22.4B, there is continually alternating first- and second-degree
AV block with a 2:1 AV ratio. This is termed 2:1 (AV) block.
I
II
III
A
I
II
III
B
F I G U R E 2 2 . 4 .
Leads I, II, and III rhythm strips from a patient with chronic pulmonary disease
and receiving digitalis therapy
(A)
and a woman with hypertension and receiving both -adrenergic
and calcium antagonist therapy
(B)
.
Arrows
indicate failure of AV conduction and therefore the pres-
ence of second-degree AV block.
