Wagner_Marriot's Practical Electrocardiography, 12e

I

II

III

A

I

II

III

B F I G U R E 2 2 . 5 .

Leads I, II, and III rhythm strips from a patient with chronic bronchitis and cor pulmonale (A) and a 79-year-old woman with acute pulmonary edema (B) , both of whom were receiving long-term digitalis therapy for heart failure. Arrows indicate P waves that completely fail to conduct to the ventricles.

Second-degree AV block may have any ratio of P waves to QRS complexes (Fig. 22.5). In Figure 22.5A, there are the commonly appearing 3:2 and 4:3 AV conduction ratios. However, in Figure 22.5B the sinus rate is in the tachycardia range, and the more rapid “bombardment” of the AV node causes the 2:1 ratio to be intermittently increased to 3:1.

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SECTION III: Abnormal Rhythms