A 63-year-old man with chronic hypertensive atherosclerotic heart disease and stable anginal syndrome had complained of intermittent palpitations for the past 2 weeks. The palpitations were unrelated to activity or food intake. He was compensated and not on any routine cardiac drug therapy. Sublingual nitroglycerin promptly relieved his anginal episodes. The tracings in Figure 1 were recorded when he was seen initially.

A tracing recorded a few minutes later is shown in Figure 2.

His bundle recordings were obtained to confirm the clinical impression (Figure 3).

1.    c. upper tracing: sinus rhythm with complete LBBB and His extrasystoles with slight aberrancy; blocked sinus P wave

lower tracing: pseudo Mobitz II 2:1 AV block due to concealed His extrasystoles d. same as c, but extrasystoles are from a focus in the RBB

    d. same as c, but extrasystoles are from a focus in the RBB

When the upper and...

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