PMC5412613_01
A: An electrocardiogram recorded at the patient's initial clinical visit. A 2:1 atrioventricular block was noted. B: A long-duration recording of an electrocardiogram at the initial clinical visit. The RR intervals were irregular during 2:1 atrioventricular block.
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An electrocardiogram (ECG) showed a second-degree 2:1 atrioventricular block with narrow QRS complexes (Figure 1A). Curiously, the RR intervals were not constant while the PP intervals remained steady during the 2:1 AV block (Figure 1B).
A: A device interrogation illustrating an event of an atrial arrhythmia with a cycle length of 240-280 milliseconds and irregular atrioventricular conductions. B: A device interrogation illustrating an event of an atrial arrhythmia with 1:1 atrioventricular conductions. C: A summary of the duration of the atrial tachycardia (AT)/atrial fibrillation (AF) burden and average or maximum heart rate during the AT/AF. D: The time course of the thoracic impedance.
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Instead, a number of atrial fibrillation (AF) or atrial tachycardia (AT) events were recorded by the pacemaker (Figure 2A). AT/AF events (Figure 2B). A cardiac compass report (Figure 2C) showed that the AT/AF persisted for about 61/2 months and terminated spontaneously. A medical interview with the patient proved that his dyspnea coincided with the first occurrences of the AT/AF events. According to the records of the thoracic impedance in his pacemaker, it markedly decreased also soon after the beginning of the AT/AF events (Figure 2D).
An intracardiac recording during atrial pacing. Wenckebach periodicity was seen at an atrial pacing cycle of 720 milliseconds.
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The Wenckebach cycle length was determined to be 720 milliseconds (Figure 3), and the AV nodal effective refractory period was found to be 620 milliseconds.