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Puzzle 2009 04 Answer: Difference between revisions
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==Answer== | ==Answer== | ||
Indeed, the heart rhythm is irregular. The P wave morphology is abnormal with negative P waves in the inferior leads, an almost negative P wave in lead I and a positive P wave in lead aVR. This indicates a lower left atrial origin. The cycle length of this rhythm is 640 | |||
ms (rate slightly lower than 100 beats/min). The wide intervals on the ECG result from a blocked atrial impulse every fourth beat. The block is at the level of the origin of the atrial impulse, i.e. an exit block of the focal impulse. Atrioventricular and ventricular conduction are normal. Repolarisation is abnormal and might be explained by the use of digoxin. Atrial tachycardia with AV block might be seen in the setting of toxic digoxin concentrations but in this case the level of block is not at the atrioventricular junction. So, there is no reason to consider this cause. | |||
Electrical cardioversion could bring this abnormal rhythm back to normal sinus rhythm. | |||