Dual Conduction and SVT

Report:

Sinus rhythm

Dual PR interval: 0.14” and 0.30”

Comment:

The two PR intervals alternated over periods of minutes, finally attracting the attention of the ICU night staff. Unfortunately, no spontaneous change was recorded.

In the morning, I gave him 0.6 mg atropine IV; with minimum acceleration of the heart rate, he decreased his PR interval to normal (lower strip). By now he was well and ready to be discharged from the ICU; attempts to recall the long PR interval (by carotid massage and Valsalva manœuvre) and record the transition failed and he left.

The dual pathway was possibly unmasked by the patient’s diabetic autonomic neuropathy. It is not rare, but is rarely observed. There is little doubt that it was the substrate for his SVT.

His 12-lead ECGs, apart from episodes of SVT (Fig 102b), showed different PR intervals at different times but no other abnormality.

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