Xylocaine and the δ Wave
Report:
Sinus tachycardia
Wolff-Parkinson-White conduction
Transient normal conduction following injection of 50 mg xylocaine
Comment:
This patient with postural hypotension ( 90 mmHg drop!) and on multiple medications, was seen in consultation with view to simplifying his treatment. When frusemide, procainamide, chlorpromazine and a tricyclic antidepressant were stopped, his pulse rate slowed down and WPW pattern emerged. Xylocaine was used to assess his bundle of Kentâs responsiveness to it and obtain a repeat 12-lead ECG without pre-excitation.
Patients with intermittent pre-excitation are less at risk from atrial fibrillation or flutter with very rapid ventricular rates. A strip with only occasional δ waves is shown below (Fig 16a). A suggestion of the concertina effect is seen between the 3rd and the 6th beat in the top strip.
Fig 16a. The PR interval gets gradually longer and the QRS slimmer between the 3rd and the 6th beat in the top strip. Anomalous conduction is not always all-or-nothing phenomenon.
Fig 17. 70 year old woman with remote myocardial infarction and unstable angina. Chest X-ray shows marked cardiomegaly.
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