Quinidine: Long QT Interval
Report:
Sinus rhythm 82/min
Widespread T wave inversion
Prolonged QT interval 0.62â
QTc for 82/min = 0.37â
Comment:
This degree of QT prolongation is unusual. The prolongation is idiosyncratic in susceptible individuals and bears little relation to quinidine levels or concomitant QRS broadening. I was taught that 30% increase in QRS width is still in therapeutic range, while 50% increase indicates toxicity. Later, blood levels came to be measured; then the drug was abandoned.
In this patient, T wave inversion is, again, more than what one would expect from quinidine ± digoxin alone; it may reflect post-tachycardia changes or, most likely, underlying heart disease.
194. 45 year old lady with persistent severe central chest pains over 10 days. What did the coronary angiography show?
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