Which ECG change most reliably indicates quinidine toxicity?
Prolonged QT interval
Quinidine is a class Ia antiarrhythmic that slows phase 0 depolarisation and prolongs ventricular repolarisation. The most reliable ECG marker of quinidine toxicity is prolongation of the QT interval, which may progress to torsades de pointes ventricular tachycardia.
Shortened PR, peaked T waves (hyperkalaemia) and 'scooped' ST depression (digitalis effect) are produced by other causes, not by quinidine toxicity.
Hence, Prolonged QT interval.
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Important Questions from Pharmacology
During ECG monitoring, which drug is most likely to cause bradycardia?
During high-dose vasopressor therapy, which ECG change most reliably indicates supply–demand ischemia due to increased afterload?
Which type of stress test involves the use of medication instead of physical exercise?
What is the most appropriate initial management for a patient presenting with symptomatic bradyarrhythmia?
What ECG change might be seen after administration of calcium channel blockers?
