Figure 1.

Disopyramide‐induced electrocardiographic changes. Electrocardiograms of a 53‐year‐old man with hypertrophic cardiomyopathy and left ventricular outflow tract gradients of up to 90 mm Hg. He suffered from exertional shortness of breath despite trials of beta‐blockers and calcium‐channel blockers. After initiation of disopyramide and increase in dose to 600 mg daily, his symptoms resolved and gradients diminished to 15 mm Hg. Electrocardiograms were recorded before disopyramide and while on 300 and 600 mg daily. Heart rate and QRS interval showed no significant change after disopyramide initiation. The PR interval was 180 ms at baseline, prolonged minimally on 300 mg and to 200 ms on 600 mg. The corrected QT interval was 378 ms at baseline, prolonged to 426 ms on 300 mg and remained without significant change (419 ms) after dose increase to 600 mg. Note the change in T‐wave morphology with a more‐rounded peak on disopyramide.