Sustained ventricular tachycardia (VT) developed in a 63-year-old woman. The 2-dimensional echocardiogram revealed left mid-ventricular obstructive hypertrophy and a discrete apical chamber. A continuous wave Doppler signal across the mid-ventricular narrowing exhibited early systolic ejection flow and diastolic paradoxical jet flow from the apex to the basal chamber, implying a significant systolic and diastolic intraventricular gradient with a high apical pressure. The left ventriculogram confirmed a mid-ventricular obstruction with an apical aneurysm. Invasive assessment of intraventricular pressure showed a peak-to-peak gradient greater than 100 mmHg. Treatment with antiarrhythmic agents could not prevent the VT, but dual-chamber pacing reduced the intraventricular pressure gradient and suppressed the VT completely. Continuous wave Doppler showed that the early systolic ejection flow from the apex had disappeared, that there was isovolumetric relaxation flow toward the apex and that there was attenuation of the diastolic paradoxical jet flow toward the basal chamber. Such findings by continuous wave Doppler can be useful in pacing therapy for evaluating changes in the severity of mid-ventricular obstruction.