The usefulness of electrophysiological-pharmacologic studies in the long-term therapy of paroxysmal tachycardias.

In 96 cases of paroxysmal tachycardia, results of chronic pharmacological assessment (CPA) were compared with acute electrophysiological-pharmacologic assessments (EPA) to evaluate the usefulness of EPA. I. Patients with sustained VT (31 cases): Sustained VT and repetitive ventricular response (RVR) could be induced in 61% and 23% respectively. More than one effective drug was found by EPA for 23 of 24 subjects. Of the 22 followed by CPA, the effectiveness of medication was excellent for 14 (64%), moderate for 1, slight for 4, and ineffective for 3 (14%). II. Patients with non-sustained VT (23 cases): RVR could be induced in 52%. Effective medication was identified by EPA for 8 of 10 patients. Of the 7 followed by CPA, the effectiveness of medication was excellent for 2(28.5%) moderate for 2, and ineffective for 3. III. Patients with PSVT (42 cases): PSVT could be induced in 90% of cases. Effective medication was found for all 31 cases which underwent EPA. Of the 23 cases followed by CPA, the chronic efficacy of drugs was excellent for 7 (30%), moderate for 5 (22%), slight for 7 (30%), and noneffective for 4 (18%). Therefore, we conclude that the usefulness of EPA differs according to the type of tachycardia. EPA is most useful in predicting chronic results for patients with sustained VT, especially when the sustained VT is readily reproducible by electrical stimulation. It is less useful for nonsustained VT and PSVT. With nonsustained VT, EPA is limited by difficulty in repeatedly inducing RVR, and by difficulty in predicting the appropriate medication for chronic oral therapy. With PSVT, even though the PSVT can be induced with greater success, EPA is limited by variations in pharmacologic effects over time, which create discrepancies between EPA and CPA.