Reproducibility of clinical and hemodynamic parameters during pacing stress testing in patients with angina pectoris.

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Abstract
The reproducibility of clinical and hemodynamic events during 2 successive pacing periods separated by a 20 min interval was evaluated in 33 patients with stable angina pectoris. Continuous pacing with stepwise increase in pacing rate was assessed in 19 patients and discontinuous pacing, in which pacing was temporarily interrupted at each rate, was evaluated in the other 14 patients. During continuous pacing, the group values for pacing rates that induced angia, the pacing time to angina, ST-segment depression, rate-pressure product, cardiac output and left ventricular end-diastolic pressure (LVEDP) were similar during the 2 pacing periods, but postpacing LVEDP was lower after the 2nd pacing period (P < 0.05). During the 2nd pacing period, angina could not be reproduced at the same pacing rates in 4 patients and postpacing LVEDP varied by 5 mm Hg or more in 10 of the 19 patients. During discontinuous pacing, the group mean values for pacing rates that induced angina and the pacing time to angina were higher (P < 0.05), and cardiac output lower (P < 0.05) during the 2nd pacing period; rate-pressure product, ST-segment depression and LVEDP were similar during the 2 pacing periods. During the 2nd pacing study angina could not be induced at the same pacing rates in 6 patients and the postpacing LVEDP varied by 5 mm Hg or more in 3 of the 14 patients. Continuous pacing is preferable to discontinuous pacing. With continuous pacing, the group values for the clinical and many of the hemodynamic parameters were reproducible. Demonstration of the reproducibility of events during pacing is recommended in studies in which the effects of therapeutic interventions are being assessed, especially in a small number of patients.