Radionuclide ejection fraction and regional wall motion during atrial pacing in stable angina pectoris: Comparison with metabolic and hemodynamic parameters

To evaluate the effects of atrial pacing on radionuclide (RNA) ejection fraction (EF) and regional wall motion (RWM), transmyocardial lactate gradients and hemodynamics in stable coronary artery disease (CAD), 12 CAD patients underwent incremental atrial pacing during cardiac catheterization. EF declined from 0.60 ± 0.07 during control state to 0.51 ± 0.11 (p < 0.001) during submaximal pacing (Sub Max P) with 10 of 12 having decreased EF, six developing new RWM abnormalities, and five experiencing mild chest pain. During maximal pacing (Max P), EF declined further to 0.47 ± 0.10 (p < 0.001), with all patients having decreased EF and experiencing moderate to severe chest pain, and nine developing new RWM abnormalities. Percentage lactate extraction (Ex) decreased from +28.3 ± 9.4% to +17.4 ± 11.9% during Sub Max P (p < 0.01), with only one patient producing lactate. During Max P, percentage lactate Ex decreased to ?0.1 ± 15.3% (p < 0.001) with eight patients producing lactate. Significant increases in pulmonary capillary wedge pressure and systemic vascular resistance occurred during Max P, and in mean pulmonary artery pressure and mean systemic arterial pressure during both Sub Max and Max P. Significant decreases in stroke volume index and stroke work index occurred during both pacing levels and cardiac index did not change with pacing. This study demonstrates that RNA may be used to establish decreases in EF and RWM which occur in response to incremental atrial pacing in patients with stable CAD, and that these changes are more consistent and appear earlier than the metabolic consequences of myocardial ischemia induced by pacing stress.