Reduced Heart Rate Response to Dipyridamole as a Marker of Left Ventricular Dysfunction in Diabetic Patients Undergoing Myocardial Perfusion Scintigraphy

Purpose of the Report: This study sought to find among clinical, hemodynamic and left ventricular perfusion and function data obtained from myocardial perfusion scintigraphy (MPS), those associated with a reduced heart rate (HR) response to dipyridamole in diabetic patients. This phenomenon, although previously described as a market of autonomic dysfunction in patients with diabetes, has not been fully elucidated. Materials and Methods: One hundred two consecutive diabetic patients undergoing dual-isotope (rest TI-201/dipyridamole stress Tc-99m tetrofosmin) MPS were prospectively enrolled. A reduced FIR response to dipyridamole was considered present if the ratio between maximal FIR after dipyridamole infusion and rest FIR was <= 1.20. MPS images were interpreted semiquantitatively, and perfusion scores were calculated. Left ventricular ejection fraction (LVEF) was automatically obtained. A logistic regression analysis was used to find variables independently associated with a reduced FIR response to dipyridamole. Results: A reduced HR response to dipyridamole was found in 46.1% of the patients and was associated with the presence of chronic renal failure (chi(2) = 6.4), with high baseline FIR (chi(2) = 4.7) and low poststress LVEF (chi(2) = 10.6). Conclusions: Attenuation of the FIR response to dipyridamole was frequent and was strongly associated with reduced LVEF. Autonomic dysfunction may be reflected in the higher baseline FIR but should not be considered the sole mechanism accounting for the reduction in FIR response to dipyridamole in patients with diabetes.