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

Abstract

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 marker of autonomic dysfunction in patients with diabetes, has not been fully elucidated. One hundred two consecutive diabetic patients undergoing dual-isotope (rest Tl-201/dipyridamole stress Tc-99m tetrofosmin) MPS were prospectively enrolled. A reduced HR response to dipyridamole was considered present if the ratio between maximal HR after dipyridamole infusion and rest HR was <or=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 HR response to dipyridamole. A reduced HR response to dipyridamole was found in 46.1% of the patients and was associated with the presence of chronic renal failure (chi2 = 6.4), with high baseline HR (chi2 = 4.7) and low poststress LVEF (chi2 = 10.6). Attenuation of the HR response to dipyridamole was frequent and was strongly associated with reduced LVEF. Autonomic dysfunction may be reflected in the higher baseline HR but should not be considered the sole mechanism accounting for the reduction in HR response to dipyridamole in patients with diabetes.