Background: Changes induced by dipyridamole infusion on left ventricular function in healthy individuals have not been investigated by gated myocardial perfusion single photon emission computed tomographic (SPECT) imaging.
Methods and results: This study examined the amplitude and duration of changes induced by dipyridamole infusion on left ventricular function as assessed by technetium 99m sestamibi gated SPECT in 18 subjects with a low likelihood of coronary artery disease. Twenty mCi (740 MBq) of Tc-99m sestamibi were injected at rest. Three different consecutive gated SPECT images were performed 60 minutes later: baseline at rest, during the infusion of 0.76 mg/kg of dipyridamole, and 1 hour later. No patient received aminophylline. Left ventricular ejection fraction (LVEF), end-diastolic volume, and end-systolic volume were automically computed. Heart rate (HR) and blood pressure were regularly monitored. Mean LVEF was 63.2% +/- 8.0% baseline at rest, increased to 73.8% +/- 8.2% (P = .0001) during dipyridamole infusion, and returned to baseline values (63.0% +/- 7.5%) 1 hour later. End-diastolic volume did not vary significantly, and end-systolic volume decreased (from 32.2 +/- 19.5 to 26.6 +/- 17.9 u, P = .002) and returned to baseline values (32.7 +/- 15.6 u) 1 hour later. Dipyridamole induced moderate HR acceleration (from 80.2 +/- 15.0 to 96.5 +/- 9.6 beats/min, P < .001) and a slight decrease in diastolic blood pressure (from 80.6 +/- 8.1 to 70.1 +/- 9.0 mm Hg, P < .001). However, 1 hour later, HR and blood pressure had returned to baseline values.
Conclusions: Dipyridamole increases LVEF and HR and decreases diastolic blood pressure slightly in healthy individuals. Because dipyridamole gated SPECT imaging acquisition is usually started 60 minutes after dipyridamole infusion, LVEF is in fact estimated at rest.