Background: pharmacological stress tests using dipyridamole is considered to be safe. However, side effect can occur. Case reports of atrio-ventricular (AV) block were reported.
Objective: to summarize the cases of AV block during dipyridamole infusion and to evaluate the presence of risk factors
Methods: All consecutive patients who underwent pharmacological stress tests using dipyridamole during the last eight months were included. Patients with pacemakers, second or third degree AV block were excluded. Dipyridamole was infused during 4 minutes’ followed by 2 min low velocity physical exercise. Tc99-MIBI was injected 3 min past the cessation of Dipyridamole infusion. Intravenous aminophylline was used whenever side effects occurred. All patients underwent Myocardial perfusion SPECT that was performed using a single day single isotope pharmacological stress test protocol using 0.21 MBq (8 mCi) Tc99m-MIBI for rest and 0.68 MBq (25 mCi) for stress.
Results: The study included 942 consecutive patients. At baseline, 314 (33%) had conduction abnormality ,including first degree AV block, left bundle branch block (LBBB), right bundle branch block (RBBB), and/or intra-ventricular conduction delay. Only 6 (0.6%) patients developed transient AV block that resolved immediately after administration of intravenous aminophylline, all of them had normal myocardial perfusion scan . Two patient without conduction abnormality developed asymptomatic type I second degree and complete AV block . One patient with complete RBBB at baseline developed asymptomatic 2:1 second degree AV block. Two patient with complete LBBB at base line developed asymptomatic complete AV block and 2:1 second degree AV block. One patient with atrial fibrillation and normal QRS width had syncope due to asystole that lasted for ten seconds.
Conclusion: transient AV block occur rarely after dipyridamole infusion and is asymptomatic in the vast majority of cases. It seems that the presence of conduction abnormality or atrial fibrillation at base line is a risk factor.
