High Grade AV Block Associated with Dipyridamole Infusion

The use of dipyridamole for thallium imaging has proved very successful in demonstrating coronary arterial disease [1]. Dipyridamole causes coronary arteriolar vasodilation by increasing interstitial adenosine levels by inhibition of both adenosine deaminase and facilitated cellular adenosine uptake. Differential flow changes occur in coronary arteries if a significant luminal stenosis exists [2]. Intravenous infusion of dipyridamole is safe although transient noncardiac side effects are common. These side effects are mostly mild and not need to treat although can be treated with aminophylline [5]. High-grade AV block after dipyridamole has been described in few case reports and mostly was associated with transient myocardial ischemia [2-4]. We describe a case of long-lasting high grade AV block following dipyridamole infusion. In context of near normal baseline ECG. In our case the AV block occurred without evidence of ischemia in myocardial perfusion imaging and we think it can be an unexpected adverse effect of dipyridamole and clinicians should be aware of AV block as a possible adverse effect of dipyridamole.