The safety of adenosine pharmacologic stress testing in patients with first-degree atrioventricular block in the presence and absence of atrioventricular blocking medications.

BACKGROUND: Pharmacologic stress testing in conjunction with radionuclide myocardial perfusion imaging may be used in the diagnosis of coronary artery disease and risk assessment. Adenosine can cause atrioventricular nodal (AV) block during infusion. In this study, we evaluated whether patients with baseline first-degree AV block could safely undergo adenosine stress testing.

METHODS AND RESULTS: We evaluated the frequency of second- and third-degree AV block in patients with baseline first-degree AV block during adenosine stress testing, in the presence and absence of AV blocking medications (digitalis, beta-blockers, diltiazem, verapamil). Six hundred consecutive patients underwent pharmacologic stress myocardial perfusion imaging with adenosine infusion at 140 microg/kg/min for 6 minutes. A total of 43 patients (7.16%) had baseline first-degree AV block (PR interval > 200 msec), and 557 patients had a baseline PR interval < 200 msec. Twenty-one of the 43 patients (48.8 %) had further prolongation of PR interval > 240 msec, compared with 58 of 557 patients (10.4%) in the control group (P < .0001). In 16 of the 43 patients (37.3 %), second-degree AV block developed, compared with 45 of 557 patients (8.0 %) in the control group (P < .0001). In 6 of the 43 patients (13.9%), third-degree AV block developed, compared with 6 of 557 patients (1.0%) in the control group (P < .0001). All types of AV block were short duration and were not associated with any specific symptoms. None of these episodes required specific treatment. The presence of AV blocking medications (digitalis, beta-blockers, diltiazem, verapamil) did not increase the incidence of AV block during adenosine infusion.

CONCLUSION: In patients with baseline PR interval of more than 200 msec, the frequency of second- and third-degree AV block during adenosine stress testing was significantly higher than in patients with a normal baseline PR interval. AV blocking medications did not increase the incidence of second- and third-degree AV block during adenosine stress testing. We conclude that it is safe to perform adenosine pharmacologic stress testing in patients with baseline PR prolongation.