PATIENTS WITH STABLE CHRONIC OBSTRUCTIVE PULMONARY-DISEASE CAN SAFELYUNDERGO INTRAVENOUS DIPYRIDAMOLE TL-201 IMAGING

Background Patients with chronic obstructive pulmonary disease are usu ally excluded from intravenous dipyridamole thallium-201 testing. We d eveloped a nurse-administered protocol to screen and pretreat patients so they could be safely tested. Methods and Results We prospectively screened patients referred for intravenous dipyridamole thallium testi ng and retrospectively reviewed a comparison group of patients who had undergone intravenous dipyridamole testing before our bronchospasm pr otocol. We studied 492 consecutive patients referred for intravenous d ipyridamole thallium testing, separating those with complete data (n = 451) into two groups: group A (n = 72), patients assessed to be at ri sk for intravenous dipyridamole induced bronchospasm who received our bronchospasm treatment protocol; and group B (n = 379), patients asses sed to be free of risk, who did not receive our bronchospasm protocol. Group C (n = 89) was a retrospective comparison group of patients who had undergone intravenous dipyridamole testing before initiation of t he protocol. Patients were considered at risk for an adverse event if any of the following were present: peak flow less than or equal to 400 ml at the time of the test (spirometry by nurse) that increased to >4 00 ml after bronchodilator treatment, wheezing audible with stethoscop e, history of chronic obstructive pulmonary disease or asthma or dyspn ea on exertion at less than four blocks, or resting respiratory rate > 18 breaths/min. The test was considered contraindicated if resting oxy gen saturation was <85%, respiratory rate greater than or equal to 36 breaths/min, or peak flow measured by peak flowmeter <400 ml after bro nchodilator inhalant (albuterol or metaproterenol sulfate by spacer) a t a dose of up to six puffs. One minute after injections of thallium-2 01, patients at risk were given 50 mg aminophylline by slow intravenou s injection. We looked for major and minor adverse effects and divided them into three categories: (1) minor events (transient headache, abd ominal discomfort, or nausea), wheezing (audible by stethoscope but wi thout marked respiratory distress), (2) marked events (severe bronchos pasm or severe ischemia defined as wheezing audible with or without st ethoscope, respiratory rate >20 breaths/min or increased by 10 from pr etest evaluation, oxygen desaturation to <90%, hypoventilation [reduce d respiratory rate with decreased mental status], respiratory arrest, chest pain, horizontal ST-segment depression greater than or equal to 1 mm on the electrocardiogram in any lead, symptomatic hypotension), o r (3) other intravenous dipyridamole-induced side effects (persistent headache, dizziness, flushing, nausea, dyspnea, and ischemic chest pai n) or anginal equivalent. The protocol properly identified patients wi th impaired pulmonary function. There was no difference in the frequen cy of adverse marked events among groups A, B, or C (1% vs 4% vs 2%, p = 0.25). Patients in group A had more minor side effects than those i n group B (53% vs 35%, p = 0.004). Specifically, patients in group A w ere more likely to wheeze (39% vs 1%, p = <0.001), but wheezing in gro up A was self-limited or responded to treatment as described in the pr otocol. The prevalence of positive thallium-201 scans in group A (44%) compared with group C (49%) was not different (p = 0.15). Conclusions A nurse-administered risk assessment and pretreatment protocol (1) pr operly identified patients with impaired pulmonary function, (2) permi tted completion of intravenous dipyridamole testing in patients at ris k for bronchospasm without an increased incidence of marked adverse ev ents, and (3) did not appear to influence the interpretation of the th allium test.