Carbon Dioxide in the Aortic Arch: Coronary Effects and Implications in a Swine Study

Purpose: CO₂ angiography is considered dangerous in the aortic arch where bubbles may cause critical cerebral and cardiac ischemia. We investigated CO₂ distribution, physiologic effects in the heart, methods of detection and treatments. Methods: Eight pigs had CO₂ and iodinated contrast arch angiograms in supine and both lateral decubitus positions. An electrocardiogram, physiologic data and cardiac ultrasound were obtained. Therapies included precordial thumps and rolls to lateral decubitus positions. Results: Supine high descending aorta CO₂ injections floated retrograde up the arch during diastole and preferentially filled the right coronary artery (RCA): mean score 3.5 (of 4), innominate artery 2.4, left coronary artery 1.2; n = 17; p = 0.0001. Aortic root injections preferentially filled the RCA when the animal was supine, left coronary in the right decubitus position, and showed a diffuse pattern in the left decubitus position. Right decubitus rolls filled both coronaries causing several lethal arrhythmias. Precordial thumps successfully cleared CO₂. Ultrasound is a sensitive detector of myocardial CO₂. Conclusion: Arch distribution of CO₂ primarily involves the RCA. Diagnostic ultrasound detects cardiac CO₂ well. Precordial thumps are an effective treatment.