The triple rule-out for acute ischemic stroke: imaging the brain, carotid arteries, aorta, and heart

Abstract

Background and purpose: Ischemic stroke is commonly embolic, either from carotid atherosclerosis or from cardiac origin. These potential sources of emboli need to be investigated to accurately prescribe secondary stroke prevention. Moreover, the mortality in ischemic stroke patients due to ischemic heart disease is greater than that of age-matched controls, thus making evaluation for coronary artery disease important in this patient population. The purpose of this study was to evaluate the image quality of a comprehensive CTA protocol in patients with acute stroke that expands the standard CTA coverage to include all 4 chambers of the heart and the coronary arteries.

Materials and methods: One hundred twenty patients consecutively admitted to the emergency department with suspected cerebrovascular ischemia undergoing standard-of-care CTA were prospectively enrolled in our study. We used an original tailored acquisition protocol using a 64-section CT scanner, consisting of a dual-phase intravenous injection of iodinated contrast and saline flush, in conjunction with a dual-phase CT acquisition, ascending from the top of the aortic arch to the vertex of the head, then descending from the top of the aortic arch to the diaphragm. No beta blockers were administered. The image quality, attenuation, and CNRs of the carotid, aortic, vertebral, and coronary arteries were assessed.

Results: Carotid, aorta, and vertebral artery image quality was 100% diagnostic (rated good or excellent) in all patients. Coronary artery image quality was diagnostic in 58% of RCA segments, 73% of LAD segments, and 63% of LCX segments. When we considered proximal segments only, the diagnostic quality rose to 71% in the RCA, 83% in the LAD, and 74% in the LCX.

Conclusions: Our stroke protocol achieved excellent opacification of the left heart chambers, the cervical arteries, and each coronary artery, in addition to adequate carotid and coronary artery image quality.

Fig 1.

Stroke CT protocol design. A bolus of 30 cc of contrast was injected into the right or left cubital vein, followed by a 15 cc saline flush, both at an injection rate of 5 cc per second. The first acquisition (1) (not ECG gated) ascends from the aortic arch origin to the vertex of the head, taking place after a delay determined from perfusion CT used as a bolus test, typically 15 seconds. A second bolus (2) of 60 cc of contrast was injected 3 seconds later and followed by a 60 cc saline flush, again at an injection rate of 5 cc per second. The second acquisition descends from the aortic arch origin to the diaphragm and is ECG gated.

Fig 2.

Study participants. One hundred twenty consecutive patients receiving standard-of-care stroke CT evaluation were prospectively enrolled in our study. Five patients were excluded because of CABGs. In 79 patients, both the carotid and cardiac portions of the CTA succeeded. In 36 patients, the carotid portion succeeded, but the cardiac portion failed. Fifteen of these 36 failures were directly related to our protocol, 7 were related to patient size, and 14, to technical issues. The 21 cases in which failure was unrelated to our protocol were excluded, and our image-quality analysis was performed on the remaining 94 patients.

Fig 3.

A, Segment-level analysis of coronary artery image quality. Each coronary artery segment was given an image-quality score (0 = excellent, 1 = good, and 2 = nondiagnostic). The nondiagnostic segments were separated into 3 categories: motion artifacts, poor contrast, and streak artifacts. Those segments that were nondiagnostic due to tiny vessel size, heavy calcification, or pacemaker artifacts were excluded because they were nondiagnostic for reasons not directly related to our protocol. B, Vessel-level analysis of coronary artery image quality. A coronary artery was considered excellent if the entire artery was diagnostic, good if 1 or 2 segments were diagnostic, and nondiagnostic if no segments were diagnostic. Those segments that were nondiagnostic for reasons unrelated to our protocol (ie, tiny vessel size, heavy calcification, or pacemaker artifacts) were omitted from this analysis. C, Patient-level analysis of coronary artery image quality. Cardiac examinations that were 75%–100% diagnostic were considered excellent, cardiac examinations that were 50%–74% diagnostic were considered good, and cardiac examinations that were 0%–49% diagnostic were considered failed. Most patients (65%, n = 61) had cardiac examinations that were 75%–100% diagnostic. Nondiagnostic segments in the failed cases were primarily due to motion artifacts.