P studies have established the feasibility of using the radial artery as an access route for percutaneous coronary interventions.1–3 This strategy, transradial coronary intervention (TCI), has several advantages over the conventional transfemoral and/or transbrachial interventions.4 In TCI, hemostasis is achieved easily by local compression because the radial artery is superficially located. Furthermore, because no major veins or nerves exist near the radial artery, risk of injury to such structures is negligible. These anatomic features significantly lower the risk of access site-related complications, and thus constitute the basis for considering the transradial route over the conventional transfemoral and/or transbrachial routes. The major drawback of TCI is the radial artery occlusion. Because radial artery occlusion can result in serious hand ischemia, it is necessary to ensure that collateral circulation from the ulnar artery is adequate to support the hand in the event of the radial artery thrombosis. The modified Allen’s test (AT) is often used to assess collateral blood supply to the hand.5–12 The results of this test are dependent on the change in hand color, the assessment of which is highly subjective and may seriously overestimate collateral blood supply. The present study investigated the feasibility of using color Doppler ultrasonography as an alternative to AT to assess the collateral supply to the hand before performing TCI. • • • The study cohort included 102 patients who were scheduled to undergo elective coronary interventions via the radial artery; 77 (76%) were men. The mean age was 65 6 10 years (range 41 to 84). Sixty-five patients (64%) had a history of myocardial infarction, and 11 (11%) had undergone coronary bypass surgery. Sixty-six patients (65%) had 1-vessel disease, and 36 (35%) had multivessel disease (Table I). When not contraindicated, patients received oral vasodilators including calcium channel blockers and nitrates at the time of AT and ultrasonographic assessment according to our institutional angioplasty protocol. Written informed consent was obtained from all patients before enrollment, and the institutional ethics committee approved the study protocol. All patients had a palpable radial artery pulse, and underwent the modified AT. Briefly, the patient was asked to repeatedly clench his or her fist to exsanguinate the hand while the examiner compressed both the ulnar and radial arteries. The fist was relaxed, and ulnar compression was released. The test was considered positive (normal) if an erythematous blush developed over the entire palm and the fingers within 10 seconds. This sign suggested adequate collateral blood supply from the ulnar artery to the area originally perfused by the radial artery. If the hand was not reperfused within 10 seconds, the test was considered negative, indicating that collaterals did not completely supply the area perfused by the radial artery. Ultrasonographic assessment of collateral blood supply to the hand was performed using a Sequoia 512 (Acuson, Mountain View, California) with an 8-MHz linear transducer. A consensus reading was reached by at least 2 investigators. With the patient at rest in the supine position, the Doppler probe was placed on the dorsal surface of the hand in the area between the thumb and forefinger (Figure 1A, left panel). The distal radial artery was visualized as it gave off branches to form the palmar arch (Figure 1B, upper left panel). While visualizing flow in the distal radial artery, the examiner compressed the radial artery at the level of the wrist (Figure 1A, right panel). When From the Departments of Medicine (Cardiology) and Clinical Laboratory, Teikyo University School of Medicine, Tokyo, Japan. Dr. Takeshita’s addrress is: Department of Medicine, Teikyo University School of Medicine, 2–11–1 Kaga, Itabashi, Tokyo 173–8605, Japan. E-mail: stake@blue.ocn.ne.jp. Manuscript received November 30, 1999; revised manuscript received and accepted February 8, 2000. TABLE I Demographics and Clinical Characteristics of Patients Evaluated for Transradial Coronary Intervention