心房中隔欠損症における心エコー肺体血流量比の精度に関する検討

Mihoka Iwazaki; 岩崎美穂香; Hiroyuki Toide; 戸出浩之; Hiroki Okaniwa; 岡庭裕貴; Kiyoko Yoshizumi; 吉住聖子; Tomomi Araseki; 荒関朋美; Yasuyuki Kobayashi; 小林康之; Eiji Yamashita; 山下英治

心房中隔欠損症における心エコー肺体血流量比の精度に関する検討A Study on the Accuracy of Pulmonary to Systemic Flow Ratio by Echocardiography in Patients with Atrial Septal Defect

岩崎美穂香¹，戸出浩之¹，岡庭裕貴¹，吉住聖子¹，荒関朋美¹，小林康之¹，山下英治²Mihoka Iwazaki¹, Hiroyuki Toide¹, Hiroki Okaniwa¹, Kiyoko Yoshizumi¹, Tomomi Araseki¹, Yasuyuki Kobayashi¹, Eiji Yamashita²

¹ 群馬県立心臓血管センター技術部Division of Medical Techniques, Gunma Cardiovascular Center ◇ 〒371-0004 群馬県前橋市亀泉町甲3番地12Ko-3-12 Kameizumi-machi, Maebashi-shi, Gunma 371-0004, Japan

² 群馬県立心臓血管センター循環器内科Department of Cardiology, Gunma Cardiovascular Center ◇ 〒371-0004 群馬県前橋市亀泉町甲3番地12Ko-3-12 Kameizumi-machi, Maebashi-shi, Gunma 371-0004, Japan

受付日：2015年3月19日Received: March 19, 2015

受理日：2015年10月9日Accepted: October 9, 2015

発行日：2015年12月1日Published: December 1, 2015

目的：パルスドプラ法（Echo法）の肺体血流量比（Qp/Qs）の計測精度を明らかにすること．

対象と方法：Echo法とFick法を施行した心房中隔欠損症31例（53±18歳，M=11例）を対象に，両法のQp/Qsを比較した．また，両法の誤差20%を境として，一致群，Echo法の過小評価群，過大評価群に区分し，各群の左室および右室流出路径（LVOTd, RVOTd），およびこれらの体表面積補正値，左室および右室流出路血流時間速度積分値（LVOT TVI, RVOT TVI）を比較した．さらに，右室流出路長軸断面右室流出路拡大像における，RVOTdと超音波ビームのなす角度（RVOTd計測角度）についても追加検討した．

結果と考察：両法の相関は良好であった（r=0.70, p<0.01）．一致群と比較して，過小評価群はRVOTd indexが有意に小であり（p<0.05），過大評価群はRVOTdが有意に大（p<0.01），RVOTd indexが有意に大であった（p<0.05）．RVOTd計測角度は一致群と比較して，過小評価群，過大評価群ともに有意に大であった（ともにp<0.01）．これらより，Echo法ではRVOT壁が超音波ビームに対して平行に描出されることで，特に側壁の描出が不鮮明となることや種々のアーチファクトにより，RVOTdに計測誤差が生じると考えられた．

結語：Echo法では，RVOTd計測時に超音波ビームがRVOT壁に可及的に直交するように描出することで計測精度が向上する可能性が考えられた．

Purpose: To clarify the measurement accuracy of pulsed-Doppler method (Echo method) in pulmonary to systemic flow ratio (Qp/Qs) in patients with atrial septal defect (ASD).

Subjects and Methods: We enrolled 31 consecutive ASD patients who underwent the Echo and Fick method (53±18 years, 11 males). According to Qp/Qs values obtained by two methods, the patients were divided into 3groups: match-group (Within 20% of the difference of Qp/Qs between Echo and Fick method, n=18), underestimate-group (more than 20% lower Qp/Qs by Echo method, n=6) and overestimate-group (more than 20% higher Qp/Qs by Echo method, n=7)．LVOT and RVOT diameter (RVOTd), and body surface revision level of each measurement item, left and right ventricular ejection bleeding flow time speed integral value, and the angle formed by RVOTd and ultrasonic beam in RVOTd measurement cross section (RVOTd measurement angle) were compared among 3 groups.

Results and Discussion: In overall, good correlation was observed between Qp/Qs by Echo and Fick method (r=0.70, p<0.01). Four patients (67%) of underestimate-group showed Qp/Qs values of 3 to 4 (3≤Qp/Qs<4) by Fick method. Five patients (71%) of overestimate-group had Qp/Qs values of 2 to 3 (2≤Qp/Qs<3) by Fick method. Compared with the match-group (3≤Qp/Qs<4: 17.4±2.0 mm/m², 2≤Qp/Qs<3: 19.3±1.3 mm/m²), RVOTd indexed by body surface area was significantly lower in underestimate-group (14.6±0.9 mm/m², p<0.05), and larger in overestimate-group (22.7±3.7 mm/m², p<0.05). Compared to the match-group (31.9±17.1 degree), both underestimate- and overestimate-group showed larger RVOTd measurement angle (65.0±4.5 degree, p<0.01, 63.6±11.8 degree, p<0.01), which suggests that ultrasound beam parallel to RVOT wall could induce larger measurement error of RVOT diameter due to lower lateral resolution than axial resolution or various artifacts.

Conclusion: In the measurement of RVOT, ultrasound beam perpendicular to RVOT wall could provide higher accuracy of Qp/Qs.

キーワード：心房中隔欠損症；肺体血流量比；パルスドプラ法；Fick法

Key words: atrial septal defect (ASD); pulmonary to systemic flow ratio (Qp/Qs); pulsed-Doppler method; Fick method

超音波検査技術

学術賞－研究Researcher's Award - Research Paper

心房中隔欠損症における心エコー肺体血流量比の精度に関する検討A Study on the Accuracy of Pulmonary to Systemic Flow Ratio by Echocardiography in Patients with Atrial Septal Defect