山田 聡¹, 岩野 弘幸¹, 小室 薫², 岡田 昌子¹, 小松 博史¹, 加賀 早苗³, 西田 睦³, 小野塚 久夫⁴, 三神 大世⁴, 筒井 裕之¹

Satoshi YAMADA¹, Hiroyuki IWANO¹, Kaoru KOMURO², Masako OKADA¹, Hiroshi KOMATSU¹, Sanae KAGA³, Mutsumi NISHIDA³, Hisao ONOZUKA⁴, Taisei MIKAMI⁴, Hiroyuki TSUTSUI¹

¹北海道大学大学院医学研究科循環病態内科学, ²国立病院機構函館病院臨床研究部, ³北海道大学病院検査・輸血部, ⁴北海道大学大学院保健科学研究院

¹Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, ²Department of Clinical Research, Hakodate National Hospital, ³Division of Clinical Laboratory and Transfusion Medicine, Hokkaido University Hospital, ⁴Faculty of Health Sciences, Hokkaido University

キーワード : blood volume, contractile reserve, contrast agent, dilated cardiomyopathy, myocardial contrast echocardiography

目的：心筋コントラストエコー法（MCE）により計測される左室の心筋内血液量が，拡張型心筋症（DCM）患者の左室機能または左室収縮予備能と関連するか否かを検討すること．対象と方法：対象は，左室駆出率（LVEF）が45％未満のDCM患者21例．超音波造影剤Levovist^®の持続静注下に，6心拍ごとの間歇送信法を行い心尖部二腔断面と四腔断面のハーモニック・パワードプラ画像を記録した．左室を6区域に分割し，心筋のコントラスト強度（CI_myo）と心筋に隣接する左室内腔血液のコントラスト強度（CI_blood）を計測した．相対的CI（RelCI）＝CI_myo−CI_blood ［dB］は，内腔血液に対する心筋の気泡密度の比率を対数で表し，心筋内血液量は10^{（RelCI/10）}×100 ［％］と算出される．20μg/kg/minまでのドブタミン負荷心エコー法で負荷前と最大用量負荷時のLVEFを計測した．結果と考察：心筋内血液量はLVEFを含めた安静時の心機能指標とは相関せず，ドブタミン負荷によるLVEFの増加率と有意に相関した（r＝0.54，p＝0.01）．DCMによる心筋の組織形態学的変化に伴って，心筋内血管の相対的容積が減少し，そのことが収縮予備能の低下に関連していると考えられる．結論：MCEにより計測される心筋内血液量は，DCM患者の左室収縮予備能と関連した．

Purpose: To elucidate whether myocardial blood volume is associated with resting left ventricular (LV) function and/or contractile reserve in patients with dilated cardiomyopathy (DCM) using myocardial contrast echocardiography (MCE). Subjects and Methods: Twenty-one patients with DCM who had LV ejection fraction (LVEF)myo) and the contrast intensity of the adjacent intracavity blood pool (CI_blood) were measured. Relative CI (RelCI), calculated as CI_myo-CI_blood [dB], logarithmically represents the ratio of microbubble concentrations between the myocardium and blood pool. Myocardial blood volume can be derived as 10^(RelCI/10)×100 [%]. Dobutamine stress echocardiography (up to 20 μg/kg/min) was performed, and LVEF was measured at baseline and at peak dose. Results and Discussion: Myocardial blood volume did not correlate with any parameters of resting LV function, but it significantly correlated with percent change in LVEF during dobutamine stress echocardiography (r0.54, p0.01). Myocardial histomorphometric features in patients with DCM conceivably cause the reduction in myocardial blood volume, being related to the depressed contractile reserve. Conclusion: Myocardial blood volume measured by MCE was associated with LV contractile reserve in patients with DCM.