鈴木 健吾

Kengo SUZUKI

聖マリアンナ医科大学循環器内科

Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine

キーワード : exercise stress echocardiography, ischemic heart disease, cardiomyopathy, valvular heart disease, pulmonary hypertension

負荷心エコー図は通常の心エコー図検査では明らかではない，“潜んでいる”所見を顕在化させ，労作時息切れの原因を明らかにできる可能性がある．負荷心エコー図における負荷の方法は大きく運動負荷と薬物負荷に分けられ，運動負荷では特に労作による自覚症状，血圧や心拍の反応，心電図変化（ST変化，不整脈），運動耐容能を客観的に評価することが可能である．負荷心エコー図は，各心疾患に応じて安静時と負荷時の心エコー図所見を評価する．虚血性心疾患では安静時と負荷時の局所壁運動をside by sideで比較しながら虚血の有無を評価する．拡張型心筋症では収縮予備能や左室同期不全，さらに機能性僧帽弁閉鎖不全の増悪を観察する．肥大型心筋症では運動負荷による左室流出路狭窄の程度を評価する．器質的僧帽弁閉鎖不全症では運動誘発性肺高血圧および運動耐容能を評価する．僧帽弁狭窄症では左房‐左室圧較差を評価し，負荷により増大する症例は軽度の僧帽弁狭窄症であってもカテーテル治療もしくは手術が推奨される．大動脈弁狭窄症では，運動負荷時左室-大動脈圧較差および運動誘発性肺高血圧の評価によりリスクの層別化を行い，ドブタミン負荷は低流量低圧較差大動脈弁狭窄症の診断に有用である．大動脈弁閉鎖不全症では，収縮予備能が大動脈弁置換術後の心機能低下と関連している．肺動脈性肺高血圧症では，運動誘発性肺高血圧の評価が早期診断に有用である．

The findings of stress echocardiography provide detailed diagnostic information in each cardiac disease. In ischemic heart disease, evaluation of left ventricular (LV) segmental wall motion at rest and with exercise determines the presence of ischemia. In dilated cardiomyopathy, systolic reserve, dyssynchrony, and functional mitral regurgitation (MR) are assessed. A poor prognosis has been reported in functional MR due to exercise-induced worsening. In hypertrophic cardiomyopathy, the LV outflow tract should be assessed because exercise often triggers LV outflow tract obstruction. In organic MR, exercise-induced pulmonary hypertension (PH) is assessed because many patients with exercise-induced PH reveal cardiac events and reduced exercise tolerance. The pressure gradient between the left atrium and ventricle is also evaluated in mitral stenosis; a high pressure gradient requires percutaneous transluminal mitral commissurotomy and/or surgical intervention even in mild mitral stenosis. The pressure gradient between the left ventricle and aorta during exercise and exercise-induced PH stratify risks for aortic stenosis. Stress echocardiography with dobutamine is useful in patients with reduced LV ejection fraction and those with paradoxical low-flow, low-gradient aortic stenosis. In aortic regurgitation, assessment of systolic reserve is recommended even in patients without LV dilatation because it predicts reduced cardiac function after aortic valve replacement. Exercise-induced PH is regarded as useful in the early diagnosis of pulmonary arterial hypertension due to a reduction of the pulmonary vascular bed at an early stage.