放射線照射による肺動脈漏斗部狭窄症の1例

Radiation-Associated Pulmonary Infundibular Stenosis:A case report

　68歳，女性．心雑音精査のために入院した．45歳時に左乳癌にて根治手術後，総量51Gyの放射線照射を縦隔の上部と下部にそれぞれ受けた．2カ月，後総量57Gyの放射線照射を上記部位にそれぞれ受けた．59歳時に心膜液貯留のため入院したが，この時には心雑音を聴取しなかった．今回入院後の心エコー図にて，肺動脈弁に異常はなく，肥厚した右室自由壁が収縮期に右室流出路を狭める所見を認めた．ドプラ心エコーでは右室流出路に12mmHgの圧較差を認め，カラードプラではその部に乱流をみた．右心カテーテル検査でも同様の圧較差を認め，本症例を縦隔への放射線照射による肺動脈漏斗部狭窄症と診断した．

A case of pulmonary infundibular stenosis due to radiation is presented. A 68-year-old female was ad-mitted to the hospital for evaluation of cardiac murmur. She had had a radical mastectomy for the left breast cancer at the age of 45 years and subsequently received mediastinal radiation with an electron beam. First total radiation doses to the upper and lower medias-tinum were 51 Gy, respectively ; second total radiation doses to the same portions were 57 Gy, respectively. At the age of 59 years, pericardial effusion due to radiation-associated pericarditis was noted but no cardiac mur-mur was heard. She had been free from symptoms during the long clinical course of her illness.

Physical examination on admission showed systolic ejection murmur of grade 3/6 at the Erb area, normal blood pressure of 134/82 mmHg and normal sinus rhyth-m of 74 beats/min. B-mode echocardiography showed pericardial effusion contiguous to the posterior wall of the left ventricle and no asynergy and no hypertrophy of the left ventricular wall. No valvular dysfunction was detected. The right ventricular (RV) outflow tract was strikingly narrowed at systole because of the hyper-contraction of the thickened RV free wall at the RV outflow tract. Doppler echocardiography revealed a turbulent flow with a pressure gradient of 12 mmHg at the RV outflow tract. A similar pressure gradient was noted by RV pressure study, which showed 32/0 mmHg (end-diastolic pressure 4 mmHg) at the RV, 17/4 mmHg at the RV outflow tract, and 20/6 mmHg (mean pressure 11 mmHg) at the pulmonary artery. Right ventriculography revealed a systolic narrowing of the RV outflow tract and coronary angiograms were nor-mal.

The cardiac murmur heard 21 years after the radia-tion therapy, the chronic pericardial effusion and the pressure gradient at the RV outflow tract, associated with thickened RV free wall at the RV infundibulum, suggest that the pulmonary infundibular stenosis was caused by mediastinal radiation. Radiation-associated pulmonary infundibular stenosis is a rare entity and is recognized as a late cardiac involvement after a large dose of chest radiation.