軽症高血圧症の拡張期障害とその機序—運動負荷心エコー法およびカルシウム拮抗薬投与による検討

Impaired diastolic function and its mechanism in mild hypertension:Assessment by exercise echocardiography and calcium antagonist

　軽症本態性高血圧症の心循環動態については，左室収縮能は正常であるが左室拡張能について等容性拡張期（IRP）延長などの拡張能障害が認められている^1〜3）。その原因には，血圧上昇による後負荷上昇^3）や心肥大^1）が考えられている。

　本研究は運動負荷心エコー法を用いて，軽症高血圧症の安静時および運動時心血行動態を検討し，さらに同症にカルシウム拮抗薬である塩酸ニカルジピンを投与し後負荷を低下させ健常者のそれと同等にした時点での変化を観察した。この結果本症の心血行動態並びに拡張能障害のメカニズムに関し，2,3の興味深い知見が得られたので，若干の文献的考察を加えて報告する。

For clarifying the hemodynamics, the mechanism of the impaired diastolic function in mild hypertension, eighteen mildly hypertensive men, mean age of 38.0± 10.5 (mean±SD), were compared with sixteen healthy men, mean age of 35.9±8.9, by means of exercise echo-cardiography. The hemodynamic change after reduction of afterload by administration of nicardipine hydrochlo-ride, which was administered 60mg/day orally to eight subjects in mildly hypertensive group for seven days, was also studied. At rest, left ventricular hypertrophy, increased total peripheral vascular resistance and pro-longed isovolumic relaxation period (S₂-mitral valve opening) were observed in mildly hypertensive group. No significant differences were present in cardiac per-formance at rest. During exercise, cardiac index and velocity of circumferential fiber shortening of mildly hypertensive group were as the same as those of healthy group. However, during exercise, healthy group showed significant increase of left ventricular enddiastolic dimension, while no significant change was seen in mildly hypertensive group, so that stroke volume during exercise in mildly hypertensive group was smaller than that in healthy group. These results were responsible for diminished Frank-Starling effect during exercise in mildly hypertensive group. In diastolic function, pro-longed isovolumic relaxation period and decreasing aortic closing pressureiisovolumic relaxation period were revealed during exercise in mildly hypertensive group. Nicardipine hydrochloride had no effect on cardiac function without significant fall of systolic and diastolic blood pressures and total peripheral vascular resistance. Impaired diastolic function in mildly hypertensive group still existed even after afterload normalization by admi-nistration of nicardipine hydrochloride.

We concluded that decreased Frank-Starling effect during exercise and impaired early diastolic function were existent in mild hypertension, which were probably due to not increased afterload, but cardiac muscular hypertrophy.