ファロー四徴症根治手術時の右室流出路パッチ形成術の流体力学的検討

Effect of pericardial patch on the outflow tract on hemodynamical and fluid dynamical parameters in the corrective surgery of tetralogy of Fallot

　ファロー四徴症根治術時における右室流出路狭窄解除の重要性についての検討はすでに数多くなされている。しかしどの程度に狭窄が解除されたかという的確な評価法についての検討はなお不十分であろうと思われる。すなわち従来より狭窄部前後の圧差や右室左室圧比^1）が本症根治術における右室流出路狭窄の評価法として用いられているが，それらが狭窄部の血流速度や体血管抵抗に左右されやすいことはすでに著者ら^2,3）が報告した。そこで著者ら^4）は流出路狭窄の流体力学的評価法として臨床的な指標，すなわち抵抗係数（λ'）を考案し検討してきた。最近，右室流出路狭窄の解除にパッチの使用がすすめられている^5）。今回，著者らは右室流出路狭窄解除に用いられる心膜パッチの影響を流体力学的手法を用いて解析し検討した。すなわち，右室流出路の抵抗係数（λ'），断面積比狭窄度，機能的弁口面積および血行動態の各指標を症例ごとに算出し，心膜パッチ縫着群と非縫着群間でそれらを比較検討した。

The outflow patch placed on the stenosed tract of right ventricle for relieving the stenosis might contribute much to the results of radical correc-tion of tetralogy of Fallot. The effect of peri-cardial patch on hemodynamic and fluid dynamical parameters after the intracardiac repair were studied by use of an electromagnetic flowmeter and pressure transducers. The shape of outflow tract stenosis of right ventricle was assumed to be orifice-like. The cross-sectional area of func-tional pulmonary valve was derived from head loss coefficient calculated by the pressure gradient and the peak flow through the stenosis. Radical correction for tetralogy of Fallot was undertaken on 28 patients. 19 patients were operated upon with pericardial patch (group A) and 9 patients without it (group B).

Cross-sectional areas of pulmonary valve (cm²/ m²) were not significantly different between the group A (0.82±0.26) and the group B (0.72±0.12). The systolic pressure (mmHg) of radial artery (96±17,100±20) and right ventricle (57±20, 55 ±12), systolic pressure gradient (mmHg) across the stenosis (24±19, 25±13), cardiac index (l/min ･m²) (2.5±0.7, 2.4±0.6), aortic peak flow index (l/min･m²) (8.7±2.2, 8.3±1.6), peak velocity (cm/sec) in the aortic root (58±17, 61±16), peak Reynolds number (3300±1200, 3400±1100) and heart rate (beats/min) (145±15, 134±13) were not significantly different between these groups.