The effect of sequential arterial stenoses on flow and pressure.

The additive effect of two sequential stenoses on arterial flow and pressure was studied in five dogs, using an extracorporeal aorto-femoral shunt. It was determined that the concept of flow being governed by the more severe stenosis is imprecise. This is true only of one critical and one subcritical lesion: two critical stenoses have an additive effect. Otherwise subcritical stenoses can become critical in the presence of hyperemia. When evaluating patients with vascular insufficiency due to arterial narrowing, all stenoses should be carefully assessed and attention directed to their cumulative effect.