Pulsation-pressure relationship in experimental aneurysms: observation of aneurysmal hysteresis

In this study the pulsation-pressure relationship in an experimental model of aneurysms was analyzed. In addition, we have examined pulsatility of the aneurysmal wall reinforced by Guglielmi Detachable Coils (GDC). Bifurcation (BAn), aneurysms (LAn) and bilobar (BiA) aneurysms were produced in 15 mongrel dogs. The aneurysmal dome was constructed from a segment of the external jugular vein which was sutured to the window performed on the apex of bifurcation of the ECA and lingual artery (BAn) or on the ECA (LAn). One set of the GDC (diameter 5 mm, length 20 cm) were inserted into the aneurysm. Intra-aneurysmal pressure, aneurysmal pulsation, ECG and femoral artery pressure were recorded. Results showed that an experimental aneurysm pulsates in synchrony with the intra-aneurysmal pressure and aneurysmal pulsation is proportional to the aneurysmal size. Pulsation profile also depends on the aneurysmal type (BAn, LAn, BiA). The looped pressure-pulsation curve indicates that aneurysms exhibit property of hysteresis. For the same pressure the aneurysm is smaller during the ascending (systolic) portion of the blood pressure wave. Insertion of catheter into the aneurysm and subsequent release of the GDC did not elicit any measurable changes of the intra-aneurysmal pressure. Aneurysm reinforced by GDC showed smaller pulsation and the hysteresis was reduced as well. It was concluded that aneurysmal hysteresis could be an important factor resulting in degeneration of aneurysmal wall since it is known that hysteresis accelerates degeneration of all fibrous elements, predominantly of elastic fibers. GDC seems to buffer the intra-aneurysmal hemodynamic forces and hence they might have a stabilizing effect on the aneurysmal wall.