Authors:
T. Bartel¹, D. Hoefer¹, M. Frick¹, G. Poelzl¹, S. Mueller¹, H. Antretter¹, O. Pachinger¹, G. Laufer¹, ¹Medical University Innsbruck - Innsbruck - Austria,

Background: In heart transplant recipients, prognosis may be altered due to increased microcirculatory resistance. This investigation sought to evaluate course of microcirculatory alterations and its haemodynamic consequences.

Methods: In 89 orthotopic cardiac transplant recipients (mean age 58±10 years) without significant coronary artery stenoses, distal pressures were measured in the left and the right coronary artery using a pressure wire. Microvascular resistance was calculated (pressure divided by flow) during peak hyperaemia and the index of microcirculatory resistance (IMR) was derived. Flows were determined by thermodilution and coronary flow reserve (CFR) measured by the same technique. Standard haemodynamic parameters, including systolic left ventricular pressure (LVP), cardiac index (CI), and pulmonary capillary wedge pressure (PCWP) were recorded. In 16 patients, an initial examination was performed 1 month and a follow-up measurement 1 year after heart transplantation (HTX).

Results: Simple regression analysis revealed IMR to directly correlate with PCWP (r=0.34; p<0.001) and inversely with CFR (r=0.39; p<0.001), but not with systolic LVP and CI. IMR was also found to be particularly increased 1 month after HTX and to decline after 1 year (0.29±0.13 vs. 0.17±0.07; see graph). Follow-up of IMR after 1 year was demonstrated to depend on ischaemic time (r=0.50; p<0.05).

Conclusions: After HTX, microcirculation may be damaged due to ischaemia and posttransplant reperfusion but recovers in the big majority of cases. Moreover, it contributes to an increase in preload and that way, may lead to left ventricular backward failure. In contrast, systolic left ventricular performance is obviously not related to microvascular function.