Abstract 2806: Percutaneous Intervention Leads to a Reduction in “Minimum” Microvascular Resistance
Background: Microvascular resistance has previously been believed to be constant and minimal with pharmacological induction of hyperaemia by IV adenosine infused at 140μg/kg/ min. Mathematical derivation of indices commonly used to evaluate coronary physiology is based on this assumption. The index of minimum microvascular resistance (IMR) has been shown to examine the microvasculature independently of epicardial stenosis severity using thermodilution.
Methods and Results: Comprehensive physiological assessment pre and post intervention using the pressure wire was made in 17 patients with single and multi-vessel disease undergoing elective revascularisation (hyperaemia induced with adenosine 140μg/kg/ min via femoral vein). Mean (SD) baseline FFR was 0.63 (0.14) and collateral flow index was 0.13 (0.08). Post intervention the IMR fell significantly (baseline 26.29 (13.36), post intervention 15.92 (8.66), p = 0.01). A rise in IMR above baseline was observed in only 1 patient following intervention. No correlation between FFR or CFI and change in resistance was found. In 3 patients minimum IMR was recorded following intervention to a second vessel, prior to treatment of the target artery.
Conclusions: Minimum microvascular resistance is not achieved pharmacologically and additional hyperaemia is seen following intervention. In part this is likely to be due to increased distal pressure following relief of the epicardial obstruction, however, the hyperaemic response following intervention to a non-target vessel suggests that additional global mechanisms are at play.