Pressure-wire based assessment of microvascular resistance using calibrated upstream balloon obstruction: a predictor of myocardial viability.

OBJECTIVES: We assess microvascular integrity as a marker of myocardial viability after coronary stenting, using only a pressure guidewire.
BACKGROUND: Microvascular integrity generally is not assessed using pressure-only guidewires because the transducer lies upstream of microvasculature. We partially inflate a balloon inside a coronary stent to achieve a specific normalized pressure drop at rest (distal coronary/aortic pressure = 0.8) and then infuse a vasodilator, to render the wire sensitive to microvascular function. We hypothesize that the further decline in pressure (ΔFFR(0.8) ) predicts MRI myocardial viability.
METHODS: We studied 29 subjects with acute coronary syndrome including myocardial infarction. After successful culprit stenting, the resting coronary/aortic pressure was set to 0.8 using temporary balloon obstruction. ΔFFR(0.8) was defined as 0.8-(distal coronary/aortic pressures) during adenosine-induced hyperemia. The average transmural extent of infarction was defined as the average area of MRI late gadolinium enhancement (after 2.8 ± 1.5 days) divided by the corresponding full thickness of the gadolinium enhanced sector in short axis slices, and was compared with ΔFFR(0.8) .
RESULTS: ΔFFR(0.8) corresponded inversely and linearly with the average transmural extent of infarction (r(2) = 0.65, P < 0.001). We found that a transmural extent of infarction of 0.50 corresponded to a ΔFFR(0.8) threshold of 0.1, and had high sensitivity and specificity (100% and 94.4%, respectively).
CONCLUSIONS: Using only an upstream pressure-sensitive guidewire and a partially obstructing balloon during pharmacologic hyperemia, we were able to predict MRI myocardial viability with high accuracy after relief of epicardial stenosis. With further validation, this may prove a useful clinical prognostic tool after percutaneous intervention.