The purpose of this study was to investigate whether microvascular resistance index
(MVRI) immediately after primary percutaneous coronary intervention (PCI) can predict
the transmural extent of infarction (TEI) defined by contrast-enhanced cardiac magnetic
resonance (ce-CMR) in patients with anterior acute myocardial infarction (MI).
The degree of microvascular damage is an important determinant of myocardial viability
and clinical outcomes in acute MI. A novel dual-sensor (pressure and Doppler velocity)
guidewire has the ability to evaluate microvascular damage. ce-CMR can accurately
discriminate transmural from nontransmural MI, and the TEI by ce-CMR can predict future
improvement in contractile function.
In 27 patients immediately after primary PCI for a first anterior acute MI, MVRI,
coronary flow reserve (CFR), deceleration time of diastolic velocity (DDT), and zero
flow pressure (Pzf) were measured with a dual-sensor guidewire. TEI was graded from
1 to 4 based on the transmural extent of hyperenhanced tissue (1 = 0% to 25% of left
ventricular wall thickness, 2 = 26% to 50%, 3 = 51% to 75%, and 4 = 76% to 100%).
Infarct size by ce-CMR was also calculated.
Peak creatine kinase-myocardial band values were significantly correlated with MVRI
(r = 0.77, p < 0.0001), CFR (r = -0.69, p < 0.0001), DDT (r = -0.75, p = 0.0001),
and Pzf (r = 0.75, p < 0.0001). Also, infarct size by ce-CMR was significantly correlated
with MVRI (r = 0.78, p < 0.0001), CFR (r = -0.67, p < 0.0001), DDT (r = -0.70, p <
0.0001), and Pzf (r = 0.72, p = 0.0002). Receiver-operating characteristic curve analyses
of MVRI, CFR, DDT, and Pzf for predicting transmural MI (TEI-grade 4) demonstrated
that the area under the curve tended to be higher for MVRI (0.885) than those for
CFR (0.848), DDT (0.862), and Pzf (0.853). The best cut-off value for MVRI was 3.25
mm Hg x cm(-1) x s (sensitivity 75%, specificity 89%). Moreover, increased MVRI was
significantly related to increased TEI-grade (p < 0.0001).
MVRI measured immediately after primary PCI is a useful predictor for the TEI in patients
with anterior acute MI.