Page 68 - Coronary hemodynamics in acute myocardial infarction - Matthijs Bax

Chapter 4
pressure.20 However, owing to capillary obstruction the capacitance of the myocardial microvasculature decreases. This has an impeding effect on diastolic flow, resulting in a rapid decrease in coronary flow velocity. Rapid deceleration of diastolic flow is associated with poorer tissue perfusion, worse functional outcome, left ventricular remodelling and an increased rate of adverse cardiac events.21
However, rapid deceleration of diastolic flow also occurs in patients without signs of microvascular obstruction measured by MCE or CMR. Therefore, rapid deceleration of diastolic flow alone has a high sensitivity, but a relatively low specificity for detecting microvascular obstruction.
Systolic flow reversal is another accurate marker of microvascular obstruction. The increased microvascular impedance resulting from microvascular injury hampers the heart’s ability to squeeze blood forward into the venous system during systole, and consequently, blood will be squeezed back into the arterial system, resulting in systolic flow reversal. In the most severe case of microvascular obstruction, a high back pressure persists throughout systole, resulting in total disappearance of systolic antegrade flow.
Doppler flow wire as a tool to predict recovery of left ventricular recovery after acute MI
Kawamoto et al investigated the clinical value of the Doppler flow guidewire- derived coronary flow pattern in predicting left ventricular function in 23 patients with a first anterior acute MI.21 The coronary flow pattern was recorded immediately after the primary angioplasty and left ventricular function was assessed before recanalisation and at 1-month follow-up by echocardiographic anterior wall motion score index. In this study, a short diastolic deceleration time (<600 ms) and low average systolic peak velocity (<6.5 cm/s) were associated with a lack of recovery of regional left ventricular function.
Bax et al compared the predictive value of CFVR with TIMI flow grade, corrected TIMI frame count, myocardial blush grade and resolution of ST-segment elevation for recovery of left ventricular function in the aforementioned series of 73 patients with a first anterior MI treated with primary PCI.22 Two-dimensional echocardiography was performed immediately before the primary PCI and repeated after 1 day, 1 week and 6 months. After multivariate linear regression
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