Page 182 - Coronary hemodynamics in acute myocardial infarction - Matthijs Bax

Chapter 11
after reperfusion. Microvascular status and function are important predictors of event-free survival but are not readily visible and available at the time of reperfusion.
A brief description is provided on coronary blood flow regulation and microvascular function and how these factors are influenced by local (patho) physiological conditions.
Since it was unclear at the end of the last century when and to what extent microvascular integrity would restore after reperfusion of the infarcted artery, we designed the study described in chapter 2. It was for the first time possible to measure the blood flow velocity in the coronary artery using a Doppler crystal mounted on a coronary guidewire. In Japan, the first studies had been performed that showed various abnormal Doppler flow velocity patterns in the setting of acute myocardial infarction (AMI) to describe microvascular dysfunction. Kern et al. demonstrated that using the Doppler technique, the coronary flow velocity reserve (CFVR or CFR) was a more relevant derivative measure of myocardial blood flow than the TIMI flow and TIMI frame-count, to determine the result of reperfusion.
The study in chapter 2 describes the prospective evaluation of 100 patients with an anterior myocardial infarction in single vessel disease, who were treated with primary PCI (PPCI). Immediately after reperfusion, Doppler flow parameters were assessed including baseline flow velocity, adenosine-stimulated maximum blood flow velocity, calculated CFR, microvascular resistance at rest and during hyperemia in both the infarct and non-infarct related artery (IRA and non-IRA). Doppler measurements were repeated, for the first time, at 1 week and 6 months after myocardial infarction. Echocardiograms were made before reperfusion, at 24 hours after the infarction as well as after 1 week and 6 months of follow-up to relate microvascular function to left ventricular recovery. In the 73 patients eligible for follow-up and without restenosis in the previously treated vessel, the Doppler flow determined CFR appeared to be the only independent 6-month predictor of global and regional restoration of LV function and thus a better prognostic marker than the usual measurements such as TIMI flow and TIMI frame count.
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