Page 20 - Coronary hemodynamics in acute myocardial infarction - Matthijs Bax
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Chapter 1
With our studies, we wanted to assess the degree of deviation of microvascular dysfunction at the time of reperfusion of the acute myocardial infarction. Furthermore, we wanted to clarify the time course of recovery of microvascular dysfunction and the predictive value of acutely disturbed microvascular function in relation to left ventricular function recovery.
In conclusion, insufficient restoration of blood flow, both at the epicardial level and based on reperfusion injury and no-reflow in the microcirculation, leads to a larger myocardial infarction and poorer prognosis. Even after correction for the size of the myocardial infarction, no-reflow entails suboptimal recovery of the left ventricular function. For the risk stratification of patients with acute myocardial infarction, it is important to know the extent of microvasculature dysfunction at the time of reperfusion. This knowledge might help to identify high risk patients, to identify timing and effect of adjunctive interventions and gaining more insight into the process of reperfusion injury.
Doppler derived flow velocity signal information
When starting our studies described in this thesis, PPCI as mechanical reperfusion therapy had just become the treatment of choice in STEMI patients as it still is today. After complete restoration of the epicardial coronary blood flow, no- or slow reflow was recognized as a suboptimal treatment outcome in the acute phase of myocardial infarction resulting in poor long-term clinical outcomes. Restoration of blood flow was evaluated on the basis of the eyeballing technique determining TIMI angiographic flow grades (flow grades based on results of the Thrombolysis In Myocardial Infarction trial). Semi quantitative measurements as (corrected) TIMI-frame count using the film frame rate as measure of speed was used for the same purposes. Using Doppler tipped guide wires to determine flow velocity after reperfusion absolute blood flow velocity could directly be measured. Profound heterogeneity was observed between the TIMI techniques and the blood flow velocity in reperfused infarct arteries.64 Furthermore, TIMI flow assessment had a low sensitivity for detecting microvascular obstruction.65 It was unclear what the best parameters were at the time of acute myocardial infarction, to predict the recovery of left ventricular function. In the timeframe of our studies, it was possible to determine coronary flow reserve (CFR) as a measure of microvascular integrity and microvascular autoregulatory function by means of quantification of the coronary blood
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