Page 69 - Coronary hemodynamics in acute myocardial infarction - Matthijs Bax

The Doppler flow wire in acute myocardial infarction
analysis, CFVR as measured by the Doppler flow guidewire in comparison with
the aforementioned, commonly reported angiographic and clinical parameters,
was better in predicting recovery of left ventricular function. All patients with a
CFVR>2.0 directly after primary PCI showed improved left ventricular function (measured as echocardiographic 16-segment wall motion index) at 6 months’
follow-up. Doppler-derived CFVR was independently correlated with recovery
of global and regional left ventricular function. No independent relation
was found between angiographic parameters or ST-segment resolution and
recovery of left ventricular function. Recovery of left ventricular function after
acute MI can be accurately predicted by intracoronary Doppler flow velocity 4 measurement during primary PCI.
Comparison of Doppler flow velocity measurement and contrast-enhanced CMR
The assessment of microvascular injury by coronary Doppler flow velocity measurement has been found to correspond well to evaluation by contrast- enhanced CMR. A series of 27 consecutive patients with a first anterior MI underwent CMR and repeat catheterisation for intracoronary flow measurement within 1 week in a study by Hirsch et al.10 All patients had a postprocedural TIMI flow grade 3. However, CMR showed microvascular obstruction in 19 patients (70%). Based on the extent of microvascular obstruction detected by contrast- enhanced CMR, patients were subsequently stratified as having mild or severe microvascular obstruction. Systolic flow reversal was seen in none of eight patients without microvascular obstruction, in four of 10 (40%) patients with mild microvascular obstruction and in six of nine patients (67%) with severe microvascular obstruction. In accordance with previous studies, the diastolic deceleration time was reduced in patients with mild (mean 575 ms) and severe (mean 382 ms) microvascular obstruction in comparison with patients without microvascular obstruction (mean 708 ms). The extent of microvascular obstruction seen by CMR was independently correlated with systolic flow reversal, a short diastolic deceleration time, and low CFVR of the IRA.
Limitations of the Doppler flow wire and alternative invasive techniques to assess microvascular injury
A few limitations of the Doppler flow wire should be mentioned. Although there is fair reproducibility of CFVR, it is dependent upon a number of haemodynamic conditions such as arterial pressure and heart rate.23–25 The haemodynamic
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