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Correspondence of Invasive FFR vs. Perfusion MRI at 3Tesla in Patients with Recent NSTEMI
Jamie Layland 1,2, Sam Rauhalammi2, Matthew Lee1,2, Nadeem Ahmed1,2, Stuart Watkins1, Kenneth
Mangion1,2, John McClure2, David Carrick1,2, Anna O’Donnell1, Arvind Sood3, Keith Oldroyd1, Sasha
Radjenovic2, Colin Berry1,2
1West
of Scotland Heart and Lung Centre, Golden Jubilee National Hospital, 2 BHF Glasgow
Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of
Glasgow; 3Hairmyres Hospital, East Kilbride, UK
Background:
Coronary microcirculatory function may be disturbed in patients with a recent acute coronary
syndrome. Myocardial fractional flow reserve (FFR) is a guidewire-derived index of coronary stenosis
severity that was validated in patients with stable symptoms. We aimed to assess the diagnostic
accuracy of FFR in patients with a recent non-ST segment myocardial infarction (NSTEMI) when
compared with 3T stress perfusion MRI.
Methods:
106 patients with NSTEMI who had been referred for early invasive management guided by coronary
angiography were included. FFR was measured in all major patent epicardial coronary arteries with a
visual stenosis estimated at ≥30%. In addition, where clinically appropriate, an FFR assessment
following PCI was also performed. Myocardial perfusion was subsequently assessed non-invasively
with stress MRI at 3T (Siemens MAGNETOM Verio). MRI provided the reference dataset.
Hyperaemia for FFR and MRI was established with intravenous adenosine (140 µg/kg/min). In a small
number of patients MRI was performed prior to coronary angiography/PCI. Baseline stress and rest
perfusion MRI images were analysed side-by-side using dedicated software (Argus Dynamic Signal,
Siemens, Erlangen, Germany). The stress and rest perfusion scans were viewed simultaneously, and
areas of hypoperfusion were assigned to coronary territories using the American Heart Association
coronary arterial segment model. In each patient, the coronary artery territories with abnormal
perfusion were recorded. In cases of disagreement between observers, a third blinded observer
adjudicated. The MRI analyses were performed blind to the FFR results.
A perfusion defect was classified as significant according to the presence of ischaemia in 2 segments
of a 32 segment model i.e: > 60 degrees in either the basal or the mid-ventricular slices or > 90
degrees in the apical slice or any transmural defect or two adjacent slices.
Results:
Mean age was 56.7±9.8 years and 82.6% male. Mean time from FFR evaluation to MRI was 5.8 ± 3.1
days. The mean ± SD left ventricular ejection fraction was 58.2±9.1%. Mean infarct size was 5.4 ±
7.1% of left ventricular volume and mean troponin was 5.2±9.2g/L. A total of 1696 segments were
available for analysis. 34 segments were excluded from the analysis due to problematic image quality
so 1664 segments were finally included. Of these, 824 segments were available for comparison with
FFR. A total of 176 vessels were assessed – 104 in the infarct-related arteries and 72 in the noninfarct-related arteries. There were 49 fixed and 150 segmental perfusion defects. There was a
negative correlation between the number of segments and FFR (r = -0.79, 0<0.0001).
The sensitivity, specificity, PPV and NPV for FFR≤ 0.8 was 91.17%, 95.7%, 91.2% and 95.7%
respectively. The sensitivity, specificity, PPV and NPV for FFR≤ 0.75 was 82.35%, 98.5%. 96.5%, and
93.2% respectively.
ROC analysis demonstrated that the optimal cut off value of FFR for demonstrating reversible
perfusion abnormalities on MRI was ≤0.8 (AUC 0.93 (0.88-0.99), p<0.0001). This was associated
with a sensitivity of 91.2% and a specificity of 99.5%.
Conclusion:
FFR measured invasively in patients with recent NSTEMI corresponds well with stress perfusion MRI
at 3T. The results support the notion that the coronary microcirculation may be functionally intact in
NSTEMI patients, in whom the infarct burden is generally modest.