Online Version: including text, references, Figure I legend

Correlation between MR and PET data:

For healthy volunteers (pooled Norm 1 and Norm 2) mean slopeendo was 0.283±0.051 which was not significantly different from slopeendo of normal myocardium of patients (0.268±0.043). Slopeendo of pathological sectors (mean of MR thresholds: 0.166±0.022) was 0.123±0.023. Since MR slope data are considered relative measures of perfusion, slope data of each sector were divided by the corresponding threshold slope value that was determined by the ROC analysis (comparison with QCA): As a result a slope index value <1 would indicate reduced perfusion. Correlation of hyperemic MBF measured by PET with the slope indexes was performed with full wall thickness data. Within the supply territory of a stenosed coronary artery the sector with the most severe reduction in slope index and hyperemic MBF, respectively, was used exclusively for analysis. In patients with CAD, slopes of sectors supplied by non-stenosed coronary arteries were averaged, in healthy volunteers slope data of all sectors of the heart were averaged.

As shown in online Figure I the relationship between MBF measured by PET and SI upslope data measured by MR was non-linear indicating an underestimation of high flows by the SI upslope data. Hence, MR upslope data seem well suited for the detection of coronary stenoses, but may not be adequate to detect subtle changes in the high flow range. In patients with CAD hyperemic MBF of sectors subtended by non-stenosed coronary arteries was reduced compared with hyperemic MBF of normal hearts (1.7±1.5 vs 3.05±1.65 mL.min-1.g-1, P<0.0001, unpaired t test) which is in agreement with earlier studies [1, 2]. However, corresponding MR slope index data were not different (1.3±0.1 vs 1.2±0.2, not significant). A correlation between SI upslope and myocardial perfusion was repeatedly demonstrated in experimental [3, 4] and clinical studies [5, 6]. Although in a canine model of coronary stenosis [3] a linear fit of MR upslope data and microsphere data yielded a correlation coefficient of r=0.96, in these plots slope appeared to level off for flows ≥ 3 mL.min-1.g-1. In the present study, a similar finding was obtained in patients challenged by a pharmacologic vasodilator.

Reproducibility: The saturation recovery approach demonstrated arrythmia-insensitivity: with RR intervals varying between 480 and 1280ms (coefficient of variation: ±32%) changes in SI in phantoms ranged from ±0.4% to ±1.4% (at Gd-DTPA-BMA concentrations varying from 5.0 to 0.1 mmol/L, respectively).

For the intraobserver variability of slopeendo and slopetrans (evaluated in 320 sectors of 10 randomly chosen patients) the mean difference (with the 95% confidence interval in parentheses) was -0.3% (-18.3 to +17.7%) and -2.5% (-14.3 to +9.4%), respectively. For the interobserver variability the results were 5.6% (-15.3 to +26.5%) and 4.7% (-14.7 to +24.1%), respectively.

REFERENCES

1. Uren NG, Crake T, Lefroy DC, et al. Reduced coronary vasodilator function in infarcted and normal myocardium after myocardial infarction. N Engl J Med. 1994;331:222-7.

2. Sambuceti G, Parodi O, Marcassa C, et al. Alterations in regulation of myocardial blood flow in one-vessel coronary artery disease determined by positron emission tomography. Am J Cardiol. 1993;72:538-43.

3. Wilke N, Simm C, Zhang J, et al. Contrast-enhanced first pass myocardial perfusion imaging: correlation between myocardial blood flow in dogs at rest and during hyperemia. Magn Reson Med. 1993;29:485-97.

4. Wilke NM, Jerosch HM, Zenovich A, et al. Magnetic resonance first-pass myocardial perfusion imaging: clinical validation and future applications. J Magn Reson Imaging. 1999;10:676-85.

5. Matheijssen NA, Louwerenburg HW, van Rugge F, et al. Comparison of ultrafast dipyridamole magnetic resonance imaging with dipyridamole SestaMIBI SPECT for detection of perfusion abnormalities in patients with one-vessel coronary artery disease: assessment by quantitative model fitting. Magn Reson Med. 1996;35:221-8.

6. Al-Saadi N, Nagel E, Gross M, et al. Noninvasive detection of myocardial ischemia from perfusion reserve based on cardiovascular magnetic resonance. Circulation. 2000;101:1379-83.

ONLINE FIGURE LEGEND

Figure I

The correlation between myocardial blood flow (MBF) determined by PET and upslope data determined by MR is shown during hyperemic condition. A slope index value <1 indicates reduced hyperemic perfusion (for details see Results Section). The MR slope data are sensitive for changes of flow in the low normal range (steep portion of the curve). The volunteer population (crossed circle) is constructed from the Norm 2 subjects (n=10) studied with MR and 8 low-likelihood subjects (collected randomly from the PET normal data base). In vessels with multiple stenoses classification of stenosis severity was based on the most severe lesion.

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