The delay of contrast arrival in magnetic resonance first-pass perfusion imaging: a novel non-invasive parameter detecting collateral-dependent myocardium.

AIM: To establish the regional delay of contrast arrival in magnetic resonance perfusion imaging (MRPI) for the detection of collateral-dependent myocardium in patients with coronary artery disease. DESIGN AND SETTING: Observational study, case series; single centre, university hospital. PATIENTS: 30 patients with coronary artery disease and collateral-dependent myocardium and 17 healthy volunteers. METHODS: Resting and hyperaemic (adenosine) MRPI was used to determine the delay time (Deltat(d)) of contrast arrival between the left ventricle and collateral-dependent or antegradely perfused myocardium, and myocardial perfusion (MP, ml/min/g). RESULTS: In healthy volunteers, mean (SD) Deltat(d) at rest and during hyperaemia were 0.8 (0.4) and 0.3 (0.3) s, and MP was 1.14 (0.21) and 4.23 (1.12) ml/min/g. In patients Deltat(d) in antegradely perfused vs collateral-dependent myocardium was 0.9 (0.7) vs 1.7 (1.0) s at rest (p<0.001), and 0.4 (0.3) vs 1.1 (0.6) s (p<0.001) during hyperaemia. MP was 1.12 (0.11) and 0.98 (0.28) ml/min/g (p = NS) at rest and 2.46 (0.85) vs 1.86 (0.91) ml/min/g (p<0.01) during hyperaemia. Receiver operating characteristics analysis showed the best sensitivity and specificity of 90% and 83% for hyperaemic Deltat(d) of >0.6 s (area under the curve (AUC) = 0.89) to detect collateral-dependent myocardium, while resting Deltat(d) (AUC = 0.77) and perfusion (AUC = 0.69 at rest or 0.70 during hyperaemia) were less accurate. CONCLUSIONS: MRPI-derived hyperaemic delay of contrast arrival detects collateral-dependent myocardium with high sensitivity and specificity. Perfusion was less sensitive, emphasising the clinical role of Deltat(d) in non-invasive detection of collateral-dependent myocardium.

Magnetic resonance first-pass perfusion imaging: overview and perspectives.

The data from clinical studies with quantitative MR first-pass perfusion imaging suggests that this technique outperforms SPECT--widely available clinical imaging tool--in sensitivity and specificity. Moreover, MRFP imaging may be combined with the assessment of global and segmental function of the heart and regional wall thickening, and in addition, performed with pharmacological stress agents. The inter- and intra-observer reproducibility of quantitative MRFP is comparable with clinically used nuclear medicine techniques. MRFP measurements can discern collateral myocardium and are able to identify small changes in myocardial blood flow and myocardial perfusion reserve (the ratio of stress blood flow over resting). MRFP imaging has been mainly used in context of coronary artery disease but many other exciting areas in clinical cardiology are awaiting of new insights that can be accomplished with this technique. Trials are needed to obtain the approval of the contrast agent (Gd-DTPA) and perfusion sequences by the Food and Drug Administration and to establish reimbursement procedures with the third-party insurance companies and health maintenance organizations.