Coronary MR imaging: lumen and wall

Delayed contrast-enhanced MRI of the coronary artery wall in takayasu arteritis

BACKGROUND

Takayasu arteritis (TA) is a rare form of chronic inflammatory granulomatous arteritis of the aorta and its major branches. Late gadolinium enhancement (LGE) with magnetic resonance imaging (MRI) has demonstrated its value for the detection of vessel wall alterations in TA. The aim of this study was to assess LGE of the coronary artery wall in patients with TA compared to patients with stable CAD.

METHODS

We enrolled 9 patients (8 female, average age 46±13 years) with proven TA. In the CAD group 9 patients participated (8 male, average age 65±10 years). Studies were performed on a commercial 3T whole-body MR imaging system (Achieva; Philips, Best, The Netherlands) using a 3D inversion prepared navigator gated spoiled gradient-echo sequence, which was repeated 34-45 minutes after low-dose gadolinium administration.

RESULTS

No coronary vessel wall enhancement was observed prior to contrast in either group. Post contrast, coronary LGE on IR scans was detected in 28 of 50 segments (56%) seen on T2-Prep scans in TA and in 25 of 57 segments (44%) in CAD patients. LGE quantitative assessment of coronary artery vessel wall CNR post contrast revealed no significant differences between the two groups (CNR in TA: 6.0±2.4 and 7.3±2.5 in CAD; p = 0.474).

CONCLUSION

Our findings suggest that LGE of the coronary artery wall seems to be common in patients with TA and similarly pronounced as in CAD patients. The observed coronary LGE seems to be rather unspecific, and differentiation between coronary vessel wall fibrosis and inflammation still remains unclear.

MRI discriminates thrombus composition and ST resolution after percutaneous coronary intervention in patients with ST-elevation myocardial infarction

Histological composition of material obtained by thrombus aspiration during percutaneous coronary intervention (PCI) in patients with ST-segment elevation acute myocardial infarction (STEMI) is highly variable. We aimed to characterize this material using magnetic resonance imaging (MRI) and to correlate MRI findings with the success of PCI in terms of ST-segment resolution. Thrombus aspiration during primary or rescue PCI was attempted in 100 consecutive STEMI patients, of whom enough material for MRI was obtained in 59. MR images were obtained at 9.4T and T1 and T2 values were measured. Patients with (n = 31) and without (n = 28) adequate ST resolution 120 min after PCI (≥70% of pre-PCI value) had similar baseline characteristics except for a higher prevalence of diabetes mellitus in the latter (10 vs. 43%, p = 0.003). T1 values were similar in both groups (1248±112 vs. 1307±85 ms, respectively, p = 0.7). T2 values averaged 31.2±10.3 and 36.6±12.2 ms; in thrombus from patients with and without adequate ST resolution (p = 0.09). After adjusting for diabetes and other baseline characteristics, lower T2 values were significantly associated with inadequate ST resolution (odds ratio for 1 ms increase 1.08, CI 95% 1.01-1.16, p = 0.027). Histology classified thrombus in 3 groups: coagulated blood (n = 38), fibrin rich (n = 9) and lipid-rich (n = 3). Thrombi composed mostly of coagulated blood were characterized as being of short (n = 10), intermediate (n = 15) or long evolution (n = 13), T2 values being 34.0±13.2, 31.9±8.3 and 31.5±7.9 ms respectively (p = NS). In this subgroup, T2 was significantly higher in specimens from patients with inadequate perfusion (35.9±10.3 versus 28.6±6.7 ms, p = 0.02). This can be of clinical interest as it provides information on the probability of adequate ST resolution, a surrogate for effective myocardial reperfusion.