Restoration of myocardial blood flow following percutaneous coronary balloon dilatation and stent implantation: assessment with qualitative and quantitative contrast-enhanced magnetic resonance imaging

Inter-observer variability of visual analysis of "stress"-only adenosine first-pass myocardial perfusion imaging in relation to clinical experience and reading criteria

To assess the inter-observer agreement of adenosine “stress”-only visual analysis of perfusion MR images in relation to experience and reading criteria. 106 adenosine perfusion MR examinations out of 350, 46 consecutive positive examinations and 60 randomly selected negative examinations were visually analysed by three individual readers (two residents and a technician) with different levels of experience. Readings (blinded for any information) were compared with the reading of an expert radiologist. After a month the examinations were presented again (randomly) without knowledge regarding the first readings. This time readings were performed with the systematical use of reading criteria. Agreement with the expert reading was good for the most experienced resident (k = 0.88). Kappa was 0.48 for the least experienced, and 0.57 for the technician. After the second systematical reading inter-observer agreement increased to 0.9, 0.68 and 0.77 respectively. Overall kappa increased from 0.59 to 0.71. The use of reading criteria significantly improved the performance of the least experienced reader (P = 0.01). Visual analysis of adenosine “stress”-only first-pass perfusion MR images has moderate to very good agreement. Performance is experience related, but the systematic use of reading criteria significantly increased performance for the least experienced observer.

Stress perfusion magnetic resonance imaging of the heart

Extensive research has documented that rapid imaging during the first pass of a magnetic resonance imaging (MRI) contrast agent provides good sensitivity to detect myocardial blood flow deficits caused by coronary disease, cardiomyopathies, or microvascular dysfunction in patients without obstructive lesions in the coronary arteries. The autoregulatory mechanisms of the coronary circulation serve the purpose of maintaining sufficient blood flow at baseline in the presence of flow-obstructing coronary lesions. Stress testing is most commonly used in this setting to determine the hemodynamic effect of coronary lesions in the epicardial arteries when the small-vessel resistance has been minimized by vasodilation. The protocols for perfusion MRI combined with vasodilation have been successfully tested in large patient studies. Besides the absence of any ionizing radiation, MRI offers the advantages of relatively high spatial resolution to detect perfusion defects limited to the inner layer of the heart muscle. Furthermore, MRI can be used for noninvasive quantitative measurements of myocardial blood flow that compare well with invasive measurements with labeled microspheres. Additional useful markers, such as the dynamic distribution volume, the delay in the arrival of the contrast agent in a myocardial region relative to the enhancement in the arterial input, and the capillary permeability-surface area product, may, in the future, further enhance the capabilities to characterize with MRI coronary atherosclerosis, coronary vascular dysfunction, and adaptive mechanisms in the coronary circulation, such as arteriogenesis, that reduce ischemia.

MR perfusion and delayed enhancement imaging in the heart

Cardiac magnetic resonance imaging is rapidly emerging as an exciting and important technique for the investigation of congenital and acquired heart disease. This article focuses in particular on recent developments in the field of adenosine stress myocardial perfusion as well as addressing the many applications of 'delayed enhancement' imaging.

Myocardial perfusion after angioplasty in patients suspected of having single-vessel coronary artery disease: improvement detected at rest-stress first-pass perfusion MR imaging--initial experience

PURPOSE

To prospectively assess myocardial perfusion before and after successful intervention in patients suspected of having single-vessel coronary artery disease by using a steady-state free precession (SSFP) perfusion magnetic resonance (MR) imaging sequence.

MATERIALS AND METHODS

Local ethics committee approval and informed consent were obtained. Rest-stress perfusion MR imaging studies were performed in 18 patients with coronary artery disease (12 men, six women; mean age, 58.6 years +/- 13.6 [standard deviation]; range, 30-79 years) at 1.5 T with a multisection saturation-recovery SSFP sequence and 0.025 mmol gadopentetate dimeglumine per kilogram of body weight. MR studies were performed before (n = 18), several days after (n = 18), and 8 months after (n = 10) coronary intervention. Nine patients underwent percutaneous transluminal coronary angioplasty (PTCA) alone, and nine patients underwent PTCA with stent placement. Myocardial perfusion reserve index (MPRI) was calculated by dividing results of myocardial perfusion at maximal vasodilation by results at rest. The standard for myocardial perfusion was technetium 99m tetrofosmin single photon emission computed tomography. Statistical significance was tested with univariate variance analysis and Student t tests.

RESULTS

In the area of the stenosed vessel, MPRI was 1.04 +/- 0.24 before treatment and 2.18 +/- 0.57 several days afterward (P < .001). In remote areas, MPRI was 2.42 +/- 0.44. In the stent group, MPRI increased by 156%, from 0.99 +/- 0.20 before stent placement to 2.53 +/- 0.53 after (P < .001). Similarly, in the PTCA only group, MPRI increased by 72%, from 1.08 +/- 0.27 before PTCA to 1.87 +/- 0.39 after (P < .001). At follow-up in patients without recurring chest pain, MPRI was 2.14 +/- 0.37 in the area of the treated artery and 2.29 +/- 0.47 in remote areas (P = .06).

CONCLUSION

The MPRI, derived from rest-stress examinations, can provide information on success of interventional procedures in stenosed coronary arteries.

Efficacy of transmyocardial laser revascularization and thoracic sympathectomy for the treatment of refractory angina

BACKGROUND

Transmyocardial laser revascularization (TMR) is an effective treatment for relief of refractory angina. This benefit may be mediated by increase in myocardial perfusion or by cardiac denervation. We investigate the efficacy of TMR and thoracic sympathectomy (TS) for relief of angina and whether any clinical benefit is associated with enhanced myocardial perfusion.

METHODS

Twenty consecutive patients with nonrevascularizable coronary arteries and intractable angina were prospectively randomized to have TMR by holmium: yttrium aluminum garnet laser or TS. Subjects were clinically evaluated before, and for 42 months after, surgery. They underwent exercise tolerance testing and rest and stress quantitative perfusion magnetic resonance imaging (MRI) before, and 6 months after surgery.

RESULTS

The demographics of the two groups were similar. There was no perioperative mortality; however, two patients died in the TS group during follow-up. The Canadian Cardiovascular Society angina score improved from 3.4 +/- 0.5 to 2.6 +/- 1.1 (p = 0.06) in the TS group at 6 months but returned to 3.2 +/- 0.7 at 42 months, while in the TMR group it improved from 3.6 +/- 0.5 to 1.9 +/- 0.7 (p = 0.008) at 6 months and deteriorated to 2.5 +/- 0.9 (p = 0.01) after 42 months of surgery. The TMR-treated patients showed significant improvements in the SF-36 scores and Seattle Angina Questionnaire only at 6 months, whereas TS-treated patients did not show amelioration at any time during follow-up. The MRI protocol was completed in 15 of 20 (TMR = 8; TS = 7) patients and no significant differences in qualitative or quantitative perfusion variables were demonstrated in either group.

CONCLUSIONS

A greater clinical benefit was obtained with TMR than with TS early after surgery but this clinical effect did not seem to be associated with improvement in myocardial perfusion as assessed by MRI and part of the beneficial effect was lost by 42 months after surgery.