Magnetic resonance coronary artery imaging for redo coronary operations

Coronary MRA--a clinical experience in Europe

This review concentrates on contributions from European centers to magnetic resonance (MR) imaging of the coronary arteries. Coronary MR angiography has developed rapidly over the last 10 years, and there has been considerable interaction between Europe and the United States in the technical and clinical developments during this time. The major problems of coronary imaging have been gradually overcome with the combined use of respiratory and cardiac gating, as well as three-dimensional imaging. The ultrafast techniques such as spiral and echoplanar methods are likely to play a larger role in the future, and flow measurements are becoming possible. The next millennium should see the adoption of these techniques into routine clinical practice to allow the safe non-invasive diagnosis of coronary artery disease.J. Magn. Reson. Imaging 1999;10:721-727.

Coronary MR angiography

MR angiography of the coronary arteries became possible in 1991 with the development of a new group of fast MR imaging sequences. Although the role of coronary MR angiography in screening for coronary artery lesions has not yet been established, coronary MR angiography already has been very successful in the detection of coronary artery variants and the imaging of coronary stents and bypass grafts. Variants of these new MR imaging techniques also can quantitate velocity in native coronary arteries. Several generations of coronary MR angiographic techniques exist; all techniques use EKG-triggering. The use of MR contrast agents appears to further improve all techniques. Technical progress and changes in this subfield of cardiac MR imaging have been so fast that large-scale preclinical trials have not been conducted with the majority of the first and second generation coronary MR angiographic pulse sequences as known today. This article reviews the development of these new cardiac MR imaging techniques and the initial successes with clinical application using commercial MR scanners.

[Current state of non-invasive methods in the study of coronary arteries and surgical bypass grafts]

The advantages of visualizing the coronary arteries by means of a non-invasive technique as an alternative to conventional angiography are obvious. Echocardiography and computed tomography have not proved to be useful in this application. Magnetic resonance imaging, however, has recently been reported as a method able to depict reliable images of the coronary vessels, including the visualization of stenotic lesions. Unfortunately, these preliminary data have not yet been followed by studies confirming the usefulness of the technique in practice, probably because of the complexity of the current magnetic resonance imaging methods and, also, to the difficulties that the intricate coronary arterial tree poses to a tomographic imaging method such as magnetic resonance imaging. On the other hand, in particular aspects of the spectrum of coronary diseases, as anomalous congenital origin of the vessels or assessment of patency of venous bypass grafts, magnetic resonance imaging has proved to be of value and may be considered a useful diagnostic tool in clinical practice.

Coronary MR angiography

Coronary MR angiography is a new noninvasive diagnostic method in rapid evolution. It has the potential to combine structural information with functional assessment of coronary blood flow. Advances in technology will undoubtedly lead to enhanced resolution, improved accuracy, and shorter scan times. It is certain that coronary MR angiography will be a prominent diagnostic clinical tool in the years to come.

Assessment of human long saphenous vein function with minimally invasive harvesting with the Mayo stripper

BACKGROUND

The use of the Mayo Stripper to harvest the long saphenous vein has been shown to improve morbidity from leg wound incisions. It has not been universally accepted because of a perceived increase in injury to the venous conduit.

OBJECTIVE

To compare the function of undistended autologous long saphenous vein harvested by a Mayo stripper with the traditional 'open' technique in the same patient (n = 12) appearance.

METHODS

Vascular reactivity was assessed in isolated organ baths. Contractile function was measured in response to increasing concentrations (10(-9)-10(-5) mol) of 5-hydroxytryptamine and noradrenaline. This was calculated as a percentage of the maximum contractile response to 90 mM KCl measured in millinewtons (mN) (control 41.4 +/- 12.1, (n = 11), open technique 35.8 +/- 11.1, (n = 11), Mayo stripper 33.7 +/- 15.9, (n = 11)). The endothelial dependent and independent function was assessed with acetylcholine and sodium nitroprusside, respectively.

RESULTS

There was no significant difference in response to both constrictors and dilators between vein taken with the Mayo stripper compared with the traditional open technique (n = 6 for each observation; P > 0.05 by ANOVA). Histological examination by light microscopy of the vessel segments removed with the Mayo stripper was unable to show any significant damage to the vessel wall. Both functional and morphological studies were conducted by 'blinded' observers. One-year follow-up with magnetic resonance angiography (MRA) and stress thallium tomography demonstrated a patency rate with lower and upper estimates of 80 and 94%.

CONCLUSIONS

We have shown that harvesting the long saphenous vein with a Mayo stripper does not compromise vascular reactivity of the long saphenous vein or long-term patency.