Imaging Strategies for Coronary Sinus Annuloplasty
resonance imaging may be of potential interest, but currently only computed tomography provides enough resolution to evaluate the relationship between the coronary sinus, the coronary arteries and the mitral annulus.
Coronary Sinus Anatomy
The feasibility of assessing the coronary venous anatomy is excellent, reaching almost 100% for the coronary sinus and the great cardiac vein.14,16
Figure 8: Relationship Between the Coronary Sinus and the Circumflex Artery
Measurement of coronary sinus and great cardiac vein diameters can be performed in the majority of patients with low intra- and inter-observer variability. Using multiplanar reconstruction, the coronary veins are manually selected and elongated, and the diameters are automatically measured all along the veins (see Figure 6). It has been shown that the diameter of the coronary sinus is larger in the supero-inferior direction than in the antero-posterior direction, indicating an oval shape. Lengths are also measured using this method. The tortuosity and curvature of the venous system can also be assessed using computed tomography, which helps to anticipate potential technical difficulties for implantation. Figure 7 presents an example of a patient with an abrupt curvature of the distal part of the great cardiac vein who could not be implanted using one of the devices discussed above.
Relationship with the Coronary Arteries
The circumflex artery crosses the venous system at a variable distance and in a variable path. It can run deeply between the mitral annulus and the coronary sinus or more superficially above the coronary sinus. Anatomical studies have shown that the former feature is common. In 61 explanted hearts, a course of the circumflex artery between the coronary sinus and the mitral annulus was noted in 64% of cases by Maselli and colleagues.18
In another anatomical
study from our group, the circumflex artery ran between the coronary sinus and the mitral annulus in 45% of patients.19
An appreciation of
the relationship between the venous system and the circumflex artery has been defined as a critical factor for the safety of mitral annuloplasty devices. The implantation of devices in patients with a circumflex running between the coronary sinus and the mitral annulus may expose the patient to coronary artery impingement; therefore, the procedure is usually not recommended in such patients. Furthermore, a correlation between the depth of the circumflex artery and its distribution has been reported.18
When
the circumflex is deeper than the coronary sinus, the number of marginal branches is higher and their diameter larger, increasing the potentially deleterious effect of circumflex compression.
Unlike venography, computed tomography allows for simultaneous imaging of veins and coronary arteries, and can help identify patients in whom the circumflex artery will or will not be a problem if a coronary sinus annuloplasty is attempted. Several studies have shown that the relationship between the coronary sinus and the circumflex artery can be assessed in a high number of patients using computed tomography.13,16
As in autopsy studies, a crossing between
the circumflex artery and the coronary sinus was observed in 60–80% of cases (see Figure 8). It is worth noting that there is significant variability in the distance to the point at which the coronary sinus intersects with the circumflex artery (from 37 to 116mm).
Relationship with the Mitral Annulus
The coronary sinus and the great cardiac vein run around the mitral annulus. However, in a significant number of patients the venous
EUROPEAN CARDIOLOGY
3D volume-rendering reconstruction (top) and projection (bottom) using computed tomography showing the relationship between the coronary sinus and the circumflex artery. In this example, the circumflex artery runs between the coronary sinus and the mitral annulus (crossing marked with a red arrow).
Figure 9: Relationship Between the Coronary Sinus and the Mitral Annulus
54%
Proximal A
14%
Distal B
Superior Same level Inferior
3D volume-rendering reconstruction illustrating the relationship (superior/same level/ inferior) between the coronary sinus and the mitral annulus at the proximal and distal coronary sinus. Source: Tops et al., 2007.16
Superior 56% Same level 30% Inferior 39% 7%
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