(Circulation. 1995;92:436-441.)
© 1995 American Heart Association, Inc.
Articles |
From the Division of Cardiology, Department of Medicine, The Toronto Hospital (General Division) and University of Toronto, Ontario, Canada.
Correspondence to J. Colin Doig, University Department of Cardiology, Freeman Hospital, Freeman Rd, Newcastle upon Tyne, NE7 7DN, UK.
| Abstract |
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Methods and Results The size and shape of the proximal coronary sinus were measured in 15 patients with AVJRT and 14 control subjects after angiographic visualization. Coronary sinus dimensions, morphology, and angle of origin from the right atrium were measured. The proximal coronary sinus in patients with AVJRT was larger than in the control population. The mean ostium diameter was 12.2±2 mm compared with control dimensions of 8.5±1.5 mm, P=.00001. At a distance of 5 mm from the ostium, the coronary sinus measured 10.2±1.8 mm compared with 8.1±1.9 mm, P=.007. The dilatation persisted 10 mm into the coronary sinus, with a measurement of 9±1.4 mm compared with 7.6±2 mm, P=.04. In 73% of AVJRT patients, the proximal coronary sinus had the appearance of a wind sock. This morphology was seen only in 7% of control patients, in whom the coronary sinus was tubular (in 93%). There was considerable interindividual variability in the angle of origin.
Conclusions The proximal coronary sinus in patients with AVJRT was significantly different from a control population. The ostium was 44% larger and remained more dilated to at least 10 mm from the ostium. The appearance was like a wind sock in AVJRT patients and tubular in the control patients. These findings may have important implications for arrhythmia pathogenesis in such patients.
Key Words: atrioventricular node tachycardia tachyarrhythmias
| Introduction |
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| Methods |
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Procedures
After the electrophysiological procedure, which
included
coronary sinus cannulation, was completed, a 7F Goodale-Lubin catheter
was advanced from the right femoral vein into the coronary sinus under
fluoroscopic imaging. Angiography was performed in held midexpiration
during hand injection of contrast into the coronary sinus. Angiograms
were obtained in each of four projections (left lateral, 40° left
anterior oblique, anteroposterior, and 30° right anterior oblique)
and stored on reel-to-reel cine tape for subsequent off-line
analysis. Failure to enter the coronary sinus with the angiographic
catheter was defined as inability to achieve a satisfactory placement
for coronary sinus visualization within 15 minutes of when catheter
manipulation was begun. Alternative routes for cannulation were not
attempted. Analysis was performed at a later date using the
cineangiograms with the investigator blinded to patient diagnosis.
The diameter of the coronary sinus ostium was measured in each of the four projections, and the mean value was obtained. Similar measurements were made 5 mm and 10 mm inside the coronary sinus ostium and at 10-mm intervals along the coronary sinus and great cardiac vein, toward the origin of the anterior interventricular vein, consistent with previously published criteria.1 The length of the coronary sinus in each projection was measured, the nature of the venous tributaries was recorded, and structural anomalies were sought. The orifice of the coronary sinus was defined as the point at which the atrial septum above and below the ostium was outlined by contrast flowing out of the vessel and the long axis of the proximal portion of the coronary sinus as it entered the right atrium. All measurements were corrected for the degree of magnification of the angiographic image by relating the diameter of the Goodale-Lubin catheter in each projection to its true diameter. Measurements were made in the still frame that best showed the coronary sinus ostium. The patients were in sinus rhythm, and the mean heart rate was 69 beats per minute in both groups.
Angles were measured in each of the four projections to examine the relation of the coronary sinus origin to the right atrium by relating the direction of the coronary sinus ostium to the vertical, represented by the spine. The angles at which the coronary sinus bodies were derived from the ostium were measured.
Student's t test statistical analysis was performed where appropriate. Results are expressed as mean±SD. Informed patient consent was obtained before angiography.
| Results |
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During the angiographic part of the investigation, it was more difficult to cannulate the coronary sinus in most patients, particularly those with smaller ostium diameters, because of the larger size of the angiographic catheter and its poorer manipulability. In the AVJRT group, 2 patients were excluded from subsequent data analysis, although limited information about them is presented. In 1, an angiogram was obtained in only one projection, while the other, who had previously undergone surgical treatment of congenital supra-aortic stenosis, was found to have a persistent left superior vena cava draining into the distal coronary sinus. Thus, 13 of the 15 AVJRT patients had adequate data for analysis.
Coronary Sinus Dimensions
Coronary Sinus Diameters
The mean coronary sinus ostial diameter from all projections in
patients with AVJRT was significantly larger than that of control
subjects: 12.2±2 versus 8.5±1.5 mm; mean difference, 3.7 mm;
P=.00001. This represents an ostium in AVJRT
patients 44% larger than in control patients. Five millimeters inside
the ostium, the coronary sinus in AVJRT patients was still 26% larger:
10.2±1.8 versus 8.1±1.9 mm; mean difference, 2.1 mm;
P=.007; and 10 mm from the ostium, the vessel remained 18%
wider, with control measurements showing much less tapering: 9.0±1.4
versus 7.6±2 mm; mean difference, 1.4 mm; P=.04. The
range
of mean coronary sinus ostium measurements was 9 to 16.1 mm for the
AVJRT group and 6.5 to 11.3 cm for control patients. Fig 1
shows mean patient values for the ostium and 5 and 10
mm from the ostium for the two patient populations. It demonstrates the
marked proximal dilatation of the AVJRT group and graphically displays
the less dilated and more tubular shape in the control population.
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The
mean maximal measurements from any projection for the two groups
for each of the three proximal points showed similar differences.
The data demonstrate the continued dilatation of the coronary sinus in
patients with AVJRT to 10 mm within the vessel and their greater degree
of tapering of the proximal coronary sinus: ostium, 14.3±2.6 versus
10.4±1.7 mm, P=.0001; 5 mm, 12.2±2.1 versus
9.5±2.2 mm,
P=.0023; 10 mm, 10.4±1.1 versus 8.8±2.5 mm,
P=.03. The range of maximal ostial diameters recorded in any
one of the four angiographic projections was 10.4 to 21.6 mm in AVJRT
patients and 8.5 to 13.4 mm in control patients. In practice, the
maximal coronary sinus dimension in any projection is likely to be most
significant. Figs 2
and 3
illustrate the
differences between the two populations on representative
angiograms.
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The dilatation of the proximal coronary sinus was most
evident in the
left lateral view, in which the sagittal cross section of the ostium
could be seen to best advantage in most patients. The mean diameter in
AVJRT patients was significantly dilated to 30 mm from the ostium. This
proximal dilatation was seen consistently in the left anterior oblique,
anteroposterior, and right anterior projections. Table 1
shows the mean measurements in each group for the first 5 cm of the
coronary sinus in each of the four projections.
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The patient with the persistent left superior vena cava had a massive coronary sinus, with the congenitally persistent vessel draining into the distal coronary sinus. The ostium was 23.5 mm in its widest projection (mean ostial diameter, 22 mm) and was still >15 mm in diameter 50 mm from the ostium.
Coronary Sinus Lengths
The maximal coronary sinus length measured in any of the four
projections was used. Because of the different configurations of the
coronary sinus in the different projections, the mean of the measured
length in the four projections was an unrepresentative value
and was not used.
The AVJRT group had a mean maximal length of 74±20.7 mm (range, 54.8 to 112 mm), which was not significantly longer than the control group, whose mean length was 62.8±18.4 mm (range, 33.9 to 92.4 mm). The left oblique projection was the most useful single projection for the determination of coronary sinus length, giving the longest measurement in 14 patients; the left lateral view in 7 patients; the anteroposterior projection in 7 patients; and the right oblique view in 2 patients. In 3 patients, the same measurement was made in two projections. The left lateral view visualized the coronary sinus length best in the control group in 5 of 14 patients, whereas it was best in only 2 of 13 patients in the AVJRT group. The left oblique projection was most useful in AVJRT patients, displaying the longest vessel in 7 of 13 patients compared with 7 of 14 control patients.
In 4 patients (3 control, 1 AVJRT), there was inadequate visualization of the distal coronary sinus.
Coronary Sinus Morphology
In 11 of the 15 AVJRT patients
(73%), the proximal coronary sinus
had a striking wind-sock appearance, with tapering of the vessel
occurring after 10 mm. In 4 patients (27%), the appearance was of a
tubular structure, with a more gradual tapering of the coronary sinus.
In 2 of these patients, the coronary sinus was long and straight. In 1
patient (7%), the coronary sinus was funnel shaped, with a secondary
dilatation. The measurements for this patient were 10.2 mm at the
ostium, 6.8 mm at 5 mm, 9.1 mm at 10 mm, then 11.4 mm at 20 mm before
narrowing to 9.1 mm at 30 mm. Another AVJRT patient showed a valve at
the ostium that directed the coronary sinus outflow superiorly and
anteriorly.
In the control subjects, only 1 of 14 (7%) showed a wind-sock proximal coronary sinus; the rest (93%) were tubular in form. Five of the control coronary sinuses were very thin, and their appearance was highly attenuated. One control patient with a left posteroseptal accessory pathway had a marked proximal dilatation and aneurysm of the coronary sinus originating at 5 mm from the ostium and continuing to the origin of the middle cardiac vein at 20 mm.
Ten AVJRT patients (67%) had the origin of the posterior interventricular vein within the first 10 mm of the coronary sinus. The average diameter of these vessels was 3.6 mm. In 1 patient, there were paired and small posterior interventricular veins. Of the control population, 5 (36%) demonstrated such an early vessel, 1 with a separate opening. The mean diameter of these vessels was 2.7 mm. The middle cardiac vein was seen at 25 mm from the ostium in AVJRT patients and 29 mm in control patients.
In 8 of the 15 AVJRT patients (53%), the site of the valve of Vieussens or the origin of the oblique vein of Marshall was identified. These observations were made at a mean of 41 mm from the coronary sinus ostium. In the control group, these structures could be identified in only 4 patients (29%) and were found at a mean distance of 40 mm from the ostium. There were no significant differences in the anatomy of the rest of the tributaries.
Coronary SinustoSpine Angles
The mean results
for both patient populations were similar, and in
each group, there was considerable interindividual variability. The
proximal portion of the coronary sinus ran posteriorly with a slight
cranial direction. After the crux, it turned to run more vertically but
at a lesser posterior inclination. The mean angles, SDs, and ranges are
shown in Table 2
.
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| Discussion |
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Relation of Dilated Coronary Sinus Ostium to Mechanism of
AVJRT
The anatomy of the AV nodal region and its electrophysiological
characteristics have received much attention in recent
years,1 2 3 4 5
renewing previous debates about the presence of
specialized AV conducting tracts.6 7 Surgery of the
AV
node in a patient with AVJRT resulted in symptomatic cure without
causing complete heart block,8 indicating that selective
modification of AV nodal function was possible. Refinements of surgical
techniques9 10 allowed a new therapeutic option for
patients refractory to medical therapy. The development of percutaneous
ablation meant that similar modifications to nodal function could be
made with smaller lesions and by a less invasive technique, first by
direct current11 and then by radiofrequency
energy.12 13 The success of ablation, particularly of
"slow-pathway" ablation, reopened debate about the anatomic
features that composed the true or compact node and the role of
perinodal atrial tissue in the mechanism of
AVJRT.14 15 16 17 18
Two approaches to slow-pathway ablation have been promoted: the
"slow-potential-guided" approach, ablating where particular
electrophysiological features are found,14 17 and the
"anatomic" approach, with a gradual stepwise anterocranial series
of burns being applied.15 16 18
The anatomy of the AV junctional area is extremely complex, and discussion of perinodal tissues must consider the entire area comprised by the triangle of Koch. It is now widely accepted that the antegrade input into the compact node occurs via two principal routes. Fibers of the first group are numerically more important in humans and run from the anterior limbus of the fossa ovalis to the AV node, well removed from the coronary sinus (the "fast pathway"). The second, smaller input runs posteroinferiorly around the coronary sinus ostium (the slow pathway).4 5 However, dual or multiple AV pathways may be electrophysiologically identified, without an associated anatomic substrate.3
The variability of inputs to the node has considerable clinical relevance. First, it has allowed the fast and slow pathways to be selectively modified. Second, several authors have demonstrated the site of slow-pathway ablation to be variably located around the mouth of the coronary sinus. Ablation is usually performed anterior to the coronary sinus ostium, in the thin rim of atrial tissue immediately above the tricuspid valve annulus.14 15 19 20 21 22 However, successful ablation in some patients may be performed as far posteriorly as the inferior coronary sinus margin.14 15 Thus, the slow-pathway site exists over a wide area around the coronary sinus ostium at the base of Koch's triangle. Recently, three separate inputs to the node have been identified in the canine heart, existing as discrete anatomic structures superior and anterior, lateral and inferior, and medial and superior to the coronary sinus.23 It remains to be determined whether similar tracts in fact exist in the human heart. Such diversity of inputs may explain continued slow-pathway function after slow-pathway ablation.24
The finding in our study that patients with AVJRT have a larger coronary sinus ostial diameter than a control population with other forms of SVT suggests a possible mechanism for the pathogenesis of the tachyarrhythmia. Dual AV nodal physiology is a frequent laboratory finding3 that may represent a variation of normal and is explained by the presence of more than one atrionodal input to the compact node. Thus, the potential substrate exists for a reentry arrhythmia. The observation that many patients have this potential but do not present with clinical tachyarrhythmias3 implies that there is a further factor important in determining which patients do present with arrhythmias. Inherent to a reentry arrhythmia is the coexistence of unidirectional block and a region of slow conduction. Several authors have demonstrated that slow conduction does not necessarily require that the conduction velocity in this region is subnormal.25 Indeed, it is usually normal. But if an advancing wave front is propagated over a prolonged course or in a direction with greater effective axial resistance, such as might occur around a dilated coronary sinus ostium, the result could be slowed conduction due to anisotropy. This might establish a reentrant tachycardia. Alternatively, the increased coronary sinus ostial diameter might stretch the normal atrial tissue around it, modifying the conduction characteristics of the periostial tissue and creating a potential zone of truly slowed conduction. Previous studies have demonstrated that increased stretch may modify the electrophysiological characteristics of cardiac tissue.26 27 28 It is not known whether patients with dual AV nodal physiology in the absence of reentry arrhythmias have proximal coronary sinus characteristics similar to those of the control population.
Coronary Sinus Morphology in AVJRT and Other SVTs
This is the
first study to measure the size of the coronary sinus
and relate it to pathological arrhythmias. One previous study performed
detailed postmortem analysis of the human heart to determine the
anatomy of the posterior septal space. Their recorded coronary sinus
lengths, primarily in normal hearts, are in keeping with our own
measurements, but there is no description of the effective size of the
coronary sinus mouth.1 Several authors have demonstrated
that coronary sinus abnormalities, particularly diverticula, are
relevant in patients with accessory AV
connections.2 29 30 31 32 33 34 35 36 37
Ablation of pathways in the middle cardiac vein in patients with
posteroseptal accessory pathways is well recognized.
A second published report35 examined the occurrence and significance of major coronary sinus abnormalities in 408 living patients with SVT. Visualization of the coronary sinus was performed during the venous phase of left coronary arteriography. Major coronary sinus abnormalities were defined as one of the following morphological features, partly on the basis of historical details of congenital anomalies found at postmortem examination38 : coronary sinus hypoplasia due to drainage of some of the cardiac venous system directly into the right atrium rather than through the coronary sinus; angulation; localized narrowing; fistulas, eg, persistent left superior vena cava; or presence of diverticulum. The study reported an overall incidence of 3% in SVTs, 5% in patients with accessory pathways, and 1% in AVJRT patients.
If these criteria are applied to our study, 5 of 28 patients (18%) with SVT had a major coronary sinus abnormality. Four of our control patients had a major coronary sinus abnormality (diverticulum in a patient with a left posteroseptal pathway, angulation in another patient with a left posteroseptal pathway, hypoplasia with separate emptying of the posterior interventricular vein into the right atrium in a patient with a right posteroseptal pathway, and ostial narrowing in a patient with a right free-wall connection), representing a 36% incidence of coronary sinus abnormality in accessory pathway patients. In the referenced report,35 the abnormalities were associated exclusively with left-sided pathways, an observation not supported by our study. One of the AVJRT patients (7%) in our study had a major coronary sinus abnormality (persistent left superior vena cava). The difference in frequency of recognition of major coronary sinus abnormalities is explained by the better visualization of the coronary sinus by direct injection of contrast.
The finding that control patients have tubular coronary sinus morphology, whereas patients with AVJRT have wind-sock proximal coronary sinuses, has not previously been described.
Cineangiography in these patients confirmed the phasic nature of epicardial coronary venous and coronary sinus flow, confirming work previously performed only in the dog.39
Facilitation of Coronary Sinus Cannulation in Patients With
AVJRT
The performance of this study confirmed our impression that
access
to the coronary sinus in patients with AVJRT was easier than in
patients with other forms of SVT. This is explained by the
morphological differences of the proximal coronary sinus between the
two groups, rather than because of a more favorable angle of origin
from the right atrium. The success of the femoral approach for coronary
sinus placement has been reported before.40
Limitations of This Study
Patients without supraventricular
arrhythmias were not included in
this investigation. It would have been unethical to cannulate the
coronary sinus in patients who had not undergone this procedure as part
of their electrophysiological study. We felt that it would be
inappropriate to use venous phase imaging of left coronary angiography
as a second control population because of the poorer imaging
characteristics and greater radiation exposure.
Confirmatory evidence of the proximal coronary sinus enlargement by use of another imaging technique would have been helpful. Transthoracic echocardiography (performed routinely at 24 hours after ablation) was deemed too insensitive to successfully detect the degree of dilatation identified in this study. This test did identify the dilated coronary sinus in the patient with the persistent left superior vena cava. Transesophageal echocardiography was thought to be too invasive without clinical indication.
Clinical Implications
Patients with AVJRT have larger and
morphologically distinct
proximal coronary sinus characteristics compared with patients with
other forms of SVT. The ostium was 44% larger than in a control
population with other types of SVT and typically had the appearance of
a wind sock. These findings explain the easier catheterization of the
coronary sinus in patients with AVJRT and may explain why some patients
with electrophysiologically demonstrable dual AV conduction present
with AVJRT.
| Acknowledgments |
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Received December 5, 1994; revision received January 23, 1995; accepted January 30, 1995.
| References |
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