Coronary ostial morphology after modified Bentall operation assessed with dual-source multidetector computed tomography

Journal of Cardiovascular Computed Tomography (2010) 4, 206–212

Technical Notes

Coronary ostial morphology after modified Bentall operation assessed with dual-source multidetector computed tomography Austin Chin Chwan Ng, MBBS, BSc(Med), MMed, FRACPa, John Yiannikas, MBBS, FRACPa, Andy Sze Chiang Yong, MBBS(Hons), FRACPa, Lloyd Ridley, MRBS, FRANZCRb, Michael Keith Wilson, MBBS, FRACSc, Leonard Kritharides, MBBS, PhD, FRACPa,* a

Cardiology Department, Concord Hospital, The University of Sydney, Hospital Road, Concord 2139, NSW, Australia; Radiology Department, Concord Hospital, The University of Sydney, Hospital Road, Concord, Australia and c Cardiothoracic Surgery Department, Concord Hospital, The University of Sydney, Hospital Road, Concord, Australia b

KEYWORDS: Aneurysm; Aortic operation; Computed tomograph; Coronary artery imaging

Abstract. During the modified Bentall operation (aortic root replacement), a cuff of native aorta is commonly implanted together with the coronary ostium into the aortic graft. We describe the radiologic appearance on computed tomography of coronary-aortic and aorto-aortic graft anastomoses over longterm follow-up in 21 consecutive asymptomatic patients (mean age, 67 6 12 years) with previous Bentall operation. Multidetector (64-slice, dual-source) computed tomography was performed at a median of 76 months after surgery. One patient had asymptomatic aortic dissection that extended into the carotid artery. Seven patients had aortic dilation R40 mm distal to the graft. All patients had dilation at the postsurgical coronary ostia-aortic attachment: mean coronary ostial diameter was 12.8 6 3.6 mm, which was on average 1.7-fold greater than the adjacent proximal coronary vessel diameter. All patients had at least one ostium R10 mm in diameter. In 16 patients, both coronary ostia were R10 mm. There was no relationship between time after surgery and the ostial diameter. In patients with accessible presurgery angiograms, no relationship was observed between ostial diameters before and after surgery. Dilation of the coronary ostia anastomosis site is typical after the modified Bentall operation. Asymptomatic aortic pathology is also evident in this population. Ó 2010 Society of Cardiovascular Computed Tomography. All rights reserved.

Introduction Early surgical intervention is recommended for large supravalvular aortic aneurysm because of increased risk of Conflict of interest: The authors report no conflicts of interest. * Corresponding author. E-mail address: [email protected] Submitted September 29, 2009. Accepted for publication March 9, 2010.

dissection or rupture.1 Aortic root replacement described by Bentall involved directly suturing the aortic wall around the coronary ostia to the graft.2 This was complicated by bleeding and pseudoaneurysm formation caused by excess wall tension and tearing of partial thickness sutures. The modified Bentall procedure addressed these problems by mobilizing the coronary ostia with a button of aortic wall (Fig. 1).3 The mobilization reduced wall tension, and the button of aortic wall allowed full-thickness accurate suture placement around the ostia.

1934-5925/$ -see front matter Ó 2010 Society of Cardiovascular Computed Tomography. All rights reserved. doi:10.1016/j.jcct.2010.03.008

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Cardiac imaging in post-Bentall patient

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There are few detailed studies of the ostial anastomoses with the use of modern imaging techniques.4 Dual-source and multidetector computed tomography (MDCT) scanners show improved temporal and spatial resolutions, respectively,5 and may therefore have an important role in evaluating the coronary ostia of patients after Bentall surgery.

Technical methods We recruited 21 consecutive patients over 15 months that had prior modified Bentall surgery referred for an elective computed tomography (CT) examination of their aortic root and aorta. Clinical information collected included indications for surgery, original pathology, comorbidities, echocardiogram, original operation report, and associated histopathology reports. Nine patients had original catheter angiograms accessible for review. With the use of the coronary catheter diameter (Judkins-6F) as reference, the diameters of the native coronary arteries were measured (calliper technique).6 Patients underwent imaging examination with a dualsource 64-slice MDCT scanner (Definition; Siemens Medical Solutions, Forchheim, Germany). Scanning parameters were 120 kV for both tubes, 400 mA of current with modulation (full current between 30% and 80% of the cardiac cycle), gantry rotation time of 0.33 seconds, pitch of 0.2–0.44 adapted to the heart rate, and a collimation of 0.6 mm. Contrast (100 mL; Omnipaque 350; Amersham Health, Princeton, NJ) followed by 81 mL of saline injected at 3.5 mL/s. Bolus tracking (when aortic root image density value exceeded 100 Hounsfield units) was used to initiate the scan after 8 seconds of monitoring delay. Axial images were reconstructed at 0.6-mm slice thickness and 0.3-mm increment, using retrospective electrocardiographic gating. A medium-soft convolution kernel was used (B25F). Nitroglycerine was not used to eliminate any potential confounder when measuring coronary artery diameters. In our institution, b-blockade during coronary MDCTangiogram is given when resting heart rate exceeds 80 beats/min. The CT scans were analyzed offline (Syngo Circulation; Siemens Medical Solutions). Measurements were performed from the ‘‘best diastole’’ data set. The coronary ostial diameter was measured at the coronary ostial-aortic graft junction. Multiplanar reconstructions (0.6 mm) were manipulated to obtain an image perpendicular to the aortic root at the level of the coronary ostium that showed the greatest ostial dilation on visual assessment. A soft tissue window was used (600/200). The dilated postsurgical ostium typically tapered to the proximal vessel at a discrete angle, and the proximal vessel diameter was measured from a nontapering segment of the coronary artery after the dilated proximal segment (Fig. 2). The postsurgery coronary ostia mostly appeared concave shaped (Fig. 2A), whereas others were more convex shaped (Fig. 2D). All statistical analyses were performed with PRISM4.03 (GraphPad Software Inc, San Diego, CA). Data are

Figure 1 Example of a Bentall procedure (aortic root replacement) with the button technique. The larger arrow points to the mobilized native left coronary artery with a ‘button’ or cuff of aortic tissue. The coronary ostia button is then sutured to a circular fenestration created in the aortic graft (smaller arrow).

presented as mean 6 standard deviation. A 2-tailed probability value ,0.05 was considered statistically significant. The institution ethics committee approved the study.

Technical results All patients (mean age, 67 6 12 years; 17 males) had severe presurgery aortic root dilation (mean diameter by echocardiogram, 52.0 6 4.2 mm), and all underwent elective surgery apart from one patient (patient no. 12) who presented with spontaneous ascending aortic dissection (Table 1). The median interval between surgery and MDCT scan was 76 months. Mean heart rate was 66 6 17 beats/min during the MDCT scan. The mean diameter of the aorta just distal to the aortic graft was 38.2 6 5.2 mm. Seven patients had aortic diameter . 40 mm distal to the graft. The mean coronary ostial diameter was 12.8 6 3.6 mm (ostial left main coronary artery [LMCA], 13.9 6 3.8 mm vs ostial right coronary artery [RCA], 11.8 6 3.1 mm;

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Table 1

Individual patient CT characteristics Original pathology

Time to CT, mo

LMA ostium, mm

Prox. LMA, mm

RCA ostium, mm

Prox. RCA, mm

Histopathology of excised aortic wall

1

AR. Dilated aortic root.

121

14

7

13

5

2

Bicuspid AV. AR. Dilated aortic root.

105

14

5

5

5

Mucinous degeneration in media. Mild–moderate intimal thickening with irregular fibrous replacement. —

3 4

AR. Dilated aortic root. Dilated aortic root.

57 92

13 18

5 5

10 18

4 3

Atheromas. Atheromas.

5

Bicuspid AV. AR. Dilated aortic root.* AR. Dilated aortic root.

107

16

5

10

4

—

70

11

6

9

3

Moderate myxoid degeneration. Atheromas. Degenerative changes in the wall and accumulation of myxoid material. Mild myxoid degeneration.

6 7

Bicuspid AV. Dilated aortic root.

40

13

5

9

6

8

62

10

4

8

4

9

Bicuspid AV. Dilated aortic root. AR. Dilated aortic root.

100

15

5

13

4

Degenerative changes with mild chronic inflammation.

10

AR. Dilated aortic root.

83

11

5

17

6

11

Bicuspid AV. Dilated aortic root.

47

26

4

10

5

Disruption of the elastic fibers associated with patchy fibrosis. Focal splitting of the media. Atheromas. Mild medial fibrosis.

12

Stanford Type A aortic dissection.

72

15

4

14

5

Cystic medial degeneration.

Comments —

Moderate dilatation of the ascending aorta (diameter, 50 mm) above the Bentall graft. — The left coronary artery has an aberrant origin from the right coronary cusp. — — —

— Moderate dilatation of the ascending aorta (diameter, 51 mm) above the Bentall graft. —

Mild dilatation of the ascending aorta (diameter, 41 mm) above the Bentall graft. Stanford type A aortic dissection with extension up into right common carotid artery.

Journal of Cardiovascular Computed Tomography, Vol 4, No 3, May/June 2010

No.

68

12

6

11

5

14

AR. Dilated aortic root.*

33

16

7

14

3

15

AR. Dilated aortic root.

59

11

6

14

6

16

AR. Dilated aortic root.*

114

12

5

10

3

17

119

12

7

10

4

18

Severe AS; moderate AR. Dilated aortic root. AR. Dilated aortic root.

92

9

6

14

6

19

AR. Dilated aortic root.*

76

10

6

10

6

Disruption of elastic fibres and accumulation of myxoid material. Atheromas.

20 21

AR. Dilated aortic root. Bicuspid AV. AR. Dilated aortic root.

120 24

14 19

7 6

13 15

4 4

Atheromas. Cystic medial degeneration.

13.9 (3.8)

5.5 (1.0)

11.8 (3.1)

4.5 (1.1)

Mean (standard deviation)

79 (30)

Atheromas. Focal mucinous degeneration. Atheromas.

Atheromas. Disruption of elastic fibres and accumulation of myxoid material. Atheromas. Disruption of elastic fibres and accumulation of myxoid material. Focal chronic adventitial inflammation. Atheromas.

— Extensive fusiform aneurysm (diameter, 47 mm) with thrombus involving descending thoracic aorta Moderate dilatation of the ascending aorta (diameter, 46 mm) above the Bentall graft. —

— —

Had hemiarch replacement with initial Bentall operation — —

Cardiac imaging in post-Bentall patient

AR. Dilated aortic root.

Chwan Ng et al

13

AR, aortic regurgitation; AV, aortic valve; CT, computed tomography (multidetector); LMCA ostium, left main coronary artery measured at its ostium; RCA ostium, right coronary artery measured at its ostium; Prox., proximal segment. *Patient also had combined coronary artery bypass grafting during the Bentall procedure.

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Figure 2 Examples of coronary ostial dilation. (A) Diagram of concave-shaped ostium; (B and C) examples of concave-shaped coronary ostia; (D) diagram of convex-shaped ostium; (E and F) examples of convex-shaped coronary ostium. OD, ostial diameter; PV, proximal vessel. The dotted double arrowhead marks the ostium of the coronary vessel in the figures. The bold arrow points to the coronary ostia.

P 5 0.049), whereas the mean proximal coronary diameter was 5.0 6 1.1 mm (proximal LMCA, 5.5 6 1.0 mm [range, 7 mm] vs proximal RCA, 4.5 6 1.1 mm [range, 3–6 mm]; P 5 0.007). The coronary ostial diameters were 1.7-fold that of their corresponding proximal coronary segments, with LMCA and RCA similarly affected (ostial diameters being, respectively, 163% and 176% of proximal coronary diameters). Of the 42 coronary ostia, only 1 had a diameter , 6 mm. No correlation was observed between the diameters of the ostium and the proximal segment of the coronary arteries. In addition, no consistent structural differences were observed between left and right coronary ostia (LMCA: 18 concave, 3 convex; RCA: 17 concave, 4 convex), although structural discordance between the coronary ostia was observed in 7 patients. Importantly, neither the ostial diameter (LMCA: r 5 0.27, P 5 0.24; RCA: r 5 0.07, P 5 0.76) nor the ratio of ostial diameter to proximal vessel diameter (LMCA: r 5 0.28, P 5 0.22; RCA: r 5 0.03, P 5 0.91) correlated with time after surgery, suggesting that this is unlikely to be a progressive, time-dependent process. To investigate the possibility that these patients had significant coronary dilation before surgery, we sought presurgery angiograms. In the 9 patients with retrieved angiograms, postsurgical coronary ostia analyzed by MDCT were

significantly larger than presurgery ostia analyzed by coronary catheter angiography for both the right (mean diameter, 10.9 6 2.4 mm vs 4.5 6 0.9 mm, P 5 0.0001) and left (14.2 6 5.3 mm vs 7.0 6 2.2 mm; P 5 0.001) coronary vessels (Fig. 3). The proximal segments of the RCA (4.6 6 1.1 mm) and the LMCA (5.6 6 1.0 mm) assessed by current MDCT were not significantly different to presurgical ostial (RCA, 4.5 6 0.9 mm; LMCA, 7.0 6 2.2 mm) or proximal (RCA, 3.3 6 0.9 mm; LMCA, 5.4 6 0.7 mm) diameters, suggesting a focal process affecting the aorto-coronary anastomosis.

Discussion In this consecutive series of 21 asymptomatic patients with previous modified Bentall surgery studied with dualsource 64-slice MDCT, apparently dilated postsurgical coronary ostia are typical. Although the lack of CT scans before surgery makes our estimation of the precise extent of postsurgical dilation imprecise, the coronary ostial diameters were 1.7-fold that of their corresponding proximal coronary segments and appear to be larger than the CT scan coronary ostial diameters of healthy subjects.7 The lack of significant dilation in the proximal vessel segment may indicate it is the preserved native aortic tissue that contributes to apparent

Chwan Ng et al

Figure 3 Comparison of postsurgery MDCT and presurgery angiographic diameters. Ostial and proximal vessel diameters before surgery (Pre-Ostium and Pre-Prox, respectively, measured with the use of invasive angiography) versus post-surgery (Post-Ostium and Post-Prox, respectively, with the use of MDCT), n 5 9. (A) Left main coronary artery; (B) right coronary artery.

ostial dilation. It is possible that this effect has been exaggerated by aortic pathology within the excised native aortic button tissue. However, because ostial dilation was also seen in patients with only atheromatous change on histopathology (Table 1), it seems more likely this relates to the surgical procedure rather than to specific aortic pathology. No patients in our study had pseudoaneurysm. This is consistent with the very low rate of coronary ostia-graft anastomotic site complications reported by others (Table 2).3,4,8–14 Our cohort extends previous reports in several important respects. First, none of our patients had a definitive diagnosis of Marfan syndrome, suggesting that postsurgical ostial dilation does not require clinical Marfan syndrome to be present. Second, almost all patients had significant postsurgical coronary ostial dilation, suggesting this is a

Cardiac imaging in post-Bentall patient

Table 2

Coronary ostia-graft anastomotic site complications post-modified Bentall surgery

Reference

N 3

Duration after surgery

Imaging modalities

Coronary ostial-graft anastomotic site No pseudoaneurysm reported. No pseudoaneurysm reported. No pseudoaneurysm reported. No pseudoaneurysm reported; 13 patients had coronary ostial diameter R10mm. No pseudoaneurysm reported. No pseudoaneurysm reported. MRI detected a pseudoaneurysm of right coronary ostial anastomosis after 18 months and left coronary dilation at angiography after 23 months. No pseudoaneurysm reported. No pseudoaneurysm reported.

Kouchoukos et al (retrospective study) Fattori et al8 (cross-sectional study) Panos et al9 (retrospective study) Meijboom et al10 (cross-sectional study)

47 25 65 30

Up to 8 y Range, 0.5–200 mo Mean, 71 6 51 mo Mean, 3 6 2 y

NA MRI NA MRI

Ruvolo et al11 (cross-sectional study) Gelsomino et al12 (retrospective study) Milano et al4 (prospective study)

93 72 71

Mean, 51 6 34 m Mean, 87 6 24 mo Mean, 49 6 19 mo

Echo and/or CT Echo Echo at 6-mo intervals and CT annually; 20 patients had MRI and coronary angiography. NA CT annually

Zehr et al13 (retrospective study) Etz et al14 (retrospective study)

118 206

Mean, 7 6 6 y Median, 5.9 y

Only patients who had undergone modified Bentall surgery were included from each study. CT, computed tomography; Echo, echocardiography; MRI, magnetic resonance imaging; NA, not available (no follow-up imaging study described).

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typical response to this surgical procedure. Third, most postsurgical coronary ostial diameters in our study were R10 mm, emphasizing the extent of apparent dilation is greater than previously recognized. Finally, because there was no correlation between the size of the coronary ostium and time after surgery, progressive dilation of the aortic button tissue is unlikely. In those patients in whom presurgery angiograms could be reanalyzed, postsurgical coronary ostial diameters were significantly greater than presurgical diameters, suggesting that these appearances were not present before surgery. We interpret the postsurgical images as indicating that the proximal vessel segment diameter in MDCT represents the original native vessel, whereas the MDCT coronary ostial diameter represents the button or aortic cuff tissue that was excised and reimplanted onto the aortic graft. The coronary ostia button is sutured to a circular fenestration created in the graft material with the use of an ophthalmic cautery. The aortic wall is elastic, sutured in a relaxed state, and then exposed to systemic arterial pressure. If the surgical fenestration is relatively larger than the ostia and there is good size match between the outer ostial diameter and the fenestration diameter, then with systemic pressurization, a conical dilation of the button aortic tissue is likely to result. However, if the coronary ostial diameter is larger than the fenestration diameter and this discrepancy is carefully sutured, a spherical dilation of the button aortic tissue is then more likely to occur. Obviously, the ostial anastomosis is critical, and kinking or twisting may result in occlusion or low flow. A larger anastomosis allows for a margin of error and may explain the MDCT findings of this study. Given these findings, it may be prudent to ensure a carefully sized matched anastomosis until it is proven that there is no progressive dilation of residual aortic wall. With the use of 64-slice dual-source MDCT scanner, a systematic assessment of the coronary ostial anastomotic site of patients after Bentall surgery has identified that dilation of the coronary ostia is common and apparently stable, although very long-term consequences of these ostial dilations remain unknown. Furthermore, our conclusion about the lack of coronary dilation before surgery would be strengthened in future studies by comparing MDCT before and after surgery in all patients. The finding of asymptomatic aortic pathology beyond the graft in the current cohort emphasizes the need for long-term follow-up of these patients.

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