indications for ascending aortic replacement: size alone is not enough

Journal of the American College of Cardiology Vol. 58, No. 6, 2011© 2011 by the American College of Cardiology Foundation ISSN 0735-1097/$36.00Published by Elsevier Inc. doi:10.1016/j.jacc.2011.03.041

EDITORIAL COMMENT

Indications for AscendingAortic ReplacementSize Alone Is Not Enough*

Donald D. Glower, MD

Durham, North Carolina

Literature over the last 2 decades has progressively loweredthe threshold for ascending aortic replacement at the time ofaortic valve replacement. Current American College ofCardiology (ACC)/American Heart Association (AHA)guidelines recommend replacing the ascending aorta at thetime of aortic valve replacement if the ascending aorta ismore than 5.0 cm in any patient or if the ascending aorta ismore than 4.5 cm in bicuspid patients (1). Yet, despite thesimplicity of these guidelines, many factors play a role indetermining the indications for ascending aortic replace-ment to prevent ascending aortic complications. In additionto increased absolute aortic diameter, observed to expectedaortic diameter ratio (2), genetics (3), rate of aortic expan-sion (2,3), body size (1,3,4), smoking (5), and hypertension(5) have been demonstrated to be influential.

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The bicuspid aortic valve is known to be a phenotypeassociated with many genotypes, some of which are consid-ered to be “connective tissue” disorders (3,6). For a givenascending aortic diameter, the presence of a bicuspid aorticvalve has been associated with increased risk of aorticcomplications relative to a tricuspid aortic valve (3). In otherwords, the presence of a tricuspid aortic valve would beexpected to have less risk of aortic complications than abicuspid valve of the same diameter.

The work by Gaudino et al. (7), in this issue of theJournal, is one of the few studies to examine the naturalhistory of the ascending aorta in patients with tricuspidaortic valves. Only a few small reports have providedoutcome data for patients with enlarged ascending aortas inthe absence of either Marfan syndrome or bicuspid disease(8,9). Michel et al. (9) noted that in patients undergoingaortic valve replacement alone for degenerative aortic regur-

*Editorials published in the Journal of the American College of Cardiology reflect theviews of the authors and do not necessarily represent the views of JACC or theAmerican College of Cardiology.

From the Department of Surgery, Duke University Medical Center, Durham,North Carolina. Dr. Glower has reported that he has no relationships to disclose.

gitation with an ascending aorta of more than 4.0 cm, 25 ofthese patients subsequently required ascending aortic re-placement.

Most studies have focused on the size threshold for com-plications for patients with Marfan syndrome, bicuspid pa-tients (6,10), or mixed populations that include bicuspid valves(4,5,11). In fact, studies cited to justify the replacement ofaortas larger than 5.0 cm all examined mixed populations thatincluded bicuspid valves (1,3,5,12,13). Other studies of mixedbicuspid and tricuspid populations still found 6.0 cm to be thepoint at which risk of aortic complications increases dramati-cally in unoperated patients (3,13).

Gaudino et al. (7) provide convincing data that at leastsome patients with a tricuspid aortic valve and an ascendingaortic diameter of 5.0 to 5.9 cm can have the ascendingaorta left alone during aortic valve replacement, contrary toACC/AHA guidelines (1). In 93 consecutive patients un-dergoing isolated replacement of a tricuspid aortic valvewith a 5.0 to 5.9 cm ascending aorta left intact, no patientsuffered an aortic complication or significant aortic enlarge-ment over a mean follow-up of 14 years. The researchersconcluded that the increase in operative risk related toascending aorta surgery does not appear justified in patientswith moderate post-stenotic dilation (�6.0 cm) of theascending aorta in the absence of connective tissue disease.

The data of Gaudino et al. (7) do have limitations. The factthat only 93 patients came to surgery with aortas of 5.0 to 5.9cm, whereas 381 patients came to surgery with aortas �5.9 cmsuggests a referral bias in which patients with aortas of less than6.0 cm were less likely to be referred for surgery. We do notknow how many patients with aortas of 5.0 to 5.9 cm rupturedtheir aortas without referral to surgery in this referral network.Furthermore, we do not know if patients in the study byGaudino et al. (7) might have been larger, if there might havebeen more men, or if the patients were less likely to have aorticregurgitation than other series, making aortic sizes respectivelylarger. Nonetheless, it is remarkable and important that noneof the 93 patients who did have surgery for aortas 5.0 to 5.9mm ever developed an aortic complication, and none everneeded aortic replacement.

One could also question the assumption of Gaudino et al.(7) that addition of ascending aortic grafting adds signifi-cant risk to an aortic valve replacement. The risk of aorticvalve replacement alone may be 1% to 5%, whereas the riskof aortic valve replacement with ascending aortic graftinghas similarly been reported at 2.5% to 5% (6). Thus, failingto graft the ascending aorta at the time of aortic valvereplacement only makes sense if the risk of leaving theascending aorta alone is less than approximately 3% (thedifference between aortic valve replacement without vs. withaortic grafting). In the current study, the risk of leaving theascending aorta alone was 0 of 93 (0%), which would havea 95% confidence interval of 0.0% to 3.5%. In short, thisstudy, as large as it were, is marginally powered to demon-

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586 Glower JACC Vol. 58, No. 6, 2011Ascending Aortic Replacement August 2, 2011:585–6

ascending aorta alone is �3%. The ability to achieve a 0 of93 (0%) mortality by leaving the ascending aorta alone does,however, suggest that further study is warranted.

Clearly these data will need to be confirmed by otherinvestigators. Yet the article is important in adding new datafrom a reasonably sized series with excellent follow-up. Shouldthe results of Gaudino et al. (7) be confirmed, then ACC/AHA guidelines should be made more specific regardingdifferent patient groups (e.g., Marfan, bicuspid, tricuspid), as inTable 1 (2). Other disease etiologies (such as degenerativeortic regurgitation or chronic dissection) might require morer less aggressive approaches than the 3 etiologies in Table 1 (2,9).

Thus, evidence supports the contention of Gaudino et al. (7)hat size alone is not enough to indicate replacement of thescending aorta in many patients with aortas of less than 6.0m in diameter. Other factors such as disease etiology, genetics,ate of enlargement, body size, hypertension, quality of theorta itself, and concurrent indication for cardiac surgery allust be considered. Guidelines are just guidelines. Guidelines

eed to be applied to individual patients by knowledgeablehysicians.

Reprint requests and correspondence: Dr. Donald D. Glower,Box 3851, Duke University Medical Center, Durham, North

Etiology-Specific Guidelines for Ascending AorticReplacement: Aortic Diameter Threshold forAscending Aortic Replacement*Table 1

Etiology-Specific Guidelines for Ascending AorticReplacement: Aortic Diameter Threshold forAscending Aortic Replacement*

Marfan Syndrome Bicuspid Tricuspid Non-Marfan

With AVR, cm 4.0 4.5 (5.0) 6.0

Without AVR, cm 4.5 5.0 (5.5) 6.0

*Subject to further study and adjustment for body size, rate of enlargement, and other factors.Current guidelines/practice are in parentheses.

AVR � aortic valve replacement.

Carolina 27705. E-mail: glowe001@mc.duke.edu.

REFERENCES

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Key Words: aneurysm y aorta y surgery.