Case Study

Aortic dissection one year after aortic valve replacement

Asian Cardiovascular & Thoracic Annals 2014, Vol. 22(9) 1099–1102 ß The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0218492313493793 aan.sagepub.com

Ali Asgar Behranwala1, Shyam R Handa2 and Nihar P Mehta2

Abstract Acute aortic dissection after aortic valve replacement is rare. A 57-year-old man presented with an acute type A aortic dissection 1 year after aortic valve replacement, which originated from the previous aortotomy site. He underwent a Bentall procedure. Postoperatively, he developed complete heart block requiring permanent pacemaker implantation. During aortic valve replacement, risk factors for aortic dissection (diameter of the aorta and fragility and thinness of the aortic wall) should be assessed. Prophylactic aortic root replacement should be undertaken if the aortic root is more than 45 mm in diameter.

Keywords Aortic dissection, aortic aneurysm, post aortic valve replacement, complete heart block, pacemaker, Bentall procedure

Introduction The occurrence of acute aortic dissection after aortic valve replacement (AVR) is rare, reported as 0.6% or less.1 Among patients with aortic dissection, previous AVR had been performed in 9%–10%.1 The hospital mortality in patients with type A dissection managed surgically is 26%, whereas mortality among those not receiving surgery is as high as 58%.2 Dissection can occur at any time from 1 month to 16 years after AVR.3 We describe a case of acute type A aortic dissection 1 year after AVR.

Case report A 57-year-old man underwent AVR for severe aortic regurgitation and remained asymptomatic for one year after his surgery until he suffered severe chest pain radiating to the back and left arm, with perspiration. He presented to a local hospital where echocardiography and computed tomography showed type A aortic dissection. He was started on medication to control his blood pressure and was referred to our hospital for further management. His electrocardiogram showed right bundle branch block. Echocardiography showed an aneurysm of the ascending aorta measuring 58 mm

in diameter with a dissection flap just distal to the normally functioning prosthetic valve. Computed tomography showed an aneurysm of the aortic root, ascending aorta and arch, with diameters of 56, 49, and 41 cm, respectively (Figures 1 and 2). A Stanford type A dissection was seen with an intimal flap in the ascending aorta, extending throughout the aortic arch, descending thoracic and abdominal aorta, and into the left common iliac artery. The celiac artery and both renal arteries arose from the true lumen. The intimal flap straddled the origin of the superior mesenteric artery, and the inferior mesenteric artery arose from the false lumen. The true and false lumens were of equal size. Surgery was undertaken through a median sternotomy. The ascending aorta had an aneurysm just after the coronary ostia. A large dissection was seen starting at the level of the previous aortotomy 1 Department of Cardiovascular Thoracic Surgery, Jaslok Hospital and Research Centre, Mumbai, India 2 Department of Cardiology, Jaslok Hospital and Research Centre, Mumbai, India

Corresponding author: Nihar Mehta, MD, DNB, Department of Cardiology, Jaslok Hospital and Research Centre, 15 G Deshmukh Marg, Mumbai 400026, India. Email: [email protected]

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and extending towards the left coronary ostium. The wall of the aortic aneurysm was fragile and thinned out. The prosthetic aortic valve showed pannus formation along with a few small clots. It was resected and a Bentall procedure was performed. A size-22 St. Jude composite valve graft was implanted. The coronary arteries were reimplanted. The computed tomography findings regarding the aortic arch vessels were confirmed, hence aortic arch replacement was not necessary. Just after the innominate artery, the true and false lumens were sutured to form a single lumen.

The conduit was attached to the newly created lumen. Postoperatively, the patient developed complete heart block and underwent implantation of a VDD permanent pacemaker 1 week postoperatively. The remaining course was uneventful and he was discharged 10 days after surgery. He was followed up 1 month later and a computed tomography aortogram showed persistence of the dissection flap from the junction of the ascending aorta and the aortic arch up to the descending aorta bifurcation (Figures 3 and 4). The flap extended into the origin of the superior mesenteric artery, but all

Figure 1. Computed tomography showing extensive dissection of the aorta, progressing from the arch to the descending aorta.

Figure 3. (a) Postoperative computed tomography showing the conduit in the ascending aorta and true lumen. There is partial thrombosis of the false lumen. (b) Reconstructed computed tomography image.

Figure 2. (a) Computed tomography showing the dissection extending into the arch of the aorta (b) Computed tomography showing the dissection in the ascending and descending aorta.

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Figure 4. (a) Postoperative computed tomography showing the true and false lumens in the ascending and descending aorta. (b) Postoperative computed tomography showing the true and false lumens in the arch of the aorta.

other major vessels arose from the true lumen. There was partial thrombosis of the blood in the false lumen. He was continued on medical management.

Discussion During AVR, risk factors predisposing to aortic dissection should be assessed to determine which patients should undergo prophylactic aortic root replacement to avoid a catastrophic aortic dissection in the future. These include hypertension, seen in 33% of patients with dissection after AVR.4,5 Dissection at the clamping or cannulation site on the ascending aorta can occur intraoperatively or within one month after surgery,4 but it is not associated with late aortic dissection after AVR. No association has been found between aortic crossclamp time, concomitant coronary artery bypass, or type of prosthesis.3 Thus dissections late after AVR are usually not related to specific operative techniques. However, our patient’s dissection did originate from the previous aortotomy site. Dilatation of the aortic root occurs due to hemodynamic stress or a congenital or acquired weakness of the aortic wall. In bicuspid aortic valves with aortic regurgitation, progressive root dilatation may not be prevented even after AVR, despite elimination of hemodynamic stress.5 Fragility and thinness of the aortic wall are independent predictors of dissection after AVR, carrying a 64% and 79% risk of late aortic dissection, respectively; if both are present, the risk of late dissection increases to 96%.4 During reoperation, our patient’s aortic wall was found to be fragile and thin at the aortic root and ascending aorta. Cystic medial necrosis was found in 39% of post-surgical dissections, but a statistical association could not be established.4

Treatment for aortic dilatation should be carried out prophylactically during AVR if the diameter of the aortic root exceeds 45 mm. Patients with a mildly dilated aortic root should be followed up with echocardiography every 6 months after AVR. Elective ascending aortic root replacement should be considered if the diameter of the ascending aorta increases above 50 mm,6 especially in the presence of systemic hypertension. Our patient’s aortic root was 56 mm before reoperation. This would have been an indication for elective replacement of the aortic root, even in the absence of dissection. During his first AVR, he had none of the risk factors that would have warranted prophylactic aortic root replacement. An unusual feature in our patient was the origin of the dissection from the aortotomy site. Our patient’s prosthetic valve showed pannus and a few clots, which made it mandatory to replace the valve. Another option would have been to leave the prosthesis in situ and suture an aortic graft to the prosthesis with reimplantation of the coronary arteries. Our patient also developed complete heart block postoperatively, requiring permanent pacemaker implantation. Permanent pacemakers are required in 3.2% to 8.5% of patients undergoing AVR.7,8 Various mechanisms have been suggested, such as fibrous thickening of the endocardium of the septum, ischemia, impingement of the conduction tissue by the prosthetic valve, and age-related degeneration of the conduction system. There are no reliable predictors of permanent pacemaker requirement after AVR, but preoperative conduction system disease, aortic regurgitation, and a large valve prosthesis appear to be risk factors. Our patient had right bundle branch block preoperatively, which increased his chances of requiring a permanent pacemaker postoperatively.

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Conclusion It is important to assess the risk of aortic dissection in patients undergoing AVR. The main risk factors are the size of the aorta and the fragility and thinness of the aortic wall.4 Prophylactic aortic root surgery should be carried out if the aortic diameter is more than 45 mm. On follow-up, elective aortic root surgery should be undertaken if the diameter of the aortic root increases beyond 50 mm.6 This is justified on the basis of the lower mortality rate of elective aortic surgery compared to emergency surgery for acute aortic dissection. It is also important to access the risk of complete heart block and requirement of PPM after AVR. The predictors are preoperative conduction defects and the presence of AR.

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Funding This research received no specific grant from any funding agency in the public, commerical, or not-for-profit sectors.

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Conflict of interest statement None declared.

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References 1. von Kodolitsch Y, Loose R, Ostermeyer J, et al. Proximal aortic dissection late after aortic valve surgery: 119 cases of

a distinct clinical entity. Thorac Cardiovasc Surg 2000; 48: 342–346. Hagan PG, Nienaber CA, Isselbacher EM, et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA 2000; 283: 897–903. Pieters FA, Widdershoven JW, Gerardy AC, Geskes G, Cheriex EC and Wellens HJ. Risk of aortic dissection after aortic valve replacement. Am J Cardiol 1993; 72: 1043–1047. von Kodolitsch Y, Simic O, Schwartz A, et al. Predictors of proximal aortic dissection at the time of aortic valve replacement. Circulation 1999; 100(Suppl II): 287–294. Masuda Z, Murakami T, Shishido E and Kuinose M. A rare cause of dissection of ascending aorta after aortic valve replacement. Asian Cardiovasc Thorac Ann 2008; 16: e4–e6. Prenger K, Pieters F and Cheriex E. Aortic dissection after aortic valve replacement: incidence and consequences for strategy. J Card Surg 1994; 9: 495–498. Dawkins S, Hobson AR, Kalra PR, Tang AT, Monro JL and Dawkins KD. Permanent pacemaker implantation after isolated aortic valve replacement: incidence, indications, and predictors. Ann Thorac Surg 2008; 85: 108–112. Limongelli G, Ducceschi V, D’Andrea A, et al. Risk factors for pacemaker implantation following aortic valve replacement: a single center experience. Heart 2003; 89: 901–904.

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Aortic dissection one year after aortic valve replacement.

Acute aortic dissection after aortic valve replacement is rare. A 57-year-old man presented with an acute type A aortic dissection 1 year after aortic...
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