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Monday, September 26, 2011
Advances Fall 2011
For years, the standard surgical treatment for aortic regurgitation has been to remove the faulty natural valve and replace it with a biological or mechanical one. There are significant drawbacks to this approach, however. Biological valves wear out over time, resulting in a high risk for reoperation in patients younger than 65. Mechanical valves are durable, but they promote blood clot formation, necessitating a lifetime of anticoagulation therapy.
The alternative to replacing a malfunctioning valve is repair. Mitral valves have been repaired routinely for two decades, and, in recent years, the surgical technique for repairing aortic valves has been refined. Aortic valve repair, rather than replacement, is now a viable option for many patients with aortic regurgitation.
A related condition that is increasingly corrected with valve-preserving surgery is dilatation of the aortic root. Because the aortic valve is suspended within the aortic root, root enlargement has traditionally been treated by replacing both the damaged portion of the aorta and the aortic valve. Today, however, valve- sparing root reconstruction is becoming more common at select centers around the country, including the Massachusetts General Hospital Heart Center. In this procedure, the affected part of the aorta is removed and replaced by a synthetic graft, yet the natural valve is preserved.
Surgeons in the Thoracic Aortic Center at Massachusetts General Hospital are pioneers in developing and refining these procedures. The cumulative experience of the team of Heart Center surgeons led by Thoralf M. Sundt III, MD, chief of cardiac surgery and co-director at the Mass General Heart Center, and by co-director Thomas MacGillivray, MD, is among the largest in the country.
Indications for Surgery
Any physical abnormality that keeps the aortic valve from closing completely can lead to regurgitation. In cases of aortic valve prolapse, one of the valve leaflets is elongated, preventing the tips of the leaflets from closing properly to form a tight seal. In cases of prior infection, a hole in the leaflet causes leakage.
A slightly leaky valve unassociated with aortic enlargement may never cause severe complications. However, if the valve leaks too much and for too long, the heart may begin to fail. Therefore, valve repair or replacement is usually recommended whenever there is significant regurgitation along with ventricular enlargement.
Another cause of leaky aortic valves is enlargement of the aortic root or ascending aorta, which can pull the valve leaflets apart. If an enlargement in this section of the aorta causes a dissection, or tear, the results can be lethal. The mortality rate is 25 percent among patients who reach the hospital, and many others never make it to the emergency room. Surgical reconstruction of the aortic root can prevent such catastrophic events, so identifying appropriate patients for the surgery is a high priority.
When to recommend surgery is determined by weighing the risk for aortic dissection against the risks for the surgery itself. A key indicator of the risk for aortic dissection is the diameter of the aorta. In a review of studies examining the natural history of ascending aortic aneurysms, Dr. Sundt and his coauthor found that aneurysms exceeding 6 cm in maximum diameter are associated with a very high risk for complications. To provide a margin of safety, they concluded that surgery is indicated at an aortic diameter of 5.5 cm and above.
When the diameter falls between 5.0 cm and 5.5 cm, surgery is still sometimes considered, especially for patients ages 50 and younger, in whom the operative risk is low and the number of years they will otherwise be at risk for dissection is high. For individuals at particular risk, such as those with Marfan syndrome, bicuspid aortic valve, or familial thoracic aortic aneurysm syndromes, surgery may be recommended at diameters as low as 4.5 cm.
When surgery is indicated, the main advantage of preserving the natural aortic valve rather than replacing it with a mechanical substitute is that anticoagulant therapy is not required afterward. Anticoagulant medication carries a risk for serious bleeding and stroke, and it interacts with many other drugs and certain foods. Monthly blood tests to monitor the effectiveness of the medication are also needed. Valve-saving procedures let patients avoid these pitfalls.
Aortic Valve Repair
Surgical repair of the aortic valve alone can be performed in experienced hands in as little as 30 minutes of cross-clamp time. During this period, the surgeon first inspects the valve to determine why it is leaking. If a leaflet is elongated, a small tuck is taken in the free edge to shorten it to the correct length. If there is a hole in a leaflet, it is patched.
Research shows that even bicuspid aortic valves, a congenital condition, can be repaired successfully, although they will continue to have only two leaflets, not the standard three. In one study, Dr. Sundt and his colleagues followed 108 patients who had surgical repair of a bicuspid aortic valve. Five- and 10-year survival rates after the repair were 96 and 87 percent, respectively. A separate analysis matched these patients with a group that had a biological valve replacement. Results showed the chance of staying free of reoperation and the 10-year survival rate did not differ between the two groups.
Valve-Sparing Root Reconstruction
Valve-sparing root reconstruction is a more complex procedure, requiring about two hours of cross-clamp time. After detaching the coronary arteries from the aortic root, the surgeon excises the affected wall of the aorta, leaving the leaflets behind. A tubular synthetic graft is sewn to the base of the heart, and the natural leaflets are then suspended inside the graft and sutured into place. Finally, the coronary arteries are attached to the graft, and the graft is sewn distally to the natural aorta.
In a prospective international study, Dr. Sundt and others assessed 151 patients with Marfan syndrome who underwent root reconstruction. The natural aortic valve was preserved in 105 of the patients and replaced in the rest. Although the valve-sparing surgery was more complex, the rate of postoperative complications was similarly low for the two procedures. Marfan syndrome patients who have root reconstruction are typically young, so they benefit from a procedure that eliminates the need for lifetime anticoagulation therapy.
Postoperative Recovery and Risks
Immediately after surgery, a breathing tube remains in place for about six hours. Most patients move to a step-down unit the day following surgery and leave the hospital three to five days later. However, it generally takes four to six weeks for patients to feel substantially better and return to work. Many patients find that participation in a structured rehabilitation program helps them through the postoperative recovery period.
During and soon after surgery, complications can occur, including endocarditis (infection of the valve), bleeding, stroke, and renal failure, although these are uncommon. The operative risk is low in younger patients when the procedure is performed in a high-volume center under elective circumstances. In Dr. Sundt’s study of Marfan syndrome patients, for example, no in-hospital or 30-day deaths occurred. As with any surgery, however, the risk increases in older patients and those with comorbidities, such as pre-existing kidney disease.
The primary long-term risk associated with these procedures is the possibility that the repair may deteriorate over time, at which point the patient may require another surgery. For aortic valve repair, reoperation rates up to 10 percent over 10 years have been reported. Nevertheless, many patients may feel that the risk for reoperation in the future is a reasonable trade-off for avoiding anticoagulation presently and potentially for decades to come.
Ashikhmina E, Sundt TM III, Dearani JA, Connolly HM, Li Z, Schaff HV. (2010). Repair of the bicuspid aortic valve: A viable alternative to replacement with a bioprosthesis. J Thorac Cardiov Sur, 139(6): 1395-401.
Davies JE, Sundt TM. (2007). Surgery insight: The dilated ascending aorta—indications for surgical intervention. Nat Clin Pract Cardiovasc Med, 4(6): 330-39.
Sareyyupoglu B, Suri RM, Schaff HV, Dearani JA, Daly RC, Orszulak TA, Sundt TM. (2009). Survival and reoperation risk following bicuspid aortic valve-sparing root replacement. J Heart Valve Dis, 18(1): 1-8.
Volguina IV, Miller DC, LeMaire SA, Palmero LC, Wang XL, Connolly HM, Sundt TM III, Bavaria JE, Dietz HC, Milewicz DM, Coselli JS, Aortic Valve Operative Outcomes in Marfan Patients study group. (2009). Valve-sparing and valve-replacing techniques for aortic root replacement in patients with Marfan syndrome: Analysis of early outcome. J Thorac Cardiov Sur, 137(5): 1124-32.
Massachusetts General Hospital Heart Center
The Massachusetts General Hospital Heart Center is a multidisciplinary program that integrates the experts and services of the divisions of Cardiology, Cardiac Surgery, Cardiac Anesthesia, Cardiac Imaging, and Cardiac Nursing to provide state-of-the-art care for patients with all types of cardiac disorders. Continuing its legacy as a pioneer in cardiac research, the Heart Center also conducts bench-to-bedside research aimed at improving the prevention, diagnosis, and treatment of heart disease worldwide.
For more information about the Massachusetts General Hospital Heart Center or to refer a patient, please call 866-MGH-8910 (866-644-8910) or visit the Heart Center website
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