Aortic Hemiarch and Valve Replacement for Severe Aortic Stenosis with Ascending Aortic Ectasia

Severe aortic valvular stenosis is a prevalent condition with potentially fatal consequences. Presenting symptoms may include dyspnea with angina/chest pains that can be significantly lifestyle limiting. Early detection and treatment are paramount to effective management, as untreated severe aortic stenosis has a five-year mortality of 50–70%. Treatment options range from the minimally invasive transcatheter approach to open heart surgery. Each strategy is tailored to the respective patient’s presentation, with considerations for cardiac anatomy, comorbidities, and patient frailty. When concomitant aortopathy is present, an open approach allows for definitive management of both conditions. 

Aortic ectasia is an abnormal dilation of the ascending aorta that, while itself is not as serious, can be a precursor to aortic aneurysm or dissection. In patients undergoing surgical aortic valve replacement, a composite replacement strategy can also address concomitant aortic ectasia by incorporating the new valve into an aortic graft segment as a single implant.

Valve surgery; ascending aorta and arch aortic surgery; aortic ectasia; aortic stenosis.

Severe aortic stenosis affects more than 3% of seniors in the United States and can lead to syncope and sudden cardiac death.¹ Prompt diagnosis and a thorough workup are essential in mitigating fatal outcomes. Echocardiography can be used to assess the severity of stenosis. Mild aortic stenosis is defined as a mean pressure gradient < 25 mmHg and an aortic valve area < 1.5 cm². Moderate aortic stenosis has a pressure gradient between 25–40 mmHg with an aortic valve area between 1 and 1.5 cm². Severe aortic is a pressure gradient greater than 40 mmHg with an aortic valve area less than 1 cm², or a peak flow velocity > 4 m/s.²

A surgical approach to repair provides an opportunity to also address concomitant pathologies. Aortic ectasia is a much less severe aortic pathology that describes ascending aortic dilation which has not yet surpassed a diameter of 4 cm to be classified as a thoracic aneurysm.³ This aortic dilation has a reported prevalence between 0.16%–0.34% and has noted to be increasing, likely due to improvements in diagnostic modalities.⁴ While criteria for surgical aortic valve replacement include the presence of symptoms, asymptomatic severe stenosis, or progressive left ventricular dilation, concomitant aortic disease may also be addressed. If the ascending aortic diameter is > 4.5 cm, surgical replacement is indicated in such cases. Otherwise, standalone ascending aortic replacement is indicated with an aortic diameter 5–5.5 cm.⁵ An aortic hemiarch and valve replacement can effectively address both of these pathologies with a single operation.

A 57-year-old male with a history of hypertension and hyperlipidemia presented to the emergency department after a syncopal episode. Workup demonstrated severe aortic stenosis with ascending aortic ectasia and aneurysm measuring up to 4.8 cm towards the aortic arch, with a normal aortic root size. A left heart catheterization was unremarkable for coronary disease and urgent surgical repair was recommended. 

The patient was resting comfortably without acute distress. Cardiac auscultation revealed S1, S2, and a harsh systolic murmur.

CTA imaging of the chest a bicuspid aortic valve with dense calcifications. The sinuses Valsalva level measured 28 x 30 mm with the sinotubular junction measuring 30 mm and the aortic annulus measuring 23 mm. There was fusiform aneurysmal dilation of the ascending thoracic aorta measuring 52 x 50 mm at the level of the right main pulmonary artery and 48 mm by the proximal aortic arch. The aneurysm tapered to a normal diameter with the descending thoracic aorta immediately distal to the arch measuring 25 mm. The heart was not enlarged. There was also multivessel coronary atherosclerosis.

Echocardiogram revealed a normal left ventricular ejection fraction of 55–60% and severe bicuspid aortic valvular stenosis with mild to moderate aortic regurgitation. The aortic valve peak velocity was measured at 5.94 m/s and valve area was 0.52cm². Mild left ventricular hypertrophy with impaired diastolic filling was also noted. A preoperative carotid duplex study was also performed to ensure adequate unilateral cerebral perfusion.

Severe aortic stenosis—even when asymptomatic—has been shown to have serious consequences without intervention, including sudden cardiac death. Other cardiac issues can also arise as a consequence of cardiac remodeling, including arrythmias, heart failure, and valvular regurgitation.⁶

Untreated aortic dilation can progressively lead to aortic dissection. For example, an ascending aortic diameter < 45 mm carries a low dissection risk, 45–50 mm carries a modest dissection risk, 50–54 mm carries a 1–3% annual dissection risk, and >55 mm is classified as a high risk, for up to 7–14% risk of aortic dissection per year.⁷

Non-operative management of thoracic aortic aneurysms have been studied retrospectively with 5-year mortality rates reported between 50–66%.⁸ Complications of unmanaged disease include aneurysmal growth, dissection, and rupture. 

Severe aortic valvular stenosis requires prompt management. While surgically placed aortic valves have consistently demonstrated the most durable repairs in literature, transcatheter valve replacement offers a minimally invasive option for more frail patients who may not tolerate an open-heart procedure, or patients over age 80.⁹ The most recent AHA recommendations a surgical mechanical aortic valve replacement for patients under 65, and transcatheter valve replacement for patients older than 80.¹⁰ Balloon valvuloplasty is another strategy that can be offered to patients in whom surgical repair is unfavorable due to comorbid conditions. Although its hemodynamic benefit has been reported to be as low as 6 months, it may serve as a bridging therapy to definitive management.¹¹ 

A surgical aortic valve replacement was performed as our patient had a younger age and longer life expectancy to justify a more invasive procedure to achieve a more durable outcome.¹² Per the AHA guidelines, the ascending aortic diameter > 4.5 cm warranted concomitant repair to avoid the risks of requiring repeat open heart surgery and mitigate the need for lifelong monitoring.⁷

If using a composite graft that includes the aortic valves and hemiarch, it is important to consider which patients may not be good candidates for this approach. This includes patients with aortas placed to the left of midline, or aortas which are porcelain or heavily calcified. Additionally, anomalous coronary origins can pose significant challenges with implanting the coronary anastomosis into the graft and should be thoroughly investigated prior to surgical planning.¹³ Additionally, the aortic cusp morphology should be examined for possible repairs in cases of aortic root dilation, for which a valve-sparing approach via the David or Yacoub procedures may be more suitable options.¹⁴

For valve selection, age is an important consideration. Patients aged 40–49 have been shown to an adjusted hazard ratio of 0.69 for all-cause mortality when comparing mechanical valve replacement to a bioprosthetic valve. This hazard ratio becomes 0.87 for ages 50–59; while patients aged 60 and older had no statistically significant difference in outcomes. Thus, patients under 60 have a demonstrated survival benefit with a mechanical valve compared to a bioprosthetic valve.¹⁵

Severe aortic stenosis is a serious condition that places additional strain on the heart by dramatically increasing the ventricular afterload. Untreated aortic stenosis can be lifestyle limiting, precipitating angina and syncope, and even sudden cardiac death. For middle-aged patients, a surgical valve replacement offers the most durable repair, while simultaneously allowing for correction of concomitant pathology.

An additional consideration is made for bicuspid aortic valve which has been well-demonstrated to correspond with proximal aortopathy—aortic root, ascending aorta, or both.¹⁶ A recent meta-analysis demonstrated the annual ascending aortic aneurysm growth rates to be more than double when comparing tricuspid aortic valve aneurysms (0.3 mm/year) to bicuspid aortic valve aneurysms (0.76 mm/year).¹⁷ This can be explained by observed differences in intrinsic medial extracellular-matric degeneration, when combined with altered valve-related hemodynamics, will cause abnormal flow rates and elevated shear stress of the aortic wall.¹⁶

The On-X is a mechanical aortic valve that has gained popularity since its inception one decade ago. Important traits of this valve include its carbon material, and a valve diameter-to-length ratio that best mimics native valve proportions. Compared to other valves, these features are responsible for increased valve strength, while minimizing thrombogenicity and hemolysis.¹² The initial INR recommendation for the On-X valve was around 2.5, however the more recent guidelines by the AHA recommend an INR range between 1.5 and 2.0 for patients with minimal risk factors.¹⁸

The Gelweave aortic graft is a woven polyester graft impregnated with a gelatin sealant to minimize blood leakage through the graft. The woven nature of this graft prevents fraying and allows for ease with surgical handling during suturing and implantation.¹² An additional benefit of using this graft for thoracic aortic cases is the versatility across both valve-sparing and valved-conduit procedures.19 As our patient had a normal aortic root size on their echocardiogram, we opted to maintain the native aortic sinus of Valsalva and selected the sinotubular junction as the proximal anastomotic site. With this method, the native coronary anatomy was maintained and no coronary anastomosis was required.

The endovascular alternative to aortic aneurysm repairs was first described in 1994 and the first commercially available thoracic aorta graft became available in 2005.²⁰ However ascending aortic repairs are incredibly challenging to manage endovascularly due to the complex anatomy involved. Some limiting factors are unmodifiable graft lengths which generally exceed the distance from the sinotubular junction and innominate artery. Other challenges include the curving anatomy of the ascending aorta with a lengthier superior arc than the inferior arc which make precise graft fixation technically arduous.²¹ Finally, the ascending aorta is unique in that it allows for accommodation of up to 50% of the left ventricular ejection fraction due to its tissue compliance during systole and allows for antegrade flow towards the arch branches and retrograde coronary flow during diastole—termed the “Windkessel effect”.²¹ Current endovascular grafts are mainly limited to polytetrafluoroethylene (PTFE) or Dacron materials which are fixed to stainless steel stents.²⁰ These materials have been shown to be less compliant than native aortic tissue by up to fourfold creating a compliance mismatch with long-term consequences for cardiovascular homeostasis, predisposing to left ventricular hypertrophy.^22,23 Further development in endovascular-compatible grafting materials are paramount to its future applicability as a viable repair option in comparison to open surgical repair.

Patients with ascending aortic aneurysms have commonly been found to have aortic valvular pathology, with the most common being a bicuspid aortic valve. A recent review published in 2023 compared patient outcomes from isolated aortic valve replacements to concomitant surgical ascending aortic aneurysm repair, demonstrating no significant difference in terms of mortality, survival rates, or long-term complication data.²⁴

In conclusion, patients with severe aortic valve stenosis and concomitant ascending aortic aneurysm may undergo a single operation to address both pathologies. This is well-tolerated and technically feasible with the current graft technologies available. Our patient did not have carotid stenosis allowing us to effectively maintain unilateral cerebral perfusion by placing an aortic clamp proximal to the left common carotid branch during the aortic repair. A comprehensive preoperative workup is instrumental to ensure appropriate patient selection for the corresponding grafting strategy.

Implants:

• Aortic graft: Hemashield Gelweave aortic graft
• Aortic valve: ON-X mechanical valve
• Left atrial appendage clip: 35 AtriClip

Open Heart Surgery Tools:

• Sternal retractor
• Aortic clamps
• Cardiopulmonary bypass cannulae and setup
• Vessel loops and tourniquets
• Teflon plegets
• Atrial and venous wires
• Mediastinal and pleural chest tubes
• Sternal cables and plates
• Prevena vacuum-assisted wound closure device

The authors have no disclosures.

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.