Combined Replacement of Aortic Valve and Ascending Aorta with Patent Foramen Ovale (PFO) Closure

Aortic valve disease in adults has many etiologies and requires careful operative planning when severe enough to require intervention. A common cause of aortic valve dysfunction in adults is a congenitally bicuspid valve that may also be associated with aortic aneurysm. Here, we describe the presentation and management of a middle-aged woman with symptomatic severe aortic stenosis due to a bicuspid aortic valve. She required an aortic valve replacement as well as replacement of an aneurysmal ascending aorta and closure of a patent foramen ovale (PFO).

Bicuspid aortic valve; bicuspid aortopathy; patent foramen ovale.

Bicuspid aortic valve (BAV) is a common congenital condition that is often asymptomatic and discovered only in adulthood when the aortic valve develops dysfunction and causes cardiac symptoms due to aortic valve stenosis (AS) or aortic valve regurgitation (AR). A normal aortic valve has 3 leaflets, but up to 1–2% of the population has a bicuspid aortic valve meaning there are only 2 leaflets. In addition to valve leaflet dysfunction, portions of the aorta including the aortic annulus, aortic root, and the proximal ascending aorta are also large in patients with bicuspid valve compared to patients with tricuspid valves. This phenomenon is known as bicuspid aortopathy, and the area of dilation can vary widely among patients with BAV. The treatment for BAV and its associated aortopathy is surgical repair or replacement of the aortic valve along with excision and replacement of the dilated portion of the aorta.

Patent foramen ovale (PFO) is an even more common congenital condition which involves incomplete closure of a foramen between the two atrial chambers of the heart. In 75% of children, this opening between the chambers closes by 1 year of age. When it fails to close, it can pose a risk of allowing blood clots to pass from the right side of the heart to the left side of the heart and cause stroke or other embolic illness. The treatment for PFO at the time of another cardiac operation is direct closure with suture. 

A 61-year-old female with history of bilateral knee replacements, hypertension, hyperlipidemia, and progressive severe bicuspid aortic valve stenosis. She progressively developed fatigue and decreased exercise tolerance, but denied chest pain, syncope, atrial fibrillation, and is a non-smoker. She is adopted and does not know her full family history.

On examination, this patient is well appearing. She has strong bilateral radial and pedal pulses and has no peripheral edema. On auscultation, she has 2+ upstrokes in bilateral carotid arteries without bruits, clear lung fields, and 4/6 crescendo-decrescendo systolic murmur heard best over the right upper parasternal border with no extra heart sounds and with regular rhythm. Her extremities are warm without abnormal skin changes. She is 5’ 1” weighing 79 kg with a BMI of 33 kg/m².

Although this patient had minimal notable exam findings, patients with longstanding aortic stenosis may present with a variety of findings including dysrhythmias, pulmonary congestion, chest pain, fatigue, or shortness of breath.

The mainstay of diagnostic imaging for aortic valve dysfunction prior to surgery is transthoracic echocardiographic (TTE) evaluation, cross-sectional aorta evaluations (CTA), and coronary artery evaluation (either angiography or CTA). 

This patient had normal ejection fraction of 65% on TTE with diastolic dysfunction, bicuspid aortic valve with restricted leaflet motion, and a calculated mean gradient of 63 mmHg, as well as a calculated aortic valve area of 0.8 cm². She also had a PFO on TTE with left to right shunting. On CTA, the patient had a normal diameter aortic root but an ascending aorta diameter of 4.5 cm and non-obstructive coronary artery disease.

The progression of BAV can be highly variable and depends on a variety of factors including whether the associated valve pathology is aortic regurgitation, aortic stenosis, and the presence of associated aortopathy. This patient had the most common pathology of BAV, which is aortic stenosis. AS occurs in up to 50% of adults with BAV and usually requires aortic valve replacement 5 years earlier compared with patients with tricuspid aortic valve stenosis. AS occurs due to leaflet fibrosis, calcification, and degeneration of the opening and closing function of the valve. Mechanical properties of the bicuspid valve including large cusp size (of the conjoined leaflet), presence of a raphe, and creasing of opening leaflets contribute to turbulence of blood flow and development of fibrosis and calcification. This process occurs more rapidly in BAV patients than in tricuspid aortic valve patients.

The aorta of patients with BAV are at risk for aneurysm formation and dissection due to earlier and more rapid growth rate of the aorta compared to patients with normal aortic valves. This is thought to be due to a decrease in the amount of fibrillin-1 as well as type I and II collagen in the aortic wall of BAV patients.

The standard treatment for this patient with severe bicuspid aortic stenosis and associated aortopathy is aortic valve replacement in order to preserve left ventricular function and increase her life expectancy. Her aorta is borderline dilated at 4.5 cm and when indexed to her body surface area is close to the guideline recommendations for ascending aorta replacement at the time of aortic valve replacement. In borderline cases such as this, intraoperative assessment of aorta tissue quality is often performed prior to making a final decision on replacement, but in this case we lean toward replacement given her young age and small body habitus for a 4.5-cm aorta. Finally, careful inspection for PFO under transesophageal echocardiogram (TEE) as well as direct inspection intraoperatively informed the decision to close her PFO at the time of the valve and aorta procedure.

The surgeon should consider several anatomic and patient demographic factors when deciding what extent of operation to perform. The first consideration is what prosthetic aortic valve substitute should be used. Broadly speaking, biologic prosthetic valves do not require anticoagulation to maintain function, but their biologic tissue leaflets will degenerate over the course of 5–15 years and will require a reintervention. Mechanical valves composed entirely of composite plastics and metal do not degrade but do require lifelong anticoagulation to keep from malfunctioning. Valve choice requires a patient-centered discussion with the surgeon and incorporates the patient’s values, age, and risk factors.

Another important consideration is the proximal extent of aortic replacement in bicuspid aortopathy. For patients who require valve replacement and have a dilated ascending aorta only above the sinotubular junction, a prosthetic valve and a supracoronary aortic Dacron graft are placed. For patients who require valve replacement and have both dilated aortic root and dilated aorta above the sinotubular junction, a Bentall procedure must be performed. A Bentall procedure involves creating a composite graft constructed of prosthetic valve and an ascending tube graft which replaces all aortic tissue from the level of the aortic annulus distally. This procedure requires excision of the right and left coronary artery ostium and reanastomosis of the coronary arteries to the new Dacron aortic graft. 

The distal aortic anastomosis can either be performed with a cross clamp in place or with the cross clamp removed under circulatory arrest. This decision is made based on the quality of aortic tissue and the extent of dilation at the base of the first aortic arch branch. If there appears to be a cuff of good quality, non-dilated aorta proximal to the first arch branch, it is reasonable to pursue a “clamp on” distal aortic anastomosis. 

A final point of consideration is use of PTFE or Teflon felt strip in a single (external to the aortic wall) or double (internal and external to the aortic wall) layer to support the proximal and distal anastomosis. This is done if the tissue quality is poor to minimize risk of bleeding. There is also some observational evidence that this reduces suture line disruption and pseudoaneurysm formation after surgery.

Bicuspid aortic valve (BAV) is one of the most common cardiac malformations first discovered by Leonardo Da Vinci in the 16th century. Today, it affects up to 2% of the general population and is commonly associated with valvular dysfunction in the form of aortic valve stenosis or regurgitation as well as associated with aortic dilation. Medical therapy in the form of aggressive blood pressure control through use of beta blockers is the guideline indicated for the valvular dysfunction; however, use of blood pressure or cholesterol lowering medications for associated aortopathy is unclear. The goal of medical therapy is to slow progression of degenerative valve disease, but ultimately all patients who live long enough will eventually develop an indication for surgical aortic valve replacement by meeting criteria for severe AS, chronic AR, or left ventricular dysfunction. There are also guideline criteria for replacement of a dilated aorta (root or ascending aorta) when the patient has BAV with or without valvular dysfunction. Generally speaking, the surgeon should consider replacing the aorta at smaller diameters for BAV compared to patients who have tricuspid valves because aneurysmal dilation occurs earlier and more rapidly in the BAV population. 

In this patient, replacement of the aortic valve and ascending aorta is initiated via a standard midline sternotomy, midline pericardial incision, and administration of systemic high dose heparin to facilitate blood circulation through the cardiopulmonary bypass (CPB) machine. Exposure of the heart and aorta is facilitated by suspending the pericardial edges to the chest wall. Next, arterial cannulation is via the ascending aorta as distally as safely possible in order to replace as much proximal aorta with a cross clamp on. Venous cannulation is performed via the superior vena cava (SVC) and the inferior vena cava (IVC) separately in order to facilitate entry into the right atrium at time of PFO closure. These cannulas are connected to the bypass machine and CPB is started. Next, the heart is stopped by placing a cross clamp as distally on the aorta as possible while still being proximal to the aortic cannula and then giving cold Del Nido cardioplegia antegrade through the aorta and via the coronary arteries. Once electromechanical arrest of the heart is achieved, the aorta is transected and aortic valve inspected. This revealed a Sievers type 1 left-right fused bicuspid valve that was heavily calcified. The calcium and leaflets are carefully and completely debrided and excised so as not to leave any particulates in the field. The annulus is sized, pledgeted sutures are placed circumferentially around the aortic annulus and then passed through a new bovine pericardial bioprosthetic valve. The valve is secured with hand-tied knots. This concludes the aortic valve replacement. 

Next, the ascending aorta is replaced by first excising all aorta from 2–3 mm above the sinotubular junction all the way to 1 cm proximal to the aortic cross clamp distally. A Dacron tube graft is used as the aorta substitute and is sewn proximally with permanent monofilament suture with incorporation of an external ring of PTFE felt for support. The distal anastomosis of the aortic graft is performed in a similar manner with the cross clamp in place and utilizing an external felt strip for support.

Lastly, the PFO is closed by first assuring that the right heart is isolated from venous blood return by snaring the SVC and IVC bypass drainage cannulas and then cutting open the right atrium. The PFO in the interatrial septum is identified and closed with a single suture, and the right atrium is closed. This concludes all repairs. The snares are removed, the cross clamp is removed, and warm, oxygenated blood returns to the coronary arteries and reanimates the heart. After placing epicardial pacing wires, chest tubes, and weaning completely off cardiopulmonary bypass with removal of cannulas, the valve and PFO are inspected via TEE and the chest is closed. 

Outcomes for aortic valve replacement and ascending aorta replacement in the setting of BAV are good with 30-day mortality of 0–2% and with late complications driven by the type of index operation. Late complications and need for reintervention fall into two categories: valve-related and aorta-related. Valve-related complications depend on if a biologic valve or mechanical valve was used. Biologic valves suffer from degenerative failure and mechanical valves are susceptible to bleeding diathesis or valve thrombosis because lifelong anticoagulation is required. Aorta-related complications depend on how much aorta was replaced at the time of the valve surgery. Patients who have undergone isolated valve replacement continue to be at risk for aneurysm formation and/or aortic dissection particularly if their aorta was >4 cm at the time of surgery. If a patient has had a portion of their aorta replaced, that repair is quite durable with most proximal or distal anastomotic pseudoaneurysms occurring early, but any residual dilation warrants cross-sectional imaging surveillance. 

• Cardiopulmonary Bypass machine.
• Arterial and venous bypass cannulas.
• Prosthetic aortic valve substitute.
• Synthetic tube graft aorta substitute.
  

Nothing to disclose.

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