Acute Aortic Regurgitation Secondary to Disk Embolization of a Björk-Shiley Prosthetic Aortic Valve

Having passed the 30th anniversary of the first implantation of a Björk-Shiley convexo-concave tilting mechanical valve, recognition of the life-threatening complication of strut fracture is not widespread. The authors report the case of a 48-year-old man with acute-onset chest pain and dyspnea found to have strut fracture and disk embolization of a 26-year-old Björk-Shiley prosthetic aortic valve. The value of echocardiography in the diagnosis of this condition is discussed.

Case Presentation

A 48-year-old Caucasian man was transferred to our hospital after presenting to an outside institution with acute-onset dyspnea, chest pain, and orthopnea. The patient’s surgical history was significant for three previous sternotomies, including a ventricular septal defect repair at 2 years of age and a redo aortic valve replacement with a 27-mm convexo-concave 60° Björk-Shiley valve at 22 years of age. The patient was previously offered a prophylactic valve replacement. He was followed for a nonischemic cardiomyopathy and had undergone the placement of a dual-chamber implantable cardiac defibrillator after a previous episode of ventricular tachycardia.

At the outside institution, he was persistently dyspneic and referred for urgent left-heart catheterization. Coronary angiography revealed no significant epicardial coronary artery disease. On transfer to our institution, the patient was immediately intubated for progressive tachypnea and hypoxia. Initial vital signs revealed a temperature of 37.2°C, blood pressure of 114/42 mm Hg, respiratory rate of 24 breaths/min, and heart rate of 102 beats/min. On examination, jugular venous pressure was 14 mm Hg. Cardiac examination revealed tachycardia without an appreciable murmur. Prosthetic clicks were notably absent. Scattered bibasilar crackles were noted. The abdomen was benign, and no peripheral edema was noted.

Electrocardiography revealed sinus tachycardia with ventricular pacing, and a portable chest x-ray revealed severe pulmonary edema. Pressor and inotropic support was initiated. Emergent two-dimensional echocardiography revealed severe left ventricular dysfunction, normal motion of the aortic annular ring, and no elevation of left ventricular outflow gradients ( Figure 1 ). Significant aortic regurgitation was noted with color Doppler echocardiography. Transesophageal echocardiography was performed to further evaluate the prosthetic aortic valve. The prosthetic leaflets could not be visualized ( Video 1 ). Severe, wide-open aortic insufficiency was confirmed from both the midesophageal ( Video 2 ) and deep transgastric ( Video 3 ) views on transesophageal echocardiography. Continuous-wave Doppler through the aortic valve revealed an extremely short pressure half-time consistent with rapid equilibration of the left ventricular end-diastolic and diastolic blood pressure ( Figure 2 ). An atrial septal defect was noted with prominent left-to-right shunting consistent with the marked elevation in left ventricular end-diastolic pressure ( Video 4 ). Finally, the aorta was markedly pulsatile, consistent with the acute, severe aortic regurgitation ( Video 5 ).

The patient underwent urgent cardiac surgery. Intraoperatively, the tilting disk was absent, and the metal strut of the Björk-Shiley valve was resting in the noncoronary sinus near the left main ostium ( Figure 3 ). The patient underwent implantation of a #27-mm Carpentier-Edwards Magna pericardial valve (Edwards Lifesciences Inc., Irvine, CA) and closure of the atrial septal defect. The patient unfortunately passed away because of shock-refractory ventricular fibrillation in the postoperative period.

Discussion

The Björk-Shiley convexo-concave prosthetic heart valve was first introduced in 1969. In an effort to reduce the valve’s risk for thrombosis and increase the effective orifice area, modifications were made, including the convexo-concave shape and disk opening angle. Strut fractures of both the 60° opening angle valve used in the United States beginning in 1978 and the 70° valve used in Europe were subsequently reported. With the recognition of the fracture of the outlet struts with disk embolization and severe regurgitation, both the 60° and 70° valves were eventually withdrawn from the market. Nonetheless, >86,000 valves were implanted between 1978 and 1986, with >600 confirmed episodes of outlet strut fracture. Although the number of strut fractures has dramatically decreased in the past decade, this issue remains clinically relevant in long-term survivors from the original series. Unfortunately, recognition of this life-threatening problem has markedly decreased given the rarity of events in the past several years.

Outlet valve strut fracture results in escape of the tilting disk with embolization, subsequent severe valvular regurgitation, and frequently catastrophic death. Despite these events, reports of survival after disk embolization have been noted. Similar to our patient, the presentation is typically acute pulmonary edema, cardiogenic shock, and stigmata of embolization from the tilting disk. Absence of prosthetic valve clicks is noted, and fluoroscopy or echocardiography can be used to establish the diagnosis.

Although efforts via cine radiographic imaging have yielded some benefit in predicting patients at risk for strut fracture with Björk-Shiley convexo-concave mitral valves, a sole diagnostic test to predict patients at risk has not been established. Given the risk for prophylactic replacement, multivariate decision guidelines have been formulated to assist physicians in determining whether prophylactic replacement is warranted. Increased risk for strut fracture has been noted with mitral valves (vs aortic), larger valve sizes, 70° convexo-concave models (vs 60°), and specific welding dates, welder groups, and batch orders. The major patient factor for strut fracture appears to be age, with higher risks of strut fracture in younger patients. Overall, our patient seemed to be at lower risk.

Our patient presented with acute aortic insufficiency due to strut fracture of a 26-year-old Björk-Shiley aortic valve. Despite recently passing the 30th anniversary of the first implantation of a Björk-Shiley convexo-concave valve, there remain patients at undefined risk for strut fracture and consideration for prophylactic replacement. Additionally, clinicians need to remain cognizant of this life-threatening complication related to convexo-concave Björk-Shiley valves. This present case illustrates the use of transesophageal echocardiography in immediate recognition of this surgical emergency.