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A Rare Cause of Severe Aortic Insufficiency Without Stenosis: Certainly Not One of the Usual Suspects
A Rare Cause of Severe Aortic Insufficiency Without Stenosis: Certainly Not One of the Usual Suspects Kishan Dwarakanath, MD,* Derek J. De Vry, MD,* M. Ansar Maqsood, MD,* Roger A. Fons, MD,* Saqib Masroor, MD,† and Paul S. Pagel, MD, PhD*
A
64-YEAR-OLD, 188-cm, 102-kg man was admitted to the authors’ institution for evaluation of shortness of breath and diaphoresis. The patient denied a history of fever, chills, malaise, chest pain, exercise intolerance, orthopnea, paroxysmal nocturnal dyspnea, and lower-extremity swelling. He described a past medical history of essential hypertension (for which he received metoprolol, hydralazine, and furosemide), hyperlipidemia (simvastatin), type II diabetes mellitus (insulin), well-controlled hyperthyroidism (methimazole), and gout
Fig 2. A midesophageal aortic valve long-axis color Doppler TEE image showing severe aortic insufficiency. (Color version of figure is available online.)
Fig 1. A modified midesophageal aortic valve long-axis TEE image showing (A) an accessory structure attached to the left or noncoronary aortic valve leaflet and (B) a hemispherical opening in the distal posterior sinus of valsalva opening into the aortic lumen (see Video 1).
From the *Anesthesia Service and †Cardiothoracic Surgery Service, Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, WI. Address reprint requests to Paul S. Pagel, MD, PhD, Clement J. Zablocki Veterans Affairs Medical Center, Anesthesia Service, 5000 W National Avenue, Milwaukee, WI 53295. E-mail: [email protected] © 2011 Elsevier Inc. All rights reserved. 1053-0770/2501-0035$36.00/0 doi:10.1053/j.jvca.2009.09.002 Key words: congenital heart disease, quadricuspid aortic valve, ascending aortic aneurysm, aortic insufficiency
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(allopurinol). He acknowledged that he had voluntarily stopped taking furosemide a few days before admission. The patient also reported a history of a stable proximal ascending thoracic aortic aneurysm for which he had been followed with serial computed tomography scans. The physical examination revealed a grade II to III of VI blowing diastolic murmur in the left 2nd intercostal space radiating caudad along the left sternal border. Rales were heard in the bilateral lung bases, and “water hammer” radial arterial pulses were noted. Laboratory analysis indicated the presence of stable chronic renal insufficiency (serum creatinine concentration of 1.5 mg/dL) but was otherwise unremarkable. Leukocytosis was absent. A chest radiograph was notable for mild pulmonary vascular congestion. A thoracic computed tomography scan with angiographic contrast showed a mildly calcified, aneurysmal ascending aorta with a maximum anterior-posterior diameter of 4.6 cm (not shown) that was unchanged compared with a previous study. Transesophageal echocardiography (TEE) was performed as part of the evaluation and revealed severe aortic regurgitation without stenosis (Figs 1 and 2 and Videos 1 and 2 [supplementary videos are available online]). What are the structures labeled “A” and “B” in Figure 1? What is the cause of the aortic insufficiency?
Journal of Cardiothoracic and Vascular Anesthesia, Vol 25, No 1 (February), 2011: pp 196-198
QUADRICUSPID AORTIC VALVE
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DIAGNOSIS: HURWITZ-ROBERTS TYPE B QUADRICUSPID AORTIC VALVE WITH ANOMALOUS POSTERIOR DISPLACEMENT OF THE LEFT CORONARY OSTIUM AND SEVERE AORTIC INSUFFICIENCY
A modified midesophageal aortic valve long-axis TEE image showed an accessory structure attached to the left or noncoronary aortic valve leaflet and a 5-mm hemispherical opening in the distal posterior sinus of Valsalva adjacent to the sinotubular junction that was continuous with the aortic lumen (Fig 1 and Video 1). The motion of the accessory structure followed the movement of this posterior aortic leaflet and was not consistent with the usual appearance or mechanics of a vegetation. Color Doppler blood flow mapping revealed a centrally directed jet of severe aortic insufficiency that nearly filled the distal left ventricular outflow tract (Fig 2 and Video 2). Diastolic blood flow was also observed entering the opening in the distal posterior sinus of Valsalva (Fig 2 and Video 2). A midesophageal aortic valve short-axis image showed a quadricuspid aortic valve with 3 large leaflets (corresponding to the usual left, right, and noncoronary cusps) and a smaller posterior accessory leaflet (Fig 3 and Video 3). All 4 leaflets were modestly thickened but opened normally without evidence of stenosis. Abnormal central coaptation of the 4 leaflets was observed concomitant with severe central aortic regurgitation (Figs 3 and 4 and Videos 3 and 4). Direct inspection of the aortic valve during cardiopulmonary bypass confirmed these TEE findings (Fig 5). There was fibrous thickening observed in all 4 cusps. The origin of the left coronary ostium was abnormally positioned in a posterior location immediately proximal to the sinotubular junction. This anomalous left coronary ostium corresponded to the opening observed in the distal posterior sinus of valsalva in the TEE aortic valve long-axis view (Fig 2 and Video 2). The native aortic valve was resected and replaced with a 25-mm bioprosthesis (St Jude Medical, St Paul, MN). The aneurysmal segment of the proximal ascending thoracic aorta was also resected and replaced with a 28-mm Hemashield graft (Boston Scientific, Wayne, NJ). The native coronary ostia were preserved. The patient separated from cardiopulmonary bypass with inotropic
Fig 3. A midesophageal aortic valve short-axis TEE image obtained during early diastole showing the quadricuspid aortic valve with a posterior accessory cusp and abnormal central coaptation of the valve leaflets.
Fig 4. A midesophageal aortic valve short-axis color Doppler TEE image obtained during early diastole showing a large central jet of aortic insufficiency. (Color version of figure is available online.)
support. A repeat TEE examination revealed normal function of the aortic prosthesis. The patient was transported to the surgical intensive care unit in stable condition after surgery, but excessive mediastinal bleeding necessitated re-exploration 3 hours later. After satisfactory surgical hemostasis was obtained, the patient was returned to intensive care. He was subsequently weaned from inotropic support and extubated on the morning after surgery. The remainder of the patient’s hospital course was uneventful, and he was discharged on the 5th postoperative day. A quadricuspid aortic valve is a very rare congenital heart abnormality. Unlike postinflammatory disease, aortic root dilatation, incomplete closure of a congenitally bicuspid aortic valve, or infective endocarditis, a quadricuspid aortic valve is also an exceedingly unusual cause of pure aortic insufficiency.1 Feldman et al2 reported only 6 quadricuspid aortic valves in a retrospective series of 13,805 transthoracic echocardiographic examinations. The remarkably low incidence (0.043%) described in this large
Fig 5. An intraoperative photograph of the aortic valve taken from the surgeon’s perspective showing the posterior accessory aortic cusp; thickening of the left, right, and noncoronary cusps; and redundant leaflet tissue in the left coronary cusp. (Color version of figure is available online.)
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review was similar to the findings of 2 autopsy series (incidences of 0.008% and 0.033%).3,4 Olson et al1 reported a 1% incidence of quadricuspid aortic valves in 225 patients undergoing surgery for aortic insufficiency without stenosis. Similarly, Yotsumoto et al5 described their management of 9 patients with quadricuspid aortic valves in another review of 616 consecutive aortic valve procedures (incidence of 1.46%). In contrast to the findings of these relatively small single-center reports, other studies of aortic valve surgical pathology6 and congenital valvular disease in European Homograft Bank donor hearts7 encompassing more than 4,500 examinations failed to identify a single case of quadricuspid aortic valve. These latter data emphasize the relative rarity of this congenital disorder. Interestingly, quadricuspid pulmonic valves were shown to be 5 times more common than quadricuspid aortic valves.8 The cause of this difference remains unclear but may be related to cyanotic heart defects involving the pulmonary outflow tract (eg, tetralogy of Fallot and truncus arteriosus). Hurwitz and Roberts4 devised a classification system that identified 7 variations of quadricuspid aortic valve based on the relative size of the leaflets (denoted types A through G). Similar to the quadricuspid aortic valve observed in the current patient, 41% of quadricuspid aortic valves described in the largest review of reported cases published to date were composed of 3 leaflets of equal size and 1 smaller leaflet (defined as type B).9 Two other common forms consisted of 4 similar cusps (type A, 32% of cases) and 2 larger plus 2 smaller cusps (type C, 15%), whereas other less frequent combinations of cusp sizes accounted for the remaining cases.9 As clearly shown in the current patient, the specific diagnosis and classification of quadricuspid aortic valve are most often established by using 2-dimensional or, more recently, 3-dimensional transthoracic
echocardiography or TEE because the presence and relative size of the 4-valve leaflets may be readily distinguished.10-17 Nevertheless, echocardiographic classification of quadricuspid aortic valve disease may not always correlate with surgical anatomy because foreshortening of the short-axis views of the valve may distort the relative cusp size.10 In the largest review of published cases of quadricuspid aortic valve to date, Timperly et al9 observed that 10 of 114 reported cases (8.8%) were associated with an anomalously placed coronary ostium. The left coronary ostium of the current patient with a quadricuspid aortic valve was abnormally located in a posterior-superior position within the left coronary sinus of valsalva. Recognition of such an abnormality may be crucial from a surgical perspective because the sewing ring of a prosthetic aortic valve may inadvertently obstruct the affected coronary ostium and prevent coronary blood flow under these circumstances.18 As observed in the current patient, TEE was previously shown to be useful in the demonstration of coronary ostial displacement in a patient with a quadricuspid aortic valve.19 Severe aortic insufficiency (without stenosis) requiring surgical intervention is usually observed late in the natural history of quadricuspid aortic valve disease and has been most frequently reported in the 6th decade of life when patients present with progressive dyspnea.9 Aortic regurgitation may occur as a consequence of cusp asymmetry, abnormal leaflet motion, differential stress distribution, and resultant fibrous thickening that combine to produce leaflet malcoaptation.20 As observed in the current patient, severe aortic insufficiency occurs most commonly in Hurwitz-Roberts type B compared with other forms of quadricuspid aortic valve.2
REFERENCES 1. Olson LJ, Subramanian R, Edwards WD: Surgical pathology of pure aortic insufficiency: A study of 225 cases. Mayo Clin Proc 59:835-841, 1984 2. Feldman BJ, Khandheria BK, Warnes CA, et al: Incidence, description and functional assessment of isolated quadricuspid aortic valves. Am J Cardiol 65:937-938, 1990 3. Simonds JP: Congenital malformations of the aortic and pulmonic valves. Am J Med Sci 166:584-595, 1923 4. Hurwitz LE, Roberts WC: Quadricuspid semilunar valve. Am J Cardiol 31:623-626, 1973 5. Yotsumoto G, Iguro Y, Kinjo T, et al: Congenital quadricuspid aortic valve: report of nine surgical cases. Ann Thorac Cardiovasc Surg 9:134-137, 2003 6. Turri M, Thiene G, Bortolotti U, et al: Surgical pathology of aortic valve disease. A study based on 602 specimens. Eur J Cardiothorac Surg 4:556-560, 1990 7. Jashari R, Van Hoeck B, Goffin Y, et al: The incidence of congenital bicuspid or bileaflet and quadricuspid or quadrileaflet arterial valves in 3,861 donor hearts in the European Homograft Bank. J Heart Valve Dis 18:337-344, 2009 8. Davia JE, Fenoglio JJ, DeCastro CM, et al: Quadricuspid semilunar valves. Chest 72:186-189, 1977 9. Timperley J, Milner R, Marshall AJ, et al: Quadricuspid aortic valves. Clin Cardiol 25:548-552, 2002 10. Barbosa MM, Motta MS: Quadricuspid aortic valve and aortic regurgitation diagnosed by Doppler echocardiography: Report of two cases and review of the literature. J Am Soc Echocardiogr 4:69-74, 1991
11. Bonde P, Sachithanadan A, McClements B, et al: Quadricuspid aortic valve: A rare cause of aortic insufficiency. J Heart Valve Dis 11:506-508, 2002 12. Formica F, Sangalli F, Ferro O, et al: A rare cause of severe aortic regurgitation: Quadricuspid aortic valve. Interact Cardiovasc Thorac Surg 3:672-674, 2004 13. Sangalli F, Formica F, Avalli L, et al: Quadricuspid aortic valve as a cause of severe aortic regurgitation. Ital Heart J 6:157-159, 2005 14. Armen TA, Vandse R, Bickle K, et al: Three-dimensional echocardiographic evaluation of an incidental quadricuspid aortic valve. Eur J Echocardiogr 9:318-320, 2008 15. Godefroid O, Colles P, Vercauteren S, et al: Quadricuspid aortic valves: A rare etiology of aortic regurgitation. Eur J Echocardiogr 7:168-170, 2006 16. Gulyasy B, Lopez-Candales A, Reis SE, et al: Quadricuspid aortic valve: An unusual echocardiographic finding and a review of the literature. Int J Cardiol 132:e68-e71, 2009 17. Holt NF, Sivarajan M, Mandapati D, et al: Quadricuspid aortic valve with aortic insufficiency: Case report and review of the literature. J Card Surg 22:235-237, 2007 18. Kurosawa H, Wagenaar S, Becker AE: Sudden death in a youth. A case of quadricuspid aortic valve with isolation of the origin of the left coronary artery. Br Heart J 46:211-215, 1981 19. Kajinami K, Takekoshi N, Mabuchi H: Images in cardiology. Non-invasive detection of quadricuspid aortic valve. Heart 78:87, 1997 20. Sievers HH, Regensburger D, Bernhard A: Quadricuspid aortic valve with significant insufficiency. Thorac Cardiovasc Surg 30:44-45, 1982
A
64-YEAR-OLD, 188-cm, 102-kg man was admitted to the authors’ institution for evaluation of shortness of breath and diaphoresis. The patient denied a history of fever, chills, malaise, chest pain, exercise intolerance, orthopnea, paroxysmal nocturnal dyspnea, and lower-extremity swelling. He described a past medical history of essential hypertension (for which he received metoprolol, hydralazine, and furosemide), hyperlipidemia (simvastatin), type II diabetes mellitus (insulin), well-controlled hyperthyroidism (methimazole), and gout
Fig 2. A midesophageal aortic valve long-axis color Doppler TEE image showing severe aortic insufficiency. (Color version of figure is available online.)
Fig 1. A modified midesophageal aortic valve long-axis TEE image showing (A) an accessory structure attached to the left or noncoronary aortic valve leaflet and (B) a hemispherical opening in the distal posterior sinus of valsalva opening into the aortic lumen (see Video 1).
From the *Anesthesia Service and †Cardiothoracic Surgery Service, Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, WI. Address reprint requests to Paul S. Pagel, MD, PhD, Clement J. Zablocki Veterans Affairs Medical Center, Anesthesia Service, 5000 W National Avenue, Milwaukee, WI 53295. E-mail: [email protected] © 2011 Elsevier Inc. All rights reserved. 1053-0770/2501-0035$36.00/0 doi:10.1053/j.jvca.2009.09.002 Key words: congenital heart disease, quadricuspid aortic valve, ascending aortic aneurysm, aortic insufficiency
196
(allopurinol). He acknowledged that he had voluntarily stopped taking furosemide a few days before admission. The patient also reported a history of a stable proximal ascending thoracic aortic aneurysm for which he had been followed with serial computed tomography scans. The physical examination revealed a grade II to III of VI blowing diastolic murmur in the left 2nd intercostal space radiating caudad along the left sternal border. Rales were heard in the bilateral lung bases, and “water hammer” radial arterial pulses were noted. Laboratory analysis indicated the presence of stable chronic renal insufficiency (serum creatinine concentration of 1.5 mg/dL) but was otherwise unremarkable. Leukocytosis was absent. A chest radiograph was notable for mild pulmonary vascular congestion. A thoracic computed tomography scan with angiographic contrast showed a mildly calcified, aneurysmal ascending aorta with a maximum anterior-posterior diameter of 4.6 cm (not shown) that was unchanged compared with a previous study. Transesophageal echocardiography (TEE) was performed as part of the evaluation and revealed severe aortic regurgitation without stenosis (Figs 1 and 2 and Videos 1 and 2 [supplementary videos are available online]). What are the structures labeled “A” and “B” in Figure 1? What is the cause of the aortic insufficiency?
Journal of Cardiothoracic and Vascular Anesthesia, Vol 25, No 1 (February), 2011: pp 196-198
QUADRICUSPID AORTIC VALVE
197
DIAGNOSIS: HURWITZ-ROBERTS TYPE B QUADRICUSPID AORTIC VALVE WITH ANOMALOUS POSTERIOR DISPLACEMENT OF THE LEFT CORONARY OSTIUM AND SEVERE AORTIC INSUFFICIENCY
A modified midesophageal aortic valve long-axis TEE image showed an accessory structure attached to the left or noncoronary aortic valve leaflet and a 5-mm hemispherical opening in the distal posterior sinus of Valsalva adjacent to the sinotubular junction that was continuous with the aortic lumen (Fig 1 and Video 1). The motion of the accessory structure followed the movement of this posterior aortic leaflet and was not consistent with the usual appearance or mechanics of a vegetation. Color Doppler blood flow mapping revealed a centrally directed jet of severe aortic insufficiency that nearly filled the distal left ventricular outflow tract (Fig 2 and Video 2). Diastolic blood flow was also observed entering the opening in the distal posterior sinus of Valsalva (Fig 2 and Video 2). A midesophageal aortic valve short-axis image showed a quadricuspid aortic valve with 3 large leaflets (corresponding to the usual left, right, and noncoronary cusps) and a smaller posterior accessory leaflet (Fig 3 and Video 3). All 4 leaflets were modestly thickened but opened normally without evidence of stenosis. Abnormal central coaptation of the 4 leaflets was observed concomitant with severe central aortic regurgitation (Figs 3 and 4 and Videos 3 and 4). Direct inspection of the aortic valve during cardiopulmonary bypass confirmed these TEE findings (Fig 5). There was fibrous thickening observed in all 4 cusps. The origin of the left coronary ostium was abnormally positioned in a posterior location immediately proximal to the sinotubular junction. This anomalous left coronary ostium corresponded to the opening observed in the distal posterior sinus of valsalva in the TEE aortic valve long-axis view (Fig 2 and Video 2). The native aortic valve was resected and replaced with a 25-mm bioprosthesis (St Jude Medical, St Paul, MN). The aneurysmal segment of the proximal ascending thoracic aorta was also resected and replaced with a 28-mm Hemashield graft (Boston Scientific, Wayne, NJ). The native coronary ostia were preserved. The patient separated from cardiopulmonary bypass with inotropic
Fig 3. A midesophageal aortic valve short-axis TEE image obtained during early diastole showing the quadricuspid aortic valve with a posterior accessory cusp and abnormal central coaptation of the valve leaflets.
Fig 4. A midesophageal aortic valve short-axis color Doppler TEE image obtained during early diastole showing a large central jet of aortic insufficiency. (Color version of figure is available online.)
support. A repeat TEE examination revealed normal function of the aortic prosthesis. The patient was transported to the surgical intensive care unit in stable condition after surgery, but excessive mediastinal bleeding necessitated re-exploration 3 hours later. After satisfactory surgical hemostasis was obtained, the patient was returned to intensive care. He was subsequently weaned from inotropic support and extubated on the morning after surgery. The remainder of the patient’s hospital course was uneventful, and he was discharged on the 5th postoperative day. A quadricuspid aortic valve is a very rare congenital heart abnormality. Unlike postinflammatory disease, aortic root dilatation, incomplete closure of a congenitally bicuspid aortic valve, or infective endocarditis, a quadricuspid aortic valve is also an exceedingly unusual cause of pure aortic insufficiency.1 Feldman et al2 reported only 6 quadricuspid aortic valves in a retrospective series of 13,805 transthoracic echocardiographic examinations. The remarkably low incidence (0.043%) described in this large
Fig 5. An intraoperative photograph of the aortic valve taken from the surgeon’s perspective showing the posterior accessory aortic cusp; thickening of the left, right, and noncoronary cusps; and redundant leaflet tissue in the left coronary cusp. (Color version of figure is available online.)
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review was similar to the findings of 2 autopsy series (incidences of 0.008% and 0.033%).3,4 Olson et al1 reported a 1% incidence of quadricuspid aortic valves in 225 patients undergoing surgery for aortic insufficiency without stenosis. Similarly, Yotsumoto et al5 described their management of 9 patients with quadricuspid aortic valves in another review of 616 consecutive aortic valve procedures (incidence of 1.46%). In contrast to the findings of these relatively small single-center reports, other studies of aortic valve surgical pathology6 and congenital valvular disease in European Homograft Bank donor hearts7 encompassing more than 4,500 examinations failed to identify a single case of quadricuspid aortic valve. These latter data emphasize the relative rarity of this congenital disorder. Interestingly, quadricuspid pulmonic valves were shown to be 5 times more common than quadricuspid aortic valves.8 The cause of this difference remains unclear but may be related to cyanotic heart defects involving the pulmonary outflow tract (eg, tetralogy of Fallot and truncus arteriosus). Hurwitz and Roberts4 devised a classification system that identified 7 variations of quadricuspid aortic valve based on the relative size of the leaflets (denoted types A through G). Similar to the quadricuspid aortic valve observed in the current patient, 41% of quadricuspid aortic valves described in the largest review of reported cases published to date were composed of 3 leaflets of equal size and 1 smaller leaflet (defined as type B).9 Two other common forms consisted of 4 similar cusps (type A, 32% of cases) and 2 larger plus 2 smaller cusps (type C, 15%), whereas other less frequent combinations of cusp sizes accounted for the remaining cases.9 As clearly shown in the current patient, the specific diagnosis and classification of quadricuspid aortic valve are most often established by using 2-dimensional or, more recently, 3-dimensional transthoracic
echocardiography or TEE because the presence and relative size of the 4-valve leaflets may be readily distinguished.10-17 Nevertheless, echocardiographic classification of quadricuspid aortic valve disease may not always correlate with surgical anatomy because foreshortening of the short-axis views of the valve may distort the relative cusp size.10 In the largest review of published cases of quadricuspid aortic valve to date, Timperly et al9 observed that 10 of 114 reported cases (8.8%) were associated with an anomalously placed coronary ostium. The left coronary ostium of the current patient with a quadricuspid aortic valve was abnormally located in a posterior-superior position within the left coronary sinus of valsalva. Recognition of such an abnormality may be crucial from a surgical perspective because the sewing ring of a prosthetic aortic valve may inadvertently obstruct the affected coronary ostium and prevent coronary blood flow under these circumstances.18 As observed in the current patient, TEE was previously shown to be useful in the demonstration of coronary ostial displacement in a patient with a quadricuspid aortic valve.19 Severe aortic insufficiency (without stenosis) requiring surgical intervention is usually observed late in the natural history of quadricuspid aortic valve disease and has been most frequently reported in the 6th decade of life when patients present with progressive dyspnea.9 Aortic regurgitation may occur as a consequence of cusp asymmetry, abnormal leaflet motion, differential stress distribution, and resultant fibrous thickening that combine to produce leaflet malcoaptation.20 As observed in the current patient, severe aortic insufficiency occurs most commonly in Hurwitz-Roberts type B compared with other forms of quadricuspid aortic valve.2
REFERENCES 1. Olson LJ, Subramanian R, Edwards WD: Surgical pathology of pure aortic insufficiency: A study of 225 cases. Mayo Clin Proc 59:835-841, 1984 2. Feldman BJ, Khandheria BK, Warnes CA, et al: Incidence, description and functional assessment of isolated quadricuspid aortic valves. Am J Cardiol 65:937-938, 1990 3. Simonds JP: Congenital malformations of the aortic and pulmonic valves. Am J Med Sci 166:584-595, 1923 4. Hurwitz LE, Roberts WC: Quadricuspid semilunar valve. Am J Cardiol 31:623-626, 1973 5. Yotsumoto G, Iguro Y, Kinjo T, et al: Congenital quadricuspid aortic valve: report of nine surgical cases. Ann Thorac Cardiovasc Surg 9:134-137, 2003 6. Turri M, Thiene G, Bortolotti U, et al: Surgical pathology of aortic valve disease. A study based on 602 specimens. Eur J Cardiothorac Surg 4:556-560, 1990 7. Jashari R, Van Hoeck B, Goffin Y, et al: The incidence of congenital bicuspid or bileaflet and quadricuspid or quadrileaflet arterial valves in 3,861 donor hearts in the European Homograft Bank. J Heart Valve Dis 18:337-344, 2009 8. Davia JE, Fenoglio JJ, DeCastro CM, et al: Quadricuspid semilunar valves. Chest 72:186-189, 1977 9. Timperley J, Milner R, Marshall AJ, et al: Quadricuspid aortic valves. Clin Cardiol 25:548-552, 2002 10. Barbosa MM, Motta MS: Quadricuspid aortic valve and aortic regurgitation diagnosed by Doppler echocardiography: Report of two cases and review of the literature. J Am Soc Echocardiogr 4:69-74, 1991
11. Bonde P, Sachithanadan A, McClements B, et al: Quadricuspid aortic valve: A rare cause of aortic insufficiency. J Heart Valve Dis 11:506-508, 2002 12. Formica F, Sangalli F, Ferro O, et al: A rare cause of severe aortic regurgitation: Quadricuspid aortic valve. Interact Cardiovasc Thorac Surg 3:672-674, 2004 13. Sangalli F, Formica F, Avalli L, et al: Quadricuspid aortic valve as a cause of severe aortic regurgitation. Ital Heart J 6:157-159, 2005 14. Armen TA, Vandse R, Bickle K, et al: Three-dimensional echocardiographic evaluation of an incidental quadricuspid aortic valve. Eur J Echocardiogr 9:318-320, 2008 15. Godefroid O, Colles P, Vercauteren S, et al: Quadricuspid aortic valves: A rare etiology of aortic regurgitation. Eur J Echocardiogr 7:168-170, 2006 16. Gulyasy B, Lopez-Candales A, Reis SE, et al: Quadricuspid aortic valve: An unusual echocardiographic finding and a review of the literature. Int J Cardiol 132:e68-e71, 2009 17. Holt NF, Sivarajan M, Mandapati D, et al: Quadricuspid aortic valve with aortic insufficiency: Case report and review of the literature. J Card Surg 22:235-237, 2007 18. Kurosawa H, Wagenaar S, Becker AE: Sudden death in a youth. A case of quadricuspid aortic valve with isolation of the origin of the left coronary artery. Br Heart J 46:211-215, 1981 19. Kajinami K, Takekoshi N, Mabuchi H: Images in cardiology. Non-invasive detection of quadricuspid aortic valve. Heart 78:87, 1997 20. Sievers HH, Regensburger D, Bernhard A: Quadricuspid aortic valve with significant insufficiency. Thorac Cardiovasc Surg 30:44-45, 1982