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Cardiac pseudoaneurysm caused by mitral ring calcification
281
Cardiovasc Pathol Vol. 3, No. 4 October-December 1994:281-285
Cardiac Pseudoaneurysm Caused by Mitral Ring Calcification Hideko Kiguchi, M D , * Toshiharu Ishii, M D , * Shigeru Masuda, M D , * Yukio Ishikawa, M D , * Noriko Asuwa, M D , * Tetsuya Osada, MD, t Tatsuhiko Kudo, MD,* and Takashi Uchiyama, MD*
Departments of *Pathology, *Surgery, and *Internal Medicine, Hachioji Medical Center, Tokyo Medical College, Hachioji-City, Tokyo, Japan
++ A case of left ventricular pseudoaneurysm caused by mitral ring calcification (MRC) in a 71-year-old woman is reported. MRC was initially detected by two-dimensional echocardiography. Two months later, rupture of the posterior wall and pseudoaneurysm formation were diagnosed. Mitral valve replacement and reconstructive surgery of the myocardial wall were performed. The patient died 46 days after the operation. At autopsy, there was no histopathological evidence of myocardial infarction, infective endocarditis, or other conditions affecting the cardiac endomyocardium. Pseudoaneurysm apparently resulted from left atrial and ventricular tears caused by MRC.
Mitral ring calcification (MRC) is a common finding in the aged. It is more pronounced in females than in males (1-3). MRC usually has no clinical significance, although occasionally heart murmur, valvular incompetence, or His bundle block is detected (4-9). We recently encountered a case of left ventricular pseudoaneurysm that resulted from intimal tears of the left atrium and ventricle in the setting of moderate MRC. To the best of our knowledge, this is the first documented case of pseudoaneurysm caused by MRC.
Case Report A 71-year-old woman was admitted to an outside hospital on December 15, 1990, with a history of persistent fever as high as 38°C for several days without any preceding complaints. She defervesced after 10 days of intravenous antibiotic therapy for a presumed bacterial infection of unknown origin. Blood culture was negative, and by antibiotic therapy she had no fever hereafter. On January 4, 1991, a holosystolic apical murmur of grade 3/6 was auscultated, and twodimensional echocardiography demonstrated bright echoes at the posterior mitral ring. Vegetations of infective endocarditis were ruled out by echo findings and physical examination. These findings were attributed to MRC. She had no fever, and
Manuscript received June 22, 1993; accepted December 27, 1993. Address for reprints: Hideko Kiguchi, MD, Department of Pathology, Hachioji Medical Center, Tokyo Medical College, 1163 Tatemachi, HachiojiCity, Tokyo, 193, Japan; telephone: 0426-65-5611, fax: 0426-66-0551. © 1994 by Elsevier Science Inc.
blood culture was negative continuously. For two weeks, however, antibiotics were prophylactically given in case infective endocarditis was present. During the term of antibiotic therapy she had no fever and was generally stable; afterward, she was discharged. On March 12, 1991, she became acutely dyspneic and was readmitted. Echocardiography demonstrated an echo-free space behind the left ventricular posterior wall. She was transferred to the Department of Cardiovascular Surgery at this hospital. On physical examination, the brachial systolic blood pressure was 60 mm Hg. Her respiratory rate was 22/rain. Fine, moist rales were audible throughout the lung fields. Microbiological examinations of the patienfs blood demonstrated no pathogenic organisms. A holosystolic murmur of grade 5/6 was heard at the apex. Electrocardiogram revealed normal sinus rhythm at 100/min with left atrial overload. Chest roentgenography showed marked cardiomegaly and an unusual bulge in the left cardiac contour. Two-dimensional echocardiography demonstrated a large echo-free space that lay on the dorsal side between the posterior wall of the left atrium and ventricle (Figs. IA and 1B). A high-velocity jet directed toward the echo-free space indicated rupture of the left ventricle posterior wall beneath the mitral ring, as noted by color doppler echocardiography. Another jet directed toward the posterior wall of the left atrium suggested mild mitral regurgitation. The other valves functioned normally. The pericardial space was free of fluid. After transfer to the intensive care unit, she developed severe heart failure. On March 20, 1991, she underwent surgery to prevent more severe mitral regurgitation. The mitral 1054-8807/94/$7.00
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Cardiovasc Pathol Vol. 3, No. 4 October-December 1994:281-285
Figure 1. (A) Two-dimensional echocardiography showing pseudoaneurysm behind the posterior wall of the left atrium and left ventricle. (B) A schema of Figure 1A. The space indicated by an asterisk is the lumen of the pseudoaneurysm (LA: left atrium; LV: left ventricle; Ao: aorta).
valve was replaced with an artificial valve (27 mm, CarboMedics, Austin, TX). At the time of the operation, the mitral valve was slightly thickened, but neither deformity nor mass vegetation was found. No rheumatic change was evident in the valve. There was no active inflammatory change on the cardiac endomyocardium. Microscopic evaluation of the mitral valve demonstrated moderate calcification at the basal part of the posterior leaflet (Fig. 2). Mild lymphocytic infiltration of the posterior mitral leaflet was noted in the compact connective tissue layer on the left ventricular side. The anterior mitral leaflet was normal. Round and oval tears were found
on the surfaces of the posterior wall above and beneath the mitral ring at the posterior leaflet. One tear of 0.5 x 2.0 cm was noted on the ventricular side, and another tear of 1.0 cm in diameter was found on the atrial side. Both of these tears communicated directly with the subepicardial space. The wall of the pseudoaneurysm was composed of fibrous tissue and thrombus. The left ventricular tear was sutured concurrently with replacement by the artificial valve. The tear in the left atrium was closed by interrupted sutures supported with a Teflon pledget. After surgery, inflow jet directed toward the pseudoaneurysm disappeared on color doppler echocardiog-
Cardiovasc Pathol Vol. 3, No. 4 October-December 1994:281-285
Figure 2. Calcified mass in the basal part of the resected posterior mitral leaflet (hematoxylin-eosin stain, x90).
raphy. Postoperative cardiac function improved, but dyspnea remained. She eventually died of severe heart failure 46 days after surgery.
Autopsy Findings A small amount of serous fluid (10 mL) was found in the pericardial sac. The heart and its contents weighed 780 g. An external bulge over the anterior surface of the left atrium and upper left ventricle was a pseudoaneurysm filled with massive thrombus measuring 8 x 6 x 6 cm (Fig. 3). The two tears that had been sutured at the time of the operation apparently provided access to the left atrium and left ventricle. The pseudoaneurysm extended into the adjacent subepicardial space. The outer surface of the pseudoaneurysm slightly adhered to the opposite pericardial sac with fibrinous material, but it was easily separated manually. Histopathologically, the wall of the pseudoaneurysm was encapsulated by connective tissue component of the epicardium throughout its circumference and contained hemosiderin deposits. No myocardial elements were included. The endo-
KIGUCHI ET AL. CARDIAC PSEUDOANEURYSM CAUSED BY MRC
283
Figure 3. The autopsied heart. The subepicardial space over the left atrium and left ventricle is markedly enlarged by the pseudoaneurysm. Arrows indicate the sutured tears.
cardium underlying the two sutured sites just above the mitral valve prosthesis was thickened with granulation tissue. The mitral valve prosthesis was intact. However, moderate calcification and mild lymphocytic infiltration were observed along the basal part of the posterior mitral ring for 3.0 cm in length (Fig. 4). Neither neutrophils nor hemosiderin-laden macrophages were present. Neither bacterial vegetation nor adhesions were seen on the mitral ring or subvalvular region of the left ventricle. The right and left ventricles were hypertrophic, but no particular change was observed in the other portions of the heart. Congestion was notable in the liver, kidney, and spleen, all of which were free from evidence of sepsis.
Discussion Pseudoaneurysm of the heart is an unusual condition. It results from ventricular wall rupture caused by acute myocardial infarction (10), trauma (11), infective endocarditis (12-14), and postoperative complication of mitral valve replacement (15,16). The sites of rupture are usually the aortic
284
KIGUCHI ET AL. CARDIAC PSEUI~ANEURYSM CAUSED BY MRC
Cardiovasc Pathol Vol. 3, No. 4 October-December 1994:281-285
Figure 4. Calcification is noted in the mitral ring with fibrosis and slight lymphocytic infiltration (hematoxylin-eosin stain, ×20).
annulus (13), mitral-aortic intravalvular fibrosa (12,17), or along the left ventricular wall (10,11,14). In the present case, pseudoaneurysm was present on the posterior side of the left atrium and ventricle. The main tear communicating with the ventricular chamber was found in the intima of the posterior mitral ring, which showed moderate calcification. MRC is a fairly common finding in adults at autopsy (1). Pomerance reported an incidence of 8.5 % among individuals over the age of 50 years (2). It is encountered at least two or three times more often in women than in men. MRC usually has no clinical significance (3). Extensive calcification of the mitral ring, however, may result in mitral valve insufficiency (4). Mitral systolic murmurs have been frequently described in the setting of MRC (5,6). Other complications are heart block (7), left ventricular outflow obstruction with severe calcification (8), and cerebral or retinal ischemia (9). In a report by Mambo et al. on five patients with calcified posterior mitral ring associated with infective endocarditis, infiltration of the involved leaflet caused perforation (18). Rupture of the ring or the myocardium frequently leads to fatal cardiac tamponade. Some reports have noted that the mitral valve is likely to be destroyed in the setting of infective endocarditis superimposed on MRC. Those cases, however, are usually culture-positive. Cardiac rupture occurs at the acme of infective endocarditis in almost all cases (12-14,18). The clinical diagnosis of infective endocarditis could not be established in our patient. Histopathologic examinations at autopsy similarly failed to provide any evidence of infection. The presence of MRC thus seems to have been a critical contributor to cardiac rupture in this patient. The presence of a very large fibrous capsule, as in the present case, suggests that microhemorrhage had persisted long
enough to have gradually induced formation of a giant pseudoaneurysm. Etiologic factors producing a similar clinical picture include calcification and pseudoaneurysm formation following mitral valve replacement (15,16). MRC following mitral valve replacement has been attributed to a response to increased blood flow, secondary to the loss of mobility and contractility of the ring caused by placement of an artificial valve. Calcification is assumed to make the ring fragile, and subsequent microhemorrhage from the sutured site of the artificial valve could cause pseudoaneurysm formation. On the other hand, calcification is, in general, a sequela of connective tissue degeneration within the cardiovascular system. Fulkerton et al. listed advanced age, female sex, increased mitral stress, and abnormal annular tissue as predisposing factors of MRC (19). Furthermore, the posterior leaflet is probably more subject than the anterior leaflet to increased left ventricular outflow force caused by degenerative changes of the mitral ring (20). When left atrial dilatation and left ventricular hypertrophy occur, mitral stress causes tension within the posterior mitral leaflet and its chordae (21). It has been suggested that the outflow force finally tears the mitral ring, which is vulnerable owing to underlying calcification. A phenomenon analogous to this mechanism may have occurred in our patient. MRC, an aging process frequently noted on routine echocardiography and lateral chest x-ray, sometimes complicates cardiovascular disease. In our patient, MRC was detected as bright echoes of the posterior mitral ring by echocardiography at the beginning of her illness. Until the pseudoaneurysm was found to echocardiography, she had not suffered from myocardial infarction, infective endocarditis, or other well-described causes of cardiac rupture. We con-
Cardiovasc Pathol Vol. 3, No. 4 October-December1994:281-285
c l u d e that M R C c a u s e d the p s e u d o a n e u r y s m over the left a t r i u m a n d ventricle. P s e u d o a n e u r y s m should b e a d d e d to the list o f k n o w n , but rare, c o m p l i c a t i o n s o f M R C .
KIGUCHI ET AL. CARDIAC PSEUDOANEURYSMCAUSEDBY MRC
12.
References 1. Ishii T, Sternby NH. Pathology of centenarians: 1. The cardiovascular system and lungs. J Am Geriatr Soc 1978;26:108-115. 2. Pomerance A. Pathologicaland clinical study of calcificationof the mitral valve ring. J Clin Pathol 1970;23:354-361. 3. Lewandowski BJ, Winsberg F. Incidence of aortic cusp and mitral annulus calcification as determined by echocardiography: significance and interrelationship. Am J Roentgenol 1982;138:829-832. 4. Pounder DJ. Calcification of the mitral annulus and its complications. Am J Forensic Med Pathol 1982;3:109-113. 5. Simon MA, Liu SF. Calcification of the mitral valve annulus and its relation to functionalvalvular disturbance. Am Heart J 1954;48:497-505. 6. Korn D, DeSanctis RW, Sell S. Massive calcification of the mitral annulus: a clinicopathological study of fourteen cases. N Engl J Med 1962;267:900-909. 7. Kriwisky M, Goldstein J, Gotsman MS. Accessory atrioventricular pathway, supra-, and infrahisian conduction impaired due to mitral annulus calcification. Clin Cardiol 1987;10:818-820. 8. Iga K, Hori K. Left ventricular outflow obstruction caused by mitral ring calcification. Am Heart J 1990;119:418--419. 9. DeBono DP, Warlow CP. Mitral-annulus calcification and cerebral or retinal ischemia. Lancet 1979;ii:383-385. 10. Buehler DL, Stinson EB, Oyer PE, Shumway NE. Surgical treatment of aneurysms of the inferior left ventricular wall. J Thorac Cardiovasc Surg 1979;78:74-78. 11. Waldhausen JA, Petry EL, Kurlander GJ. Successful repair of subval-
13. 14.
15.
16.
285
vular annular aneurysm of the left ventricle. N Engl J Med 1966;275: 984-987. Bansal RC, Graham BM, Jutzy KR, Shakudo M, Shaw PM. Left vantricular outflow tract to left atrial communication secondary to rupture of mitral-aortic intervalvular fibrosa in infective endocarditis: diagnosis by transesophageal echocardiography and color flow imaging. J Am Coil Cardiol 1990; 15:499-504. Bhagwat AR, Patil PM, Loya YS, Sharman S. Subaortic aneurysm in infective endocarditis. Am Heart J 1991;122:588-589. Kessler KM, Kieval J, Saksena S, Sanderson TL, Myerburg RJ. Echocardiographic features of posterior left ventricular wall pseudoaneurysm due to Escherichia coli endocarditis. Am Heart J 1982;103:139-142. Kupari M, Verkkala K, Maamies T, Hiirtel G. Value of combined cross sectional and doppler echocardiography in the detection of left ventricular pseudoaneurysm after mitral valve replacement. Br Heart J 1987; 58:52-56. Verkkala K, Maamies T, Kupari M, Mattila T, Ala-Kulju K. Pseudoaneurysm of the left ventricle following mitral valve replacement. J Cardiovasc Surg 1990;31:242-246.
17. Bansal RC, Molony PM, Marsa ILl, Jacobson JG. Echocardiographic features of a mycotic aneurysm of the left ventricular outflowtract caused by perforation of mitral-aortic intervalvular fibrosa. Circulation 1983; 67:930-934. 18. Mambo NC, Silver MD, Brunsdon DFV. Bacterial endocarditis of the mitral valve associated with annular calcification. Can Med Assoc J 1978; 119:323-326. 19. Fulkerson PK, Beaver BM, Auseon JC, Graber HL. Calcification of the mitral annulus. Am J Med 1979;66:967-977. 20. Roberts WC, Perloff JK. Mitral valvular disease. Ann Intern Med 1972;77:939-975. 21. Salazar AE, Edwards JE. Friction lesions of ventricular endocardium. Arch Pathol 1970;90:364-376.
Cardiovasc Pathol Vol. 3, No. 4 October-December 1994:281-285
Cardiac Pseudoaneurysm Caused by Mitral Ring Calcification Hideko Kiguchi, M D , * Toshiharu Ishii, M D , * Shigeru Masuda, M D , * Yukio Ishikawa, M D , * Noriko Asuwa, M D , * Tetsuya Osada, MD, t Tatsuhiko Kudo, MD,* and Takashi Uchiyama, MD*
Departments of *Pathology, *Surgery, and *Internal Medicine, Hachioji Medical Center, Tokyo Medical College, Hachioji-City, Tokyo, Japan
++ A case of left ventricular pseudoaneurysm caused by mitral ring calcification (MRC) in a 71-year-old woman is reported. MRC was initially detected by two-dimensional echocardiography. Two months later, rupture of the posterior wall and pseudoaneurysm formation were diagnosed. Mitral valve replacement and reconstructive surgery of the myocardial wall were performed. The patient died 46 days after the operation. At autopsy, there was no histopathological evidence of myocardial infarction, infective endocarditis, or other conditions affecting the cardiac endomyocardium. Pseudoaneurysm apparently resulted from left atrial and ventricular tears caused by MRC.
Mitral ring calcification (MRC) is a common finding in the aged. It is more pronounced in females than in males (1-3). MRC usually has no clinical significance, although occasionally heart murmur, valvular incompetence, or His bundle block is detected (4-9). We recently encountered a case of left ventricular pseudoaneurysm that resulted from intimal tears of the left atrium and ventricle in the setting of moderate MRC. To the best of our knowledge, this is the first documented case of pseudoaneurysm caused by MRC.
Case Report A 71-year-old woman was admitted to an outside hospital on December 15, 1990, with a history of persistent fever as high as 38°C for several days without any preceding complaints. She defervesced after 10 days of intravenous antibiotic therapy for a presumed bacterial infection of unknown origin. Blood culture was negative, and by antibiotic therapy she had no fever hereafter. On January 4, 1991, a holosystolic apical murmur of grade 3/6 was auscultated, and twodimensional echocardiography demonstrated bright echoes at the posterior mitral ring. Vegetations of infective endocarditis were ruled out by echo findings and physical examination. These findings were attributed to MRC. She had no fever, and
Manuscript received June 22, 1993; accepted December 27, 1993. Address for reprints: Hideko Kiguchi, MD, Department of Pathology, Hachioji Medical Center, Tokyo Medical College, 1163 Tatemachi, HachiojiCity, Tokyo, 193, Japan; telephone: 0426-65-5611, fax: 0426-66-0551. © 1994 by Elsevier Science Inc.
blood culture was negative continuously. For two weeks, however, antibiotics were prophylactically given in case infective endocarditis was present. During the term of antibiotic therapy she had no fever and was generally stable; afterward, she was discharged. On March 12, 1991, she became acutely dyspneic and was readmitted. Echocardiography demonstrated an echo-free space behind the left ventricular posterior wall. She was transferred to the Department of Cardiovascular Surgery at this hospital. On physical examination, the brachial systolic blood pressure was 60 mm Hg. Her respiratory rate was 22/rain. Fine, moist rales were audible throughout the lung fields. Microbiological examinations of the patienfs blood demonstrated no pathogenic organisms. A holosystolic murmur of grade 5/6 was heard at the apex. Electrocardiogram revealed normal sinus rhythm at 100/min with left atrial overload. Chest roentgenography showed marked cardiomegaly and an unusual bulge in the left cardiac contour. Two-dimensional echocardiography demonstrated a large echo-free space that lay on the dorsal side between the posterior wall of the left atrium and ventricle (Figs. IA and 1B). A high-velocity jet directed toward the echo-free space indicated rupture of the left ventricle posterior wall beneath the mitral ring, as noted by color doppler echocardiography. Another jet directed toward the posterior wall of the left atrium suggested mild mitral regurgitation. The other valves functioned normally. The pericardial space was free of fluid. After transfer to the intensive care unit, she developed severe heart failure. On March 20, 1991, she underwent surgery to prevent more severe mitral regurgitation. The mitral 1054-8807/94/$7.00
282
KIGUCHI ET AL. CARDIAC PSEUDOANEURYSM CAUSED BY MRC
Cardiovasc Pathol Vol. 3, No. 4 October-December 1994:281-285
Figure 1. (A) Two-dimensional echocardiography showing pseudoaneurysm behind the posterior wall of the left atrium and left ventricle. (B) A schema of Figure 1A. The space indicated by an asterisk is the lumen of the pseudoaneurysm (LA: left atrium; LV: left ventricle; Ao: aorta).
valve was replaced with an artificial valve (27 mm, CarboMedics, Austin, TX). At the time of the operation, the mitral valve was slightly thickened, but neither deformity nor mass vegetation was found. No rheumatic change was evident in the valve. There was no active inflammatory change on the cardiac endomyocardium. Microscopic evaluation of the mitral valve demonstrated moderate calcification at the basal part of the posterior leaflet (Fig. 2). Mild lymphocytic infiltration of the posterior mitral leaflet was noted in the compact connective tissue layer on the left ventricular side. The anterior mitral leaflet was normal. Round and oval tears were found
on the surfaces of the posterior wall above and beneath the mitral ring at the posterior leaflet. One tear of 0.5 x 2.0 cm was noted on the ventricular side, and another tear of 1.0 cm in diameter was found on the atrial side. Both of these tears communicated directly with the subepicardial space. The wall of the pseudoaneurysm was composed of fibrous tissue and thrombus. The left ventricular tear was sutured concurrently with replacement by the artificial valve. The tear in the left atrium was closed by interrupted sutures supported with a Teflon pledget. After surgery, inflow jet directed toward the pseudoaneurysm disappeared on color doppler echocardiog-
Cardiovasc Pathol Vol. 3, No. 4 October-December 1994:281-285
Figure 2. Calcified mass in the basal part of the resected posterior mitral leaflet (hematoxylin-eosin stain, x90).
raphy. Postoperative cardiac function improved, but dyspnea remained. She eventually died of severe heart failure 46 days after surgery.
Autopsy Findings A small amount of serous fluid (10 mL) was found in the pericardial sac. The heart and its contents weighed 780 g. An external bulge over the anterior surface of the left atrium and upper left ventricle was a pseudoaneurysm filled with massive thrombus measuring 8 x 6 x 6 cm (Fig. 3). The two tears that had been sutured at the time of the operation apparently provided access to the left atrium and left ventricle. The pseudoaneurysm extended into the adjacent subepicardial space. The outer surface of the pseudoaneurysm slightly adhered to the opposite pericardial sac with fibrinous material, but it was easily separated manually. Histopathologically, the wall of the pseudoaneurysm was encapsulated by connective tissue component of the epicardium throughout its circumference and contained hemosiderin deposits. No myocardial elements were included. The endo-
KIGUCHI ET AL. CARDIAC PSEUDOANEURYSM CAUSED BY MRC
283
Figure 3. The autopsied heart. The subepicardial space over the left atrium and left ventricle is markedly enlarged by the pseudoaneurysm. Arrows indicate the sutured tears.
cardium underlying the two sutured sites just above the mitral valve prosthesis was thickened with granulation tissue. The mitral valve prosthesis was intact. However, moderate calcification and mild lymphocytic infiltration were observed along the basal part of the posterior mitral ring for 3.0 cm in length (Fig. 4). Neither neutrophils nor hemosiderin-laden macrophages were present. Neither bacterial vegetation nor adhesions were seen on the mitral ring or subvalvular region of the left ventricle. The right and left ventricles were hypertrophic, but no particular change was observed in the other portions of the heart. Congestion was notable in the liver, kidney, and spleen, all of which were free from evidence of sepsis.
Discussion Pseudoaneurysm of the heart is an unusual condition. It results from ventricular wall rupture caused by acute myocardial infarction (10), trauma (11), infective endocarditis (12-14), and postoperative complication of mitral valve replacement (15,16). The sites of rupture are usually the aortic
284
KIGUCHI ET AL. CARDIAC PSEUI~ANEURYSM CAUSED BY MRC
Cardiovasc Pathol Vol. 3, No. 4 October-December 1994:281-285
Figure 4. Calcification is noted in the mitral ring with fibrosis and slight lymphocytic infiltration (hematoxylin-eosin stain, ×20).
annulus (13), mitral-aortic intravalvular fibrosa (12,17), or along the left ventricular wall (10,11,14). In the present case, pseudoaneurysm was present on the posterior side of the left atrium and ventricle. The main tear communicating with the ventricular chamber was found in the intima of the posterior mitral ring, which showed moderate calcification. MRC is a fairly common finding in adults at autopsy (1). Pomerance reported an incidence of 8.5 % among individuals over the age of 50 years (2). It is encountered at least two or three times more often in women than in men. MRC usually has no clinical significance (3). Extensive calcification of the mitral ring, however, may result in mitral valve insufficiency (4). Mitral systolic murmurs have been frequently described in the setting of MRC (5,6). Other complications are heart block (7), left ventricular outflow obstruction with severe calcification (8), and cerebral or retinal ischemia (9). In a report by Mambo et al. on five patients with calcified posterior mitral ring associated with infective endocarditis, infiltration of the involved leaflet caused perforation (18). Rupture of the ring or the myocardium frequently leads to fatal cardiac tamponade. Some reports have noted that the mitral valve is likely to be destroyed in the setting of infective endocarditis superimposed on MRC. Those cases, however, are usually culture-positive. Cardiac rupture occurs at the acme of infective endocarditis in almost all cases (12-14,18). The clinical diagnosis of infective endocarditis could not be established in our patient. Histopathologic examinations at autopsy similarly failed to provide any evidence of infection. The presence of MRC thus seems to have been a critical contributor to cardiac rupture in this patient. The presence of a very large fibrous capsule, as in the present case, suggests that microhemorrhage had persisted long
enough to have gradually induced formation of a giant pseudoaneurysm. Etiologic factors producing a similar clinical picture include calcification and pseudoaneurysm formation following mitral valve replacement (15,16). MRC following mitral valve replacement has been attributed to a response to increased blood flow, secondary to the loss of mobility and contractility of the ring caused by placement of an artificial valve. Calcification is assumed to make the ring fragile, and subsequent microhemorrhage from the sutured site of the artificial valve could cause pseudoaneurysm formation. On the other hand, calcification is, in general, a sequela of connective tissue degeneration within the cardiovascular system. Fulkerton et al. listed advanced age, female sex, increased mitral stress, and abnormal annular tissue as predisposing factors of MRC (19). Furthermore, the posterior leaflet is probably more subject than the anterior leaflet to increased left ventricular outflow force caused by degenerative changes of the mitral ring (20). When left atrial dilatation and left ventricular hypertrophy occur, mitral stress causes tension within the posterior mitral leaflet and its chordae (21). It has been suggested that the outflow force finally tears the mitral ring, which is vulnerable owing to underlying calcification. A phenomenon analogous to this mechanism may have occurred in our patient. MRC, an aging process frequently noted on routine echocardiography and lateral chest x-ray, sometimes complicates cardiovascular disease. In our patient, MRC was detected as bright echoes of the posterior mitral ring by echocardiography at the beginning of her illness. Until the pseudoaneurysm was found to echocardiography, she had not suffered from myocardial infarction, infective endocarditis, or other well-described causes of cardiac rupture. We con-
Cardiovasc Pathol Vol. 3, No. 4 October-December1994:281-285
c l u d e that M R C c a u s e d the p s e u d o a n e u r y s m over the left a t r i u m a n d ventricle. P s e u d o a n e u r y s m should b e a d d e d to the list o f k n o w n , but rare, c o m p l i c a t i o n s o f M R C .
KIGUCHI ET AL. CARDIAC PSEUDOANEURYSMCAUSEDBY MRC
12.
References 1. Ishii T, Sternby NH. Pathology of centenarians: 1. The cardiovascular system and lungs. J Am Geriatr Soc 1978;26:108-115. 2. Pomerance A. Pathologicaland clinical study of calcificationof the mitral valve ring. J Clin Pathol 1970;23:354-361. 3. Lewandowski BJ, Winsberg F. Incidence of aortic cusp and mitral annulus calcification as determined by echocardiography: significance and interrelationship. Am J Roentgenol 1982;138:829-832. 4. Pounder DJ. Calcification of the mitral annulus and its complications. Am J Forensic Med Pathol 1982;3:109-113. 5. Simon MA, Liu SF. Calcification of the mitral valve annulus and its relation to functionalvalvular disturbance. Am Heart J 1954;48:497-505. 6. Korn D, DeSanctis RW, Sell S. Massive calcification of the mitral annulus: a clinicopathological study of fourteen cases. N Engl J Med 1962;267:900-909. 7. Kriwisky M, Goldstein J, Gotsman MS. Accessory atrioventricular pathway, supra-, and infrahisian conduction impaired due to mitral annulus calcification. Clin Cardiol 1987;10:818-820. 8. Iga K, Hori K. Left ventricular outflow obstruction caused by mitral ring calcification. Am Heart J 1990;119:418--419. 9. DeBono DP, Warlow CP. Mitral-annulus calcification and cerebral or retinal ischemia. Lancet 1979;ii:383-385. 10. Buehler DL, Stinson EB, Oyer PE, Shumway NE. Surgical treatment of aneurysms of the inferior left ventricular wall. J Thorac Cardiovasc Surg 1979;78:74-78. 11. Waldhausen JA, Petry EL, Kurlander GJ. Successful repair of subval-
13. 14.
15.
16.
285
vular annular aneurysm of the left ventricle. N Engl J Med 1966;275: 984-987. Bansal RC, Graham BM, Jutzy KR, Shakudo M, Shaw PM. Left vantricular outflow tract to left atrial communication secondary to rupture of mitral-aortic intervalvular fibrosa in infective endocarditis: diagnosis by transesophageal echocardiography and color flow imaging. J Am Coil Cardiol 1990; 15:499-504. Bhagwat AR, Patil PM, Loya YS, Sharman S. Subaortic aneurysm in infective endocarditis. Am Heart J 1991;122:588-589. Kessler KM, Kieval J, Saksena S, Sanderson TL, Myerburg RJ. Echocardiographic features of posterior left ventricular wall pseudoaneurysm due to Escherichia coli endocarditis. Am Heart J 1982;103:139-142. Kupari M, Verkkala K, Maamies T, Hiirtel G. Value of combined cross sectional and doppler echocardiography in the detection of left ventricular pseudoaneurysm after mitral valve replacement. Br Heart J 1987; 58:52-56. Verkkala K, Maamies T, Kupari M, Mattila T, Ala-Kulju K. Pseudoaneurysm of the left ventricle following mitral valve replacement. J Cardiovasc Surg 1990;31:242-246.
17. Bansal RC, Molony PM, Marsa ILl, Jacobson JG. Echocardiographic features of a mycotic aneurysm of the left ventricular outflowtract caused by perforation of mitral-aortic intervalvular fibrosa. Circulation 1983; 67:930-934. 18. Mambo NC, Silver MD, Brunsdon DFV. Bacterial endocarditis of the mitral valve associated with annular calcification. Can Med Assoc J 1978; 119:323-326. 19. Fulkerson PK, Beaver BM, Auseon JC, Graber HL. Calcification of the mitral annulus. Am J Med 1979;66:967-977. 20. Roberts WC, Perloff JK. Mitral valvular disease. Ann Intern Med 1972;77:939-975. 21. Salazar AE, Edwards JE. Friction lesions of ventricular endocardium. Arch Pathol 1970;90:364-376.