Bar calcification of the mitral anulus

J

THoRAc CARDIOVASC SURG

1987;94:399-404

Bar calcification of the mitral anulus A risk factor in mitral valve operations Between Jan. 1, 1979, and Jan. 1, 1986, 72 septuagenarians bad open heart operations for disease of the mitral valve. Thirty-two (44%) had additional operative procedures. Overall seven patients (9.7%) died within 30 days of operation. Eleven patients bad bar calcification of the posterior mitral anulus as defined by three criteria and 61 did not. No differences betweenthese two groups were present except for hospital mortality. Three of the 11 patients (27.3%) died at or soon after operation of complications resulting from the calcified annular bar. Only four of 61 patients (6.6%) without bar calcificationdied early. The difference in early mortality between the two groups is significant (p < 0.05)and identifies the presenceof bar calcification of the posterior mitral anulus as an independent risk factor of mitral valve operations in elderly patients.

Paul L. Cammack, M.D., Richard N. Edie, M.D., and L. Henry Edmunds, Jr., M.D., Philadelphia, Pa.

Calcification of the mitral anulus is a degenerative process':' related to aging':' that may be associated with arrhythmias, mitral stenosis, mitral insufficiency, or mixed valve lesions.l-" The process more commonly involves the posterior or mural anulus,! 2, 4-6 is two to four times more common in elderly women.!" and may affiict 9.4% of women and 2.7% of men over 60 years of age.' In contrast to rheumatic calcification, degenerative annular calcification involves only the base of the valve leaflets and adjacent ventricular myocardium and spares most of the leaflet tissue and all chordae (Fig. 1),u,4 The process may produce a shelf of calcium beneath the posterior leaflet that encroaches on the valve orifice to produce a functionally stenotic valve.1,5, 6 Mitral insufficiencyresults if the bar of calcium extends toward the atrium. I, 5, 6 This elevates and immobilizes the mural leaflet by stretching the free edge and chordae over a ledge of calcium (Fig. 1).1,5,6 Bar calcification may also be associated with myxomatous degeneration of the valve and mitral valve prolapse.v" As the population ages, surgeons increasingly see From the Division of Cardiothoracic Surgery, Department of Surgery, Hospital of the University of Pennsylvania, Philadelphia, Pa. Received for publication Aug. 4, 1986. Accepted for publication Sept. II, 1986. Address for reprints: L. Henry Edmunds, Jr., M.D., Hospital of the University of Pennsylvania,3400 Spruce St., 4th Floor, Silverstein Pavilion, Philadelphia, Pa. 19104.

stretched chordae

----- papi Ilary muscle

-

left ventricular wall

Fig. 1. Drawing of the location of degenerative bar calcification of the posterior mitral anulus. The accumulated calcium elevates the base of the mitral leaflet, which is usually only slightly thickened by fibrosis, The calcium may extend into the subannular ventricular myocardium. Note the proximity of the circumflex coronary artery and the thinness of the wall at the atrioventricular junction.

elderly patients with symptomatic mitral valve dysfunction. This study reports on 11 septuagenarians who had nonrheumatic bar calcification of the mitral anulus and open mitral valvular operations. The study identifies the presence of annular bar calcification as an independent risk factor of operation.

399

40 0

The Journal of Thoracic and Cardiovascular Surgery

Cammack, Edie, Edmunds

Fig. 2. Lateral chest radiograph of a patient with bar calcification of the posterior mitral anulus.

Table I. Demographic characteristics of two groups Bar calcification Present (n

Mean age (yr) Women NYHA Class III NYHA Class IV Emergency operation Patients with additional operative procedures Hospital mortality

= Il)

74 9 (82%) 6 4 I 3 (27%)

3 (27%)

Absent

(n = 61)

74 41 (67%)

26 33 2

29 (48%) 4 (6.6%)

Legend: NYHA refers to the New York Heart Association classification. Emergency operation is defined as immediate operation in any available operating room.

Methods

From Jan. I, 1979, through Jan. 1, 1986, 72 consecutive patients 70 years of age or older had open mitral valve operations with or without additional procedures by three surgeons at the Hospital of the University of Pennsylvania. The average age was 74 years; 50 (69%) were female. Eleven of these 72 patients had bar calcification of the mitral anulus. We define bar calcification by three criteria: absence of any history of rheumatic fever.t? radiographic presence of posterior mitral annular calcification extending 4 em or more (Fig. 2),5-7 and operative confirmation of an annular

subleaflet calcified bar that does not involve nonbasal leaflet tissue or chordae. All (72) operations were performed with either membrane or bubble oxygenators, cold crystalloid cardioplegia, and moderate hypothermia to nasopharyngeal temperatures of 26 to 28 C. Distal coronary bypass grafts were constructed before valves were addressed; the mitral valve was repaired or replaced before the aortic valve was replaced. Hospital mortality is defined as death within 30 days of operation. Characteristics of patients with bar calcification (11) were compared to those in patients without bar calcification (61) by chi square analysis. 0

0

Results

The two groups, distinguished by the presence or absence of mitral annular calcification, are comparable with respect to age, sex predominance, symptoms, and number of additional operative procedures (Table I). There is a strong female predominance, particularly in the group with bar calcification. Additional operative procedures are more common in the group without bar calcification (Table 11). None of the differences between groups is significant. Three patients with bar calcification died during or shortly after operation of complications related to the bar. Four of 61 patients without bar calcification died. Two of these four patients had emergency operation for

Volume 94 Number 3 September 1987

Bar calcification of mitral anulus

40 1

Table Il. Operations in two groups Bar calcification

Mitral valve replacement Mitral valve reconstruction Mitral valve replacement plus coronary bypass grafts Mitral valve reconstruction plus coronary bypass grafts Mitral valve replacement plus tricuspid annuloplasty Mitral and aortic valve replacement Mitral and aortic valve replacement plus coronary bypass grafts Mitral valve reconstruction and aortic valve replacement Exploratory cardiotomy Total

Present*

Absent

6 1

28

o

4 10

o o

3

12

2

2

o o 11

61

'Six St. Jude Medical mitral prostheses and three porcine heterograft prostheses were used in the group with bar calcification.

acute postinfarction mitral insufficiencyand cardiogenic shock." The other two patients (New York Heart Association Class IV) died of low cardiac output 1 and 2 days after operation. One of these had systemic pulmonary arterial pressures. The difference in hospital mortality (6.6% versus 27.3%) between the two groups is significant (p < 0.05) even when the two deaths from emergency operations are included. Table III lists details of the 11 patients with bar calcification. Ages ranged from 70 to 79 years. Eight of 11 patients had prior histories of hospitalizations for congestive heart failure but only one had a previous myocardial infarction. Five patients had mixed mitral stenosis and regurgitation, one pure stenosis, and five pure regurgitation. Eight had atrial fibrillation and three sinus rhythm. Lateral chest radiographs demonstrated the extensive bar calcification of the posterior mitral anulus in all patients. Seven of 11 had an enlarged left atrium. Nine patients had echocardiograms," 7. 9 but severe calcification of the mural anulus was described in only eight. Ten patients had cardiac catheterization; one did not because of rapidly deteriorating hemodynamics (Table III). In nine patients the mitral valve was excised and replaced; in one the valve was repaired with a Carpentier-Edwards ring, and in one the valve was considered

Fig. 3. Right arterior oblique cineangiograms in systole (A) and diastole (B) of Patient 1, showing extensive calcification of the posterior mitral anulus. Note the small ventricular cavity at end-systole in this 79-year-old woman who had pure mitral regurgitation and no mitral stenosis.

inoperable and the surgeon closed without repair or replacement. Operations are listed in Table II. Polyester (0) mattress sutures buttressed with Teflon felt pledgets were passed from the atrium over, through, and sometimes under the bar to anchor the prosthetic valve or ring in 10 patients. The bar of calcium was not disturbed or debrided in seven patients, including Patient 5, whose valve was not removed, and Patient 10, whose valve was reconstructed (Table III). One of these patients (Patient 1) died of ventricular rupture. In four patients the bar of calcium was partially debrided. Two patients (Patients 8 and 9) survived operation, one died in the operating room of low cardiac output, and the fourth died of left ventricular rupture 14 hours after operation. The average stay in the intensive care unit of the eight

The Journal of Thoracic and Cardiovascular Surgery

402 Cammack, Edie, Edmunds Table m. Patients with bar calcification Patient No.

CI (L/m 2/min)

Diagnosis

MR MR/MS MR, AS, CAD

I

2 3 4 5 6 7 8 9 10

78 71 73 70 73 72

78

II

72

Mean ± SD

74.1 ± 3.2

F F F M F F M F

III III III III III III IV IV

NSR AF AF NSR AF AF AF NSR

AS/MS AS/MR MR/MS MR MR/MS MR/MS MR/MS MR, AS/CAD

2.4 27/13

62/23 50/25 45/20 35/10 40/16 58/25 70/40 70/32 53/22

15 22 26 20 13 20 27 15 34 21.4 ± 6.4

5

45

7.6

1.6

18 20 8 20 16 16

70 68

3.8 7.2 5.0 6.3 2.9 7.7

3.1 2.7

IS

64 65

16 15.4 ± 5.1

55 70

61.4 ± 9.1

5.6 6.0 ± 1.8

1.7

1.9 2.0 1.4 1.9 2.1 2.1 ± 0.5

Legend: Details of II patients with bar calcification. NYHA class. New York Heart Association classification. PAP, Pulmonary arterial pressure. PCWP. Pulmonary capillary wedge pressure. EF. Ejection fraction period. A-Vo, diff., Arterial-venous oxygen difference. CI, Cardiac index. IABP. Intra-aortic balloon pump. E. Emergency operation. AF. Atrial fibrillation. NSR, Normal sinus rhythm. MR, Mitral regurgitation. MS, Mitral stenosis. MR/MS. Mixed mitral disease. AS. Aortic stenosis. CAD. Coronary arterial disease. MVR. Mitral valve replacement. AVR, Aortic valve replacement. CABG, Coronary arterial bypass grafts.

survivors was 3 days. Seven patients were discharged an average of 9 days after operation. One patient, who developed acute neurologic symptoms as the result of an unrecognized benign cerebellar tumor, remained in the hospital 1 month. Only one of three patients who died had an autopsy (Patient 1).

Discussion The anatomical location and extent of bar calcification of the mitral anulus presents formidable technical problems to the cardiac surgeon. Although degenerative annular calcification can involve the entire mitral ring, more commonly only the posterior or mural anulus is invclved.l-" Accumulated calcium deposits may extend into and essentially replace most of the ventricular myocardium adjacent to the valve anulus.': 2, 4, 6 At this junction the normal ventricle is tenuously attached to the normal atria and anulus.'? The circumflex coronary artery passes in the atrioventricular groove just outside the thin-walled junction of ventricular myocardium, posterior atrial wall, and posterior mitral valve anulus.9, 10 Last, the myocardium in elderly women is notoriously friable. Unlike calcification of rheumatic or previously infected valves, which primarily affects leaflets and chordae, degenerative calcification primarily affects the vulnerable junction of ventricle, atrium, and atrioventricular valves'v-" and produces mitral stenosis or insufficiency secondarily.I. 4, 6 Our experience with 11 patients with bar calcification of the mitral anulus produced a variety of technical modifications but no consistently effective method to

deal with the problem. Despite one success, in most patients the posterior annular bar essentially prevents mitral reconstruction and reduction and realignment of the mitral anulus. Most often, annular dilatation primarily involves the posterior anulus, which cannot be reduced if bar calcification is present. Our single success resulted because we could reduce the anulus at both commissures and because we could repair ruptured chordae and resect redundant leaflet tissue in two places of what originally had probably been a prolapsing mitral valve. Debridement of the calcified bar may result in separation of the atrium and ventricle with exposure of the circumflex coronary artery.'? Partial debridement is often possible and sometimes necessary to place a prosthetic valve, but fracture or movement of the residual bar risks rupture and may injure the lateral ventricular wall when calcium extends downward into the ventricular wall. Partial debridement and placement of pledget-supported mattress sutures passed from the atrium through or sometimes under the bar are required to anchor the low-profile St. Jude Medical prosthesis. Unfortunately, partial debridement and possiblyventricular injury because of movement of the extensive ventricular calcium may have contributed in one patient to severe left ventricular dysfunction and death in the operating room. Theoretically, the mounted porcine heterograft prosthesis with central flow offers the best solution. The height of this prosthesis allows atrial anchorage of the sewing ring just above the posterior calcified sector of

Volume 94 Number 3

Bar calcification of mitral anulus

September 1987

Hospital course

Operation MVR, porcine MVR, 51. Jude Medical AVR, MVR, CABG X I 51. Jude Medical

Yes Yes Yes

AVR, MVR, 51. Jude Medical Exploratory cardiotomy MVR, 51. Jude Medical MVR, porcine MVR, 51. Jude Medical MVR, porcine Mitral reconstruction AVR, MVR, CABG X 3, 51. Jude Medical

No No No No No No No No

Ruptured ventricle, 3 hr Died in operating room Discharged to community hospital, 30 days---eerebellar tumor Ruptured ventricle, 14 hr Discharged home, 6 days Discharged home, 9 days Discharged home, 9 days Discharged home, 9 days Discharged home, 9 days Discharged home, 9 days Discharged home, 15 days

the mitral anulus. The bar of calcium need not be debrided, but is accommodated beneath the sewing ring abutting the struts of the prosthesis. Unfortunately, porcine heterograft prostheses cannot always be used. Left ventricular cavity size decreases with agel I and may be small at end-systole even in patients with pure mitral insufficiency (Fig. 3). One fatal case of left ventricular rupture, which was located at the junction of the calcified bar and uncalcified ventricular myocardium (Patient 1, Table III), occurred 3 hours after operation despite prophylactic use of intravenous nitroprusside and the intra-aorta balloon. In this case, the lever effect of the prosthesis may have caused motion of the bar and disruption at the junction of the calcified and uncalcified myocardium. Two of the 11 patients (18%) died of ventricular rupture despite anticipation of the possibility and extraordinary efforts to prevent rupture by reducing ventricular afterload. Ventricular rupture occurs in 1.5% of patients after mitral valve replacement and is usually fatal.12, IJ Sites of rupture include the atrioventricular groove, the lateral and posterior ventricular muscle wall just beneath the annular attachment, and the ventricular wall at the level of the papillary muscles. 12. 13 Improved surgical techniques have largely controlled traumatic injuries to ventricular myocardium." These techniques include avoidance of intraoperative trauma and avulsion injury to the anulus, retention of papillary muscles, and placement of sutures in the mitral anulus as opposed to the subannular ventricle. However, as Cobbs, Hatcher, and Craver" have shown, removal of the mural mitral leaflet and chordae may remove an anchoring mechanism for the lateral ventricular wall. Loss of local anchoring may allow the adjacent wall to bulge outward

403

Present status Hospital death Hospital death Alive, 56 mo, Class II Hospital death Alive, 15 mo, Class IV Alive, 27 mo, Class I Alive, 26 mo, Class I Alive, 29 mo, Class I Died 12 rno, sudden, unexpected death Alive, 15 mo, Class I Died, 6 mo, prosthetic endocarditis

during systole. The resultant increase in wall stress may lead to rupture. Retention of portions of the mural leaflet and subvalvular apparatus may reduce the possibility of rupture from this cause. 12. 14 Unfortunately, bar calcification of the posterior mitral anulus must also be recognized as a risk factor for ventricular rupture. In addition to the two cases reported herein, four of 14 cases with ruptured ventricle reported by Spencer, Galloway, and Colvin" and four of 18 cases reported by Dark and Bain" had calcification of the mitral anulus. Details are not available, but some of these patients may have had degenerative calcification of the mitral anulus as the primary cause of their mitral valve dysfunction. Elderly symptomatic patients with mitral valve dysfunction will increasingly be considered for operation. Although mortality of mitral valve replacement is high in patients over 70 years,15.l6 this report documents considerably improved results and identifies a new and important operative risk factor. However, despite the increased risks of operative death associated with bar calcification of the posterior anulus, mitral valve surgery may be the most attractive option for some patients. Six of eight survivors (including the patient who had exploratory cardiotomy) remain alive 15 to 56 months after operation. Others have also reported survivors,' although in one instance mitral valve replacement appears to have accelerated calcium deposits in the posterior anulus."

REFERENCES 1. Korn D, DeSanctis RW, Sell S. Massive calcification of the mitral annulus. N Engl J Med 1962;267:900-9.

404 Cammack, Edie, Edmunds

2. Rosenthal J, Feigin I. Pathology of the mitral valve in the older age groups. Am Heart J 1947;33:346-61. 3. Savage DD, Garrison RJ, Castelli WP, et al. Prevalence of submitral (anular) calcium and its correlation in the general population-base sample (the Framingham study). Am J Cardiology 1983;51:1375-8. 4. Geill T. Calcification of the left annulus fibrosus (230 cases). Acta Med Scand 1950;138:(Suppl 239):153-6. 5. Fulkerson PK, Beaver BM, Auseon JC, Graber HL. Calcification of the mitral annulus. Am J Med 1979; 66:967-77. 6. D'Cruz lA, Cohen HC, Prabbu R, Bisla V, Glick G. Clinical manifestations of mitral annulus calcification with emphasis on its echocardiographic features. Am Heart J 1977;94:367-77. 7. Nestico PF, Depace NL, Morgan THJ, Kotler MN, Ross J. Mitral annular calcification: clinical, pathophysiologic, and echocardiographic review. Am Heart J 1984;107:98996. 8. Tepe NA, Edmunds LH Jr. Operation for acute postinfarction mitral insufficiency and cardiogenic shock. J THORAC CARDIOVASC SURG 1985;89:525-30. 9. D'Cruz I, Panetta F, Cohen H, Gerald G. Submitral calcification or sclerosis in elderly patients: M mode and two-dimensional echocardiography in "mitral anulus calcification." Am J Cardiol 1979;44:31-8.

The Journal of Thoracic and Cardiovascular Surgery

10. Roberts WC, Morrow AG. Causes of early postoperative death following cardiac valve replacement. J THORAe CARDIOVASC SURG 1967;54:422-37. II. Roberts WC, Perloff JK. Mitral valvular disease. Ann Intern Med 1972;77:939-75. 12. Spencer FC, Galloway AC, Colvin SB. A clinical evaluation of the hypothesis that rupture of the left ventricle following mitral valve replacement can be prevented by preservation of the chordae of the mural leaflet. Ann Surg 1985;202:673-80. 13. Dark JH, Bain WHo Rupture of posterior wall of left ventricle after mitral valve replacement. Thorax 1984; 39:905-11. 14. Cobbs BW Jr, Hatcher CR Jr, Craver JM. Transverse midventricular disruption after mitral valve replacement. Am Heart J 1980;99:33-50. 15. Nicolaou N, Kinsley RH. Mitral valve replacement in the elderly. S Afr Med J 1984;65:598-600. 16. Stephenson LW, MacVaugh H III, Edmunds LH Jr. Surgery using cardiopulmonary bypass in the elderly. Circulation 1978;8:250-4. 17. Bulkley BH, Morrow AG, Roberts We. Calcification of the mitral annulus: a late complication of valve replacement with caged-ball prosthesis. Am J Cardiol 1973; 31:123.