Myocardial Abscess on the Anterolateral Papillary Muscle

A 51-year-old man with type 1 diabetes was referred to Osaka City General Hospital because of a high fever. Blood culture identified Group B streptococcus. Echocardiography showed that the anterior papillary muscle in the left ventricle was bulging considerably with some small fluttering vegetations (Figure A; Supplementary Movie 1). Upon surgical inspection, the mitral valve leaflets did not appear to be affected by the infection. The anterolateral papillary muscle showed large swelling and a blackish appearance with fragile grayish vegetations on the surface (Figure B; Supplementary Movie 2). These parts of the tissue were excised, and the mitral valve was replaced with a mechanical valve. The patient was placed on intravenous antibiotic therapy for 6 weeks after the operation. Histological examination of the excised tissue revealed that inflammatory cells and bacterial substances had infiltrated the necrotic papillary muscle tissue (Figure C–E). Seven years after the operation, the patient is doing well, with no signs of recurrent infection.

Figure.

(A) Preoperative echocardiography. (B) The bulging anterolateral papillary muscle. (C) Macroscopic image of the resected papillary muscle. (D) Micrograph showing dense inflammatory infiltrate. Hematoxylin and eosin (HE) staining. (E) Gram staining revealed bacterial substances (arrow).

Papillary muscle infection is a rare phenomenon that has been reported to occur in only 2% of myocardial abscesses.¹ As to its etiology and mechanisms, a previous report described the secondary effects of valvular endocarditis;² however, in the present case, there was no other evidence for an infection in the heart.

IRB Information

This study was approved by the Ethics Committee of Osaka City General Hospital (No. 1406037).

Supplementary Files

Supplementary Movie 1.

Supplementary Movie 2.

Please find supplementary file(s);

http://dx.doi.org/10.1253/circj.CJ-22-0038

References

• 1.   Daniel WG, Mügge A, Martin RP, Lindert O, Hausmann D, Nonnast-Daniel B, et al. Improvement in the diagnosis of abscesses associated with endocarditis by transesophageal echocardiography. N Engl J Med 1991; 324: 795–800.
• 2.   Atoui R, Hijal T, Fraser R, Shum-Tim D. Acute rupture of both papillary muscles after aortic valve replacement for infective endocarditis. J Thorac Cardiovasc Surg 2009; 137: 1275–1276.