Skeletal muscle tissue was obtained from the vastus lateralis or peroneus brevis muscles of 34 healthy volunteers. Focal and extensive areas of Z band streaming and disruption of myofibrillar architecture without Z band streaming were quantified in Araldite-embedded specimens examined in the phase microscope. Extensive areas of Z band streaming in more than 2.0 percent of fibers was present in only two of the 34 volunteers. Myofibrillar disruptions without Z band streaming was much less common than Z band streaming. The size of extensive areas of Z band streaming or myofibrillar disruptions was quantified by counting the number of adjacent fibrils and contiguous sarcomeres occupied by either type of lesion. These data should be of use in determining if such lesions are present in excessive amounts in suspected pathologic material.

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A 65-year-old man with a permanent pacemaker placed for atrioventricular block presented to the emergency department with 4 days of fever, gastrointestinal complaints, and back pain. On presentation, he was febrile, tachycardic, and hypotensive, with a significant leukocytosis. Urine and blood cultures grew methicillin-sensitive staphylococcus aureus in 6/6 bottles. The patient was initiated on appropriate antibiotic coverage, including nafcillin, resulting in sterilization of blood cultures. Transesophageal echocardiography revealed a vegetation on the pacing wire, likely involving the tricuspid valve, necessitating removal of the pacing lead (online-only Data Supplement Movies I and II). Four weeks into his antibiotic course, continued fevers along with a new holosystolic murmur at the apex of his heart prompted repeat echocardiography, which revealed a persistent mobile echodensity on the tricuspid valve and a new mobile echodensity on the mitral valve, as well, associated with severe mitral regurgitation (online-only Data Supplement Movie III). The patient was considered for valve replacement surgery, and preoperative coronary angiography was performed. Figure 1A shows multiple mycotic aneurysms (arrows) in coronary vessels that were not present 4 months earlier ( Figure 1B). Based on the involvement of multiple epicardial vessels, and in light of the patient's clinical status (which included difficult-to-control gastrointestinal bleeding and renal insufficiency), a decision was made to treat the patient conservatively with antibiotics. The patient defervesced, remained hemodynamically stable, and finished a 12-week course of nafcillin.Despite aggressive medical management of his valvular disease, he presented to the clinic 6 months later with shortness of breath, cyanosis, ascites, and lower-extremity edema. Repeat transesophageal echocardiography revealed severe mitral regurgitation (online-only Data Supplement Movie IV) and moderate tricuspid regurgitation. He was admitted for medical optimization of his congestive heart failure before cardiac surgery. Regadenoson positron emission tomography myocardial perfusion imaging revealed a large area of ischemia in the left anterior descending and circumflex artery distributions (Figure 2). Repeat cardiac catheterization revealed enlargement and septation of the aneurysms (Figure 3). He underwent mitral valve repair with chordoplasty to A1 and A2 and coronary artery bypass grafting with left internal mammary artery to the left anterior descending artery, saphenous vein graft to the obtuse marginal artery, and saphenous vein graft to the posterior descending artery and left posterior left ventricular branch. His postoperative course was uncomplicated, his breathing improved, and repeat transthoracic echocardiography showed only mild mitral regurgitation (online-only Data Supplement