Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3654_Библиотеки_им_академика_М_И_Перельмана

of septic vegetations with embolism, metastatic infection and septicemia.

Local complications of IE occur in the valve components (Figs. 6.5 and 6.6) or in the perivalvular region, and they also vary, based on whether atrioventricular or semilunar

valves are affected (Table 6.1). Vegetations are usually attached to the atrial side of atrioventricular valves and to the ventricular side of semilunar valves, at the valve line closure. IE may present with vegetations of various sizes, which in the acute phase consist of septic thrombi entrap­ping microorganisms and neutrophil inltrates (Fig. 6.4). Sometimes, vegetations may be so small as to be overlooked by the pathologist.

At present, evidence of endocardial vegetations through echocardiography plays a major role for an invivo clinical diagnosis (“Duke criteria”) (Table6.3), even in the absence of positive blood cultures. A molecular approach, by employ­ing polymerase chain reaction either on excised valves or blood, may enhance the diagnosis of valvular IE.Cusp dis­ruption with loss of substance accounts for tearing, fraying, perforation, and bulging, even in the absence of vegetations, especially when the causative microorganism is a Staphylococcus (Fig.6.5). Valve incompetence is the usual hemodynamic complication with left ventricular decompen­sation and congestive heart failure. It may be associated with stenosis if vegetations are huge, as it is the case of fungal infections causing valve obstruction. In the subacute-chronic phase, microorganisms may disappear, replaced by granulo­matous inammation including giant cells, and vegetations may transform into coarse calcic deposits. Local spread of infection includes extension to the aortic wall that may lead to development of sinus of Valsalva aneurysms, ring abscess, tunnels, and stulae to the surrounding cardiac chambers (right and left atria and ventricles) (Fig.6.11). Rupture into the pericardial cavity with tamponade may occur. Transesophageal echocardiography is highly accurate in the detection of complications, such as paravalvular abscesses or mycotic aneurysms. Aortic root complications carry an

erative recurrence. Homografts are generally preferred to treat these complications. Extension of IE from the aortic to the mitral valve occurs through mitro-aortic brous continu­ity. A marker of such complication is the development of a septic aneurysm in the anterior leaet of the mitral valve (satellite infection or “kiss” lesion), with or without perfora­tion (Fig.6.12). Involvement of the atrioventricular conduc­tion system may account for atrioventricular block, while extension to the membranous septum with rupture may cre­ate ventricular septal defect with interventricular or ventricu­loatrial communications.

Apart from cusp vegetations and perforations, which do not differ substantially from those occurring in the semilu­nar valves, IE of atrioventricular valves is peculiar in so far as the subvalvular apparatus (chordae tendineae and papil­lary muscles) may also be involved (Fig. 6.13). Papillary muscles rupture may occur, either due to septic localization on their tip or to myocardial necrosis because of coronary embolism. Perivalvular extension of the infection and ring abscesses are rare if IE is localized at atrioventricular valves.