Valvular damage and subsequent dysfunction, as well as intracardiac fistula formation, can be accurately defined by use of two-dimensional and Doppler echocardiography from a transthoracic or transesophageal approach. Conduction abnormalities may signal the extension of valvular infection to the septum and its major conduction tissues. The development of PR interval prolongation or the appearance of a new left bundle branch block or of a new right bundle branch block with left anterior hemiblock suggests that the infection has spread from the aortic valve into the ventricular septum. In the absence of digitalis toxicity or a recent inferior myocardial infarction, the development of nonparoxysmal junctional tachycardia, a Wenckebach block, or complete heart block with a narrow QRS complex serves as a clue to the spread of infection from the mitral annulus into the AV node and proximal bundle of His. The development of new and persistent conduction abnormalities, particularly in patients with infected aortic valves, usually indicates the presence of a deep-seated abscess and the need for debridement and valve replacement.
Conduction abnormalities are an indication for pacing.
Another rhythm disturbance that may be seen in infective endocarditis is ventricular premature beats, which in the absence of electrolyte abnormalities or digitalis toxicity are caused by myocarditis, myocardial abscesses, or small coronary emboli. Abscess of the aortic valve ring may be suggested by the recent onset of aortic regurgitation, by the presence of a high degree of AV block, and by the development of pericarditis. A multivariate analysis of clinical, microbiological, and echocardiographic findings in patients with native valve endocarditis identified aortic valve infection and intravenous drug abuse as independent significant risk factors associated with extension of infection into periannular tissue. The authors suggested that patients with these risk factors be routinely screened for this complication. Transesophageal echocardiography is the most sensitive and preferred noninvasive test for detecting myocardial abscesses in both native and prosthetic valve endocarditis.