Approach Considerations
The documentation and characterization of second-degree atrioventricular (AV) block by means of ECG is usually an essential investigation. This is ideally performed with a 12-lead ECG, although ambulatory ECG monitoring may be needed to identify and characterize infrequent episodes.
Electrophysiologic study to assess the level of block and subsidiary pacemaker rate may be beneficial in some patients. In patients with suspected carditis or cardiomyopathy, an endomyocardial biopsy may be performed at the same time.
Histologic findings
When endomyocardial biopsy is performed to assess heart block in conjunction with myocardial dysfunction, histochemically stained sections should be assessed for myofibrillar destruction or for lymphocytic, fatty, or fibrotic infiltration. Electron microscopy should be performed to assess any mitochondrial or other ultrastructural alterations that may be present.
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