Anatomy, histology, and pathology of the cardiac conduction system—Part IV

Abstract

Summary: Metastatic tumor involvement of the heart as a basis for the genesis of various cardiac arrhythrmas is reviewed. The morphologic basis of pre-excitation syndromes and right ventricular dysplasia are also reviewed.

Examination of the Cardiac Conduction System

“…13 James fibers are atrial fibers that penetrate through the central fibrous body and connect to the His bundle, although this is somewhat of a misapplication of the original description by James. 42 James fibers are the morphologic basis for Lown-Ganong-Levine syndrome. Lown-Ganong-Levine patients have shortened PR interval, similar to that of WolffParkinson-White but without QRS widening.…”

“…41 They may consist of either working myocardium or conduction tissue. 42 Kent bundles may occur anywhere along the atrioventricular rim on either the right or left side and may constitute a fascicle of only a few fibers. Thus, they may be difficult to demonstrate histologically, often requiring thousands of sections.…”

Double Primary Cancers: Intrahepatic Cholangiocarcinoma with Myocardial Metastases and Lung Squamous Cell Carcinoma

“…However, myocardial metastases can cause sudden death or other significant clinical problems such as syncope, and indeed, such cases have been previously reported. For example, myocardial metastases can provoke atrial and ventricular heart rhythm disturbances and conduction defects, including complete atrioventricular block (5)(6)(7)(8)(9), and may cause myocardial infarction or angina pectoris as a result of invasion or compression of a coronary artery (1,(10)(11)(12). Although there are no established therapeutic strategies, several reports have shown that, in patients whose myocardial metastasis caused complete atrioventricular block, pacemaker implantation or systemic chemotherapy might be effective (7,8).…”

Atrial Metastatic Tumor: Transthoracic and Transesophageal Echocardiograph Imaging

“…Arrhythmias in patients with cardiac metastases is usually the result of concomitant factors such as hypoxemia, electrolyte imbalance, or anemia; however, arrhythmia can be secondary to tumors involving autonomic fibers or encroaching on the coronary arteries [17]. Overall, arrhythmia is the most prevalent manifestation of myocardial involvement by metastatic tumors [12,18]. The occurrence of arrhythmia without an obvious trigger in a patient with known malignancy suggests the possibility of metastatic myocardial involvement.…”