Sub-aortic tendon induced ST-segment elevation - a new echo-electrocardiographic phenomenon?

Abstract

The causes for ST-segment elevation other than myocardial infarction are numerous. The existence of left ventricular false tendons has been known for more than a century. Currently, the clinical entities associated with these left ventricular false tendons include innocent murmurs and premature ventricular contractions. A case report is presented where such a false tendon, attached to the interventricular septum, is responsible for striking ST-segment elevation in the anterior precordial leads. It is proposed that this is a newly observed entity├óÔé¼ÔÇØthat of subaortic tendon-induced STsegment elevation. This is proposed as a totally benign phenomenon with the clinical importance in that it should not be confused with other pathological processes, such as the Brugada syndrome.

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The first description of so called false tendons inside the left ventricle was published 115 years ago 1. These structures are also described in the literature as: left ventricular moderator bands, anomalous cords, left ventricular bands and aberrant tendons 2. Abdulla et al 3 examined these tendons histologically and suggested that they are intracavitary radiations of the bundle of His. Embryologically, these false tendons are thought to derive from the inner muscle layers of the primitive heart and in addition to Purkinje cells, they also contain myocardial fibers, blood vessels, connective tissue and fibrous tissue 2 . Anatomically, these tendons have been divided into longitudinal and transverse tendons├óÔé¼ÔÇØlongitudinal tendons extending from the ventricular septum to the posteroapical wall and transverse tendons extending between the septum and the lateral wall. 4

These tendons have been shown to be a cause of functional ejection murmurs 2, 3, 4, 5. It has also been documented that they are associated with both uni-and multifocal premature ventricular contractions (PVC`s) 4, 6. These PVC`s are poorly controlled by antiarrhythmic drugs, but easily suppressed by exercise 4. There are currently two hypotheses for the generation of these PVC`s 4: These tendons contain Purkinje fibers and it is known that the automaticity of Purkinje cells is increased by mechanical stretching 4, 7 . It may be that mechanical stretching of the tendon can generate the PVC or alternatively, the mechanical strectch of the ventricular wall, where the tendon inserts, may trigger the PVC.

A case report is presented where it is postulated that a left ventricular false tendon, attaching to the interventricular septum in a subaortic location, is responsible for striking ST-segment elevation in the anterior precordial leads.

A 34-year old Caucasian male was referred for a cardiovascular examination, because of an abnormal electrocardiogram, demonstrating striking ST-segment elevation in leads V1, 2 and 3 (Figure 1). The patient is totally asymptomatic. The ECG was done by his primary care physician for insurance purposes for an insurance policy he applied for. He is an athlete who competes in marathon running in his spare time.

12-lead electrocardiogram.

This is the 12-lead electrocardiogram which clearly demonstrates the striking ST-segment elevation in leads V2 and V3.

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References
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