Atypical Chordae Tendineae of the Canine (Canis familiaris) Right Atrioventricular Valve

The canine right atrioventricular valve cusps are anchored to papillary muscles by chordae tendineae. During ventricular systole, these tendineae keep the cusps from being pushed into the atrium. While this is the general description for chordae tendineae, several researchers have briefly documented chordae tendineae in animal and human hearts that do not attach to papillary muscles. In the 39 canine hearts examined, atypical chordae tendineae were observed in two hearts. In both dogs, a single stranded chordae tendineae extended from the free edge of the parietal cusp of the right atrioventricular valve to the ventricular free wall. While the discovery of these atypical tendineae provides additional information on canine cardiac anatomy, their presence may also be clinically significant. A review of the veterinary and biomedical literature showed entanglement in normal chordae tendineae can be a complication during cardiac catheterization or pacemaker lead placement. Given this issue with normal chordae tendineae, it seems logical to propose that these atypical tendineae could also cause catheter or pacemaker lead entanglement and therefore warrant further study and documentation.