Editing Coronary circulation (section)

===Supply to papillary muscles===
The [[papillary muscle]]s attach the [[mitral valve]] (the valve between the [[left atrium]] and the [[left ventricle]]) and the [[tricuspid valve]] (the valve between the [[right atrium]] and the [[right ventricle]]) to the wall of the heart.  If the papillary muscles are not functioning properly, the mitral valve may leak during contraction of the left ventricle.  This causes some of the blood to travel "in reverse", from the left ventricle to the left atrium, instead of forward to the aorta and the rest of the body.  This leaking of blood to the left atrium is known as [[mitral regurgitation]].  Similarly, the leaking of blood from the right ventricle through the tricuspid valve and into the right atrium can also occur, and this is described as [[tricuspid insufficiency]] or tricuspid regurgitation.{{citation needed|date=April 2021}}

The anterolateral papillary muscle more frequently receives two blood supplies: [[left anterior descending]] (LAD) artery and the [[left circumflex artery]] (LCX).<ref name=voci>{{cite journal |vauthors=Voci P, Bilotta F, Caretta Q, Mercanti C, Marino B |title=Papillary muscle perfusion pattern. A hypothesis for ischemic papillary muscle dysfunction |journal=Circulation |volume=91 |issue=6 |pages=1714–1718 |year=1995 |pmid=7882478 |doi=10.1161/01.cir.91.6.1714}}</ref>
It is therefore more frequently resistant to [[coronary ischemia]] (insufficiency of oxygen-rich blood).  On the other hand, the posteromedial papillary muscle is usually supplied only by the PDA.<ref name=voci/>  This makes the posteromedial papillary muscle significantly more susceptible to [[ischemia]].  The clinical significance of this is that a [[myocardial infarction]] involving the PDA is more likely to cause mitral regurgitation.{{citation needed|date=April 2021}}