A 56-year-old woman presented to the cardiology clinic with a 7-day history of dyspnea and chest pressure. An echocardiogram showed a flail posterior mitral valve leaflet, and subsequent left heart catheterization showed complete occlusion of the first obtuse marginal coronary artery. Further investigation demonstrated the culprit lesion to be ischemic partial rupture of the posteromedial papillary muscle. Timely recognition of this condition allowed for an optimal clinical outcome. In this Cardiology Grand Rounds, the authors further describe the above presentation of ischemic partial papillary muscle rupture and provide a brief review of the pathophysiology, diagnosis and treatment of this condition.