We report a case of successful TandemHeart implantation for cardiogenic shock due to critical aortic stenosis using a 21 Fr transseptal cannula which was safely advanced through an existing inferior vena cava (IVC) filter under fluoroscopic guidance. This supported the patient through balloon valvuloplasty and subsequent definitive surgical valve replacement. This report demonstrates that the IVC filter can be safely crossed with a sheath as large as 21 Fr in size. In addition, patients with an existing IVC filter requiring a TandemHeart percutaneous ventricular assist device should not be denied this device for fear of dislodging the filter.