Clinical experience with the Nimbus pump. The Nimbus pump is an indwelling, electromagnetic powered left ventricular (LV) assist device inserted transfemorally. The inflow cannula (7 mm) is positioned across the aortic valve and the pump in the descending aorta. Indications for insertion include cardiogenic shock despite maximal medical support and PCWP greater than 18 mmHg, MAP less than 90 mmHg, and Cl less than 2 L/min/m2. Twelve patients underwent the attempt at surgical insertion of the Nimbus pump. Diagnoses included eight acute myocardial infarctions (AMI), two ischemic cardiomyopathy, one postpartum cardiomyopathy, and one transplanted heart rejection. Eight (67%) of twelve patients had successful insertion. One patient had peripheral vascular disease preventing passage, and three had femoral vessels too small for insertion (less than 7.5 Hagar dilator). Five patients with the diagnosis of AMI had successful insertion and three (60%) underwent sufficient LV recovery for removal of the device; the other two patients died of stroke and ventricular arrhythmias, respectively. Three patients with the diagnosis of cardiomyopathy had progression of the disease process, and their needs exceeded the capabilities of the pump and they died of multiorgan failure. The Nimbus pump is an attractive LV assist device because of its pumping capacity (3.5 L/min) and minor surgical procedure for insertion. However, its application is limited because of access route and size. The device appears to work well for patients in cardiogenic shock after AMI (60% recovery) but does not appear indicated for patients with cadiomyopathy. 