surgery: etiologic classification by radionuclide ventriculography

Early after open heart surgery, cardiac shock due to tamponade is easily misdiagnosed as ventricular dysfunction. The distinction is critical to successful therapy. We assessed the utility of 99mTc-red blood cell, gated equilibrium radionuclide ventriculography in 50 patients with early postoperative cardiac shock after historical, clinical, and invasive hemodynamic evaluation failed to identify either tamponade or ventricular dysfunction as the specific cause of their shock. The cause was established by radionuclide ventriculography in 45 of 50 patients and led to a change in therapy in 21 patients. A single cause was found in 35 patients: 13 had severe global dysfunction of the left ventricle (three patients), right ventricle (seven patients), or both ventricles (three patients); three had severe segmental left ventricular dysfunction; and 19 had an exaggerated region of photon deficiency (nine patients) or an abnormal and accumulating blood pool (10 patients) surrounding small hyperdynamic ventricles. Sixteen of these 19 patients with scintigraphic evidence of tamponade underwent aspiration with a pericardial needle or reoperation early after radionuclide ventriculography, resulting in confirmation of scintigraphic findings and improved hemodynamics. Ten additional patients had combined ventricular dysfunction and a pericardial abnormality, and five of these underwent reoperation resulting in improved hemodynamics. Radionuclide ventriculography provided no explanation for the cause of cardiac shock in five patients. Thus, the various causes of cardiac shock early after open heart surgery can be distinguished by 99mTc-red blood cell, gated equilibrium radionuclide ventriculography, eliminating diagnostic uncertainty that can occur with traditional evaluation. Circulation 71, No. 6, 1153-1161, 1985. CARDIAC SHOCK complicating open heart surgery is well known in the setting of poor preoperative left ventricular function and when excessive postoperative bleeding leads to tamponade. When it occurs under less well-defined circumstances, differentiation of ventricular dysfunction from tamponade can be difficult by clinical examination, chest x-ray, electrocardiography, and hemodynamic monitoring. Therapy, depending on the cause of shock, may include operative exploration to relieve tamponade or administration of vasoactive drugs with or without intra-aortic balloon counterpulsation to improve ventricular function. From the Division of Cardiology and the Department of Thoracic and Cardiovascular Surgery, Cedars-Sinai Medical Center, and the Department of Medicine, UCLA School of Medicine, Los Angeles. Supported in part by a grant provided by Mr. and Mrs. Henry Jaffe of Los Angeles, and by SCOR IHD grant HL-17651 from the National Heart, Lung, and Blood Institute, NIH, Bethesda. Address for correspondence: Timothy M. Bateman, M.D., CedarsSinai Medical Center, 8700 Beverly Blvd., Room 6215, Los Angeles, CA 90048. Received Sept. 25, 1984; revision accepted Feb. 28, 1985. Vol. 71, No. 6, June 1985 In the early postoperative patient, 99mTc gated equilibrium cardiac blood pool scintigraphy has been used primarily for determining the time course of postoperative ventricular recovery. 1 Theoretically, it could be a valuable clinical tool in patients who develop cardiac shock after open heart surgery. We therefore designed this study to determine the utility of portable cardiac blood pool scintigraphy in patients with cardiac shock of uncertain cause early after open heart surgery.