Friday August 3, 2007
step-up oxygen saturation and VSD


Case: 61 year old male admitted with Angina. Cardiac cath. showed 3 vessel disease. Cardiac Bypass surgery planned for next morning. Patient admitted back to CCU with protocolized post cardiac cath orders. Around 12 midnight, patient suddenly became hypotensive. Arriving at bedside you noticed tall v waves on pulmonary artery catheter tracings. You suspect flail Mitral valve (Mitral regurgitation - MR) with possible ruptured Chordae tendinae. Cardiologist is also concerned about ventricular septal defect (VSD). Unfortunately, STAT Echo is not available at 12 MN. What would be the best way to differentiate between MR and VSD ?



VSD is very difficult to diagnose from MR on clinical grounds. VSD can be differentiated from MR by demonstrating a step-up in oxygen saturation in the right ventricle. (By collecting blood from CVP, RV and PA/distal ports of PA catheter).

If oxygen saturation level in right ventricle is more than 5% from right atrium or 8% from pulmonary artery (due left-to-right shunt across the ventricular septum), it is diagnostic of VSD. In this era of technology, echocardiography is preferable, if available, due to its non-invasive and good diagnostic value.



Reference: click to get abstract/article

Hemodynamic complications of ventricular septal rupture after acute myocardial infarction - Catheterization and Cardiovascular Interventions, Volume 60, Issue 4 , Pages 509 - 514, 2003