Preventing heart injury during negative pressure wound therapy in cardiac surgery: Assessment using real-time magnetic resonance imaging

Objective: Heart rupture is a devastating complication to negative pressure wound therapy in cardiac surgery. Also, reduced cardiac output during negative pressure wound therapy has been reported. The present study aimed to examine the effects of negative pressure wound therapy on the position of the heart in relation to the thoracic wall using magnetic resonance imaging in a porcine sternotomy wound model. Methods: Six pigs had median sternotomy followed by negative pressure wound therapy at -75, -125, and -175 mm Hg. Real-time magnetic resonance imaging movies (10 images/s) were acquired in a midventricular transverse plane or a midsagittal plane during the application of negative pressure wound therapy. Results: Similar finding were observed at all different negative pressures studied. Negative pressure wound therapy caused the heart to be displaced toward the thoracic wall, and in some cases, the right ventricular free wall bulged into the space between the sternal edges, and the sharp edges of the sternum jutted into and deformed the anterior surface of the right ventricular free wall. These events were not affected by the interposition of 4 layers of paraffin gauze dressing but were hindered by the placement of a rigid barrier between the anterior portion of the heart and the inside of the thoracic wall. Conclusion: The results show altered position of the heart in relation to the sternum during negative pressure wound therapy. This may explain 2 potentially hazardous events associated with negative pressure wound therapy, namely, risk for heart rupture and reduced cardiac output. Inserting a rigid barrier over the heart may be a protective measure that is clinically practicable.