Right Ventricular Perforation From a Floating Rib Following Deep Sternal Wound Infection Debridement and Application of a Vacuum-Assisted Closure Device: A Case Report and Literature Review

Identifying patients at risk for cardiac rupture

For the reconstructive surgeon, it is important to know the full history of the patient and the time line of important medical and surgical events prior to debridement. Events such as recent myocardial infarction affecting the free wall of the right ventricle, bypass surgery, types of bypass grafts used, foreign material in the operative field, the onset of infection symptoms, and chronic RV dilatation are important to consider when assessing myocardial health. Cartier at al⁸ recognized that of 48 patients with postoperative mediastinitis, 7 of whom went on to develop RV rupture, obesity with a body mass index greater than 30 kg/m² and infection identification delay were risk factors that were statistically linked to the occurrence of RV rupture. In addition, Arbulu et al⁹ noted that weakness in myocardial wall from previous insult, such as an infarction, may cause avulsion trauma to the RV to occur more readily. Edwin⁹ emphasized that mechanical sternal trauma from an open or dehisced sternum, akin to a rip saw effect on the adjacent RV wall, can promote spontaneous rupture. Even armed with this information, Edwin¹⁰ goes on to warn that a very thin RV wall may rupture without any mechanical sternal contributions whatsoever. Assessing a patient's preoperative state will assist in operative planning and counseling of the patient on his or her unique risk factors that could contribute to rupture.

Intraoperative debridement and VAC application

In regard to intraoperative prevention of RV rupture, tenets of sternal wound debridement are straightforward. Arubul et al⁹ stress 3 key steps in initial operative management: (1) limit open packing and close with flaps as soon as possible based on clinical evaluation; (2) free adhesions between the anterior RV and sternal halves to prevent avulsion; and (3) sternal edges should be meticulously smoothed after debridement. In addition, the use of antimicrobial irrigation, such as betadine, Dakin's, and other antibiotics, intraoperatively may increase desiccation risk and further weaken the myocardial wall.⁹ While these steps were formulated for the “open” method of treatment, nevertheless their significance can be extrapolated to those patient treated with a negative pressure wound therapy. In a study by Gustafsson et al,¹¹ 40 patients with DSWI were treated with sternal-sparing debridement technique in conjunction with VAC therapy. All patients received sternal reconstruction without the use of muscle or omental flap surgery, highlighting a conservative and efficacious approach to sternal wound debridement.¹¹

When using conventional VAC therapy to temporize a sternal wound, placement of the polyurethane foam and vacuum setting must be taken into consideration. Two goals are kept in mind when applying the VAC. First, one must successfully cover the heart. Second, the sternum must be fixated. Protective covering, such as 3 to 4 layers of paraffin gauze sheets, such as Adaptic (Acelity, San Antonio, Tex), can be used to line the lungs, heart, and bypass grafts to prevent direct contact with the polyurethane foam. This reduces negative pressure from acting directly on the heart and prevents adherence between the sternum and the RV. The foam should then be placed in a 2-layer fashion, with the posterior piece at the level of the sternum and the anterior piece at the level of the skin.^5,11 It is the authors’ recommendation that VAC sponge selection can utilize the less adherent white foam for the posteriorly placed piece whereas the anterior piece can utilize either the standard black sponge or antimicrobial silver sponge. While no studies have confirmed the exact optimal negative pressure for VAC treatment of sternotomy wounds, Malmsjö et al¹² endorse the use of negative 75 to 125 mm Hg. These settings are used to mimic physiologic conditions of a normal chest cavity and to provide the most effective stability to the sternum. It is postulated that the use of intermittent negative pressure therapy is unsuitable for the treatment of sternal wounds.¹²

Recently, a series of articles from Malmsjö et al¹² has investigated the specific physiologic nature of RV rupture during VAC treatment. It is believed that rupture may be potentiated by repeated trauma from contact of the RV with sharp sternal edges. In their porcine model, as little as 50 mm Hg of pressure contact was sufficient to cause damage to the anterior surface of the heart.¹³ In light of this, Ingmansson and colleagues¹⁴ have developed a novel device used to protect the heart from the sternal edges, aptly named the HeartShield. This device consists of a T-shaped plastic form covered with foam and low-adherence wound contact layer. This system can be used in combination with conventional VAC therapy. Results from a small cohort of patient studies are promising.¹⁴

Protocols for patients with DSWI treated with VAC therapy

While, traditionally, the closure of sternal wounds after debridement has been based on clinical evaluation of granulation tissue, other parameters may be considered in regard to correct timing of the closure. The Lund University Hospital mediastinitis algorithm published by Sjögren et al¹⁵ reports successful delayed primary closure without the use of free tissue transfer in VAC patients. The algorithm advocates initial sternal-sparing debridement, gentle saline rinse, and application of continuous-suction VAC at negative 125 mm Hg. Vancomycin and imipenem are used for initial antibiotic treatment. After 2 to 4 days, C-reactive protein (CRP) levels are monitored. If the value is less than 70 mg/L, delayed primary closure, including sternal rewiring, is attempted. If the defect is large, soft-tissue flap surgery is employed. Antibiotics are continued for 6 weeks. If CRP values are greater than 70 mg/L, the VAC is removed in the OR, and the wound is recultured to guide antibiotic therapy and debrided. VAC therapy continues for another 2- to 4-day cycle, and CPR levels are reexamined to determine whether closure can occur.¹⁵ A comparison of 30-day mortality data demonstrates that the benefits of microbiological control with repeated debridement outweighed the risk of RV rupture in 176 patients treated for DSWI with VAC therapy.⁵

Postoperatively, abrupt changes in intrathoracic pressure should be avoided so as to decrease the risk of sheering forces. Efforts should be made to quell vigorous coughing and episodes of postoperative nausea and vomiting. The use of a postoperative soft corset/chest harness is strongly recommended, especially in obese patient or those at risk for postoperative coughing such as patients with chronic obstructive pulmonary disease.^5,15 If the patient remains intubated, close monitoring for signs that the patient is “fighting the ventilator” should be undertaken.⁹

While a properly placed VAC does facilitate early mobilization, communication between the surgeon and the nursing/physical therapy staff must be clear to delineate restrictions in motion. To date, there have been no reported accepted clinical guidelines for timing of mobilization in patients with unstable sternums following DSWI debridement. However, recently, Cahalin et al¹⁶ addressed revisions to historical sternal precautions in order to maximize benefits for optimal recovery while decreasing functional impairment in patients with a median sternotomy. For high-risk patients, such as those with unstable sternums, a sternal precaution algorithm was developed. For 2 to 4 weeks after surgery, the algorithm proposes that patients: (1) participate in no lifting, pushing, or pulling more than 10 lb; no shoulder abduction or flexion greater than 90° when the upper extremities are weighted; (2) participate in shoulder active range of motion in a “pain-free” range; (3) have no scapular retraction past neutral; (4) have limited active trunk flexion/rotation with movements from the supine to sitting positions; (5) have no use of upper extremities with sitting to standing; and (6) continue the use of a sternal splint/compression device to mitigate effects of coughing or Valsalva maneuvers.¹⁶ We caution that aggressive shoulder adduction and/or abduction should be avoided in the early postoperative period. Ideally, a patient should be monitored overnight with bed rest precautions and carefully evaluated by physical therapy in the first few days postoperatively for mobilization readiness.

Tenets of management after ventricular rupture

Notification should be immediately sent to the cardiovascular OR team and the cardiothoracic surgeon if a rupture is suspected. We advocate that all patients be typed and screened for blood products before undertaking any deep sternal wound debridement. Should rupture occur, the administration of intravenous fluids and blood products for immediate resuscitation should be initiated as soon as possible. In addition, the VAC appliance should be shut off to relieve further negative pressure on the myocardium and the appliance should be removed at the bedside with a senior surgeon present. Prior to VAC removal, functional wall or bedside suction should be set up and packing material such as sponges and gauze roll be readily available. Exploration of the wound and visualization of the source of bleeding can then be safely undertaken. Application of manual pressure to the tear site should be performed once identified. Once an OR is secured, the patient may require cardiopulmonary bypass for large ruptures.

As noted in the cardiac literature, there are multiple modalities for repair including suture repair with Dacron pledgets, pericardial patches, fascia lata, TachoComb sheets (equine collagen patch with human fibrinogen and human thrombin; CSL Behring, Tokyo, Japan), and Teflon felt patch with suture anchor or cyanoacrylate glue.^8,17 Discussion between the cardiovascular and reconstructive teams should include methods and feasibility of repair based on the appearance of native tissues. Consideration of flap closure at this time should be weighed heavily for further protection of the repair. Monitoring in the intensive care unit postoperatively is advocated for potential rebleeding.