Walter E. McGregor

Mechanical analysis of midline sternotomy wound closure

OBJECTIVE Unstable median sternotomy closure can lead to postoperative morbidity. This study tests the hypothesis that separation of the sternotomy site occurs when physiologic forces act on the closure. METHODS Median sternotomy was performed in 4 human cadavers (2 male) and closed with 7 interrupted stainless steel wires. The chest wall was instrumented to apply 4 types of distracting force: (1) lateral, (2) anterior-posterior, (3) rostral-caudal, and (4) a simulated Valsalva force. Forces were applied in each direction and were limited to physiologic levels (< 400 N). Four sets of sonomicrometry crystals were placed equidistantly along the sternum to measure separation at the closure site. RESULTS Sternal separation occurred as a result of the wires cutting through the bone. Less force was needed to achieve 2.0-mm distraction in the lateral direction (220 +/- 40 N) than in the anterior-posterior (263 +/- 74 N) and rostral-caudal (325 +/- 30 N) directions. More separation occurred at the lower end of the sternum than the upper. During lateral distraction, xiphoid and manubrial displacement averaged 1.85 +/- 0.14 and 0.35 +/- 0.12 mm, respectively. Anterior-posterior distraction caused 1.99 +/- 0.04-mm xiphoid displacement and 0.26 +/- 0.12-mm manubrial displacement. During a simulated Valsalva force, more separation occurred in the lateral (2.14 +/- 0.11 mm) than in the anterior-posterior (0.46 +/- 0.29 mm) or rostral-caudal (0.25 +/- 0.15 mm) directions. CONCLUSIONS These data suggest that sternal dehiscence can occur under physiologic loads and that improved sternal stability may be readily achieved via mechanical reinforcement near the xiphoid. Closure techniques designed to minimize wire migration into the sternum should also be developed.

Validation of a bone analog model for studies of sternal closure.

BACKGROUND The incidence of serious sternal wound complications may be reduced with improvements in closure methods. Biomechanical testing of median sternotomy closures in cadavers has proven useful but is limited by availability, high cost, and wide variations in the material properties of the sterna. This study tests whether artificial sterna can be used to replace whole cadavers in sternal closure testing. METHODS Two common wire closure techniques were tested using both whole cadavers and artificial sternal models formed from bone analogue material. Sternal models were molded from polyurethane foam (20 lbs/ft3) to simulate the mechanical properties observed in human cadaveric sterna. The force vector previously identified as the most detrimental to sternal cohesion (lateral traction) was used to stress the closures. Separation of the incision site was measured at the manubrium, midsternum, and xiphoid and data were compared between cadaver and bench test groups. RESULTS Sternal separations recorded in cadavers were found to be similar to bench test results for both closure types. Data variability within test groups was found to be consistently lower using artificial sterna, where peak standard deviations for sternal motion averaged less than half that measured in cadavers. CONCLUSIONS Results suggest that anatomic sternal models formed from solid polyurethane foam can be used to approximate the biomechanical properties of cadaveric sterna and that reliable information regarding sternal closure stability can be secured through this means. Moreover, bench test data were shown to be less variable than cadaveric results, thus enhancing the power to detect small differences in sternal fixation stability.

Improvement of sternal closure stability with reinforced steel wires

BACKGROUND Sternal dehiscence occurs when steel wires pull through sternal bone. This study tests the hypothesis that closure stability can be improved by jacketing sternal wires with stainless steel coils, which distribute the force exerted on the bone over a larger area. METHODS Midline sternotomies were performed in 6 human cadavers (4 male). Two sternal closure techniques were tested: (1) approximation with six interrupted wires, and (2) the same closure technique reinforced with 3.0-mm-diameter stainless steel coils that jacket wires at the lateral and posterior aspects of the sternum. Intrathoracic pressure was increased with an inflatable rubber bladder placed beneath the anterior chest wall, and sternal separation was measured by means of sonomicrometry crystals. In each trial, intrathoracic pressure was increased until 2.0 mm of motion was detected. Differences in displacement pressures between groups were examined at 0.25-mm intervals using the paired Students t test. RESULTS The use of coil-reinforced closures produced significant improvement in sternal stability at all eight displacement levels examined (p < 0.03). Mean pressure required to cause displacement increased 140% (15.5 to 37.3 mm Hg) at 0.25 mm of separation, 103% (34.3 to 69.8 mm Hg) at 1.0 mm of separation, and 122% (46.8 to 103.8 mm Hg) at 2.0 mm of separation. CONCLUSIONS Reinforcement of sternal wires with stainless steel coils substantially improves stability of sternotomy closure in a human cadaver model.

Effect of a Flexible Ventricular Restraint Device on Cardiac Remodeling after Acute Myocardial Infarction

The effects of a flexible ventricular restraint device on left ventricular (LV) dilatation and hypertrophy after transmural infarction are examined in an ovine model. Left ventricular remodeling and dilatation occurs after extensive myocardial infarction. A flexible ventricular restraint made from a nitinol mesh was evaluated in adult female sheep (n = 14). Cardiac magnetic resonance imaging scans and hemodynamic measurements were completed before and 6 weeks after anterior myocardial infarction. Treatment animals (n = 7) received passive ventricular restraint concurrently with LV infarction; the others (n = 7) served as controls. Increases in LV end-diastolic volume index were significantly less in the restraint group than in controls (0.20 ± 0.41 vs 0.83 ± 0.50 ml/kg, p < 0.03). End-systolic volumes increased less in treatment animals (0.43 ± 0.28 vs 0.90 ± 0.38 ml/kg, p < 0.03). Control hearts showed an increase in LV mass after infraction, whereas LV mass decreased in restrained hearts (0.14 ± 0.19 vs −0.25 ± 0.36 g/kg, p < 0.03). Hemodynamic studies showed similar changes after infarction for the control and the device group. Gross and microscopic examination showed no device-induced epicardial injury. A flexible ventricular restraint device attenuated remodeling after acute myocardial infarction in sheep.

Salvage Peripheral Extracorporeal Membrane Oxygenation Using Cobe Revolution® Centrifugal Pump as a Bridge to Decision for Acute Refractory Cardiogenic Shock

Abstract  Objectives: Acute refractory cardiogenic shock with early multisystem organ failure has a poor outcome without mechanical circulatory support. We review our experience with emergent peripheral cardiopulmonary support as a bridge to decision in these patients. Methods: A retrospective review from January 2009 through December 2010 was conducted of 26 consecutive adult patients at a single institution with acute refractory cardiogenic shock who underwent salvage peripheral cardiopulmonary support. Results: There were 18 men and 8 women with a mean age of 54 years (range 18 to 76). Indications for support: acute myocardial infarction (n = 16), decompensated chronic heart failure (n = 2), refractory arrhythmic arrest (n = 3), acute valvular pathology (n = 4), and unknown (n = 1). Patients with primary postcardiotomy shock were excluded. Median duration of support was 3 days (range 1 to 14). Decisions included: withdraw of support (n = 4), recovery (n = 5), and bridge to a procedure (n = 17). The procedures were percutaneous coronary intervention (n = 4), left ventricular assist device (n = 9), heart transplantation (n = 1), and miscellaneous cardiac surgery (n = 3). Overall survival to discharge was 65%. In the recovery and bridge to a procedure group, 78% were discharged from the hospital and survival at three months was 72%. Conclusions: Salvage peripheral cardiopulmonary support is a useful tool to rapidly stabilize acute refractory cardiogenic shock permitting an assessment of neurologic and end‐organ viability. (J Card Surg 2012;27:521‐527)

Strategies and Outcomes of Cardiac Surgery in Jehovah's Witnesses

Abstract  Background: Jehovahs Witnesses (JW) are a Christian faith, with an estimated 1.1 million members in the United States, well recognized for their refusal of blood and blood products. JW may not be considered for cardiac surgery due to perceived higher risks of morbidity and mortality. This study reviews our contemporary strategies and experience with JW undergoing routine and complex cardiac surgery. Methods: From November 2001 to April 2010, 40 JW were referred for cardiac surgery at a single quaternary referral institution. A retrospective analysis of demographic data, perioperative management, and clinical outcomes was examined. Published validated clinical risk calculator and model for prediction of transfusion were used to identify high‐risk patients (risk of mortality >6% or probability of transfusion >0.80). Results: The mean age was 70 (± 9.5) years with 21 men and 19 women. Patients were classified as high risk (45%, n = 18) and low risk (55%, n = 22) with demographics and comorbidities listed in Table 2. Operative procedures included: isolated coronary artery bypass grafting (CABG) (n = 19), isolated valve replacement/repair (n = 7), valve/CABG (n = 7), reoperative valve replacement (n = 4), reoperative CABG (n = 2), valve/ascending aorta replacement (n = 1), and CABG/ascending aorta replacement (n = 1). All JW were evaluated by The Department of Bloodless Medicine to individually define acceptable blood management strategies. The mean preoperative hemoglobin was 14.1 g/dL (±1.6). Overall mortality was 5% (n = 2) all of which were in the high‐risk group. Discussion: Using a multidisciplinary approach to blood management, JW can safely undergo routine and complex cardiac surgery with minimal morbidity and mortality. (J Card Surg 2011;26:135‐143)

Preoperative clinical factors are important determinants of the inflammatory state before and after heart surgery.

Postoperative inflammatory response is common in heart surgery patients, but less is known about variation in the baseline inflammatory state. This study characterizes the preoperative inflammatory profile in a group of high- and low-risk patients (n = 32; male 16, female 16; mean age, 70.3 ± 1.8) and relates this to postoperative events. Interleukin-6 (IL-6), tumor necrosis factor (TNF)-alpha, TNF receptors (R1 and R2), and high-sensitivity C-reactive protein were measured before surgery and 4 hours after arrival in the intensive care unit. Considerable variability existed in all preoperative inflammatory mediators before surgery. Patients with an elevated baseline IL-6 level, (IL-6 >10 pg/mL) were older (73.5 ± 2.2 vs. 67.9 ± 2.6 years), had a lower ejection fraction (34 ± 3.8% vs. 44 ± 2.9%), a higher predicted risk score (10.3 ± 1.2 vs. 5.9 ± 1.1), and a higher baseline high-sensitivity C-reactive protein (65 ± 10 vs. 24 ± 6 mg/L), p < 0.05 for all. These patients had high morbidity and mortality rates after surgery. In addition, patients judged to be at high risk on clinical criteria were found to have consistent elevations in the baseline inflammatory state. All patients had a surge in inflammatory mediators after surgery, but those who started at a higher baseline reached a higher postoperative level than the others (IL-6 2023 ± 561 vs. 361 ± 47 pg/mL, p < 0.05). Many heart surgery patients, especially higher-risk patients, have a significant inflammatory state before surgery. These patients are at risk for high morbidity and mortality rates after surgery.

Impending cardiac herniation following robotic mitral valve repair: A case report and review of the literature.

From the Departments of Cardiac Surgery Critical Care and Medicine, Temple University School of Medicine; and Departments of Cardiothoracic and Vascular Surgery and Anesthesiology, and Pulmonary Hypertension Program, Section of Heart Failure/Transplant/MCS & Pulmonary Hypertension; and Thoracic Surgery Residency Program, Allegheny General Hospital, Pittsburgh, Pa. Disclosures: Authors have nothing to disclose with regard to commercial support. Received for publication Jan 26, 2016; revisions received April 26, 2016; accepted for publication May 5, 2016; available ahead of print July 2, 2016. Address for reprints: Walter E. McGregor, MD, Thoracic Surgery Residency Program, Department of Cardiothoracic and Vascular Surgery, Allegheny General Hospital, Pittsburgh, PA 15212 (E-mail: wmcgrego@wpahs. org). J Thorac Cardiovasc Surg 2016;152:e79-82 0022-5223/

Combined carotid endarterectomy and transcatheter aortic valve replacement: Technique and outcomes

36.00 Copyright 2016 by The American Association for Thoracic Surgery http://dx.doi.org/10.1016/j.jtcvs.2016.05.037 Cardiac herniation before bedside maneuvers.

Left atrial appendage myxofibrosarcoma: A rare masquerader of myxoma and thrombus-“all that glitters is not gold”

Stroke and transient ischemic attack after transcatheter aortic valve replacement results in significantly higher morbidity and mortality. Severe carotid artery disease may be a contributing factor to this increased risk. We report our technique and outcomes of combined carotid endarterectomy (CEA) with transcatheter aortic valve replacement (TAVR).