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INTRODUCTION

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The heart and its tributaries are encased in the thoracic skeleton composed of the manubrium, sternum, clavicles, rib cage, and vertebral bodies. This rigid chassis protects the heart, lungs, and great vessels. Trauma may result from penetrating or blunt mechanisms. The bony structures, interestingly, can also provide unique forms of injuries as they cause deflection of bullets, altering vectors of the original direction of penetration or by secondary fragments. Blunt forces can lead to crushing, traction, or torsion injuries to the heart from deceleration. Penetrating trauma to the great vessels usually leads to immediate exsanguination or, through a pattern of injury similar to blunt trauma including pseudoaneurysm, partial transection with intimal flap, thrombosis, and propagation.

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HEART INJURY

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Incidence

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Penetrating cardiac trauma is a highly lethal injury, with relatively few victims surviving long enough to reach the hospital. In a series of 1198 patients with penetrating cardiac injuries in South Africa, only 6% of patients reached the hospital with any signs of life.1

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With improvements in organized emergency medical transport systems, up to 45% of those who sustain significant heart injury may reach the emergency department with signs of life. It is somewhat frustrating, however, to note the overall mortality for penetrating trauma has not changed significantly, even in the major trauma centers.2

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Blunt cardiac injuries have been reported less frequently than penetrating injuries. The actual incidence of blunt cardiac injury is unknown because of the diverse causes and classifications. Thoracic trauma is responsible for 25% of the deaths from vehicular accidents, of which 10–70% of this subgroup may have been the result of blunt cardiac rupture.3 There continues to be tremendous confusion as the term, “blunt cardiac injury/cardiac contusion” is applied to a wide spectrum of pathology.

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MECHANISM

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Penetrating Cardiac Injury

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Penetrating trauma is a common mechanism for cardiac injury, with the predominant etiologies being from firearms and knives (Table 26-1).4 The location of injury to the heart is associated with the location of injury on the chest wall. Because of an anterior-lateral location, the cardiac chambers at greatest risk for injury are the right and left ventricles. In a review of 711 patients with penetrating cardiac trauma, 54% sustained stab wounds, and 42% had gunshot wounds. The right ventricle was injured in 40% of the cases, the left ventricle in 40%, the right atrium in 24%, and the left atrium in 3%. The overall mortality was 47%. This series noted one-third of cardiac injuries involved multiple cardiac structures.4 More complicated intracardiac injuries involved the coronary arteries, the valvular apparatus, and intracardiac fistulas (such as ventricular septal defects). Only 2% of patients surviving the initial injury required reoperation for a residual defect. The majority of these repairs were performed on a semielective basis.4 Thus, the majority ...

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