Penetrating Cardiac Injuries
Penetrating injury to the heart must be suspected with any missile or knife wound to the thorax or upper abdomen. The mechanism of injury may be categorized as low, medium, or high velocity. Knife wounds are low velocity, shotgun injuries are medium velocity, and high-velocity injuries include bullet wounds caused by rifles and wounds resulting from military and civilian weapons. The amount of tissue damage is directly related to the amount of energy exchange between the penetrating object and the body part.4
Traumatic cardiac penetration injuries are highly lethal, at 70% to 80%. The anteriorly positioned right ventricle is most frequently injured, followed by the left ventricle, right atrium, and left atrium (Table 104–1).6 Other potentially injured structures include the interatrial or interventricular septum, coronary arteries, valves, subvalvular apparatus, and conduction system.7 Low-velocity injuries, such as stab wounds, produce damage commensurate to the structure penetrated and size of the defect. High-velocity missiles produce injury beyond the region of myocardial penetration secondary to concussive effects and are more frequently lethal.8,9,10,11
TABLE 104–1.Spectrum of Penetrating Cardiac Injury by Anatomic Location50 ||Download (.pdf) TABLE 104–1. Spectrum of Penetrating Cardiac Injury by Anatomic Location50
|Right ventricle ||43% |
|Left ventricle ||34% |
|Right atrium ||16% |
|Left atrium || 7% |
The primary manifestations of cardiac penetration are hemorrhage and tamponade. Valve or coronary injury may, of course, produce acute valvular incompetence or myocardial infarction. Stab victims often present with tamponade when clot and surrounding pericardial fat partially seal the pericardial defect. Injuries to the left ventricle more commonly result in overt hemorrhage. Patients presenting with tamponade may have a survival advantage, with mortality as low as 8% in experienced trauma centers.8 Early diagnosis is critical to survival, and this is only possible with a high index of suspicion, bearing in mind that patients with potentially fatal wounds can be stable at presentation. Echocardiography can confirm the diagnosis of cardiac injury, but the lack of an effusion does not disprove injury.12 The diagnostic gold standard, short of exploration, is a subxiphoid window.
Management of penetrating wounds to the heart depends on the stability of the patient. If the patient presents with a recent loss of vital signs or in a moribund state, a left anterior thoracotomy performed in the emergency department is potentially lifesaving. Emergent thoracotomy may salvage as many as 20% of unstable or pulseless patients who have isolated penetrating trauma to the heart, but results are less favorable with missile wounds.13,14 Most cardiac wounds can be repaired through a left thoracotomy. Additionally, the thoracic aorta can be compressed or clamped to improve cerebral and cardiac perfusion while volume is restored. More stable patients are transported to the operating room, where a median sternotomy is the preferred approach. A sternotomy allows adequate exposure of all cardiac structures and permits rapid institution of cardiopulmonary bypass when required. Most injuries are repaired with simple pledgeted sutures using finger control to stop bleeding once identified. Coronary artery injuries are common, and the surgeon must use his or her judgment regarding coronary artery bypass versus ligation. An effort should be made to bypass large epicardial vessels, whereas smaller terminal branches or side branches can be ligated. The principal objective is to relieve tamponade and stop life-threatening hemorrhage. Further procedures, once again, require individualized surgical judgment based on the severity of the lesion and the physiologic significance on echocardiogram.
The reported incidence of blunt cardiac trauma varies widely in the literature, but blunt injury is involved in up to 20% of all motor vehicle collision deaths.15 The Centers for Disease Control and Prevention estimates 30,000 cases of blunt cardiac injuries per year in the United States.16 Blunt cardiac injury results from either a rapid deceleration mechanism or a direct blow to the precordium; in all cases, blunt cardiac injury requires significant force, such as occurs in motor vehicle crashes, pedestrians struck by motor vehicles, falls from heights, and sports-related injuries. Severe sudden abdominal compression can acutely increase pressure and blood flow to the heart, resulting in right-sided rupture. The absence of a clear definition and rapid laboratory testing makes the diagnosis of blunt cardiac injury difficult.
Resulting injuries include cardiac contusion, valve disruption, atrial or ventricular septal defects, or frank cardiac rupture. These injuries vary by anatomic location (Table 104–2). Once again, because of its anterior position, the right ventricle is the chamber most frequently involved. Cardiac rupture is a common mechanism of death in blunt trauma, with survival after medical care being uncommon.15,17 In patients reaching medical care with vital signs, however, a reasonable survival rate can be expected if cardiac injury is promptly recognized and operated on.18 Those surviving cardiac rupture more frequently have injuries to the right heart.19 Myocardial contusion encompasses a spectrum of injuries. In its mildest form, cardiac contusion results in mild epicardial ecchymosis without functional significance. More severe contusion can cause muscular injury, dysfunction, and infarction. The true incidence of myocardial contusion following blunt trauma is difficult to discern. It is important to note that severe myocardial injury can occur with little evidence of external chest trauma.
TABLE 104–2.Spectrum of Blunt Cardiac Injury by Anatomy Location ||Download (.pdf) TABLE 104–2. Spectrum of Blunt Cardiac Injury by Anatomy Location
|Right atrium ||8%-65% |
|Right ventricle ||17%-32% |
|Left ventricle ||8%-15% |
|Left atrium ||0%-31% |
|Coronary artery || |
Left anterior descending artery most common
|Valve injury ||0%-5% |
Aortic valve most common
|Blunt pericardial rupture ||0%-3% |
A high index of suspicion along with careful evaluation of mechanism should accompany all trauma patients from these accident scenarios, as a majority of patients with blunt cardiac trauma are asymptomatic. Diagnostic testing including chest x-ray, electrocardiogram (ECG), Holter monitoring, cardiac markers, transthoracic and transesophageal echocardiography, and cardiac computed tomography (CT) and magnetic resonance imaging (MRI) may be needed to make the diagnosis.4 All patients who have a significant mechanism of injury should have a screening ECG. Findings suggestive of cardiac contusion include nonspecific ST- and T-wave changes. Arrhythmias such as atrial fibrillation, atrial flutter, and premature ventricular complexes are also common and are usually self-limiting. Ventricular tachycardia and fibrillation are uncommon in patients surviving to the hospital. With a normal ECG in an otherwise uninjured patient, the risk of complications is low. Serial cardiac enzyme measurements are nonspecific for the diagnosis of myocardial contusion in the blunt injury patient.20 In the patient who remains unstable or responds poorly to standard resuscitative efforts, echocardiography is indicated to look for regional wall-motion abnormalities or structural defects.
The American Association for the Surgery of Trauma Injury Scale for Cardiac Injuries is one way of quantifying the extent of injury (Table 104–3).
TABLE 104–3.American Association for the Surgery of Trauma Injury Scale: Cardiac Injuries ||Download (.pdf) TABLE 104–3. American Association for the Surgery of Trauma Injury Scale: Cardiac Injuries
Blunt cardiac injury with minor electrocardiographic abnormality (nonspecific ST- or T-wave changes, premature atrial or ventricular contractions, or persistent sinus tachycardia).
Blunt or penetrating pericardial wound without cardiac injury, tamponade, or cardiac herniation.
Blunt cardiac injury with heart block or ischemic changes without cardiac failure.
Penetrating tangential cardiac wound, up to but not extending through endocardium, without tamponade.
Blunt cardiac injury with sustained or multifocal ventricular contractions.
Blunt or penetrating cardiac injury with septal rupture, pulmonary or tricuspid incompetence, papillary muscle dysfunction, or distal coronary artery occlusion without cardiac failure.
Blunt pericardial laceration with cardiac herniation.
Blunt cardiac injury with cardiac failure.
Penetrating tangential myocardial wound, up to but not through endocardium, with tamponade.
Blunt or penetrating cardiac injury with septal rupture, pulmonary or tricuspid incompetence, papillary muscle dysfunction, or distal coronary artery occlusion producing cardiac failure.
Blunt or penetrating cardiac injury with aortic or mitral incompetence.
Blunt or penetrating cardiac injury of the right ventricle, right or left atrium.
Blunt or penetrating cardiac injury with proximal coronary artery occlusion.
Blunt or penetrating left ventricular perforation.
Stellate injuries, less than 50% tissue loss of the right ventricle, right or left atrium.
Blunt avulsion of the heart.
Penetrating wound producing more than 50% tissue loss of a chamber.
The management of myocardial contusion is often expectant, particularly in the patient who remains hemodynamically stable after treatment of concurrent injuries. Arrhythmias are treated with standard agents for rate control and suppression of ectopy as well as optimization of electrolytes. In patients with hemodynamic instability, definitive echocardiography should be obtained. In cases of severe ventricular dysfunction and low cardiac output, inotropic support is appropriate with perhaps less concern for extension of injury than with a primary ischemic event. If inotropic support does not produce satisfactory improvement, intra-aortic balloon counterpulsation should be considered.
Pericardial injury results from direct high-energy impact of acute increase in intra-abdominal pressure. The presence of absence of a sternal fracture is not diagnostic. The pericardium may rupture along the diagphragmatic or pleural surface parallel to the phrenic nerve, resulting in evisceration of the heart and/or torsion of the great vessels. Pneumopericardium, abnormal gas pattern, or displacement of the cardiac silhouette may be present. Emergency surgical intervention via sternotomy is mandatory.
Direct coronary artery injury may cause arterial thrombosis, resulting in myocardial infarction, post-myocardial infarction ventricular septal defect, cardiac failure, or malignant arrhythmias.
Valve injury following blunt trauma is uncommon. The aortic valve is most frequently involved and can result from commissural avulsion, leaflet tears, or aortic dissection, all resulting in acute aortic insufficiency.21,22 Isolated injury of the mitral valve is less common and most frequently involves rupture of the papillary muscle or chordal apparatus. Tricuspid valve injury is more commonly reported than mitral injury perhaps because the latter is frequently fatal. Figure 104–1 shows the two-dimensional transthoracic echocardiogram in a female patient who was kicked in the anterior chest wall by her horse.23 Tricuspid valve injury may become evident at a time remote from the injury as right heart failure develops.24,25,26
A 53-year-old woman was kicked by her horse, with the hoof striking her in the center of the chest. She developed severe chest pain. Cardiac auscultation was normal. Rib radiographs did not show any rib fractures, and chest x-ray showed clear lung fields and a normal cardiac silhouette. Electrocardiogram (12-lead) demonstrated sinus tachycardia with a minor right ventricular conduction delay and no ischemic changes. Troponin I was elevated. Two-dimensional echocardiogram demonstrated a partially flail septal leaflet of the tricuspid valve (white arrow). RA, right atrium; RV, right ventricle. Reproduced with permission from Morsli H, Weissman G, Cooper HA: Images in Cardiovascular Medicine. Blunt Cardiac Injury- A case report. Circulation. 2008 May 13;117(19):e333-e335.
Recently a case of traumatic left ventricular intramural dissection has been reported (Fig. 104–2).27
Traumatic left ventricular intramural dissection. A 30-year-old male sustained severe blunt chest injury from a hydraulic pipe thruster. He required high-dose vasopressors and inotropes. Transesophageal echocardiography (TEE) revealed a small pericardial effusion (panel A, top) and an extended intramural dissection (panels A-C) of the left ventricle involving the anterolateral papillary muscle and the apical and mid-segments of the anterior and lateral ventricular walls. An epicardial patch was placed over a severely thinned part of the anterolateral wall to prevent apical rupture. Reproduced with permission from Groves DS, Schmidt C: Traumatic left ventricular intramural dissection. Eur Heart J. 2010 Oct;31(20):2481.
Delayed Sequelae of Cardiac Injury
Patients sustaining significant blunt or penetrating cardiac injuries require long-term follow-up. Injuries may not be appreciated at the time of trauma. Possible late sequelae include evolving atrial or ventricular septal defects, progressive valvular incompetence, aortocardiac or aortopulmonary fistulas, coronary artery fistulas, ventricular aneurysms, and post-traumatic pericarditis.28,29,30,31