Penetrating Injury to the Heart

The many factors affecting survival from penetrating injury to the heart include the weapon used, the size of the myocardial injury, the injured cardiac chamber, coronary artery damage, the presence of tamponade, associated injuries, and the time taken to reach the hospital. Every patient with penetrating chest injury anywhere near the heart and shock on admission should be considered as having a cardiac injury until proven otherwise. The converse is not true, since about one-third of patients who arrive in an ED alive and are subsequently proven to have a penetrating cardiac wound have near-normal vital signs.

With early aggressive resuscitation and surgery, up to one-third of patients arriving in a trauma center in extremis with a cardiac injury can be saved. In patients brought to the operating room with signs of life and a recordable blood pressure, the survival rate should exceed 70 percent for gunshot wounds and 85 percent for stab wounds.

Prognosis in penetrating cardiac injury correlates with cardiovascular status on presentation. Those patients who reach the ED with near-normal vital signs typically have good outcomes, while few who lose signs of life during transport or on arrival to the ED survive with intact neurologic function. Patients who have no signs of life "in the field" are not candidates for resuscitative efforts.

PATHOPHYSIOLOGY Penetrating wounds of the heart are usually rapidly fatal, generally because of massive hemorrhage; fewer than one-fourth of the patients with this injury reach the hospital alive. Patients surviving more than 15 to 30 min usually have either a small wound or some component of pericardial tamponade. In a sense, pericardial tamponade is a two-edged sword; although it may prolong life by reducing the initial blood loss, the tamponade itself can be fatal by interfering with diastolic filling of the heart.

DIAGNOSIS Clinical Features All patients in shock with a penetrating wound of the chest between the midclavicular line on the right and the anterior axillary line on the left should be considered to have a cardiac injury until proven otherwise. If the only problem is tamponade and the patient is not hypovolemic, Beck's triad may be present. This consists of distended neck veins, hypotension, and muffled heart tones. The last is the least reliable sign; even with a large acute pericardial tamponade, which seldom is more than 200 mL, the heart tones are usually fairly clear.

Since patients with penetrating heart wounds are usually hypotensive, the neck veins will generally not distend until the blood volume is at least partially restored. On the other hand, chest injuries can cause the patient to breathe abnormally or strain, thereby causing neck vein distention even in the absence of tamponade. Other causes of Beck's triad include tension pneumothorax, myocardial dysfunction, and systemic air embolism.

Tamponade may also cause two Kussmaul signs. One is increased distention of neck veins during inspiration and the other is pulsus paradoxus. Paradoxical pulse is characterized by a drop in systolic blood pressure of more than 10 to 15 mmHg during normal spontaneous inspiration. The amount of paradox may be increased by hypovolemia.

Invasive Monitoring While the obstruction to cardiac venous return is usually evident on physical examination and by the finding of distended neck veins, occasionally a central venous catheter may be required to confirm the elevated central venous pressure in the setting of hypoperfusion. Patients in extremis should undergo diagnostic pericardiocentesis in lieu of central venous pressure following insertion of a central venous catheter.

X-Rays The pericardium is noncompliant. Whereas an obviously globular cardiac silhouette may suggest tamponade as the cause of hypoperfusion, the converse is not true: most patients with tamponade have very ordinary-appearing cardiac silhouettes.

Electrocardiography Electrocardiography (ECG) changes following cardiac injury are usually nonspecific. ST-T wave changes may indicate pericardial irritation or may reflect associated ischemia or hypoxia.

Echocardiography Transthoracic echocardiography (TTE) performed by both emergency physicians and trauma surgeons has been shown to be successful in the detection of pericardial fluid.1 l9 and 20 Accordingly, TTE is now frequently used in penetrating chest trauma for the evaluation of potential cardiac tamponade. It has been shown that TTE performed in the ED results in more rapid diagnosis, faster time to surgical intervention, as well as improved survival and neurologic outcome. 19 The presence of a hemothorax may limit the ability of TTE to detect occult cardiac injuries; 21 however, there are methods to distinguish hemothorax from pericardial fluid by using different views.

Echocardiography can identify pericardial fluid and may help localize missile fragments in the pericardium. While TTE remains a mainstay of rapid assessment and diagnosis, emergency physicians practicing in trauma centers will periodically encounter critically ill patients for whom the diagnosis of cardiac injury must be excluded while a series of other injuries are being addressed. In experienced hands, transesophageal echocardiography (TEE) is an efficient diagnostic tool, particularly if the patient is already intubated and ventilated and the probe can be inserted quickly.

Pericardiocentesis ACCURACY There is an increasing tendency to avoid the use of pericardiocentesis as a diagnostic procedure in acutely injured patients with possible tamponade. In Demetriades' series, the incidence of false-negative pericardiocentesis was 80 percent and the incidence of false-positives was 33 percent. 13 In addition to its inaccuracy, attempts at pericardiocentesis may injure the heart or cause dangerous delays in needed surgery.

TECHNIQUE The paraxiphoid approach is commonly used. An 18-gauge, 10-cm spinal needle is attached to a stopcock and then to a 20-mL syringe. The pericardiocentesis should be done with continuous ECG monitoring if possible. The ECG monitoring is more sensitive if one attaches the V lead of the ECG to the metal pericardiocentesis needle using an insulated wire with alligator clips on both ends.

The needle is passed upward and backward at an angle of 45° for 4 to 5 cm and advanced slowly until the point seems to enter a cavity ( Fig 251-3). Most authors direct the needle toward the left scapula tip; however, directing the needle toward the right scapula is more likely to parallel the right border of the heart and is less likely to penetrate the right ventricle.

FIG. 251-3. The paraxiphoid technique for pericardiocentesis is usually performed with the needle directed toward the left shoulder or left scapula tip. However, if one aims toward the tip of the right scapula, the needle tends to go parallel to the lateral border of the right heart and is less apt to penetrate the coronary artery or myocardium. [From Wilson RF: Injury to the heart and great vessels, in Henning RS (ed): Critical Care Cardiology. New York: Churchill Livingstone, 1989, with permission.]

One should aspirate every 1 to 2 mm as the needle is advanced. One can insert a stylet or inject 0.5 to 1.0 mL of saline solution at intervals to be certain that the needle is not plugged. The needle is then carefully advanced until blood is obtained, cardiac pulsations are felt, or the ECG shows an abrupt change.

Generally, a large portion of the blood in the pericardial cavity is clotted. Consequently, one can usually remove only a few milliliters of blood without manipulating the needle. If 20 mL of blood can be drawn out easily and rapidly, it usually indicates that the blood is being aspirated from the right ventricle.

If an immediate thoracotomy is not possible in a patient with a positive pericardiocentesis, a plastic catheter (inserted over a needle or Seldinger wire) can be left in place for continuous drainage of intrapericardial blood until the cardiac wound can be surgically repaired.

COMPLICATIONS The pericardiocentesis needle can perforate the right ventricle as a coronary artery and cause tamponade as a consequence of the procedure itself. Dysrhythmias may also occur. A falsely negative pericardiocentesis may delay needed surgery.

Subxiphoid Pericardial Windows If the patient has been hemodynamically stable and echocardiography is either not available or equivocal, an alternative method for diagnosing pericardial tamponade is a subxiphoid pericardial window. Although this can occasionally be performed under local anesthesia in the ED in a cooperative patient, it is best done in the operating room under general anesthesia. If blood is found in the pericardium, the incision can be extended up as a median sternotomy to repair the cardiac wound.

TREATMENT Fluid Replacement It is essential that patients with penetrating wounds of the chest have two or more large intravenous lines in place, with at least one line in a leg vein in the event that the superior vena cava or one of its major branches is injured. It is particularly important to have an adequate or increased blood volume if hypovolemia or tamponade is present. If tamponade is present with an elevated central venous pressure, one should generally not be reluctant to administer further fluid and blood to improve venous return to the heart while moving the patient to an operating room.

Pericardiocentesis Pericardiocentesis can be both diagnostic and therapeutic. Patients who are in shock and may have a cardiac injury should have an emergency thoracotomy as soon as possible. If it is not possible to perform an emergency thoracotomy promptly, continuing pericardiocentesis to relieve the suspected tamponade should be attempted.

Removal of as little as 5 to 10 mL of blood from the pericardial sac may increase stroke volume by 25 to 50 percent, with a dramatic improvement in cardiac output and blood pressure. In patients who have small puncture wounds of the heart, pericardiocentesis may be curative, and thoracotomy may not be required as long as the vital signs remain stable for at least 24 to 48 h after the procedure.

Thoracotomy Occasionally, a highly selected, stable patient with a small penetrating cardiac injury, as by a needle or ice pick, may be successfully treated without surgery. However, all patients with hemodynamic instability and a suspected injury to the heart should have emergency thoracotomy.

INCISION For penetrating wounds over the precordium thought to involve the heart, an anterolateral thoracotomy is performed in the left fifth intercostal space, which is one interspace below the male nipple (Fig 2.5.1-4.). The incision should be as long as possible, extending from just lateral to the sternum to a point high in the axilla. In females, the breast is displaced upward, and the incision is made through the breast crease. The incision is extended through the intercostal muscle into the pleural cavity, with care taken not to injure the underlying lung or heart. A rib spreader is then inserted and opened widely so that two hands can fit inside the chest (Fig.251-5). Cutting the intercostal cartilages above and below the incision may help increase the exposure. Not infrequently the internal mammary vessels, which lie about 0.5 to 1.0 cm lateral to the sternum, are cut; if so, they must be clamped and tied or suture-ligated.

Cardiac Wound

FIG. 251-4. Emergency thoracotomy to treat a stab wound of the heart or to perform open cardiac massage is usually done through an anterolateral thoracotomy approach. The incision extends along the fifth intercostal space with the skin incision placed in the inframammary crease. It extends from just lateral to the sternum to the midaxillary line. (From Geller ER: Shock and Resuscitation. New York: McGraw-Hill, 1993, with permission.)

FIG. 251-5. If the descending thoracic aorta is to be cross-clamped, it is best done under direct vision. To accomplish this, the anterior thoracotomy must be large and the incision opened as widely as possible. The left lung is pulled up anteriorly as far as possible by an assistant standing at the right side of the table. The pleura and fascia anterior to the aorta are thin, but the tissue between the aorta and the vertebral column is often rather tough and must be incised to get around the aorta properly. A straight clamp is often easier to put around the aorta than a curved clamp and is less likely to rupture the intercostal vessels. (From Geller ER: Shock and Resuscitation. New York: McGraw-Hill, 1993, with permission.)

When the injury is to the right of the sternum, a right thoracotomy is initially performed to control any bleeding sites, but strong consideration should be given to extending the incision across the sternum as a bilateral thoracotomy so as to be able to also control the descending aorta and, if needed, massage the heart directly. The sternum can be divided with a rib cutter. A bilateral anterolateral thoracotomy allows wide exposure of both sides of the heart and the proximal great vessels. In patients with a cardiac arrest, there is usually minimal bleeding from the thoracotomy incision until the circulation is restored. However, once circulation is restored, incisional bleeding may become quite severe, especially from the internal mammary arteries, which should be suture-ligated.

In hemodynamically stable patients with penetrating anterior chest trauma, a midsternotomy provides superior exposure for the organs most apt to be injured. 22 They feel that an anterolateral or lateral thoracotomy should be reserved for hemodynamically unstable patients, or if posterior mediastinal injury is suspected or aortic cross-clamping is apt to be needed.

PERICARDIOTOMY Even when the pericardial sac is not distended with blood, it can be difficult to grasp the pericardium with a forceps. It may be necessary at times to "hook" the pericardium with one blade of a scissors and then grab it with a forceps or clamp. Another technique is to very carefully incise the pericardium near the apex of the heart with a small-bladed knife to produce a hole just big enough to allow the tip of one blade of a scissors. If a scalpel is used to open the pericardial sac, inadvertent injury to the underlying myocardium or left anterior descending coronary artery can easily occur.

The pericardial sac should then be opened from the diaphragm below to the great vessels above with a scissors in a longitudinal direction 1 to 2 cm anterior to the left (or right) phrenic nerve. If the pericardial sac is still tight around the heart, a transverse cut of the anterior pericardium just above the central diaphragm may greatly help with exposure. The liquid blood and clots in the pericardial sac should then be manually evacuated and cardiac massage initiated if needed.

CLAMPING THE DESCENDING AORTA The second maneuver in the patient with severe hypotension or a cardiac arrest is compression or clamping of the descending thoracic aorta to help improve coronary and cerebral arterial flow. Since more than 60 percent of the cardiac output goes through the descending thoracic aorta, cross-clamping of this vessel can increase blood flow to the coronary and cerebral arteries two- to threefold.

To expose the descending aorta, an assistant on the right side of the patient lifts the left lung anteriorly, almost out of the hemithorax, so that the aorta can be seen from the left side of the table. The pleura and fascia in front of the aorta are easily opened, but the tougher posterior tissue between the aorta and the vertebral bodies often has to be incised sharply.

After the aorta has been exposed, a finger or a vascular clamp can be hooked around it. In this way, clamping is performed under direct vision, and the chances of intercostal or esophageal injuries are reduced. To be sure that the clamp is applied properly, one should feel pulsations from the spontaneous heartbeat or cardiac massage above the clamp but none below. If a nasogastric tube is not in place and there is little or no blood pressure, it is possible that the esophagus was mistaken for the aorta. After the clamp is applied, the time is noted, and the left lung is allowed to drop back into the thorax.

CLAMPING INJURED LUNG If there is an obvious associated lung injury, it should be controlled with a vascular clamp or a lung clamp to prevent systemic air embolism and stop the bleeding and air leak until more definitive control can be accomplished. If there is a large central lung injury, one should put a clamp across the hilum. If the hilar clamp does not control the bleeding because the injury is too close to the heart, one may have to clamp the pulmonary vessels inside the pericardium.

EXAMINING THE HEART If the bleeding site(s) is (are) not obvious, one should first carefully examine the right ventricle and right atrium, which are the chambers most apt to be injured. If an injury is still not seen, the heart can be swung out laterally and anteriorly into the left hemithorax to allow better examination of the remainder of the heart. When examining the posterior heart, one should be very careful because lifting the heart straight up increases the possibility of entry of air into a left-sided or posterior cardiac perforation, and this could result in sudden fatal coronary or cerebral air embolism.

CONTROLLING CARDIAC WOUNDS Most atrial wounds can be controlled by the application of a Satinsky vascular clamp and then sewn with a running 3-0 or 4-0 polypropylene suture. Traditionally, wounds of the ventricles can generally be tamponaded by the operator's finger while pledgeted horizontal mattress sutures of 2-0 silk or Prolene are passed under the finger and tied by an assistant. However, given the uncontrolled setting and poor visualization, this procedure can only be considered of the highest risk for needle-stick injury and potential exposure to blood-borne infections. Thus, other techniques described below should be used. When a wound lies next to a major coronary artery, mattress sutures are placed beneath the artery so as to avoid ligation or compression of the vessel. Cardiac stapling can also be highly effective in the initial management of simple penetrating cardiac wounds.

For handling more difficult cardiac wounds, several other techniques are available. The insertion of a 5- or 30-mL balloon Foley catheter into a large or inaccessible

(posterior) defect may allow for control of hemorrhage until a purse-string suture can be applied around the hole. Use of such a catheter also allows one to infuse fluids very rapidly, directly into the heart.

Wide horizontal mattress sutures placed on either side of a large defect and pulled together can also be used to control hemorrhage until cardiopulmonary bypass can be instituted. If cardiopulmonary bypass is not readily available, occlusion of the superior vena cava and inferior vena cava by vascular tapes or clamps can allow quick repair of large defects without causing exsanguinating hemorrhage. Before restarting the heart, if the caval occlusion technique is used, all air is evacuated from the various cardiac chambers by allowing bleeding through the injury prior to tying the final suture and then inserting large needles into the apex of the right and left ventricles while the heart is cautiously massaged.

CARDIAC MASSAGE Once cardiorrhaphy had been completed, internal cardiac massage can be performed as needed by compressing the heart between the palms of two hands or between one palm and the sternum. Warm—preferably 40 to 42.2°C (104 to 108°F)—saline solution poured over the heart may help prevent ventricular fibrillation. If ventricular fibrillation occurs, defibrillation with internal paddles, starting at 20 to 40 W/s should be performed. Lidocaine (1 mg/kg), correction of severe acidosis or alkalosis, and intravenous infusions of 1 to 2 g of MgSO 4 may help prevent recurrent ventricular fibrillation.

AIR EMBOLISM If severe dysrhythmia or cardiac arrest develops during endotracheal intubation or while the chest is being opened, aspiration of the cardiac chambers for air should be performed immediately. Systemic air embolism is most frequently diagnosed by seeing air bubbles in the coronary arteries. This serious complication is seldom mentioned in the literature but is seen in about 20 percent of patients with penetrating truncal trauma who have a cardiac arrest in the ED after endotracheal intubation. Patients rarely survive this complication.

CONTINUED CARE Once the heart develops a satisfactory rhythm, the descending thoracic aorta is gradually declamped as infusions of fluid and blood are administered, with care taken to keep the systolic blood pressure above 90 to 100 mmHg. One should also avoid systolic blood pressures greater than 160 to 180 mmHg because they may tear open cardiac repairs, excessively dilate the left ventricle, and/or cause intracerebral bleeding. The use of vigorous inotropes, such as epinephrine, should be particularly avoided at this point, as they may cause sudden, severe hypertension and can also increase the risk of recurrent ventricular fibrillation.

After the cardiac wounds and all bleeding vessels are controlled and an adequate cardiac output has been obtained, all clot is washed out of the pericardial and pleural cavities. One must look closely to make sure that the internal mammary arteries are intact or carefully suture-ligated. If the heart is edematous or dilated, the pericardium can be left open. Occasionally, the sternum cannot even be closed. In such instances, the skin can usually be stapled. The sternum can then be closed after several days when the cardiac edema and dilatation have resolved.

CORONARY ARTERY INJURIES Ligation of the cut ends is the treatment of choice for lacerations of small coronary vessels. Torn proximal coronary arteries may also be ligated if there is no evidence of cardiovascular dysfunction. However, such patients must be observed closely. If a large proximal coronary artery laceration results in dysrhythmias, myocardial infarction, or impaired hemodynamic function, an aortocoronary revascularization with a saphenous vein graft should be performed under cardiopulmonary bypass.

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