Left pulmonary artery bullet embolism following a penetrating cardiac gunshot injury

Abstract

Introduction

Bullet emboli occur when bullets migrate from an entry point to an abnormal endpoint via blood vessels or bowel. Most result from low-velocity, small calibre civilian gunshots. Although rare, when it does occur, it commonly embolises to the arterial system. Many times, these are amenable to removal and recovery.

Case report

We present a case of a haemodynamically unstable polytrauma patient with a pulmonary artery projectile embolus following a penetrating trans-thoracic cardiac gunshot wound.

Conclusion

A brief overview of the literature regarding bullet emboli is provided in light of this unusual case, focusing specifically on thoracic bullet emboli. A high index of suspicion should be raised when the number of entry and exit wounds are incongruent, bullet location does not align with anticipated trajectory, or serial radiographs demonstrate missile migration. Radiological evaluation and bullet retrieval are dependent on haemodynamic stability of the patient.

African relevance

• •Bullet emboli occur when bullets migrate from an entry point to an abnormal endpoint via blood vessels or bowel.
• •A high index of suspicion is advised in patients who present with thoracic gunshot wounds where exit wound(s) are not identified.
• •Radiographic imaging is important in identifying bullet embolisation and planning management.
• •Haemodynamic instability should prompt urgent surgical exploration.

Introduction

Bullet embolus to the pulmonary artery was first reported by Moresten [1] in 1903. Most projectile emboli result from low-velocity, small calibre civilian gunshots. Reported survival following penetrating cardiac injury in the largest published series was 84% [2]. Mechanism of injury and physiological status on arrival were the most important determinants of outcome in those patients. Transthoracic cardiac gunshot wound with subsequent pulmonary arterial missile migration is rare. These patients often present with challenging, confusing clinical pictures [3].

Case report

A 33-year-old man presented to the Trauma Centre of Inkosi Albert Luthuli Central Hospital (IALCH) in South Africa, following multiple sunshot wounds to the right upper limb, chest, and flank. Examination revealed gunshot wounds in the following anatomical areas:

• •On the proximal right humerus, with an exit wound at the proximal antero-medial humerus;
• •In the mid-forearm, with a palpable bullet at the medial side of the right elbow joint;
• •In the right infra-scapular region, without a corresponding exit wound;
• •At the proximal antero-lateral right chest, and
• •The right posterior flank and right upper quadrant (RUQ) of the abdomen.

On arrival, the patient’s airway was self-maintained, and breathing was spontaneous. Bilateral air entry was generally good; only slightly reduced in the right lower zone. The trachea was noted to deviate to the right. He was pale and hypothermic, with an initial blood pressure of 176/135 mmHg and heart rate of 132 beats per minute. His Glasgow Come Scale was 13/15, and he was notably confused, anxious and mildly combative. Heart sounds were audible, with a normal S1 and S2 and no murmurs. His neck veins were mildly distended. The abdomen was not distended or peritonitic but was tender in the right upper quadrant. An initial urine dipstick was normal.

Resuscitation began with oxygen per mask, intravenous fluids, and urethral catheterisation. Prior to any radiological imaging, the patient became acutely hypoxic, followed by profound hypotension and acute abdominal distension. The patient was rapidly intubated. Central venous catheterisation was performed, a nasogastric tube inserted, and vasopressor support commenced. Imaging was deferred, and the patient was immediately transferred to the adjacent operating theatre. The time from admission to theatre was approximately 45 min.

During transfer to the operating theatre, the patient developed pulseless electrical activity. Cardiopulmonary resuscitation was performed for five minutes. The patient required high-dose vasopressor support but return of spontaneous circulation was achieved. Repeat examination revealed absent breath sounds on the right side and two litres of blood, which was drained via an intercostal drain. Haemorrhage was also noted from the anterior abdominal wound. In view of the extensive haemorrhage from the thoracic cavity, the surgeon proceeded to a right sided emergency thoracotomy. There was an extensive haemothorax, with transection of the right lower lobe bronchus, and the gunshot wound was observed at the junction of the superior vena cava and right atrium. The pericardium was opened, and the caval laceration sutured. Despite haemorrhage control, the patient suffered a further cardiac arrest. Resuscitation failed, and the patient died intra-operatively. Chest X-ray performed in the mortuary prior to post-mortem revealed a projectile in the peri-hilar region of the left lung. On opening the mediastinum, the caval suture was intact and a contusion was noted on the medial wall of the right atrium, but there was no perforation at that site in the chamber. Exploration of the proximal left pulmonary artery revealed a bullet occluding the lumen without any external wound. Abdominal exploration revealed through and through wounds of the inferior vena cava and ascending colon with faecal contamination.

Discussion

Bullet embolisation is a rare but serious complication of gunshot wounds [4]. There are three known types: arterial, venous, and paradoxical. An arterial embolus is more commonly observed compared to a venous embolus at a 4:1 ratio [5]. Paradoxical emboli, where the bullet crosses from the venous to the arterial system (or vice versa), are exceedingly rare.

When a bullet penetrates body tissue, apart from striking bone, it generally tends to follow a straight trajectory. As the bullet loses kinetic energy, it may traverse only one wall of a vessel or hollow viscus. The main factor affecting the migration of a bullet in the venous system includes the force of blood flow, missile size and velocity, gravity, body position, and respiratory movement [6]. In the index case, the missile initially penetrated the right arm, then entered the right hemi-thorax, passing through the pulmonary parenchyma and lower lobe bronchus before eventually perforating the superior vena cava and entering the right atrium. It then ricocheted off the medial right atrial wall and embolised via the right ventricle to the left pulmonary artery.

Missiles in a right sided cardiac chamber may either embolise to the pulmonary artery or become entrapped in the endocardial trabeculations, becoming encysted with fibrous tissue. Due to the cardiac wound, a retained missile in the heart manifests itself immediately; this presents clinically with tamponade and/or intra-thoracic haemorrhage [7]. The clinical presentation following missile embolus to the pulmonary artery ranges from asymptomatic to features such as chest pain, dyspnoea, and haemoptysis. The diagnosis of bullet embolisation should be suspected in a patient with no exit wound, and, on radiograph, no visible bullet in the area of injury [7]. Given the sequence of collapse in the index patient, which began with acute hypoxia, followed by extreme agitation, and then profound hypotension, the assumption is that the missile had penetrated the right atrium but had insufficient energy to perforate the medial wall (Fig. 1). The distended neck veins suggest tamponade without active haemorrhage. For a brief period, the bullet may have remained in the right heart but eventually embolised to the left pulmonary artery and completely occluded the lumen. In conjunction with a major lower airway injury to the right hemi-thorax, acute hypoxia ensued causing extreme agitation and hypertension of sufficient magnitude to blow off any clot that was controlling the caval injury. Profound haemorrhage and hypotension then followed.

Fig. 1.

Schematic diagram of bullet trajectory following gunshot wound to right chest.

A diagnosis of bullet embolisation should be based on three observations:

• •An incongruent number of gunshot wounds,
• •A radiograph localising a bullet outside of the anticipated trajectory, and/or
• •Serial radiographs demonstrating a moving foreign body.

These observations should raise suspicion of the trajectory and prompt further investigation [8]. Radiological evaluation should be guided by clinical presentation and physiological status. Modalities for imaging include plain chest radiography, computerised tomography (CT), and trans-thoracic and/or trans-oesophageal echocardiography [9].

The management options for bullet embolisation depend mainly on haemodynamic status [10]. The challenge is compounded when the patient develops haemorrhagic shock, as in the index patient. Haemodynamically stable patients allow for chest radiography and, where available, whole-body trauma CT angiography. This helps to confirm the bullet trajectory, exact location of the bullet(s), and site(s) of active bleeding. The index patient became acutely unstable and this precluded imaging. Such patients require urgent surgical exploration. The indications for emergency thoracotomy include massive bleeding with persistent blood loss, bronchial injury with a massive air leak, oesophageal injury, cardiac tamponade, great vessel injuries, and acute deterioration of the patient’s condition [5].

Survival to hospital following a cardiac gunshot wound is rare and removal of the bullet depends on a multitude of factors, including: the haemodynamic stability of the patient, bullet location, experience, expertise, and equipment available to the attending surgeon [11]. Indications for venous embolectomy remain controversial. Proponents advise bullet retrieval when the bullet is in the pulmonary artery or its branches, either by thoracotomy, median sternotomy or percutaneous catheterisation [5]. Over 65% of these patients are asymptomatic [12]. Missile extrication by invasive procedures carry inherent risk, exposing the patient to intervention-associated morbidities. As such, opponents of venous bullet embolectomy also advocate that cardiopulmonary bypass should be used with caution and simple cardiac injuries repaired where possible.

Conclusion

A high index of suspicion is advised in patients who present with thoracic gunshot wounds where exit wounds are not identified. Radiographic imaging is important in identifying bullet embolisation and planning management. Haemodynamic instability prompts surgical exploration. Successful management of these patients remains a challenge.

Dissemination of results

This case was presented at the local mortality and morbidity forum.

Author contribution

All authors substantially contributed to the conception and design of the work; case acquisition, drafting the work and revising it critically, and final approval of the version to be published. All authors agreed to be accountable for all aspects of the work.

Conflict of interest

TH is an editor of this journal, but was not involved in the editorial workflow of this paper. No further conflicts of interest were declared.

Appendix A. Supplementary data

The following are the Supplementary data to this article: