Missile Embolism from Pulmonary Vein to Systemic Circulation: Case Report with Systematic Literature Review.

Missile embolism (ME) is a rare condition and was seen in 0.3% of gunshot wounds during the Vietnam War. It was first reported by Thomas Davis in 1834. ME occurs when a small caliber, slow velocity projectile penetrates a wall in the vasculature; loses its kinetic energy; and gets carried away along the bloodstream to occlude another vessel at a distant site. Civilian victims of low-velocity bullets account for 60% of such cases. ME can be arterial, venous, or paradoxical. Systemic arterial embolization accounts for 80% of published reports and occurs after the projectile penetrates the left chambers of heart, aorta, or very rarely pulmonary veins (PVs). There are only nine published reports of ME through PV till date. We report here, embolism of an air-gun pellet entering through the right thorax, into right PV, embolizing into right femoral artery, causing acute limb ischemia, in a young male. Emergency arteriotomy and removal of the embolic pellet saved the limb with good recovery. He did not require a thoracotomy. The clinical picture, radiological findings, operative details, and the management are presented and discussed with relevant literature. The purpose of this report is to highlight the unique presentation of ME through PV, as its management is different from other cases of arterial ME. Early diagnosis of the condition is imperative to prevent permanent ischemic damage of end organ and its sequelae. We present an analysis of all published reports of systemic ME through PV and also give our recommendations for its management.

INTRODUCTION

Missile embolism (ME) from gunshot injuries is rare and <200 cases have been reported till date.[1] Civilian low-caliber, low-velocity pellets account for 80% of cases of ME.[23]

ME is classified as arterial, venous, or paradoxical.[4567] Systemic arterial ME can occur when the missile enters through the left cardiac chambers, aorta, or pulmonary veins (PVs). The entry of a missile through PV is extremely rare with only nine published reports. We report here, embolism of an air gun pellet entering through the right thorax, through the right PV, into the right femoral artery causing acute limb ischemia in a young male. Emergency arteriotomy and removal of the embolic pellet saved the limb, and the patient had good recovery. The clinical picture, radiological findings, and the management are discussed along with relevant literature.

CASE REPORT

A 23-year-old male sustained multiple air gun pellet injuries to the right upper and lower limbs and right anterior chest and was brought to our hospital after 10 h. He complained of acute onset right lower limb pain with impaired sensation and inability to move the limb. On examination, he was hemodynamically stable with absent right lower limb pulses with features of acute ischemia.

There were 4 entry wounds of which 3 had accountable pellets on clinical and radiological evaluation. The fourth puncture wound was over the right anterior chest wall at the 6th intercostal space 1 cm lateral to mid-clavicular line without any exit wound or a clinically evident pellet nearby. The chest radiograph showed minimal right hemothorax, no pneumothorax, normal cardiac outline, and no pellet. Radiograph and ultrasound examination of the abdomen was normal.

Computed tomography (CT) of the thorax showed pellet trajectory [Figure 1] toward right hilum along with linear contusion of the right lower lobe and minimal right hemothorax with no visible pellet. Two-dimensional (2D) echocardiography showed normal functional parameters with no evidence of cardiac injury, hemopericardium, or congenital defect. All the pellets seen after radiological examination had corresponding entry wounds except for the pellet seen in the femoral area.

Figure 1

Coronal reconstruction of computed tomography thorax of the patient along with a line diagram showing bullet trajectory toward the right inferior pulmonary vein. (PV-Pulmonary vein)

At surgery, an intraluminal pellet was found in the right superficial femoral artery. Arteriotomy was done and the pellet was retrieved [Figure 2]. Complete thrombectomy with both forward and backward bleed was achieved with Fogarty catheter after which distal circulation was established. An intercostal tube was passed on the right side and about 350 mL of blood drained slowly. As the patient was hemodynamically stable, thoracotomy was deferred and planned only in case of any deterioration. He was heparinized postoperatively. The patient's intercostal drainage gradually decreased and the intercostal tube was removed on the 5th postoperative day after repeat CT thorax and 2D-echocardiography. At 1 month follow-up, the patient was doing well.

Figure 2

Intraoperative picture showing femoral arteriotomy (A) and extracted pellet (B)

DISCUSSION

ME is rare and was seen in 0.3% of 7500 cases of gunshot wounds during the Vietnam War; and 1.1% of 346 bullet injuries during the Afghanistan and Iraq wars.[4] Thomas Davis reported the first case of intravascular migration of a foreign body after a self-inflicted injury in 1834.[8]

To become an embolus, the missile should be of low-caliber and have just sufficient kinetic energy to come to rest in the lumen of the vessel; to be carried away in the blood stream to occlude a distant vessel.[9]

The clinical picture in a patient with ME is often confusing.[810] It should be suspected in a patient with gunshot injury when:

There is an entry wound without an exit wound

The missile is seen to lie away from the anticipated trajectory

A missile which is found to wander and lie in different positions during serial radiological investigations

There is loss of peripheral arterial pulsations with ischemic sequelae

A missile appears out of focus in the cardiac silhouette in a chest radiograph and

The missile appears in the central portion of the lung (within the pulmonary artery).[10]

ME is classified into (a) arterial, (b) venous, and (c) paradoxical.[4567] Systemic arterial ME occurs from penetration of the left cardiac chambers, aorta, PVs or after paradoxical entry to left chambers of the heart through atrial septal defect, ventricular septal defect, or a patent foramen ovale.[11] Migration of arterial missile is then determined mainly by the force of blood flow, anatomy of branches of aorta and to some extent, gravity.[512]

Systemic ME through the PV is extremely rare. Mattox et al.[10] reported a fairly large series of 28 cases of bullet embolism and also reviewed published reports of bullet embolism in 141 patients; and in none of them, the entry of the missile was through the PV. After the review of published literature till date, we have found only nine case reports Table 1 wherein the missile entered the PV resulting in systemic embolization.[3891314151617]

Table 1

Summary of all cases of systemic missile embolism through pulmonary vein

Authors	Findings
	Entry wound	Vessel affected by embolus	Clinical findings	Radiological findings	Surgical intervention and findings in thorax	Surgical intervention and findings at the embolic site	Clinical outcome
Schmidt 1885[5]	PV	Right femoral artery			No thoracotomy was done	No embolectomy was done	Expired
Burihan et al., 1980[13]	Left posterior chest wall to left PV	Right subclavian artery	Ischemia of right upper limb with absent distal pulses 24 h after injury	In X-ray chest bullet migrated from region of left atrium to right subclavian region	No thoracotomy was done	Arteriotomy and removal of bullet was done	Uneventful
Klitenick and Suarez 1982	Right chest wall to Right PV	Left profunda femoris artery	Developed right hemothorax. No features of left lower limb ischemia	Chest-X ray- right large hemothorax. Arteriography showed bullet in left profunda femoris artery	Thoracotomy - lung laceration stapled. Small hematoma toward the hilum was not explored	Bullet left in situ	Discharged with good outcome on the 5th day
Kerr and Louie 1993[9]	Left posterior chest to right PV	Right axillary artery	Absent pulses in right upper limb	Chest X-ray -Right hemopneumothorax and bullet in right infraclavicular area	Arteriography - obstruction of the 1st part of axillary artery. Thoracotomy -entry wound in the right lower lobe of the lung without exit wound	Surgical exploration showed intact artery with intraluminal bullet, which was removed	Discharged with good outcome after 7 days
Rajamani and Fisher 1998[14]	Right chest wall to right PV	Right ICA	Right-sided hemopneumothorax; Developed left hemiplegia 16 hours after admission with coma	CT brain - right cerebral infarct. Carotid angiography - complete occlusion of right ICA by the bullet	Hemopneumothorax present but the patient was hemodynamically stable	The bullet was surgically removed	Expired due to massive cerebral infarct. Autopsy showed finding of bullet entry into the right PV
Braun[15] (undated)	Chest to PV	Left common femoral artery	Ischemic left leg	Angiography - bullet in the left common femoral artery	No thoracotomy was done	The bullet was removed surgically	Discharged with good outcome
Duncan and Fourie 2002[16]	Anterior chest	Right ICA	Left hemiparesis	Chest X-ray -normal. CT of brain - right cerebral infarct. Angiogram - bullet in the right ICA	No thoracotomy was done	Bullet was left in situ	Good outcome with mild left hemiparesis
Ronsivalle et al., 2005[17]	Left chest wall to left PV	Right axillary artery	Absent distal pulses in right upper limb	CT of thorax - bullet tract from left chest wall to hilum. Bullet in right axillary artery on angiography	No thoracotomy was done	The bullet removed after arteriotomy	Discharged with good outcome
Ntlhe et al., 2008[3]	Anterior left chest to left PV	Right ICA	Dense left hemiplegia on the day after the injury	Chest X-ray was normal. Transesophageal echocardiography was normal	No thoracotomy was done as the patient was hemodynamically stable	Angiography after 2 months - right ICA bullet. Bullet removed after 7 months	Discharged with left hemiparesis
Present report	Right anterior chest wall to right PV	Right superficial femoral artery	Right lower limb ischemia	CT thorax- bullet tract toward right hilum, right hemothorax. 2D-Echocardiography normal	No thoracotomy was done	Bullet extracted from right superficial femoral artery through arteriotomy	Discharged with good outcome

PV: Pulmonary vein, ICA: Internal carotid artery, CT: Computed tomography, 2D: Two-dimensional

Embolism through PV can be surmised when:

In the presence of systemic ME, there is absence of clinical or radiological evidence of injury to cardia or aorta and

There is no significant intra-thoracic bleeding requiring surgical intervention.

Bleeding from PV is minimal or self-limiting as they are low-pressure channels,[18] and the low-caliber low-velocity bullet causes minimal local tissue injury during penetration through the elastic and/or muscular wall of the vessel.[2] Thoracotomy is therefore rarely indicated.

The right inferior PV has an almost transverse course along the intersegmental septum till just before it enters the pericardium, where it is almost vertical, and it opens anteriorly and inferiorly into the left atrium.[19] The CT thorax of our patient [Figure 1] showed the trajectory of the pellet corresponding to the right inferior PV. The course of the pellet in our patient was probably: right inferior PV, to the left atrium, to the left ventricle, and to the systemic circulation until it got lodged in the right femoral artery. In our patient, 2D-echocardiography did not suggest any injury to the heart or its valves, hemopericardium, or any congenital defects. If the pellet had entered the right heart chambers, the embolism would have been into the pulmonary circulation.

Arterial embolization accounts for 80% of ME and presents early due to ischemic symptoms.[420] Trimble's series showed that ME was three times more frequent in the lower limbs as compared to upper limbs. In Table 1, of 10 cases, 3 had upper limb involvement and 4 had lower limb involvement. ME is also reported three times more commonly in the left lower limb as compared to the right.[2521] This has been attributed to the less acute angle (30°) of aorta with left common iliac artery as compared to right common iliac artery (45°).[1121] However, in our review [Table 1], both the sides were equally involved (2 each). In upper limb, the right side is more commonly affected due to the large caliber of right brachiocephalic artery.[2] In our review [Table 1], the right upper limb was involved in three cases and right internal carotid artery (ICA) was involved in 3.

In addition to chest X-ray and CT of thorax, whole-body X-ray can help in locating the missing bullet.[10] Angiogram can further show the exact location of the bullet, aiding in surgical management.[210] Shannon et al. in their series, state that X-ray screening documented 86% of ME and was supplemented by arteriographic studies in 36%.[2]

It is generally believed that patients with arterial ME are at high risk for ischemic complications.[4] Hence, removal of the missile is considered mandatory.[22] However, sometimes, delayed embolectomy may result from delayed or nonrecognition of the embolic event.[2] In our review [Table 1], seven embolic missiles were removed and three left in situ (one expired without investigations, one left in profunda femoris as the perfusion of the limb was good and the last left in right ICA. Endovascular intervention for retrieval is not advocated for intra-arterial bullet as it may be adherent to intima of the artery.[3]

In our case review, only one patient underwent thoracotomy for an associated lung laceration and the site of ME into pulmonary vein did not require surgical intervention in any of the cases. Apart from the earliest patient reported by Schmidt who did not undergo any surgical intervention, only one other patient died due to massive cerebral infarct. Two other patients with ICA embolus recovered with mild left hemiparesis. All the other patients had good outcome.

CONCLUSION

ME through PV is to be suspected when there is no evidence of cardiac or aortic injury clinically or radiologically in the presence of systemic arterial embolism

If ME is suspected, all peripheral pulses have to be examined, and any evidence of peripheral ischemia should be noted. Whole-body X-ray supplemented with an arteriogram can localize the missile. CT scan of the thorax and 2Dechocardiogram are invaluable for complete assessment

Minimum-to-moderate hemothorax or pneumothorax may be present. However, exsanguinating bleed requiring thoracotomy is highly unusual

Early detection of arterial ME can prevent ischemic damage and other delayed complications, ensuring good outcome.

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Conflicts of interest

There are no conflicts of interest.