Dissection of the left main coronary artery after blunt thoracic trauma: Case report and literature review

The Eastern Association for the Surgery of Trauma (EAST) has published a practice management guideline for patients with suspected BCI. A review of the literature supporting these recommendations can be found in table 1. Each patient with suspected cardiac injury should have an EKG upon arrival (Level I) [1]. Abnormal admission EKG should likely be followed with cardiac monitoring for 24 hours or until hemodynamically stable. Patients with normal EKG and no symptoms or other injuries can be discharged after a brief period of observation. This recommendation is supported by a review by Christiansen that showed over 80% of patients who developed a clinically significant arrhythmia had EKG changes on the initial study, suggesting that intake EKG can be considered a reasonably discriminating screening exam [2].

Echocardiography should be reserved for patients who are hypotensive either on admission or during the initial observation period. It can be helpful in diagnosing apical thrombi, pericardial effusion and tamponade. Echocardiograms added little clinical information for patients who were normotensive. Radionuclide imaging studies are too sensitive and lack specificity in the setting of trauma, so are not helpful in the evaluation of blunt cardiac trauma.

The EAST guidelines recommend against following cardiac enzymes because they are not helpful in predicting complications from BCI [1]. A review by Biffl, et al evaluated the management of suspected cardiac injury at a Level-One trauma center in Denver. Screening creatinine phosphokinase or troponin levels were frequently elevated post-injury and did not correlate with clinically significant BCI [3]. They identified clinical risk factors for complications in BCI including age greater than 55, an abnormal EKG at admission, the absence of chest pain, a widened mediastinum on imaging, a head injury with a Glasgow coma score less than 8, and pelvic fractures. In both univariate and multivariate analysis, these factors were more predictive of complications from BCI than cardiac enzymes [3].

Guidelines are helpful in directing the evaluation when thoracic injuries are suspected. The recommendations from EAST support a limited evaluation for negative screening tests and asymptomatic patients. If the initial screening evaluation is positive the algorithm is redirected to evaluate more specific injury patterns. In our case, there was evidence of malperfusion of the myocardial tissue in the anterior distribution, so we integrated cardiac enzymes and angiography to diagnose the potential causes of ST segment changes on the initial EKG. Efficiently proceeding from a screening evaluation to a diagnostic evaluation allowed for rapid detection and treatment of the coronary dissection.

Many types of cardiac injuries have been described after blunt chest trauma. Arrhythmia, cardiac contusion, and acute myocardial infarction are among the more common injuries [4]. Older patients can have ischemia induced by hemorrhagic shock superimposed on underlying cardiac disease, rather than from direct cardiac injury. Less commonly encountered are coronary artery laceration, thrombosis, or intimal dissection [4]. Clinically the injuries can by asymptomatic, or may cause angina, hemodynamic instability, or commotio cordis, resulting in sudden death.

Coronary artery dissections are most common in the left anterior descending artery (76%), right coronary artery (12%) and the circumflex (6%) [5]. Very few cases have been reported from blunt trauma such as waterskiing [4], contact sports such as basketball [6] and football [5], and high-speed impact such as motorcycle[7, 8], or motor vehicle collisions [9‐12]. Dissection of the left main coronary artery is among the most rare sequela of blunt chest trauma. One trauma-related left main coronary dissection was reported 3 days after a head-on motor vehicle collision at only 15 mph [13]. Cases that have been reported in the literature are listed in table 2.

Other causes of dissection unrelated to trauma include spontaneous lesions and iatrogenic injuries from coronary angiography. Spontaneous dissections have a 4:1 predilection for women with 25-33% occurring during pregnancy or the peripartum period [14]. Spontaneous lesions are associated with three conditions: 1) pre-existing coronary artery disease; 2) hormonal factors, such as pregnancy or oral contraceptive use, as stated above [14‐16]; and 3) patients with tissue fragility disorders (e.g., Marfan's or Ehler-Danlos syndromes) [17]. Mortality with spontaneous dissection can be up to 70%, based on post-mortem studies after sudden cardiac death [17].

Iatrogenic injuries are rare, occurring in 3-6/10,000 angiograms. They are most commonly seen as RCA injuries, and can be due wire passage or balloon inflation [18].

The approach to treatment of coronary artery lesions is variable and depends upon the mechanism, the co-morbidities of the patient, and degree of hemodynamic stability. Conservative management includes anticoagulation and observation if they are hemodynamically stable with minimal injuries. Thrombolytics can be administered to dissolve clot associated with an intimal injury, but are contraindicated in multiply injured patients. Revascularization can be achieved with percutaneous techniques or coronary bypass, and timing is dependent upon the clinical scenario.

Advancements in percutaneous interventions have prompted some to attempt revascularization using this method. Lesions in the LAD and RCA are highly amenable to stent placement [23]. Surgical revascularization is the preferred therapy in coronary lesions with the following characteristics: 1) unprotected isolated LMCA disease, 2) contraindication to anti-platelet therapy including aspirin, heparin, and clopidogrel, 3) history of known coagulopathy or bleeding diathesis, or 4) pregnant women [23]. The need for subsequent anti-platelet therapy following stent placement to assure patency limits the utility of these approaches in the multiply injured blunt trauma patient. Some of these patients are already coagulopathic and the addition of these agents can destabilize clots in solid organs leading to life-threatening hemorrhage, or propagate an intracerebral hemorrhage with grave clinical consequences.

In our patient the decision to proceed to coronary bypass was likely due to two factors. Most importantly, the dissection involved the left main coronary artery, which is preferentially treated surgically [23]. Secondly, our patient had a contraindication to percutaneous techniques because of his risk of bleeding. Our approach is supported by a number of successful cases already reported. Korach, Smayra, and Boland all report cases of motor vehicle collisions with resultant LAD coronary dissection that were successfully treated with surgical revascularization [9, 10, 13]. Harada had a similar success story, but the dissection was the left main coronary artery [8]. Redondo reported a mortality in the case of a 45 year-old female diagnosed with a left coronary artery dissection after a motor vehicle collision [11]. Attempts to treat with angioplasty and heparinization were complicated by fatal intra-abdominal hemorrhage.

Coronary dissection after blunt chest trauma has been successfully treated with a more conservative approach. Hobelmann reported the case of a 32 year-old male who suffered an RCA dissection after being elbowed in the chest during basketball [6]. The lesion was successfully treated with eptifibitide, heparin and stents. A focal right coronary artery lesion can be successfully stented, similar to the treatment of lesions in coronary artery disease [23]. Also, the risk of bleeding associated with the use of anticoagulation and anti-platelet agents was lower due to the isolated nature of the trauma. Hazeleger reported an LAD dissection 2 months after a tackle in football which was successfully treated with a stent [5]. Once again, left anterior descending artery lesions respond well to stent placement [23]. Also, the time interval from injury to diagnosis significantly reduces the risk of bleeding from anticoagulation necessary when stents are utilized.