A 50-year-old woman with underlying ischaemic heart disease presents to the ED following a motor vehicle crash. Her car rear-ended a stationary car at 60 km per hour and she was unrestrained. She was found to have an isolated undisplaced fracture of the sternum on a contrast-enhanced chest CT. Her vital signs and the 12-lead ECG are normal.
The MOST appropriate management of this patient would be:
Answer: C: Traditionally, sternal fractures have been considered a marker of serious underlying injury. However, current evidence suggests that the incidence of associated cardiac arrhythmias requiring treatment is very low (1.5%) and mortality rate is <1%. Subsequently, sternal fractures are no longer considered to be markers of significant blunt myocardial injury. In the given scenario the most appropriate management is to observe the patient for 6 hours and to repeat ECG at that point. If vital signs and ECG are normal, pain control has been achieved and no other significant injuries are present, the patient can be considered for discharge.
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Regarding ECG and troponin testing in a patient suspected of having myocardial contusion due to blunt chest trauma, which ONE of the following statements is TRUE?
Answer: A: The pathological characteristics of myocardial contusion resembles that of acute myocardial infarction with associated myocardial haemorrhage and oedema, myocardial cell necrosis with subsequent healing with scar formation. More than 50% of patients will have small pericardial effusions but the underlying myocardial injury itself can be small. Although not accurately determined, a small proportion of patients with myocardial contusion may develop significant arrhythmias. Myocardial dysfunction including cardiogenic shock, delayed rupture of the myocardium and ventricular aneurysm formation are other rare complications.
However, definitive diagnosis of myocardial contusion in a trauma patient is difficult because there is no gold standard. Clinical features, ECG and cardiac biomarker findings in a suspected patient can be non-specific. As a result the main objective of investigating a suspected patient is to identify a low-risk patient who is less likely to develop complications, mainly life-threatening cardiac arrhythmias, therefore less likely to benefit from inpatient cardiac monitoring and further investigations. When both the 12-lead ECG and the serum troponin are normal, the negative predictive value for a myocardial contusion reaches 100% and therefore can be considered as adequate investigations for ‘ruling out’.
It is important to note that a normal ECG alone, without troponin results, does not exclude the risk of developing a clinically significant cardiac event. Although the right ventricle is more prone to contusion than other chambers of the heart because of its location, the right ventricular (RV) contusions may produce relatively little ECG abnormalities. There are no gold standard ECG abnormalities that will help in the diagnosis and sinus tachycardia and supraventricular and ventricular ectopics are the most common changes. Various degrees of AV block and atrial fibrillation may be seen. Ventricular tachycardia (VT) and ventricular fibrillation (VF) are the lifethreatening arrhythmias.
Myocardial cell necrosis in myocardial contusion releases troponin; however, this happens at a relatively low level when compared with acute myocardial infarction. The sensitivity of troponin as a lone test to detect blunt myocardial injury seems to be limited (12–23%). When troponin is elevated, in combination with ECG abnormalities, it indicates a high-risk patient. These patients should be cardiac monitored in an inpatient setting with further investigation with 2D echocardiography and serial ECGs and troponins until these test results return to normal levels.
Regarding stab wounds to the heart, which ONE of the following statements is TRUE?
Answer: B: The right ventricle is at greatest risk for injury from penetrating wounds, including stab wounds, because of its anterior location and the large surface area. Gunshot wounds may produce complex injury in the heart and therefore survival from stab wound is much better than that from a gunshot wound. The injury to the pericardium and the myocardium can seal spontaneously and this is more true for stab wounds than gunshot wounds due to its small and linear defect. Additionally, ventricular wounds seal better than atrial wounds because of the thicker ventricular muscle. If the pericardial injury is sealed before the myocardial injury, the continuing blood loss into the pericardial sac can cause a cardiac tamponade. The likelihood of occurrence of cardiac tamponade is higher with stab wounds than with gunshot wounds. If both myocardial and pericardial defects remain open, exsanguinating haemorrhage can occur into the pleural cavity creating a large haemothorax.
Which one of the following scenarios is the MOST appropriate indication for an ED thoracotomy?
Answer: B: Emergency department thoracotomy (EDT) is recommended for victims of penetrating chest trauma (stab wounds or gunshot wounds) who are unstable with witnessed signs of life in the ED at least upon arrival and subsequently deteriorated and arrested. Signs of life refer to any organized electrical activity on the cardiac monitor, a palpable pulse, a recordable BP, any respiratory effort, any purposeful movement or a reactive pupil. In general, penetration with sharp objects is associated with a better outcome than penetration resulting from gunshot wounds. Two-thirds of the patients with stab wounds who are transferred to the OT may survive neurologically intact. Patients with severe hypotension, but not in the immediate danger of cardiac arrest, will also require an emergency thoracotomy, but this is best performed immediately in OT.
The available evidence is less clear regarding the value of EDT for similar patients with blunt cardiac trauma. Patient outcome is relatively poor when EDT is done for blunt trauma – 2% survival in patients in shock and <1% survival with no vital signs. Conversely, the success of EDT approximates 35% in patients arriving in shock with a penetrating cardiac wound, and 15% for all penetrating wounds. Some undertake EDTs for patients with clear evidence of cardiac tamponade who are in similar situations to the above following blunt cardiac trauma. A FAST examination performed upon arrival may be helpful in this situation.
In the given scenarios, patient B is the most likely to benefit from an EDT. Even though he has no vital signs he still has organized cardiac activity. Patient D is most likely to benefit from emergency thoracotomy performed in theatre, rather than in the ED. Patients A and C suffered from significant blunt trauma and are unlikely to benefit from EDT.
Which ONE of the following is NOT an aim of ED resuscitative thoracotomy?
Answer: B: The primary objectives of EDT are to:
One of the main aims of EDT is to identify and stop bleeding from a cardiac wound. Once identified digital occlusion should be attempted. A Foley type catheter can be used to seal a large defect. Thereafter, the patient should be taken to theatre immediately for definitive repair. Temporary aortic cross-clamping can be done at the level of the descending thoracic aorta for either thoracic or abdominal sources of haemorrhage. This will decrease the effective circulating volume, cause a reduction in subdiaphragmatic blood loss in abdominal haemorrhage and redistribute blood volume to the myocardium and brain.
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