The body is a complex and marvellous thing. In the words of Nathanael West (1903-1940):
"Under the skin of man is a wondrous jungle where veins like lush tropical growths hang along over-ripe organs and weed-like entrails writhe in squirming tangles of red and yellow".
These florid and floral lines are from the novel Miss Lonelyhearts (published in 1933). This novel is about a man who works at a New York newspaper as an advice columnist to despairing readers, writing under the name "Miss Lonelyhearts."
In our day to day work in the Emergency Department (ED) we view the impact of disease or trauma on the inner world described by West through test results and images (supplemented by smart phone photographs and YouTube videos and blogs). This monochrome view of trauma is in marked contrast with the coloured anatomical illustration from the mid 15th century shown in Figure 1.
This illustration, from a English medical treatise, shows the outer as well as the inner structure of a "wounded man" who has been stabbed, bitten, wounded by arrows, as well as bludgeoned in the arm and head. The drawing has a certain naive charm; it shows different causes of trauma and shows the different parts of the body that can be injured. It is a good summary, from nearly 700 years ago, of the "How" and "Where" aspects of trauma. It also shows that injuries can be blunt or penetrating. The heart is the only inner organ to be highlighted - the round blue object on the figure's head is a hat and not a brain injury.
A major difference between the 15th Century and our view of trauma is that we have a much better understanding of the "Where" and "What happens" aspects i.e. the location of injury, the process of damage and the consequences of injury. However some injuries are very uncommon, and our knowledge of them will nearly always be derived, based on reading books or review articles or using internet-based resources. These are an example of the "I believe it but I will never see it" situation.
Other injuries are well defined pathological entities but are difficult to diagnose at the bedside because there are no "gold standard" diagnostic criteria, or the clinical features are non-specific. This is the "I believe it but I haven't seen it yet" situation. A good example of this is blunt cardiac injury: myocardial contusions are found in about 20 percent of immediate fatalities from blunt trauma, so we can speculate that cardiac contusions should/may be present in (perhaps) one in fifty persons with significant thoracic trauma or severe multiple injuries or both. The following case shows that sometimes seeing confirms believing.
This 20 year old man driver of a car was involved in a high speed collision with another car. He sustained blunt trauma to the front of his chest and injured his right wrist. On arrival his heart rate was 100 beats per minute, blood pressure was 130/80 mm Hg, respiratory rate was 20 breaths per minute and his oxygen saturation (pulse oximetry) was 96 percent on room air. His trachea was midline, his jugular venous pulse was obscured by a cervical collar and his sternum was very tender. Auscultation of the heart and lungs was normal. Bedside ultrasound examination (FAST) of the heart and abdomen was normal.
His initial investigations included:
- Chest X-ray (CXR) and X-ray of the right wrist (Figure 2)
- Computed axial tomography (CT) scans of his brain, cervical spine, chest (Figure 3) and abdomen. The CT scans of his brain and, spine and abdomen were normal.
- Blood tests (Figure 4)
The patient's initial electro-cardiographs are shown in Figures 5 to 9.
Subsequent ECGs are shown in Figure 6 to Figure 9
An echocardiogram the day after admission was normal (Figure 10)
Diagnosis: Acceleration-deceleration blunt trauma resulting in a fractured manubrium, lung contusions and a cardiac contusion.
Blunt chest injury (BCI) can have no obvious effect on the heart but may cause one or more of the following:
- Acute myocardial rupture (with haemopericardium)
- Valve rupture - autopsy studies indicate that the aortic valve is most commonly involved, followed by the mitral and then tricuspid
- Coronary artery thrombosis or dissection
- Cardiac arrhythmias of all kinds
- Cardiac contusion - this implies an area or area(s) of oedema or haemorrhage or necrosis within the myocardium. Cardiac contusions can cause arrhythmias, bundle branch block (usually right bundle branch block), decreased cardiac contractility (that may be visible as wall motion abnormalities on echocardiography) or localised bleeding that could produce a haemopericardium). In autopsy series of patients who died from blunt trauma, myocardial contusions have been found in 14–24% of patients, although these patients also had multiple other injuries that contributed to or were the cause of death.
- Cardiogenic shock or rapid death secondary to one or more of the above complications
The gold standard test of cardiac contusion is autopsy or histological examination or both. The bedside diagnosis of cardiac contusion is difficult, as there are no non-invasive tests that are equivalent to the pathology findings. Patients with contusions may have ECG changes and/or elevated serum troponin troponin levels on arrival, but these tests are prone to false positive results due to neurologic injury or a catecholamine surge. Echocardiography is a more specific test, but its sensitivity is lower than ECG or troponin tests. Echocardiography is often difficult in BCI because of rib fractures, dressings, and the presence of pneumothoraces.
Haemodynamic instability in trauma is usually due to bleeding, but if ultrasound shows poor contractility, then this may be due to cardiac contusion. More commonly, however, ECG and/or wall motion abnormalities on echocardiography are due to pre-existing disease. In difficult cases of BCI where the causes of arrhythmia or shock are unknown or where echocardiography is indeterminate or limited, cardiac CT or MRI may have a role.
In this case:
- The patient presented with right bundle branch block on his initial ECG. The right bundle branch block pattern had disappeared within 9 hours.
- There was subtle ST elevation and T wave inversion in the precordial leads - this is not a feature of uncomplicated right bundle branch block. They indicate myocardial injury. These changes also disappeared within 9 hours.
- Electrical alternans was present in the initial ECG, but was not seen in the following ECGs. This finding can accompany pericardial effusion, but pericardial fluid was not seen on the initial bedside echocardiogram study.
- The serum troponin level was increased at presentation, had increased at 9 hours after arrival, and was decreasing 14 hours after arrival.
- A formal echocardiogram study 24 hours after arrival was normal.
These ECG and serum troponin findings are highly suggestive of myocardial contusion. The normal echocardiogram does not rule out this diagnosis. Although this patient had a sternal fracture, the great majority of persons with a sternal fracture do not have a cardiac contusion.
- "I believe it but I haven't seen it" is a variation of the famous comment "I see it but I don't believe it" attributed to the mathematician Georg Cantor (1845-1918). Cantor studied at the University of Berlin, where the mathematics department was probably the best in the world. His doctoral thesis was on the number theory of quadratic forms.
Mathematicians love to tell each other stories. One of their favourites is the story that Cantor was so surprised when he discovered one of his theorems that he said “I see it, but I don’t believe it!” Sometimes we might have a proof, and therefore know that something is true, but nevertheless still find it hard to believe.
- Does this patient need any specific follow up advice? Dr Smith's ECG blog (July 22nd 2012) described a 6 year old girl who was involved in a motor vehicle accident that resulted in a closed head injury, an orthopaedic injury (not specified) and an initial ECG that showed a right bundle branch block with ST elevation in Lead V3 and Lead aVL (and possible subtle ST depression in the inferior leads). A CT of the head, neck, chest, abdomen and pelvis was normal. She was observed initially in ICU. No further tests (ECG, troponin, or echocardiogram) were done because she was asymptomatic, and had a normal rhythm and rate. Three weeks later, shortly after bouncing on a trampoline, she collapsed and was found to be in electromechanical dissociation. A 2 mm hole was found in the left ventricle, with a large area of surrounding thinned and necrotic muscle. The patient could not be resuscitated.
The ECG changes in the case described by Dr Smith were more extensive than the ones in this case. Serial investigations in the case above showed resolution of the ECG changes, a troponin level that peaked and then was falling, and a normal echocardiogram study. While there is no evidence basis for the following recommendations, it would be prudent to repeat the echocardiogram study one month after discharge, and to avoid strenuous exercise until the second echocardiogram has been completed.
Dua A, McMaster J, Desai PJ et al. The association between blunt cardiac injury and isolated sternal fracture. Cardiology Research and Practice 2014, Article ID 629687 http://dx.doi.org/10.1155/2014/629687