Case #1: Picking Penetrating Precordial Pathology.

The Patient

A 22 year old male was rushed into the resuscitation room in the late evening with two right-sided stab wounds to the chest, both of which had been sustained about two hours earlier. The exact nature of the weapon was unclear, but thought to have been some form of kitchen knife.

It was a busy Friday night in Resus and this new arrival took our last remaining Resus bed space. To look at, he didn't appear overtly unwell. En route with paramedics he had become hypoxic and on arrival had 15L/min O2 running via a non-rebreather mask, which was maintaining his SpO2 in the low-normal range. Importantly, he had remained haemodynamically stable, and his arrival HR was 100 with a BP of 102/75mmHg.

Anteriorly there was a small 1.5cm defect just adjacent to the right parasternal edge in the 5th intercostal space. Posteriorly there was a similarly small wound in the right paraspinal region at the level of T7. There was no active bubbling or sucking from either wound, and no significant external haemorrhage.

An EFAST was performed, which demonstrated a moderate pericardial effusion with no overt evidence of tamponade on a sub-xiphoid view. The remainder of the scan was negative. A brief video demonstrating this effusion on a slightly-off axis PLAX view can be seen below:

An arterial blood gas taken at the time revealed a pH of 7.35, pCO2 of 31, HCO3- of 17.1, BE of -8.5, and a lactate of 4.9.

Management

The patient was urgently consented and booked for an emergency sternotomy and repair. After pericardiotomy, a 1cm right ventricular defect was found and suture repaired with 3/0 Prolene. Intraoperative blood loss was approximately 600mL, and he required 3 units of PRBC while on table. The patient did well and was extubated the subsequent day.

Discussion

These wounds are very small - externally. This should highlight two important points - one, that the width of a wound is not in any way predictive of its depth, so these wounds should be underestimated at your peril, and two, that these wounds are often overlooked in an otherwise blood-smeared patient - highlighting the importance of a thorough primary and secondary survey which includes a conscientious inspection of the patient's posterior.

The anterior wound falls inside what we would traditionally think of as the "cardiac box".

But it is important to remember that the posterior wound could also cause cardiac injury. Our image of the "cardiac box" fails to fully appreciate the three-dimensional nature of the at-risk area, forgetting that in addition to a "precordium" anteriorly there is a corresponding "postcordium" posteriorly - not to mention the fact that many a cardiac injury has been caused by penetrating injury to the epigastrium. Some evidence would also suggest that this concept of the "box" ought only apply to stab wounds anyway, as the wound tracts from gunshot wounds are longer and take more convoluted paths - and so wounds occurring outside of the traditional "box" should not sufficiently reassure you that cardiac injury is not possible [1,2].

Regardless of their location, any penetrating chest wound should mandate careful inspection of the pericardial sac using point-of-care ultrasound, and this view should be prioritised ahead the other traditional EFAST views. If this view is unrevealing, don't shy away from expanding your search to other focused echocardiography views.

Our patient continued to have some semblance of haemodynamic stability (his shock index on arrival being almost exactly 1), even several hours after injury. This meant an expedited trip to theatre for a median sternotomy was possible, a surgical approach that allows good exposure of the heart and great vessels, but also would have allowed extension above and below into the neck or abdomen, should this have been necessary. Had he arrested in the context of his cardiac injury however, we would often default to a left anterolateral thoracotomy - the standard approach to resuscitative thoracotomy. However, injuries to the far right of the right ventricle, the right atrium, and other right hemithoracic structures can't be accessed from the left, and so penetrating injuries to the right-side of the chest like these often require a right-sided approach, either via extension across the sternum in the form of a clamshell or a simultaneous right anterolateral thoracotomy via a separate incision [3,4]. Note that a left anterolateral thoracotomy is usually still necessary, as aortic cross-clamping can't be performed from the right. This means you typically need a second operator.

Take Home Points

• Don’t be fooled by the size of a wound - the width of an injury is in no way predictive of the depth.

• The "precordium" isn't just the surface anatomy overlying the heart - it's a larger anatomical area than one might think and should be appreciated in three dimensions.

• Prioritise the sub-xiphoid view during EFAST when evaluating penetrating chest injury. This is the money shot. Supplement this with additional echocardiographic views if needed.

• Access to the right atrium and ventricle is much more difficult via a left anterolateral thoracotomy. You either need a sternotomy or a right-sided thoracotomy to adequately expose the defect. Had this patient arrested in resus, defaulting to the standard left anterolateral approach alone would have likely been futile. In penetrating right-sided chest injury, know this and plan accordingly.

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Dr Ryoko Kinukawa is an emergency medicine registrar completing her advanced training with the Australasian College of Emergency Medicine. She has previously worked at The Alfred Hospital's Emergency & Trauma Centre and Royal Darwin Hospital. As an ex-physiotherapist, she has a keen interest in sports medicine and trauma, and has plans to sub-specialise in paediatric emergency medicine.

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References

[1] Jhunjhunwala R, Mina MJ, Roger EI, et al. Reassessing the cardiac box: a comprehensive evaluation of the relationship between thoracic gunshot wounds and cardiac injury. J Trauma Acute Care Surg. 2017; 83(3):349-55.

[2] Karam BS, Pearl JS, McCormick A, et al. Death of the cardiac box in contemporary era of ultrasound for trauma [conference presentation]. ASC 2021 Convention, United States.

[3] Hirshberg A, Mattox KL. Top Knife: The Art & Craft of Trauma Surgery. TFM Publishing Ltd. 2005; p182.

[4] Eagleton A, Brown CVR. Emergency Department Thoracotomy. In: Velmahos GC, Degiannis E, Doll D, editors. Penetrating Trauma: A Practical Guide on Operative Technique and Peri-Operative Management, 2nd Ed. Springer. 2017; p81.