Cardiac injuries in blunt chest trauma
© Huguet et al; licensee BioMed Central Ltd. 2009
Received: 2 June 2009
Accepted: 17 September 2009
Published: 17 September 2009
Blunt chest traumas are a clinical challenge, both for diagnosis and treatment. The use of Cardiovascular Magnetic Resonance can play a major role in this setting. We present two cases: a 12-year-old boy and 45-year-old man. Late gadolinium enhancement imaging enabled visualization of myocardial damage resulting from the trauma.
Blunt chest traumas are a clinical challenge, both for diagnosis and treatment, since they are often associated with substantial cardiac injury . If not recognized and treated promptly, it may have severe, or even fatal, complications for the patient due to myocardial herniation . Myocardial contusion usually shows enzyme rises, electrocardiographic abnormalities and contractile dysfunction . Since these symptoms can be similar for acute peri-traumatic myocardial infarction, a correct diagnosis may be difficult. The use of Cardiovascular Magnetic Resonance (CMR) can play a major role in diagnosing the etiology of the cardiac abnormalities in this setting.
We present two cases where the use of CMR is illustrated for the diagnosis and understanding of cardiac injury. The first patient was a 12-year-old boy referred to our center after a blunt thoracic-abdominal trauma by a rollover vehicle accident at the age of six. Although he was initially asymptomatic, a subsequent tachycardia was noted. An echocardiogram, acquired two years after the trauma, revealed a left midventricular aneurysm with loss of myocardium affecting the septal and posteriorlateral walls.
The second patient was a 45-year-old man who suffered from a blunt chest trauma after precipitating into a trench in which he was buried by construction material and lost consciousness. His echocardiogram showed a ventricular-septal defect with a left to right shunt. The CMR was performed the day after the trauma.
Both patients underwent an CMR examination to estimate the severity of myocardial damage using a 1.5 T scanner (Signa CVi-HDx, GE Medical Systems, Waukesha, WS) with a dedicated cardiac coil. The protocol included balanced steady-state free precession gradient-echo images (CINE) and late gadolinium enhancement (LGE) inversion recovery images (after IV administration of 0.2 mmol/kg of gadopentate dimeglumine contrast).
The patterns of myocardial damage visible from these images are consistent with previously reported injury sites [3, 4]. In Figure 3, a possible mechanism is presented for explaining the observed rupture. We hypothesize that the sudden increase in intrathoracic pressure during trauma  causes the right ventricular pressure to rise and the cavity to expand. This fastly displaces the right ventricular free wall outward, stretching the moderator band and generating a point of high wall stress around its septal insertion. Additionally, the induced increase in left ventricular pressure closes the mitral valve and stretches the tendinous chords and papillary muscles, creating a higher wall stress around the insertion of the papillary muscles. The increased stress from the right ventricular moderator band and the chordal apparatus puts the connecting (helical) endocardial muscle fibres, which run along the septal, inferior and lateral wall, from apex towards the base (Figure 3 right), under extreme wall stress, resulting in fibre damage, as observed in patient 1.
Finally, the lack of LGE in the second patient might be due to either: the acute state of the injury or the strong loss of myocardium resulting in no-reflow . However, further investigation is required to establish the prevalence of this condition among patients.
CMR has the potential to distinguish acute infarction from myocardial contusion, since it allows for a three-dimensional evaluation of the myocardial injury caused by blunt chest trauma. The use of CINE images can depict motion abnormalities and myocardial rupture, while the pattern observed in LGE images can describe the extent of injury (helical pattern vs. coronary territory).
In summary, CMR imaging enables to visualize the typical pattern of myocardial damage resulting from a blunt chest trauma, thus enabling to make an accurate evaluation of the induced injuries. It can be used to differentiate myocardial contusion from a peri-traumatic myocardial infarction.
Written informed consent was obtained from the patients for publication of this case report and any accompanying images.
This work was partially funded by the Spanish Industrial and Technological Development Centre (CDTI) under the CENIT Programme (CDTEAM Project). We would like to thank Viviana Zimmerman for the help with the visualization of fibre directions.
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