Introduction

      Introduction Blunt trauma to the chest can result in a variety of cardiac injuries. If overlooked this can lead to major complications or death. Myocardial contusion, which is the most frequent of these injuries, has no specific diagnostic test. The presence of myocardial contusion therefore needs a high index of suspicion. Such contusive injuries usually result from high speed trauma and occur in about 16-76% of patients involved in motor vehicle crashes(1). Cardiac contusion is only one of a variety of cardiac injuries that can occur. Other injuries are myocardial rupture, pericardial tamponade, pericardial trauma, valve rupture and myocardial infarction. Myocardial contusion is the most frequent cardiac injury in about half of patients involved in motor vehicle accidents. The majority of such contusive injuries involve the right ventricle, reflecting its anterior position(2). We present a case that highlights the problems faced in the diagnosis and management of such injury .

Case Presentation

     An 18-year-old man with no significant past history presented to the emergency department with a history of blunt injury to the chest , abdomen and pelvis sustained in a motor vehicle accident 45 minutes previously. He was conscious but irritable, with severe pain in the right side of the chest and abdomen. Clinical examination revealed a pulse rate of 110/min, with all pulses present and a blood pressure of 100/70 mmHg. Neck veins were not distended. He was in respiratory distress with tachypnoea and a flail segment of the chest on the right side. A right sided pleural effusion was present and a short systolic murmur at the left parasternal edge was heard with a positive Carvallo`s sign. He also had a distended and tender abdomen. The electrocardiogram on admission revealed sinus rhythm, right axis deviation and ST segment elevation with T-wave inversion in leads V1 to V4 (which persisted for the next three days of admission and then gradually reverted to normal).

His radiographic evaluation revealed fractures of the 6th, 7th and 8th ribs on the right side, fracture of the pelvis and a right-sided pleural effusion. Cervical spine radiography and computed tomography of the brain were normal. Patient's blood gas analysis was normal initially. Later it showed hypoxemia and the patient became irritable for which he was sedated, paralysed, mechanically ventilated and monitored in the intensive care unit. Trans-thoracic echocardiography revealed mild dilation of the right ventricular cavity and marked hypokinesia of the anterior right ventricular wall.
There was no pericardial effusion, no valve rupture nor aortic dissection or rupture. Doppler evaluation revealed mild tricuspid regurgitation. There were no regional wall motion abnormalities of the left ventricle and the ejection fraction was normal.
 

 In the intensive care unit, intercostal tube drainage and a Foley's catheter were inserted. Both tubes drained frank blood. The patient was subjected to an urgent exploratory laparotomy, which revealed rupture of the urinary bladder and copula of the diaphragm. Both injuries were repaired.. Seventy-two hours after the operation the urine became clear and the chest expansion became adequate. However, he required large volumes of intravenous fluids to maintain his blood pressure. The serial cardiac marker assays revealed a marked elevation suggestive of myocardial injury (table 1).

The other blood investigations were normal. The patient was stabilised and extubated and on the 8th day was transferred to the general ward. The intercostal tube was removed on the 12th day of admission. During the hospital stay (22 days) the patient did not develop any cardiac arrhythmias. A pre-discharge multigated blood pool study on the 20th day revealed a right ventricular ejection fraction of 37%.

Discussion

     Discussion Our patient was confirmed to have a myocardial contusion. This terminology is used to describe a broad spectrum of injury. It denotes the presence of cellular damage, diagnosed either clinically or biochemically by the elevation of the creatine kinase MB fraction and troponin-I enzymes(2). Experimentally, the severity of myocardial contusion in animals varies with the intensity of impact, and damage of 50% or more of the left ventricle precludes extended survival(3,4). Large contusions are associated with evidence of both regional and global biventricular dysfunction(3,4). Our patient had elevated cardiac enzymes. The echo Doppler study revealed a markedly hypokinetic anterior right ventricular wall with dialated right ventricular cavity and mild tricuspid regurgitation with normal pulmonary artery pressure. These findings suggest a fairly large myocardial contusion.
 
   The differential diagnosis of myocardial contusion includes pericardial tamponade, coronary artery dissection (causing acute myocardial infarction) (1), cardiac rupture and interventricular septum rupture. Acute myocardial infarction secondary to blunt chest trauma is rare(5,6) and if it does occur it usually suggests coronary artery dissection, intraluminal thrombosis or coronary spasm(6). These uncommon abnormalities tend to resolve spontaneously over a period of weeks after injury(7).

 Diagnosis of severe contusion injury is facilitated by non-invasive imaging techniques, and cardiac enzyme estimation. In our patient, the electrocardiogram, the ST segment elevation in V1 -V4 and the ischaemic pattern of progressive T wave inversion followed by resolution was indicative of contusion. Diffuse, non-specific repolarisation abnormalities, however are more common in patients with blunt chest trauma. Studies suggest that an abnormal electrocardiogram is not as sensitive or specific as functional indicators, such as echocardiography or radio nuclide ventriculography(8,9,10).

Ectopics, particularly ventricular ectopy have been suggested to confirm the diagnosis of contusion. Studies of blunt chest trauma had frequently presented elevation of creatine kinase MB and troponin I level as a prima facie evidence of contusion(11,12),but this has been questioned (13,9,14,15).

Complications of myocardial contusion resemble those of myocardial infarction and include arrhythmias, cardiogenic shock, true or false aneurysm formation, rupture of free wall, interventricular septum or papillary muscle and intracavitary thrombus(2,16,17,18,19).

The management of patients who have haemodynamic instability is similar to that of patients with complicated myocardial infarction(16,20,21). Fortunately, our patient did not have any of these complications.

Conclusions

     Myocardial contusion should be considered in all case of significant blunt chest trauma. Therefore, these patients with blunt chest trauma require systemic monitoring of cardiac function to enable timely diagnosis and successful treatment. The following points emerge from the discussion of this case:

1) Hypotension in polytrauma can be multi-factorial. Right ventricular contusion can be a cause or contributory factor to hypotension in such cases.

 2) Right ventricular contusion can be fairly accurately diagnosed by imaging techniques like echocardiography, gated pool studies and cardiac enzyme assays.

3) Management of myocardial contusion is similar to myocardial infarction with the exception that anti-thrombotics are contraindicated, except when normal thrombosis is identified.

Competing interests None declared

Acknowledgement We are grateful to Dr. Suhail Doi for his critical comments on this manuscript.

References

1. Fang BR, Li CT. Acute Myocardial infarction following blunt chest trauma. Eur Heart J 1994; 15(5):705--7.
2. Kaye P, O'Sullivan I. Myocardial contusion: emergency investigation and diagnosis. Emerg Med J 2002; 19(1):8-10
3. Stein PD, et al. Response of the heart to nonpenetrating cardiac trauma. J Trauma 1982; 22(5):364-73.
4. Utley JR, et al. Cardiac output, coronary flow, ventricular fibrillation and survival following varying degrees of myocardial contusion. J Surg Res 1976; 20(6):539-43.
5. Masuda T, et al. Long-term follow-up of coronary artery dissection due to blunt chest trauma with spontaneous healing in a young woman. Intensive Care Med 1996; 22(5):450-2.
6. Vlay SC, et al. Delayed acute myocardial infarction after blunt chest trauma in a young woman. Am Heart J 1980; 100(6 Pt 1):907-16.
7. Grady AE, et al. Traumatic dissecting coronary arterial aneurysm with subsequent complete healing. Am J Cardiol 1985; 55(11):1424-5.
8. Dubrow TJ, et al. Myocardial contusion in the stable patient: what level of care is appropriate? Surgery 1989; 106(2):267-73; discussion 273-4.
9. Helling TS, et al. A prospective evaluation of 68 patients suffering blunt chest trauma for evidence of cardiac injury. J Trauma 1989; 29(7):961-5; discussion 965-6.
10. Mooney R, et al. Conventional and right precordial ECGs, creatine kinase, and radionuclide angiography in post-traumatic ventricular dysfunction. Ann Emerg Med 1988;
11. Beresky R, Klingler R, Peake J. Myocardial contusion: when does it have clinical significance? J Trauma 1988; 28(1):64-8.
12. Edouard AR, et al. Circulating cardiac troponin I in trauma patients without cardiac contusion. Intensive Care Med 1998; 24(6):569-73.
13. Fabian TC, et al. A prospective evaluation of myocardial contusion: correlation of significant arrhythmias and cardiac output with CPK-MB measurements. J Trauma 1991; 31(5):653-9; discus sion 659-60.
14. Keller KD, Shatney CH. Creatine phosphokinase-MB assays in patients with suspected myocardial contusion: diagnostic test or test of diagnosis? J Trauma 1988; 28(1):58-63.
15. Moront M, Lefrak EA, Akl BF. Traumatic rupture of the interventricular septum and tricuspid valve: case report. J Trauma 1991; 31(1):134-6.
16. King RM, et al. Cardiac contusion: a new diagnostic approach utilizing two-dimensional echocardiography. J Trauma 1983; 23(7):610-4.
17. McLean RF, et al. Significance of myocardial contusion following blunt chest trauma. J Trauma 1992; 33(2):240-3.
18. Symbas PN. Traumatic heart disease. Curr Probl Cardiol 1982; 7(3):3-35.
19. Tenzer ML. The spectrum of myocardial contusion: a review. J Trauma 1985; 25(7):620-7.
20. Shapiro MJ, et al. Cardiovascular evaluation in blunt thoracic trauma using transesophageal echocardiography (TEE). J Trauma 1991; 31(6):835-9; discussion 839-40.
21. Sutherland GR, et al. Hemodynamic adaptation to acute myocardial contusion complicating blunt chest injury. Am J Cardiol 1986; 57(4):291-7.

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