Traumatic blunt cardiac injuries: An updated narrative review.

Blunt cardiac injury (BCI) is defined as injuries sustained due to blunt trauma to the heart, and it remains unchanged for long time. The spectrum of BCI ranges from a minor "bruise" to specific postcontusion cardiac conditions such as free-wall rupture. This is a narrative review provides a continued and updates details regarding BCIs from 2008 to 2017. For this purpose, a narrative review of literature was conducted using appropriate database for retrieval of articles through systematic search methodology. Autopsy-based studies are very limited. It can be concluded that regardless of the variability in the spectrum of modalities and medical/surgical resources, BCIs diagnosis and management remain a puzzle and needs further prospective studies. Copyright:

INTRODUCTION

Blunt cardiac injury (BCI) refers to injury sustained due to blunt trauma to the heart which is more common than penetrating injuries.[1] Misdiagnosis and high mortality are major concerns in these injuries. The true incidence rate of BCIs varies greatly in the literature. The CDC estimated the incidence of BCI as 30,000 cases per year in the United States.[2] The definition of BCI has remained unchanged for a long time. In light of this, we conducted a narrative review of literature to provide a continued overview of the knowledge and updates regarding BCI in the last decade. A literature search using PubMed, Scopus, and Google scholar was conducted for the studies in human, published in English language, full texts available, and in the duration between 2008 and 2017. The literature search resulted in 90 articles; 52 were found to be of relative context to the topic with majority of them being case reports (n = 33), prospective studies (n = 2), retrospective studies (n = 11), and 3 articles, 1 narrative review, 1 analysis, 1 scientific standard. We excluded 38 of irrelevant context and pediatrics [Figure 1].

Figure 1

Study design

BLUNT CARDIAC INJURY

The incidence of cardiac injury following blunt chest trauma varies between 8% and 86%.[3] The main reported cause was high-speed vehicle collision, followed by falls from height or crushing incidents.[4] Damage to the myocardium falls within a wide range from asymptomatic to death based on the severity and mechanism of injury. Cardiac manifestations include arrhythmias, wall motion abnormalities, myocardial wall rupture, and valve damage. However, the most prevalent pathology is myocardial contusion.

Mechanism of injury

The common causes of BCI include motor vehicle accidents with impact at a speed >30 mph with deceleration sheering forces[1] or direct blow to the chest wall by airbag deployment, sports (e.g., contact sports), fall from heights, acts of violence, crush injuries, and blast trauma.

Commotio cordis

Commotio cordis is defined as sudden cardiac death triggered by a relatively innocent blow to the precordium over the left chest wall.[5] Collapse typically follows instantaneously or within a few seconds due to arrhythmias (typically ventricular fibrillation [VF]), making it one of the most common causes of sudden cardiac death in recreational and competitive sports.[5] Left ventricular pressure increases with the impact, leading the myocardial cell membrane to stretch and activating stretch-sensitive ion channels which ultimately induces VF by increasing the dispersion of repolarization. To induce VF, the impact must occur within a narrow window before the T-wave peak on the electrocardiogram.[4]

Commotio cordis is a distinct form of cardiac contusion, in which structural damage to the heart with resultant arrhythmias develops within 24 h after severe chest impact. It warrants a crucial need for observation-monitoring and close follow-up to identify the need for intervention. Many case reports demonstrated that resuscitation efforts are effective if immediately performed.[67]

Commotio cordis is considered as a significant cause of morbidity and mortality on the playing field, especially among young male athletes and sportsmen.[67] Athletes gear protection equipment's to avoid the injury to chest is highly recommended, considering relatively high incidence of commotio cordis in sports and athletics.[6]

Commotio cordis can also occur in situations like severe steering wheel impact to the anterior chest wall during a head-on collision. VF induced at the scene leads the paramedics to carry out immediate defibrillation with an automated external defibrillator which showed a possibility of survival.[6]

Commotio cordis is a rare mechanoelectric arrhythmogenic syndrome which is difficult to diagnose, because of the absence of a reliable objective pathological change on the postmortem examination.[8] In addition to sports and motor vehicle-related injuries, assaults leading to blunt injuries on chest contribute to the male preponderance.

A retrospective study[9] revealed male dominance for commotio cordis following assaults, as male-to-female ratio of 37:2, among age group of 13–47 years. Chest blows were produced by fists (28 cases, 71.8%), feet (6 cases, 15.4%), knee (2 case, 5.1%), head (1 case, 2.6%), or objects (2 cases, 5.1%).[9]

This study emphasized the importance of avoiding precordial blow, and early recognition and timely rescue measures in improving the survival rate.

Cardiac rupture

Cardiac rupture refers to damage to the integrity of the myocardial muscle that presents in the circumstances of myocardial infarction, penetrating and blunt trauma, aortic dissections, or iatrogenic consequences. With BCI in perspective, cardiac rupture is most devastating when it occurs simultaneously with the beginning of the cardiac systole, where the muscle fibers are at the peak strength to begin the ejection at the chamber's full capacity. Such damage would be visible in imaging/intraoperatively or postmortem. A case report published in the last decade showed that the damage to the heart mostly involves the left side of the heart, specifically the left atria.[3] The right side was observed to involve the ventricle along with the tricuspid valve, secondary to papillary muscle rupture. Table 1 summarizes timing and characteristics of BCI.

Table 1

Blunt cardiac injury characteristics

Affected cardiac part	Causes	Timing
Mitral and aortic injuries	Sudden increase in intracardiac pressure during a vulnerable phase of the cardiac cycle	Isovolumetric contraction
Aortic valve injury	Tremendous pressure gradient can be generalized across a competent aortic valve	Early diastole
Mitral valve and subvalvular apparatus	When the delivered impact force suddenly changes the full flooded ventricle and stretches the mitral apparatus	Late diastole and early systole

Coronary artery dissection

Almost 2% of coronary artery injuries can be related to BCI, causing coronary artery dissection that leads to myocardial ischemia.[910] The most commonly involved artery is the left anterior descending (71.4%), followed by the right coronary artery (19%), left main (6.4%), and circumflex (3.2%). In addition to the spontaneous occurrence, the high-speed impacts and contact sports are the frequent causes of coronary artery dissection.

With high clinical suspicious, management includes urgent angiography with percutaneous coronary intervention or coronary artery bypass graft surgery versus conservative treatment in case of associated fatal bleeding.

Indirect cardiac injury

It has been shown that significant cardiac damage may occur as a consequence of trauma that was not directed toward the heart. Some injuries may occur in varying magnitudes, but their extent reaches far beyond the original scope of the injury.[11121314] Others explained it as an external force with the secondary rise to the intrathoracic pressure creating stress on the cardiac tissue.[12] The stressful impact of trauma causes a surge of catecholamines release that can cause myocyte injuries, coronary spasm, or thrombosis.[13]

Cardiac herniation

Cardiac herniation is a rare secondary consequence of blunt traumatic pericardial rupture (~1% of cases), and typically appears as a delayed diagnosis, for which the initial radiography may show no specific pathology prior to the herniation.[14] Such delayed diagnosis is a rare as patients are mostly expired before arriving to the hospital, with a survival rate of 36.4%–42.9%.[10] Hernias have many complications or outcomes, with strangulation of a cardiac hernia being one cause of the reversible cardiac arrest post-BCI.[15] Pericardial tears that allow for the cardiac tissue to herniate range from small tear that are rarely detected on imaging or clinical examination, to longer tears (8–12 cm in length). Tear may initially be asymptomatic, only to develop cardiogenic shock after cardiac herniation. In association to the anatomical positioning, preferences of the left cardiac herniation is higher. However, if herniation does not take place, pneumopericardium, enlargement, distortion, and displacement of the heart will be expected on chest X-ray.[14] Some of these injuries yield prolonged time period to be detected or diagnosed, as this is true for a 78-year-old woman, with an incidental finding of a large intrapericardial diaphragmatic hernia, which had developed many years after a traffic accident.[16]

Pericardial effusion and tamponade

With traumatic cardiac injuries, effusions are more commonly hemorrhagic, either due to damage to the integrity of the myocardial wall or its vessels causing bleeding into the pericardial sac, or due to traumatic pericarditis. Many case reports indicated right wall rupture as the source of leakage,[101718] while the left interior descending coronary artery and the right superior pulmonary vein were most frequently the cause of vascular bleeds.[319] The diagnosis of pericardial effusion requires clinical evaluation, Electrocardiography (ECG), and an imaging tool such as simple chest X-ray, focused assessment with sonography for trauma (FAST), echocardiography, computed tomography (CT), and cardiac magnetic resonance imaging (MRI). Rapid diagnosis and treatment of pericardial effusions were found to increase survival rates by up to 80%.[10] The rapid collection of fluids surrounding the heart (tamponade) can be alleviated by pericardiocentesis to assist with consequential symptoms resulting from the pressure exerted on the heart's chambers.

Traumatic cardiac arrest

The difference between traumatic cardiac arrest (TCA) and medical cardiac arrest (MCA) can be highlighted by the hemodynamic status of the patient. MCA is commonly displayed with euvolemia or an underlying cardiac disease indicating to a true arrest with the presence of VF, while TCA is a consequence of hypovolemia due to blood loss characterized by a very low cardiac output state as pulseless electrical activity; with possible reversible causes. Such difference in the pathophysiology justifies the sequential management. Despite the poor outcome of TCA, unexpected survival of some patients points toward the benefits of resuscitative efforts.

With TCA, the efforts of basic life support must not be terminated without the availability of a substitute of advanced life support that addresses the reversible causes. Although other viable options of management such as chest compressions and adrenaline are available for MCA, no positive outcome has been recorded for TCA with these options.[20]

Blunt aortic injury

It is highly unlike that patients with aortic valvular disruption arrive to the hospital alive. Despite that, it is reported to be the most injured cardiac valve followed by the mitral and then tricuspid valve.[21] Traumatic rupture of the thoracic aorta is a life-threatening lesion, and it occurs in 10%–30% of mortality (90% of patients die at the scene and 30% die before surgery) due to blunt chest trauma and it is the second most common cause of death after head injuries.[22] Blunt aortic injury (BAI) occurs with rapid deceleration in road traffic accidents or falls.[22] The most common injury occurs at the aortic isthmus, where the relatively mobile thoracic aorta joins the fixed arch and the insertion of the ligamentum arteriosus.[22] Many retrospective studies have operated on the mortality of BAI revealing a high BAI mortality (31%) in the United States in 2014.[23] In Germany, in 2017, the BAI mortality was as high as 34% within 24 h and 40.8% during the hospital course.[24] Chest X-ray remains the ideal initial diagnostic tool in viewing the mediastinal width in regard to chest injuries. For an in-depth understanding, more sensitive methods are deployed to provide a more detailed perspective of the injury. Such methods include, but are not limited to, CT scan, angiography, transesophageal echography, and MRI.[25]

DIAGNOSTICS

As there is a lack of standard diagnostic criteria, BCI incidence remains uncertain and can only be stated in estimations. BCI-related injuries ranges from fatal, such as chamber rupture, to benign, such as minimal myocardial contusion.[21] Blunt cardiac trauma produces a wide range of myocardial lesions resulting from nonpenetrating chest trauma.

Options for the initial detection of BCI are numerous, but an earlier detection is always beneficial in reducing severity and probability of mortality. The chance for an early diagnosis begins in the field which spans through the ambulance service to the hospital. Therefore, multiple studies recommended the availability of cardiac equipment on all modes of emergency medical transportation with specialized emergency physicians readily available.[2]

In trauma settings, visible injuries warrant an immediate attention to stabilize the patient, making it easier for underlying cardiac injuries not to be easily overlooked or undermined. Therefore, a high index of suspicion is required at the evaluation of a blunt injury. The index should span the entire spectrum of cardiac injuries from cardiac contusion and pleural effusion to cardiac rupture and myocardial infarction.

Notably, some modalities of diagnosis are inherently used without a particular guideline stating it as a standard regardless whether it is BCI or multitrauma injury. Establishing standards would reduce the possibility of missing injuries that might be masked during the initial assessment or asymptomatic in nature, as well as maintaining an index of suspicion.

Despite the benefit of early suspicion, it is only effective when coupled with the most inclusive and comprehensive modalities of diagnosis and management. The investigation might begin with the classic methods such as vital sign monitoring, serial ECG, serial cardiac enzyme testing, chest X-ray, and FAST.

Investigative tools

Biomarkers/cardiac enzymes

Enzyme and proteins level measurements indicate the damage to the integrity of the cardiac myocytes. Troponins and CK-MB are coupled with other modalities such as ECG and echocardiogram. Elevated cardiac markers can be a result of acute or chronic disease, iatrogenic or myocardial injury other than acute coronary syndrome, or heart failure.[26] In general, biomarker elevation is directly proportional to the duration of delayed diagnosis, treatment, length of hospital stay, and risk of mortality.[26] The use of troponin in conjunction with ECG is also suggested in order to identify patients at risk of complications secondary to myocardial contusion.[27]

Heart-type fatty acid-binding proteins

Heart-type fatty acid-binding proteins (H-FABPs) are a new biomarker for myocardial ischemia that can be detected 30 min after the onset of cardiac injury. In assessment of the H-FABP in relation to BCI, no significance was found between cardiac injury due to blunt thoracic trauma and H-FABP (P > 0.05); therefore, it is recommended to conduct wide-scale prospective studies for its use in this context.[28]

Electrocardiography

ECG is an established method of cardiac diagnosis and monitoring. It is used for the detection of rate, rhythm, conduction, and pathological ischemic abnormalities. Its deployment extends to include initial diagnosis as well as monitoring and follow-up. The only concern is the inability to distinguish between ST-segment changes due to a myocardial contusion or genuine myocardial infarction secondary to coronary lesion in the setting of BCI.[29] However, there is always a need for repetition of ECG in trauma settings and having a look at the prior ECG traces, if available, to determine whether the bundle branch block is new or old.

Chest X-ray

Chest X-ray is the simplest radiographic imaging tool routinely obtained in a trauma setting. It is mainly used to determine if further advanced imaging is required. X-ray findings are not a definite tool for cardiac diagnosis, but it may reveal significant findings such as fractures, air collection, hematomas, or heart enlargement. BCI in the setting of tachycardia with the first rib fracture evident on chest X-ray, with associated signs of ischemia should always warrant further investigation. For example, a 29-year-old male patient presented with an underlying cardiac contusion and dissection to the coronary artery following a head-on collision with a truck while riding his bike, severe enough to result in death on the 3rd day of hospitalization.[30] Therefore, limiting the scope of diagnosis to the area or soft tissue that might be affected by the imaged injury site. A retrospective study on the relevance and significance of BCI in severely injured patients indicated a higher risk of cardiac injury when sternal fracture is present.[31]

Focused assessment with sonography for trauma

Ultrasound-based investigative tools provide a variety of options. FAST is a preliminary investigative tool to view not only the heart but also the chest and abdominal cavities in a setting of trauma diagnosis and management. The overall survival outcome of patients with BCI can be improved by early intervention and examination by FAST.[31]

Echocardiography (transthoracic echocardiogram and transesophageal echocardiogram)

Echocardiogram is the most common and undisputed tool, as it provides the opportunity to visualize the heart with all its chambers, valves, pressure, ejection fraction, wall abnormalities, and pericardium. Early assessment with echo leads to accurate diagnosis in case of anterior chest wall injury and management of pericardial effusion.[32]

Coronary computed tomography angiography

It is a superior method of viewing the coronary arteries noninvasively. It showed great potential when used for surgical planning, determining the location, and visualization of cardiac abnormalities. It provided a better description to highlight partial myocardial rupture and ventricular septal defect in relation to the coronary vessels.[3334]

Cardiac magnetic resonance imaging

Cardiac MRI is generally favored when iodine-containing contrast agents are contraindicated such as contrast allergy, renal impairment, and hyperthyroidism. In the context of BCI, it is used to gain insight on the location and extent of damage[33] such as cardiac contusions,[35] pseudoaneurisms,[34] and for follow-up.

GRADING OF SEVERITY

BCIs have a wide scope of injury patterns that dictate the length and degree of intervention. For this purpose, cardiac injuries grading has been provided by the American Association for the Surgery of Trauma (AAST).[1]

Autopsy-based studies

there are very limited autopsy-based studies in the literature, although most of cardiac trauma died before arrival to the ED. Fedakar et al.[36] studied 2487 autopsied cases in Turkey, of them 160 had cardiac injury (6.4%). Most of cardiac injuries were penetrating and 12.5% were blunt in origin. The vast majority of injuries was cardiac rupture and only 3 had cardiac contusion. The risk of atrial rupture was higher than of ventricular rupture and all atrial rupture cases died at the scene. In another study from the USA, Teixeira et al.[37] studied 304 autopsied cases, of them 96 (32%) had BCI. Most of cases died at the scene (78%). The right side was the most frequently affected (right atrium; 30%, right ventricle; 27%). Among BCI, 64% had transmural rupture and multiple chambers were ruptured in 26%, the right atrium in 25%, and the right ventricle in 20%. Thoracic aorta was injured in 47% of these BCI cases whereas sternal injury was found in 32%.

MANAGEMENT

As a part of the emergent management of patients presenting with multiple trauma, hypotension and tachycardia warrant the need to exclude internal hemorrhage as the main cause rather than BCI itself.[10] On the other hand, exclusion of myocardial infarction/pulmonary embolism/dissected aorta are the ultimate priorities among all other causes presenting with chest pain.

BCI management narrows down to either stabilization efforts, to maintain the level of injury and prevent deterioration, aggressive resuscitation, or surgical intervention. These require an equipped trauma setting and well-fitted surgical operation rooms.

Poststabilization monitoring is a critical requirement to ensure recovery and prevent deterioration. Treated patients who are believed to be hemodynamically stable should be monitored.[38]

Pericardiocentesis

Although surgical intervention is the definitive management for cardiac tamponade, pericardiocentesis is a temporarily intermediate measure. Alone, percutaneous pericardiocentesis does not affect the survival rate in patients with traumatic cardiac injuries, as it only used as a tool to provide more time and aid in the safe transfer of patients to surgery-definitive surgical management.[3940] An exception to the norm was a case of a pressure injury resulting from a dynamite blast, where transthoracic echocardiogram, revealed a swinging heart appearance and collapse of the right side of the heart associated with symptoms of hypotension resistant to treatment, loss of consciousness, and desaturation, which necessitates pericardiocentesis. Aspiratation of blood could be sufficient to normalize the patient hemodynamics and exclude the need for surgical intervention subsequently.[41]

Thoracotomy

In the instances where noninvasive intervention is ineffective in stabilizing the patient or resuscitation ceased to succeed, surgical intervention “thoracotomy” is highly and promptly recommended. Emergency department thoracotomy (EDT) is a lifesaving procedure when performed by trained surgeons[42] to mitigate distress in cases such as tamponade, internal cardiac massage, and hemorrhage control.[43] EDT, however, is thought to be controversial in the setting of BCI, stated by a meta-analysis conducted to assess the mortality and neurologic results post-EDT. Patients should have vital sign present on examination at time of admission or emergent thoracotomy within 15 min of cardiac arrest.[44] Shifting the focus to the opening site median sternotomy, clamshell incision, and left lateral thoracotomy are different approaches to gain cardiac view, provided midline sternotomy best in surgical exposure of the heart. Attempting median sternotomy using a fret sternum saw in the emergency department by trauma surgeons does not require significantly more time than a left lateral thoracotomy or clamshell incision in an emergency situation. Taking into consideration that whichever is the fastest to decrease the risk of hypoxic brain injury is the best.[42] Along the years, physicians have been occupied with means to improve their practice in order to achieve that continuous assessment of survival, which lead them to 14% survival rate following EDT and 24% successful attempts to rescue traumatic patients.[45]

The benefit of surgical intervention is inconsequential in patients with extensive damage caused by the traumatic cardiac injury and can most prominently be seen in patients who sustained extensive cardiac damage. Due to its invasiveness, multiple efforts have been exerted and are being attempted to develop a less invasive methods (e.g., endovascular hemorrhage control), but none yet offers concrete evidence of superior performance when compared to thoracotomy.[43]

Management of blunt aortic injury

Management of BAI has three common approaches. The summary of findings from retrospective studies is presented in Table 2.

Table 2

Summary of studies involving blunt aortic injury treatments

Study	Treatment approach	Major findings
USA, 2014[21]	Conservative (medical) management	Aims to identify patients that would benefit from medical management Injury grade and secondary signs of injury stratification identifies ideal patents for medical management Grade Ι and ΙΙ aortic injuries are finer candidates for medical management
Germany, 2017[22]	Endovascular versus surgical treatment	Aims to analyze the value of different therapy approaches in BAI High-speed accidents were the main injury pattern Endovascular treatment prevailed as the preferred method, showing low mortality rate Surgical means showed higher rate of survival, regardless of injury grade
Spain, 2011[23]	Conservative versus surgical and endovascular treatment	Compare survival and cardiovascular complications of acute BAI In-hospital survival rates were 21.6%, 22.7%, and 14.3% of conservative, surgical, and endovascular, respectively Conservative treatment survival rate in 1, 5, and 10 years found as 75%, 72.3%, and 66.7%, respectively Surgical treatment survival remained the same at 1, 5, and 10 years as 77.2% Endovascular treatment survival remained the same at 1 and 5 years as 85.7% Survival depends on patient selection for relative treatment

BAI: Blunt aortic injury

Intra-aortic balloon pump in myocardial contusion

Intra-aortic balloon pump acts by increasing diastolic blood pressure, improving diastolic coronary perfusion, and increasing cardiac output and stroke volume by reducing afterload.[46]

Severe myocardial contusion is a representation of diminished function and in exceptionally rare conditions can cause acute heart failure that could be refractory to vasoactive medications in cardiac shock, intra-aortic balloon is inserted into the aorta, positioned and inflated to counter pulsate with blood flow. The balloon's targeted function is to simultaneously increase the cardiac output, ejection fracture, coronary perfusion pressure, stroke volume, and myocardial oxygen delivery while decreasing the heart rate, systemic vascular resistance, and afterload.[4647] These result in better cardiac function and reduced vasoactive medication consumption. The intra-aortic balloon pump is limited in cases of aortic injuries and irreversible brain injuries, as it may worsen the magnitude of the injury.[47]

Consensus and guidelines

The AAST adopted the evaluation and treatment guidelines of myocardial contusion established by the Eastern Association for the Surgery of Trauma.[48] The authors recommended the use of admission ECG and troponin I in all patients, in whom BCI is suspected which can be ruled out only if both ECG result and troponin I level are normal.[48] Furthermore, echocardiogram is not effective as a screening tool for BCI and should be reserved for patients with hypotension and/or arrhythmias.[48]

CONCLUSIONS

Regardless of the variability in the spectrum of modalities and medical/surgical resources, BCIs remain a puzzle. In the past decade, researchers around the globe have made an admirable effort in solving various part of the mystery however; it still needs further prospective studies.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Ethical conduct of research

This manuscript represents a literature review. Because this project involved no experimental design, the Institutional Review Board approval was not required. Applicable EQUATOR Network (http://www.equator-network.org) guidelines were followed.