Forensic aspects of cardiovascular pathology

Penetrating injuries

Penetrating injuries of the heart and cardiac vessels may result from any object that pierces the organ, including fractured ribs, sharp objects such as knives, tools such as a screwdriver or a barbecue fork, and high-velocity blunt objects such as bullets. Stab wounds result from any sharp object penetrating into the skin, soft tissues, and organs with the injury deeper than it is wide on the surface of the skin. Such injuries most often result in death from hemorrhage into the pericardial sac with tamponade or from exsanguination due to extensive hemorrhage into the pleural cavities and soft tissues surrounding the pericardium. These injuries may involve the myocardium, the coronary arteries, or the great vessels. The size of the injury as well as the structures involved will determine the speed at which sufficient blood is lost to result in death. Accurate measurements of injury dimensions, location, and estimation of depth of penetration are often helpful in assessing the type of object causing the injury. Features of the object injuring the heart are often well preserved in the muscular heart, and often are consistent with or even more precise than measurements on the surface of the skin, which is subject to distortion from Langer’s lines ( Fig. 22.4A and B ). Injuries of the blood vessels can result in hemorrhage or introduction of air into the cardiovascular system ( Fig. 22.5 ).

Gunshot wounds vary in the extent of injury, with smaller caliber bullets generally causing less damage to the heart than larger caliber bullets, and rifle wound injuries being much more extensive than those sustained from handguns. The damage to the heart is a result of the amount of energy the traveling bullet releases into the tissue as it traverses. The more gunpowder in a projectile, the more energy the bullet has to transfer to the tissues, and the greater the damage. A handgun typically causes a small- to medium-sized perforation in the heart while a rifle will cause pulpification of the myocardium ( Fig. 22.6 ). Shotgun wounds of the heart vary based on how close the shotgun is fired to the body. The closer the shotgun is to the body when fired, the tighter the distribution of the pellets, and the more they travel together as one object causing a large defect with a smooth to scalloped margin. The further away from the body when fired, the more spread out the pellets become and the pattern of injury will be smaller, punctate defects approximating the size of the pellets . Injuries of the blood vessels can occur from direct perforation or secondary damage from a bullet passing close to the vessel ( Figs. 22.7 and 22.8 ).

Blunt force injuries

Blunt force trauma of the heart and vessels results from direct impact or acceleration–deceleration forces . Direct impact injuries may be from an object striking the chest, such as a baseball, or from the torso impacting a hard object or surface, such as steering wheel. Acceleration–deceleration injuries occur when the body, moving at a high velocity, strikes a fixed object; although the motion of the body is stopped, the internal organs continue to move, and may have changes in velocity at differential rates resulting in lacerations depending on the tethering points of individual structures and the properties of the individual tissues. Resultant trauma, causing injury or even death, may be as minimal as no gross or microscopic evidence of injury, as in a commotio cordis (a phenomenon in which a sudden blunt impact to the chest causes sudden death in the absence of cardiac damage), or as extensive as focal rupture of the cardiac muscle . Occasionally, the heart may even be expelled from the chest when gaping lacerations of the skin and chest wall are present. Such extensive injuries are most often seen in high-speed motor vehicle and motorcycle crashes where there are extensive blunt force injuries ( Fig. 22.9 ). Additionally, small aircraft collisions may result in extensive injuries of the heart and vessels, both from impact and from fragments of penetrating debris ( Fig. 22.10 ). Contusions of the heart result from direct impact or compression of the heart and may occur on the anterior or posterior surface of the heart. Concurrent injury to the skin, soft tissues, and bones need not be present. Contusion may be present on the epicardial surface, through the full thickness of the myocardial wall or on the endocardial surface . However, endocardial hemorrhages are more commonly associated with reperfusion injury. Care should be taken to microscopically examine such lesions when related to the cause of death. Contusion may cause pain simulating angina pectoris or myocardial infarction, but may remain undetected and asymptomatic. Microscopic examination of the contusion reveals abundant interstitial hemorrhage with variable findings, including contraction band necrosis and damage to muscle bundles. Similar to a resolving myocardial infarct, healing of a contusion with necrotic softening renders the wall weak and prone to rupture with resultant hemopericardium and cardiac tamponade. Replacement fibrosis is the end result of a healed cardiac contusion and, if large, a posttraumatic aneurysm may form .

Falls or jumps from great heights, such as descent from a tall building, often lead to extensive fractures of the ribs, sternum, and vertebral column which may displace and cause secondary injuries including hemorrhage of the soft tissues, contusion of the myocardium, and puncture lacerations of the heart and vessels. The deceleration forces may also cause primary lacerations to the pericardium, heart, and great vessels . Lacerations may be small and focal or large and gaping ( Fig. 22.11 ). The vast majority of aortic lacerations and transections occur in the thoracic segment 2–3 cm past the origin of the left subclavian artery at the aortic isthmus. It is at this location where the aorta is most fixed by the ligamentum arteriosum, resulting in a focus of increased stress during deceleration. The second most common site of aortic laceration is just proximal to the innominate artery in the ascending aorta, another relative point of fixation. A partial thickness laceration of the intima or media may lead to a posttraumatic aneurysm which may remain undetected while contained by pressure from surrounding anatomic structures or may continue to expand, causing pain as it presses on surrounding structures. Margins of an aneurysm located at the site of the laceration may cause a coarctation and disrupt blood flow past this site . A partial thickness laceration with maintained circulation may also result in retrograde or antegrade dissection of the aortic wall, causing occlusion of the intimal lining of the aorta or coronary artery and sudden death . Injuries similar to those discussed in the aorta can occur in the branches of the aorta or in the peripheral arteries, with similar pathologic sequelae . Injuries to peripheral veins often lead to thrombotic occlusion with infarction of dependent tissues and organs . Nonpenetrating blunt trauma may also damage the coronary arteries and cardiac valves . Lacerations of the intima and media may lead to local thrombosis or dissection resulting in myocardial ischemia. The left anterior descending coronary artery is most commonly involved, likely due to a location of vulnerability to blunt impact in the anterior chest. Lacerations of the cardiac valve leaflets and avulsion at points of attachment, as well as rupture of the chordae tendineae and papillary muscles, may lead to valvular insufficiency and even infective endocarditis . The aortic valve most commonly experiences lacerations and avulsion of the leaflet attachments, while the chordae tendineae and papillary muscles of the mitral valve tend to incur damage. Both native valves and mechanical and bioprosthetic valves may be subjected to damage in blunt impact trauma .

Identifying death from commotio cordis is heavily dependent on documentation of witnessed or circumstantial blunt impact to the chest without gross or microscopic injury of the heart identified at autopsy ( Figs. 22.12 and 22.13 ). Typically, injuries to the soft tissues and bones of the chest are absent to minimal and should never be extensive enough to cause death . A thorough scene investigation may make the difference between determining death due to commotio cordis and an undetermined cause of death. Details surrounding death should be thoroughly documented, particularly extensive explanation of the activities before and after collapse. Multiple witness accounts should be gathered when a decedent was engaged in a sporting activity during collapse, particularly those with hard objects such as baseballs, lacrosse balls, and hockey pucks . Decedents involved in motor vehicle crashes where there is possible chest impact should be examined for signs of cardiac activity after death. A lack of blood at the scene in a decedent with injuries that would be expected to bleed should raise suspicion for a sudden loss of cardiac activity and the possibility of commotio cordis. A sudden collapse during horseplay or wrestling should also raise suspicion for commotio cordis. Correlating negative autopsy findings, including histopathology, toxicology, and if appropriate molecular genetic testing for cardiac channelopathies and cardiomyopathies, with a blow to the chest will allow one to make the diagnosis of commotio cordis ( Fig. 22.14 ). Chest impacts leading to commotio cordis typically occur to the anterior chest wall over the heart and must occur at a very specific point in the cardiac cycle to cause ventricular fibrillation and death. Pig studies have shown that chest impacts with a baseball-type object caused commotio cordis if the impact occurred during a 30 ms window on the upslope of the T-wave, just before the peak. This represents the repolarization phase of the cardiac cycle. The most common cardiac dysrhythmia experienced is ventricular fibrillation . Cardiac dysrhythmias from witnessed chest impacts followed by unresponsiveness may be reversed with quick use of automated external defibrillator (AED) devices. AEDs are most effective when utilized within 3 min of collapse and readily available AEDs at sporting events has become the rule rather than the exception. While resuscitation was once believed to be futile, survival is now reported in 35% of reported cases .

Congenital disorders

With current medical advances, most cardiac congenital anomalies are identified at a very young age and are successfully treated. In those who die from the anomalies, their deaths typically do not fall under the jurisdiction of the coroner or medical examiner, as the cause of death is natural and related to their previously diagnosed congenital heart disease. In cases of sudden unexpected death, congenital defects are typically readily identified at autopsy. However, more subtle or rare anomalies may be identified only upon consultation with a cardiac pathologist. Occasionally, death occurs suddenly and unexpectedly after a period of time following successful repair of a known congenital defect from which long-term survival was expected. In such cases, the death typically does fall under the jurisdiction of the local coroner or medical examiner and an autopsy should be performed to determine the cause of death. It is often helpful to review operative reports and if possible, to have the surgeon present for evaluation of the heart, to better understand the procedure, and receive immediate feedback regarding the state of the repair . Once out of the adolescent period, sudden death due to a congenital cardiac anomaly is rare, though ventricular and atrial septal defects may be identified in older adults who have managed to remain undiagnosed and compensate for the defect until the heart becomes enlarged and a cardiac dysrhythmia occurs, causing sudden death . The threshold to consult a cardiac pathologist for gross or microscopic examination should be low, particularly in cases of complex congenital anomalies or rare genetic disease processes.

Cardiomyopathies

Cardiomyopathies are covered at great length elsewhere in this book, but here we highlight the most common causes of sudden and unexpected cardiac death related to cardiomyopathies . Dilated and hypertrophic cardiomyopathies are the most prevalent types identified in SCD. Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a less commonly identified cardiomyopathy, but should be excluded in all cases of SCD. Dilated cardiomyopathies alter the normal muscular function of the heart leading to a variety of physiologic compensatory changes and death typically results from dysrhythmia, conduction system abnormalities, or secondary effects of heart failure . Identification of cases in which saving genetic material may be helpful can be complex, but in sudden death where a cardiomyopathy in the decedent is known, a family history of cardiomyopathy is known, or autopsy findings suggest a genetic cardiomyopathy, samples should be collected. It is best to err on the side of caution and collect material for potential genetic studies even if subsequent analysis is later deemed unnecessary.

Dilated cardiomyopathies are commonly identified at forensic autopsy. Death may be seen at any stage of the progressive process of cardiac enlargement, ventricular chamber enlargement, thinning of the left ventricular wall, and contractile dysfunction. The heart enlarges primarily from systolic failure, though diastolic failure also occurs. Dilatation can lead to progressive dysfunction of the tricuspid and mitral valves, manifesting as regurgitation. Despite efforts to compensate for the dysfunction, the heart eventually sustains too much damage to maintain adequate cardiac function. A variety of underlying etiologies for dilatation are well known, but in the forensic population of sudden death, alcohol and hypertension are the most commonly identified underlying etiologies ( Fig. 22.15 ). Dilatation from unreported or undiagnosed remote myocarditis is also seen. Much less common are genetic mutations leading to familial dilated cardiomyopathy .

Occasionally, antemortem symptoms are reported including fatigue, dyspnea on exertion, and edema. Often, there is no history of such symptoms and clues must be gathered during the external examination and examination of the body cavities and organs at the time of autopsy. Lower extremity edema, pulmonary edema, and increased serous fluid in body cavities can be observed at autopsy. A thorough medicolegal investigation may reveal a history of known cardiomyopathy or the presence of medications suggestive of treatment for congestive heart failure, including angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, beta-blockers, diuretics, and vasodilators. Investigation may also reveal medications indicating a possible underlying etiology of the cardiomyopathy, for example, antihypertensive medications. The presence of numerous alcoholic beverages and/or medications such as folate and vitamin B12, can suggest a history of chronic alcohol use disorder.

Thorough examination of the organs at autopsy may also reveal clues for underlying etiologies. Identification of hepatosteatosis or hepatic cirrhosis at autopsy would support ethanol as the underlying etiology. Arteriolonephrosclerosis suggests a history of hypertension ( Fig. 22.16 ). The presence of a billowing mitral valve with myxoid degeneration is consistent with mitral valve prolapse (MVP). Fibrosis and thickening of the valve and chordae tendineae indicate long-standing prolapse ( Fig. 22.17 ). Histopathologic examination may reveal patchy fibrosis suggestive of a remote viral myocarditis. Because alcohol is cardiotoxic, its cardiovascular effects in addition to cardiomyopathy include arrhythmias, hypertension, and stroke. Binge drinking has been shown to cause myocardial inflammation. While chronic alcohol use disorder is identified more frequently in men than women, women tend to suffer the cardiotoxic effects of alcohol more commonly than men, despite consuming a lower quantity than men. Cardiomyopathy from chronic alcohol use disorder and sudden death may still occur in persons abstinent from alcohol if they have suffered irreversible or progressing myocardial damage from past alcohol consumption. Lack of present overconsumption of alcohol or presence of alcohol containers upon medicolegal investigation should not exclude alcohol as the underlying etiology of the cardiomyopathy. In such cases, a history of past alcohol misuse provides sufficient evidence . Rarely, the cause of the dilated cardiomyopathy cannot be identified . Less common causes of cardiomyopathy include doxorubicin chemotherapy treatment, collagen vascular disease, starvation, endocrine diseases, drugs such as cocaine, heavy metals, granulomatous disease such as sarcoidosis, neuromuscular disorders, and the peripartum period. A complete medicolegal investigation combined with findings from a complete and through autopsy will often allow for identification of these underlying etiologies. Occasionally, despite extensive efforts, a likely cause may not be identified .

Hypertrophic cardiomyopathy (HCM) is a widely recognized cause of sudden death in the preadolescent, adolescent, and young adult population, often without antemortem symptoms or diagnosis. While both males and females may be affected, the typical forensic scenario is a teenage male participating in a vigorous sporting activity who suddenly collapses and cannot be resuscitated ( Fig. 22.18 ). Most patients are asymptomatic, and the first presentation of disease can be sudden death. When present in females, the disease typically presents at a younger age, with symptoms, and is medically evaluated. At autopsy, the heart is enlarged, and the interventricular septum is typically disproportionately enlarged in comparison to the left ventricular free wall. Cutting the heart to show a four-chamber view will allow for the most obvious identification of this discrepancy . Occasionally, the free wall and the interventricular septum may be symmetrically thickened, or the free wall may even be thicker than the interventricular septum. The risk of sudden death in HCM patients is high, even if the left ventricular wall and interventricular septum thickness is not marked. Extensive histologic sections should be taken. Microscopic examination reveals myocyte disarray or disorganization, particularly high in the interventricular septum, but disarray may also be identified in the left ventricular free wall. Fibrosis is often present and may be identified both grossly and microscopically. Intramural coronary arteries with a thickened wall and reduced lumen may also be observed . Subendocardial fibrosis from ischemia may be identified. Endocardial fibrosis occurring over the septum immediately subjacent to the aortic valve is typically present, as well as a patch of fibrosis in the subaortic mitral region due to sustained repetitive impacts . While consultation with a cardiac pathologist is not necessary, benefit may be gained from an extensive evaluation of the coronary vessels and structural documentation of the heart. Since HCM is a genetic disorder known to have a high incidence of sudden death and living relatives may also be affected, fresh postmortem samples should be collected and saved for potential future genetic testing. Identification of HCM at autopsy may prompt testing of relatives for HCM and, if identified, lives can be prolonged through medical intervention including medication and adjustment of activities of daily living .

ARVC manifests with gross or microscopic fibrofatty replacement of the right ventricular myocardium. ARVC can manifest with sudden unexpected death from postadolescence to age 50. At autopsy, the right ventricle may exhibit extensive fibrofatty replacement of the right ventricle such that the wall is translucent when held to light. However, cases may be missed exclusively on gross examination. Thorough sectioning of the heart, including sections of the right ventricle, in cases of sudden death when routine investigation, toxicology, and histology do not illicit an underlying cause of death may help to identify grossly inapparent cases of ARVC .