Unexpected death due to right-sided infective endocarditis in a methamphetamine abuser

1. Introduction 

Right-sided infective endocarditis (IE) is relatively rare among the overall cases of IE, and is considered to result in good prognosis compared with left-sided IE [1]. Since right-sided IE frequently occurs in drug abusers [1], [2], it is considered to be an important disease for forensic pathologists. We report an autopsy case of a methamphetamine abuser who suffered from severe right-sided IE.

2. Case history 

A 44-year-old woman was taken to a hospital by ambulance having almost lost consciousness. She had a history of depression, and had attempted to commit suicide several times. On admission, she demonstrated low blood pressure, anuria and high fever with a marked increase in white blood cells. Since many scars from venous injections and old scars of cuts from previous attempts at suicide were visible on her extremities, she was clinically diagnosed as being in a state of shock probably due to drug intoxication. She died 6 h after admission.

3. Autopsy findings 

The autopsy was performed 10 h after her death at Kyushu University, Fukuoka, Japan. The deceased was 157 cm tall and weighed 51.5 kg. Examination of the external surface of the body showed some old bruises, but no evidence of any traumatic wounds that had formed recently. Both old and fresh scars from venous injections, and old scars from cuts were seen in several places on her extremities (Fig. 1). No evidence of acute infection was noted in or around these scars.

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Fig. 1. Scars from venous injections on the left arm (a) and the right foot (b). Old scars from cuts can also be seen on the left arm (a).

On internal examination, the heart weighed 239 g. Dark reddish-brown colored vegetation with involvement of the septal and posterior leaflets was visible on the tricuspid valve (Fig. 2). Since some chorda were also involved, tricuspid regurgitation might have occurred on and near the annules. The other valves and the heart muscle were of an almost normal appearance. The bilateral lungs (weight: left, 696 g; right, 840 g) showed multiple hemorrhagic infarcts, and a dark reddish-brown thrombus could be seen in the left main pulmonary artery (PA).

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Fig. 2. Macroscopic appearance of tricuspid valve. Deformity of septal leaflet and vegetation (arrowheads) can be seen.

On microscopic examination, thrombi of the left main and peripheral PA contained not only many polymorphic neutrophils, but also abundant colonies of cocci (Fig. 3a). Gram staining was positive for almost all of the cocci. In the lung parenchyma, there was multiple massive coagulative necrosis with bacterial infection. Secondary pneumonia with abscess formation was seen in and around the infarcts (Fig. 3b). Destruction of the tricuspid valve and acute involvement by many neutrophils and cocci in the septal and posterior tricuspid valve with a few foci of granulation were noted (Fig. 4a,b). The other valves were intact, but some mycotic emboli were discernible in the heart muscle of the bilateral ventricles (Fig. 5). Mycotic emboli were also confirmed in the brain, kidneys, adrenal glands, and spleen. The liver demonstrated centrilobular hemorrhagic necrosis probably due to hypovolemia at critical periods.

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Fig. 3. Microscopic appearance of the lung. (a) Many cocci are contained in the thrombi of PA (H&E; original magnification, ×10). (b) Secondary pneumonia in and around the infarcts (H&E; original magnification, ×25).

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Fig. 4. Microscopic appearance of the tricuspid valve. (a) Longitudinal section of superior ventricular septum. Destruction of the septal leaflet of the tricuspid valve (arrow) (H&E; original magnification, ×5). (b) High-power view. Cocci can be seen with infiltration of neutrophils (H&E; original magnification, ×75).

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Fig. 5. Microscopic appearance of cardiac muscle. Abscess formation due to mycotic emboli can be seen (H&E; original magnification, ×50).

Toxicological analysis revealed that the blood total methamphetamine concentration was 0.61 μg/ml. Postmortem cultivation of bacteria was not performed.

4. Discussion 

Primary IE was observed in the tricuspid valve, and many mycotic emboli were seen in the pulmonary artery in the present case. In addition, these mycotic emboli were disseminated to other organs from the lung. These findings suggest that the victim had already been suffering from a septic state due to right-sided IE on admission. Accordingly, the cause of death was diagnosed as septic shock due to right-sided IE.

Right-sided IE is considered to be relatively rare [1], and its prognosis is known to be good compared with left-sided IE [3]. It is essential to remember that intravenous injections are considered to be major risk factors of right-sided IE [1]. The reason why right-sided IE commonly occurs in drug abusers is thought to be that particulate matter in the injected material may damage the tricuspid valve through continuous bombardment of the endothelial surface [4]. However, the clear mechanism of this particle or drug-induced valvular damage is as yet unknown [5]. In the case of addictive drugs, cocaine may have a greater propensity to cause injury to the myocardial surface than other injected drugs, because of tissue ischemia caused by vasospasm [6], [7].

In right-sided IE, the occurrence rate of pulmonary infarction such as that seen in the present case is very high (60–100%) [3], [8], while hemoptysis and pneumothorax are reported as severe late complications [2], [8]. Since drug abusers have a tendency to hesitate visiting a hospital because they wish to hide their abuse, the severity and mortality of IE among unlawful drug abusers may be higher than among common citizens, and sudden unexpected death may sometimes occur.

In the present case, we were easily made aware of the possibility of the victim's drug abuse from external physical findings. However, we should always bear in mind at autopsy that the presence of right-sided IE may be a predicting factor of drug abuse, even if the injection site is not clearly visible. For this reason we should carry out a full toxicological analysis of addictive drugs for victims with right-sided IE.