How common is pulmonary embolism compared to acute myocardial infarction among patients with severe mental illnesses?

Sudden unexpected death is more frequent among patients with severe mental illnesses (SMI) than the general population.1, 2 Coronary heart disease is the primary cause of sudden unexpected death in the general population,3 which is assumed to be the case among patients with SMI.1, 4 Patients with SMI, especially those with catatonia, also have an elevated risk for pulmonary embolism (PE),5-8 which is another important cause of sudden unexpected death. We recently reported that the proportion of patients with psychiatric diseases who experience out-of-hospital cardiac arrest due to PE is nine times higher than that among the non-psychiatric population.9 It is thus important to investigate prevalence and disease burden of PE among patients with SMI. Therefore, we aimed to examine the proportion of comorbid SMI among patients with PE and those with ST-elevation myocardial infarction (STEMI) in a Japanese tertiary hospital. This study was conducted at Tertiary Emergency Medical Center of Tokyo Metropolitan Bokutoh Hospital in Tokyo, Japan. This retrospective chart-review study was approved by the institutional review board of Tokyo Metropolitan Bokutoh Hospital and the requirement for informed consent was waived because the study utilized de-identified data that were acquired through routine clinical care. A systematic chart review of patients with PE and those with STEMI who visited our emergency department between 1 January 2011 and 31 December 2018 was performed. Physical diagnosis on admission and psychiatric diagnosis were identified using an electronic chart. Mood disorders, including depression, bipolar disorder, and schizophrenia, were considered as SMI. The proportion of patients with psychiatric disorders (i.e., SMI plus other psychiatric disorders: dementia, anxiety disorders, or alcohol dependence) and the proportion of patients with SMI in the STEMI and PE groups were compared. The following demographic and clinical information were also collected: age, sex, psychiatric diagnoses according to the ICD-10, and the occurrence of out-of-hospital cardiac arrest. Statistical analyses were performed using R 3.5.2 with EZR package (R Software, Miami, FL, USA). The proportion of patients with SMI and the proportion of patients with psychiatric diseases in the STEMI and PE groups were compared using Fisher's exact test. Fisher's test was used to compare categorical variables while the Mann–Whitney U-test was used to compare continuous variables. A P-value < 0.05 (two-tailed) was considered statistically significant for all tests. One hundred and forty-nine patients with PE and 996 patients with STEMI were identified during the study period. The proportion of men was significantly lower in the PE group than in the STEMI group (45.6% vs 81.6%, P < 0.001). The median age (66 [51–75] vs 67 [56–75] years, P = 0.147) and the proportion of patients who experienced out-of-hospital cardiac arrest (12.8% vs 14.5%, P = 0.706) were not different between the two groups. The proportion of psychiatric disorders was significantly higher in the PE group than in the STEMI group (18.1% [27/149] vs 4.0% [40/996], P < 0.001); this was also the case among patients with SMI (13.4% [20/149] vs 1.5% [15/996], P < 0.001; Table 1). In this study, the proportion of patients with psychiatric disorders, especially SMI, was significantly higher among patients with PE than among those with STEMI. Surprisingly, the number of patients with SMI in the PE group (n = 20) was even higher than that in the STEMI group (n = 15), despite the significantly low number of patients in the PE group (n = 149 vs n = 996). Patients with SMI are known to have an elevated risk for both PE5-8 and STEMI.10 Nevertheless, PE, in comparison to STEMI, has received less attention as a cause of sudden cardiac death among SMI patients, possibly because of its much lower prevalence in the general population.11 The initial clinical presentation of a large and potentially life-threatening PE can be minor and even asymptomatic.12 Therefore, clinical vigilance is important in order to prevent all negative consequences. Recent reports on the elevated risk for PE among patients with SMI5-8 may raise physicians’ awareness of this condition to a similar extent as their awareness of STEMI. This may increase the incidence of PE among patients with SMI. Furthermore, there are some possible factors associated with venous thromboembolism, such as restraint,13 excessive sedation caused by psychotropics,13 and catatonia14; patients with SMI are more likely to be at risk. These risk factors might account for a larger representation of SMI patients in the PE group, compared to those in the STEMI group. Further well-designed studies are necessary to confirm our findings. There are several limitations to be noted in this study. These include unmeasured confounding factors, lack of information on the severity of psychiatric diseases, and lack of prescription information as well as adherence data. Another limitation is that this study is a retrospective Japanese single-center study. In conclusion, the burden of PE may be even higher than traditionally assumed and may be comparable to that of STEMI among patients with SMI. Further studies are needed to help decrease the mortality rate among patients with SMI. All authors have completed the International Committee of Medical Journal Editors uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare that they did not receive any support from any organization for the submitted work; they did not have any financial relationship with any organization that might have an interest in the submitted work during the previous 3 years described; and there exists no other relationships or activities that could have influenced the submitted work.