The Prognostic Value of Myocardial Injury in COVID-19 Patients and Associated Characteristics

Background: Since December 2019, Coronavirus disease 2019 (COVID-19) has emerged as an international pandemic. COVID-19 patients with myocardial injury might need special attention. However, understanding on this aspect remains unclear. This study aimed to illustrate clinical characteristics and the prognostic value of myocardial injury to COVID-19 patients. Methods: This retrospective, single-center study finally included 304 hospitalized COVID-19 cases confirmed by real-time RT-PCR from January 11 to March 25, 2020. Myocardial injury was determined by serum high-sensitivity troponin I (Hs-TnI). The primary endpoint was COVID-19 associated mortality. Results: Of 304 COVID-19 patients (median age, 65 years; 52.6% males), 88 patients (27.3%) died (61 patients with myocardial injury, 27 patients without myocardial injury on admission). COVID-19 patients with myocardial injury had more comorbidities (hypertension, chronic obstructive pulmonary disease, cardiovascular disease, and cerebrovascular disease); lower lymphocyte counts, higher C-reactive protein (CRP, median, 84.9 vs 28.5 mg/L, p<0.001), procalcitonin levels (median, 0.29 vs 0.06 ng/ml, p<0.001), inflammatory and immune response markers; more frequent need for noninvasive ventilation, invasive mechanical ventilation; and was associated with higher mortality incidence (hazard ratio, HR=7.02, 95% confidence interval, CI, 4.45–11.08, p<0.001) than those without myocardial injury. Myocardial injury (HR=4.55, 95% CI, 2.49–8.31, p<0.001), senior age, CRP levels, and novel coronavirus pneumonia (NCP) types on admission were independent predictors to mortality in COVID-19 patients. Conclusions: COVID patients with myocardial injury on admission is associated with more severe clinical presentation and biomarkers. Myocardial injury and higher HsTNI are both strongest independent predictors to COVID related mortality after adjusting confounding factors. In addition, senior age, CRP levels and NCP types are also associated with mortality.

Conclusions: COVID patients with myocardial injury on admission is associated with more severe clinical presentation and biomarkers. Myocardial injury and higher HsTNI are both strongest independent predictors to COVID related mortality after adjusting confounding factors. In addition, senior age, CRP levels and NCP types are also associated with mortality.
Trial registration: Not applicable.

Background
Coronavirus disease 2019 (COVID-19) is a newly recognized infection which was rst reported in Wuhan, China [1]. Since the beginning of the outbreak, COVID-19 has emerged as a pandemic globally [2], and the number of cases is rising at an exponential rate [3]. As of November 15, 2020, there have been a total of more than 53,766,728 laboratory-con rmed cases of COVID-19 globally, and it poses a great threat to public health in the world as evidenced by 1,308,975 deaths [4]. COVID-19 is caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The clinical spectrum appears to be very wide, including asymptomatic infection, mild upper respiratory disease, and severe viral pneumonia with respiratory failure, and even death [5].
The condition of some patients with COVID-19 may deteriorate rapidly, particularly in older patients with underlying comorbidities including cardiovascular disease [6]. Furthermore, SARS-CoV-2 can affect the cardiovascular system in multiple ways, increasing morbidity in patients with potential cardiovascular disease and causing myocardial injury and dysfunction [3]. High-sensitivity troponin I (Hs-TnI) provides the potential to earlier identify myocardial injury and assists treatment [7]. Some studies provide insights into the incidence of cardiac complications associated with SARS-CoV-2 [8,9], while imaging manifestations, cytokine levels and the prognostic value of cardiovascular risk factors in COVID-19 patients are poorly understood. We aimed to comprehensively de ne clinical characteristics, laboratory results, outcomes, and management strategies of COVID-19 patients, then to nd whether there is an association of myocardial injury and other biomarkers with mortality. This study may also provide clues to potential mechanisms associated with myocardial injury.

Study Design And Patients
In this study, we retrospectively enrolled 320 COVID-19 patients admitted to the Renmin Hospital of Wuhan University from January 11, 2020 to March 25, 2020 with approval from the Research Ethics Committee of the Renmin Hospital of Wuhan University, Wuhan, China (approval number: WDRY2020-K038). 16 cases without signi cant biomarkers, including Hs-TnI and creatinine kinase-myocardial band (CK-MB) levels, were excluded. Thus, a total of 304 patients were nally included in the study.
The con rmed diagnosis of COVID-19 was de ned as a positive result by using real-time reverse-transcriptase polymerase-chainreaction (RT-PCR) detection for routine nasal and pharyngeal swab specimens or anti-SARS-CoV-2 antibody assay.

Data Collection
The demographic characteristics, clinical data, and results of cardiac biomarkers were obtained from the hospital's electronic medical records according to previously designed standardized data collection forms. The date of symptom onset, initial diagnosis of COVID-19, and death were recorded. The clinical features of symptoms and signs and comorbidities were collected on admission. Laboratory analyses included complete blood count, hepatic function, kidney function, coagulation function, Creactive protein (CRP), lactate dehydrogenase (LDH), myocardial enzymes, procalcitonin (PCT), electrolytes test, and status of other viral infection. Cardiac biomarkers including N-terminal pro-B-type natriuretic peptide (NT-proBNP), Hs-TnI, CK-MB, and myoglobin were measured on admission and during hospitalization. Routine bacterial and fungal examinations were also performed. Radiologic assessments included digital radiography (DR) and/or computed tomography (CT). Two researchers collected and checked the nal database.

De nitions
Fever was de ned as an axillary temperature of 37.5℃ or higher [10]. The date of onset was de ned as the day when any symptom was noticed. Myocardial injury was de ned as serum levels of Hs-TnI were above the 99th percentile upper reference limit at admission (0.04ng/mL, measured in the laboratory of Renmin Hospital of Wuhan University) [11]. The novel coronavirus pneumonia (NCP) types (mild, common, severe, critically severe) was de ned according to the diagnostic and treatment programme for SARS-CoV-2 issued by Chinese National Health Committee (version 7) [12]. The primary end point was COVID-19 associated death. Hospital discharge was allowed after the relieved clinical symptoms, normal body temperature for at least three days, signi cant improvement in radiological ndings, and at least two consecutive negative results shown by RT-PCR for COVID-19 [12].

Statistical analysis
Categorical variables are shown as frequency rates or percentages. Continuous variables as mean ± standard deviation (SD) or median (interquartile range [IQR]) as appropriate. Student's t test, Mann Whitney test, χ 2 test or Fisher exact test was used where appropriate to assess the difference between different cohorts. The Pearson correlation coe cient and Spearman rank correlation coe cient were used for correlation analysis. Survival curves were plotted using the Kaplan-Meier method between patients with and without myocardial injury. Univariate and multivariate Cox regression models were used to determine the independent risk factors for death in hospital. The NCP types was listed as rank variable. Statistical analysis was performed with SPSS, version 21.0 (IBM, USA). A two-sided P < 0.05 was considered statistically signi cant.

Results
A total of 304 hospitalized patients with COVID-19 were consecutively enrolled in our study, including 96 patients (31.6%) with myocardial injury and 208 patients (68.4%) without myocardial injury. The demographic and clinical characteristics of the patients are listed in Table 1. On admission, over half of the COVID-19 patients (198, 65.1%) had comorbidities, including hypertension (42.8%), diabetes (16.4%), and cardiovascular disease (16.1%), like coronary artery disease (10.5%), arrythmia (4.3%), and cardiomyopathy (0.7%). COVID-19 patients with myocardial injury were older, more males, and more likely to have preexisting comorbidities, and were associated with more severe presentation (critically severe, 26.0% vs 7.2%, all p < 0.001). On admission, the median leukocyte counts, neutrophil counts, platelet counts, hemoglobin, immunoglobulin G (IgG), IgM, IgA and complement 3 (C3) levels were all within the normal range in both groups (Table 2). However, signi cant differences were noted in neutrophil and platelet counts between the two groups (p < 0.001). Comparing with patients without myocardial injury, patients with myocardial injury had even lower CD3, CD4, CD8 counts, higher IL-6, CRP, and PCT levels (all p < 0.001), and CD3, CD4, CD8 counts showed strong correlations (R > 0.77) with lymphocytes counts and moderate correlations (R: -0.39~-0.45) with CRP levels ( Fig. 1). Log-transformed serum Hs-TnI levels in patients with COVID-19 correlated signi cantly with both log-transformed serum NT-proBNP levels (β = 0.37, p < 0.001) and serum urea nitrogen levels (β = 4.23, p < 0.001) (Fig. 2).  Regarding the cardiac, hepatic, renal and coagulation function (Table 2), patients with COVID-19 had increased Hs-TnI, PCT and Ddimer levels on admission and NT-proBNP during hospitalization compared to the normal reference values. Patients with myocardial injury showed elevated myoglobin, LDH, PCT, and D-dimer levels (all p < 0.001) compared to patients without myocardial injury. Figure 2 shows the dynamic change of NT-proBNP of COVID-19 patients from admission to hospitalization. Compared with those without myocardial injury, more COVID-19 patients with myocardial injury required oxygen inhalation; noninvasive ventilation, invasive mechanical ventilation, antibiotic treatment and hemoperfusion therapy (all p < 0.001) ( Table 3). However, intravenous immunoglobulin treatment (24.0% vs 47.6%, P < 0.001) was lower in patients with myocardial injury. The comparison of typical managements, comorbidities, complications and time duration from symptom onset to death were made in 20 random patients with myocardial injury or not (Fig. 3), which tells us that myocardial injury may be associated with more severe presentation.  (Table 3). In the univariable analysis, the mortality rate was signi cantly higher in patients with myocardial injury (63.5% vs 13.0%, P < 0.001, Table 3). The Kaplan-Meier survival curves indicate signi cant survival differences between the patients with or without myocardial injury (p < 0.001, Fig. 4)

Discussion
This study summarizes the clinical characteristics, laboratory, cardiac, and radiographic ndings in a large cohort of 304 hospitalized COVID-19 patients, and provides novel information of the prognostic value of pre-existing co-morbidities and myocardial injury. Myocardial injury, senior age, NCP types and CRP levels were independently associated with higher risk of mortality during hospitalization. The myocardial injury was probably associated with in ammation response. The prognostic value of elevated Hs-TnI in patients with COVID-19 should be of great interest to a broad readership, as a simple blood biomarker test was such a strong predictor of mortality and that sophisticated, expensive and time-consuming cardiac testing with CT and magnetic resonance imaging (MRI) are not needed.
With the high infectivity, COVID-19 has managed to supersede severe acute respiratory syndrome (SARS) in 2003 and Middle East respiratory syndrome (MERS) in 2012 in terms of death toll [13]. The median age was 65 years in our study, greater than previous studies (55.6 and 49 years) [9,14], mainly due to the severe clinical types and more comorbidities in our patient cohort tending to be older. This is supported by the evidence that the median age of patients is higher in group with myocardial injury than those without (70.5 vs 62.0 years). COVID-19 patients with myocardial injury were prone to develop severe types (77.0%), and more likely to have pre-existing comorbidities (79.2% vs 58.7%), like hypertension, cardiovascular disease and cerebrovascular disease, also con rmed by other studies [9,15]. Li et.al analyzed six studies involving 1527 COVID-19 patients with previous cardiovascular metabolic diseases, and indicated that this patient group may face a greater risk of developing into the severe condition and that the comorbidities can also greatly affect the prognosis of the COVID-19 [16].
In our study, COVID-19 patients with myocardial injury had obviously elevated myoglobin, and NT-proBNP levels, providing independent corroborating evidence of myocardial injury [17]. In addition, the correlations between Hs-TnI levels and NT-proBNP levels with urea nitrogen levels indicate multiorgan injury along with myocardial injury and worth early monitoring. In prior studies, no signi cant deviations in coagulation function from the normal range were found but some patients still presented with coagulation dysfunction [18,19]. Our study further validated this result, especially in patients with myocardial injury or in critically severe and severe type. Hence, we speculate that coagulation may be not a very important pathophysiological process in all patients with COVID-19. Only some critically ill patients demonstrated abnormal coagulation function and multiple organ dysfunction at the end stage. COVID-19 patients with myocardial injury need active treatments to delay or reverse the progression of disease, supported by the fact that the clinical presentation and the severity of COVID-19, as well as more comorbidities in patients with myocardial injury group. However, patients without myocardial injury received more intravenous immunoglobulin therapy than patients with myocardial injury, and this may be attributable to rapid progression of COVID-19 disease in the later cohort, which makes it too late to use intravenous immunoglobulin therapy.
Two prior studies indicated that there was a strong correlation between myocardial injury and prognosis of COVID-19 patients during hospitalization [8,9]. Adding to previous reports, our study further con rmed that myocardial injury, senior age, CRP levels and NCP types are all independent prognostic indicators of mortality in COVID-19 patient. Among these risk factors, myocardial injury, determined by serum Hs-TnI, was the strongest both as dichotomous and continuous variable. The Hs-TnI marker can be an ally for earlier identifying myocardial injury, rather than cardiac infarction, thus guiding timely intervention [7]. To date, the exact mechanism of cardiac involvement in COVID-19 remains under investigation. Current studies suggested immune change in patients with MERS [20], SARS [21] and in uenza [22], especially changes in peripheral blood T cells, which may contribute to understanding the characteristics, diagnosis, monitoring, prevention and treatment of the disease. Many investigations have already reported that the pathophysiology and outcomes of COVID-19 may be linked to dysregulation of immune response, presenting with lower lymphocyte counts, higher leukocytes counts and signi cantly reduced CD4 + and CD8 + T lymphocytes levels [23,24]. In our study, the CD3, CD4, CD8 counts correlated well with lymphocytes counts and CRP levels, and an elevated in ammation reaction (CRP) and suppressive immune response (CD4+, CD8+) in COVID-19 patients at admission. In addition, traditional cardiovascular risk factors such as diabetes and hyperlipidemia impact immune function, and conversely, dysregulated immunologic status corresponds with elevated risk of incident cardiovascular disease [25]. Another possible mechanism is the direct invasion via angiotensin converting enzyme 2 (ACE2) receptors in cardiovascular system [3]. In our study, we not only found that COVID-19 patients with comorbidities were associated with higher mortality, but also the CRP levels are signi cantly associated with mortality in multi-variate cox analysis, which indicated there would be in ammation reaction and this was associated with worse outcomes. In addition, IL-6 cytokines were elevated in COVID-19 patients with myocardial injury, justifying the emergence of and association with severity of in ammation, and immune-related markers, like CD3, CD4, CD8 molecules counts and lymphocyte counts were all reduced, more signi cant in patients with myocardial injury. It was reasonable to presume the invasive coronavirus may dysregulate the immune system, and further lead to severe damage to myocardial tissues. The data from all these studies taken together, suggest that clinicians should consider myocardial injury on presentation, NCP types and in ammation and immune dysregulation what caring for COVID-19 patients. The exact mechanism of myocardial injury merits further investigation, but the ndings presented here highlight the prognostic value in identifying myocardial injury with noninvasive biomarker testing on admission in COVID-19 patients and raise the possibility that providers should consider close management of immune response, in ammation and comorbidities in COVID-19 hospitalized patients.
We acknowledge some limitations in our study. First, this was a retrospective, single center study of patients admitted to hospital; multi-center investigations for a larger cohort would be better to assess the clinical characteristics and con rm the outcomes of myocardial injury after infection with COVID-19. Second, because of the logistical limitations at the onset of these emerging infections in Wuhan, some data, such as in ammation biomarker and imaging data were lacked on admission, which limits the further con rmation of potential mechanisms of myocardial injury. Third, the data in this study permit a preliminary assessment of the clinical course and outcomes of patients with COVID-19. The causes of death may involve multiple organ dysfunction in most cases, and it is di cult to differentiate the myocardial injury as the main and direct cause in an individual case. Long-term observation and prospective study design on the effectiveness of treatments speci c for the myocardial injury are needed.

Conclusions
In conclusion, myocardial injury is common in patients hospitalized with COVID-19. Patients with myocardial injury had more severe presentation and complex comorbidities. Furthermore, myocardial injury is independently associated with increased inhospital mortality in patients with COVID-19.

Declarations
Ethics approval and consent to participate: This study obtained approval from the Research Ethics Committee of the Renmin Hospital of Wuhan University, Wuhan, China (approval number: WDRY2020-K038). Written consent was obtained from all participants.

Consent for publication:
Not applicable.
Availability of data and materials: The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Competing interests
The authors declare that they have no competing interests