Implications of Cardiac Markers in Risk-Stratification and Management for COVID-19 Patients

Pengping Li; Wei Wu; Tingting Zhang; Ziyu Wang; Jie Li; Mengyan Zhu; Yuan Liang; Wenhua You; Kening Li; Rong Ding; Bin Huang; Lingxiang Wu; Weiwei Duan; Yi Han; Xuesong Li; Xin Tang; Xin Wang; Han Shen; Qianghu Wang; Hong Yan; Xinyi Xia; Yong Ji; Hongshan Chen

Disclosures

Crit Care. 2021;25(158) 

In This Article

Results

Baseline Clinical Characteristics

Of the initial 3046 patients with COVID-19 enrolled in our study, 48 patients with no record of survival status, 29 patients without classification of disease severity, and 15 patients with suspected CAD but with no diagnosis were excluded. In the remaining cohort of 2954 patients, 1439 patients were mild/moderate cases and 1515 were severe/critical cases. Among 1439 mild/moderate cases, 71 had CAD. 538 severe/critical cases had complete biomarker data during hospitalization, of which 79 had CAD (Figure 1a).

Among the final cohort of 2954 patients, the median age was 60 years (range 50–68 years), 1461 (49.5%) were female, and 1515 (51.3%) were severe/critical cases. The median hospital stay for severe/critical (S) patients was significantly longer than that for mild/moderate (M) cases. Compared with mild/moderate cases, severe/critical patients were more likely to experience chest tightness. Comorbidities were more prevalent among severe/critical patients compared to mild/moderate cases, including hypertension, diabetes, cardiovascular disease, cerebrovascular disease, cancer, and chronic obstructive pulmonary disease (Table 1).

In terms of radiological and laboratory findings, severe/critical (S) patients had more incidences of blurred edges and consolidation (Table 1) and significantly higher levels of C-reactive protein (CRP), D-dimer, interleukin-6 (IL-6), procalcitonin (PCT), and higher percentages of neutrophils (NEUT%), lymphocytes (LYM%), and monocytes (MONO%) within the first week of admission (Figure 2). Serum cardiac markers, namely; BNP, hs-TNI, α-HBDH, CK-MB, and LDH, were also drastically elevated in severe/critical patients during the first week (Figure 2). In general, the results showed more pronounced activation of pathophysiological pathways in more severe cases of COVID-19.

Figure 2.

Serum cardiac markers drastically elevated in severe/critical patients during the first week. Levels of 12 multiple organ dysfunction indicators in mild/moderate (M) and severe/critical (S) groups during the first week of hospitalization. The difference of each indicator between the two groups is significant (two-sided Wilcoxon test, P < 0.001)

Cardiac Markers and Clinical Outcomes

To evaluate the relationship between the degree of cardiac abnormality and disease outcome in patients with COVID-19, serum cardiac markers during hospitalization were measured. Due to the 0% mortality and favorable prognosis of mild/moderate patients, we focused on the 1,515 patients with severe/critical COVID-19 in the follow-up period.

Five cardiac biomarkers, namely, BNP, hs-TNI, α-HBDH, CK-MB, and LDH, were collected to evaluate heart function. For the detection of BNP, 1456 samples from 835 patients were tested during hospitalization. Each patient was tested 1 to 19 times, and 281 (33.6%) were tested more than once. The median sampling interval was 4 days among patients who were tested more than once. For the detection of α-HBDH and LDH, 3900 samples from 1443 patients were tested. Each patient was tested 1 to 27 times, and 835 (57.9%) were tested more than once. The median sampling interval was 4 days among patients who were tested more than once. For the detection of total CK-MB, 3885 samples from 1442 patients were tested. Each patient was tested 1 to 27 times, and 834 (57.8%) were tested more than once. The median sampling interval was 4 days among patients who were tested more than once. For the detection of total hs-Tnl, 1126 samples from 660 patients were tested. Each patient was tested 1 to 18 times, and 209 (31.6%) were tested more than once. The median sampling interval was 4 days among patients who were tested more than once. A total of 538 critical/severe patients had all five cardiac markers measured during hospitalization.

In total, 171 (20.5%), 79 (12.0%), 529 (36.7%), 124 (8.6%), and 447 (3.1%) patients showed abnormal serum levels of BNP, hs-TNI, α-HBDH, CK-MB, and LDH, respectively (Figure 3a). Patients with an elevated level of a cardiac marker during hospitalization showed a significantly higher mortality than those with normal serum levels (Figure 3b). The same trend was observed in the ICU admission rate (Figure 3c).

Figure 3.

Severe/critical COVID-19 patients with evidence of abnormal cardiac markers have poor clinical outcomes. a Number of patients with abnormal and normal levels of BNP, hs-TNI, α-HBDH, CK-MB, and LDH during hospitalization. The mortality (b) and ICU admission rate (c) of severe/critical COVID-19 patients with abnormal serum levels of BNP, hs-TNI, α-HBDH, CK-MB, and LDH during hospitalization. d Number of patients with abnormal and normal levels of BNP, hs-TNI, α-HBDH, CK-MB, and LDH within the first week after admission. The mortality (e) and ICU admission rate (f) of severe/critical COVID-19 patients with abnormal serum levels of BNP, hs-TNI, α-HBDH, CK-MB, and LDH within the first week after admission. g Serum levels of BNP, hs-TNI, α-HBDH, CK-MB, and LDH during hospitalization for non-survivors and survivors. Shaded regions represent a 95% confidence interval

When considering detection data within the first week after admission, BNP, hs-TNI, α-HBDH, CK-MB, and LDH were detected in 706 patients, 551 patients, 1345 patients, 1342 patients, and 1345 patients, respectively. 125 (17.8%), 52 (9.4%), 470 (35.0%), 78 (5.8%), and 385 (28.7%) patients showed abnormal serum levels of BNP, hs-TNI, α-HBDH, CK-MB, and LDH (Figure 3d). Patients with an elevated level of cardiac markers within the first week after admission also showed a significantly higher mortality (Figure 3e) and ICU admission rate than those with normal serum levels (Figure 3f). Figure 3g shows that the serum levels of BNP, hs-TNI, α-HBDH, CK-MB, and LDH were significantly higher during hospitalization in non-survivors than in survivors. The results represented patients having abnormal level of cardiac markers within the first week after admission and during hospitalization may predict deterioration or progression.

Expression of SARS-CoV-2 Receptors in Heart Tissue of non-COVID-19 Cohorts

The scRNA-seq data of normal human heart tissue were analyzed and five cell types, namely, cardiomyocyte (CM), endothelial (EC), fibroblast (FB), macrophage (MP), and smooth muscle (SMC) cells, were identified (Figure 4a). SARS-CoV-2 receptors ACE2, ANPEP, DPP4, and ENPEP were enriched in specific cell populations. ACE2 was mainly expressed in CM, EC, and FB cell types. ANPEP was enriched in CM, DPP4 was mainly expressed by CM and EC, and ENPEP was primarily expressed in CM and SMC (Figure 4b, c).

Figure 4.

scRNA-seq analysis of SARS-CoV-2 receptors in heart specific cell populations. a The t-distributed Stochastic Neighbor Embedding (t-SNE) diagram shows the main cell types in healthy heart tissue. Each dot represents a cell, and each color represents a cell type. b Feature maps and c violin diagrams show SARS-CoV-2 receptors are enriched in specific cell populations in healthy heart tissues

Cardiac Markers and Mortality Rate in Patients With CAD or not

The 1,515 severe/critical patients were further categorized into groups according to the presence of pre-existing CAD (n = 165) or absence (n = 1350). Compared with patients without CAD, patients with pre-existing CAD had a higher percent of elevated BNP (52 [46.4%] vs 119 [16.5%]), hs-TNI (24 [26.7%] vs 55 [9.7%], α- HBDH (86 [55.6%] vs 443 [34.4%]), CK-MB (27 [17.4%] vs 97 [7.5%]), and LDH (65 [41.9%] vs 382 [29.7%]) during hospitalization (P < 0.01 for all results, (Figure 5a). Compared to patients with normal levels of cardiac markers, those with abnormal levels of BNP, hs-TNI, α-HBDH, CK-MB, and LDH during hospitalization exhibited significantly higher mortality in both CAD and non-CAD groups (P < 0.001 for all results; Figure 5c). The same trend was observed for the ICU admission rate (Additional file 2: Figure S1). The serum markers were then compared between non-survivors and survivors. The results showed that BNP, α-HBDH, CK-MB, and LDH were significantly higher in non-survivors than in survivors for patients with pre-existing CAD (Figure 5d). In patients without pre-existing CAD, all markers were significantly higher in non-survivors than in survivors during hospitalization (Figure 5e).

Figure 5.

Severe/critical COVID-19 patients with abnormal cardiac markers exhibited higher mortality. a Percent of abnormal cardiac markers in patients with and without pre-existing CAD. b Expression of SARS-CoV-2 receptors, TMPRSS2 and ENPEP, in coronary artery disease and healthy controls. c The mortality rate of COVID-19 patients with cardiac markers abnormality. de Median levels of cardiac markers in survivors and non-survivors during hospitalization. ***P < 0.001; NS: not significant

SARS-CoV-2 Receptors in CAD and Healthy Controls of non-COVID-19 Cohorts

To explore the underlying pathophysiological mechanism for the elevated levels of cardiac markers in COVID-19 patients with pre-existing CAD, RNA-seq data from 93 patients with CAD and 48 healthy people were analyzed and compared. The results showed that compared with healthy controls, SARS-CoV-2 receptors, including Transmembrane Serine Protease 2 (TMPRSS2, P = 0.009) and Glutamyl Aminopeptidase (ENPEP, P = 0.012), were significantly upregulated in CAD (Figure 5b).

Cardiac Markers in Non-survivors With CAD or not

Notably, the median value of BNP was significantly higher in non-survivors than in survivors for those with pre-existing CAD (911.3 pg/mL vs. 57.9 pg/mL) and those without (121 pg/mL vs. 0.01 pg/mL) on the first day after admission. The median levels of hs-TNI, α-HBDH, and LDH were significantly higher in non-survivors than in survivors in patients without pre-existing CAD; however, a significant difference was not observed in patients with pre-existing CAD (Additional file 3: Figure S2).

In non-survivors with pre-existing CAD, the median levels of BNP and hs-TNI within the first week showed a higher fold change (BNP: 5.8; hs-TNI: 7.5; α-HBDH: 1.9; CK-MB: 0.81; LDH: 1.7) from the upper reference limit of each marker (Figure 6a). In non-survivors without pre-existing CAD, the fold change for BNP, hs-TNI, α-HBDH:1.9, CK-MB, LDH was 1.4, 1.7, 2, 0.78, and 1.9, respectively (Figure 6b). The serum level differences for the five markers within a week after admission in patients with or without pre-existing CAD showed that BNP, α-HBDH, and LDH values were significantly higher in non-survivors than in survivors regardless of pre-existing CAD (Figure 6c, d). Levels of hs-TNI were significantly higher only in non-survivors than in survivors for patients without pre-existing CAD. Although CK-MB were significantly different between non-survivors and survivors, most data for non-survivors were within normal levels (Figure 6c, d). The change of five markers levels was the same as those mentioned above during hospitalization (Additional file 4: Figure S3).

Figure 6.

Risk-Stratification Biomarker for COVID-19 patients. a–b Fold change of cardiac markers relative to the upper reference within one week after admission. c–d The fluctuation of serum levels of cardiac markers within one week after admission. CAD: COVID-19 patients with pre-existing CAD; non-CAD: COVID-19 patients without pre-existing CAD

Elevated Cardiac Markers and Increased Mortality

The mortality between patients with high and normal cardiac markers within the first week after admission that were not in the ICU were analyzed. When we retrieved patients' electronic medical records, we found 4 patients with elevated five markers were not admitted into ICU and 3 patient died. Conversely, 217 patients with normal level of five cardiac markers were not admitted into ICU and 0 died. The results demonstrated the mortality of patients with elevated five cardiac markers not admitted to ICU was significantly higher than those with normal cardiac markers not admitted to ICU (Fisher exact test, P < 0.0001). Additionally, 90 patients with elevated BNP, 32 patients with elevated hs-TNI, 382 patients with elevated α-HBDH, 47 patients with elevated CK-MB and 305 patients with elevated LDH within the first week were not admitted to ICU, respectively (Additional file 1: Table S1, Figure 3f).

In order to evaluate the risk of elevated levels of cardiac markers in COVID-19 patients as early as possible, we established a prognosis prediction model based on levels of BNP, hs-TNI, α-HBDH, CK-MB, and LDH within the first week after admission. Firstly, univariate Cox regression analysis was conducted by applying a mixed-effect Cox model adjusted for age, sex, comorbidities for each cardiac marker. Patients with missing values for each marker were removed. We identified five markers were independent predictor of mortality (P < 0.001, Additional file 5: Figures S4 and S5). Secondly, to predict the risk of mortality more accurately, five markers were entered into a multivariate Cox regression analysis. Samples with missing values in any marker were removed and 429 patients have five cardiac markers detections were included in the subsequent analysis. We divided 429 patients into cardiac markers abnormal (n = 79) and normal (n = 350) groups based on the upper reference limit. As a result, the five cardiac markers abnormal group demonstrated a significantly higher risk of mortality with hazards ratio 3.4 [95% CI, 2.4–4.8] (Figure 7a). Five cardiac markers levels classified survivors and non-survivors with an area under the curve (AUC) of 0.90 with the threshold value based on the ROC curve of 1.5, a sensitivity of 70.6%, and a specificity of 96.4% (Figure 7b).

Figure 7.

Abnormal levels of five cardiac makers is correlated with increased mortality of COVID-19 patients. a Kaplan–Meier estimates for severe/critical patients by levels of BNP, hs-TNI, α-HBDH, CK-MB, and LDH within the first week after admission in multivariate Cox regression analysis. Log-rank test shows statistical significance. The table below shows the number of people still alive at different time points. b ROC curve of five cardiac markers to predict survivors and non-survivors

CRP, D-dimer, and IL-6 are commonly elevated and LYM% diminished in patients with COVID-19 and correlate with disease severity in previous studies. We analyzed the correlation between five cardiac barkers and CRP, D-dimer, IL-6, and LYM%. The results showed BNP, hs-TNI, α-HBDH, CK-MB, and LDH were highly positive correlation with CRP, IL-6, and D-dimer (Additional file 7: Figure S6). By contrast, five markers were significantly negatively correlated with LYM% (Figure S6).

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