Is two-dimensional echocardiography better than electrocardiography for predicting patient outcomes after cardiac arrest?

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Acute Crit Care. 2021;36(1):37-45

Publication date (electronic) : 2020 December 21

doi : https://doi.org/10.4266/acc.2020.00773

Dong Ki Kim, Yong Soo Cho, Joochan Kim, Byung Kook Lee, Dong Hun Lee, Eujene Jung, Jeong Mi Moon, Byeong Jo Chun

Department of Emergency Medicine, Chonnam National University Hospital, Gwangju, Korea

Corresponding author Yong Soo Cho Department of Emergency Medicine, Chonnam National University Hospital, 42 Jebong-ro, Dong-gu, Gwangju 61469, Korea Tel: +82-62-220-6809 Fax: +82-62-228-7417 E-mail: semi-moon@hanmail.net

Received 2020 September 24; Revised 2020 November 26; Accepted 2020 December 4.

Abstract

INTRODUCTION

The most common cause of cardiac arrest (CA) is acute coronary syndrome (ACS), which accounts for 70% of all CA cases [1-3]. Coronary angiography (CAG) improves both survival and neurological outcomes in CA patients [3-5]. The current guidelines for CA patients recommend that immediate CAG be performed on patients with ST segment elevation (STE) on electrocardiography (ECG); if STE is not detected, CAG should be performed considering account instability, comorbidities, and patient characteristics [5].

In ACS patients, ECG is helpful for prediction of patient outcomes. In several studies of ACS patients who underwent primary percutaneous coronary intervention (PCI), STE was associated with poorer survival-to-hospital discharge rates [6-8]. These results are similar to those in CA patients. In a previous study [9], CA patients who underwent CAG had a low incidence of survival-to hospital discharge when STE was not present because ECG detects coronary artery stenosis. The presence of coronary artery stenosis increases in-hospital mortality rates and leads to poor neurological recovery in CA patients [9]. However, the ability of ECG to predict coronary artery stenosis in CA patients is limited [3,10-12].

When diagnosing coronary artery stenosis in ACS patients, regional wall motion abnormality (RWMA) assessment using two-dimensional echocardiography (2DE) is more useful than STE assessment using ECG [13,14] because RWMA assessment is more sensitive to coronary artery stenosis [11,15]. As in ACS, if RWMA assessment is more capable of diagnosing coronary artery stenosis in CA patients than is STE assessment, it may predict the outcomes of CA patients with greater accuracy than STE assessment using ECG. We investigated whether RWMA assessment using 2DE could predict prognosis more effectively than STE assessment using ECG in CA patients who underwent CAG after return of spontaneous circulation (ROSC).

MATERIALS AND METHODS

Study Design and Patients

This was a retrospective observational study of adult CA survivors who were treated at Chonnam National University Hospital in Kwangju, Korea, between January 2006 and December 2018. This study was approved by the Institutional Review Board of the Chonnam National University Hospital (IRB No. CNUH-2020-104); the need for informed consent was waived.

Adult (age ≥18 years) CA patients with presumed cardiac etiology who underwent ECG, 2DE, and CAG immediately after ROSC were included in the study. In patients with CA, including out-of-hospital cardiac arrest (OHCA) and in-hospital cardiac arrest, cardiac etiology was defined as follows [16-18]: CA was presumed to be of cardiac etiology unless it was known or likely to have been caused by trauma, submersion, drug overdose, asphyxia, exsanguination, or any other noncardiac cause as best determined by rescuers. No patients who did not undergo CAG were enrolled in the study because they either died shortly after ROSC or their caregivers withdrew them from treatment. The exclusion criteria were as follows: (1) 2DE performed after CAG and (2) CAG performed at least 24 hours after ROSC [5,9,10] (Figure 1). A total of 145 patients was enrolled.

Figure 1.

Flowchart of the patient selection process. ECG: electrocardiography; TTE: transthoracic echocardiography; CAG: coronary angiography; 2DE: two-dimensional echocardiogram; STE: ST elevation; RWMA: regional wall motion abnormality.

RESULTS

Among 145 patients, in-hospital death was observed in 36 (24.8%) (Figure 1), good neurological outcome was observed in 78 (53.8%), and significant stenosis of the coronary artery was observed in 76 (52.4%). The flowchart is shown in Figure 1. In all patients, ECG was performed immediately after the visit, 2DE was performed at 151 minutes (interquartile range, 5 minutes to 589 minutes), and CAG was performed at 318 minutes (interquartile range, 151 minutes to 789 minutes). During 2DE, 105 patients (72.4%) had RWMA. On ECG, 61 patients (42.1%) had STE (Table 1). The incidence of STE differed significantly between the survival and death groups (P=0.037), while RWMA incidence showed no difference between groups (P=0.853). In terms of good neurological outcomes, no difference was observed between RWMA and STE (P=0.995, P=0.817). The incidence of significant coronary artery stenosis was significantly different between the RWMA and STE groups (P<0.001, P=0.004). Other variables related to prognosis of CA patients, such as age, sex, medical history, presence of a witness, CPR administration by a bystander, initial shockable rhythm, and total arrest time, did not differ between the STE and RWMA groups (Table 1).

Table 1.

Demographic findings of the study population according to 2DE and ECG findings

In univariable analysis of survival, total arrest time, hypertension, OHCA, troponin-I, NT-proB-type natriuretic peptide, and STE had P-values < 0.2, and a multivariable analysis using these variables revealed that only total arrest time (P=0.011) and STE (P=0.035) were significant. The OR and 95% CI obtained after adjusting for significant variables in the multivariable analysis of survival outcomes were only significant for STE (OR, 0.40; 95% CI, 0.17–0.94) (Table 2). In the multivariable analysis of good neurological outcomes, only sex (P=0.013), initial shockable rhythm (P<0.001), and total arrest time (P<0.001) were significant (Table 3). Neither STE nor RWMA was a significant predictor of good neurological outcomes. In the multivariable analysis of stenosis, age (P=0.021), sex (P=0.045), and RWMA (P<0.001) were significant. The OR and 95% CI for stenosis were significant for RWMA (OR, 6.07, 95% CI, 2.37–15.54) (Table 4). The demographic findings of RWMA and no-RWMA in 84 no-STE patients are shown in Supplementary Table 1. In the multivariable analysis, RWMA was only significant for stenosis (OR, 6.01; 95% CI, 1.78–20.21), and there were no significant differences in survival and neurologic outcomes between the two groups (Supplementary Table 2).

Table 2.

Logistic regression analysis for survival outcomes

Table 3.

Logistic regression analysis for good neurological outcomes

Table 4.

Logistic regression analysis for coronary artery stenosis

DISCUSSION

STE was independently associated with survival outcomes, whereas RWMA was not. Both STE and RWMA were independent predictors of coronary artery stenosis but not of neurological outcomes.

In the multivariable analysis, total arrest time and STE were significant predictors of survival outcomes. After adjusting for total arrest time, the OR for STE was 0.37 (95% CI, 0.17–0.83). In a previous study [9] of patients with CA, the survival-to-hospital discharge rate was 55.1% (109/198) for all patients with STE, higher than the rate of 41.3% (226/547) in patients without STE (adjusted P=0.007). However, in patients who underwent CAG, the survival-to-hospital discharge rate was 55.7% (107/192) when STE was found and 66.8% (165/247) when it was not (adjusted P=0.01). We studied patients who underwent CAG, and survival was poor when STE was present, consistent with the findings of the previous study [9]. This is likely due to the association of coronary artery stenosis with mortality in CA patients.

In the multivariable analysis of significant coronary artery stenosis, only RWMA and STE were significant. RWMA had a higher OR than STE; however, this did not lead to improved survival. Several studies have shown that it is PCI, not CAG that reduces mortality in CA patients [3,9,11,26,27]. Therefore, CAG is only recommended after CA in patients with significant coronary artery stenosis. However, it is not easy to predict stenosis before CAG [1,10-12,28] because the clinical signs for ischemia caused by significant stenosis are unclear, and the available diagnostic tools are of limited use [1,10-12]. ECG, the most widely-used tool, is a poor predictor of significant stenosis in CA patients [3,10-12]. Significant stenosis was not observed in 20% of STE patients, while it was observed in 25% of patients without STE. This finding suggests the need for further research using other diagnostic tools [3,29]. We assessed the presence of RWMA on 2DE, which is superior to ECG for diagnosis of significant coronary artery stenosis in ACS patients. However, in our study of CA patients, the presence of RWMA did not predict patient survival. This suggests that the characteristics of RWMA differ between CA and ACS.

In the present study, RWMA was observed in 105 patients, whereas STE was observed in 61 patients. This suggests that RWMA can detect stenosis unrelated to survival. In addition, the accuracy of RWMA assessment can decrease due to the presence of Takotsubo syndrome [30], which can occur after CA and is difficult to distinguish from RWMA on 2DE. Postresuscitation myocardial dysfunction (PRMD) occurring after CA can further reduce the accuracy of RWMA assessment. PRMD is reversible myocardial dysfunction caused by global ischemia that occurs during CA, and global myocardial dysfunction is the most common pattern [31,32]. PRMD might have influenced the results of this study and can hinder the ability of physicians to identify RWMA.

In general, cardiac enzymes, such as troponin, predict coronary stenosis and patient outcomes. However, troponin did not show any significant relationships in our study. This observation is consistent with previous reports demonstrating that troponin has a high rate of false negative results (2.5%–7.8%) and is not useful in patients with CA, in contrast with patients with ACS [11]. The treatment strategy for patients with ROSC after CA typically involves CAG and TTM [5]. TTM results in better prognosis when initiated shortly after ROSC, but the optimal timing of CAG, especially in non-ST-elevation myocardial infarction (NSTEMI) patients, remains controversial [2,3,19]. In recent studies of NSTEMI, performing CAG shortly after CA did not show any clear benefit in terms of prognostic measures such as 30-day mortality [2,3,19,29]. In CA patients, CAG also has disadvantages, such as hemodynamic instability, exposure to contrast, and delays in appropriate diagnosis of other possible causes of CA, which can result in incorrect therapeutic decisions [19,29].

We hypothesized that RWMA assessment would help determine whether early CAG should be performed in patients without STE but found that RWMA was a useful predictor of significant coronary artery stenosis rather than of survival outcomes. Therefore, the benefits of 2DE in CA patients were limited. We chose to include only patients who had undergone 2DE prior to CAG. In patients who underwent 2DE after CAG, RWMA findings could differ due to successful PCI. However, we aimed to avoid preconceptions regarding interpretation of RWMA by the cardiologist, a potential consequence of knowing CAG results in advance.

The present study has several limitations. STE was defined according to the Fourth Universal Definition of Myocardial Infarction, so ECG results such as left main or post infarction were classified as no-STE. However, some clinicians have different opinions about these classifications. In our hospital, ECG is performed immediately after arrival at the ED. If STE is observed, CAG is performed as quickly as possible; if there is no STE, the decision to perform CAG is based on patient instability, comorbidities, and characteristics. In the ED, 2DE is performed at bedside during CAG preparation. In our study, STE patients only underwent 2DE if it did not interfere with CAG initiation; thus, selection bias could have been introduced. Since bias is greater in STE, we conducted further analyses of patients with no-STE in an attempt to reduce the impact of this limitation. In addition, since we only targeted patients who underwent CAG, it is possible that patients were selected under the presumption that CAG would be advantageous to their respective prognoses. Our study was limited by the different timings of 2DE and CAG execution. In the future, multicenter trials that address the timing of various procedures in CA patients, such as optimal timing of 2DE implementation, should be conducted.

In conclusion, both RWMA and STE are helpful for prediction of significant coronary artery stenosis. However, while STE predicted survival, RWMA did not. The decision to perform CAG after CA should include ECG results under the existing guidelines. The use of RWMA has limited benefits in treatment of this population.

KEY MESSAGES

SUPPLEMENTARY MATERIALS

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