European Journal of Cardiovascular Medicine

Cardiac arrest remains a major cause of morbidity and mortality worldwide and continues to be a challenge for emergency physicians, anesthesiologists, intensivists, and resuscitation teams. Despite advances in cardiopulmonary resuscitation (CPR) protocols, survival rates following cardiac arrest remain suboptimal, with global survival to hospital discharge averaging between 10–20% for out-of-hospital cardiac arrests and approximately 25–40% for in-hospital cardiac arrests. A critical determinant of survival is the timely identification and correction of reversible causes, often described as the “Hs and Ts” in the Advanced Cardiac Life Support (ACLS) algorithm. These include hypoxia, hypovolemia, hydrogen ion imbalance (acidosis), hypo/hyperkalemia, hypothermia, tension pneumothorax, tamponade, toxins, and thrombosis (coronary or pulmonary).^[1]

Traditionally, ACLS relies on clinical assessment, history, physical findings, and basic investigations such as electrocardiogram (ECG), arterial blood gases, or bedside monitoring to identify these potentially reversible causes. However, in emergency situations, these assessments may be time-consuming, inconclusive, or impractical. For instance, differentiating between massive pulmonary embolism and myocardial infarction based solely on clinical findings and ECG changes during resuscitation may be extremely difficult. Similarly, pericardial tamponade or tension pneumothorax can be easily missed without direct imaging.^[2]

Point-of-Care Ultrasound (POCUS) has emerged as a valuable adjunct to resuscitation medicine, bridging the gap between clinical suspicion and rapid diagnosis. POCUS allows real-time, bedside evaluation of cardiac contractility, volume status, pericardial effusion, pneumothorax, and even indirect evidence of pulmonary embolism. Unlike traditional imaging modalities such as CT or echocardiography in radiology or cardiology suites, POCUS can be performed during ongoing resuscitation without significant interruption in chest compressions, thereby making it especially relevant in the context of cardiac arrest.^[3]

The integration of POCUS in cardiac arrest management has gained increasing attention over the last decade. Studies have demonstrated that focused echocardiography during cardiac arrest can provide prognostic information distinguishing true asystole from fine ventricular fibrillation or pseudo-PEA, help in procedural guidance pericardiocentesis, and improve diagnostic accuracy in identifying reversible causes. Protocols such as the FEEL (Focused Echocardiographic Evaluation in Life Support) and CASA (Cardiac Arrest Sonographic Assessment) have been developed to standardize ultrasound use during resuscitation. Despite these advantages, concerns remain regarding potential delays in chest compressions, operator dependency, and variable diagnostic accuracy across different levels of training.^[4][5]

Aim

To compare Point-of-Care Ultrasound (POCUS) with Standard Advanced Cardiac Life Support (ACLS) assessment in identifying reversible causes during cardiac arrest.

Objectives

1. To evaluate the diagnostic accuracy of POCUS compared with standard ACLS assessment in detecting reversible causes of cardiac arrest.
2. To determine the time taken for identification of reversible causes using POCUS versus standard ACLS assessment.
3. To assess the clinical impact of POCUS on management decisions during cardiac arrest resuscitation.

Source of Data

The study included patients presenting with cardiac arrest to the Emergency Department of a tertiary care teaching hospital. Both in-hospital and out-of-hospital cardiac arrest patients who were brought to the emergency and underwent resuscitation were included.

Study Design

This was a prospective, comparative, cross-sectional study conducted on patients undergoing resuscitation for cardiac arrest.

Study Location

The study was conducted in the Emergency Department and Critical Care Unit of a tertiary care teaching hospital.

Study Duration

The study was carried out over a period of 18 months (January 2023 to June 2024).

Sample Size

A total of 80 patients were enrolled and divided into two groups:

Group A (n = 40): Standard ACLS assessment.

Group B (n = 40): POCUS assessment in addition to ACLS protocol.

Inclusion Criteria

1. Adult patients (>18 years) presenting with cardiac arrest (in-hospital or out-of-hospital).
2. Patients in whom resuscitation efforts were initiated according to ACLS guidelines.
3. Patients for whom consent for study participation was obtained from relatives after stabilization or termination of resuscitation.

Exclusion Criteria

1. Patients <18 years of age.
2. Traumatic cardiac arrest cases.
3. Patients with do-not-resuscitate (DNR) orders.
4. Cases where POCUS could not be performed due to logistic or technical issues.

Procedure and Methodology

Patients presenting with cardiac arrest were immediately managed according to ACLS guidelines. In Group A (ACLS only), identification of reversible causes relied solely on standard ACLS clinical and biochemical assessment, including ECG, arterial blood gases, and clinical examination. In Group B (POCUS + ACLS), patients underwent additional point-of-care ultrasound examination performed by a trained emergency physician during pre-defined pauses in CPR or simultaneously during resuscitation when feasible.

POCUS protocols included:

Cardiac ultrasound (subxiphoid or parasternal view): To detect pericardial tamponade, cardiac activity, ventricular function, or massive pulmonary embolism (suggested by RV dilation).

Lung ultrasound: To assess for pneumothorax (absence of lung sliding, barcode sign on M-mode).

IVC assessment: For volume status and hypovolemia.

Abdominal FAST scan: For occult hemorrhage.

Findings were recorded, and any reversible cause identified was documented along with the time taken to detect it. The resuscitation team was allowed to act upon findings in real time.

Sample Processing

Data sheets were maintained for each patient, recording demographic details, clinical characteristics, resuscitation details, and findings from either ACLS-only assessment or ACLS+POCUS assessment. Reversible causes identified by either method were categorized (hypoxia, hypovolemia, tamponade, tension pneumothorax, thrombosis, toxins, electrolyte imbalance).

Statistical Methods

Data were entered in Microsoft Excel and analyzed using SPSS version 25. Continuous variables (e.g., time taken to identify cause) were expressed as mean ± standard deviation (SD) and compared using Student’s t-test. Categorical variables proportion of causes detected were expressed as percentages and compared using Chi-square test or Fisher’s exact test. A p-value <0.05 was considered statistically significant. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of POCUS compared to ACLS assessment were calculated.

Data Collection

Data were collected prospectively for each resuscitation event. A structured proforma was used to capture patient demographics, presenting event details, type of cardiac arrest rhythm, interventions performed, causes identified, and outcomes. All data were anonymized before statistical analysis.

Table 1: Comparison of POCUS vs Standard ACLS for Identifying Reversible Causes During Cardiac Arrest (n=40 per group)

Effect = difference in proportions; CI by normal approximation; z = two-sample proportion z-test.

Table 1 compared the ability of Point-of-Care Ultrasound (POCUS) and standard ACLS assessment to identify reversible causes during cardiac arrest. POCUS identified reversible causes in 72.5% of cases (29/40), which was significantly higher than the 42.5% detected by ACLS alone (p = 0.0044). This corresponds to an absolute increase of 30% (95% CI: 9.4–50.6%). Among individual conditions, POCUS detected more cases of pericardial tamponade (12.5% vs. 2.5%), tension pneumothorax (17.5% vs. 7.5%), and pulmonary embolism (12.5% vs. 2.5%), although these differences did not reach statistical significance, likely due to small sample sizes. Severe hypovolemia was slightly more frequently identified by POCUS (22.5% vs. 17.5%), but this difference was not significant (p = 0.5754).

Figure 1

Table 2: Diagnostic Accuracy vs Adjudicated Reference Standard (n=40 per group)

Reference standard determined by post-event adjudication. POCUS confusion matrix: TP=21, FN=3, FP=4, TN=12. ACLS: TP=13, FN=10, FP=5, TN=12. CIs for single proportions by Wilson; differences by two-sample z-tests.

Table 2 evaluated the diagnostic accuracy of POCUS compared to ACLS against an adjudicated reference standard. POCUS showed significantly higher sensitivity (87.5%, 95% CI: 69.0–95.7%) than ACLS (56.5%, 95% CI: 36.8–74.4%), with an absolute difference of 31% (p = 0.0121). Specificity was slightly higher with POCUS (75.0% vs. 70.6%), though the difference was not significant. The positive predictive value of POCUS (84.0%) was better than ACLS (72.2%), while the negative predictive value was substantially higher (80.0% vs. 54.5%), suggesting that POCUS was more reliable at ruling out reversible causes when absent. Overall diagnostic accuracy was significantly superior with POCUS (82.5% vs. 62.5%, p = 0.0398).

Figure 2

Table 3: Time Metrics for Identification and Action (n=40 per group)

Welch’s t-test and 95% CI for mean difference.

Table 3 analyzed time metrics related to identification and intervention. The mean time to identify the first reversible cause was significantly shorter with POCUS (3.9 ± 1.6 min) compared to ACLS (6.6 ± 2.3 min), with a mean difference of −2.7 minutes (95% CI: −3.58 to −1.82, p < 0.0001). Similarly, the time to first intervention following identification was also faster with POCUS (5.2 ± 2.1 min vs. 8.3 ± 2.7 min), with a mean reduction of 3.1 minutes (p < 0.0001). However, POCUS was associated with slightly longer CPR pauses per pulse check (9.6 ± 2.1 sec vs. 7.8 ± 1.9 sec, p = 0.00013). Although these pauses were longer, they remained within clinically acceptable ranges.

Figure 3

Table 4: Clinical Impact on Management Decisions and Outcomes (n=40 per group)

Table 4 assessed the clinical impact of POCUS on management decisions and outcomes. Use of POCUS led to a significantly higher rate of management changes during resuscitation (67.5% vs. 37.5%, p = 0.0049). POCUS also improved return of spontaneous circulation (ROSC: 57.5% vs. 37.5%), survival to hospital admission (47.5% vs. 27.5%), and survival to discharge (22.5% vs. 17.5%), though these differences did not reach statistical significance. Importantly, POCUS facilitated more critical procedures such as pericardiocentesis, decompression, or thrombolysis (32.5% vs. 12.5%, p = 0.0274).

Figure 4

Identification of reversible causes (Table 1): Primary endpoint “any reversible cause identified”-was significantly higher with POCUS than with standard ACLS (72.5% vs. 42.5%, absolute difference +30.0%, p=0.0044). This aligns with the original FEEL work, which demonstrated the feasibility of ALS-conformed echocardiography in the peri-resuscitation setting to uncover treatable etiologies (tamponade, probable PE, hypovolemia) and to alter management in a meaningful proportion of patients Zaki HA et al.(2024)^[6]. Similarly, the multicenter REASON/ED POCUS cohort found that ultrasound during cardiac arrest not only stratifies prognosis but also uncovers findings that prompt non-ACLS interventions pericardiocentesis in effusion associated with comparatively higher survival to admission Javaudin F et al.(2024)^[7]. Higher detection for tamponade, tension pneumothorax, and suspected PE trends in the same direction as these reports, although, as in prior studies, event counts for individual etiologies are modest and confidence intervals are wide. Narrative and consensus reviews continue to recommend integrating POCUS alongside the “Hs and Ts” to accelerate hypothesis-driven treatment while acknowledging operator dependence Kedan I et al.(2020)^[8] & Dudek M et al.(2023)^[9].

Diagnostic accuracy (Table 2): Study shows materially greater sensitivity (87.5% vs. 56.5%) and higher overall accuracy (82.5% vs. 62.5%) for POCUS relative to standard assessment. This is directionally consistent with evidence that intra-arrest ultrasound improves the detection of clinically relevant pathology and with meta-analytic data linking sonographic cardiac activity to better odds of ROSC, survival to admission, and survival to discharge in non-traumatic, non-shockable arrests Reynolds JC et al.(2022)^[4]. At the same time, high-quality systematic reviews focused specifically on diagnostic test accuracy caution that evidence for identifying the exact etiology of arrest remains heterogeneous, with risks of bias and imprecision that limit certainty particularly for PE inference by right-heart findings and for pneumothorax so favorable accuracy should be interpreted in light of these caveats Lalande E et al.(2019)^[10]. This dovetails with ILCOR’s Advanced Life Support CoSTR, which highlights that although intra-arrest POCUS may be informative, diagnostic claims during CPR should be tempered and weighed against potential harms -  interruptions.

Time metrics and CPR pauses (Table 3): POCUS markedly shortened the time to first identification (mean −2.7 min) and to first intervention (mean −3.1 min), reinforcing its value as a rapid, bedside diagnostic adjunct when implemented by trained teams. Modest increase in pulse-check pause duration (+1.8 s) is smaller than earlier reports linking POCUS use to clinically significant prolongations (≈+6–8 s) in real-world ED arrests Badra K et al.(2019)^[11]. The difference is plausibly explained by structured implementation and technique probe pre-positioning, image acquisition during planned pauses, which the CASA protocol demonstrated can reduce ultrasound-associated pauses after targeted training and standardized choreography Leviter JI et al.(2024)^[12].

Management decisions and outcomes (Table 4): Observed significantly more management changes with POCUS (67.5% vs. 37.5%) and higher rates of critical procedures pericardiocentesis, needle decompression, thrombolysis (32.5% vs. 12.5%). This echoes FEEL’s prospective data showing that incorporating focused echocardiography identified treatable pathology and altered on-scene care Martinez EC et al.(2023)^[13] and mirrors the multicenter finding that POCUS can surface non-ACLS interventions, with pericardiocentesis in effusion linked to comparatively improved survival to admission Goudie A et al.(2024)^[14]. ROSC and early survival in cohort trended higher with POCUS, consistent with meta-analytic associations between sonographic cardiac activity and survival benchmarks, though as in prior literature survival to discharge often fails to reach statistical significance because outcomes depend on myriad post-resuscitation factors Heikkilä E et al.(2023)^[15].

This comparative study demonstrated that Point-of-Care Ultrasound (POCUS) significantly improved the identification of reversible causes during cardiac arrest compared with standard Advanced Cardiac Life Support (ACLS) assessment. POCUS identified reversible etiologies in 72.5% of patients, an absolute increase of 30% over ACLS alone. It also showed superior diagnostic sensitivity (87.5% vs. 56.5%) and overall accuracy (82.5% vs. 62.5%). Importantly, POCUS enabled faster recognition and intervention, reducing time to diagnosis and treatment by nearly three minutes, albeit at the expense of slightly longer pulse-check pauses, which remained clinically acceptable. Moreover, POCUS facilitated more management changes and critical procedures, with trends toward higher rates of ROSC and survival to admission, though survival to discharge did not differ significantly. Overall, POCUS, when integrated into resuscitation protocols, represents a valuable adjunct that enhances diagnostic accuracy, accelerates therapeutic decision-making, and improves the likelihood of identifying treatable causes in cardiac arrest.

LIMITATIONS

1. Sample size – The relatively small number of patients (40 per group) limited statistical power, particularly for subgroup analysis of individual reversible causes such as tamponade, pneumothorax, and pulmonary embolism.
2. Single-center study – Conducted in a tertiary care hospital, which may limit generalizability to community hospitals or prehospital settings.
3. Operator dependency – POCUS accuracy relies heavily on the skill and experience of the physician, introducing variability in diagnostic outcomes.
4. Potential interruption to CPR – Despite structured implementation, POCUS caused slightly longer CPR pauses, which may influence outcomes in less experienced teams.
5. Outcome assessment – While ROSC and admission survival were measured, ultimate survival to hospital discharge and neurological outcomes were not significantly different, limiting assessment of long-term benefit.
6. Logistical constraints – Equipment availability and real-time interpretation challenges may limit widespread adoption in resource-limited settings.

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