Critical Care Alert: The CT FIRST Cohort Study

ARTICLE: Branch KRH, Gatewood MO, Kudenchuk PJ, et al. (2023). Diagnostic yield, safety, and outcomes of Head-to-pelvis sudden death CT imaging in post arrest care: The CT FIRST cohort study. Resuscitation. 2023;109785.

OBJECTIVE

To determine whether head-to-pelvis CT for post-cardiac arrest patients improves diagnostic yield as well as the time to identify the cause(s) for out of hospital cardiac arrest (OHCA)

BACKGROUND

OHCA is common globally, occurring in 82.1 per 100,000 people, or 3.8 million people per year on average worldwide. Of these individuals, only about 8-12% survive to hospital discharge.¹ Currently, when patients arrive to the hospital after an OCHA with no identifiable cause for the arrest, the standard of care includes obtaining an EKG, chest x-ray, CT head, metabolic evaluation via lab work, and an echocardiogram with all other CT scans left to the discretion of the treating physician.² Multiple studies have evaluated the utility in various combinations of CT scanning in post OHCA patients. One prospective, observational cohort study performed by Karatasakis, et al. studied the use of head-to-pelvis CT in post-OHCA patients within 6 hours of resuscitation to detect injuries associated with resuscitation and time-critical diagnoses. They found that 81% of patients had post-resuscitation associated injuries with 14% of patients having time-critical diagnoses which included liver or spleen laceration, pneumothorax, pulmonary laceration or hemorrhage. These findings lead to down-stream interventions in 87% of patients identified to have time-critical diagnoses including further imaging, surgical consultation, blood transfusions, chest and abdominal drain placement and repositioning of the endotracheal tube.³ Additionally, a retrospective review by Chelly et, al. demonstrated that performance of a CT chest or coronary angiography at the time of admission for post OHCA patients identified a cause for the arrest in 59% of cases.⁴ These studies further emphasize the utility of CT scanning in post-cardiac arrest patients, both in order to identify causes for cardiac arrest as well as to help direct post-resuscitation care.

Previously, the authors of the CT FIRST cohort study had performed an observational study and had found that head to pelvis CT scan post-cardiac arrest identified a cause for OHCA in 39% of patients and identified a high proportion of patients with resuscitation complications. In this prospective, observational, pre-cohort study, the authors studied survival and patient safety outcomes of the sudden death CT (SDCT) cohort to further understand the protocol’s diagnostic utility.

DESIGN

• Prospective, observational, pre-cohort and post-cohort study of patients successfully resuscitated from, at time of randomization, idiopathic OHCA from January 2014 - February 2018 at two academic hospitals
• The pre-cohort (standard of care [SOC] alone) cohort included patients successfully resuscitated from OHCA from January 2014 to December 2015 whereas the post- or SDCT-cohort included patients that underwent a head-to-pelvis sudden death CT (SDCT) scan in addition to the standard of care from December 2015 to February 2018. The SDCT scan protocol consisted of three CT scans:

1. A non-contrast CT head
2. Retrospective ECG-gated thoracic CT contrast angiogram for most of the cardiac cycle
3. Non-ECG gated venous phase abdominal and pelvic CT

• Potential causes for the OHCAs were adjudicated by two independent physicians with access to all patient records, including the SDCT and the most likely cause was considered the clinical diagnosis for the OHCA event. “Time-critical” diagnoses were defined a priori to the study and included acute coronary syndrome or obstructive coronary disease (≥50% coronary stenosis in a major coronary artery), pulmonary embolism, aortic dissection, pneumothorax, cerebrovascular accident (hemorrhagic or thrombotic), abdominal catastrophe, pneumonia (excluding presumed resuscitation aspiration), and critical resuscitation complications of internal or organ bleeding.

INCLUSION CRITERIA

• Unknown cause for cardiac arrest
• Age > 18 years
• Clinically stable to undergo CT imaging within 6 hours of ED arrival
• No known cardiomyopathy or obstructive coronary artery disease

EXCLUSION CRITERIA

• Obvious cause for OHCA prior to SDCT or on hospital arrival (which included: obvious trauma, drowning, suicide attempt, a massive amount of blood loss, asphyxiation, intoxication, or extreme metabolic abnormalities)
• Any patient with an indication for emergent coronary angiography (eg, STEMI or new left bundle branch block) or any patient who had invasive coronary angiography within 1 hour of hospital arrival
• Known obstructive coronary artery disease or any patient known to have previously been successfully treated for obstructive coronary disease with < 2.5 mm coronary stent
• Known cardiomyopathy with severe systolic dysfunction (LVEF < 35%)
• Any known cardiac defibrillator due to CT artifacts (pacemaker was permissible)
• Known pre-existing Do Not Resuscitate order, any patient with a known terminal disorder with less than 3 months of expected survival, or any patient in hospice care
• Severe renal dysfunction (defined as GFR 1-30 mL/min/1.73m²); however, patients could undergo CT imaging if the treating physicians deemed it to be medically appropriate
• Any patient with known iodinated contrast dye allergy

PRIMARY OUTCOME

Diagnostic yield of SDCT which was defined by the number of patients with an adjudicated diagnosis that was the presumed cause for the OHCA.

SECONDARY OUTCOMES

• Time to adjudicated OHCA diagnosis (time at which a laboratory value, procedure, or scan was completed that led to the OHCA cause or the time of a progress note listing the diagnosis). If no diagnosis was made, then the time of discharge or death was used.
• Percentage of correct diagnoses by SDCT or by any CT scan as part of SOC
• Diagnosis of time-critical diagnosis >6 hours from hospital arrival and safety of SDCT scanning
• SDCT safety, defined as acute kidney injury at 48 hours, contrast dye allergic reactions, complications from CT (eg, line extravasation, extubation), or CT findings leading to inappropriate treatments
• Survival to hospital discharge
• Neurologic outcomes at time of hospital discharge defined by Cerebral Performance Category (CPC)

KEY RESULTS

The CT FIRST study enrolled a total of 247 patients, 143 in the pre-cohort (standard of care alone cohort) and 104 in the post-cohort (Sudden Death CT + standard of care cohort). Subjects were well matched between groups in characteristics including age, race, sex, initial cardiac rhythm, and medical history. Despite the matching there were some group differences, the SDCT cohort had a higher proportion of patients with prior valvular disease (5% in the SDCT group compared to 0.8% in the SOC group), higher rates of bystander CPR (58% in the SDCT group compared to 40% in the SOC group) but lower rates of OHCA in public (17% in the SDCT group compared to 23% in the SOC group).

Primary outcome

The SDCT + SOC group (post-cohort group) identified the presumptive cause of OHCA in 96 out of 104 (92%) cases as compared to 107 out of 143 (75%) of cases in the SOC group (adjusted p value < 0.001).

Secondary outcomes

• The time to diagnosis was decreased by 78% in the SDCT (3.1 hours) vs SOC cohorts (14.1 hours) (adjusted p < 0.0001)
• While both groups identified time-critical diagnoses, there was a 81% decrease in the amount of delayed (>6 hours) diagnoses in the SDCT (12%) vs SOC cohort (62%) (adjusted p < 0.001)
• There was no significant difference between groups in survival to hospital discharge or neurologic recovery
• There were no contrast dye allergic reactions in either group, no difference in AKI in either group and no difference in renal function between patients that received contrast and patients that did not
• There were no complications from SDCT and no inappropriate treatments performed secondary to SDCT findings

LIMITATIONS

• Small study
• Lack of randomization to SDCT group
• A significant amount of patients in the SOC group underwent at least one CT scan, theoretically affecting the analysis of the proposed benefit of the full SDCT
• Not powered to assess for difference in survival to hospital discharge or neurologic function at hospital discharge and so a clinical benefit to the patient is hard to assess

EM TAKE-AWAYS

While it didn’t improve survival to hospital discharge or neurologic recovery vs the SOC, the SDCT protocol significantly improved the time and diagnostic ability to determine the cause of OHCA. Consider SDCT as a way to focus appropriate care and identify time-critical diagnoses for the critically ill post-cardiac arrest patient with an unclear cause of their arrest.

REFERENCES

1. Brooks SC, Clegg GR, Bray J, et al. Optimizing Outcomes after Out-of-Hospital Cardiac Arrest with Innovative Approaches to Public-Access Defibrillation: A Scientific Statement from the International Liaison Committee on Resuscitation. Circulation. 2022;145(13):E776-E801.
2. Peberdy MA, Callaway CW, Neumar RW, et al. Part 9: post-cardiac arrest care: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010;122(18 Suppl 3):S768-S786.
3. Karatasakis A, Sarikaya B, Liu L, et al. Prevalence and Patterns of Resuscitation-Associated Injury Detected by Head-to-Pelvis Computed Tomography After Successful Out-of-Hospital Cardiac Arrest Resuscitation. J Am Heart Assoc. 2022;11(3):e023949-e023949.
4. Chelly J, Mongardon N, Dumas F, et al. Benefit of an early and systematic imaging procedure after cardiac arrest: Insights from the PROCAT (Parisian Region Out of Hospital Cardiac Arrest) registry. Resuscitation. 2012;83(12):1444-1450.