Tests
1st tests to order
continuous cardiac monitoring
Test
Identifying the cardiac rhythm is a key step in determining which cardiac arrest treatment algorithm to use.
Result
shockable rhythm (ventricular fibrillation/pulseless ventricular tachycardia), or non-shockable rhythm (asystole/pulseless electrical activity)
CBC
Test
Hemorrhage may cause hypovolemia and should be evaluated for.
CBC may not demonstrate acute bleed as dilution has not yet occurred.
Result
low hematocrit in hemorrhage
serum electrolytes
Test
Electrolyte abnormalities may occur as either a cause or consequence of cardiac arrest.[63]
Result
may show electrolyte abnormalities, particularly hyperkalemia or hypokalemia
ABG
Test
Respiratory and metabolic parameters should be optimized as necessary to normalize acid-base status. Abnormal results may be a result of sudden cardiac arrest and not necessarily the cause. May indicate an underlying respiratory etiology of pulseless electrical activity/asystole.
Result
may show respiratory acidosis; metabolic acidosis; respiratory acidosis with renal compensation; metabolic acidosis with respiratory compensation; mixed metabolic and respiratory acidosis; can also reveal hyperkalemia
cardiac biomarkers
Test
Elevations in markers of myocardial infarction (MI) may be a result of sudden cardiac arrest and not necessarily indicate that an MI is the cause.
Result
positive/elevated
point of care ultrasound (POCUS)
Test
POCUS may be used as an adjunct for patient evaluation during cardiac arrest, so long as it does not interfere with standard cardiac arrest treatments.[1][50] International Liaison Committee on Resuscitation guidelines recommend against its routine use, but suggest that if it can be performed by experienced staff without interrupting CPR, it can be used to look for a specific suspected reversible cause.[51] POCUS can be used to identify the presence or absence of cardiac activity, and can also identify features of cardiac tamponade, pneumothorax, hemorrhage, or pulmonary embolism. As these are potentially reversible causes of cardiac arrest, this could alter subsequent management. However, there is evidence that the use of POCUS in cardiac arrest prolongs the length of interruption of CPR during pulse checks.[51][52][53]
Result
presence or absence of cardiac activity; assess for signs of tamponade, pulmonary embolism, pneumothorax, hemorrhage
Tests to consider
ECG
Test
An ECG should be performed immediately after return of spontaneous circulation, then subsequently to assess for evolving changes. Ambulatory ECG monitoring can be useful to capture sporadic events, either by continuous monitoring (Holter recording) over 24-48 hours, or patient-activated ECG recorders (mobile health or smart phone technology) for infrequent events.[7]
Result
may show: prolonged QT interval; ST-segment or T-wave changes; conduction abnormalities; ventricular hypertrophy; QRS prolongation in V1 to V3 and/or epsilon waves in cardiomyopathy; and T-wave inversion in V1 to V3 in arrhythmogenic right ventricular dysplasia (ARVD)
coronary angiography
Test
Consider after achieving return of spontaneous circulation, as coronary artery disease is a predisposing factor for sudden cardiac arrest. In patients with ST-elevation myocardial infarction (STEMI) on ECG, emergency coronary angiography with or without percutaneous coronary intervention, should be performed.[1][7][51] Emergency coronary angiography, is also reasonable for select patients with suspected acute coronary syndrome without ST elevation, including those with hemodynamic/electrical instability or signs of ongoing ischemia.[1] However, several randomized controlled trials in patients without signs of STEMI have shown no benefit in clinical outcomes for early coronary angiography compared to delayed angiography.[7][55][56] International Liaison Committee on Resuscitation consensus recommendations suggest that in patients without signs of STEMI, either early or delayed coronary angiography is reasonable.[51] PCI should only be performed in patients with culprit lesions on coronary angiography. Unnecessary PCI of stable lesions should be avoided in the early phase after out-of-hospital cardiac arrest, given the absence of benefit and increased risk of hemorrhagic complications and stent thrombosis in the setting of sudden cardiac arrest.[57][58]
Result
may show signs of coronary disease; may also reveal acute coronary artery occlusion with thrombus.
echocardiogram
Test
Echocardiography can be used after return of spontaneous circulation to assess cardiac contractility and check for structural abnormalities, valvular disorders, and evidence of tamponade. Left ventricular function should also be assessed 48 hours after return of spontaneous circulation, after the period of post-arrest myocardial stunning.[59] A normal imaging study in patients with ventricular arrhythmias suggests a primary electrical disorder.[7]
Result
assesses cardiac activity and left ventricular function; may show valvular abnormalities, myocardial scarring, cardiomyopathy, pericardial effusion
exercise stress testing
Test
Useful for diagnosing and measuring response to treatment in patients with adrenergic-dependent rhythm disturbances, such as exercise-induced idiopathic monomorphic ventricular tachycardia (VT) or polymorphic VT. The 4-minute recovery QT interval (QTc) after exercise testing can contribute to the diagnosis of long QT syndrome.[7][60] Consider after return of spontaneous circulation.
Result
ECG may show arrhythmia or ectopy. QTc prolongation during the recovery phase may be seen in long QT syndrome.
chest x-ray
Test
May show causes of, or complications from, cardiac arrest. Endotracheal tube placement should be evaluated after return of spontaneous circulation if the patient is intubated.
Result
may show pneumothorax, pulmonary edema, or other disorders of the lungs or thoracic cage
toxicology screen
Test
Illicit substances may predispose to ventricular arrhythmia. Consider after return of spontaneous circulation.
Result
positive in illicit drug use
cardiac magnetic resonance imaging
Test
Preferred test to identify arrhythmogenic right ventricular dysplasia or other primary cardiomyopathies, and should be considered after return of spontaneous circulation if other causes of sudden cardiac arrest are not discovered.
Result
may show arrhythmogenic right ventricular dysplasia or other primary cardiomyopathies
coronary computed tomography angiography
Test
Can be used to rule out coronary artery stenosis in patients who have a low probability of coronary artery disease.[7] Consider after return of spontaneous circulation.
Result
may show signs of coronary artery disease
signal-averaged ECG (SAECG)
Test
Done as necessary after return of spontaneous circulation if other causes of sudden cardiac arrest are not discovered.[7]
Result
late potentials on SAECG may indicate arrhythmogenic right ventricular dysplasia
electrophysiologic study
Test
Evaluation of primary arrhythmia or conduction abnormalities should be considered after return of spontaneous circulation if no other cause of sudden cardiac arrest is found, or if there is potential for ablation of an arrhythmogenic source in patients with prior myocardial infarction.[7][61][62]
Result
an arrhythmogenic focus may be delineated
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