What are the immediate management steps for various ECG (electrocardiogram) findings?

Immediate Management of Various ECG Findings

Obtain a 12-lead ECG within 10 minutes of first medical contact, place the patient on continuous cardiac monitoring with a defibrillator immediately available, and triage based on the presence or absence of ST-segment elevation or equivalent findings. 1, 2

Initial ECG Acquisition and Assessment

• Acquire and interpret a 12-lead ECG within 10 minutes of first medical contact for any patient with suspected acute coronary syndrome 1
• Place the patient immediately on continuous cardiac monitoring with emergency resuscitation equipment and defibrillator nearby 2
• If the initial ECG is nondiagnostic but clinical suspicion remains high, obtain serial ECGs to detect dynamic changes, especially when symptoms persist or clinical condition deteriorates 1
• Consider additional ECG leads (V3R, V4R for right ventricular involvement; V7-V9 for posterior MI) if ongoing ischemia is suspected when standard leads are inconclusive 1

Management Algorithm Based on ECG Findings

ST-Segment Elevation or New LBBB (STEMI)

Activate immediate reperfusion pathway with goal of first medical contact-to-device time ≤90 minutes. 1, 2

Specific ST-Elevation Criteria:

• ≥2.5 mm in men <40 years in leads V2-V3 3
• ≥2.0 mm in men ≥40 years in leads V2-V3 3
• ≥1.5 mm in women in leads V2-V3 3
• ≥1.0 mm in all other leads 3
• Must be present in at least 2 contiguous leads 3

Immediate Actions:

• Activate emergency medical services transport to PCI-capable hospital with advance notification to activate cardiac catheterization team 1, 2
• If fibrinolytic therapy is chosen instead of PCI, initiate in emergency department with door-to-needle time ≤30 minutes 2
• Administer aspirin, antiplatelet agents, anticoagulation, and consider beta-blockers and nitrates unless contraindicated 2
• Do not delay reperfusion for cardiac biomarkers if ST-elevation criteria are met with compatible symptoms 3

Special Considerations:

• For inferior MI, record right precordial leads (V3R, V4R) to identify right ventricular infarction 3
• For suspected posterior MI, look for ST depression in V1-V3 with positive terminal T-waves; confirm with ST elevation ≥0.5 mm in posterior leads V7-V9 3
• New LBBB should not be considered diagnostic of acute MI in isolation; clinical correlation is required 1, 3

ST-Segment Depression or T-Wave Inversion (NSTE-ACS)

Initiate immediate medical therapy and perform risk stratification to determine timing of invasive strategy. 1, 2

Immediate Medical Therapy:

• Aspirin, low molecular weight heparin, clopidogrel, beta-blockers, and nitrates 2
• High-intensity statins targeting LDL-C <70 mg/dL 4
• Titrated IV opioids for chest pain with anti-emetics as needed 4
• Oxygen therapy only if hypoxia, breathlessness, or acute heart failure present (not if saturation ≥90%) 4

Risk Stratification:

• High-risk ECG features include: transient ST-segment changes >0.5 mm, bundle branch block (new or presumed new), or sustained ventricular tachycardia 2
• Patients with ST-segment depression have 30-day death/MI rate of 10.5% vs 5.5% with T-wave inversion alone 5
• Combined ST-elevation and depression carries highest risk (12.4% 30-day death/MI rate) 5

Cardiac Biomarker Protocol:

• Measure high-sensitivity cardiac troponin immediately with results within 60 minutes 1
• Use ESC 0h/1h or 0h/2h algorithm with validated high-sensitivity troponin assays 1
• If first two measurements inconclusive and clinical condition still suggestive of ACS, obtain additional testing at 3 hours 1

Invasive Management:

• High-risk patients should undergo early invasive management with coronary angiography 2
• Perform echocardiography to assess left ventricular function, regional wall motion abnormalities, and mechanical complications 4

Normal or Nonspecific ECG Changes

Patients with normal ECG have extremely low risk (1.3%) for acute MI but require observation with serial biomarkers. 6

Management Strategy:

• Observe in facility with cardiac monitoring (chest pain unit or hospital telemetry ward) 2
• Repeat ECG and cardiac biomarker measurements at predetermined intervals 2
• If chest pain resolved, ECG normal, and cardiac troponin normal (preferably high-sensitivity), perform non-invasive stress test (preferably with imaging) or coronary CT angiography before deciding on invasive approach 1
• Consider coronary CT angiography as alternative to invasive angiography when low-to-intermediate likelihood of CAD and troponin/ECG normal or inconclusive 1

Discharge Criteria:

• Low-risk patients with negative serial ECGs and biomarkers can be managed as outpatients 2
• Provide precautionary pharmacotherapy (aspirin, sublingual nitroglycerin, beta-blockers) for those referred for outpatient stress testing 2

Bradyarrhythmias or Conduction Disorders

Immediately assess hemodynamic stability and prepare for temporary pacing if symptomatic. 2

Specific Findings Requiring Evaluation:

• Profound sinus bradycardia <30 beats/min: Repeat ECG after mild aerobic activity; consider additional testing based on clinical suspicion 1
• Profound first-degree AV block ≥400 ms: Repeat ECG after mild aerobic activity 1
• Advanced second-degree or third-degree AV block: Perform echocardiography, minimum 24-hour ECG monitor, exercise ECG test; consider laboratory screening and cardiac MRI 1
• Review medications that may exacerbate bradycardia or conduction disorders 2

Ventricular Arrhythmias

Perform comprehensive cardiac evaluation to rule out myocardial disease and primary electrical disease. 1

Immediate Actions:

• Echocardiography, cardiac MRI, minimum 24-hour ECG monitor, exercise ECG test 1
• If >2,000 PVCs or non-sustained ventricular tachycardia present, comprehensive cardiac testing including CMR warranted to investigate for myocardial disease 1
• Consider signal-averaged ECG 1

Atrial Tachyarrhythmias

• Perform echocardiography, minimum 24-hour ECG monitor, exercise ECG test 1
• Consider cardiac MRI or electrophysiology study based on clinical suspicion 1

Prolonged QTc

• Repeat resting ECG on separate day 1
• Consider exercise ECG test, laboratory (electrolyte) screening, family screening, and genetic testing when clinical suspicion high 1
• Direct referral to heart rhythm specialist or sports cardiologist for QTc ≥500 ms 1

Brugada Type 1 Pattern

• Immediate referral to cardiologist or heart rhythm specialist 1
• Consider high precordial lead ECG with leads V1 and V2 in 2nd intercostal space or sodium channel blockade if Brugada pattern indeterminate 1
• Consider genetic testing and family screening 1

Ventricular Pre-excitation (WPW)

• Exercise ECG test to assess for abrupt cessation of delta wave (indicates low-risk pathway) 1
• Consider electrophysiology study for risk assessment if low-risk accessory pathway cannot be confirmed by non-invasive testing 1

Continuous Monitoring Requirements

• Continuous rhythm monitoring is mandatory until diagnosis of NSTEMI established or ruled out 1
• All patients with suspected MI should be monitored for arrhythmias for at least 24 hours or until alternative diagnosis made 1, 2
• Patients resuscitated from cardiac arrest should continue monitoring in intensive care unit until ICD implanted (unless clearly transient, reversible, preventable cause) 1
• For uncomplicated acute MI, monitor for minimum 24 hours; for complicated course (ongoing ischemia, heart failure, cardiogenic shock, arrhythmias requiring intervention), continue monitoring for 24 hours after complications resolved 1
• Rhythm monitoring up to 24 hours or to PCI (whichever first) for NSTEMI patients at low risk for cardiac arrhythmias 1
• Rhythm monitoring >24 hours for NSTEMI patients at increased risk for cardiac arrhythmias 1

Critical Pitfalls to Avoid

• Never delay reperfusion therapy to wait for cardiac biomarkers if ECG meets STEMI criteria with compatible symptoms 3
• Do not perform emergent coronary angiography with intent for primary PCI in Type 2 MI (supply-demand mismatch); instead, identify and correct underlying cause 4
• Fibrinolytic therapy is contraindicated in Type 2 MI 4
• Do not assume new LBBB alone is diagnostic of acute MI; clinical correlation mandatory 1, 3
• Serial ECGs are critical as 11% of patients ultimately diagnosed with STEMI had initial nondiagnostic ECG, with 72.4% showing diagnostic changes within 90 minutes 3
• Patients with abnormal ECG but no definite ischemia (LBBB, RBBB, LAH) have relatively low MI incidence (3.6%) but still require evaluation 6

Hemodynamic Instability

• In patients presenting with cardiac arrest or hemodynamic instability of presumed cardiovascular origin, echocardiography should be performed immediately following 12-lead ECG 1
• Consider invasive monitoring of arterial and pulmonary artery pressures for patients with cardiogenic shock, progressive heart failure, or suspected ventricular septal defect or papillary muscle dysfunction 2