What does an ST depression of -1.05 mm on an electrocardiogram (ECG) indicate?

ST Depression of -1.05 mm on Lexiscan Stress Test: Clinical Significance

An ST depression of 1.05 mm on a Lexiscan (regadenoson) pharmacologic stress test indicates myocardial ischemia and requires immediate risk stratification with cardiac biomarkers and clinical assessment for acute coronary syndrome. 1

Diagnostic Interpretation

Horizontal or downsloping ST depression ≥0.5 mm (0.5 mV) at the J-point in two or more contiguous leads is diagnostic of myocardial ischemia. 1 Your finding of 1.05 mm exceeds this threshold and represents clinically significant ischemia. 1

Severity Assessment

• ST depression of 1.0 mm carries an 11% risk of death or MI at 1 year 1
• The magnitude correlates directly with the extent and severity of coronary artery disease 1, 2
• ST depression >1.0 mm indicates higher likelihood of multivessel coronary disease 1, 2
• Each additional millimeter of ST depression increases mortality risk approximately six-fold when exceeding 2 mm 1

Immediate Clinical Actions Required

Acute Assessment

• Obtain cardiac troponin immediately and repeat at 1-3 hours if using high-sensitivity assays 3
• Perform 12-lead ECG within 10 minutes to assess for dynamic changes 3
• Assess for active chest pain, dyspnea, or other ischemic symptoms 4
• Check vital signs for hemodynamic instability 3

Risk Stratification Based on Context

If symptomatic (chest pain, dyspnea) with this ST depression: This represents high-risk acute coronary syndrome requiring immediate hospital admission, dual antiplatelet therapy, and consideration for urgent coronary angiography within 12-24 hours 3

If asymptomatic during the test: This still indicates significant coronary artery disease requiring:

• Cardiology consultation for invasive versus non-invasive anatomic assessment 1
• Initiation of guideline-directed medical therapy including antiplatelet agents, statins, and anti-anginal therapy 1
• Risk factor modification per primary prevention guidelines 1

Anatomic Correlation

The location of ST depression provides critical information about which coronary territories are affected:

• Lateral leads (I, aVL, V5, V6): ST depression in ≥2 lateral leads predicts three-vessel or left main disease in 60% of cases and carries 3.5-fold increased mortality risk 5
• Anterior leads (V1-V3): May indicate posterior wall ischemia, especially if terminal T-waves are positive 4, 3
• Multiple leads: The number of leads showing ST depression correlates with extent of coronary disease 1, 2

Important Caveats and Pitfalls

Exclude Non-Ischemic Causes

Before attributing ST depression solely to ischemia, rule out:

• Left ventricular hypertrophy with strain pattern 6
• Left bundle branch block 1, 6
• Digitalis effect 6
• Baseline ST depression on resting ECG (measure only additional depression during stress) 1, 7
• Electrolyte abnormalities 4

Pattern Matters

• Upsloping ST depression is generally equivocal and less specific for ischemia unless ≥2.0 mm at 80 ms after the J-point in highly symptomatic patients 1, 8
• Horizontal or downsloping patterns are more specific for true ischemia 1

Prognostic Implications

The sum of ST depression across all leads is a powerful independent predictor of 30-day mortality (p<0.0001), even after adjusting for clinical variables and cardiac biomarkers 2. Your finding of 1.05 mm places the patient at intermediate-to-high risk requiring aggressive management.

Correlation with Disease Severity

• ST depression correlates significantly with three-vessel disease (p<0.0001) 2
• Correlates with left main coronary artery disease (p<0.0001) 2
• Predicts peak creatine kinase levels during acute events (p<0.0001) 2

Management Algorithm

1. Immediate: Check troponin, perform 12-lead ECG, assess symptoms 3
2. If troponin elevated OR symptomatic: Admit for NSTEMI management with early invasive strategy 3
3. If troponin normal AND asymptomatic: Outpatient cardiology referral within 1-2 weeks for consideration of coronary angiography or coronary CT angiography 1
4. All patients: Initiate aspirin, statin, beta-blocker (if no contraindications), and optimize cardiovascular risk factors 1, 3