What ECG changes can be expected in a patient with a thoracic aortic aneurysm?

ECG Changes in Thoracic Aortic Aneurysm

Thoracic aortic aneurysms (TAA) themselves do not produce specific or diagnostic ECG changes—the ECG is typically normal or shows nonspecific findings unrelated to the aneurysm. 1

Understanding the ECG-Aneurysm Relationship

The critical concept here is that uncomplicated TAA is an anatomic structural problem that does not directly affect cardiac electrical activity. The ECG serves a different purpose in this context:

What You May See on ECG

• Normal sinus rhythm is the most common finding in patients with uncomplicated TAA 2
• Left ventricular hypertrophy (LVH) patterns may be present due to associated hypertension or aortic valve disease, not the aneurysm itself 3
• Left axis deviation can reflect chronic hypertension or LVH from coexisting conditions 2
• Nonspecific ST-T wave changes may indicate underlying coronary disease or hypertension, which are risk factors for TAA but not caused by the aneurysm 3

When ECG Changes Signal Complications

ECG abnormalities become clinically significant when TAA complications occur, particularly acute aortic dissection:

• ST elevation in lead aVR predicts higher hospital mortality (OR 5.30) when dissection occurs 1
• ST depression or T-wave changes correlate strongly with shock (65.2% vs 28.8%) and cardiac tamponade (51.2% vs 15.0%) in acute dissection 1, 4
• ST elevation in other leads (8.2% of dissection cases) indicates direct coronary artery involvement from dissection extension 4
• QRS duration >120 milliseconds predicts worse long-term mortality (HR 2.45) in dissection patients 1
• Any abnormal ECG finding is associated with higher surgical mortality (20.6% vs 11.9%) in acute aortic syndromes 1

Clinical Algorithm for ECG Interpretation

When evaluating a patient with known or suspected TAA:

1. Recognize that the ECG does not diagnose or monitor TAA 1, 2
2. Use ECG to rule out acute coronary syndrome and assess for cardiac complications that may coexist 2
3. If acute ECG changes appear (ST elevation, depression, or T-wave inversion), immediately consider aortic dissection before initiating thrombolysis or catheterization 4
4. Order ECG-gated CT angiography as the gold standard for definitive TAA diagnosis and monitoring, not serial ECGs 1

Critical Pitfalls to Avoid

Never delay definitive imaging (CTA or MRA) based on a normal ECG—the sensitivity of ECG for detecting thoracic aortic disease is extremely limited 1. The American College of Radiology explicitly advises against this approach 1.

Do not mistake acute ECG changes for primary cardiac ischemia in patients with chest pain and risk factors for aortic disease. Acute ECG changes occur in 49.7% of type A dissections, with ST depression and T-wave changes being far more common (34.0% and 21.4% respectively) than ST elevation (8.2%) 4.

Proper Diagnostic Approach

• Transthoracic echocardiography (TTE) serves as first-line screening for the aortic root and proximal ascending aorta, while simultaneously assessing for LVH and valvular disease that may explain ECG findings 5, 2
• ECG-gated CT angiography provides comprehensive evaluation of the entire thoracic aorta with superior spatial resolution and is the definitive imaging modality 5, 1
• ECG gating during CT acquisition eliminates motion artifact at the aortic root and ensures reproducible measurements at the same cardiac phase, with 5-10% diameter variation between systole and diastole 5