What is a cardiac MRI with T2 testing?

Cardiac MRI with T2 Testing: A Diagnostic Tool for Myocardial Inflammation

A cardiac MRI with T2 testing is a non-invasive imaging technique that evaluates myocardial inflammation by detecting tissue edema, which is an essential component of acute inflammatory processes in the heart. 1

What is Cardiac MRI with T2 Testing?

• Cardiac MRI (CMR) is a specialized imaging technique that provides detailed structural and functional assessment of the heart without radiation exposure 1
• T2 testing specifically refers to techniques that measure or visualize T2 relaxation times in cardiac tissue, which are sensitive to increased water content (edema) in the myocardium 1, 2
• T2 testing can be performed through two main approaches:
  • T2-weighted imaging: Qualitative assessment using specialized sequences (typically short-tau inversion recovery or STIR) that highlight areas of increased water content 1, 3
  • T2 mapping: Quantitative measurement of actual T2 relaxation times throughout the myocardium, displayed as color maps 2, 4

Clinical Applications

• T2 testing is primarily used to detect myocardial edema, which is a hallmark of:

  • Acute myocarditis (viral, autoimmune, or other causes) 1, 5
  • Acute myocardial inflammation in various cardiomyopathies 4, 6
  • Active cardiac sarcoidosis 6

• T2 abnormalities can help differentiate between acute and chronic myocardial injury 1

  • T2 is specifically elevated in acute inflammatory processes
  • T2 elevations diminish as acute inflammation subsides

Diagnostic Criteria (Lake Louise Criteria)

• According to the 2018 updated Lake Louise Criteria from the American College of Cardiology, CMR provides strong evidence for acute myocardial inflammation when both of the following are present: 1

  1. A T2-based marker for myocardial edema (either T2-weighted imaging or T2 mapping)
  2. A T1-based marker for associated myocardial injury (LGE, T1 mapping, or ECV)

• T2-based markers specifically detect edema, which is an essential component of acute inflammation 1, 7

  • T2-weighted imaging: Visual assessment of signal hyperintensity or quantitative T2 signal intensity ratio ≥2.0 compared to skeletal muscle 1
  • T2 mapping: Direct measurement of T2 relaxation times, with elevated values indicating edema 1, 4

Advantages of T2 Mapping over Traditional T2-Weighted Imaging

• Higher signal-to-noise ratio 1
• Shorter breath-holds with fewer breathing motion artifacts 1
• Direct quantification of T2 values 2, 4
• Improved intraobserver and interobserver variability 1
• Better diagnostic confidence 1, 4
• Superior for detecting chronic myocarditis (73% diagnostic accuracy in patients with symptoms >14 days) 1

Pathophysiological Basis

• During inflammation, several processes occur that affect T2 signal: 7

  • Increased vascular permeability due to inflammatory mediators (bradykinin, serotonin, prostaglandins)
  • Endothelial cell contraction creating gaps that allow fluid leakage
  • Vasodilation with hyperemia
  • Net expansion of the extracellular space

• These changes result in increased myocardial water content (edema), which prolongs T2 relaxation time 7, 2

Clinical Value and Interpretation

• T2 mapping is particularly useful for ruling out active inflammation (sensitivity of 89%) 1
• T2 abnormalities may be reversible with appropriate treatment, as demonstrated in cardiac sarcoidosis 6
• T2 elevations are most pronounced during early, acute inflammation and diminish as inflammation subsides 1
• T2 mapping may be more specific for acute inflammation compared to T1 mapping, which can also detect water in chronic settings such as scarring or fibrosis 1

Common Pitfalls and Limitations

• T2-weighted imaging can be limited by: 1

  • Low signal-to-noise ratio
  • Susceptibility to arrhythmia and motion artifacts
  • Inconsistent image quality
  • False negatives if skeletal muscle is also involved in systemic inflammatory disease

• T2 mapping addresses many of these limitations but requires specialized sequences and expertise 1, 4

• Interpretation should consider that T2 abnormalities may reflect not only edema but also other tissue alterations 4

• For optimal diagnostic accuracy, T2 testing should be combined with other CMR techniques (T1 mapping, LGE) 1