What is the cause of T wave inversions in a strain pattern on an electrocardiogram (ECG)?

T Wave Inversions in Strain Pattern: Causes and Significance

T wave inversions in strain pattern are primarily caused by secondary repolarization abnormalities resulting from increased left ventricular mass and myocardial fibrosis, which alter the normal transmural repolarization sequence from endocardium to epicardium 1.

Pathophysiology of T Wave Inversions in Strain Pattern

The classic strain pattern consists of three key components:

• J-point depression
• Upwardly convex down-sloping ST segment depression
• Asymmetrical T wave inversion opposite to the QRS axis (typically in leads V5 and/or V6)

This pattern develops through several mechanisms:

1. Altered Repolarization Sequence:

   • In normal hearts, repolarization progresses from epicardium to endocardium
   • In LVH with strain, this sequence is reversed, causing T wave inversion 2
   • This abnormal transmural repolarization contributes to diastolic dysfunction

2. Myocardial Fibrosis:

   • Strain pattern is strongly associated with myocardial fibrosis
   • 100% positive predictive value for midwall late gadolinium enhancement on cardiac MRI 3
   • Both replacement fibrosis and diffuse fibrosis are increased in patients with ECG strain

3. Myocardial Injury:

   • Patients with strain pattern show elevated cardiac troponin levels, indicating ongoing myocardial damage 3
   • This subclinical injury contributes to the ECG changes and adverse outcomes

Clinical Significance

The presence of strain pattern has important prognostic implications:

• Marker of Advanced Disease:

  • Associated with greater left ventricular mass in patients both with and without coronary heart disease 4
  • Indicates more severe structural heart disease

• Predictor of Adverse Outcomes:

  • Independent predictor of cardiovascular mortality (HR 1.53) 5
  • Associated with increased risk of myocardial infarction (HR 1.55) 5
  • Predicts composite cardiovascular endpoints even with aggressive blood pressure control 5

• Diastolic Dysfunction:

  • 5.6-fold increased odds of diastolic dysfunction in patients with T wave inversion and LVH 2
  • Associated with higher E/e' ratios and left atrial volumes

Conditions Associated with Strain Pattern

Strain pattern is most commonly seen in:

1. Hypertensive Heart Disease:

   • Prevalence ranges from 2.1% to 36% in hypertensive patients 6
   • Higher prevalence in the era before effective antihypertensive therapy

2. Aortic Stenosis:

   • Specific marker of midwall myocardial fibrosis 3
   • Independent predictor of aortic valve replacement or cardiovascular death

3. Cardiomyopathies:

   • Dilated cardiomyopathy
   • Hypertrophic cardiomyopathy
   • Other conditions with significant LVH

Clinical Approach to Strain Pattern

When encountering strain pattern on ECG:

1. Recognize the significance:

   • The term "strain" is discouraged; "secondary ST-T abnormalities" is preferred 1
   • These changes indicate advanced disease with higher cardiovascular risk

2. Evaluate for underlying causes:

   • Assess for hypertension, aortic stenosis, and other causes of LVH
   • Consider echocardiography to confirm LVH and evaluate for structural heart disease

3. Risk stratification:

   • Patients with strain pattern require more aggressive management
   • The pattern identifies patients at higher risk for cardiovascular morbidity and mortality 6

Pitfalls and Caveats

• Not just a benign ECG finding: Unlike isolated voltage criteria for LVH, strain pattern indicates more advanced disease and worse prognosis

• Independent of voltage criteria: Strain pattern provides prognostic information beyond QRS voltage alone 1

• Persists despite treatment: Remains a significant risk marker even with aggressive blood pressure control 5

• Not limited to hemodynamic burden: While originally attributed to increased hemodynamic work, strain pattern also occurs in conditions like cardiomyopathies without hemodynamic overload 1