What are the ECG characteristics of right ventricular (RV) strain?

ECG Characteristics of Right Ventricular (RV) Strain

RV strain on ECG manifests through several classic patterns, with T-wave inversion in leads V1-V4, S1Q3T3 pattern, right bundle branch block (complete or incomplete), and right axis deviation being the most diagnostically significant findings. 1

Classic ECG Findings

T-Wave Inversion in Anterior Precordial Leads

• T-wave inversion in leads V1-V4 is one of the most specific markers of RV strain, particularly when new in onset 1
• This pattern reflects RV ischemia and myocardial stretch from acute pressure overload 1
• In pulmonary embolism specifically, anterior T-wave inversions (V1-V4) carry prognostic significance and suggest more severe RV dysfunction 2
• The sensitivity is limited (11.1% overall, 17.1% in large clot load PE), but specificity is excellent at 97.4% 2

S1Q3T3 Pattern

• The classic S1Q3T3 pattern consists of an S wave in lead I, Q wave in lead III, and inverted T wave in lead III 1
• While historically emphasized, this pattern is actually infrequent, occurring in only 3.7% of confirmed PE cases 2
• Despite its low sensitivity, when present it remains a useful marker of RV strain 1, 3

Right Bundle Branch Block (RBBB)

• Complete RBBB (QRS ≥120 ms with rSR' pattern in V1) or incomplete RBBB are important markers of RV strain 1
• Complete RBBB occurred in 9.0% of PE patients and correlates with the extent of vascular obstruction 3, 2
• In massive PE treated with embolectomy, complete RBBB often disappears within 24 hours post-operatively, confirming its acute nature 3
• The presence of RBBB may paradoxically indicate shorter symptom duration and fewer embolic episodes in patients with extensive embolization 3

QR Pattern in Lead V1

• A QR pattern in lead V1 is a specific but less commonly discussed marker of RV strain 1
• This reflects significant RV pressure overload and conduction delay 1

Right Axis Deviation

• Right axis deviation (>120°) suggests RV enlargement and strain 1
• Only 4.2% of PE patients demonstrate this finding, limiting its sensitivity 2
• The increase in frontal QRS axis of ≥20° correlates with extent of vascular obstruction 3

Additional ECG Manifestations

P Pulmonale

• P-wave amplitude ≥2.5 mm in leads II, III, or aVF indicates right atrial enlargement 1
• This is an extremely rare finding in acute RV strain (0.5% in PE) but when present suggests significant RV pressure overload 2

Sinus Tachycardia

• Sinus tachycardia is the most common ECG abnormality in RV strain, occurring in 28% of PE patients 2
• While nonspecific, it reflects the hemodynamic stress of acute RV dysfunction 1

Atrial Arrhythmias

• Atrial dysrhythmias occur in approximately 10% of patients with RV strain from PE 2
• These reflect atrial stretch and increased atrial pressures 2

Clockwise Rotation

• Clockwise rotation (transition zone shifted leftward) occurs in 20% of PE cases 2
• This finding is relatively common but also occurs frequently in controls, limiting its specificity 2

Prognostic Implications

The presence of ≥1 classic RV strain sign (S1Q3T3, RBBB, or T-wave inversion V1-V4) is associated with doubled mortality risk (OR 2.11,95% CI 1.00-4.46) 4. The number of RV strain signs present correlates with adverse outcomes, with each additional sign increasing odds of adverse events by 35% 4.

Important Clinical Caveats

Normal ECG Does Not Exclude RV Strain

• 20-25% of patients with confirmed PE, including those with large clot burden, have completely normal ECGs 2
• No patient with vascular obstruction ≥67% had a normal ECG in one series, but this still means significant PE can exist with minimal ECG changes 3

Transient Nature of Findings

• ECG abnormalities in RV strain are dynamic and changing, requiring serial ECG recordings for optimal detection 3
• Pronounced ECG signs may reflect both massive embolization and short-lasting obstruction 3

Context-Specific Interpretation

• In athletes, T-wave inversion in V1-V3 may be a normal variant (juvenile pattern) in those <16 years old 1
• Complete RBBB in athletes (0.5-2.5% prevalence) may represent physiologic remodeling rather than pathology 1
• In arrhythmogenic cardiomyopathy, T-wave inversion in V1-V4 with LBBB morphology ventricular arrhythmias suggests RV involvement 1

Reliability Concerns

• Interrater reliability for individual ECG signs of RV strain is highly variable (κ 0.40-0.95), which may limit clinical utility 4
• The modest effect size of ECG findings means they should complement, not replace, other risk stratification tools 4