EKG Leads for Right Heart Assessment
For assessing the right side of the heart, use right-sided precordial leads V3R and V4R, with V4R being the single most valuable lead, positioned in the 5th intercostal space at the right midclavicular line. 1
Standard 12-Lead Assessment
In the standard 12-lead EKG, lead V1 provides the best view of right ventricular activity among the routine leads, as it sits closest to the right ventricle anatomically. 2 However, V1 alone has limited sensitivity and specificity for right ventricular pathology. 3
Right-Sided Precordial Leads (The Gold Standard)
The American Heart Association and American College of Cardiology recommend four additional right-sided precordial leads for comprehensive right heart evaluation: 2
- V3R and V4R are the most clinically useful, positioned as mirror images of V3 and V4 on the right anterior chest wall 1
- V4R specifically is positioned in the 5th intercostal space at the right midclavicular line and has the greatest diagnostic value 1
- V1R and V2R (where standard V1 = V1R and standard V2 = V2R) 2
- V5R and V6R complete the right-sided array 2
Critical Clinical Application: Right Ventricular Infarction
Right-sided leads are essential for detecting right ventricular infarction, which complicates approximately 25% of inferior wall myocardial infarctions. 4 The diagnostic approach follows this algorithm:
When to Obtain Right-Sided Leads
Record V3R and V4R immediately in ALL patients with ST elevation in leads II, III, and aVF (inferior MI). 1, 5 This is a joint recommendation from the American Heart Association and American College of Cardiology. 1
Diagnostic Criteria
- ST elevation ≥0.1 mV (1 mm) in V3R or V4R indicates right ventricular involvement 2
- This finding is moderately sensitive and specific for right ventricular injury 2
- Often accompanied by ST elevation in standard lead V1 1, 5
Critical Timing Pitfall
ST elevation in right-sided leads disappears much faster than in inferior leads—you must record V3R and V4R as rapidly as possible after chest pain onset. 1, 6 This is the single most important pitfall to avoid, as delayed recording may miss the diagnosis entirely. 1
Additional Diagnostic Clues in Standard Leads
When right ventricular infarction occurs with inferior MI, look for these patterns in the standard 12-lead:
- ST elevation greater in lead III than lead II suggests right coronary artery occlusion (which supplies the RV in most patients) 5, 7
- ST elevation in V1 may indicate RV involvement 1, 5, 4
- ST depression in leads I and aVL often accompanies RCA occlusion 6
Practical Implementation
Modern ECG machines should be programmed to automatically suggest recording V3R and V4R when ST elevation >0.1 mV occurs in leads II, III, and aVF. 1 If your machine doesn't do this automatically, develop a protocol to manually obtain these leads in all inferior STEMI cases.
Clinical Significance
Identifying right ventricular infarction has major implications for mortality and management:
- Patients with RV infarction have markedly worse prognosis compared to isolated inferior MI 4
- RV failure makes left ventricular filling entirely preload-dependent 4
- Avoid nitroglycerin and use morphine judiciously, as these reduce preload and can cause severe hypotension 4
- Aggressive IV fluid resuscitation is the cornerstone of management 4
- V4R helps distinguish proximal versus distal RCA occlusion, which has prognostic and therapeutic implications 1