Does V4R Alone Indicate RV Infarction?
Yes, ST-segment elevation in V4R alone (≥1 mm or 0.1 mV) is sufficient to diagnose right ventricular infarction extension in the setting of inferior MI, even without changes in V3R.
Primary Diagnostic Criterion
Lead V4R is the single most predictive electrocardiographic finding for RV ischemia/infarction, with ST-segment elevation ≥1 mm (0.1 mV) being diagnostic 1, 2, 3.
The 2017 ESC Guidelines explicitly recommend recording V3R and V4R to identify concomitant RV infarction in inferior MI, but V4R carries the highest diagnostic value 1.
Research demonstrates that V4R achieves 100% sensitivity for posterior RV infarction when ST elevation is present, with the highest specificity (68.2%) among all right precordial leads 4.
Why V4R Is Superior to V3R
V4R has consistently higher sensitivity (78.6-100%) and specificity than V3R for detecting RV involvement 4.
ST elevation may be present in V4R while V3R remains normal, and this still represents true RV extension 4.
The diagnostic efficiency of V4R alone reaches 80.6%, making it the most reliable single lead for RV infarction diagnosis 4.
Enhanced Specificity Criterion
If ST elevation in V4R exceeds that in leads V1-V3, specificity reaches 100% with positive predictive value of 100% and diagnostic efficiency of 91.7% 4.
This comparative criterion is more specific than V4R elevation alone but less sensitive (78.6% vs 100%) 4.
Clinical Implications and Management
RV infarction increases mortality from 6% to 25-30% in inferior MI patients, making recognition critical 1, 5.
The classic triad of hypotension, clear lung fields, and elevated jugular venous pressure has <25% sensitivity, so ECG diagnosis is essential 1.
V4R changes may be transient, resolving within 10 hours in half of patients, so recording should occur as rapidly as possible after symptom onset 1, 2, 3.
Recommended Approach
Record V3R and V4R in all patients with inferior ST elevation (leads II, III, aVF) 1, 2, 3.
Diagnose RV extension if V4R shows ≥1 mm ST elevation, regardless of V3R findings 1, 4.
Initiate RV-specific management: volume loading with IV normal saline, avoid nitrates/diuretics, maintain AV synchrony, and pursue urgent reperfusion 1.
Common Pitfall
Do not wait for V3R changes or require both leads to be abnormal before diagnosing RV involvement—V4R alone is sufficient and more sensitive 4.
Hospital personnel must be trained to properly record V4R at the fifth intercostal space in the right mid-clavicular line, as technical errors can miss the diagnosis 1.