What is the significance of R wave progression in electrocardiogram (ECG) interpretation?

R Wave Progression in ECG: Clinical Significance and Interpretation

Definition and Normal Pattern

R wave progression refers to the normal sequential increase in R wave amplitude from leads V1 through V5, representing the transition from predominantly negative QRS complexes over the right ventricle to predominantly positive complexes over the left ventricle. 1

• The R wave normally increases progressively across the precordial leads as the electrode position moves from right to left across the chest 1
• This progression reflects the changing electrical vectors as the recording electrode moves from overlying the right ventricle to the dominant left ventricle 1

Poor R Wave Progression: Four Major Causes

1. Technical/Artifactual (Most Common - Must Exclude First)

Electrode misplacement is the most frequent cause of apparent poor R wave progression and must be systematically excluded before considering pathological diagnoses. 1, 2

• Superior misplacement of V1 and V2 electrodes (in the 2nd or 3rd intercostal space instead of the 4th) reduces R wave amplitude by approximately 0.1 mV per interspace 1
• This misplacement can create rSr' complexes with T wave inversion resembling lead aVR 1
• Transposition of precordial lead wires (V1 with V2, or within V1-V3) causes reversal of R wave progression that simulates anteroseptal infarction, often recognizable by distorted P wave and T wave progression 1, 2
• Inferior-leftward misplacement of left precordial electrodes occurs in more than one-third of routine ECGs 1

2. Prior Anterior Myocardial Infarction (Most Clinically Significant)

• Prior anterior MI is the most important pathological cause, particularly when accompanied by pathological Q waves (Q/R ratio ≥0.25 or ≥40 ms duration in two or more contiguous leads) 1, 2
• All patients with ischemic heart disease and reversed R wave progression had left anterior descending artery stenosis 3
• The sum of R wave amplitude in leads V1-V6 inversely correlates with myocardial infarct size (r = -0.56, p < 0.001) and positively correlates with left ventricular ejection fraction (r = 0.45, p < 0.001) 4

3. Left Ventricular Hypertrophy

• LVH causes poor R wave progression through increased posterior forces that diminish anterior R wave amplitude 1
• Look for increased QRS voltage and associated ST-segment and T wave abnormalities in lateral leads 2
• Voltage criteria for LVH in athletes represent physiologic adaptation and do not require further evaluation when isolated 1

4. Right Ventricular Hypertrophy

• RVH produces poor R wave progression by shifting the QRS vector rightward and anteriorly 1, 5
• Right axis deviation (≥90°) is required for diagnosis in nearly all cases 5
• Up to 13% of athletes fulfill Sokolow-Lyon criteria for RVH, representing normal physiologic adaptation when isolated 1

Reversed R Wave Progression: A Red Flag

Reversed R wave progression (RV2 < RV1, RV3 < RV2, or RV4 < RV3) has a 76% association with cardiac pathology and should never be dismissed as benign. 2, 3

• Among patients with reversed R wave progression, 41% had previous anterior MI and 17% had ischemic heart disease without MI 3
• All patients with ischemic heart disease had left anterior descending artery stenosis 3
• Only 24% of patients with reversed R wave progression were normal 3

Normal Variant

• Poor R wave progression can be a normal variant, particularly in individuals with low cardiothoracic ratio 1
• The positive predictive value for coronary artery disease in the general population is only approximately 7.3% 1
• Normal variant occurs in approximately 8% of individuals without cardiac disease 6
• This represents one tail of a normal distribution of null planes and is not related to age, sex, height, weight, body surface area, or thoracic skeletal abnormalities 6

Systematic Evaluation Algorithm

Step 1: Verify Technical Accuracy

• Repeat the ECG with meticulous attention to lead placement 2
• Ensure V1 and V2 are in the 4th intercostal space at the sternal border 1
• Ensure V5 and V6 are positioned at the horizontal extension of V4 in the 5th intercostal space 2

Step 2: Assess for Anterior MI

• Look for pathological Q waves with Q/R ratio ≥0.25 or ≥40 ms duration in two or more contiguous leads 2
• If present, obtain immediate echocardiography to assess wall motion abnormalities and left ventricular function 2
• Note: Poor R wave progression alone has only 85% sensitivity for anterior MI when using comprehensive criteria 2

Step 3: Evaluate for Ventricular Hypertrophy

• For LVH: Check for increased QRS voltage and ST-T abnormalities in lateral leads; obtain echocardiography to quantify left ventricular mass and assess diastolic function 2
• For RVH: Look for right axis deviation, tall R waves in V1, and patterns of pressure or volume overload; obtain echocardiography to assess right ventricular size, function, and estimated pulmonary artery pressure 2, 5

Step 4: Consider Biventricular Hypertrophy

• In the presence of LVH criteria, look for prominent S waves in V5/V6, right axis deviation, and right atrial abnormality to suggest concurrent right ventricular involvement 5
• Combined R and S wave amplitude greater than 60 mm (6.04 mV) in leads V2-V6 suggests biventricular hypertrophy in patients with congenital heart defects 5

Step 5: Special Populations

• In asymptomatic athletes: Isolated poor R wave progression without other abnormalities may not require extensive workup, but if accompanied by pathological Q waves or other abnormal findings, echocardiography is warranted 2
• In COPD patients: Look for low voltage in limb leads, right or superior axis deviation, rightward P wave axis (>60°), persistent S waves in all precordial leads, and low R wave amplitude in V6; RVH is suggested only if R wave amplitude in V1 is relatively increased 5

Critical Pitfalls to Avoid

• Never dismiss reversed R wave progression as benign - it has 76% association with cardiac pathology 2
• Never rely on poor R wave progression alone to diagnose anterior MI - sensitivity is only 85% even with comprehensive criteria 2
• Lead placement variability as little as 2 cm can result in important diagnostic errors, particularly regarding anteroseptal infarction and ventricular hypertrophy 7
• Pulmonary conditions with low diaphragm position can cause V3 and V4 to be located above ventricular boundaries, recording negative deflections that simulate anterior infarction 1

When to Pursue Further Cardiac Evaluation

Further cardiac evaluation with echocardiography, cardiac MRI, or stress testing is warranted in patients with poor R wave progression and any of the following: 2

• High clinical suspicion of coronary artery disease based on age, cardiac risk factors, or symptoms
• Presence of pathological Q waves
• Reversed R wave progression
• Associated ST-segment depression or T wave abnormalities
• History of cardiac disease