What are the causes of poor anterior R wave progression on an electrocardiogram (ECG)?

Poor Anterior R Wave Progression: Causes

Poor R wave progression has four major causes: anterior myocardial infarction, left ventricular hypertrophy, right ventricular hypertrophy, and normal variant, with technical factors like electrode misplacement being the most common artifactual cause. 1, 2

Technical/Artifactual Causes

Electrode misplacement is the most frequent cause of apparent poor R wave progression and must be excluded first. 3, 1

• Superior displacement of V1 and V2 electrodes (placed in the 2nd or 3rd intercostal space instead of the 4th) reduces initial R-wave amplitude by approximately 0.1 mV per interspace, creating artifactual poor R wave progression 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 in the same leads 3
• Inferior-leftward misplacement of left precordial electrodes occurs in more than one-third of routine ECGs and contributes to poor reproducibility 3

Pathological Cardiac Causes

Anterior Myocardial Infarction

Prior anterior MI is the most clinically significant cause, particularly when accompanied by pathological Q waves (Q/R ratio ≥0.25 or ≥40 ms duration in two or more contiguous leads). 3, 1, 4

• Reversed R wave progression (RV2 < RV1, RV3 < RV2, or RV4 < RV3) is highly specific for cardiac pathology, with 76% association with cardiac disease and 41% specifically with anterior MI 4, 5
• All patients with reversed R wave progression and ischemic heart disease had left anterior descending artery stenosis 5
• The positive predictive value of poor R wave progression alone for coronary artery disease in the general population is only approximately 7.3%, making it a poor isolated screening tool 1, 6

Left Ventricular Hypertrophy

LVH causes poor R wave progression through increased posterior forces that diminish anterior R wave amplitude. 2

• Characterized by increased QRS voltage criteria with associated ST-segment and T-wave abnormalities in lateral leads 4
• Voltage criteria for LVH in athletes (up to 85% prevalence) represent physiologic adaptation and do not require further evaluation when isolated 3

Right Ventricular Hypertrophy

RVH produces poor R wave progression by shifting the QRS vector rightward and anteriorly. 2

• Identified by right axis deviation, tall R waves in V1, and patterns consistent with pressure or volume overload 4
• Up to 13% of athletes fulfill Sokolow-Lyon criteria for RVH; when isolated without other abnormalities, this represents normal physiologic adaptation 3

Cardiomyopathies

• Dilated cardiomyopathy (7% of cases with reversed R wave progression) and hypertrophic cardiomyopathy (3% of cases) can present with poor R wave progression 5
• Complete left bundle branch block (QRS ≥120 ms with predominantly negative QRS in V1) alters normal R wave progression and may indicate underlying structural heart disease 3

Normal Variant

Poor R wave progression occurs in 8% of apparently normal individuals without cardiac disease, representing one tail of the normal distribution of cardiac electrical axes. 7

• Not related to age, sex, height, weight, body surface area, thoracic skeletal abnormalities, or ECG frontal axis 7
• Particularly common in individuals with low cardiothoracic ratio 1
• In asymptomatic athletes without family history of sudden cardiac death and no other ECG abnormalities, isolated poor R wave progression does not require extensive workup 4

Pulmonary and Positional Causes

• Low diaphragm position causes V3 and V4 to be located above ventricular boundaries, recording negative deflections that simulate anterior infarction 1
• Pulmonary embolism accounted for 3% of cases with reversed R wave progression in one series 5

Clinical Pitfalls

Never diagnose anterior MI based solely on poor R wave progression—only 2-9% of patients meeting poor R wave progression criteria actually have anterior MI, a proportion no different than expected by chance. 6, 4

• Always verify proper electrode placement before interpreting poor R wave progression as pathological 3, 1
• Look for associated findings: pathological Q waves, ST-segment changes, and clinical context including age, cardiac risk factors, and symptoms 1, 4
• Reversed R wave progression is far more specific (76% association with cardiac pathology) than simple poor R wave progression and warrants thorough cardiac evaluation 4, 5