What are the causes of right axis deviation in adults with underlying cardiovascular disease, such as hypertension, hyperlipidemia, or diabetes, and a history of smoking, obesity, or physical inactivity?

Causes of Right Axis Deviation

Right axis deviation (RAD) in adults results from right ventricular hypertrophy, conduction abnormalities, or structural heart disease, with the most common causes being chronic lung disease, pulmonary hypertension, congenital heart defects (particularly atrial septal defect), and right bundle branch block.

Congenital Heart Disease

Atrial septal defect (ASD) is a leading cause of RAD in adults and should be actively excluded when RAD is discovered. The ECG in secundum ASD characteristically shows right-axis deviation, right atrial enlargement, and incomplete right bundle-branch block 1. The RAD occurs due to right ventricular volume overload from chronic left-to-right shunting 1.

• Primum ASD presents differently with superior left-axis deviation rather than RAD, which helps distinguish it from secundum defects 1
• Sinus venosus ASD may show an abnormal P-wave axis in addition to RAD 1
• Any adult presenting with atrial arrhythmia and dilated RV should be investigated for an atrial level shunt 1

Pulmonary Hypertension and Right Ventricular Hypertrophy

RAD with right bundle-branch block configuration suggests pulmonary hypertension and represents an important surgical risk factor 1. This combination indicates significant right ventricular pressure overload and should prompt evaluation for:

• Primary pulmonary arterial hypertension 2
• Chronic obstructive pulmonary disease
• Obstructive sleep apnea 1
• Interstitial lung disease 1

Acute Coronary Syndromes

New-onset RAD during acute myocardial infarction is uncommon but signals severe disease with poor prognosis 3. Transient RAD during acute anterior wall infarction correlates with:

• Significant right coronary artery obstruction (100% incidence versus 25% in controls without RAD) 4
• Collateral circulation between left coronary system and posterior descending artery (73% versus 0% in controls) 4
• More extensive myocardial damage and lower left ventricular ejection fraction 3

The RAD pattern in acute MI manifests as increased R wave voltage in leads II, III, and aVF, with deep S waves in lead aVL 4. This electrocardiographic marker identifies coronary occlusion when ST-segments are difficult to evaluate 3.

Conduction System Abnormalities

• Incomplete or complete right bundle branch block produces RAD 1
• Left posterior hemiblock causes RAD, though isolated left posterior hemiblock is rare 5
• Hereditary conduction patterns can produce pseudo left posterior hemiblock with RAD in the absence of structural disease 6

Obesity and Metabolic Factors

In severely obese patients, RAD may indicate underlying pulmonary hypertension or right ventricular dysfunction 1. The physical examination often underestimates cardiac pathology in obesity, making ECG findings particularly important 1.

• Pedal edema in massive obesity may result from elevated right ventricular filling pressures despite increased cardiac output 1
• Body habitus can camouflage jugular venous distention 1

Cardiovascular Risk Factors in Adults with CHD

Adults with congenital heart disease who develop hypertension, diabetes, or hyperlipidemia face amplified cardiovascular risk 1. These acquired conditions:

• Reduce left ventricular compliance, increasing left-to-right shunting in ASD patients 1
• Accelerate right ventricular failure 1
• Occur in approximately 80% of adults with CHD 1

The prevalence of hypertension in CHD populations may reach 47% in those over 65 years, higher than the general population 1.

Clinical Pitfalls

A left bundle-branch block configuration is unusual in uncomplicated obesity and raises suspicion for occult coronary heart disease, whereas RAD with RBBB suggests pulmonary hypertension 1. This distinction is critical for risk stratification.

Changing axis deviation during acute MI, though rare, indicates dynamic ischemia with multivessel disease and warrants urgent revascularization 5. The combination of anterior MI with transient RAD specifically suggests right coronary involvement with collateral flow 4.

In younger patients, physiological axis divergence increases with steeper electrical heart axis, and misinterpreting this as pathological can lead to unnecessary cardiac workup 7. However, when RAD appears with RV enlargement on imaging, structural disease must be excluded 1.