Expansion
Left ventricular hypertrophy criteria, and the causes of small complexes
Expansion
Left ventricular hypertrophy
- Sokolow-Lyon: S in V1 plus R in V5 or V6 over 35 mm
- Cornell: R in aVL plus S in V3 over 28 mm in men, 20 mm in women
- R in aVL over 11 mm
- Supporting features: left axis deviation, left atrial enlargement, and a strain pattern with downsloping ST depression and asymmetric T inversion in the lateral leads
The criteria are specific but insensitive, and are unreliable in the young, the thin, the obese and in bundle branch block. Echocardiography is the definitive test.
Right ventricular hypertrophy: dominant R in V1, right axis deviation, deep S waves in V5 and V6, and right atrial enlargement.
Low voltage, defined as QRS under 5 mm in all limb leads or under 10 mm in all chest leads
- Something between the heart and the electrodes: pericardial effusion, obesity, emphysema, pleural effusion, subcutaneous emphysema, anasarca
- Less myocardium or infiltrated myocardium: amyloidosis, extensive infarction, myocarditis, cardiomyopathy, constrictive pericarditis
- Systemic: hypothyroidism (myxoedema)
- Technical: wrong calibration, so always check the standardisation mark
Electrical alternans, where the QRS amplitude alternates beat to beat, reflects the heart swinging in a large pericardial effusion. Combined with low voltage and tachycardia it is strongly suggestive of tamponade.