How to calculate Cardiac Axis скачать в хорошем качестве

How to calculate Cardiac Axis

Kia ora team! My name is Ben — let’s talk cardiac axis. The cardiac axis is the average direction of electrical current travelling through the ventricles. Understanding the Axis Wheel If we look at this wheel: 0° points to the left side of the heart +90° is straight down –90° is straight up The heart’s electrical signal begins at the SA node at the top, then travels downward. You might expect the normal axis to be around +90°, but because the heart sits slightly tilted to the left and the left ventricle is larger than the right, the normal axis is actually between –30° and +90°. More muscle on the left side means more electrical activity pulling the axis leftward. How to Determine Cardiac Axis Let’s look at Lead I and Lead aVF: Lead I = 0° If the QRS is more positive, the axis is toward the left side of the heart (right side of the wheel). If more negative, it’s toward the right side. Lead aVF = +90° If the QRS is more positive, the axis is in the lower half of the diagram. If more negative, the axis is in the upper half. Combine both leads to determine which quadrant of the axis wheel you're in. The "Thumbs Test" You don’t need to draw the wheel — just use your thumbs: Left thumb = Lead I Right thumb = Lead aVF Thumbs up = QRS is mostly positive Thumbs down = QRS is mostly negative Results: Both thumbs up = Normal axis Left thumb up, right thumb down = Possible left axis deviation Left thumb down, right thumb up = Right axis deviation Both thumbs down = Extreme axis deviation Why Use Lead II for Confirmation? Lead II sits at +60°, right in the middle of the normal axis range. If the QRS in Lead II is mostly positive, the axis is likely normal If mostly negative, it may suggest leftward deviation Lead I aVF Lead II Interpretation + — Normal axis – + Still within normal range – – Left axis deviation – + — Right axis deviation – – – Extreme/indeterminate axis Why Do We Care About Axis Deviation? Because it can reveal: Chamber enlargement Conduction abnormalities Acute or chronic heart disease Life-threatening conditions (such as pulmonary embolism) Axis deviation provides a quick clue on the ECG that may indicate underlying pathology — sometimes even before symptoms appear. Common Causes of Axis Deviations Left Axis Deviation (–30° to –90°): Left ventricular hypertrophy (LVH) Left anterior fascicular block (LAFB) Inferior myocardial infarction Left bundle branch block (LBBB) Paced rhythms Right Axis Deviation (+90° to +180°): Right ventricular hypertrophy (RVH) Pulmonary embolism Left posterior fascicular block (LPFB) Lateral myocardial infarction Congenital heart disease (e.g., Tetralogy of Fallot) Extreme Axis Deviation (–90° to –180°): Severe ventricular rhythms Dual fascicular blocks Lead misplacement or artifact (always check this first) Summary Table Axis Deviation Possible Causes Left Axis Deviation LVH, LAFB, Inferior MI, LBBB Right Axis Deviation RVH, PE, LPFB, COPD, congenital heart disease Extreme Axis Deviation Severe conduction disease, abnormal ventricular rhythms