A new method to determine the QRS axis-QRS axis determination.

BACKGROUND The development of a perfect method for determining the mean QRS axis (ÂQRS) is still lacking. HYPOTHESIS We proposed a new simple method, whether this method is accurate is unknown. METHODS The axis perpendicular to the mean QRS axis (P-ÂQRS) divides six limb leads into two groups. All the leads that are in the range of 180° along the ÂQRS are positive, while all the leads in another 180° are negative, one lead is isodiphasic if it is on the P-ÂQRS. If no lead is isodiphasic, then the P-ÂQRS is located in the middle of two adjacent leads, which can help us determine the P-ÂQRS. The six limb leads that fall in the range of -30° to 120° are as follows: aVL (-30°), I (0°), -aVR (30°), II (60°), aVF (90°), and III (120°). We can check an external lead (aVL or III) first. For example, if lead III is isodiphasic and lead aVF is positive, the P-ÂQRS is 120°; if lead III is negative and lead aVF is positive, then the P-ÂQRS is 105°. If more than one lead is negative, all such leads can be checked individually until a positive or isodiphasic lead is found. The ÂQRS can be easily decided once we know the P-ÂQRS. In total, 200 recorded ECGs were investigated. We obtained the ÂQRS from our new method, computer interpretations, and a standard bipolar method. The Pearson correlation coefficient and Bland-Altman analysis were performed. RESULTS The mean and SDs were remarkably similar, the correlation coefficient between the P-ÂQRS method and the bipolar method was 0.976 (P < .001). Mean bias (Bland-Altman limits of agreement) between the two methods was 0.885 (-12.37 to 14.14). CONCLUSION The new method is simple and is able to assess the mean QRS axis accurately.