<P> Ventricles contain more muscle mass than the atria . Therefore, the QRS complex is considerably larger than the P wave . The QRS complex is often used to determine the axis of the electrocardiogram, although it is also possible to determine a separate P wave axis . </P> <P> The duration, amplitude, and morphology of the QRS complex are useful in diagnosing cardiac arrhythmias, conduction abnormalities, ventricular hypertrophy, myocardial infarction, electrolyte derangements, and other disease states . </P> <P> High frequency analysis of the QRS complex may be useful for detection of coronary artery disease during an exercise stress test . </P> <Table> <Tr> <Th> Parameter </Th> <Th> Normal value </Th> <Th> Value comments </Th> <Th> Clinical significance </Th> </Tr> <Tr> <Td> QRS duration </Td> <Td> 0.06--0.10 s </Td> <Td> Shorter in children and in tachycardia </Td> <Td> Prolonged duration indicates e.g. hyperkalemia . or bundle branch block </Td> </Tr> <Tr> <Td> QRS amplitude </Td> <Td> <Ul> <Li> S amplitude in V1 + R amplitude in V5 <3.5 millivolt (mV) </Li> <Li> R + S in a precordial lead <4.5 mV </Li> <Li> R in V5 or V6 <2.6 mV </Li> </Ul> </Td> <Td> </Td> <Td> Increased amplitude indicates cardiac hypertrophy </Td> </Tr> <Tr> <Td> Ventricular activation time (VAT) </Td> <Td> <Ul> <Li> <0.05 s in V5 or V6 </Li> <Li> <0.03 s in V1 </Li> </Ul> </Td> <Td> </Td> <Td> Measured in increased QRS amplitude </Td> </Tr> <Tr> <Td> Q wave </Td> <Td> <Ul> <Li> Duration up to 0.04 seconds in leads other than III and aVR </Li> <Li> Amplitude less than 1 / 3 QRS amplitude (R + S) </Li> <Li> Amplitude less than 1 / 4 of R wave </Li> </Ul> </Td> <Td> </Td> <Td> Abnormality indicates presence of infarction </Td> </Tr> </Table>

The qrs complex of an electrocardiogram is a result of