pathway leads to right-axis deviation. Ventricular tachycardia Fascicular tachycardia usually arises from the posterior fascicle of the left bundle branch. They produce QRS complexes of relatively short durations with a right bundle branch block pattern. Tachycardias originating in the anterior left fascicle would lead to right axis deviation. Right ventricular outflow tract tachycardia originates from the outflow tract of the right ventricle or the tricuspid annulus. As it arises from the right ventricle, the impulse spreads inferiorly from beneath the pulmonary valve, and there right axis deviation. Ventricular ectopy Ventricular ectopy is when the heartbeat is an abnormal heartbeat where the QRS complex is significantly wider. When the origin of the ectopic heartbeat is in the anterior fascicule then there is right axis deviation. Pathophysiology The pathophysiology depends on the specific cause of right axis deviation. Most causes can be attributed to one of four main mechanisms. These include right ventricular hypertrophy, reduced muscle mass of left ventricle, altered conduction pathways and change in the position of the heart in the chest. Right ventricular hypertrophy Enlargement of right ventricular myocardial mass can result in right axis deviation. There are 2 main reasons for this mechanism. Firstly, more muscle mass will result in greater amplitude of depolarisation of that side of the heart. Secondly, depolarisation of the heart will be slower through the right ventricle relative to the left, and therefore the effects of the right ventricle on the axis of the heart will be dominant. Left ventricular atrophy Decrease in myocardial mass of the left ventricle will shift the balance of depolarisation towards the right. For example, scarring and atrophy caused by ischaemia of the left ventricle will cause depolarisation of the left side of the heart to be less forceful. Hence, depolarisation of the right ventricle will be greater in amplitude than left, shifting the axis to the right. Conduction abnormalities Changes in the conduction pathways of the heart can result in right axis deviation. For example, an accessory pathway from the left atrium to the left ventricle, as in Wolff-Parkinson-White Syndrome, will result in the left ventricle finishing depolarisation earlier than the right. Hence, the right ventricle will have more of an effect on the axis of the heart. Position of heart in the chest The apex of the heart is normally orientated towards the left. A more vertical orientation of the heart, shifts the axis to the