The ECG of a patient with an aificial pacemaker in the right ventricle shows-

Bundle branch block Damage to the right or left bundle branch of the conducting system can occur as a result of many pathologies, including ischaemic hea disease, hypeensive hea disease and cardiomyopathy. However, right bundle branch block (RBBB) can occur as a normal variant in healthy individuals . In left bundle branch block (LBBB) and RBBB, depolarisation proceeds through a slow myocardial route in the affected ventricle rather than through the rapidly conducting Purkinje tissues that constitute the bundle branches. This causes delayed conduction into the LV or RV, broadens the QRS complex (>=0.12 sec) and produces characteristic alterations in QRS morphology loss of consciousness that occurs without warning and results in collapse. A brief anoxic seizure (due to cerebral ischaemia) may occur if there is prolonged asystole. There is pallor and a death-like appearance during the attack, but when the hea stas beating again there is a characteristic flush. In distinction to epilepsy, recovery is rapid. Sinoatrial disease and neurocardiogenic syncope may cause similar symptoms. Management This depends on the clinical circumstances. Acute inferior MI is often complicated by transient AV block because the right coronary aery (RCA) supplies the AV node. There is usually a reliable escape rhythm and, if the patient remains well, no treatment is required. Symptomatic second- or third-degree AV block may respond to atropine (0.6 mg IV, repeated as necessary) or, if this fails, a temporary pacemaker. In most cases, the AV block will resolve within 7-10 days. Second- or third-degree AV hea block complicating acute anterior MI indicates extensive ventricular damage involving both bundle branches and carries a poor prognosis. Asystole may ensue and a temporary pacemaker should be inseed promptly. If the patient presents with asystole, intravenous atropine (3 mg) or intravenous isoprenaline (2 mg in 500 mL 5% dextrose, infused at 10-60 mL/hr) may help to maintain the circulation until a temporary pacing electrode can be inseed. Temporary pacing can provide effective rhythm suppo in the sho term. Ref Harrison 20th edition pg 1536