Essential Revision Notes for MRCP Third Edition - PasTest

Essential Revision Notes for MRCP• Indications for temporary pacing• Asystole• Haemodynamically compromisedbradycardia• Prophylaxis of MI complicated bysecond-degree or complete heart block• Prior to high-risk cardiac interventionsor pacemaker replacement• Prevention of some tachyarrhythmias(eg torsades)• Overdrive termination of variousarrhythmias (eg atrial flutter, VT)• Indications for permanent pacing• Chronic AV block• Sick sinus syndrome with symptoms(including chronotropic incompetence– the inability to appropriately increasethe heart rate with activity)• Post-AV nodal ablation for arrhythmias(elective or inadvertent)• Neurocardiogenic syncope• HCM• Dilated cardiomyopathy (may pacemore than two chambers)• Long QT syndrome• Prevention of atrial fibrillation• Post-cardiac transplantationPacing in heart failureThere are several synonymous terms for pacing inpatients with cardiac failure. These include ‘cardiacresynchronisation therapy’, ‘biventricular pacing’and ‘multisite pacing’. In heart failure pacing isindicated when all of the following are present:• NYHA III–IV heart failure• QRS duration .130 ms or other clear evidenceof dyssynchrony• Left ventricular ejection fraction ,35% withdilated ventricle and patient on optimal medicaltherapy (diuretics, angiotensin-convertingenzyme (ACE) inhibitors and â-blockers)The atria and right ventricle are paced in the usualfashion and in addition to this a pacing electrode isplaced in a tributary of the coronary sinus on thelateral aspect of the left ventricle. The two ventriclesare paced simultaneously or near-simultaneouslywith a short AV delay. The aim is to optimise AVdelay and reduce inter- and intraventricular asynchrony.This therapy is known to reduce mortality,to improve exercise capacity, to improve quality oflife and to reduce hospital admissions.Implantable cardioverter de¢brillators (ICD)ICDs are devices that are able to detect life-threateningtachyarrhythmias and to terminate them byoverdrive pacing or a counter-shock. They are implantedin a similar manner to permanent pacemakers.Current evidence supports their use in bothsecondary prevention of cardiac arrest and also astargeted primary prevention (eg for individuals withleft ventricular impairment and those with familialsyndromes such as arrhythmogenic right ventriculardysplasia, Brugada syndrome, long QT variants).Radiofrequency ablationRadiofrequency ablation is resistive, heat-mediated(658C) protein membrane disruption causing celllysis. Using cardiac catheterisation (with electrodesin right- or left-sided chambers) it interrupts electricalpathways in cardiac structures. Excellent resultsare obtained in the treatment of accessory pathwaysand atrial flutter, and with complete AV nodal ablationor AV node modification. Ventricular tachycardiais technically more difficult to treat (ventricularmyocardium is much thicker than atrial myocardium).Isolation of the pulmonary veins by ablation therapyis now an established technique to treat atrial fibrillation.Current cure rates are around 85%, but morethan one procedure is required in half the cases.Complete heart block and pericardial effusions arerare complications of radiofrequency ablation.Indications to refer to an electrophysiologistIndications for referral to an electrophysiologist aregiven in Table 1.5.30