Cardiologist in Chikkajala, Bangalore • Electronic pacemakers Pacemakers come as temporary or permanent, fixed-rate (although only if they are faulty these days), demand or rate-responsive, atrial, ventricular, biventricular or dual chamber, unipolar or bipolar and as a combination of many of these features. In routine ECG reporting the pacemaker’s exact programming is not usually known, but it is still possible to diagnose the pacemaker type Acute inferolateral infarction with LBBB. Although ST elevation and depression in the limb leads are suggestive, the more discrete elevation in V6 proves the diagnosis (arrows). Within hours, it disappeared and all that was left were primary T wave changes in the inferior leads ). The same patient as in , showing residual primary T wave changes in the inferior leads 90 PRACTICAL CARDIOLOGY Pathological Q waves in all the LV leads in a 90-year-old man with known old anterior infarction Table 3.1 The North American Society of Pacing and Electrophysiology (NASPE) and the British Pacing and Electrophysiology Group (BPEG) generic (NBG) pacemaker codes Position I II III IV V Category Chamber(s) paced Chamber(s) sensed Response to sensing Programmability, rate modulation Anti- tachyarrhythmia function(s) O = none A = atrium V = ventricle D = dual (A + V) O = none A = atrium V = ventricle D = dual (A + V) O = none T = triggered I = inhibited D = dual (D + I) O = none P = simple programmable M = multiprogrammable C = communicating R = rate modulation O = none P = pacing (antitachyarrhythmia) S = shock D = dual (P + S) Manufacturers’ designation only S = single (A or V) S = single (A or V) Note: positions I–III are used exclusively for anti-bradyarrhythmia function. Source: and the all-important capacity to sense the native complexes and pace the appropriate chambers. An international letter code has evolved for describing pacemaker types, shown in Table 3.1. Thus: n VVI = ventricular pacing and sensing, inhibition (in response to sensing)—the pacemaker is inhibited and produces no impulse when it senses a ventricular impulse n AAI = atrial pacing and sensing 3• AN OVERVIEW OF CLINICAL ELECTROCARDIOGRAPHY 91 n VOO = fixed-rate (asynchronous) ventricular pacing, no sensing—this is used for pacemaker testing and is the usual response of a pacemaker when a magnet is placed over it; modern pacemakers are always demand (inhibited) devices n DDD = atrial and ventricular (dual) sensing and pacing n DDDR = same as universal (DDD) pacemaker, with rate-responsiveness—the device will change its pacing rate in response to the patient’s physical activity n VDD = ventricular pacing with dual-chamber sensing (through a single lead). The above codes include the implantable cardioverter-defibrillators. ‘Failed pacemaker’ is not a proper or complete diagnosis. Failure may be intermittent or complete and involve sensing or capture (pacing), or both. A few examples are shown in More examples and details of the pacemaker syndrome and arrhythmias Miscellaneous conditions Chamber hypertrophy Left ventricular hypertrophy Although the ECG is reasonably specific, it is not as sensitive as echocardiography in detecting LVH. The LVH voltage alone may be a normal finding in younger subjects, but in adults over 35 years it usually connotes true LVH, especially if corroboratory findings are present ). Unfortunately, LVH with ST/T changes may be impossible to separate from LVH voltage complicated by ST/T changes of different, especially ischaemic, origin Right ventricular hypertrophy The main criteria for detecting RVH are RAD over +110° and a dominant R wave in V1 (in the absence of its other causes and in the presence of normal-duration QR congenital heart disease conduction defects often come to obscure the hypertrophy patterns.