DEPENDENCE OF THE FORM OF THE ELECTRO-CARDIOGRAM UPON THE SITE OF MECHANICAL STIMULATION OF THE HUMAN VENTRICLES

Ventricular arrhythmias. A guide to their localisation

An electrocardiographic atlas of ventricular tachycardias was produced by pacing 27 epicardial sections of the heart and the mitral papillary muscles to simulate focal ventricular arrhythmias and simultaneously recording their 12 lead electrocardiographic appearances. One hundred and twenty nine patients undergoing cardiac surgery were studied. In five patients all 27 epicardial sites were paced at operation and in 124 individual sections were paced postoperatively with temporary epicardial wires and the electrocardiograms analysed in terms of frontal and horizontal plan QRS axis, maximum limb lead QRS amplitude, and QRS duration. Each ventricular region paced produced a distinctive 12 lead electrocardiographic pattern. Simulated right ventricular arrhythmias had either inferior frontal plane QRS axes (from the anterobasal region) or superior frontal plane QRS axes (from the apical and posterior right ventricular sections). Horizontal plane QRS axes were directed leftwards, with some posterior shift in the anteroapical regions. Simulated arrhythmias from the base of the left ventricle (anteriorly and laterally) had inferior frontal plane QRS and anterorightward horizontal plane QRS axes. Left ventricular arrhythmias with a superior frontal plane QRS axis were readily distinguished by their horizontal plane QRS axes: posterorightwards from the anterior and anterorightwards from the posterior left ventricular sections. Standard errors of the paced QRS axes for the various epicardial sections paced postoperatively ranged from 3.0 degrees to 6.0 degrees using the frontal plane axis. The electrocardiogram was most accurate in localising ventricular arrhythmias from the anterior left ventricle and least accurate for those arising from the inferior right ventricle. The appearance of the paced electrocardiograms was slightly modified by underlying disease such as myocardial infarction and left ventricular hypertrophy. This atlas may be useful in comparing the localisation of ventricular tachycardia with the site of underlying cardiac disease and may facilitate mapping in patients with refractory ventricular tachycardia requiring ablation (either surgical or by high energy impulses).

The history of bundle branch block

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The noninvasive localization of ventricular pacing sites by radionuclide phase imaging

This study was designed to investigate the potential role of radionuclide angiographic phase imaging in defining ventricular pacing sites. Twenty patients were paced from multiple right ventricular and left ventricular sites. Ten patients had both normal wall motion and normal electrocardiograms (ECGs), while 10 patients had segmental wall motion abnormalities and/or bundle branch block. Both continuous pacing and premature ventricular stimuli were performed. Multiple (two to three) views of each pacing site were obtained by radionuclide angiography and the ventricular site was determined by subsequent phase imaging. Simultaneous 12-lead ECGs were also obtained. The phase-imaging technique accurately localized all 35 right ventricular and 21 of 25 (84%) left ventricular sites to a specific segment. Statistically, this localization ability was independent of baseline wall motion or conduction system disease. In addition, sites as close as 1.5 cm were identified. The 12-lead ECG distinguished left ventricular from right ventricular pacing sites in all patients. Segmental localization by ECG in the right ventricle was accurate in 24 of 35 (69%) and in the left ventricle in 17 of 25 (68%). Thus, radionuclide angiographic phase imaging provides excellent descriptive information regarding the focus of ventricular pacing ectopy and can define both sites of continuous pacing and intermittent premature ventricular stimulation. These findings provide a basis for further assessment of the role of phase imaging in the evaluation of patients with spontaneous ventricular ectopy.

Ventricular activation during ventricular endocardial pacing: I. Electrocardiographic patterns related to the site of pacing

The QRS configuration produced by pacing at multiple left ventricular endocardial sites was evaluated in eight patients with (group 1) and six patients without (group 2) left ventricular wait motion abnormalities. Pacing was performed at a total of 122 sites, 4 to 13 sites in each patient. The QRS configuration resulting from apical pacing locations was compared with that at basal, septal to lateral and inferior to superior locations. Significant differences in QRS configuration during pacing from apical and basal locations were observed in electrocardiographic leads I, V1, V2 and V6 (probability [p] less than 0.01). Specifically, a QS pattern in leads I, V2 and V6 was more characteristic of an apical pacing location (p less than 0.001), and a monophasic R wave in leads V1 and V2 was more characteristic of a basal pacing location (p less than 0.01). Significant differences in leads V1 and V2 were observed when septal and lateral pacing sites were compared (p less than 0.001). A monophasic R wave in leads V1 and V2 was more characteristic of a lateral pacing location (p less than 0.01); a QS complex in lead V2 was more characteristic of a septal pacing location (p less than 0.001). Pacing at superior sites usually produced an inferior axis and vice versa (p less than 0.001). The electrocardiographic patterns produced by pacing at similar sites in patients in group 1 were less consistent than those in patients in group 2. The QRS complex during ventricular pacing was wider in patients in group 1 (159 +/- 30 ms) than in patients in group 2 (132 +/- 18 ms) (p less than 0.001). It is concluded that the QRS configuration recorded with 12 lead electrocardiography during endocardial pacing can help locate the region of the pacing site in patients with and without organic heart disease, although precise localization is not possible.

The Localization of Ventricular Extrasystoles

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