In an effort to standardize terminology and criteria for clinical electrocardiography, and as a follow-up of its work on definitions of terms related to cardiac rhythm, an Ad Hoc Working Group established by the World Health Organization and the International Society and Federation of Cardiology reviewed criteria for the diagnosis of conduction disturbances and pre-excitation. Recommendations resulting from these discussions are summarized for the diagnosis of complete and incomplete right and left bundle branch block, left anterior and left posterior fascicular block, nonspecific intraventricular block, Wolff-Parkinson-White syndrome and related pre-excitation patterns. Criteria for intraatrial conduction disturbances are also briefly reviewed. The criteria are described in clinical terms. A concise description of the criteria using formal Boolean logic is given in the Appendix. For the incorporation into computer electrocardiographic analysis programs, the limits of some interval measurements may need to be adjusted.

Forty-five patients with Wolff-Parkinson-White syndrome (WPW) were reviewed. The preexcitation using Boineau's classification was: right anterior (six patients), left lateral (nine patients), right posterior (15 patients) and left posterior (15 patients). Normal pathway conduction was observed to occur either spontaneously or after administration of ajmaline, procainamide, or by eye-ball pressure. Disappearance of preexcitation was associated with T wave abnormalities in 39 patients (86.6%). The orientation of the T spatial vector (SAT), after suppression of the WPW aspect, varied according to the site of ventricular preexcitation. In eight patients with left lateral ventricular preexcitation (LLVP), the frontal T wave axis was between +70 degrees and +120 degrees (mean +92 degrees) and the horizontal T wave axis was located in the left anterior quadrant. In the five patients with right anterior ventricular preexcitation (RAVP), the frontal axis was between + 40 degrees and - 10 degrees (mean + 26 degrees) and the horizontal axis was in the left posterior quadrant. The 26 cases with right posterior ventricular preexcitation (RPVP) and left posterior ventricular preexcitation (LPVP) had a frontal axis between - 10 degrees and - 70 degrees (mean -39 degrees) and the horizontal T wave axis in the left anterior quadrant. This study suggests that the T wave anomalies observed after suppression of the WPW aspect are in direct relation to the localization of the preexcitation according to Boineau's classification. The analogy between the abnormalities of the T wave and those which are observed after right ventricular pacing (VP) or after disappearance of left bundle branch block (LBBB) is discussed.

Fasciculoventricular Fibers. INTRODUCTION: Fasciculoventricular tracts are considered a rare form of ventricular preexcitation. Few fasciculoventricular pathways have been reported, and none have been linked to a reentrant tachycardia. METHODS AND RESULTS: Four patients with fasciculoventricular bypass tracts underwent electrophysiologic evaluation. Two patients had a single fasciculoventricular pathway, one that inserted anteroseptally and the other in the left ventricle. Two patients also had an AV bypass tract, with anterograde conduction over the fasciculoventricular pathway during orthodromic AV reentrant tachycardia. After ablation of the AV pathways, the ECG during sinus rhythm and the electrophysiologic study showed ventricular preexcitation due to a fasciculoventricular bypass tract inserting into the right ventricle. Adenosine triphosphate was helpful in the diagnostic process. CONCLUSION: Electrophysiologists should be able to make the differential diagnosis between a fasciculoventricular bypass tract and an anteroseptal accessory pathway to preclude potential harm to the AV conduction system if a fasciculoventricular pathway is targeted for catheter ablation.

The Wolff-Parkinson-White syndrome has been studied in a group of healthy aviation personnel over the past 15 years. The incidence of this electrocardiographic pattern has been determined in 22,500 healthy individuals and found to be 0.25%. The prevalence of documented tachyarrhythmias in this group of individuals was found to be only 1.8% while in a group of referred patients the prevalence was 20%. The limitations of the widely accepted classification into Type A and Type B patterns was borne out by our inability to categorize 45% of subjects with the WPW pattern. Q waves as QS or QR complexes in the inferior limb leads were found in 16.7% of subjects, but in all there was Q wave-T wave vector discordance. The limited value of stress testing in these individuals was reflected by 30% of our patients who demonstrated false positive signs of ischaemic heart disease. A discussion of the incidence, classification, differential diagnosis, mechanism of tachyarrhythmias, associated cardiovascular anomalies, and treatment follows.

Based on an analysis of 4980 ECGs of patients, the authors could distinguish and classify the clinico-electrocardiographic versions of the early ventricular repolarization syndrome (EVRS): permanent, occurring for the first time, suddenly disappearing, intermittent with a gigantic T wave; with a negative T wave, with a short-term T wave inversion, marked by the combination with Wolff-Parkinson-White syndrome, and additional chordae of the left ventricle. The clinico-electrocardiographic classification of the EVRS is of paramount importance for practitioners owing to an assumption that the EVRS is not only a version of the normal ECG but also can be a marker of CHD. The authors view the EVRS as an independent version of the preexcitation syndrome along with Wolff-Parkinson-White and CLK syndromes, with the manifestations of which it may combine.

In a study of 45 cases of ventricular pre-excitation, 19 were classified as type A and 20 as type B according to Rosenbaum's criteria, which depend on the polarity of the major deflections in the right praecordial leads and not, as is commonly thought, on the direction of the delta vector. Six cases that could not be classified as type A or type B were termed intermediate. Vectorcardiograms were recorded from 29, and these showed a wide but continuous range of values for both the delta and the main QRS vectors in all three planes. Any classification based on these features must, therefore, depend on arbitrary quantitative data. Three patients in this series had associated right bundle-branch block. A review of the published reports on the association of pre-excitation and bundle-branch block failed to provide a rational basis for the classification of pre-excitation. It is emphasized that Rosenbaum's classification is empirical and its validity is questioned.