The article by Viskin et al[1] adds some confusion to the definition of "the typical" electrocardiographic pattern associated with the syndrome of sudden death and right bundle branch delay described by Nava and Martini in 1988-1989,[2, 3] by Aihara in 1990, and by Brugada in 1992. As clearly documented,[3] three (and not one as discussed by Viskin et al) of six patients with aborted sudden death showed different degrees of right bundle branch block, left axis deviation, prolonged PR interval and ST segment elevation. Two more patients had mild isolated ST elevation with T inversion. The same polymorphic patterns were lately documented either with standard electrocardiography or after class 1C drugs (in subjects with normal ECG or minor ST-T abnormalities), either in Brugada's or other series.[4] Thus a typical sign of the syndrome is a fascinating but not confirmed statement.

Viskin probably wants to emphasise the first and the most popular electrocardiogram of the syndrome, which is the one published in 1988[1] and 1989 (patient 3 of figure 1 in reference 2), and reprocessed by Brugada on his web site.

This electrocardiogram shows an R' wave in V1 (incorrectly called J wave), very similar to an incomplete right bundle branch block, followed by a coved ST elevation. It must be remembered that the typical J wave is those recorded in leads II, III, aVF, V5-V6 in vagotonia, and other pathological conditions.[5] Thus R' in V1 is an atypical J wave, or something else.

Different from a right bundle branch delay, the atypical J wave seen in V1 shows neither a late and slurred S wave in V6, or the typical vectorcardiographic terminal loop.[1] Late potentials often characterise this pattern, but are absent in pure incomplete right bundle branch block. Thus the trace proposed by Viskin et al in figure 2 as the typical sign of the syndrome is, in reality, a typical incomplete right bundle branch block, while the trace presented in figure 3A closely resembles a true atypical J wave with coved ST elevation, and not a questionable sign.

This does not means that Viskin et al's patients do not have the syndrome, because this is not characterised by a single electrocardiographic pattern, but by polymorphic right bundle branch delays with ST elevation.[2] The latter can be the only basal abnormality, with the atypical J wave appearing spontaneously, or being induced after class 1C drugs.

The significance of all the electrocardiographic patterns of the syndrome, particularly of the atypical J wave and coved ST elevation, is strongly debated. Brugada favours a functional repolarisation abnormality, while we think, according to electrical and anatomic demonstration, that it represents an organic depolarisation abnormality.[4] This can be easily demonstrated by recording late potentials. As mentioned before, in patients with the discussed "typical" electrocardiogram late potentials are almost always present, clearly demonstrating that the atypical J wave and coved ST elevation is due to a delayed QRS activity, probably of the outflow tract of the right ventricle.[4]

Please contact Dr Martini for a copy of the figure described below (unfortunately we cannot support illustrations in Rapid Responses)
The atypical J wave with coved ST elevation in V1, is identical in these two subjects with the syndrome. The trace on the left is the patient of Brugada described in Heart[6] after ajmaline; this pattern was ascribed to a functional repolarisation abnormality. The trace on the right is that of an apparently normal patient, belonging to a family affected by a minor form of right ventricular cardiomyopathy. This patient has a very positive late potentials study, indicating that the atypical J wave and ST elevation, both spontaneous and drug inducible, represents a late depolarisation abnormality of the cardiac activity, probably at the right ventricular outflow tract level. A repolarisation abnormality can never induce late potentials.

Bortolo Martini MD*
Andrea Nava MD+
Sergio Cannas MD*
*Department of Cardiology, Ospedale Civile di Thiene
+Department of Cardiology, University of Padua

Correspondence to:
Bortolo Martini MD
Via Gioberti 9
36016 Thiene (VI), Italy
Fax +39 445 368537

References

(1) Viskin S, Fish R, Eldar M, et al. Prevalence of the Brugada sign in idiopathic ventricular fibrillation and healthy controls. Heart 2000;84:31-6.

(2) Nava A, Canciani B, Schiavinato ML, Martini B, Buja GF, La repolarisation precoce dans le precordiales droites: trouble de la conduction intraventriculaire droite? Correlations de l'electrocardiographie- vectorcardiographie avec l'electro- physiologie. Mises a Jour Cardiologiques 1988;17:157-9.

(3) Martini B, Nava A, Thiene G, et al. Ventricular fibrillation without apparent heart disease: description of six cases. Am Heart J 1989;11:1203-9.

(4) Martini B, Corrado D, Nava A, Thiene G. Syndrome of right bundle branch block, ST segment elevation and sudden death: evidence of an organic substrate. In: Nava A, Thiene G, eds. Arrhythmogenic right ventricular cardiomyopathy. Elsevier 1997:438-53.

(5) Yan GX, Antzelevitch C. Cellular basis for the electrocardiographic J wave. Circulation 1996;93:372-9.

(6) Brugada P. Brugada syndrome: an electrocardiographic diagnosis not to be missed. Heart 2000;84:1-3.

We thank Lawrance et al for their letter that raises several important points about the implementation of the national audit of myocardial infarction.[1] Until the numerator and denominator can be confidently stated there is little point in producing case fatality data either nationally or locally. The data that they quote in their letter strongly support this view. There is an urgent need to address this problem.

The definition of myocardial infarction which can be used in hospital, and which we propose to use for the national audit relies primarily on the demonstration of an elevation of a cardiac specific enzyme such as creatine kinase to a level greater than twice the upper limit of normal for the local laboratory, or the elevation of serial non-specific enzymes to a level greater than twice the upper limit of normal with an appropriate pattern of release in relation to the relevant symptoms. This elevation must be accompanied by a history of symptoms consistent with a myocardial infarction and/or cardiographic changes consistent with infarction. Rarely it is necessary for a clinician to need to make a judgment about a patient dying in hospital before significant enzyme release has occurred.

As we point out in the Acute Myocardial Infarction - A Core data Set,[2] the recognition of all patients admitted with myocardial infarction may be difficult for some hospitals. Norris, in an unpublished study from four South Coast Hospitals demonstrated that between 68% and 98% of patients admitted with myocardial infarction to those hospitals were admitted to the Cardiac Care Unit (CCU). How patients having infarction not going to CCU should be identified is a problem which requires a local solution. However this is achieved, accurate coding remains of paramount importance.

Adjustment for case mix in myocardial infarction is a unresolved problem. The work outlined by Lawrance and his colleagues may be a solution. We did not include clinical variables in the initial data set because there were no compelling data to show they would add to the analysis. However, the dataset is not static, and the addition of further fields was always anticipated. It may be that the simple and objective measures proposed by the EMMACE study group will be the first to be added. We will be shortly start collecting data on large numbers of patients with myocardial infarction in the National Audit, together with planned mortality flagging. The introduction of a robust case mix model will be potentially of great value to the National Audit.

J S Birkhead
Clinical Lead National Audit of Myocardial Infarction
Clinical Effectiveness and Evaluation Unit
Royal College of Physicians
London NW1 4LE, UK

References

(1) Lawrance RA. National Service Framework – core data set [Rapid response] Heart 18 August 2000.

(2) Birkhead JS, Norris RM, Quinn T, Pearson M, on behalf of the Coronary Heart Disease National Service Framework for coronary disease: Acute Myocardial Infarction - a core data set for monitoring standards of care. Royal College of Physicians, London. December 1999.

Dear Editor

The case described by Blommaert et al makes interesting reading. Inadvertent left ventricular (LV) pacing following attempted placement of a lead in the right ventricle (RV) is a known occurrence. It is vital to recognise the problem to institute appropriate therapeutic measures, realising however that often right bundle branch block (RBBB) pattern results from normal RV pacing. It would however be interesting to point out the following points, if only for a purely academic exercise.

First, it is obviously important in such cases to study the 12 lead ECG as it is known that even normal RV pacing can lead to right bundle branch block (RBBB) patterns on the ECG, which can often be corrected by placement of leads V1 and V2 1 interspace lower than normal. The FRONTAL QRS AXIS and the PRECORDIAL transition are important determinators of the site of the lead.[1]

Thus, a frontal QRS axis from 0 to -90 and a precordial QRS tansition by lead V3 points to a lead which is still sited in the RV septum/apex pacing with a positive predictive accuracy of 95%, often necessitating no further intervention. If however, the QRS tansition is after V4, it is more likely to be in the posterior LV or a coronary vein.

A frontal QRS axis from -90 to -180 localises the lead to the LV in practically all cases. A precordial transition by V3 results from a pacing site in the distal anterior LV or the LV apex. A precordial transition after V3 results from pacing lead in the inferior LV.

A frontal QRS axis from 90 to 180 results from pacing in the anterior/anterolateral LV.

Second, a 12 lead ECG and a frontal and lateral x ray (or fluoroscopic position of the lead post implant) are vital for early detection of malpositioned leads. A posterior loop of the lead in the LAO view or a more superior course in the AP view (as it courses across the RA-LA-LV) are important pointers.

Third, it would be interesting to know about the ECG of the reported patient immediately following the implant, as it would have probably helped make the diagnosis right away (RBBB pattern, frontal QRS axis to the right, and precordial transition after V4 localising it to be in the LV)

Aditya Kapoor

Reference

(1) Coman JA, Trohman RG. Incidence and electrocardiographic localisation of safe right bundle branch block configurations during permanent ventricular pacing. Am J Cardiol 1995;76:781-4.

Dear Editor:

Dr Gavaliatsis points out the severe limitations that we still face in the exact diagnosis of monogenic diseases causing ventricular arrhythmias, like Brugada syndrome and the long QT syndrome. In Brugada syndrome it seems that we have a pharmacologic challenge (iv flecainide, ajmaline or procainamide) to unmask the phenotype. Unfortunately, that is not so in the long QT syndrome. But even with the pharmacologic challenge I agree with Dr Gavaliatsis that there may exist a problem of sensitivity and specificity in the diagnosis that will only be uncovered by exact knowledge of the genotype. But we need more than genetic analysis to make the correct correlations.

It starts with
1. The correct clinical diagnosis (something no that easy sometimes, particularly in the long QT syndrome), it continues by
2. Showing a change in the genetic code - for instance in the gene SCN5A encoding for the human cardiac sodium channel - and ends by
3. Expressing the mutation to show its functional consequences.

Of course, the diagnostic chain is only closed at the time that the functional consequences of the mutation turn out to make sound pathophysiologic sense, that is, they correlate with the clinical diagnosis and the known consequences of the disease. Mutation "hunters" seem to forget more and more frequently step 3. They report results that rather confuse instead of clarifying the many scientific questions that still remain. Publication of "mutations" without functional analysis to exclude among others, polymorphisms and non-significant changes in DNA sequences should be avoided by all serious scientific journals.

The points by Dr Gavaliatsis are well taken but a simple answer will not become available instantaneously. Meanwhile it remains the duty of the physician to protect patients with a Brugada phenotype against sudden death. It is a matter of medical phylosophy: When we do not know the patient should not become the victim of our ignorance. Implanting a defibrillator too much is not nice, but seeing a young individual succumb suddenly to ventricular fibrillation because a defibrillator was not implanted is much worse.

Prof Dr Pedro Brugada