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With special interest I read the paper on postural electrocardiographic abnormalities in the Netherlands Heart Journal.1 For me a feast of reminiscence, looking at the authors and the subtle way they addressed a pitfall in electrocardiography. A relief too, in a time where there is little room for shading in a continuous strive for so-called ‘hard data’ to be wrapped in the shiny paper of a perfect decision-tree to speak for itself. Nevertheless I would like to add some comments on the case presented here. The electrocardiogram in upright position shows alternating T waves (V1) and biphasic T-wave abnormalities, especially in the lateral precordial leads, suggesting neuroendocrine-induced heterogeneity in repolarisation rather than ischaemia-dependent alterations. This autonomic effect on ventricular repolarisation could well be the result of a combination of mental and emotional stress (subjected to a ‘conclusive’ cycle ergometer test) and the augmented sympathetic activity of the upright posture. Measurements of QTc intervals at rest, in upright position and during exercise are of interest because they may provide an additional argument for sympathetic tonisation in this case. Because effects of autonomic imbalance are volatile, the postural abnormalities are not very likely to be reproducible as they are, but information on this point is lacking.
Furthermore, the borderline hypertension before exercise, the history of palpitations, an enhanced sinus rhythm, non-specific ST-T changes and the presence of premature ventricular beats, all point in the direction of autonomic hyperactivity, which may warrant future monitoring.2 In this respect, heart rate variability, the amount of heart rate fluctuations around the mean heart rate, during Holter monitoring and blood pressure during exercise are more than only of scientific interest.
Besides the tendency for normalisation of suspected ST changes, the electrocardiogram during stress testing showed two other distinct features. There is a marked change in R-wave amplitude and a striking electrical alternans. Although R-wave amplitude changes during exercise are not an efficient tool in detecting ischaemia, it can be helpful to separate the chaff from the wheat, in reducing falsenegative and false-positive responses according to ST-segment criteria.3 Looking at the standard leads it would be a simplification to ascribe the electrical alternans to forced respiration. Sympathetic stimulation increases the maximum slope of electrical restitution (relating action potential duration to diastolic interval) and electrical alternans but decreases the effective refractory period and ventricular fibrillation threshold whilst vagus nerve stimulation has opposite effects.4 In the long run and looking at the data presented, stories like these may be less innocent than previously thought.5
C. van Tellingen
Duke Ellingtonlaan 23, 4702 KG Roosendaal,the Netherlands
The comments of Dr van Tellingen are interesting. It was concluded that the repolarisation abnormalities in the pre-exercise ECG (figure 2) represent postural ECG abnormalities, which is demonstrated by the disappearance of these ST abnormalities during exercise and the accomplishment of a normal exercise tolerance. It is possible that the vasoregulatory abnormalities with the ST alterations are enhanced by stress but there are no investigational data. Above all, we must avoid subjecting our patients to mental stress, induced by a so-called ‘conclusive’ cycle ergometric testing as suggested in the comments. The ultimate clinical importance of the results of an exercise ECG is dependent on other, non-exercise dependent, variables as in most Bayesian situations. A possible incidental stress period in this situation must be discerned to the heart syndrome (also called Da Costa’s syndrome, neurocirculatory asthenia (NCA) or Soldiers Heart). This syndrome1 is characterised by anxiety, fatigue, emotional stress, and physiological characteristics such as arterial hypertension, tachycardia and breathlessness, and sometimes hyperventilation. The syndrome can present with ‘aspecific’ ST abnormalities at rest, worsening during exercise. To the contrary of the postural syndrome, the exercise tolerance is low in NCA.
The second part of the comments by Dr van Tellingen as to the measurement of the R-wave importance. In 1978 Bonoris drew attention to the clinical importance of the analysis of the R wave in exercise ECG.2 In the normal situation during exercise the R amplitude diminishes but it sometimes increases during exercise-induced ischaemia. In our studies in the 1980s3 it appeared that the predictive value of this analysis was poor. The predictive value, however, could increase significantly if we analysed the ST and R parameters in concordance: the combination of an increasing R-wave amplitude with an ischaemic ST segment during exercise was highly predictive as to ischaemic heart disease. Returning to our case with the postural ST-wave abnormality, the R-wave analysis was of no clinical importance due to the fact that the repolarisation did ‘normalise’ during exercise and thus the opportunity of a concordance was not present.
VieCuri Medisch Centrum for Noord-Limburg, Venlo, the Netherlands
St. Antonius Hospital, Nieuwegein, the Netherlands
Retired cardiologist, Gezichtslaan 58, 3723 GG Bilthoven, the Netherlands