ST elevation in recovery post exercise with normal coronary arteries.

We present the case of a 45-year-old healthy man who successfully completed three stages of the Bruce protocol but developed inferolateral ST segment elevation in the recovery phase. The ECG change was associated with a marked drop in blood pressure. He underwent emergency coronary angiography which revealed normal coronary arteries. It is likely that post-exercise hypotension triggered coronary spasm which caused the ST segment elevation. Alternatively, coronary spasm may have been the primary event, inducing sufficient myocardial ischaemia to cause a marked drop in blood pressure. Exercise tolerance testing is often a reliable test to rule out reversible myocardial ischaemia. While the physician is focused on ischaemic changes or rhythm abnormalities developing during the exercise phase, the recovery period is just as important and requires as much vigilance. Coronary vasospasm can result in significant ST changes and haemodynamic compromise at any point during the test, and the ECG traces can be indistinguishable from a classic ST elevation myocardial infarction, as in the present case.

Graphical representation of QT rate correction formulae: an aid facilitating the use of a given formula and providing a visual comparison of the impact of different formulae.

The QT interval on the electrocardiogram is an increasingly important measurement, especially in relation to drug action and interaction. The QT interval varies inversely as the heart rate and numerous rate correction formulae have been proposed. It is difficult to compare the effect of applying different formulae at different heart rates and for different measured QT intervals. A simple graphical display of the results from different formulae is proposed. This display is dependent on the concept of the absolute correction factor. This graphical presentation is useful (a) in comparing the effect of the application of different formulae and (b) in directly reading the correction produced by any individual formula.

Inadvertent interchange of electrocardiogram limb lead connections: analysis of predicted consequences part II: double interconnection errors.

Limb lead connection errors are known to be very common in clinical practice. The consequences of all possible single limb lead interconnection errors were analyzed in an earlier publication (J Electrocardiology 2008;41:84-90). With a single limb lead interconnection error, 6 combinations of limb lead connections are possible. Two of these combinations give rise to records in which the limb lead morphology is uninterpretable. Such records show a "flat line" in lead II or III. Three of the errors give rise to records that are fully interpretable once the specific interconnection error has been identified (although one of the errors cannot reliably be recognized in the absence of a previous record for comparison). One of the errors produces no change in the electrocardiogram recording. In all cases, the precordial leads are interpretable, although there are very minor changes in the voltages. This communication predicts the changes in limb lead appearances consequent upon all possible double limb lead interchanges and illustrates these with records electively taken with such double interconnection errors. There are only 3 possible double limb lead interconnection errors. In 2 of the possible combinations, interpretation of the limb leads is impossible, and each of these errors gives rise to a flat line in lead I. In the third combination, the record is fully interpretable once the abnormality has been identified. In all 3 types, the precordial leads are interpretable, although there are very minor changes in the voltages.

Spurious atrial tachycardia in a pilot. Prediction of the artifactual appearances in all twelve leads, when a single limb lead is the source of the artifact.

A routine screening electrocardiogram on a amateur pilot revealed what was initially thought to be an episode of atrial tachycardia. Minutes later, the record was within normal limits. The initial reading contained an artifact. A clear explanation of the distribution (within the 12 leads) of the artifact is given. The case illustrates that if an artifact is produced at any 1 of the 3 limb lead connections, it is possible to predict the size of the artifact in all 12 simultaneously recorded leads.