Latest advances in electrocardiology

Ljuba Bacharova
MD PhD MBA
International Laser Centre
Bratislava, Slovak Republic

Electrocardiology (ECG) is the science studying all the aspects of the electrical field generated by the heart. Each heartbeat is triggered by a spontaneous electrical impulse, this electrical impulse spreads across the myocardium and the electric field is recorded as an electrocardiogram. Electrocardiography was introduced at the end of the 19th century, and since then a huge body of knowledge and experience has been gained. ECG is currently the established standard diagnostic method not only in cardiology but in any medical and experimental discipline requiring evaluation and/or monitoring of vital functions.

Recent developments and potential impact on the provision of care
ECG has undergone rapid development, which reflects both progress in ECG itself as well as progress in other sciences and technology. The latest advantages in ECG can be framed into three main areas:

• Optimisation of the recording, processing and interpretation of the routine, classical 12-lead electrocardiogram.
• ECG signal processing and modelling going beyond the “classical” ECG curves: ECG imaging and multimodal imaging.
• New knowledge: moving beyond the “classical” ECG understanding of processes related to the cardioelectric field.
  

Optimisation of the recording, processing and interpretation of routine ECG
Electrocardiography is irreplaceable in its ability to provide information on heart rhythm, arrhythmias, including life-threatening arrhythmias, and conduction defects, as well as being reliable and providing early information in many acute clinical situations, such as in myocardial infarction. This area of electrocardiography benefits from the experience and knowledge gained – diagnostic criteria are well established and generally agreed, and the degree of automated diagnostic interpretation is very high.

The main characteristics of this area of electrocardiography are miniaturisation of devices and automated diagnostic interpretation, offering a broad spectrum of possibilities for diagnostics, monitoring and consequent intervention, including defibrillation. These include implantable devices, mobile transportable devices, continuous monitoring, home monitoring, online ECG registration and diagnostics, telemetry and many others. The diagnostic criteria and the resulting interventions are continually updated in accordance with new knowledge.

ECG signal processing and modelling going beyond the “classical” ECG curves: ECG imaging and multimodal imaging
Since the hexaxial system of coordinates of the classical 12-lead electrocardiogram provides a complicated virtual concept for understanding the relation between individual ECG curves and the heart, the progress in technology and informatics enables electrocardiology to go far beyond the “classical” ECG curve. Processing a great amount of data in real time has been made possible by powerful computers and advanced graphical software. Both ECG imaging and multimodal imaging methods are rapidly evolving.

The methods of imaging electrical processes in the heart range from complicated models to simple ones. Ramanathan et al(1) developed a method of noninvasive electrocardiographic imaging for cardiac electrophysiology and arrhythmia, allowing calculation and graphical presentation of the electrical activity on the epicardium, processing ECG data recorded by 200 electrodes from the body surface. On the other hand, Titomir and Ruttkay-Nedecky(2) elaborated the graphical presentation of the sequence of the electrical activation of the heart using three orthogonal leads.

The graphical presentation of the electrical activity of the heart broadens the understanding and analysis of the electrocardiogram, since it provides images comparable with those obtained by other imaging methods used in cardiology (see Figure 1). The superimposition of electrocardiogram and other diagnostic techniques complementary to electrocardiography provides a higher level of information on the relation between structural and functional characteristics of the heart. Consequently it creates a basis for applying advanced methods of analysis, such as pattern recognition, allowing better utilisation of different imaging modalities in routine clinical problems.

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New knowledge on the processes underlying the generation of electrical impulses in the heart and its propagation under normal and pathological conditions – moving beyond the “classical” ECG understanding of active and passive properties of myocardium
During the past few years, a great amount of knowledge on active and passive electrical properties of myocardium has been summarised, especially in relation to arrhythmias, going deeply into subcellular processes.(3) The term “electrical remodelling” has been introduced, comprising complex changes in active and passive electrical properties of myocardium, including cardiac microstructure, ion channels, energy metabolism and gene expression. Based on this knowledge, the diagnostic power of ECG is being re-evaluated even in those areas of clinical diagnostics where ECG was considered to be of limited value, such as in left ventricular hypertrophy.(4)

Implications for hospital services provision
The current situation in hospital electrocardiography is characterised by a high degree of computerisation and automation of ECG signals, both in ECG diagnostics and in patient monitoring. However, the strategies of hospitals have to take into account the rapid progress in all three above-mentioned areas. The increased number of devices available for ECG telemonitoring and home monitoring, the techniques of ECG imaging and multimodal imaging moving gradually from research centres into practical clinical diagnostics, will require technical and personal support for recording, transmission, analysis, interpretation, archiving and sharing ECG data, including the management of early and effective intervention. In addition, ECG systems should be sufficiently flexible to follow the progress in diagnostics to incorporate the increasing amount of knowledge and to continually increase the quality of diagnostics, monitoring, evaluation of the effect of therapy, emergency intervention, education and research.

References

1. Ramanathan C, Ghanem RN, Jia P, Ryu K, Rudy Y. Noninvasive electrocardiographic imaging for cardiac electrophysiology and arrhythmia. Nat Med 2004;10:422-28.
2. Titomir LI, Ruttkay-Nedecky I. Chronotopography: a new method for presentation of orthogonal electrocardiograms and vectorcardiograms. Int J Biomed Comput 1987;20:275-82.
3. Kleber AG, Rudy J. Basic mechanisms of cardiac impulse propagation and associated arrhythmias. Physiol Rev 2004;84:431-88.
4. Bacharova L. Electrical and structural remodeling in left ventricular hypertrophy – a substrate for a decrease in QRS voltage? ANE 2007;12:260-73.