Introduction and Concept of the Book
During the last decades the socalled ‘direct’ and ‘imaging’ diagnostic methods, such as coronary angiography, echo/color Doppler, scintigraphy, computer tomography and magnetic resonance imaging, have contributed to improve diagnostic accuracy in cardiac
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M. Gertsch, The ECG © Springer-Verlag Berlin Heidelberg 2004
coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG) before an ECG has been performed? In many cases an exercise ECG is required, although the potential of this test is limited in detecting ischemia. The immediate ECG diagnosis of acute infarction has become more urgent since the application of emergency PTCA and thrombolysis, the latter also in regional hospitals. Conduction disturbances as second degree AV block, bundle branch block and fascicular blocks represent another unique domain of the ECG. These conduction block patterns have a major clinical significance as potential precursors of a complete AV block. Sometimes, a severe electrolyte imbalance (potassium, calcium) is first detected in the ECG. In 70-90% of cases pericarditis is confirmed or diagnosed by the ECG. Particular characteristics in the 12 lead ECG allow the distinction of ventricular tachycardia and supraventricular tachycardia with aberration in about 90%. Many other ECG patterns of clinical significance are discussed in this book. Thirdly, the ECG pattern may give hints for tachyarrhythmias which are not yet present. Examples: Pre-excitation (shortened PQ interval with delta wave in the QRS complex --+ arrhythmias in the (WPW) syndrome. Prolonged QT interval ('long QT') --+ polymorphous ventricular tachycardia of the type 'tors ades de pointes' . Incomplete right bundle branch block pattern combined with marked ST elevations in leads VIN 2 (Brugada syndrome) --+ ventricular tachycardias with possible fibrillation and sudden death.
1.
Only 50-60% of acute and old myocardial infarctions can be diagnosed in the ECG on the basis of usual criteria. This is not surprising. On the contrary, the relatively high per-
centage is striking, considering that the routine ECG is a highly indirect method. Moreover, the study of more complex infarction patterns should allow a correct diagnosis in over 70% of cases. 2. It is obvious that the echocardiogram (by direct measurement) can better determine the dimensions and the wall thickness of all four heart chambers than the ECG. Famous indices for the detection of left ventricular hypertrophy as Sokolow's, Lyon's and Romhilt's point score indexes have revealed a very low sensitivity and good to moderate specificity. It is time to realize this. 3. 40 years ago even complex congenital heart diseases were diagnosed on the basis of clinical findings (especially auscultation), x-rays and, of course, the ECG. Heart catheterization, including angiography, has initiated a revolution. Today this field has become a domain of echo/Doppler. 4. The diagnosis of acute pulmonary embo!ism should most certainly not be based on an ECG alone. 5. Isolated alterations of the repolarization (T wave and ST segment) are unspecific and insensitive overall. The most important exception is the typical ECG pattern of an acute infarction. Generally, changes of ST and T segments should only be interpreted in the context of other ECG abnormalities (especially o
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