Electrocardiography in Ischemic Heart Disease

Clinical and Imaging Correlations and Prognostic Implications

Miquel Fiol-Sala, Yochai Birnbaum, Kjell Nikus, Antoni Bayés de Luna

• Publisher: Wiley-Blackwell
• Year: 2019
• ISBN:
  9781119422280
• Edition: 2
• Topic: Medicina
• Subtopic: Cardiologia

A fresh assessment of ischemic electrocardiography, its prognostic correlations, and the concepts and principles that underlie its use

The electrocardiogram (ECG) is integral to the accurate diagnosis and optimal management of patients with ischemic heart disease. Picking up a wide range of indicators, it provides valuable prognostic data to cardiologists and emergency medicine specialists for whom ECG readings are a trusted and everyday resource. Electrocardiography in Ischemic Heart Disease is designed to help enhance such clinicians' understanding of ECG recordings and their relationship to anatomical patterns of myocardial ischemia, thereby facilitating the continued improvement of patient care.

For this new edition, the book's globally recognized team of authors has revised and expanded the original text to bring it up to date with the cardiology of today. Practical explanations of electrophysiological mechanisms, ischemic insults, and arterial occlusions are placed in the context of the ECG's day-to-day use, while full-color images illustrate core concepts in a vivid and instructive manner. This essential guide:

• Demonstrates correlations between ECG recordings and anatomical patterns of myocardial ischemia
• Covers STEMI, special forms of NSTEMI, and Q waves
• Describes electrocardiographic patterns of ischemia, injury, and infarction
• Includes full-color images
• Explores advanced techniques such as contrast-enhanced cardiac magnetic resonance

Electrocardiography in Ischemic Heart Disease is an indispensable resource for both trainee and practicing cardiologists, emergency medicine physicians, and any clinicians involved in the diagnosis and management of ischemic heart disease.

Part I
The ECG Changes Secondary to Ischemic Heart Disease: Electrophysiologic Bases

1
Anatomy of the Heart: The Importance of Imaging Techniques Correlations

The surface electrocardiogram (ECG) in both the acute and chronic phase of ischemic heart disease (IHD) may give crucial information about the coronary artery involved and the area‐at‐risk for myocardial injury. Knowing the anatomy of the heart, especially the ventricular walls and coronary tree, helps to understand the various ECG patterns present in IHD. However, the electric activity of the heart is influenced by numerous cardiac and non‐cardiac factors. Structural (chamber size, hypertrophy, presence of diffuse fibrosis, or localized scar, presence of pericardial effusion, etc.), functional and metabolic (ischemia, post‐ischemic stage, inflammation) aspects and diseases of the conduction system (CS) can all modify the ECG. Non‐cardiac factors include the position of the heart in the chest (horizontal position in obese patients, vertical in patients with emphysema, altered anatomy after pulmonary surgery, atelectasis, or pneumothorax), the distance of the electrodes from the heart and the width of the chest wall (effusion, adipose tissue, radical mastectomy, etc.), electrolyte imbalance and drug effects. This information together with the ECG‐clinical correlation is very important for diagnosis and risk stratification, as will be demonstrated in this book.

For centuries, since the pioneering works of Vesalio, Leonardo da Vinci, Lower, and Bourgery‐Jacob, pathology has been a unique method to study the anatomy of the heart. Since the end of the nineteenth century, the visualization of the heart in vivo has been possible by X‐ray examination. The last 40–50 years started the era of invasive imaging techniques with cardiac catheterization, including coronary angiography, and non‐invasive imaging techniques, first with echocardiography and later with radionuclide studies, computed tomography(CT) and cardiovascular magnetic resonance (CMR) imaging. These techniques have opened up new horizons to study, not only the anatomy of the heart, coronary arteries and great vessels, but also myocardial function, metabolism and perfusion, and the characterization of the valves, pericardium, etc.

From an ECG standpoint, coronary angiography (Figure 1.1) is especially important in the acute phase for diagnosing the disease and correlating the site of occlusion with the ST‐segment deviations. It is also useful in the chronic phase of the disease. However, in the chronic phase of Q‐wave myocardial infarction (MI) the ECG does not usually predict the state of the coronary tree, because revascularization has often modified the characteristics of the occlusion responsible for the MI (Basso and Thiene 2006). Moreover, coronary angiography is insensitive for detecting minor collaterals that could attenuate ischemia. Coronary angiography does not give information about the myocardium and, thus, cannot directly assess the extent and severity of ischemia, especially in the acute phase of acute coronary syndromes (ACSs).

In patients with non‐ ST‐elevation ACS, the culprit lesion is not always identifiable by angiography, especially in patients without active ischemia during the time of angiography or with multi‐vessel disease. Cine angiography of the left ventricle (LV) may give information for identifying hypokinetic or akinetic areas, but in practice, echocardiography is the preferred technique for this purpose. After the acute phase of myocardial ischemia, hypo‐/akinetic myocardial segments usually corelate with the extent of tissue injury (Shen, Tribouilloy, and Lesbre 1991a,b; Takatsu et al. 1988; Takatsu, Osugui, and Nagaya 1986; Warner et al. 1986).

Computed coronary tomography angiography (CTA) is an alternative to invasive angiography to explore the coronary artery anatomy, especially in situations with low likelihood of need for percutaneous coronary intervention (PCI) (Figure 1.1). CTA may provide additional diagnostic information for clinical decision‐making in contemporary stable chest pain patients with intermediate pre‐test probability for IHD (Hoffmann et al. 2017). In additional to narrowing, CTA can provide information on coronary distribution, including abnormalities in the origin and course of the arteries, and presence of coronary aneurysms. However, the accuracy of assessing the severity of coronary stenosis in highly calcified lesions and within stents is reduced.

Figure 1.1 (A) Normal case: coronary angiography (left) and three‐dimensional CTA (right) showing normal left anterior descending (LAD, arrow) and left circumflex (LCX) coronary arteries. The latter is partially covered by the left appendix in CTA. (B) Normal case: coronary angiography (left) and CTA (right...