This chapter and the next examine one of the most important topics in electrocardiogram (ECG) analysis and clinical medicine, namely the diagnosis of myocardial ischemia and infarction (ischemic heart disease), a a The terms infarction and infarct are used interchangeably…
Recall that in the normal process of ventricular activation the electrical stimulus (signal) reaches the ventricles from the atria by way of the atrioventricular (AV) node and His–Purkinje system ( 1, 5 ). The first part of the ventricles to…
The first six chapters have been devoted to the basics of electrocardiograms (ECGs). From this point on, we focus attention primarily on the recognition and understanding of abnormal ECG patterns. This chapter discusses the ECG manifestations of enlargement and related…
Normal electrocardiogram (ECG) patterns in the chest and extremity leads were discussed in Chapter 5 . The general terms horizontal heart (or horizontal QRS axis ) and vertical heart (or vertical QRS axis ) were used to describe normal, individual variations…
The previous chapters reviewed the cycles of atrial and ventricular depolarization/repolarization detected by the electrocardiogram (ECG) and the standard 12-lead system used to record this electrical activity. This chapter describes the detailed appearance of the P–QRS–T patterns seen normally in…
As discussed in Chapter 1 , the heart produces electrical currents similar to the dry cell battery. A special recording instrument (sensor) such as an electrocardiograph can measure the strength or voltage of these currents and the way they are transmitted…
This chapter continues the discussion of electrocardiogram (ECG) basics introduced in 1, 2 . Here we focus on recognizing key components of the ECG in order to make clinically important measurements from these time–voltage graphs. Standardization (Calibration) of the ECG…
The first purpose of this chapter is to present two fundamental electrical properties of heart muscle cells: (1) depolarization (activation) and (2) repolarization (recovery). Second, in this chapter, and the next, we define and show how to measure the basic…
The electrocardiogram ( ECG or EKG ) is a special type of graph that represents changes in cardiac electrical activity from one instant to the next. Specifically, the ECG provides a time-voltage chart of the heartbeat. 10 seconds of ECG data…