The Normal ECG, and Introduction to Sinus Rhythm

This chapter is arguably the most important chapter, as it lays the proverbial groundwork for all chapters that come after it. More specifically, this chapter provides an imperative understanding of a normal electrocardiogram (ECG), so that learners of all backgrounds will start with the same structure in mind. Starting from the primary wave (P-wave), QRS complex, and T-wave, and all the intervals in-between, this introductory section will demonstrate the “anatomy” of the ECG and elucidate the relevant terminology for proper ECG interpretation. Additionally, this component of the book discusses the concept of P-wave abnormalities, which focuses primarily on the electrocardiographic changes expected with atrial enlargement. Moreover, this chapter also introduces the definition of sinus rhythm—a notion that will be carried through virtually every chapter of the work. This idea is especially important in juxtaposing sinus rhythm against ectopic atrial rhythms, a clinical entity that can be easily misdiagnosed. This first chapter serves as the perfect framework for the reader's journey through ECG interpretation.