Author: Saim Khalid

Introduction The Frank–Starling law of the heart is a fundamental principle of cardiovascular physiology that describes how the stroke volume of the heart adjusts to changes in venous return. It asserts that the force of ventricular contraction is proportional to the initial length of cardiac muscle fibers (preload). This intrinsic property enables the heart to…

The pressure-volume (P-V) loop is a powerful graphical tool used in cardiology and physiology to analyze the mechanical function of the heart. It provides an integrated view of ventricular pressure, volume, and cardiac work throughout the cardiac cycle. By plotting ventricular pressure against ventricular volume in real time, P-V loops offer critical insights into contractility,…

Introduction Cardiac output (CO) and stroke volume (SV) are central concepts in cardiovascular physiology, representing the heart’s ability to supply oxygenated blood to meet the body’s metabolic demands. Cardiac output is defined as the volume of blood ejected by the heart per minute, whereas stroke volume is the volume ejected per beat. Together, these parameters…

Introduction Heart sounds are audible vibrations produced by the cardiac cycle, primarily generated by valve closure, blood flow, and myocardial movement. They are fundamental to cardiovascular assessment, providing critical information about heart function, valvular integrity, and hemodynamics. Traditionally, four heart sounds are recognized: S1, S2, S3, and S4, each reflecting specific phases of the cardiac…

The heart is a dynamic organ whose primary function is to pump blood efficiently throughout the body. This pumping occurs in a coordinated cycle known as the cardiac cycle, which consists of alternating phases of contraction (systole) and relaxation (diastole). Ventricular systole, in particular, is the period during which the ventricles contract, generating sufficient pressure…

Introduction Cardiac function is a sophisticated interplay of electrical excitation, mechanical contraction, and hemodynamic forces. Among the fundamental events in the cardiac cycle, atrial systole and ventricular filling are essential for ensuring efficient ventricular preload and optimizing cardiac output. These phases occur during diastole, when the ventricles relax and accommodate incoming blood. While often overlooked…

Introduction The cardiac cycle is the sequence of mechanical and electrical events that occur during a single heartbeat, enabling the heart to efficiently pump blood throughout the systemic and pulmonary circulations. Each cycle ensures unidirectional blood flow, optimal ventricular filling, and effective stroke volume. Understanding the cardiac cycle is fundamental to cardiology, physiology, and clinical…

The heart is not only a mechanical pump but also a complex organ intricately regulated by the autonomic nervous system (ANS). Cardiac innervation is crucial for maintaining proper heart rate, conduction velocity, contractility, and overall cardiovascular homeostasis. Understanding cardiac innervation involves examining the sympathetic and parasympathetic inputs, as well as the cardiac plexus, which serves…

Introduction The left coronary artery (LCA) is a pivotal vessel supplying the majority of the left heart, including the left ventricle (LV), left atrium (LA), and interventricular septum (IVS). Its branches — most importantly the left anterior descending (LAD) and the left circumflex (LCX) — have critical anatomical and clinical significance. A thorough understanding of…

Introduction The right coronary artery (RCA) is one of the two main coronary arteries supplying the myocardium. Arising from the right aortic sinus, the RCA runs along the right atrioventricular (AV) groove, giving off multiple branches that supply the right atrium, right ventricle, sinoatrial (SA) and atrioventricular (AV) nodes, and parts of the interventricular septum.…