Cardiology: Introduction to Medical Terminology

Definition and Scope

Cardiology is the medical specialty focused on the study, diagnosis, and treatment of the cardiovascular system, which includes the heart and blood vessels. Understanding the terminology is essential for effective communication in healthcare settings.

• Cardi/o-: Prefix meaning heart

• -logy: Suffix meaning study of

• Cardiology: The study of the heart and its functions

Cardiovascular System Overview

Structure and Function

The cardiovascular system consists of the heart and an extensive network of blood vessels. It is responsible for circulating blood throughout the body, delivering oxygen and nutrients, and removing waste products.

• Heart: Central organ that pumps blood

• Blood vessels: Arteries, veins, and capillaries that transport blood

• Continuous circulation: Ensures all body tissues receive oxygenated blood and nutrients

Circulation of the Blood

Pathways of Blood Flow

Blood circulates through two main pathways: pulmonary and systemic circulation. The heart acts as a double pump, sending deoxygenated blood to the lungs and oxygenated blood to the rest of the body.

• Pulmonary circulation: Right side of the heart pumps deoxygenated blood to the lungs for oxygenation

• Systemic circulation: Left side of the heart pumps oxygenated blood to the body

• Key structures: Atria, ventricles, valves, arteries, veins, and capillaries

Anatomy of the Heart

Location and External Features

The heart is located in the thoracic cavity, behind the sternum and between the lungs. It is roughly the size of a fist and has an irregular external surface with mounds and grooves corresponding to internal chambers and vessels.

• Chambers: Four chambers (right/left atria and right/left ventricles)

• Grooves: Contain fat, blood vessels, and nerves

Heart Wall Layers

The heart wall is composed of three main layers, each with distinct functions:

• Pericardium: Two-layered membrane forming the pericardial sac (parietal and epicardium layers)

• Pericardial fluid: Lubricates and reduces friction between layers

• Myocardium: Thick muscular layer responsible for contraction

• Endocardium: Smooth inner lining of chambers and valves

Internal Anatomy: Chambers and Septum

The heart contains four chambers separated by the septum:

• Atria: Upper chambers that receive blood

• Ventricles: Lower chambers that pump blood out

• Septum: Central wall dividing right and left sides

Heart Valves

Valves ensure unidirectional blood flow through the heart:

• Tricuspid valve: Between right atrium and right ventricle

• Pulmonary valve: Between right ventricle and pulmonary arteries

• Mitral (bicuspid) valve: Between left atrium and left ventricle

• Aortic valve: Between left ventricle and aorta

Anatomy: Thoracic Cavity and Mediastinum

Location of the Heart and Great Vessels

The heart is situated within the mediastinum, a central compartment in the thoracic cavity. This area also contains the great vessels, esophagus, trachea, and thymus.

• Mediastinum: Central area between the lungs

• Great vessels: Aorta, superior/inferior vena cava, pulmonary arteries/veins

Anatomy: Blood Vessels

Types and Functions

Blood vessels are classified based on their structure and function:

• Arteries: Carry blood away from the heart; thick muscular walls for high pressure

• Capillaries: Smallest vessels; site of exchange between blood and tissues

• Veins: Carry blood toward the heart; thinner walls, often with valves

Arteries: Structure and Regulation

Arteries branch into smaller arterioles and are responsible for distributing oxygen-rich blood. They can constrict or dilate to regulate blood pressure.

• Vasoconstriction: Narrowing of arteries, increases blood pressure

• Vasodilation: Widening of arteries, decreases blood pressure

Major Arteries and Veins

The aorta is the largest artery, and the superior/inferior vena cava are the largest veins. Coronary arteries supply the heart muscle itself.

Veins: Structure and Function

Veins return deoxygenated blood to the heart. Many veins have valves to prevent backflow, especially in the limbs.

• Venules: Small veins that collect blood from capillaries

• Valves: Ensure one-way flow toward the heart

Circulation Pathways

Pulmonary and Systemic Circulation

Blood flows through two main circuits:

• Pulmonary circuit: Right ventricle → pulmonary arteries → lungs → pulmonary veins → left atrium

• Systemic circuit: Left ventricle → aorta → body tissues → veins → right atrium

Conduction System of the Heart

Electrical Pathways

The heart's rhythm is controlled by specialized cells that generate and conduct electrical impulses:

• SA node (sinoatrial node): Pacemaker, initiates heartbeat

• AV node (atrioventricular node): Delays impulse before passing to ventricles

• Bundle of His, bundle branches, Purkinje fibers: Distribute impulse through ventricles

Physiology: Heartbeat and Regulation

Cardiac Cycle

The cardiac cycle consists of two main phases:

• Systole: Contraction phase, blood is pumped out

• Diastole: Relaxation phase, chambers fill with blood

Heart rate is regulated by the autonomic nervous system:

• Parasympathetic: Releases acetylcholine, slows heart rate

• Sympathetic: Releases norepinephrine and epinephrine, increases heart rate

Common Cardiovascular Diseases

Angina Pectoris

Angina is chest pain caused by reduced blood flow to the heart muscle, often triggered by exertion or stress.

Peripheral Edema

Swelling in the lower legs and feet, often a sign of right-sided heart failure.

Myocardial Infarction (Heart Attack)

Occurs when blood flow to part of the heart is blocked, causing tissue death due to lack of oxygen.

Aneurysm

A localized dilation or ballooning of a blood vessel wall, often in the aorta, which can rupture if untreated.

Atherosclerosis

Build-up of fatty plaques in arteries, narrowing the lumen and restricting blood flow.

Hypertension

Chronic high blood pressure, a major risk factor for heart disease and stroke.

Varicose Veins

Enlarged, twisted veins, often in the legs, due to valve failure and blood pooling.

Arrhythmias

Abnormal heart rhythms, which can be detected on an electrocardiogram (ECG).

• Bradycardia: Slow heart rate

• Tachycardia: Fast heart rate

• Fibrillation: Irregular, uncoordinated contractions

• Asystole: Absence of heartbeat

Laboratory and Diagnostic Procedures

Cardiac Exercise Stress Test

Assesses heart function under physical stress using a treadmill or bicycle, monitoring ECG and blood pressure.

Electrocardiography (ECG/EKG)

Records the electrical activity of the heart to detect arrhythmias, ischemia, and other cardiac conditions.

Ultrasonography and Echocardiography

Uses sound waves to visualize blood flow and heart structures. Color flow duplex ultrasonography shows both anatomy and blood flow direction/velocity.

Medical and Surgical Procedures

Measuring Blood Pressure

Blood pressure is measured using a sphygmomanometer and stethoscope. Systolic pressure reflects ventricular contraction; diastolic pressure reflects resting pressure.

Automatic External Defibrillator (AED)

AEDs are portable devices used to treat sudden cardiac arrest by delivering an electric shock to restore normal rhythm.

Pulse Points

Pulse points are locations where arterial pulses can be felt, used to assess heart rate and circulation.

Pacemaker

A pacemaker is an implanted device that regulates heart rhythm in patients with arrhythmias.

Open Heart Surgery

Involves opening the chest to access the heart for procedures such as valve replacement or coronary artery bypass.

Drugs and Pharmacology

Digitalis Drugs

Digitalis drugs, derived from the foxglove plant (Digitalis purpurea), are used to treat heart failure and arrhythmias by increasing the force of heart contractions.

Summary Table: Major Cardiovascular Terms