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Definitions, Chapter Questions, Study Guide Questions, General Questions



Absolute refractory period

Corresponds with the onset of the QRS complex to approximately the peak of the T wave; cardiac cells cannot be stimulated to conduct an electrical impulse, no matter how strong the stimulus

Accessory pathway

An extra bundle of working myocardial tissue that forms a connection between the atria and ventricles outside the normal conduction system.

Action potential

A five-phase cycle that reflects the difference in the concentration of these charged particles across the cell membrane at any given time.

Acute arterial occlusion

A sudden blockage of arterial blood flow that occurs because of a thrombus, embolus, tumor, direct trauma to an artery or an unknown cause.

Acute coronary syndrome (ACS)

A term used to describe ischemic chest discomfort. ACS consists of 3 major syndromes: unstable angina, NSTEMI, and STEMI


Pressure or resistance against which the ventricles must pump to eject blood


Heigth (voltage) of a waveform on the ECG


Massive generalized body edema


Localized dilation or bulging of a blood vessel wall or wall of a heart chamber.

Anginal equilvalents

Symptoms of myocardial ischemia other than chest pain or discomfort.

Angina pectoris

Chest discomfort or other related symptoms of sudden onset that may occur because the increased oxygen demands of the heart temporarily exceeds the blood supply


Medications used to correct irregular heartbeats and slow hearts that beat too fast

Aortic valve

SL valve on the left of the heart; seperates the left ventricle from the aorta

Apex of the heart

Lower portion of the heart, tip of the ventricles (approximately the level of the fifth intercostal space); points leftward, downward and forward.


Term often used interchangeably with dysrhythmia; any disturbance or abnormality in a normal rhythmic pattern; any cardiac rhythm other than a sinus rhythm.


A chronic disease of the arterial system characterized by abnormal thickening and hardening of the vessel walls


A total absence of ventricular electrical activity


A form of arteriosclerosis in which the thickening and hardening of the vessel walls are caused by a buildup of fatty deposits in the inner lining of the large and middle-sized muscular arteries. (from 'athero' meaning gruel or paste)


Distortion of an ECG tracing by electrical activity that is noncardiac in origin (e.g., electrical interference, poor electrical conduction, patient movement)


Marked abdominal swelling from a buildup of fluid in the peritoneal cavity

Asynchronous pacemaker

Fixed rate pacemaker that continuously discharges at a preset rate reguardless of the patients intrinsic activity


Two upper chambers of the heart (singular: atrium)

Atrioventricular junction

The AV node and the nonbranching portion of the bundle of His

Atrioventricular node

A group of cells that conduct an electrical impulse through the heart; located in the floor of the right atrium immediately behind the tricuspid valve and near the opening of the coronary sinus

Atrioventricular sequential pacemaker

Type of dual chamber pacemaker that stimulates first the atrium , then the ventricle, mimicking normal cardiac physiology.

Atrioventricular valve

Valve located between each atrium and ventricle; the tricuspid seperates the right atrium from the right ventricle and the mitral (bicuspid) seperates the left atrium from the left ventricle.

Augmented limb lead

Leads aVR, aVL and aVF; these leads record the difference in electrical potential at one location relative to zero potential rather than relative to the electrical potential of another extremity, as in the bipolar leads


Ability of cardiac pacemaker cells to initiate an electrical impulse spontaneously without being stimulated from another source (such as a nerve)


Imaginary line joining the positive and negative electrodes of a lead


Straight line recorded on ECG graph paper when no electrical activity is detected

Base of the heart

Top of the heart; located at approximately the level of the second intercostal space


Waveform that is partly positive and partly negative

Bipolar limb lead

ECG lead consisting of a positive and negative electrode; a pacing lead with two electrical poles that are external from the pulse generator; the negative pole is located at the extreme distal tip of the pacing lead, and the positive is located several millimeters proximal to the negative electrode. The stimulating pulse is delivered through the negative electrode.

Blocked premature atrial complex

PAC not followed by a QRS complex

Blood pressure

Force exerted by the blood against the walls of the arteries as the ventricles of the heart contract and relax


Heart rate slower than 60 bpm


Blowing or swishing sound created by the turbulence within a blood vessel

Bundle branch block (BBB)

Abnormal conduction of an electrical impulse through either the right or left bundle branches

Bundle of His

Fibers located in the upper portion of the interventricular septum


Three or more sequential ectopic beats; also referred as a salvo or run


Regulation of an ECG machines stylus sensitivity so that a 1mV electrical signal will produce a deflection measuring exactly 10mm


Ability of a pacing stimulus to depolarize successfully the cardiac chamber being paced; with one to one capture, each pacing stimulus results in depolarization of the appropriate chamber

Cardiac arrest

Absence of cariac mechanical activity, confirmed by the absence of a detectable pulse, unresponsiveness, apnea or agonal, gasping respirations.

Cardiac cycle

Period from the beginning of one heart-beat to the beginning of the next; normally consisting of PQRST waves, complexes, and intervals

Cardiac output (CO)

Amount of blood pumped into the aorta each minute by the heart

Cardiogenic shock

A condition which heart muscle function is severly impaired, leading to decreased cardiac output and inadequate tissue perfusion


A disease of the heart muscle

Cardiovascular disorders

A collection of diseases and conditions that involve the heart (cardio) and blood vessels (vascular)


Having the characteristics of the parasympathetic division of the autonomic nervous system

Chordae tendineae

Thin strands of fibrous connective tissue that extend from the AV valves to the papillary muscles that prevent the AV valves from bulging back into the atria during ventricular systole (contraction)


A change in heart rate

Circumflex artery

Division of the left coronary artery

Compensatory pulse

Pause for which the normal beat after a premature complex occurs when expected; also called a complete pause


Several waveforms

Conduction system

A system of pathways in the heart composed of specialized electrical (pacemaker) cells


Ability of a cardiac cell to recieve an electrical stimulus and conduct that impulse to an adjacent cardiac cell


Ability of acrdiac cells to shorten, causing cardiac muscle contraction in response to an electrical stimulus

Coronary artery disease

Disease of the arteries that supply the heart muscle with blood

Coronary heart disease

Disease of the coronary arteries and their resulting complications, such as angina pectoris or acute myocardial infarction

Coronary sinus

Venous drain for the coronary circulation into the right atrium

Cor pulmonale

Right sided heart failure caused by pulmonary disease


Two consecutive premature complexes


Flow of electrical charge from one point to another

Cystic medial degeneration

A connective tissue disease in which the elastic tissue and smooth muscle fibers of the middle arterial layer degenerate


Protien molecules produced by white blood cells that act as chemical messangers between cells

Deep vein thrombosis (DVT)

Presence of a clot in the deep veins of the extremities


Therapuetic use of electric current to terminate lethal cardiac dysrhythmias

Delta wave

Slurring at the beginning of the QRS complex caused by prexcitation

Demand pacemaker

Synchronous pacemaker that discharges only when the patient's heart rate drops below the preset rate for the pacemaker


Movement of ions across a cell membrane, causing the inside of the cell to become more positive; an electrical event expected to result in contraction


Phase of the cardiac cycle in which the atria and ventricles relax between contractions and blood enters these chambers; when the term is used without reference to a specific chamber of the heart, the term implies ventricular diastole

Diastolic blood pressure

Pressure exerted against the walls of the large arteries during ventricular relaxation


The speed of conduction through the AV junction

Dual-chamber pacemaker

Pacemaker that stimulates the atrium and ventricle


An uncomfortable awarenes of ones breathing; shortness of breath or difficulty breathing


Any disturbance or abnormality in a normal rhythmic pattern; any cardiac rhythm other than a sinus rhythm.


Impulse(s) originating from a source other than the SA node

Electrical alternans

A beat-to-beat change in waveform amplitude on the ECG


Adhesive pads that contain a conductive gel and are applied at specific locations on the patients chest wall and extremities and connected by cables to an ECG machine


Elements or compounds that break into charged particals (ions) when melted or dissolved in water or another solvent


Innermost layer of the heart that lines the inside of the myocardium and covers the heart valves


Implies the presence of dilation or hypertrophy or both


Also know as the viseral pericardium; the external layer of the heart wall that covers the heart muscle


Term used when the sinus node slows or fails to initiate depolarization and alower pacemaker site spontaneously produces electrical impulses, assuming responsibility for pacing the heart

Essential hypertension

High blood pressure for which there is no cause identifiable; also called primary hypertension


Ability of cardiac muscle cells to respond to an outside stimulus


A brief loss of conciousness caused by a temporary decrease in blood flow to the brain


Small bundle of nerve fibers


The breakdown of fibrin, the main component of blood clots

Fine ventricular fibrillation

VF with fibrillatory waves less than 3mm in height

Fixed rate pacemaker

Asynchronous pacemaker that continuously discharges at a present rate regardless of the patients heart rate

Focal atria tachycardia

AT that begins in a small area (focus) within the heart

Great vessels

Large vessels that carry blood to and from the heart: superior and inferior venae cavae, pulmonary veins, aorta, and pulmonary trunk

Ground electrode

Third ECG electrode (the first and second are the positve and negative electrodes), which minimizes electrical activity from other sources

Heart disease

A broad term referring to the conditions affecting the heart

Heart failure

A condition in which the heart is unable to pump enough blood to meet the metabolic needs of the body

His-Perkinje system

Portion of the conduction system consisting of the bundle of His, bundles branches, and Purkinje fibers

Homan's sign

Pain and tenderness in the calf muscle on dorsiflexion of the foot

Hypertensive emergencies

Situations that require rapid (within 1 hour) lowering of blood pressure to prevent or limit organ damage

Hypertensive urgencies

Significant elevations in blood pressure with nonspecific symptoms that should be corrected within 24 hrs


Increase in the thickness of a heart chamber because of chronic pressure overload

Hypovolemic shock

Inadequate tissue perfusion caused by inadequate vascular volume

Indicative change

ECG changes seen in leads looking directly at the wall of the heart in an infarction


Death of a tissue because of an inadequate blood supply


A change in myocardial contractility

Intermittent claudication

Pain, cramping, muscle tightness, fatigue, or weakness of the legs when walking or during exercise


Waveform and a segment; in pacing, the period, measured in milliseconds, between any two desiganted cardiac events

Intrinsic rate

Rate at which a pacemaker of the heart normally generates impulses


Electrically charged particles


Decreased supply of oxygenated blood to a body part or organ

Isoelectric line

Absence of electrical activity; observed on the ECG as a straight line


Point where the QRS complex and ST segment meet

Junctional bradycardia

A rhythm that begins in the AV junction with a rate of less than 40 beats/min


Electrical connection attached to the body to record electrical activity

Malignant hypertension

Severe hypertension with signs of acute and progressive damage to end organs such as heart, brain, and kidneys


Located in the middle of the thoracic cavity; contains the heart, great vessels, trachea, and esophagus, among other structures; extends from the sternum to the vertebral column

Membrane potential

Difference in electrical charge across the cell membrane

Milliampere (mA)

Unit of measure of electrical current needed to elicit depolarization of the myocardium

Millivolt (mV)

Difference in electrical charge between two points in a circuit


Having the same shape

Multiformed atrial rhythm

Cardiac dysrhythmia that occurs because of impulses originating from various sites, including the SA node, the atria, and/or the AV junction; requires at least 3 different P waves, seen in the same lead, for proper diagnosis.

Myocardial cells

Working cells of the myocardium that contain contractile filaments and form the muscular layer of the atrial walls and the thicker muscular layer of the ventricular walls

Myocardial infarction (MI)

Necrosis of some mass of the heart muscle caused by an inadequate blood supply


Inflammation of the middle and thickest layer of the heart, the myocardium


Middle and thickest layer of the heart; contains the cardiac muscle fibers that cause contraction of the heart as well as the conduction system and blood supply


A chemical released from one nerve that crosses the synaptic cleft to reach a receptor


Dyspnea relieved by a change in position (either sitting upright or standing)


A normal chemical process in the body caused by the release of oxygen atoms created during normal cell metabolism


Artiicial pulse generator that delivers an electrical current to the heart to stimulate depolarization

Pacemaker cells

Specialized cells of the hearts electrical conduction system capable of spontaneously generating and conducting electrical impulses


An unpleasant awareness of ones heartbeat

Papillary muscles

Muscles attached to the chordae tendineae of the heart valves and the ventricular muscle of the heart

Paroxysmal atrial tachycardia

AT that starts or ends suddenly

Paroxysmal nocturnal dyspnea (PND)

A sudden onset of difficulty breathing that awakens the patient from sleep

Paroxysmal supraventricular tachycardia (PSVT)

A regular, narrow-QRS tachycardia that starts or ends suddenly

Pericardial effusion

An increase in the volume and/or character of pericardial fluid that surrounds the heart


A procedure in which a needle is inserted into the pericardial space and the excess fluid is drawn out (aspired) through the needle


Inflammation of the double walled sac (pericardium) that encloses the heart


Protective sac that surrounds the heart


Ability of a membrane channel to allow passage of electrodes once it is open

Point of maximal impulse (PMI)

Apical impulse; the site where the heartbeat is most strongly felt

Polarized state

Period after repolarization of a myocardial cell (also called the resting state) when the outside of the cell is positive and the interior is negative


Varying in shape

Potential difference

Difference in electrical charge between two points ina circuit; expressed in volts or millivolts


Term used to describe rhythms that originate from above the ventricles but in which the impulse travels by a pathway other than the AV node and bundle of His; thus the supraventricular impulse excites the ventricles earlier than normal


Force exerted by the blood on the walls of the ventricles at the end of diastole

Premature complex

Early beat occurring before the next expected beat; can be atrial, junctional, or ventricular

Primary hypertension

High blood pressure for which no cause is identifiable; also called essential hypertension

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