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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
An extra bundle of working myocardial tissue that forms a connection between the atria and ventricles outside the normal conduction system.
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
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
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 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)
Fixed rate pacemaker that continuously discharges at a preset rate reguardless of the patients intrinsic activity
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.
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)
Base of the heart
Top of the heart; located at approximately the level of the second intercostal space
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.
Force exerted by the blood against the walls of the arteries as the ventricles of the heart contract and relax
Bundle branch block (BBB)
Abnormal conduction of an electrical impulse through either the right or left bundle branches
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
Absence of cariac mechanical activity, confirmed by the absence of a detectable pulse, unresponsiveness, apnea or agonal, gasping respirations.
Period from the beginning of one heart-beat to the beginning of the next; normally consisting of PQRST waves, complexes, and intervals
A condition which heart muscle function is severly impaired, leading to decreased cardiac output and inadequate tissue perfusion
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
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)
Pause for which the normal beat after a premature complex occurs when expected; also called a complete pause
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 heart disease
Disease of the coronary arteries and their resulting complications, such as angina pectoris or acute myocardial infarction
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
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
Any disturbance or abnormality in a normal rhythmic pattern; any cardiac rhythm other than a sinus rhythm.
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
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
High blood pressure for which there is no cause identifiable; also called primary hypertension
Fixed rate pacemaker
Asynchronous pacemaker that continuously discharges at a present rate regardless of the patients heart rate
Large vessels that carry blood to and from the heart: superior and inferior venae cavae, pulmonary veins, aorta, and pulmonary trunk
Third ECG electrode (the first and second are the positve and negative electrodes), which minimizes electrical activity from other sources
A condition in which the heart is unable to pump enough blood to meet the metabolic needs of the body
Portion of the conduction system consisting of the bundle of His, bundles branches, and Purkinje fibers
Situations that require rapid (within 1 hour) lowering of blood pressure to prevent or limit organ damage
Significant elevations in blood pressure with nonspecific symptoms that should be corrected within 24 hrs
ECG changes seen in leads looking directly at the wall of the heart in an infarction
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
A rhythm that begins in the AV junction with a rate of less than 40 beats/min
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
Unit of measure of electrical current needed to elicit depolarization of the myocardium
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.
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
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
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
Specialized cells of the hearts electrical conduction system capable of spontaneously generating and conducting electrical impulses
Muscles attached to the chordae tendineae of the heart valves and the ventricular muscle of the heart
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
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
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
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
Early beat occurring before the next expected beat; can be atrial, junctional, or ventricular
High blood pressure for which no cause is identifiable; also called essential hypertension
Blood from the right ventricle is pumped directly to the lungs for oxygenation through the pulmonary trunk; blood becomes oxygenated and is then delivered throught the pulmonary arteries for the left atrium
Pulseless electrical activity (PEA)
Organized electrical activity observed on a cardiac monitor (other than VT) without the patient having a palpable pulse.
A beat to beat difference in the strength of a pulse (also called mechanical alternans)
A fall in systolic blood pressure of more than 10mmHg during inspiration (also called paradoxal pulse)
Fibers found in both ventricles that conduct an electrical impulse through the heart.
First wave in the cardiac cycle; represents atrial depolarization and the spread of the electrical impulse throughout the right and left atria
Several waveforms (Q wave, R wave, S wave) that represent the spread of an electrical impulse through the ventricles (ventricular depolarization)
Mirror image ECG changes seen in the wall of the heart opposite the location of an infarction
Period of recovery that cells need after being discharged before they are able to respond to a stimulus
Relative refractory period
Corresponds with the downslope of the T wave; cardiac cells can be stimulated to depolarize if the stimulus is strong enough
On an ECG, the first positive deflection in the QRS complex, representing ventricular depolarization
High blood pressure that has an identifiable cause, such as medications or an underlying disease or condition
Semilunar (SL) valves
Valves shaped like half moons that seperate the ventricles from the aorta and pulmonary artery
Inadequate tissue perfusion that results from the failure of the cardiovascular system to deliver sufficient oxygen and nutrients to sustain vital organ function
Amount of blood ejected by either ventricle during one contraction; can be calculated by cardiac output divided by heart rate
Sudden cardiac daeth (SCD)
An unexpected death from a cardiac cause that either occurs immediately or within 1 hour of onset of syptoms
Period during the cardiac cycle when a weaker than normal stimulus can cause cardiac cells to depolarize; extends from the end of phase 3 to the beginning of phase 4 of the cardiac potential
Originating from a site above the bifurcation of the bundle of His, auch as the SA node, atria, or AV junction
Contraction of the heart (usually referring to the ventricular contraction) during which blood is propelled into the pulmonary artery and aorta; when the term is used without reference to a specific chamber of the heart, the term implies ventricular systole
Systolic blood pressure
Pressure exerted against the walls of the large arteries at the peak of ventricular contraction
Interval between two successive PQRST complexes during which electrical activity of the heart is absent; begins with the end of the T wave through the onset of the following P wave and represents the period from end of ventricular repolarization to the onset of atrial depolarization
A pacing lead with a single electrical pole at the distal tip of the pacing lead (negative pole) through which the stimulating pulse is delivered. In a permanent pacemaker with a unipolar lead, the positve pole is the pulse generator case
Amount of blood flowing into the right atrium each minute from the systemic circulation
Type of pre-excitation syndrome charachterized by a slurred upstroke of the QRS complex (delta wave) and wide QRS
Three major coronary arteries
Left anterior descending (LAD)
Right coronary artery (RCA)
Three factors that determine stroke volume
Myocardiums contractile state (contracting or relaxing)
Four properties of cardiac cells
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