Cardiac Arrythmias

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What is automaticity?: The ability to initiate an impulse spontaneously and continuously.
What is contractility?: The ability to respond mechanically to an impulse.
What is conductivity?: The ability to transmit an impulse along a membrane in an orderly manner.
What is excitability?: The ability to be electrically stimulated.
What is arrhythmia?: Abnormal cardiac rhythm.
ECG paper: What do the small (light lined) squares represent horizontally?: 0.04 second
ECG paper: What do the small squares (light lined) represent vertically?: 0.1 mV
ECG paper: What do the large (heavy lined) squares represent horizontally?: 0.20 second
(300 large squares=1.0 minute)
ECG paper: What do the large (heavy lined) squares represent vertically?: 0.5 mV
ECG paper: How many small squares are incorporated into each large (heavy lined) square?: 25
(5 horizontal, 5 vertical)
What is an artifact?: A distortion of the baseline and waveforms seen on the ECG. Can be caused by things like muscle tremors, patients' movements, and loose electrodes.
What is normal sinus rhythm?: Normal conduction pattern of the cardiac cycle, which originates in the SA node.
What does the P wave represent?: The depolarization of the atrium (passage of electrical impulse thru the atrial muscle), causing *atrial* contraction.
What does the QRS complex represent?: The depolarization of the ventricles, causing *ventricular* contraction.
What does the T wave represent?: The REpolarization of the *ventricles*.
What does the PR interval (beginning of P wave to beginning of QRS complex) represent?: Time taken for impulse to spread through the atria, AV node and bundle of His, the bundle branches, and Purkinje fibers, to a point immediately preceding ventricular activation.
normally 0.12-0.20 sec
What does the QRS interval (from beginning to end of QRS complex) represent?: Time taken for depolarization of BOTH VENTRICLES.
normally 0.04-0.12 sec
What does QT interval (from beginning of QRS to end of T wave) represent?: Time taken for entire electrical depolarization AND repolarization of the VENTRICLES.
normally 0.34-0.43 sec
What could be the significance of DISTURBANCE of the PR interval?: Disturbance in conduction usually in AV node, bundle of His, or bundle branches but can be in atria as well.
What could be the significance of DISTURBANCE of the QRS interval?: Disturbance in conduction in bundle branches or in ventricles.
What could be the significance of DISTURBANCE of the QT interval?: Disturbances usually affecting repolarization more than depolarization such as drug effects, electrolyte disturbances, and heart rate changes.
Types of Arrhythmias: Sinus Bradycardia What happens?: The conduction pathway is the same as that in sinus rhythm, but the sinus node discharges at a rate of < 60 beats/min.
Types of Arrhythmias: Sinus Bradycardia What are the clinical associations?: Normal in aerobically trained athletes and in other individuals during sleep. Response to carotid sinus massage, Valsalva maneuver, hypothermia, increased intraocular pressure, increased vagal tone, and admin of parasympathomimetic drugs.
Disease states: hypothyroidism, increased intracranial pressure, obstructive jaundice, and inferior wall MI.
Types of Arrhythmias: Sinus Bradycardia Treatment?: Administration of atropine (anticholinergic) for the patient with hemodynamic symptoms. Pacemaker therapy may be required.
Types of Arrhythmias: Sinus Tachycardia What happens?: Conduction pathway is same as in normal sinus rhythm. Discharge rate from the sinus node is increased as a result of vagal inhibition or sympathetic stimulation.
Rate is > 100 beats/min.
Types of Arrhythmias: Sinus tachycardia. Clinical associations?: Physiologic stressors such as exercise, fever, pain, hypotension, hypovolemia, anxiety, anemia, hypoxia, hypoglycemia, myocardial ischemia, CHF, and hyperthyroidism.
Causative drugs: epinephrine, norepinephrine, caffeine, atropine, theophylline, nifedipine/Procardia, hydralazine/Apresoline.
Types of Arrhythmias: Sinus Tachycardia Treatment?: Determined by underlying causes. B-adrenergic blockers (ie. metoprolol, atenolol) used to reduce HR and decrease myocardial oxygen consumption.
Types of Arrhythmias: Premature Atrial Contraction (PAC) What is it?: A contraction originating from an ectopic focus in the atrium in a location other than the sinus node.
Types of Arrhythmias: Premature Atrial Contraction (PAC) Clinical Associations?: In normal heart it can result from emotional stress or use of caffeine, tobacco, or ETOH. Can also result from disease states such as infection, inflammation, hyperthyroidism, COPD, heart disease (including CAD), valvular disease, and others. Can also be caused by an enlarged atrium.
Types of Arrhythmias: Premature Atrial Contraction (PAC) Significance?: Isolated PAC not significant for healthy heart.
In heart disease, frequent PACs may indicate enhanced automaticity of the atria, or a reentry mechanism and may warn of or initiate supraventricular tachyarrhythmias.
Types of Arrhythmias: Premature Atrial Contraction (PAC) Treatment?: Depends on patients sx. Withdrawal of caffeine or sympathomimetic drugs may be warranted. B-Adrenergic blockers (-olols) may be used to decrease PACs.
Types of Arrhythmias: Paroxysmal Supraventricular Tachycardia (PSVT) What is it?: An arrhythmia originating in an ectopic focus anywhere above the bifurcation of the bundle of His. Occurs with reentrant phenomenon. A run of repeated premature beats is initiated and is ususally heralded by a PAC. "Paroxysmal" refers to an abrupt onset and termination. Termination is sometimes followed by a brief period of asystole. Some degree of AV block may be present.
Types of Arrhythmias: Paroxysmal Supraventricular Tachycardia (PSVT): Clinical associations?: Normal heart: associated with overexertion, emotional stress, changes of position, deep inspiration, and stimulants like caffeine and tobacco.
Disease states: rheumatic heart disease, digitalis toxicity, CAD, cor pulmonale. often occurs in presence of Wolff-Parkinson-White (WPW) syndrome.
Types of Arrhythmias: Paroxysmal Supraventricular Tachycardia (PSVT): ECG characteristics?: HR is 100-300 beats per minute
P wave often hidden in preceding T wave and has abnormal contour.
PR interval may be proloned, shortened. or normal, and QRS complex may have normal or abnormal contour.
Types of Arrhythmias: Paroxysmal Supraventricular Tachycardia (PSVT): Significance?: Depends on symptoms and HR.
A prononged episode and HR greater than 180 bpm may precipitate a decreased CO with hypotension and myocardial ischemia.
Types of Arrhythmias: Paroxysmal Supraventricular Tachycardia (PSVT): Treatment?: Vagal stimulation and drug therapy.
Vagal stimulation induced by carotid massage or Valsalva maneuver.
Adenosine IV most commonly used to convert PVST to normal sinus.
Also used--IV diltiazem/Cardizem or one of the following B-adrenergic blockers: entenolo/Tenormin, metoprolol/Toprol XL, or esmolol/Brevibloc.
Digitalis and amiodarone/Cordarone can also be used.
note: DIGITALIS AND CALCIUM CHANNEL BLOCKERS CAN CAUSE HEMODYNAMIC COLLAPSE IN WPW SYNDROME.
What does this ECG show?: atrial fibrillation
What does this ECG show?: atrial flutter
What does this ECG show?: atrial flutter, 2:1 block
What does this ECG show?: atrial flutter, variable block
What does this ECG show?: 1st degree heart block
What does this ECG show?: normal sinus rhythm
What does this ECG show?: paroxysmal supraventricular tachycardia (PSVT)
What does this ECG show?: premature atrial contraction (PAC)
What does this ECG show?: r on t phenomena
What does this ECG show?: 2nd degree heart block
What does this ECG show?: sinus arrhythmia
What does this ECG show?: sinus bradycardia
What does this ECG show?: sinus tachycardia
What does this ECG show?: 3rd degree heart block
What does this ECG show?: ventricular fibrillation

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