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**Normal Sinus Rhythm:** iği ; İİİİ İİaİİııİİ Şİİİı;wİiaızıaİİİ \...Eşi E: Rate 60 -- 100 per minute ----------------------------------- ------------------------------------------------------------------- Rhythm Regular P Wave...

**Normal Sinus Rhythm:** iği ; İİİİ İİaİİııİİ Şİİİı;wİiaızıaİİİ \...Eşi E: Rate 60 -- 100 per minute ----------------------------------- ------------------------------------------------------------------- Rhythm Regular P Wave Positive, smoothly rounded, under 0.1 seconds (two small squares) PR Interval Between 0.12 -- 0.20 seconds (max one large box) QRS & Conduction Ratio Narrow and sharply pointed, 1:1 ratio with P wave Origin SA node PP & RR Intervals Equal Aetiology & Clinical Significance **[Sinus Dysrhythmias: ]** **Sinus Arrhythmia (Dysrhythmia):**  Irregular rate in which the R-R interval is greater than 0.12 seconds. +-----------------------------------+-----------------------------------+ | Rate | Generally still 60-100 | +===================================+===================================+ | Rhythm | Can be irregularly irregular or | | | regularly irregular | +-----------------------------------+-----------------------------------+ | P Wave | Relatively normal | +-----------------------------------+-----------------------------------+ | PR Interval | | +-----------------------------------+-----------------------------------+ | QRS & Conduction Ratio | Normal QRS, 1:1 | +-----------------------------------+-----------------------------------+ | Origin | SA node | +-----------------------------------+-----------------------------------+ | PP & RR Intervals | Larger RR intervals | +-----------------------------------+-----------------------------------+ | Aetiology & Clinical Significance | Sick sinus syndrome, sinus node | | | dysfunction, sinus node damage, | | | medications, advanced age | +-----------------------------------+-----------------------------------+ | Clinical Significance | Relates to respiratory rates | | | | | | - Inhalation = increase is | | | heart rate | | | | | | - Exhalation = decrease in | | | heart rate | +-----------------------------------+-----------------------------------+ **Sinus Bradycardia:** i%Ea\'ăiiiiiii.\'EEfi : - Eiiižiiii\#i fiii iiiiiiiiiiini isiii iiiiiiiiiiii aiiiiii„ Dysrhythmia in the SA node where it is not firing as quickly as normal. +-----------------------------------+-----------------------------------+ | Rate | Mild = 50 -59, Moderate = 30 -- | | | 50, Severe = under 30 | +===================================+===================================+ | Rhythm | Regular | +-----------------------------------+-----------------------------------+ | P Wave | Upright and rounded | +-----------------------------------+-----------------------------------+ | PR Interval | Normal duration | +-----------------------------------+-----------------------------------+ | QRS & Conduction Ratio | Narrow and pointed, 1:1 | +-----------------------------------+-----------------------------------+ | Origin | SA node | +-----------------------------------+-----------------------------------+ | PP & RR Intervals | | +-----------------------------------+-----------------------------------+ | Aetiology & Clinical Significance | Mild = no clinical significance, | | | depends on the patient | | | (pre-existing = issue) | | | | | | Moderate = hypotension, | | | symptomatic = less cardiac output | | | = less blood pumping around = | | | feelings of dizziness or faint | | | | | | Severe = hypotensive = patient | | | will be critically ill | +-----------------------------------+-----------------------------------+ **Sinus Arrest:**  Periodic failure of the SA node resulting in irregular bradycardia -- SA node stopped firing. Rate Generally 40 -- 100 but can be slower ------------------------ ---------------------------------------------------------------------------------------------------------------------------------------- Rhythm Irregularly irregular P Wave PR Interval Underlying rhythm QRS & Conduction Ratio Normal duration Origin PP & RR Intervals PP intervals will be irregular Aetiology Causative factors = increased vagal tone, hypoxia, hyperkalaemia, acute myocardial infarction, medications, sleep apnoea (obstructive) Clinical Significance No beat from the SA node = rescue beat from AV node = QRS complex with no P wave = slower impulse = less cardiac output **Sinoatrial Exit Block:** Interruption in the conduction of the electrical impulse from the SA node to the atria. Rate Generally 60 -- 100 but can be slower -- variable due to arrest blocks ------------------------ ------------------------------------------------------------------------------------------------------------------------- Rhythm Missed beats = irregular P Wave Normal PR Interval That of the underlying rhythm QRS & Conduction Ratio Sharp and narrow, 1:1 Origin SA node PP & RR Intervals PP interval will be regular with a skipped P wave Aetiology Increased vagal tone, hypoxia, hyperkalaemia, acute myocardial infarction, medications, sleep apnoea (obstructive) Clinical Significance No beat from the SA node = rescue beat from AV node = QRS complex with no P wave = slower impulse = less cardiac output **Sinus Tachycardia:**  Fast heart rate originating in the SA node. Rate Above 100 ------------------------ ---------------------------------------------------------------------------------------------------------------------------------------------- Rhythm Regular P Wave Normal, however, can disappear in the T waves PR Interval Shorter due to increased HR QRS & Conduction Ratio Narrow and sharp, 1:1 Origin SA node PP & RR Intervals Aetiology Medications, caffeine, illicit drugs, sympathetic nervous system, pulmonary embolisms, hypoxia, myocardial infarction Clinical Significance Increased heart rate = increased myocardial demand = too much stress on the heart (e.g. pre-existing problems) = can decrease cardiac output **[Atrial Dysrhythmias:]** **Premature Atrial Complex (PAC):** iiiiii iiiüi üiiii işli\'İÜwİİİiEiliiiiiiiii İİiİİİiİİİİİİİilİİİİİİİİİİİiİ iiiiİİİİİiİİİİİİİİİiİİiiiiii Premature impulse arising from an ectopic focus in the atria causing an early PQRST complex, then followed by a non-compensatory pause. Rate Underlying rhythm ------------------------ ----------------------------------------------------------------------------------------------------------------------------------- Rhythm Irregular at point of PAC P Wave Abnormal = abnormal atrial depolarisation, can also be inverted (different pacemaker) PR Interval Should be normal, if inverted = shorter QRS & Conduction Ratio Narrow and sharp, 1:1 Origin Multiple sites in atria or AV junction (inverted) PP & RR Intervals Will both be early Aetiology Increased sympathetic tone, infections, caffeine, smoking, cardiovascular disease, hypoxia, valve problems & hypertrophy of atria Clinical Significance Dependant on underlying cause, disease or pathological processes of atria = significant for patient long term **Wandering Atrial Pacemaker:**  Impulses occurring from various points within the atria. Rate 60 -- 100 but can be variable ------------------------ -------------------------------------------------------------- Rhythm Slightly irregular P Wave Vary in size and shape due to different pacemakers PR Interval Normal (from SA node) or short (pacemaker closer to AV node) QRS & Conduction Ratio Sharp and narrow, 1:2 Origin Variable -- SA node, ectopic atrial sites, AV junction PP & RR Intervals Unequal Aetiology Age (young people and athletes), medications Clinical Significance Not typically significance in the immediate term **Atrial Tachycardia:** Rhythm from a single ectopic focus that is throwing depolarisation out. +-----------------------------------+-----------------------------------+ | Rate | 160 -- 240 | +===================================+===================================+ | Rhythm | Typically regular | +-----------------------------------+-----------------------------------+ | P Wave | Abnormal as SA node isn't firing | | | too fast = vary in shape, size, | | | angle | +-----------------------------------+-----------------------------------+ | PR Interval | Fairly regular and normal | | | intervals | +-----------------------------------+-----------------------------------+ | QRS & Conduction Ratio | Narrow and sharp, can be dropped | | | = 2:1 ratio | +-----------------------------------+-----------------------------------+ | Origin | Ectopic site in the atria | +-----------------------------------+-----------------------------------+ | PP & RR Intervals | Should be regular | +-----------------------------------+-----------------------------------+ | Aetiology | Electrolyte imbalances, hypoxia, | | | chronic lung disease, coronary | | | heart disease, acute coronary | | | syndrome, rheumatic heart | | | disease, alcohol toxicity | +-----------------------------------+-----------------------------------+ | Clinical Significance | Dependant on the underlying cause | | | = pre-existing conditions = | | | significant | | | | | | Fast impulses transferred to the | | | ventricles = increased cardio | | | workload = increased O2 demand of | | | the heart = deterioration | +-----------------------------------+-----------------------------------+ **Multifocal Atrial Tachycardia (MAT):**  More than three foci depolarising, throwing out depolarisation. +-----------------------------------+-----------------------------------+ | Rate | 100 -- 150 | +===================================+===================================+ | Rhythm | Typically regular | +-----------------------------------+-----------------------------------+ | P Wave | Abnormal and variable | +-----------------------------------+-----------------------------------+ | PR Interval | Variable depending on the | | | proximity of the ectopic focus to | | | AV node | +-----------------------------------+-----------------------------------+ | QRS & Conduction Ratio | Narrow and sharply pointed, 2:1 | | | ration is possible | +-----------------------------------+-----------------------------------+ | Origin | Multiple foci in the atria | +-----------------------------------+-----------------------------------+ | PP & RR Intervals | Can vary | +-----------------------------------+-----------------------------------+ | Aetiology | Electrolyte imbalances, hypoxia, | | | chronic lung disease, coronary | | | heart disease, acute coronary | | | syndrome, rheumatic heart | | | disease, alcohol toxicity | +-----------------------------------+-----------------------------------+ | Clinical Significance | Dependant on the underlying cause | | | = pre-existing conditions = | | | significant | | | | | | Fast impulses transferred to the | | | ventricles = increased cardio | | | workload = increased O2 demand of | | | the heart = deterioration | +-----------------------------------+-----------------------------------+ **Atrial Flutter:** A graph with a graph on it Description automatically generated Rhythm arising in an atrial ectopic pacemaker due to increased automaticity or a rapid re-entry circuit creating a sawtooth appearance (fib-flutter). +-----------------------------------+-----------------------------------+ | Rate | 240 -- 360 (atrial rate) which is | | | 2x ventricular rate | +===================================+===================================+ | Rhythm | Typically regular but may not be | | | due to changes in ratio | +-----------------------------------+-----------------------------------+ | P Wave | 'F' waves are present instead of | | | P waves | +-----------------------------------+-----------------------------------+ | PR Interval | FR interval = difficult to | | | measure | +-----------------------------------+-----------------------------------+ | QRS & Conduction Ratio | QRS should be regular, ratio is | | | usually 2:1, 3:1, 4:1 and can | | | change | +-----------------------------------+-----------------------------------+ | Origin | Atrial site outside of SA node | +-----------------------------------+-----------------------------------+ | PP & RR Intervals | PP doesn't exist, RR are equal | | | until ratio changes | +-----------------------------------+-----------------------------------+ | Aetiology | Paroxysmal (transiently) = atrial | | | dilation, hyperthyroidism, | | | hypoxia, congestive heart | | | failure, myocarditis, alcoholism, | | | pericarditis | | | | | | Chronic = stenotic valves, | | | coronary artery disease, | | | hypertension | +-----------------------------------+-----------------------------------+ | Clinical Significance | High ventricular rate = higher | | | myocardial demand = precipitate | | | or exacerbate pre-existing | | | conditions or cause new | | | conditions e.g. heart attack | +-----------------------------------+-----------------------------------+ **Atrial Fibrillation:**  Increased automaticity or re-entry in the atria causing multiple ectopic atria sites to produce f waves in an irregular ventricular response. Rate 350 -- 600, ventricular rate can be under 60 ------------------------ -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Rhythm Irregularly irregular P Wave 'f' wave PR Interval fR interval is basically absent QRS & Conduction Ratio QRS should be normal but random ratios Origin Atrial sites outside the SA node PP & RR Intervals PP = absent, RR = unequal Aetiology Mitral valve disease, coronary heart/artery disease, hypertension, congestive cardiac failure, lung disease, excessive alcohol & caffeine use, medications Clinical Significance Chaos occurring = no blood moving effectively = can create blood clots = breaks off and becomes an embolism = unable to fit through all arteries = occlusion in cerebral arteries = stroke **[Junctional Rhythms: ]** **Premature Junctional Complex (PJC):** Premature impulse originating within the AV junction, causing a compensatory pause. +-----------------------------------+-----------------------------------+ | Rate | That of the underlying rhythm = | | | 70 | +===================================+===================================+ | Rhythm | Irregular where the PJC is | +-----------------------------------+-----------------------------------+ | P Wave | Can be before or after QRS, or | | | also buried in the QRS | +-----------------------------------+-----------------------------------+ | PR Interval | Less than 0.12 seconds | +-----------------------------------+-----------------------------------+ | QRS & Conduction Ratio | Sharp and narrow, 1:1 | +-----------------------------------+-----------------------------------+ | Origin | Ectopic pacemaker in the AV | | | junction | +-----------------------------------+-----------------------------------+ | PP & RR Intervals | PP & RR with PJC = 2x that of | | | underlying rhythm, otherwise | | | normal | +-----------------------------------+-----------------------------------+ | Aetiology | Antiarrhythmics, adrenaline, | | | hypoxia, junction toxicity, | | | congestive heart failure, | | | coronary artery disease | +-----------------------------------+-----------------------------------+ | Clinical Significance | In isolation = not significant | | | | | | Not in isolation = can cause | | | other dysthymias & impact cardiac | | | output | +-----------------------------------+-----------------------------------+ **Junctional Escape Rhythm:**  Problem with sinus pacing or block where the AV junction takes over and creates its own impulses. Rate 40 -- 60 but can be less ------------------------ ----------------------------------------------------------------------------------------------------------------------------------------- Rhythm Regular P Wave Can be before or after QRS or not present PR Interval Under 0.12 seconds QRS & Conduction Ratio Narrow and sharp, no ratio as P waves is not associated with QRS complexes Origin Ectopic pacemaker in the AV junction PP & RR Intervals RR intervals are equal Aetiology Severe sinus bradycardia, sinus arrest, sinoatrial exit block, AV block, hyperkalaemia, medications and is present in ROSC Clinical Significance Slower than SA node = slow heart rate and cardiac output = poor cerebral perfusion, poor coronary perfusion and low end organ perfusion **Nonparoxysmal Junctional Tachycardia (Accelerated Junctional Rhythm/Junctional Tachycardia):** Rate of the AV junction has exceeded that of the SA node. +-----------------------------------+-----------------------------------+ | Rate | Accelerated = 60 -- 100, | | | junctional tachycardia = over 100 | +===================================+===================================+ | Rhythm | Regular, just fast | +-----------------------------------+-----------------------------------+ | P Wave | Before or after QRS or absent | +-----------------------------------+-----------------------------------+ | PR Interval | Less than 0.12 seconds | +-----------------------------------+-----------------------------------+ | QRS & Conduction Ratio | Sharp and narrow, 1:1 | +-----------------------------------+-----------------------------------+ | Origin | Ectopic pacemaker within the AV | | | junction | +-----------------------------------+-----------------------------------+ | PP & RR Intervals | RR intervals = equal | +-----------------------------------+-----------------------------------+ | Aetiology | Medications, damage to AV | | | junction (blockage of arteries, | | | heart attack), hyperkalaemia, | | | hypoxia | +-----------------------------------+-----------------------------------+ | Clinical Significance | Post heart attack = significant | | | | | | Hypoxic or overdose = significant | +-----------------------------------+-----------------------------------+ **Paroxysmal Supraventricular Tachycardia (PVST):**  Rhythm originating abruptly at the site of a re-entry circuit in the AV junction. Rate 150 -- 250 with abrupt onset or termination ------------------------ ------------------------------------------------------------------------------------------------------------- Rhythm Irregular at start and end of rhythm, otherwise regular P Wave Typically absent (buried in QRS) PR Interval Under 0.12 seconds QRS & Conduction Ratio Narrow QRS complexes, 1:1 if P wave can be seen Origin AV node or accessory pathway outside AV node causing re-entry circuit PP & RR Intervals RR intervals are equal Aetiology Associated with ectopic focus, increased sympathetic nervous tone, electrolyte imbalances, hyperventilation Clinical Significance Treated with valsalva manoeuvre **Atrioventricular Block -- First Degree:** Constant conduction delay from the AV node. +-----------------------------------+-----------------------------------+ | Rate | That of the underlying rhythm | +===================================+===================================+ | Rhythm | Regular | +-----------------------------------+-----------------------------------+ | P Wave | Consistently normal | +-----------------------------------+-----------------------------------+ | PR Interval | Longer than 0.20 seconds | +-----------------------------------+-----------------------------------+ | QRS & Conduction Ratio | Generally a little wider due to | | | conduction delay, 1:1 | +-----------------------------------+-----------------------------------+ | Origin | Sinus node | +-----------------------------------+-----------------------------------+ | PP & RR Intervals | Equal | +-----------------------------------+-----------------------------------+ | Aetiology | Damage to AV node, ischemic heart | | | disease, excessive vagal tone, | | | medications, acute rheumatic | | | fever, electrolyte imbalances | +-----------------------------------+-----------------------------------+ | Clinical Significance | In isolation = patients will be | | | asymptomatic = consider cause | | | | | | Can progress to a high-grade | | | block | +-----------------------------------+-----------------------------------+ **Atrioventricular Block -- Second Degree Type 1 (Mobitz 1/Wenckebach):**  The delay in conduction progressively gets longer from the AV node until it is completely blocked. Rate That of the underlying rhythm ------------------------ ----------------------------------------------------------------------------------------------------------------------------- Rhythm Regularly irregular P Wave Normal PR Interval Gets progressively longer until QRS is dropped QRS & Conduction Ratio Sharp and narrow, variable ratios - dependant on frequency of non-conductive P wave Origin SA node PP & RR Intervals PP = equal, RR = unequal and progressively shorter Aetiology Damage to AV node, ischemic heart disease, excessive vagal tone, medications, acute rheumatic fever, electrolyte imbalances Clinical Significance Transient and variable, can progress to higher-grade block **Atrioventricular Block -- Second Degree Type 2 (Mobitz 2/Infranodal):**. ŞİŞİ Şİİ; İİİİİİİİ: Rhythm with intermittent dropped beats due to completed blocks below AV node. Rate Variable -- depending on frequency of blocks ------------------------ ----------------------------------------------------------------------------------------------------------------------------- Rhythm Irregularly irregular P Wave Normal PR Interval Should be normal, until QRS complex is dropped QRS & Conduction Ratio Can be wide, ratio is generally 4:3 = one more P wave than QRS complex Origin SA node PP & RR Intervals PP = equal, RR = unequal Aetiology Damage involving the anterior walls of the heart can cause damage to bundle branches. Clinical Significance Slow ventricular rate = slow heart rate and cardiac output = low cerebral and coronary perfusion, low grade organ perfusion **Atrioventricular Block -- Third Degree -- Complete AV Block:**  Complete block of descending electrical activity from either the AV node, Bundle of His or bundle branches. +-----------------------------------+-----------------------------------+ | Rate | Underlying rhythm = dependant on | | | what pacemaker is working (40 -- | | | 60) | +===================================+===================================+ | Rhythm | Regular | +-----------------------------------+-----------------------------------+ | P Wave | Should be normal if SA node is | | | firing regularly, can see | | | flutter/fibrillation | +-----------------------------------+-----------------------------------+ | PR Interval | Variable -- no association | +-----------------------------------+-----------------------------------+ | QRS & Conduction Ratio | QRS & P wave = no association = | | | no ratio, narrow and sharp = SA | | | node, wide = ventricular | | | pacemakers | +-----------------------------------+-----------------------------------+ | Origin | AV node or idioventricular | +-----------------------------------+-----------------------------------+ | PP & RR Intervals | PP = equal, RR = equal | +-----------------------------------+-----------------------------------+ | Aetiology | Transient = similar to 1^st^ | | | degree block | | | | | | Permanent = severe damage to | | | specific AV junction region from | | | coronary occlusion e.g. | | | myocardial infarction, chronic | | | degenerative changes of bundle | | | branches. | +-----------------------------------+-----------------------------------+ | Clinical Significance | No escape beat = asystole = | | | light-headedness = loss of | | | consciousness = patient can die | +-----------------------------------+-----------------------------------+ **[Ventricular Dysrhythmias: ]** **Premature Ventricular Complex (PVC):** Ectopic premature impulse coming from the ventricles, can be multifocal (multiple areas of impulse generation) or unifocal (one area of impulse generation). Rate That of the underlying rhythm (ectopic intervals not counted) ------------------------ ---------------------------------------------------------------------------------------------------------------------------------------------- Rhythm Irregular where the PVC occurs P Wave That of the underlying rhythm PR Interval That of the underlying rhythm QRS & Conduction Ratio Wide Origin Ectopic site in ventricles, bundle branches, Purkinje, or myocardium PP & RR Intervals Unequal, compensatory pause Aetiology May not be associated with disease, increased sympathetic tone, stimulants, myocardial ischemia/infarction, hypoxia, acidosis, hyperkalaemia Clinical Significance In isolation = not immediately significant, no in isolation = significant, not all PVC's can eject blood, R on T phenomenon **Ventricular Tachycardia:**  Very fast rhythm that originates in an ectopic pacemaker in the ventricles. +-----------------------------------+-----------------------------------+ | Rate | 100 -- 150 | +===================================+===================================+ | Rhythm | Regular with slight variations | +-----------------------------------+-----------------------------------+ | P Wave | Absent | +-----------------------------------+-----------------------------------+ | PR Interval | Absent | +-----------------------------------+-----------------------------------+ | QRS & Conduction Ratio | Wide complexes, no ratio = AV | | | disassociation | +-----------------------------------+-----------------------------------+ | Origin | Ectopic site in ventricles, | | | bundle branches, Purkinje, or | | | myocardium | +-----------------------------------+-----------------------------------+ | PP & RR Intervals | PP = none = ectopic pacemaker is | | | below AV node, RR = equal | +-----------------------------------+-----------------------------------+ | Aetiology | Cardiomyopathy, acute coronary | | | syndromes, valve disease, | | | abnormalities in atria or | | | ventricles, electrolyte | | | imbalances, hyperkalaemia, R on T | +-----------------------------------+-----------------------------------+ | Clinical Significance | High workload = decreased cardiac | | | output + increased oxygen demand | | | = unable to supply enough blood | | | for coronary perfusion | | | | | | Perfusing can deteriorate to | | | non-perfusing, cannot be | | | sustained for long time | +-----------------------------------+-----------------------------------+ **Ventricular Fibrillation:** A rhythm that originates within multiple ectopic sites within the ventricles. Rate 300 -- 500 but uncoordinated ------------------------ --------------------------------------------------------------------------------------------------------------------------------------------------------- Rhythm Irregularly irregular P Wave Absent PR Interval Absent QRS & Conduction Ratio Absent Origin Multiple ectopic sites within the ventricles PP & RR Intervals Absent Aetiology Cardiomyopathy, cardiac trauma, hypoxia, acidosis, electrolyte imbalances, hyper/hypokalaemia, medications, electrocution, failed cardioversion, R on T Clinical Significance No cardiac output = must be shocked **Ventricular Escape Rhythm/Idioventricular Rhythm (IVR) & Accelerated Idioventricular Rhythm (AIVR):**  Ectopic pacemaker in the ventricles that have taken over sending impulses. +-----------------------------------+-----------------------------------+ | Rate | 20 -- 40, over 40 = AIVR | +===================================+===================================+ | Rhythm | Regular | +-----------------------------------+-----------------------------------+ | P Wave | Absent | +-----------------------------------+-----------------------------------+ | PR Interval | Absent | +-----------------------------------+-----------------------------------+ | QRS & Conduction Ratio | Will be wide and bizarre | +-----------------------------------+-----------------------------------+ | Origin | Ectopic pacemaker in ventricles | +-----------------------------------+-----------------------------------+ | PP & RR Intervals | RR = equal | +-----------------------------------+-----------------------------------+ | Aetiology | Sinus arrest, sinoatrial exit | | | block, 3^rd^ degree AV block, | | | block below AV node | +-----------------------------------+-----------------------------------+ | Clinical Significance | AIVR = can been seen in ROSC | | | | | | Poor cardiac output alongside | | | whatever caused this to occur = | | | significant hemodynamic | | | instability | +-----------------------------------+-----------------------------------+ **Asystole:** Absence of all ventricular electrical activity. +-----------------------------------+-----------------------------------+ | Rate | None | +===================================+===================================+ | Rhythm | None | +-----------------------------------+-----------------------------------+ | P Wave | Mostly absent | +-----------------------------------+-----------------------------------+ | PR Interval | None | +-----------------------------------+-----------------------------------+ | QRS & Conduction Ratio | None | +-----------------------------------+-----------------------------------+ | Origin | None | +-----------------------------------+-----------------------------------+ | PP & RR Intervals | None | +-----------------------------------+-----------------------------------+ | Aetiology | Failure of all primary | | | pacemakers, VT/VF refractory to | | | defibrillation | | | | | | Transient = termination of ST or | | | VT, after administration of | | | medications | +-----------------------------------+-----------------------------------+ | Clinical Significance | Loss of all ventricular activity | | | = no cardiac out = no perfusion | +-----------------------------------+-----------------------------------+ **Internal Pacing:**  Stimulation of the heart to contract via a pacemaker. Rate 60 -- 70 ------------------------ -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Rhythm Regular, demand pacing = can be irregular P Wave Normal, atrial pacing = narrow spike preceding P wave PR Interval Normal QRS & Conduction Ratio Ventricular pacing = can be wide Origin Pacemaker PP & RR Intervals Aetiology Complete heart blocks Pathophysiology Demand pacing = heart cannot fire faster than pre-set rate, fixed pacing = discharge at fixed, constant rate, failure to capture = spikes without anything after, dual chamber pacing = two lines before QRS