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103 Cards in this Set
- Front
- Back
resting state |
myocytes polarized, interior of cell NEGATIVEly charged |
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depolarization |
myocytes become positive and contract |
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repolarization |
myocyte interiors regain resting negative charge |
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automaticity |
ability of the SA node to generate pacemaking stimuli |
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AV node |
sole pathway to conduct depolarization stiumuls through the fibrous AV valves |
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tRicuspid |
Right |
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mitraL |
left |
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P wave |
represents atrial contraction |
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conduction through AV node and bundle of His |
depolarization conducts slowly through the AV node due to slow-moving Ca++ ions, then rapidly through the His bundle and L & R bundle branches due to fast-moving Na+ ions |
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Q wave |
beginning of QRS, first downward reflection of the complex |
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R wave |
first upward wave in the QRS complex |
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S wave |
any downward wave that is PRECEDED by an upward wave |
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QRS complex |
represents ventricular depolarization and contraction |
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T wave |
represents ventricular repolarization |
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ST segment |
horizontal segment following QRS, preceding T wave. Elevation or depression indicates pathology. |
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QT interval |
represents duration of ventricular systole, from beginning of QRS to end of T wave |
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release of free Ca++ cells |
produces contraction |
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controlled outflow of K+ ions |
repolarization |
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Na+ ions |
produce cell-to-cell conduction of depolarization |
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EKG graph paper |
small boxes 1 mm, large 5 mm |
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height & depth of waves measures |
voltage |
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amplitude of wave |
magnitude (in mm) of upward or downward deflection |
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positive deflections |
upward |
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negative deflections |
downward |
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time between two heavy black lines |
0.2 seconds |
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time between two light black lines |
0.04 seconds |
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4 small squares |
0.16 seconds |
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lead I |
horizontal - left arm +, right arm - |
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lead III |
diagonal -- left arm -, left leg + |
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lead II |
diagonal -- right arm -, left leg + |
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AVF lead |
left foot +, both arms - |
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AVR |
right arm +, left leg/left arm - |
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AVL |
left arm +, left leg, right arm - |
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lateral leads |
I & AVL, both have positive electrode laterally on the left arm |
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inferior leads |
II, III, & AVF -- all have positive electrode positioned on L foot |
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chest leads |
V1-V6, always positive |
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right chest leads |
V1, V2 |
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left chest leads |
V5, V6 |
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limb leads plane |
frontal |
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chest leads plane |
horizontal |
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sympathetic |
secretes norepinephrine; activates adrenergic receptors |
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parasympathetic |
secretes acetylcholine; activates cholinergic receptors
|
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norepinephrine |
activate adrenergic receptors, cause SA node to pace faster. Improves AV node conduction and accelerates conduction through atrial and ventricular myocardium, increases contraction |
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actetylcholine |
inhibits SA nodes, decreasing heart rate, decreases myocardial conduction and depresses AV node, diminishes contraction. |
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vagus nerve |
body's main sympathetic pathway |
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sympathetic stimulation of arteries |
causes constriction with alpha adrenergic receptors |
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parasympathetic stimulation of arteries |
causes dilation with cholinergic receptors |
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merciful syncope |
parasympathetic response slow SA node, dilates arteries, causes loss of consciousness |
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vagal maneuvers |
stimulate parasympathetic reflex that inhibits SA node and AV node; carotid massage, induced gagging, bear down |
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response to standing |
sympathetic response constricts peripheral arteries and prevents syncope |
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orthostatic hypotension |
abrupt fall in BP caused by failure of compensatory sympathetic mechanisms |
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neuro-cardiogenic syncope |
parasympathetic response to prolonged standing, causes vasodilation and slowing of pulse - syncope |
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SA node |
heart pacemaker |
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SA node location |
upper posterior wall of R atrium |
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normal sinus rhythm |
60-100 bpm |
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sinus bradycardia |
less than 60 BPM |
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sinus tachycardia |
sinus rhythm with rate > 100 BPM |
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automaticity foci |
potential pacemakers which assumes pacemaking when SA node fails. Atrial, AV junction, ventricular |
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atrial rates |
60-80 BPM |
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AV junction rates |
40-60 BPM |
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ventricular rates |
20-40 BPM |
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dominant pacemaker |
fastest functioning pacemaker will overdrive-suppress all slower pacemakers |
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rate count numbers |
300, 150, 100, 75, 60, 50 |
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5 pieces to evaluate EKG |
rate, rhythm, axis, hypertrophy, infarction |
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regular rhythm |
constant, unvarying rate |
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bachmann's bundle |
originates in the SA node and distributes depolarization to the left bundle |
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conduction pathways from the SA to the AV node |
Anterior, Middle and Posterior internodal tracts |
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wandering pacemaker |
* P' wave shape varies; * atrial rate less than 100; * irregular ventricular rhythm. |
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multifocal atrial tachycardia |
* P' wave shape varies;
* atrial rate exceeds 100; * irregular ventricular rhythm. |
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atrial fibrillation |
*irregular rhythm; *continuous chaotic atrial spikes; *irregular ventricular rhythm; |
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escape rhythms/beats |
* atrial escape rhythm/beat; * junctional escape rhythm/beat; * ventricular escape rhythm/beat; |
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atrial escape beat/rhythm |
sinus node arrest leads to single beat, or sustained atrial rhythm at 60-80 BPM |
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junctional escape beat/rhythm |
sinus node arrest then atrial foci fail leads to junctional escape rhythm |
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retrograde atrial depolarization |
pacing stimulus from the AV node also depolarizes atria from below, causes inverted P' wave |
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ventricular escape rhythm |
Mechanism 1: AV block prevents stimulation by SA/atrial pacing. Mechanism 2: total failure of SA node and all automaticity foci above the ventricles leads to full ventricular pacing |
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atrial and junctional irritants (cause premature beats) |
* adrenaline; * increased sympathetic stimulation; * caffeine, amphetamines, cocaine, other bta-1 receptor stimulants; * excess digitalis, some toxins, ETOH; * hyperthyroidism; * stretch; |
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premature atrial beat |
resets SA node pacing |
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premature atrial beat with aberrant ventricular conduction |
caused when one bundle branch has not repolarized completely, an causes slight delay in depolarization and widened QRS |
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non-conducted premature atrial beat |
caused when AV node is not fully repolarized and still refractory to stimulus. P wave with no QRS-T response -- appearance of block. |
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atrial bigeminy |
PAB at the end of every normal cycle |
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atrial trigeminy |
PAB after two normal cycles |
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widened QRS |
consider aberrant junctional or atrial beat |
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ventricular focus irritability causes |
* low O2; * Low K+; * pathology -- mitral valve prolapse, stretch, myocarditis. |
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most common cause of PVCs |
hypoxia |
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parasystole |
PVCs coupled to a long series of normal cycles |
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mitral valve prolapse/Barlow syndrome |
* 6-17% of females, 1.5% males; * causes multi-focal PVCs; * |
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R on T phenomenon |
PVC falls on a T wave -- vulnerable period, likely to start a run of Vtach |
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paroxysmal tachycardia |
150-250 BPM |
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flutter tachyarrhythmia |
250-350 BPM |
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fibrillation tachyarrhythmia |
350-450 BPM |
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digitalis |
provokes atrial focus, and inhibits AV node -- possible block. |
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reentry tachycardia |
continuous circuit around the AV node that rapidly paces the atria and ventricles |
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supraventricular paroxysmal tachycardia |
paroxysmal atrial tachycardia and paroxysmal junctional tachycardia |
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ventricular tachycardia = |
run of PVCs |
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ventricular tachycardia indicates |
coronary insufficiency, poor oxygenation of the heart |
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wide QRS complex SVT |
patient with coronary disease/infarction -- uncommon; QRS width < 0.14 sec; rare AV dissociation showing captures or fusions; raare extreme Right Axis Deviations |
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Ventricular tachycardia |
very common in pt with coronary disease or infarction; QRS >0.14 sec; AV dissociations shows captures or fusions; Extreme Right Axis Deviation |
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torsades de pointes |
two competitive irritable foci |
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atrial flutter |
consecutive, identical flutter waves in rapid back-to-back succession. Sawtooth appearance. |
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ventricular flutter |
smooth sine-wave pattern; arrhythmia rapidly deteriorates |
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fibrillation |
rapid discharges from multiple foci |
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bundle of Kent |
accessory pathway that causes ventricular pre-excitation in Wolff-Parkinson-White syndrome |
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Lown-Ganong-Levine Syndrome |
AV node is bypassed by an extension of the anterior internodal tract. Without the conduction delay of the AV node. Rapid atrial rates are conducted directly to the Bundle of His. |