CARDIOLOGY - Sinus and Atrial Dysrhythmias (Week 5) Flashcards

Question

**Sinus Block** Rate Rhythm P wave PR Interval QRS complex

Answer 1

**Rate:** can occur at any rate (usually 60 - 100 BPM) **Rhythm:** _occasionally irregular_ (due to pause(s) caused by sinus block); pause is the same distance between two other P-P intervals **P wave:** normal sinus P's before AND after the pause **PR Interval:** 0.12-0.20 seconds, constant from beat to beat **QRS complex:** \<0.12 seconds (can be \> 0.12 if BBB exist)

Answer 2

**Causes:** * **MI** * **Vagal stimulation** * **CAD** (building up atherosclerotic plaque) * **Myocarditis** * **CHF** * **Hypoxia** * **Medications** - eg. Digitalis, Quinidine, Procainamide **Adverse Effects:** frequent or very long sinus blocks can cause decreased cardiac output **Treatment:** attempt to correct the underlying cause

Answer 3

SA node stops firing impulses regularly (aka SA node is not working) and ultimately the heart begins beating after one more missed beats

Answer 4

* SA node suddenly stops firing for a brief period - result is one or more beat sequences missing, creating a "pause" * EITHER * 1) sinus node eventually resumes functioning after missing one or two beats OR * 2) other pacemaker may continue as the new pacemaker and possibly create a new rhythm

Answer 5

SA node does NOT generate an impulse so no impulse heads down the normal conduction pathway

Answer 6

**Sinus Block:** R-R intervals are exactly equal distance apart EXCEPT for the 6th complex **Sinus Arrest:** R-R intervals are exactly equal distance apart EXCEPT for anything after 5th complex * An ectopic beat follows which confirms another pacemaker (purkinje fibers) assumed responsibility for pacing the heart (heart MUST continue to beat!) note that the underlying rhythm has to be regular to be able to distinguish between the two

Answer 7

**Rate:** Can occur at any rate **Rhythm:** Occasionally irregular due to the pause(s) - always measure a pause in seconds * P-P interval may vary after the pause depending on whether SA node regains pacemaker control **P wave:** Normal sinus P's before the arrest **PR interval:** 0.12-0.20 seconds (before the pause); may be shorter or absent after the pause **QRS complex:** \<0.12 (can be \> 0.12 if BBB exist) before the pause * On escape beats, if: * **Junctional escape beat:** \<0.12 secs if AV node escapes as pacemaker (with appropriate P wave characteristics) * **Ventricular escape beat:** \>0.12 secs if Purkinje fibers escape as pacemaker (with NO P waves)

Answer 8

**Causes:** * Myocardial ischemia or infarction * Vagal stimulation * Sinus node ischemia * hypoxia * hyperkalemia * Medication (Digitalis toxicity, beta blockers, calcium channel blockers) **Adverse Effects:** Frequent/very long sinus arrest can cause decreased cardiac output **Treatment:** attempt to correct underlying cause

Answer 9

d) sinus arrhythmia

Answer 10

1. Premature Atrial Complex 2. Wandering Atrial Pacemaker 3. Supraventricular Tachycardia 1. Atrial trachycardia 2. AV Nodal Re-entrant tachycardia (SVT) 4. Atrial Flutter *with block ratio* 5. Atrial Fibrillation 1. Slow Atrial Fibrillation 2. Atrial Fibrillation 3. Rapid Atrial Fibrillation 4. Uncontrolled Atrial Fibrillation

Answer 11

* impulse originates in one or more irritable foci (location) in the atria, depolarizes the atria and heads down the conduction pathway towards the ventricles * **remember:** atria is NOT considered "inherent" (like SA node, AV node, Purkinje fibers), yet acts like another pacemaker of the heart * a rhythm that begins in the atria will have P waves that are differently shaped from the P waves that begin in SA node * because remember that P waves reflect atrial depolarization

Answer 12

1) Altered automaticity OR 2) Re-entry

Answer 13

Caused by an acceleration in depolarization (ussually results from high Na+ leakage into cell) **One of the following occurs:** 1. cardiac cells that are NOT associated with pacemaker function begin to depolarize spontaneously 2. A pacemaker site other an SA node increases it firing rate beyond which is considered normal

Answer 14

* cells initiate an impulse BEFORE the SA node impulse * can occur in both normal pacemaker cells and contractile cells (that do not normally function as pacemaker sites)

Answer 15

* Reactivation of myocardial tissue for the **2nd** or **subsequent** **time** by **the same impulse** * Occurs when an impulse is **DELAYED, BLOCKED or BOTH** in one or more segments in the conduction system * The propagation of the impulse fails to end and continues activating excitable tissue which have just become **polarized**

Answer 16

* impulse originates from an irritable atrial focus before the next sinus beat is due (i.e PACs occur early before the next expected beat) * **is NOT the entire rhythm** - it is a single beat occuring in an underlying rhythm * ex. Sinus tachycardia with a PAC (5th complex)

Answer 17

* if the irritable site is close to the SA node, the atrial P wave will look similar to P wave initiated by SA node BUT WILL BE DIFFERENT * morphology may look: * **1) biphase, "notched", pointed, flattened OR** * **2) buried in the preceding T wave** (T wave may have an extra "hump" suggestting presence of hidden P wave)

Answer 18

Compensatory (complete) pause OR Non-compensatory (incomplete) pause

Answer 19

* pause is compensatory if the **normal beat following PAC occurs WHEN IT IS expected** * if you measure from R wave of complex BEFORE the PAC to the R wave of the complex AFTER the PAC, the period between the complex before and after the premature beat is the same as two normal R-R intervals

Answer 20

**NSR:** two R-R intervals are exactly equal distance apart **NSR with PAC (3rd complex):** * Two R-R intervals that are unequal distance apart * The distance before and after the PAC IS equal to two normal R-R intervals and therefore considered compensatory (complete)

Answer 21

* pause is non-compensatory if the **normal beat following the PAC occurs BEFORE it was expected** * Measure from R wave of complex before the PAC to the R wave of the complex AFTER PAC (i.e. the period between the complex before and after the premature beat is less than normal R-R interval)

Answer 22

**NSR:** Two R-R intervals are exactly equal distance apart **NSR with a PAC (3rd complex):** two R-R intervals that are unequal distance apart; the distance before and after the PAC is NOT equal to two normal R-R intervals and therefore considered non-compensatory (incomplete) as it's actually shorter than two normal R-R intervals

Answer 23

* PACs that are very premature which will NOT be conducted to the ventricle because it will arrive during the ventricle's absolute refractory period * P waves may or may not be followed by a QRS depending on how premature the PAC is * occur because the AV junction is still refractory to stimulation and is unable to conduct an impulse to the ventricles thus no QRS complex

Answer 24

* P waves may or may not be followed by a QRS depending on how premature the PAC is (may occur very early and close to the T wave of the preceding beat so only P wave seen) * **always be suspicious when T waves change shape suddently!** if one T wave is different, there's probably a P wave hiding in it \*NOTE: non-conducted PACs may be confused with sinus block or sinus arrest (especially if P wave of PAC happens early enough to be hidden in the preceding T wave) - to differentiate between the, look and compare T wave contours (in sinus block/arrest, no P wave is producted so the T wave remains the same morphology; in non-conducted PAC, an early abnormal P wave of the PAC will distort preceding T wave)

Answer 25

**Rate:** Can occur at any rate **Rhythm:** occasionally irregular **P wave:** Shaped different from sinus P waves; can be upright and pointed or inverted depending on its origin (premature P waves may be hidden in T wave and if so may deform T wave - in these cases, compare the T waves preceiding each PAC with those of the underlying rhythm) **PR interval:** 0.12-0.20 secs **QRS complex:** \<0.12 secs (or will be absent if it's a non-conducted PAC)

Answer 26

**Causes:** * **Acute Coronary Syndromes (ACS)** - eg. STEMI, non-STEMI, unstable angina * **CHF** * **Atrial enlargement** * **Valvular heart disease** * **Emotion stress** * **Electrolyte imbalance** * **Hyperthyroidism** * **Medication** - Digitalis toxicity * **Drugs** - cocaine, tobacco, caffeine **Adverse Effects:** frequent PACs may be an early sign of heart failure or atrial fibrillation **Treatment:** reduce stress, reduce stimulants

Answer 27

* Transient pacemaker shifting from SA node to another pacemaker site in the atria or AV junction * size, shape and direction of P waves vary, sometimes from beat to beat

Answer 28

* impulse originates in at least 3 different foci (location) in the atria (the difference in the look of P waves is the result of pacemaker shifting between the SA node, atria and AV junction) * heads down the normal conduction pathway and ultimately depolarizes the ventricular muscle

Answer 29

**Rate:** \<100 (usually 50s - 60s) **Rhythm:** regular, BUT may be irregular as pacemaker site shifts from SA node to ectopic locations **P wave:** _at least 3 different shape_s (hallmark sign); some beats may have no visible P waves **PR Interval:** varies (because P wave varies) **QRS complex:** \< 0.12 secs (can be \> 0.12 if BBB exist)

Answer 30

**Causes:** * **may occur in healthy individuals** (eg. athletes, during sleep) * **heart disease** * **medication** (Digitalis toxicity) **Adverse Effects:** usually no ill effects **Treatment:** usually none needed; typically resolves on its own

Answer 31

* A fast, regular and narrow dysrhythmia originate somewhere above the ventricles ("supra" meaning above) * Its exact location of origin can not be identified due to the absence of P waves (P waves may be buried in QRS complex) * can also be used to describe an "umbrella" of tachycardias that originate above the ventricles in either SA node, atria, or AV junction * 3 main types of SVT: * **atrial tachycardia (AT)** * **AV nodal re-entrant tachycardia (AVNRT)\*** *what paramedics call SVT* * **AV re-entrant tachycardia (AVRT)**

Answer 32

* usually caused by altered automaticity (irritable site in the atria fires at a rate of 100-250 times per minute) * often precipitated by a PAC * heads down the normal conduction pathway and ultimately depolarizes into ventricular muscle * typically present when 3 or more PACs occur in a row of \>100 BPM * **hard to different between sinus tach and atrial tach** (you'd have to see a long ECG tracing and the rhythm that precedes atrial tach to call it atrial tach)

Answer 33

**Rate:** 100 - 250 beats/min **Rhythm:** regular **P wave:** upright P wave in Lead II * if rhythm originated in lower portion of atrium, P's will be negative in Lead II) * matching and precede each QRS complex (P wave looks different from those seen when the impulse is initiated from the SA node) **PR interval:** may be shorter or longer than normal **QRS complex:** \<0.12 seconds (can be \>0.12 seconds if BBB exists)

Answer 34

**Causes:** * can occur in person's with normal heartbeats * Myocardial Infarction (MI) * Acute illness with catecholamine release * Electrolyte imbalance * Infection * Medications - albuterol, theophylline * Drugs - caffeine, cocaine, etc. **Adverse Effects:** decreased cardiac output secondary to rapid HR **Treatment:** None

Answer 35

* most common type of SVT * impulse originates from an irritable side above the Bundle of His * exact location of origin CANNOT be identified because P waves are not discernable * P waves may be hidden in T wave of preceding complex * heads down normal conduction pathway and ultimately depolarizes in ventricular muscle * usually caused by a PAC * impulse is stuck in a re-entry loop as it enters the AV node * impulse re-enters the normal electrical pathway with each pass of the circuit

Answer 36

**Rate:** \>100 (generally \>150) **Rhythm:** regular **P wave:** no P waves (P waves are non-discernable) **PR interval:** n/a (because no P waves) **QRS complex:** \<0.12 secs (narrow)

Answer 37

**Causes:** typically occurs: * later in life for unknown reason not determined (30s-40s) * in individual with no structural heart disease AND triggered due to hypoxia, stress, anxiety, caffeine, smoking, sleep deprivation and medications * women more than men * in persons with COPD, CAD, valvular heart disease, CHF, and Digitalis toxicity **Adverse Effects:** decreased cardiac output secondary to rapid HR **Treatment:** None

Answer 38

* SVT that starts and ends suddenly * "paroxsymal" can describe a rhythm that starts and stops suddenly * you have to witness the SVT starting to be able to call it PSVT (otherwise it's just SVT)

Answer 39

* A rapid re-entry circuit caused by an irritable focus within the atria * so rapid that "flutter" wave are produced instead of P waves * usually saw shaped and no P waves * typically would not see isoelectric line because the flutter waves affect the whole baseline so much

Answer 40

* impulse originates in a irritable atrial focus AND rapidly circles a round a larger area of tissue continuously (eg. entire RA and arrives back at the same point) * AV node is bombarded with impulses and allows some to go through and blocks others (protects the ventricles from extremely fast impulses) * heads down the normal conduction pathway and ultimately depolarizes into ventricular muscle * the irritable focus typicall depolarizes at a rate of 300/min BUT AV node can't conduct faster than 180 impulses/min due to its intrinsic conduction rate (otherwise if impulse was transmitted to ventricles, ventricular rate would be 300/min)

Answer 41

**Rate:** Atrial rate - 250 - 350; ventricular rate - 60 -100 * ventricular rate depends on number of impulses the AV node conducts (eg. if AV node conducts 1 impulse every 2 atrial contractions, conduction block/ratio would be 2:1 block/ratio) - i.e. two flutter waves for every 1 QRS * **Three flutter waves for every one QRS: 3:1 block/ratio** * **Four flutter waves for every one QRS: 4:1 block/ratio** * **Five flutter waves for every one QRS: 5:1 block/ratio** * If block/ratio is inconsistent, it is referred to as "variable block/ratio" **Rhythm:** regular if conduction ratio is constant; irregular if conduction ratio varies **P wave:** NO P waves; flutter waves present (hallmark signs) - "saw tooth", "picket fence", V-shaped, upside down V-shaped * 2 or more flutter waves to each QRS * some flutter waves may be hidden inside QRS and T waves even though you can't see flutter waves, they still count (count those inside the these components) **PR Interval:** n/a (since no real P waves) **QRS Complex:** \< 0.12 seconds (can be \>0.12 if BBB exist)

Answer 42

**Causes:** commonly associated with * CHF * cardiomyopathy * cardiac hypertrophy * myocarditis * pericarditis * hypoxia **Adverse Effects:** can be well tolerated at normal ventricular rates; at higher rates, may see signs of decreased cardiac output **Treatment:** None

Answer 43

* Increased irritability causes many sites/foci in the atria to initiate an electrical impulse at the same time (seen as a wavy line) * caused by enhanced automaticity or re-entry

Answer 44

* atria depolarizes in section instead of a unit causing a "wiggle" or quiver (fibrillate) instead of a contraction - like a bag of worms * AV node is bombarded with impulses (some are allowed through, but blocks others) * at irregular intervals, one electrical impulse is conducted * heads down the normal conduction pathway and ultimately depolarizes into ventricular muscle

Answer 45

**Rate:** atrial rate of 250-750 * **Slow atrial fibrillation:** ventricular rate of \<60 * **Atrial fibrillation:** ventricular rate 60 -100 * **Rapid atrial fibrillation:** ventricular rate of \>100 * **Uncontrolled atrial fibrillation:** ventricular rate of \>150 **Rhythm:** irregularly irregular, completely unpredictable * atrial depolarization occurs very irregularly which results in irregular ventricular depolarization **P wave:** Fibrillatory waves are present, NO P waves (if there are P waves, the rhythm is NOT atrial fibrillation) **PR Interval:** n/a (not measured since no real P waves) **QRS complex:** \<0.12 secs (can be \>0.12 if BBB exist)

Answer 46

**Causes:** * **Idiopathic (no clear cause)** * **Advanced age** * **HTN** * **heart disease and MI** * **Pericarditis** * **Lung Disease** * **Pulmonary Embolism** * **CHF** * **WPW** * **Hyper/hypothyroidism, hypokalemia, hypoxia, hypoglycemia** * **Infection** * **Sympathomimetics** * **Electrocution** * **Stress, etc.** **Adverse Effects:** * Blood clots collecting in a sluggish atria causing MI and strokes (so that's why they are on blood thinners - the blood clots can circulate to the brain) * Decreased cardiac output secondary to rapid HR **Treatment:** None