CVPR 03-31-14 11am-Noon Arrhythmias slides - Horwitz Flashcards Preview

► Med Misc 16 > CVPR 03-31-14 11am-Noon Arrhythmias slides - Horwitz > Flashcards

Flashcards in CVPR 03-31-14 11am-Noon Arrhythmias slides - Horwitz Deck (45):

Normal conduction pathway & waves generated

SA node generates an electrical impulse which cannot be seen on the ECG ---> electrical current travels through Rt. & Lt. atrial muscles and atrial depolarization is visible as the P wave ---> electrical impulse then arrives at AV node, which conducts electricity at a slower pace, creating a pause (PR interval) before the ventricles are stimulated [pause allows blood to be emptied into ventricles from atria prior to ventricular contraction] ---> QRS is due to ventricular depolarization ---> T-wave is due to repolarization


Sinus rhythm

Ever QRS is triggered by a P wave (P before QRS)


Normal sinus rate in adults

60-100 beats/min


Normal PR interval in adults

0.12-0.20 seconds


Normal QRS in adults

Whereas the QRS is normally narrow, if there is widening of the QRS (as occurs w/bundle branch blocks) but there is a P wave preceding each QRS by a normal PR interval, the rhythm is still sinus…… If the rate is 60-100, the QRS is regular, or only varies slightly due to respiration, and each QRS is preceded by a normal P wave with a normal PR interval, it is normal sinus rhythm.


Sinus Tachycardia - causes

Commonly occurs during exercise or emotional stress, with no treatment generally needed (appropriate compensatory increase in HR)….. In pts w/coronary artery disease as well as in hyperthyroidism, the increased cardiac oxygen demand may precipitate angina …… May also be caused by hypotension, acute lung/abdominal pathology, Thyrotoxicosis


Sinus Tachycardia – typical rates & ECG findings

Regular, fast …..Typical rates are 101-150…..Normal P & QRS


Sinus Tachycardia – treatment

Usually none is needed, but would want to look for underlying disease if it occurs at rest….. If treatment needed (as in thyrotoxicosis), beta blockade is usually effective


Sinus Bradycardia - causes

Common in normal individuals, especially athletes; Vagotonic states (faint; sick sinus syndrome; small inferior infarctions which increase vagal tone)


Sinus Bradycardia – symptoms

Can cause syncope, lightheadedness or fatique in elderly patients w/age-related dysfunction - the ‘sick sinus syndrome’


Sinus Bradycardia – typical rates & ECG findings

Regular, slow HR (


Sinus Bradycardia - treatment

Often requires no treatment; However, it may produce syncope during intense vagal activation as in fainting (‘Vaso-Vagal event’), for which atropine is effective. Treatment of sick sinus syndrome may require placement of an electronic pacemaker.


First-degree AV block – ECG findings

PR interval prolonged (>0.2 s, or more than one large block) = increased junctional delay


First-degree AV block – causes

Most commonly drug-induced (beta-blockers, some Ca2+ blockers [diltiazim, verapimil], digitalis. Also, conduction system disease


First-degree AV block – severity of the problem

Benign condition, but can proceed to more serious type of block


Second-degree AV block - causes

Some P waves conduct normally to the ventricles, but some do not (patterns vary…. Some P waves not followed by QRS; may or may be change in PR interval in normal P/QRS)….. May reflect conduction system disease, high vagal tone, or excessive effects of drugs


Second-degree AV block – symptoms

If rate is too slow to support cardiac output adequately, syncope or confusion may occur, requiring a pacemaker


Second-degree AV block - Mobitz type 1 vs. type 2

Mobitz 1 type: PR gets longer & longer until a P does not conduct (no QRS) = usually less severe….. Mobitz 2 type: no change in PR, just P waves sometimes not followed by a QRS (generally more sever & worry about transition to 3rd degree AV block)


Third-degree AV block – causes

Due to AV node or “junctional” failure with aging, infarct, severe conduction system disorders or disruption during cardiac surgery; Rarely drug-induced


Third-degree AV block – On ECG + symptoms/outcomes

Complete Heart Block…. Both Ps & QRSs show regular rhythm, but they are at different rates, with P rate > QRS rate…. No relationship between P and QRS waves (a pacemaker below the AV node has taken over)….. May cause syncope or sudden death


Third-degree AV block – treatment

Pacemaker if ventricular rate or BP are to low (probably a permanent pacemaker)


Premature atrial beat/contraction

Typically an abnormally-shaped P wave before a normal,narrow QRS, w/out widening of PR …. Usually benign


Premature ventricular beat/contraction

Typically QRS widens substantially and has no P wave in front of it….. Ectopic Ventricular Focus – conducted by slow myocardium (no Purkinje)….. Short path length blocks Re-entry …..Usually benign


Premature Atrial/Ventricular Contractions

Both are common in healthy persons and are experienced as single-beat palpitations….. Most commonly noticed at rest when low HR permit occurrence of premature ‘skipped beats’ and when distractions are reduced allowing awareness.


Atrial flutter – findings

P waves (flutter waves) at a rate of 240-320 bpm….. Pulse may be regular (most commonly) or irregular….. sawtooth pattern ….. Ventricular rates vary widely, but are typically rapid if untreated


Atrial flutter has some risk of...

Embolic stroke due to clot in left atrium (not as common an outcome as it is in atrial fibrillation)


Atrial flutter – treatment

Anticoagulation for embolism risk; Rate control w/drugs (beta-blockers, Ca2+ channel blockers - not the-pines, rather verapamil & diltiazem); Cardioversion; Ablation of reentry site


Atrial Tachycardia – symptoms/findings

Quite uncomfortable & disturbing….. Rapid HR: at Baseline = 70; during episode = 180….. Narrow QRS complexes with P waves present before but abnormal


Atrial Tachycardia - Treatment

Easily terminated by adenosine infusion… But, recurrence common, which can be prevented by ablation of the reentry pathway…. Also, vagal maneuver (cold towel on face) to decrease HR; beta blocker; or verapamil/diltiaem


Atrial fibrillation - findings

Irregularly irregular ventricular rhythm (completely irregular QRS)- typically fast if not on drugs….. NO P waves at all…. May be either a chaotic or create an undulating baseline


Atrial fibrillation –causes

A ton of impulses hitting the AV node every minute; only some can be conducted, whenever AV node is able….NI subjects (“lone A fib”); Aging (common); Post-Op; Heart disease (common); Hyperthyroidism


Atrial fibrillation – problems/symptoms caused

Rapid HR (---> syncope, ischemia, HF)….. Loss of Atrial Kick (---> HF)….. Atrial Thrombi (---> embolic stroke)


Atrial fibrillation – treatments

Most patients are anticoagulated & given rate control drugs, b/c of high recurrence rate of A fib….. May also require cardioversion (electrical shock or drugs; must first be anticoagulated if there is a clot) or ablation (not as successful as in flutters)


Anticoagulation in Atrial fibrillation

Usually wararin is used, but aspirin may be used in low-risk cases…..nearly all pts are anticoagulated b/c of risk for embolic stroke


Rate control drugs in Atrial fibrillation

Beta-blockers…..some Ca2+ channel blockers (diltiazem or verampamil)….. Digoxin …. Singly or in combo)


Cardioversion in Atrial fibrillation

Conversion to sinus rhythm can be achieved w/electrical cardioversion drugs or w/drugs…… However, maintenance of sinus rhythm often requires drugs with high toxic potential ---> thus, generally reserved for pts in whom rate is poorly controlled, there are intolerable palpitations, or who need their “atrial kick” to maintain cardiac output…… Pts w/out underlying heart disease or patients who have minimal evidence of pathology may also be cardioverted for AF b/c of better results in maintaining sinus rhythm.


Reentry Arrhythmias

Abnormal reentry pathways may be present in the atria, ventricles, or the junctional tissue…. While arrhythmias may arise from a single ectopic pacemaker, most ectopic rhythms arise from reentry


Mechanism of Reentry

In normal heart, arrhythmias are self-terminating b/c depolarization at a junction usually meets tissue which has already been depolarized & is therefore refractory to reentry…… BUT, if chamber dilation and/or islands of fibrosis create a long & circuitous path, depolarization can continue to find non-refractory myocardium and be sustained = reentry


Junctional Rhythms – defn.

The region surrounding the AV node is often termed “the junction” and rhythms originating there are called “junctional rhythms”.


Junctional Rhythm – findings

Regular rhythm which may be slow or fast….. Narrow (normal) QRS complex….. NO antecedent P waves (buried before/after the QRS); sometimes P wave seen after the QRS


Ventricular Tachycardia (VT) – causes/mechanism

From fibrosis, infiltrate, or dilation…..Ectopic ventricular focus – conducted by slow myocardium (no Purkinje)…. Long pathway length permits re-entry


Ventricular Tachycardia (VT) – findings

Repetitive, wide, and abnormally shaped QRS (a bunch of hills close together)….. NO P wave usually…. Termed “sustained” if QRS last most than 30s (often life-threatening)


Treatment of ventricular tachycardia

Lidocaine, amiodarone, cardioversion


Life-threatening tachycardias

“Sustained” ventricular tachycardia or VF require emergency defibrillation……There is typically ABNORMAL ventricular contraction in VT & there is NO contraction in VF….. In asystole, only a straight line is seen on the ECG and prognosis is dismal.


Ventricular defibrillation

No consistent QRS or coordinated conjunction (no pattern at all) – will die quick if don’t shock (defibrillate)

Decks in ► Med Misc 16 Class (28):