advanced EKG

what is systole?

contraction phase (mainly ventricles) → pushes blood to lungs/body

what is diastole?

relaxation phase → atria & ventricles fill w blood; longer than systole

what is an atrial kick?

last bit of blood pushed into ventricles before contraction

what is depolarization?

muscle contraction → sodium and calcium enter cells, potassium exits

what is repolarization?

muscle relaxation → cells returning to resting state

what is a refractory period?

brief time after contraction when no new impulse should occur → if an impulse happens, can cause dangerous arrhythmias (sudden cardiac arrest in athletes)

what is the function of the SA node?

main pacemaker, initiates impulse

what is the function of the AV node?

backup pacemaker, slows impulse to allow ventricular filling

what is the function of the bundle of his & purkinje fibers?

spread impulse through ventricles → depolarization should be < 0.12 sec (narrow QRS)

what is the p wave?

atrial depolarization (contraction)

what is the PR interval?

time from SA node through AV node (0.12 - 0.20 sec)

what is the QRS complex?

ventricular depolarization (normal less than or equal to 0.12 sec → wide/bizarre = ventricular problem)

what is the QT interval?

total ventricular activity (depolarization & repolarization) → normal 0.34 - 0.44 sec; can be prolonged by certain meds

what is the T wave?

ventricular repolarization; peaked T waves can indicate hyperkalemia

what is the ST segment?

ventricular recovery → elevation = STEMI

characteristics of sinus tachycardia?

regular rhythm, rate > 100 bpm → P wave before every QRS, normal PR interval

characteristics of sinus bradycardia?

regular rhythm, rate < 60 bpm → P wave before every QRS, normal PR interval

characteristics of atrial flutter?

sawtooth pattern/flutter waves, not true P waves → QRS complex normal; originates in atria

characteristics of afib?

irregularly irregular rhythm, no distinct P waves → QRX complex normal; originates in atria

characteristics of supraventricular tachycardia?

regular rhythm, rate > 150 bpm, often narrow QRS → P waves may be hidden, originates above ventricles, (symptoms of heart pounding & palpitations)

what is important to know about junctional rhythms?

originate in the AV node (not SA node) → typically slower around 40-60 bpm but accelerated can be at 61-100 bpm → sends impulses backwards and forwards (creates retrograde/inverted p wave)

what are some causes of junctional rhythms?

sick sinus syndrome (SA node doesn’t work), digoxin toxicity, MI, heart sx → tx by addressing underlying cause, may require pacing if symptomatic

in general, what are heart blocks?

delay or blockage in the electrical conduction at the AV node → caused by acute coronary syndrome, electrolyte imbalance, medication toxicities

characteristics of a first degree heart block?

looks like normal sinus rhythm but PR interval is prolonged (> 0.20 sec) → everything else is normal “if R is far from P then you have a first degree”

characteristics of a wenchebach second degree heart block?

type I → progressive PR lengthening until a QRS is dropped; usually intermittent and non-life threatening, “longer, longer, longer drop - now you have a wenckebach”

characteristics of a mobitz II second degree heart block?

type II → PR interval is constant but there are sudden dropped QRS complexes; more serious and can progress to a third degree block; may require pacing, “if some Ps don’t get through then you have a mobitz II”

characteristics of a third degree block?

no communication between atria and ventricles; P waves and QRS march out independently → life threatening, requires pacemaker, symptoms include syncope and low cardiac output “if Ps and Qs don’t agree then you have a third degree”

what is the purpose of pacemakers?

provide electrical stimulus when heart can’t generate impulses; many different types

what are the different types of pacemakers?

• external/transcutaneous: pads on chest, temporary

• epicardial: wires placed during open-heart sx, temporary

• transvenous: wire through vein to heart, temporary

• permanent: implanted device (single, dual, or biventricular chamber)

what are some nursing education/interventions for pacemakers?

monitor HR/rhythm, site care, patient education: no arm movement, keep incision dry, pain management, and regular device checks

what are pacemaker spikes?

sharp vertical lines on EKG before P wave (atrial pacing), QRS (ventricular pacing), or both (dual pacing) → think TMC cardiac rehab 

what does failure to sense mean on a pacemaker?

pacemaker doesn’t detect intrinsic heart activity & fires inappropriately

what does failure to capture mean on a pacemaker?

pacemaker fires but heart doesn’t respond → no depolarization

what does failure to fire mean on a pacemaker?

pacemaker doesn’t emit impulse → battery or device failure

what does the nurse need to do as far as pacemaker malfunctions go?

recognize abnormal patterns, notify provider, monitor patients

what do patient’s need to be aware of if they get a pacemaker?

avoid strong electromagnetic fields (airport security, MRI), wear medical alert bracelet, have regular device interrogation/checks

characteristics of an implantable cardioverter-defibrilator?

detects and treats lethal arrhythmias by delivering a shock; may also pace the heart if needed → need to notify patient that the device may shock unexpectedly if arrhythmia is detected

what are some lethal rhythms?

torsade de pointes (polymorphic vtach), ventricular tachycardia (vtach), ventricular fibrillation (vfib), asystole

characteristics of torsades de pointes?

lethal rhythm → twisting QRS complexes of varying amplitude/direction, associated w prolonged QT interval → need to tx with IV magnesium

characteristics of ventricular tachycardia?

lethal rhythm → wide & bizarre QRS with a rate of > 150 bpm; may have pulse or be pulseless but requires immediate intervention

characteristics of ventricular fibrillation?

lethal rhythm → no organized QRS, chaotic baseline, no pulse; requires immediate defibrillation

characteristics of asystole?

lethal rhythm → flatline, no electrical activity; NOT shockable, tx with CPR and medications