MED SURG EXAM 3

What 4 things is every heart cell capable of?

Automaticity, excitability, conductivity, contractility

Automaticity

cardiac muscle cells can contract (create an impulse) without stimulation

What is the function of the SA node?

pacemaker of the heart (60-100 bpm)

If the SA node is not firing adequately, what takes over?

AV node (40-60 bpm)

What takes over if the SV node AND AV node are not working, what takes over?

Purkinje fibers (20-40 bpm)

Excitability

cell initiated by a cell next to it (and then conduct an impulse)

Contractility

cardiac cells contribute to muscle fiber contraction

Systole

contraction phase (of the heartbeat)

Diastole

relaxation phase (of the heartbeat)

All mechanical activity (contractility) in the heart requires _________

electrical conduction (conductivity)

ECG Monitoring: Isoelectric line

where no electrical activity occurs (baseline)

An ECG monitors ______ over _______

conduction, time

5 lead ECG placement

4 limb electrodes (RA, LA, RL, LL), 1 chest (V1)

3 lead ECG placement

3 limb electrodes (RA, LA, LL)

QRS complex

ventricular depolarization and atrial repolarization

P wave

depolarization of atrium (initiated by the SA node)

T wave

repolarization of ventricles

A positive deflection T wave is _____

rounded

A negative/abnormal deflection T wave is ______

peaked

What should each QRS complex correlate to?

contraction of the ventricle

Normal mechanical response

1 beat per QRS complex (1:1 ratio)

Normal rate

60-100 bpm

Normal PR interval

0.12-0.20 sec (3-5 small boxes)

Normal QT interval

0.34-0.43 sec (depends on HR)

Normal QRS interval

less than 0.12 sec

A normal T wave is ______

rounded (and upright)

sinus bradycardia: ECG abnormality

slower than normal SA node (conduction pathway is normal, but fires at < 60 bpm)

sinus tachycardia: ECG abnormality

faster than normal SA node (firing at 100-150 bpm)

what is an ectopic focus?

site of electrical activity other than the SA node (PAC is in atrium, PVC is in ventricles)

Premature Atrial Contractions (PAC): ECG abnormality

early P wave, compensatory pause

Premature Ventricular Contractions (PVC): ECG abnormality

no P wave, wide QRS (> 0.12 sec), and compensatory pause

What is the focus?

location in the heart where an electrical impulse originates (typically the SA node; 'pacemaker')

R on T phenomenon

R wave falls on the T wave of the preceding complex (seen in PVC)

Run of ventricular tachycardia

3 or more PVCs in a row (ventricle is doing the pacing, no interference from SA node)

Atrial Flutter: ECG abnormality

sawtooth pattern (atrial rate 250-350)

Atrial Fibrillation (AFib): ECG abnormality

no P waves, irregular rhythm, variable rate (disorganized artial activity with NO pacemaker)

atrial kick

blood pushed into the ventricles because of atrial contraction

What happens to the atrial kick in A-Fib?

Loss, causing (20-30%) reduction in cardiac output

Synchronized Cardioversion

R-wave-timed shock for unstable rhythms with a pulse (used in Atrial Fib/Flutter, unstable SVT, and Vtach WITH A PULSE)

Why are anticoagulants used in management of Arterial Flutter/Fibrillation?

may cause blood stasis in atria, allowing for clots (atrial kick is absent/lost)

AFib increases risk of stoke ____x without anticoagulation

5

AFib/Flutter: If the arrhythmia > 48 hrs or unknown duration

anticoagulate 3 weeks before (cardioversion) and 4 weeks after (cardioversion)

AFib/Flutter: If the arrhythmia < 48 hrs

cardiovert immediately, anticoagulate right after

Why is it important to anticoagulate while cardioverting?

clots can be ejected into circulation (causing PE, stroke, etc)

Supraventricular Tachycardia (SVT): ECG abnormality

regular rhythm, narrow QRS complex, obscured P and T waves, HR > 150 (tachycardia with rate too rapid to find impulse)

Reentrant atrial conduction loop

electrical impulse (in the atria) keeps going around in a circular pathway instead of stopping

What does Adenosine do?

slows conduction through the AV node (slows HR, allowing SA node to take back over)

When is adenosine contraindicated?

Sick sinus syndrome (without pacemaker), 2nd or 3rd degree heart block, asthma

Why is adenosine administered via rapid IV push?

metabolizes very fast (administer closest to the heart, ex: AC vs wrist)

Ventricular Tachycardia (Vtach): ECG abnormality

wide QRS (>0.12), HR > 100, absent/obscured P wave

vagal maneuvers

stimulate vagal nerve, slow HR (ice to face, bear down)

Ventricular Fibrillation (Vfib): ECG abnormality

No p waves or QRS (chaotic/quivering)

Asystole: ECG abnormality

flatline (may have baseline sway (if on ventilator), NO electrical activity)

Pulseless Electrical Activity (PEA): ECG abnormality

NSR, no pulse (no mechanical heart contraction despite NSR)

All pulseless rhythms require ______ and ______

CPR, epinephrine (1 mg IV, q3-5 min)

Why is defibrillation only helpful in V-tach or V-fib?

caused by chaotic activity, defibrillation stops activity (in Asystole, there is no activity and PEA has normal activity)

Defibrillation

Immediate, unsynchronized shock when pulseless (used for Vfib without pulse)

Peaked T waves indicate

hyperkalemia, early MI

Inverted T waves indicate

ischemia/MI (often seen in bundle branch block)

Flattened T waves indicate

hypokalemia, ischemia

Biphasic T waves indicate

evolving MI, electrolyte imbalance

True or false: any of the T wave abnormalities can occur with any abnormal rhythm

true

ST elevation

indicator of acute STEMI, rapid intervention (> 1mm above isoelectric line)

ST Depression

may indicate NSTEMI, may be non-urgent (could be due to bundle branch block or digoxin, > 0.5 mm below isoelectric line)

Prolonged QT interval causes

hypomagnesemia, hypokalemia, meds, long QT syndrome (risk of torsades de pointes/Vtach)

Shortened QT interval causes

hypercalcemia, digoxin toxicity (risk of atrial and/or ventricular arrhythmias)

Artifact

distortion on ECG tracing not caused by heart's electrical activity (caused by pt movement, tremors, loose electrodes, broken lead)

heart block

delay interruption in normal electrical conduction pathway (affects AV node or bundle branches)

First Degree AV block

prolonged PR interval (> 0.20, typically asymptomatic)

Second Degree AV block: TYPE I

Progressive PR interval lengthening followed by dropped QRS

Second Degree AV Block: TYPE II

some P waves not followed by QRS

Third Degree Heart Block (complete heart block)

no association between P and QRS, inconsistent PR (wide QRS, >0.12)

Bundle Branch Block (BBB)

wide QRS (rabbit ears morphology)

Cardiac pacing

use of electrical stimulus to initiate or support heart beat (used in bradyarrhythmias, heart blocks, or asystole)

Pacing modes: AAI

atrial activity sensed

Pacing modes: VVI

ventricular activity sensed (ignores atrial activity)

Pacing modes: DDD

atrial and ventricular activity sensed

Post-implantation care for a permanent pacemaker

immobilize arm (24-48 hrs), monitor for infection (bleeding, hematoma), and continuous ECG (AVOID STRONG MAGNETS)

Implantable Cardioverter-Defibrillator (ICD)

device that delivers synchronized cardioversion (corrects Vtach or Vfib, some also provide pacing)

What is the #1 cause of death in the United States?

CAD (1 in 4 deaths occur due to CAD)

Coronary Artery Disease (CAD)

progressive narrowing of arteries (by atherosclerosis)

Ischemia occurs when normal blood flow through a vessel is reduced by _____%

50 (%)

What causes a Myocardial Infarction (MI)?

abrupt stoppage of blood flow through a coronary artery (causing irreversible myocardial cell death/necrosis)

a STEMI is when the thrombus is ______ occluded

fully

a NONSTEMI is when the thrombus is _____ occluded

partially

What is the c-reactive protein test used for?

protein levels connected to inflammation (associated with atherosclerosis)

Acute Coronary syndrome

plaque forms, creates clot and blockage (acute emergency caused by CAD)

Acute Coronary Syndrome (ACS) is the umbrella term that includes what three conditions?

unstable angina, NSTEMI, STEMI

_____ angina develops as a result of Coronary Artery Disease (CAD)

Cardiac enzyme labs elevate around ______ hrs after an MI

4-6 (peak at 18 hrs, slowly return to normal 24-36 hrs post-MI)

What elevated lab is the best indicator of Myocardial Infarction (MI)?

Troponin (I and T)

What happens in a CABG/MIDCAB?

vessels (from other regions of the body are) used to bypass the occluded coronary artery

Cardiac Tamponade

acute compression of the heart (caused by fluid accumulation in the pericardial cavity)

This procedure involves fully open chest, stopped heart, and is used when multiple coronary arteries are occluded

CABG (coronary artery bypass graft)

This procedure involves small incisions between ribs, keeps the heart beating, and usually involves only one occluded coronary artery

MIDCAB (minimally invasive direct coronary artery bypass)

This procedure is minimally invasive and uses laser channels into ventricles (typically used when pt. is not candidate for CABG/MIDCAB)

Transmyocardial revascularization

What are the earliest lesions of atherosclerosis?

fatty streaks

What are the stages of atherosclerosis?

chronic endothelial injury, fatty streak, fibrous plaque

complicated lesion

The incidence of CAD is greatest among what population?

middle aged men (at 75 yrs, incidence among men and women even out)

What population has an earlier onset and greater severity of CAD?

African Americans