emt 230 Flashcards
The coronary arteries deliver _____ml of blood to the myocardium each minute?
200-250 ml
The L main coronary artery supplies what part of the heart?
The L ventricle, the interventricular septum, and part of the R ventricle
The R coronary artery supplies what part of the heart?
The R atrium and ventricle, part of the L vent, and the conduction system
Avg stroke volume is ___ml for an adult
70 ml
Preload? End-diastolic volume?…definitions
Preload - the volume of blood returning to the heart
End diastolic - the volume returning to each ventricle
Cardiac output is?
the amount of blood pumped by the ventricles in 1 min
Afterload (definition)…..a result of?
the pressure within the aorta before ventricular contractions. A result of peripheral vascular resistance
How is afterload reduced?
lowering bp and vasodilators
Parasympathetic control of the heart is through the ____ nerve?
Vagus nerve - reduces HR and to a lesser extent contractility
Sympathetic nerve fibers originate in _____ region of the spinal cord
Thoracic region
The resting membrane potential inside a cell is appx ____ to ____ mV
-70 to -90 mV.
What electrolyte/ion is most responsible for cardiac contraction?
Calcium
Give 2 examples of calcium channel blockers
Verapmil and ditiazem
What happens is phase 0 of the cardiac action potential?
Rapid depolarization - rapid entry of sodium into the cell, this causes the inside of the cell to become more positively charged than the outside….leading to muscular contraction
What are the 2 ways basic ways ectopic impulses are generated?
Enhanced automaticity and reentry
Phase 1 of cardiac action potential?
the early rapid repolarization. Returns the cell membrane to it’s resting permeability state
Phase 2 of the cardiac AP?
The “plateau phase”. Prolonged phase of repolarization of the AP
Phase 3 of the cardiac AP?
The terminal phase. It results in the inside of the cell becoming negatively charged. Repolarization is completed by the end of this phase
Phase 4 of the cardiac AP?
the period between action potentials
EKG paper: each sm square is equal to ____ seconds?
.04 seconds
EKG paper: each small square (height/amplitude) is equal to _____ mV?
0.1 mV
PR segment…begins and ends where?…
starts at the end of the P wave and ends at the onset of the QRS complex
PR interval…begins and ends where?
starts at the beginning of the P wave and ends at the onset of the QRS complex
The duration and amplitude of the P wave is normally?
duration: 0.1 seconds or less
amplitude: 0.5 - 2.5 mm
Normal P-R interval duration?
0.12 - 0.20 sec
Normal QRS complex duration?
0.08 - 0.10 sec
The triplicate method can be used when?
the rhythm is regular and the HR is above 50
R-R method is used when?
The rhythm is regular and it can also be used for HR’s under 50
6 second count method used for?
appx rate in regular and IRREGULAR rhythms
If the distance between the R to R waves are equal or vary by less than ____ sec, they are considered regular.
0.16 second
Any duration greater than ____ is considered a prolonged P-R interval and indicates an AV block
0.2 second
Most SVT’s are likely caused by what?
A reentry mechanism that involves abnormal pathways in the AV node
SVT’s are rare in pt’s with _____?
myocardial infarction
SVT typical rate?
150 - 250 beats/min
Treatment (in order) for symptomatic narrow complex SVT?
vagal maneuvers and adenosine, calcium channel/beta blockers (stable pt’s only), then synchronized cardioversion beginning at 50 J
NEVER administer diltiazem or verapamil to a pt with what rhythm?
V-tach
Signs and symptoms of CHF with impaired cardiac function?
jvd, dyspnea, tachycardia, chest pain, or decreased LOC
Atrial flutter is almost always a result of ?
rapid atrial reentry focus
What drugs are used to treat pt’s with rapid a-fib?
Diltiazem, beta blockers, calcium channel blockers. Possibly amniodarone or digoxin if used within 48 hrs of a-fib onset.
The pt is at an increased risk of _____ when a-fib or a-flutter has been present for more than 48hrs.
Emboli Formation. “throwing a clot” …this usually occurs when a-fib is converted suddenly to a sinus rhythm.
What drugs should never be given to a pt with WPW?
adenosine, diltiazem, verapamil, digoxin, and in most cases beta blockers. These drugs may cause a dangerous increase in HR
The initial shock to convert A-fib should be set at ___?
synchronized shock
100-120 J biphasic (200 J monophasic)
What are the 3 main P-wave characteristics in a junctional dysrhythmia?
1) inverted P wave in lead II with a short P-R interval
2) absent P wave
3) P wave after the QRS complex
3 ECG features found in VENTRICULAR dysrhythmias?
1) QRS complexes are wide and bizarre in appearance
2) P waves may be hidden in the QRS complex
3) ST segments usually deviate from the baseline
Ventricular Escape Complex/Rhythm is also known as ___?
Idioventricular Rhythm
Ventricular Escape dysrhythmias happen when ___?
impulses from higher pacemakers fail to fire or reach the ventricles or when the rate of discharge of a higher pacemaker falls below the rate of the ventricles.
What dysrhythmia is often the first seen after defibrillation?
Ventricular escape rhythm
R on T phenomenon definition?
The occurrence of ventricular depolarization during the refractory period
V-tach is defined as?
3 or more consecutive ventricular complexes that occur at a rate of 100+ beats/min
Torsades de pointes definition
a type of polymorphic ventricular tachycardia
Any wide complex tachycardia that occurs with serious signs and symptoms requires what?
immediate cardioversion
When is a precordial thump appropriate?
when unstable v-tach is witnessed and cardioversion is not immediately available
What is the most common initial rhythm disturbance in sudden cardiac arrest?
v-fib
4 possible causes of pacemaker malfunction
1) battery failure 2) runaway pacemaker
3) failure of the sensing device 4) failure to capture
ECG abnormality for a 1st degree AV block
a prolonged, constant P-R interval is often the only alteration on the ECG
ECG abnormality for a 2nd degree AV block - type I
aka Wenckbach or Morbitz I
A cyclical pattern where the P-R intervals get progressively longer until a P wave is not followed by a QRS complex. ( a missed beat)
Where are 2nd degree AV blocks - type II usually located?
below the bundle of His
2 ECG criteria for recognizing a bundle branch block?
1) a QRS complex equal or greater than .12 sec (wide complex “rabbit ears)
2) QRS complexes produced by supraventricular activity.
When viewing a 12-lead, which leads are best for viewing ventricular conduction disturbances?
V1 and V6
What class of drug is Lasix (Furosemide)?
loop diuretic
What action should you take for a pt with an unstable, bradycardic rhythm?
Pace the pt
What position should a pt with chest pain be in?
semi-fowlers
Depolarization of the heart is dependent on what?
Sodium/Potassium pump
A heart failure pt should be positioned at what angle?
45 degrees
When the heart can’t meet the metabolic needs of the body…..this is referred to as?
Cardiogenic shock
Never pace a pt with PEA
Never pace a pt with PEA
What part of the EKG show atrial depolarization?
P wave
What type of nerve fibers go through the heart
sympathetic
Sinus tachycardia is commonly caused by ____?
an increase in sympathetic tone
What may be a lethal treatment for a pt with a ventricular escape rhythm?
Lidocaine
Leads I, II, and III are referred to as ______ or _______ leads
bipolar or limb leads
What type of valves prevent the backflow of blood into the ventricles?
semilunar valves
Starling’s Law
Myocardial fibers contract more forcefully when they are stretched
Automaticity in cells?
cardiac fibers have specialized cells that can generate their own electrical impulses spontaneously
Bipolar leads have what type of electrode charge?
Each of the bipolar leads has one positive electrode and one negative electrode
What are the 3 augmented leads? Bipolar or Unipolar?
Unipolar leads. aVR, aVL, and aVF
In augmented leads, the current flows from the heart ______ to the extremities
outward
V1 - V6 are _____ leads
unipolar. aka precordial leads
What part of the EKG represents ventricle relaxation and repolarization?
T wave
Collateral circulation allows for what?
_____ makes collateral circulation possible
Collateral circulations allows for an alternate path of blood flow in the event of a vascular occlusion.
ANASTOMOSES (comm between two or more vessels) make coll circ possible
Blood vessels and arterial walls have 3 layers, what’s the middle layer called?
Middle is the tunica media
Main differences between a 2nd degree type I and II AV block
The P-R interval progressively lengthens in Type I whereas it’s usually constant for Type II.
Type II will have more frequent missed QRS complexes.
Type II generally has a wider QRS complex compared to Type II is usually associated with an MI
Type I is usually transient and reversible
