Cardiac 2 Flashcards
What valves are open/closed during diastole?
Open: AV valves
Closed: Semilunar valves
What area of the heart is filling/emptying during diastole?
Filling: Ventricles
Emptying: Atria
What electric activity corresponds to diastole?
T wave
What heart sound occurs during diastole?
S2 (Closure of semilunar valves)
What valves are open/closed during systole?
Open: Semilunar valves
Closed: AV valves
What area of the heart is filling/emptying during systole?
Emptying: Ventricles
What electric activity corresponds with systole?
The QRS complex
What heart sound occurs during systole?
S1 (closure of AV valves)
The greater the preload the greater the _______.
Cardiac Output
An increase in contractility is demonstrated on a Frank-Starling diagram by:
Increased cardiac output for a given EDV
Walk through the conduction system of the heart beginning with SA node.
SA node –> atrial conducting fibers –> AV node –> Bundle of His–>Bundle branches (R/L) –>Purkinje fibers
What is the pacemaker of the heart? What does it normally set the rate to?
SA node
60-100bpm
What is CN X’s affect on HR?
Slows the rate (parasympathetic)
What corresponds to the SA and AV nodes firing?
The SA node causes the atria to contract and the AV node causes the ventricles to contract
What does the the P wave correspond to?
Atrial contraction (depolarization)
What does the QRS complex correspond to?
Ventricular contraction (depolarization)
What does the T wave correspond to?
Ventricular relaxation (repolarization)
What does the U wave correspond to?
The repolarization of the Purkinje fibers
Often not visible, best seen on leads V2 and V3
What does the PR interval represent?
atrial, AV node, and Purkinje depolarization
The physiologic function of the relatively slow conduction through the AV node is to allow sufficient time for:
Ventricular filling
Name the three layers of the artery from innermost to outermost:
- Tunica intemae
- Tunica media
- Tunica adventitia
How do the anatomy of the veins and arteries contribute to different functions?
- Arteries are muscular, thick, and elastic. They are able to sustain higher pressures
- Veins are muscular, thin, and elastic. They contain semilunar valves to direct flow.
What factors determine blood flow? (2)
- Pressure (force exerted)
2. Resistance (opposition to force)
Blood pressure = ______ x ________
Cardiac Output x Peripheral Resistance
What are some genetic and environmental factors that could lead to hypertension?
- Defects in renal Na homeostasis
- Functional vasoconstriction
- Defects in vascular smooth muscle and growth structure
What can preload be equated to?
EDV
What is afterload?
The pressure during ejection that the LV must overcome to eject.
What three factors make up Vichrow’s triad and what do they result in?
- Endothelial (intimal) injury
- Venous stasis
- Hypercoagulability
=THROMBOSIS
What is shock?
An imbalance between oxygen supply and oxygen demand at the cellular level.
=hypoperfusion and impaired cellular oxygen utilization
What are the four major types of shock?
- Cardiogenic
- Obstructive
- Hypovolemic
- Distrubutive
What is the pathogenesis of cardiogenic shock?
Blood pump problem; inadequate CO despite sufficient vascular volume
What is the pathogenesis of obstructive shock?
Blood flow problem; circulatory blockage such as a large PE or cardiac tamponade= disrupts CO
What is the pathogenesis of hypovolemic shock?
Blood volume problem; Loss of blood volume as a result of hemorrhage or excessive loss of extracellular fluids
What is the pathogenesis of distributive shock?
Blood vessel problem; greatly expanded vascular space because of inappropriate vasodilation
Acyanotic congenital heart defects cause what type of shunt. Give examples.
L –> R shunt
ASD, VSD, PDA, CoA, PS, or AS
Cyanotic congenital heart defects cause what type of shunt? Give examples?
R–>L shunt
Tet, d-TGA, Truncus, TA
______ delivers oxygenated blood to the fetus in fetal circulation.
Umbilical vein
What are the four components of a Tet?
- Large VSD
- Overriding Ao (over VSD instead of LV)
- RV hypertrophy
- PS or PA
What is Kawasaki Disease?
A mucocutaneous lymph node syndrome. Acute, self limiting systemic vasculitis that may result in cardiac sequalae.
What is pediatric systemic hypertension defined as?
SBP and DBP >95th percentile for age and gender on at least three occasions.
What are some underlying disease that could cause HTN in pediatric patients?
Renal disease
CoA
Adrenal tumors
Space occupying lesions of the cranium
What are some complications of shock?
DIC Acute Renal Failure ARDS MODS GI Ischemia
What are the three clinical stages of shock?
- Compensated (homeostatic mechanisms)
- Progressive (hypotensive, immediate intervention)
- Refractory (unresponsive to treatment)
When can S3 be heard?
Abnormal
Dilated heart
Also known as the Kentucky gallop
d/t: Increased blood volume, stiff chordae tendinae, HF (more volume at end of systole)
When can S4 be heard?
Abnormal
Stiffened ventricle/restrictive cardiomyopathy
“Atrial kick”
Also known as the Tennessee gallop
d/t:
Turbulent blood flow against stiffened ventricular walls
Hypertrophy
Atrial contraction attempting to overcome hypertrophic ventricle
What happens during atrial systole?
An atrial contraction causes a small amount of additional blood into the ventricles
What is End diastolic volume and what is a normal amount.
The maximum amount of blood in the ventricles which occurs at the end of ventricular relaxation.
~135ml
What is happening during isovolumic ventricular contraction?
1st phase of ventricular contraction
Pushes AV valves closed but does not create enough pressure to open semilunar valves
Volume in heart stays the same (isovolumic)
What is happening during ventricular ejection?
As ventricular volume rises and exceeds pressure in the arteries the semilunar valves open and blood is ejected
What is End Systolic Volume and what is a normal amount?
Minimum amount of blood in ventricles at the end of systole.
~65ml
What is happening during isovolumic ventricular relaxation?
As ventricles relax pressure in the ventricle drops causing the semilunar valves to snap shut
Volume in the heart stays the same (isovolumic)
What is the rate of rhythmic discharge of the cardiac cells determined by?
Influx of Na and Ca versus the efflux of K
Spread of an action potential over cardiac muscle cell surfaces results in ___________.
myocardial contraction
What ion concentration difference across the cell membrane is the primary determinant of the resting membrane potential?
Potassium
What happens during phase 0 of an cardiac action potential?
- Membrane potential of the cardiac cell approaches threshold and voltage gated Na channels open
- Na rushes into cell causing depolarization
(Class I antidysrhythmics block voltage gated channels- quinidine, lidocaine)
What happens during phase 1 of a cardiac action potential?
- Na channels close
- K channels open and K leaves cell
- Cell becomes more positive (repolarizing)
What happens during phase 2 of a cardiac action potential?
- Plateau phase (little change in membrane potential)
- Influx of Ca and efflux of K
- This phase is reduced in atrial cells
(Ca channel blockers are used to inhibit this Ca influx. Beta blockers also reduce Ca influx)