Cardiac Pathophysiology Flashcards
Where is the heart located?
In the mediastinum between second rib and fifth intercostal space
Superficial fibrous pericardium
function?
3
- Protects,
- anchors, and
- prevents overfilling
Layers of the heart wall
3
- Epicardium—
- Myocardium
- Endocardium
What is the epicardium?
What is the myocardium made of? 2
Endocardium is continuous with what?
-visceral layer of the serous pericardium
- Spiral bundles of cardiac muscle cells
- Fibrous skeleton of the heart: crisscrossing, interlacing layer of connective tissue
-continuous with endothelial lining of blood vessels
Function of the myocardium? 3
- Anchors cardiac muscle fibers
- Supports great vessels and valves
- Limits spread of action potentials to specific paths
When is pericarditis most likely caused by?
4
- Post viral
- Autoimmune/lupus
- Cancer
- Idiopathic
Tampanade does happen (friction rub) what will they describe it as?
What makes it better? 2
stabbing, shooting, pain of 7 to 10
Leaning forward
Shallow breathing
What encircles the junction of the atria and ventricles?
What is the function of the auricles?
Coronary sulcus (atrioventricular groove)
Auricles increase atrial volume
What marks the interventricular septum externally? 2
Anterior and posterior interventricular sulci mark
What lines the wall of the atria?
What vessels enter the right atrium? 3
What vessels enter the let atrium? 2
Walls are ridged by pectinate muscles
Vessels entering right atrium
- Superior vena cava
- Inferior vena cava
- Coronary sinus
Vessels entering left atrium
1. Right and 2. left pulmonary veins
Ventricles: The Discharging Chambers
- What lines the walls of the ventricles?
- What kind of muscles project into the ventricular cavities?
- What vessel leaves the right ventricle?
- What vessel leaves the left ventricle?
- Walls are ridged by trabeculae carneae
- Papillary muscles project into the ventricular cavities
- Vessel leaving the right ventricle
Pulmonary trunk - Vessel leaving the left ventricle
Aorta
Pathway of Blood Through the Heart
The heart is two side-by-side pumps
- Right side is the pump for the what?
- Left side is the pump for the what?
- Right side is the pump for the pulmonary circuit
Vessels that carry blood to and from the lungs - Left side is the pump for the systemic circuit
Vessels that carry the blood to and from all body tissues
Describe the pathway of blood through the heart?
Including chambers, great vessels and valves
Right atrium → tricuspid valve → right ventricle
Right ventricle → pulmonary semilunar valve → pulmonary trunk → pulmonary arteries → lungs
Lungs → pulmonary veins → left atrium
Left atrium → bicuspid valve → left ventricle
Left ventricle → aortic semilunar valve → aorta
Aorta → systemic circulation
_______ volumes of blood are pumped to the pulmonary and systemic circuits
Pulmonary circuit is a ____, _____-pressure circulation
Systemic circuit blood encounters _____ resistance in the long pathways
Anatomy of the ventricles reflects these differences
Equal
short, low
much
What is Coronary Circulation?
______ _______ varies considerably and contains many anastomoses (junctions) among branches
______ routes provide additional routes for blood delivery
The functional blood supply to the heart muscle itself
Arterial supply
Collateral
What are the arteries in our coronary circulation? 5
What are the veins in our coronary circulation? 3
Arteries
- Right and
- left coronary (in atrioventricular groove),
- marginal,
- circumflex, and
- LAD
Veins
- Small cardiac,
- anterior cardiac, and
- great cardiac veins (join together to make the cardiac sinus and dumps into the right atrium)
The right coronary artery supplies blood to the ?
4
The left coronary artery supplies blood to the ? 2
- right ventricle, the
- right atrium, and
- the SA (sinoatrial) and
- AV (atrioventricular) nodes,
- left ventricle and
- left atrium
When does does cornary circlaiton deliver blood to the heart?
relaxation/diastole
DURING WHAT PERIOD OF THE CARDIAC CYCLE DO THE CORONARY ARTERIES RECEIVE PERFUSION?
diastole
What is angina pectoris?
What does this cause?
–Thoracic pain caused by a fleeting deficiency in blood delivery to the myocardium
–Cells are weakened
Describe Myocardial infarction (heart attack)?
2
- -Prolonged coronary blockage
- -Areas of cell death are repaired with noncontractile scar tissue
Infarction is different from ischemia how?
sudden and not going away. Killing heart cells until you do an itervention and perfuse again
ischemia can leave and be relieved on its own
- Which side of the heart acts as the pulmonary pump?
- Which side of the heart acts as the systemic pump?
- Which ventricle is larger?
- Which system is a high pressure system?
- Name two main branches of the RCA?
- right
- left
- left
- systemic
- PDA and marginal
What are the different AV heart valves and what is their purpose?
What anchor AV valve cusps to papillary muscles?
When pressure increases and blood fills in what happens to the valves?
Atrioventricular (AV) valves Prevent backflow into the atria when ventricles contract Tricuspid valve (right) Mitral valve (left)
Chordae tendinae
the valves close
Intraventricluar pressure increases and look to shoot out the blood!
What are the semilunar valves and what is their function?
Prevent backflow into the ventricles when ventricles relax
Aortic semilunar valve
Pulmonary semilunar valve
What causes the opening of the AV valves?
What causes them to close?
AV valves open; atrial pressure greater than ventricular pressure
AV valves closed; atrial pressure less than ventricular pressure
Fibrous insulator exists between atrium and ventricle. Why?
provides electrical insulation
46
46
Describe cardiac muscle?
3
- Gap junctions (for conduction)
- Actin and mysoin filaments
- low resistance intercalated disks
- Depolarization of the heart is ______ and ______?
- About __% of cardiac cells have automaticity— (are self-excitable)
- What do gap junctions ensure?
- Describe the refractory period of the cardiac muscle?
- rhythmic and spontaneous
- 1
- the heart contracts as a unit
- Long absolute refractory period (250 ms)
Similarities of Cardiac and Skeletal Muscle
- WHich are triggered by action potentials that sweep across cell membranes?
1% of cardiac fibers are autorhythmic
- The bulk of heart muscle, however, is composed of _______ ______ _____responsible for the heart’s pumping action
- In these cells, the sequence of events leading to contraction is similar to that in ________ ______ ____?
- Both
- contractile muscle fibers
- skeletal muscle fibers
Cardiac (short and interconnected, one or two nuclei)
What happens during systole?
What happens during diastole?
On the EKG what is the:
Pwave?
QRS?
T wave?
Systole – ventricular muscle stimulated by action potential and contracting
Diastole – ventricular muscle reestablishing Na+/K+/Ca++ gradient and is relaxing
EKG -
P-atrial wave
QRS - Ventricular wave T - ventricular repolarization
Volume overload to fibrosis what do you hear?
Heart failure what do you hear?
S4
S3
What is the intrinsic cardiac conduction system?
A network of noncontractile (autorhythmic) cells that initiate and distribute impulses to coordinate the depolarization and contraction of the heart
What are the parts of the cardiac conduction system?
4
- SA node
- AV node
- Bundle of HIS
- Bundle branch
Pathway of the heartbeat:
- Begins where?
- Then?
- Where does the impulse pause?
- Then?
- Then?
- Begins in the sinoatrial (S-A) node
- Internodal pathway to atrioventricular (A-V) node
- Impulse delayed in A-V node and bundle
- A-V bundle takes impulse into ventricles
- Left and right bundles of Purkinje fibers take impulses to all parts of ventricles
Why is the impulse delayed in the AV node?
(allows atria to contract before ventricles)
- What kind of cells have unstable resting potentials (pacemaker potentials or prepotenials)?
- Why?
- When the potenial reaches threshold what happens?
- This causes?
- What does repolarization result from?
- Autorhythmic Cells
- due to open slow Na+ channels
- At threshold, Ca2+ channels open
- Explosive Ca2+ influx produces the rising phase of the action potential
- Repolarization results from inactivation of Ca2+ channels and opening of voltage-gated K+ channels
Pacemaker potential: This slow depolarization is due to both opening of \_\_\_ channels and closing of \_\_\_ channels. Notice that the membrane potential is never a flat line.
Na+
K+
Depolarization The action potential begins when the pacemaker potential \_\_\_\_\_\_ \_\_\_\_\_\_\_. Depolarization is due to \_\_\_\_ influx through \_\_\_\_ channels.
Reaches threshold
Ca2+
Ca2+
Repolarization is due to \_\_\_ channels inactivating and \_\_\_ channels opening. This allows \_\_\_ efflux, which brings the membrane potential back to its most \_\_\_\_\_\_\_ voltage.
Ca2+
K+
K+
negative
- What is the SA node?
- What does it act as and why?
- When membrane potential reaches -40 mV what happens?
- After 100-150 msec _____ channels close and ___ channels open more thus returning membrane potential to -55mV
- Specialized cardiac muscle connected to atrial muscle
- Acts as pacemaker because membrane leaks Na+ and membrane potential is -55 to -60mV
- When membrane potential reaches -40 mV, slow Ca++ channels open causing action potential
4.
Ca++
K+
What actually causes the depolarization/contraction of the heart?
Ca+ channels open
Heart Physiology: Sequence of Excitation
First? Second? Third? Fourth? Fifth?
- Sinoatrial (SA) node (pacemaker)
- Atrioventricular (AV) node
- Atrioventricular (AV) bundle (bundle of His)
- Right and left bundle branches
- Purkinje fibers
SA node generates impulses at what rate?
________ faster than any other part of the myocardium
SA is mediated by who?
75 times/minute
Depolarizes
Parasympathetic system (otherwise normal would be 100 or over)
Describe the structure of the AV node? 2
Delays impulses how much?
Depolarizes how many times per minute without the SA node influence?
- Smaller diameter fibers;
- fewer gap junctions (so the impulses move slower)
Delays impulses approximately 0.1 second
Depolarizes 50 times per minute in absence of SA node input
What is the only electrical connection between the atria and the ventricles?
Atrioventricular (AV) bundle (bundle of His)
Only electrical connection between the atria and ventricles
Whats the purkinje system?
Describe its conduction and why?
Fibers lead from A-V node through A-V bundle into Ventricles
Fast conduction; many gap junctions at intercalated disks
What are the Right and left bundle branches?
Two pathways in the interventricular septum that carry the impulses toward the apex of the heart
Purkinje fibers complete the conduction pathway into the _____ and __________ _____?
AV bundle and Purkinje fibers depolarize only __ times per minute in absence of AV node input
apex and ventricular walls
30
Describe Homeostatic Imbalances?
Defects in the intrinsic conduction system
Defects in the intrinsic conduction system may result in what?
3
- Arrhythmias: irregular heart rhythms
- Uncoordinated atrial and ventricular contractions
- Fibrillation: rapid, irregular contractions; useless for pumping blood
Defective SA node may result in
what?
2
- Ectopic focus: abnormal pacemaker takes over
2. If AV node takes over, there will be a junctional rhythm (40–60 bpm)
Defective AV node may result in what?
2
- Partial or total heart block
2. Few or no impulses from SA node reach the ventricles
Heartbeat is modified by what system?
autonomic nerve system
Where are the cardiac nerve centers located?
medulla oblingata
Cardioacceleratory center innervates what? 3
Cardioinhibitory center inhibits what and through what system?
Cardioacceleratory center innervates
- SA and AV nodes,
- heart muscle, and
- coronary arteries through sympathetic neurons
Cardioinhibitory center inhibits
1. SA and AV nodes through parasympathetic fibers in the vagus nerves
What nerve decreases heart rate?
What nerve increases heart rate?
- The vagus nerve
(parasympathetic)
decreases heart rate. - Sympathetic cardiac
nerves increase heart rate
and force of contraction.
What is an EKG?
What are the three waves and describe them?
a composite of all the action potentials generated by nodal and contractile cells at a given time
P wave: depolarization of SA node
QRS complex: ventricular depolarization
T wave: ventricular repolarization
Why doesnt the p wave repolarization show up?
hidden in the QRS
What happens in a junctional rhythm?
The SA node is nonfunctional, P waves are absent, and heart is paced by the AV node at 40 - 60 beats/min.
What is a Second-degree heart block?
Some P waves are not conducted through the AV node; hence more P than QRS waves are seen. In this tracing, the ratio of P waves to QRS waves is mostly 2:1.
What is ventricular fibrillation?
These chaotic, grossly irregular ECG deflections are seen in acute heart attack and electrical shock.
What is the Lubb heart sound?
When does it occur?
first heart sound (S1)
A-V valves closing
occurs during ventricular systole
What happens if you have a long QT what can happen?
go into torsades
What is the Dubb heart sound?
When does it occur?
second heart sound (S2)
pulmonary and aortic semilunar valves closing
occurs during ventricular diastole
First heart sound occurs when what happens and signifies what?
Second heart sound occurs when what happens and signifies what?
First sound occurs as AV (Tricuspid and Mitral) valves close and signifies beginning of systole
Second sound occurs when SL (Aortic and Pulmonic) valves close at the beginning of ventricular diastole
What are heart murmurs?
Heart murmurs: abnormal heart sounds most often indicative of valve problems
- Aortic valve is heard where?
- Pulmonary valve is heard where?
- Mitral valve is heard where?
- Tricuspid valve is heard where?
- Aortic valve sounds heard
in 2nd intercostal space at
right sternal margin - Pulmonary valve
sounds heard in 2nd
intercostal space at left
sternal margin
3. Mitral valve sounds heard over heart apex (in 5th intercostal space) in line with middle of clavicle
- Tricuspid valve sounds typically
heard in right sternal margin of
5th intercostal space
What is the definition of the cardiac cycle?
What is systole?
What is diastole?
all events associated with blood flow through the heart during one complete heartbeat
Systole—contraction
Diastole—relaxation
- What is the first phase of the cardiac cycle?
- When does it take place?
- What valves are open?
- What percent of the blood passively flows into the ventricles?
- What delivers the remaining percentage?
- What is end diastolic volume?
- Ventricular filling—
- takes place in mid-to-late diastole
- AV (tricuspid and mitral) valves are open
- 80% of blood passively flows into ventricles
- Atrial systole occurs, delivering the remaining 20%
- End diastolic volume (EDV): volume of blood in each ventricle at the end of ventricular diastole
- What is the second phase of the cardiac cycle?
- What do the atria do here?
Ventricles? - What causes the closing of the AV valves?
- What contraction phase is this?
- What happens in the ejection phase?
- What is end systolic volume?
- Ventricular systole
- Atria relax and ventricles begin to contract
- Rising ventricular pressure results in closing of AV valves
- Isovolumetric contraction phase (all valves are closed)
- In ejection phase, ventricular pressure exceeds pressure in the large arteries, forcing the SL valves open
- End systolic volume (ESV): volume of blood remaining in each ventricle
- What is the third phase of the cardiac cycle?
- What do the ventricles do?
- What closes the SL valves and what does this cause?
- Isovolumetric relaxation occurs in early diastole
- Ventricles relax
- Backflow of blood in aorta and pulmonary trunk closes SL valves and causes dicrotic notch (brief rise in aortic pressure)
SV =
CArdiac output =
EDV - ESV
SV(stroke volume) X HR
- The second heart sound is associated with the closing of which heart valves?
- If the MV were insufficient, would you expect to hear the murmur during ventricular systole or diastole?
- During the cardiac cycle, there are two periods when all four valves are closed. Name these two periods.
- SL valves closing
- systole (AV valve should we closed during systole)
- -Isovolumetric contraction phase- beginning of systole (ventricle depolarization) and
- -Isovolumetric relaxation -beginning of diastole (ventricle repolarization)
What is cardiac output?
Volume of blood pumped by each ventricle in one minute
What is stroke volume?
volume of blood pumped out by a ventricle with each beat
- At rest what is our normal cardiac output?
- Maximal CO is ____ times resting CO in nonathletic people
- Maximal CO may reach ___ L/min in trained athletes
- What is the Cardiac reserve?
- CO (ml/min) = HR (75 beats/min) × SV (70 ml/beat) = 5.25 L/min
- 4–5
- 35
- difference between resting and maximal CO
Three main factors affect SV?
Preload (EDV)
Contractility (ESV)
Afterload (ESV)
- Ejection fraction is what?
- Whats normal?
- How can we determine this? 2
- measurement of ventricular systolic function
- normal is 60%
- echocardiogram
- cardiac catheterization
What is the definition of preload?
Preload: degree of stretch of cardiac muscle cells before they contract (Frank-Starling law of the heart)
- What kind of relationship does cardiac muscle exhibit?
- What length are cardiac cells at rest?
- What increases venous return?
- What does increased venous return do?2
- Cardiac muscle exhibits a length-tension relationship
- At rest, cardiac muscle cells are shorter than optimal length
- Slow heartbeat and exercise increase venous return
- Increased venous return
- -distends (stretches) the ventricles and
- -increases contraction force
- Pressure-volume relationships are critical for understanding the pathophysiologic mechanisms of diseases that affect the entire ventricular chamber function, such as ______ _______ and_______ abnormalities.
- Increase pre-load ______ SV
- Increase after-load _______ SV
- Increasing contractile state shifts the isovolemic pressure-volume relationship ______ (_______ ESV) _______ SV
- heart failure
valvular - increases
- decreases
- leftward
decreasing
increasing
What is contractility?
What is it independant of? 2
contractile strength at a given muscle length,
independent of muscle stretch and EDV
Positive inotropic agents _______contractility. How? 2
Negative inotropic agents _______ contractility
When would this occur? 3
Increase
1. Increased Ca2+ influx due to
sympathetic stimulation
2. Hormones (thyroxine, glucagon, and epinephrine)
decrease
- Acidosis
- Increased extracellular K+
- Calcium channel blockers
Decreased contractility affects volume and pressure how?
Increased contractiility affects volume and pressure how?
Increases them
Decreases them
Positive chronotropic factors ______ heart rate
Negative chronotropic factors ______ heart rate
increase
decrease
Sympathetic nervous system is activated by emotional or physical stressors:
Norepinephrine causes the pacemaker to fire more______ (and at the same time_______ contractility)
rapidly
increases
Sympathetic Effects on Heart rate
4
- Releases norepinephrine at sympathetic ending
- Causes increased sinus node discharge
- Increases rate of conduction of impulse
- Increases force of contraction in atria and ventricles
Sympathetic activation increases pacemaker rate by
decreasing ___ perm and increasing slow inward___ and ___?
K+
Ca++
Na+
Does parasympathetic affect contractility?
no
Parasympathetic nervous system opposes sympathetic effects. How?
The heart at rest exhibits vagal tone. Why?
Acetylcholine hyperpolarizes pacemaker cells by opening K+ channels
parasympathetic response
Parasympathetic (vagal) nerves, which release ______ at their endings, innervate what? 2
What does this cause and why?
acetylcholine
- S-A node and
- A-V junctional fibers proximal to A-V node.
Causes hyperpolarization because of increased K+ permeability in response to acetylcholine.
Hyperpolarization due to increased K+ permeability in response to acetylcholine causes what?
Which leads to what??
decreased transmission of impulses maybe temporarily stopping heart rate.
Ventricular escape occurs
- What is the atrial (brain bridge) reflex?
- What stimulates the SA node?
- What does this also stimulate?
- a sympathetic reflex initiated by increased venous return
- Stretch of the atrial walls stimulates the SA node
- Also stimulates atrial stretch receptors activating sympathetic reflexes
Sympathetic stimulation causes an increase in what two things?
Parasympathetic does the opposite
We can tachycardia decrease cardiac output?
HR+ contractility
with HR = 180-200 and C.O. = 15-20 L/min.
because there is not enough time for heart to fill during diastole.
Epinehphrine from where enhances what two things?
Thyroxine increases what?
And enchances what?
Epinephrine from adrenal medulla enhances heart rate and contractility
Thyroxine increases heart rate and enhances the effects of norepinephrine and epinephrine
What is the common sign of low contractility?
leg edema
CCB
Other Factors that Influence Heart Rate
4
Age
Gender (females have faster HR)
Exercise
Body temperature
Bradycardia: heart rate slower than 60 bpm. What could this result in?
May result in grossly inadequate blood circulation
HOw do we Assess Perfusion at the Bedside?
3
- Cold extremities indicate reduced perfusion so feel the feet
- Poor Urine Output also indicates poor tissue perfusion
You now have 2 ways to determine if the patient is adequately perfusing or to see if the heart is doing its job or mission.
- Don’t forget the Blood pressure
