Cardiac Terms & Definitions Study Set for Medicine

What part of the heart makes up the inferior surface?

right ventricle, lies on the diaphargm

What direction is the apex tipped?

left

pericardium

double walled sac surrounding the heart and root of the great vessels

How much fluid does the pericardium normally contain?

10-25ml

What are the outer and inner layers of the pericardial sac called?

outer parietal and inner visceral

Anterior Interventricular Artery

lies in the anterior interventricular sulcus, separates the ventricles only not the atria (one on the posterior as well)

3 structures the RA receives blood from

IVC, SVC, coronary sinus

Ventricles

thicker with a rough surface r/t papillary muscles and chordae tendineae

chordae tendineae

prevent backward flow of blood through valves

Atrial Kick

provides 20-30% of LVEDV, small portion, healthy people don't rely on this for CO

Part of the heart most vulnerable to ischemia

Subendocardium, flow during systole stops completely r/t compression of left coronary artery

3 layers of the heart

endocardium (inner), myocardium (middle muscular), epicardium (outer attached to visceral pericardial membrane)

Valvular Insufficiency

valve does not close perfectly

Valvular Stenosis

valve does not open perfectly

Atrioventricular valves

tricuspid and mitral, opening and closing is a passive process determined by pressure gradients between the atria and ventricles

Semilunar Valves

pulmonic and aortic, each has 3 cusps with no chordae tendineae

sinus of Valsalva

dilation above the aortic valve allowing it to open without occluding the coronary arteries

Valve Area in mild, moderate, and severe aortic stenosis

mild 1.5, moderate 1-1.5, severe <1

AV vs. SL valves

-AV valves are lower pressure with a softer closer, SL valves high pressure with a harsh snap closure

-only AV valves have chordae tendineae

-AV valves are larger while SL valves are smaller

APETM

-all people enjoy times magazine

-aortic, pulmonic, Erb's, tricuspid, mitral

Aortic Auscultation

right side, 2nd intercostal space

Pulmonic Auscultation

left side, 2nd intercostal space

Erb's Point

-use this to listen to all sounds at once

-left sternal border, 3rd intercostal space

Tricuspid Auscultation

left lower sternal border, 4th intercostal space

Mitral Auscultation

apex, 5th intercostal space midclavicular line

Which is anterior the pulmonary trunk or the aorta?

pulmonary trunk

2 branches of the left coronary artery

circumflex and the left anterior descending

2 branches of the right coronary artery

marginal and the posterior interventricular branch

LAD blood supply (5)

1. anterior 2/3 of the interventricular septum

2. right and left bundle branches

3. anterior and posterior papillary muscles of the MV

4. anterior lateral and apical walls of the LV

5. collateral circulation to anterior wall of the RV

What is the most devastating vessel to be occluded and why?

LAD, septal damage disrupts the conduction system, damage to MV papillary muscles leads to regurg, and LV wall damage decreases contractility

Circumflex blood supply (5)

1. left atrial wall

2. posterior and lateral LV

3. anterolateral papillary muscle

4. AV node in 10% of the population

5. SA node in 40-45% of the population

Right Coronary artery blood supply (5)

1. SA and AV nodes

2. RA and RV

3. posterior 1/3 of interventricular septum

4. posterior fascicle left bundle branch

5. interatrial septum

What drains the posterior interventricular branch of the RCA?

middle cardiac

What are the two most common areas of occlusion?

1. LAD, less angle compared to right

2. RCA prior to branching, larger size

Where does blood from the LAD drain?

great cardiac

Where does blood from the RCA drain?

small cardiac

Where does blood from the marginal branch drain?

anterior cardiac

What part of the medulla handles sensory information?

dorsal medulla

What part of the medulla is responsible for motor output?

ventral medulla

Baroreceptors

-found in aorta and the common carotids

-sense pressure changes and communicate with the medulla

Chemoreceptors

-central are in the brain and are directly stimulated by hydrogen

-peripheral are in the carotid and aortic bodies next to the baroreceptors and sense CO2, O2, and hydrogen

-communicate with the medulla

Proprioceptors

monitor movements/detect posture changes, communicate this information with the medulla

What are the 2 efferent structures the medulla uses to effect CV function?

1. cardiac accelerator nerves/sympathetic, release nor-epi

2. vagus (CN X, parasympathetic, release acetylcholine)

Effects of sympathetic output from the medulla

-increased rate of depolarization of the SA and AV node increasing HR

-increased contractility

-increased SV

Effects of parasympathetic output from the medulla via vagus nerve

decreased rate of depolarization of the SA and AV node decreasing HR only, no direct decrease to contractility

Acetylcholine

-major neurotransmitter of the PNS

-binds to muscarinic receptors decreasing the rate of firing from the SA node and slowing conduction through the AV node

-increased permeability to K, K leaks out leading to hyperpolarization

Sensory innervation of the heart

-receptors in the wall of the heart, coronary arteries, and pericardium synapse with second order neurons in the posterior gray column of the spinal cord

-ascend via the ventral spinothalamic tract and terminate in the posterolateral nucleus of the thalamus

-then to hypothalamus

*DO NOT GO TO THE CORTEX

What factors determine coronary blood flow?

-change in pressure/gradient and resistance

-increased gradient=increased flow

-increased resistance=decreased flow (inverse relationship)

% CO designated to coronary blood flow at rest

4-5%, 225ml/min

Intrinsic factors affecting coronary tone

arrangement of the vessels themselves and perfusion pressure

Extrinsic factors affecting coronary tone

compression, metabolic demand, SNS stimulation, catecholamines, angiontensin II

5 factors determining myocardial O2 supply

1. arterial blood content of PaO2/PCO2

2. DBP (increased DBP increases O2 supply)

3. length of diastole as determined by HR (tachy less O2 supply)

4. O2 extraction

5. Coronary blood flow

4 factors determining myocardial O2 demand

1. preload

2. afterload

3. contractility

4. HR

*if any on these increase, O2 demand increases

What is the most important determinant of myocardial oxygen demand?

heart rate especially in those with CAD

Effect of beta blockers on myocardial oxygen demand

decreases heart rate and contractility therefore increasing supply and decreasing demand

At rest, how much oxygen does the heart extract from the blood supplied to it?

65-70%, only way to increase O2 delivery during times of greater demand like exercise is to increase supply, coronary flow can increase by 3-4x

What substances does the myocardium release in response to decrease O2 delivery? (5)

-adenosine

-adenosine phosphate compounds

-K, H, CO2

-bradykinin

-prostaglandins

*all of these vasodilate

What is the primary substance the myocardium releases in response to decreased O2 delivery?

adenosine

MVo2

myocardial oxygen consumption

Determinants of myocardial oxygen consumption (4)

-contractility

-myocardial wall tension/preload

-HR

-afterload (MAP)

Normal equation for coronary perfusion pressure and normal value

CPP=DBP-LVEDP

60-70

Normal DBP

70-80

Normal LVEDP

10mmHg

Equation for CPP once coronaries are maximally dilated

CPP=MAP-RAP

What vasodilators have been associated with coronary steal?

nitroglycerin and sevo

Cardiac Ouput

volume of blood ejected from the heart per minute, clopse to total blood volume

CO=HRxSV

Normal SV

60-70ml

EF equation

EF=(SV/EDV)x100

Normal >60%

Normal EDV

120-130ml

What is the primary measurement of afterload?

SVR, problem with this is that ventricular wall tension/hypertrophy is not considered

Frank Starling Law

more the heart fills the greater the force of contraction, proportional to EDV

Normal SVR

800-1500

Anesthetic agent effect on HR and contractility versus calciums effect

-anesthetics decrease contractility and HR

-calcium increases contractility and HR

Which is the only system affecting vasomotor tone?

SNS, NOT PNS

Reflexes altering CO (7)

valsalva maneuver, baroreceptor reflex, oculocardiac reflex, celiac reflex, bainbridge/atrial stretch reflex, cushing reflex, chemoreceptor reflex

Valsalva manuever

-forced expiration against a closed glottis

-mediated through baroreceptors that when stimulated inhibits the vasomotor center in the medulla

-also inhibits SNS and stimulates PNS

-decreased HR, contractility, blood pressure, and vasodilation

-increase in intrathoracic pressure further decreases venous return and CO

Where are baroreceptors located?

bifurcation of the internal/external carotid arteries (carotid sinus) and the aortic arch

Nerves involved in the valsalva maneuver (3)

-Hering's Nerve

-glossopharyngeal (carotid sinus)

-vagus (aortic arch)

Baroreceptor reflex

-respond to alterations in arterial BP via the same pathway as the valsalva maneuver

-decrease in BP stimulates increased SNS tone/vasoconstriction, opposite response to increased BP

*volatiles can inhibit this reflex

Oculocardiac Reflex

-traction on medial rectus, conjunctiva, or other orbital structures causes hypotension and decreased HR

-other causes include a retrobulbar block, ocular trauma, or pressure after enucleation

-efferent branch is via the vagus nerve

Treatment of oculocardiac reflex

remove offending stimulus, retrobulbar block, anticholinergics (atropine/glycopyrrolate)

Celiac Reflex

-traction on abdominal structures stimulating the vagus nerve or pneumoperitoneum

-bradycardia, hypotension, and apnea

-remove offending stimulus

Bainbridge Reflex

-also known as the atrial stretch reflex as it is caused by an increase in volume in the RA causing SNS stimulation

-stretch receptors also found at the junction of the vena cava and the pulmonary veins

-SA node can increase HR 10-15% preventing sequestration of blood in the veins, atria, and pulmonary bed

-ADH decreased and ANP is increased promoting diuresis

Cushing Reflex

-response to CNS ischemia caused by increase in ICP, ICP>MAP

-vasomotor center triggers SNS response and vasoconstriction in an attempt to maintain CPP

Cushing's Triad

late sign of increased ICP prior to herniation, hypertension, bradycardia, and respiratory irregularities

Chemoreceptor Reflex

central chemoreceptors responding to increased hydrogen and peripheral chemoreceptors responding to increased CO2/decreased O2 stimulate an increased in MV, SNS output, and blood pressure

*can be inhibited by volatiles much like baroreceptors

Peripheral chemoreceptors

bifurcation of internal/external carotids and aortic arch

Central chemoreceptors

below the ventral surface of the medulla

Constriction of which vessels causes the greatest increase in SVR?

arterioles

Arterial vs. Venous fibers

-arteries have elastic tissue, smooth muscles, and fibrous tissue

-veins have the same things just much thinner, don't contract or dilate but can be stretched out

% blood in arteries versus veins

arteries 20% veins 60% (reservoir/distensible)

Tunica interna

endothelium, basement membrane, and internal elastic lamina

Tunica media

smooth muscle and external elastic lamina

Tunica externa

outer layer of vessels, also known as the adventitia

Does inhalation or exhalation encourage the return of blood back to the RA?

inhalation

Two types of arteries

-conducting or elastic arteries have more elastic fibers, stretch and then recoil to propel blood forward (i.e. aorta and 3 major branches)

-distributing or muscular have more smooth muscle (i.e. axillary, femoral, iliac)

Branches of the ASCENDING aorta?

right and left coronary arteries

Branches of the transverse/arch of the aorta?

brachiocephalic trunk, left common carotid, left subclavian

Branches of the brachiocephalic trunk?

right common carotid and the right subclavian

Branches of the bilateral subclavian arteries?

vertebral arteries and the axially arteries