Clinical Monitoring Cardiac - Exam 1

Label 1-13

1-     Right atrium

2-     Left atrium

3-     Superior Vena Cava

4-     Aorta

5-     Pulmonary artery

6-     Pulmonary veins

7-     Mitral valve

8-     Aortic Valve

9-     Left ventricle

10-  Right ventricle

11-  Inferior vena cava

12-  Tricuspid valve

13-  Pulmonary valve

What are the chambers of the heart

• Right and left atrium

• Right and left ventricle

Which are semilunar valves

pulmonary and aortic valves

Which are AV valves

Atrioventricular valves

• tricuspid

• mitral

Structure of tricuspid valve

• 3 leaflets

• normal size 4-6cm²

Mitral valve structure

• 2 leaflets

• normal size= 4-5 cm²

Chordae Tendineae

fibrous cords that connect edges of valve to papillary muscle

Papillary muscle

muscular projections that arise from the inner surface of the ventricles

semilunar valves structure

three half-moon shaped leaflets attached to a fibrous ring

• normal size: 3-4 cm²

what constitutes aortic stenosis

<2.0 cm²

Coronary Ostia

small opening of coronary artery

Fibrous Pericardium

outermost, tough, dense connective tissue

• Anchors the heart to the great vessels, diaphragm, and sternum

• Helps to limit excessive cardiac distention

Serous Pericardium

thin, smooth membrane - made up of two layers

Parietal layer

lines and is fused to the inner surface of the fibrous pericardium

Visceral layer

also called the epicardium; directly covers the heart

pericardial cavity/sac

lies between the parietal and visceral layers; contains a small amount of fluid, reduces friction

Myocardium

muscular, middle layer of the heart → has both contractile and conduction properties

Endocardium

serous membrane that lines the inner surface of the heart and extends out to form the heart valves → similar to endothelial cells that line blood vessels

What is a sacromere

basic functional contractile unit of cardiac muscle

• contains actin and myosin filaments

• during contraction actin and myosin slide past one another → shortening the sarcomere and generating tension

Why is calcium important for contraction

1. Increase in intracellular Ca2+ initiates contraction

2. Binds to troponin which causes shape change and moves tropomyosin

3. Myosin binding site open for Actin-Myosin crossbridge

4. More intracellular calcium = longer/stronger contraction

What is the pulmonary capillary wedge pressure?

• It is an estimate of left atrial pressure

• Obtained by inflating a small balloon at the tip of a catheter placed in a branch of the pulmonary artery

Right atrium pressure

0-4 mmHg

Right ventricle pressure

25 systolic; 4 diastolic

Normal Pulmonary artery pressure

25 systolic, 10 diastolic

Left atrium pressure

4-12 mmHg

Left ventricle pressure

120 systolic, 10 diastolic

Aortic pressure

120 systolic, 80 diastolic

What are the 5 major steps of the cardiac cycle

1. isovolumetric relaxation

2. ventricular filling

3. arterial systole

4. isovolumetric ventricular contraction

5. ventricular ejection

Identify the nodes of the cardiac conduction system

a.      “Some Believe In Acting Badly Before Performing”

i.     Sinoatrial (SA) Node → upper part of RA, pacemaker

ii.     Bachmann Bundles → inner wall of LA, atrial conduction system

iii.     Intermodal Pathway → atrial wall, SA node – AV node

iv.     Atrioventricular Node → AV node delay, allows atria to empty/finish contraction before stimulating ventricles

v.     Bundle of His → passes through ventricular septum, transmits signals from AV node to ventricles

vi.     Right and Left bundle branches

vii.     Purkinje Fibers → provide synchronized contractions of the ventricles

How to find Cardiac Output + normal value

heart rate x stroke volume; normal value = 4-8 L/min

stroke volume

= End-diastolic volume - end-systolic volume

• determined by

  • preload - ventricular stretch

  • contractility - force of myocardial contraction

  • afterload - resistance/pressure must overcome

Frank Starling Law

• as stroke volume increases as the volume of ventricular filling (EDV) increases

• stretch of the myocardium, lining up of sarcomere, must be optimal alignment/overlap for proper contraction and stroke volume

Centric Hypertrophy

• Thickening of the myocardial wall; increase in the number of muscle layers

• occurs because of increased workload → need to push/contract against persistently high resistance

Eccentric (ventricular) hypertrophy

• Dilation of heart chamber → widens/lengthens

• Increased blood volume - stretch → increased wall tension

Atrial Natriuretic Peptide

• released from atria; stimulated by atrial stretch or increased volume

• promotes natriuresis and diuresis → offload of excess volume

• vasodilation

Decreases blood volume, preload, and vascular resistance

B-type Natriuretic Peptide

• released by the ventricular myocardium, stimulated by ventricular wall stretch and increased filling pressure

• BNP and NT-proBNP are biomarkers for cardiac wall stress

Decreases blood volume, preload, and vascular resistance

Nervous system control of myocardium

Sympathetic NS = flight or fight

• norepinephrine and epinephrin stimulate Beta 1 adrenergic receptors

• increase HR, AV conduction, myocardial contractility

• increased CO to meet metabolic need

Parasympathetic NS = rest and digest

• medicated by vagus nerve

• Acetylcholine stimulates M2 muscarinic receptors

• decreased SA node firing → decrease HR

• decrease AV nodal conduction

Arterial Pressure Waveform

a. As the arterial pressure wave transmits further away from the heart → systolic pressure increases and diastolic pressure decreases

i. Increases pulse pressure

ii. MAP declines

b.Systolic upstroke = sharp, rapid rise in pressure caused by left ventricular ejection

c. Dicrotic Notch = downward deflection/notch on the downstroke signifying aortic valve closure and the end of systole

How is CO to each organ determined

1. Demand, function, and metabolic needs of organs

2. Resistance across organs → individual vascular resistance makes it easier/harder to perfuse and exchange oxygen

What percentage of C.O. goes to the lungs

100% of CO from right heart

What percentage of CO goes to the digestive system

21%

What percentage of CO goes to the Kidneys

20%

What percentage of CO goes to the Skeletal muscle

15%

What percentage of CO goes to the brain

13%

What percentage of CO goes to the skin

9%

What percentage of CO goes to the liver

6%

What percentage of CO goes to the bone

5%

What percentage of CO goes to the heart muscle (coronary circulation)

3%

Right Coronary Artery pathway

travels between right atrium and ventricle

• Acute Marginal branches = supply the right ventricular wall

• Posterior descending artery, if dominant

Left main coronary artery

Short vessel from the left coronary sinus and ascending aorta

• left anterior descending

  • Diagonal branches - anterolateral LV

  • Septal perforators - anterior interventricular septum

• Left Circumflex

  • Obtuse marginal branches

• Ramous

Coronary dominance

Determined by which coronary artery gives rise to the posterior descending artery

• 85% right

• 8-10% left

• 5-10% codominant

Average diameter of coronary artery

3-5 mm

Law of Laplace

larger the vessel radius, larger wall tension required to withstand a given internal fluid pressure

• as radius increases vessels must generate more force to create the same internal pressure

Pascal’s Principle

pressure is transmitted equally in an enclosed static fluid

• push on a fluid anywhere in a enclosed system → pressure spreads evenly throughout system

Poiseuille’s principle

Flow is determined by the change in pressure, resistance, and the radius of the vessel to the fourth power

• The radius has a very strong influence on the flow

  • small changes to the radius has huge change to flow

  • double radius = increase flow by 16x

What governs fluid movement across a capillary membrane

1. Hydrostatic pressure - physical pressure exerted by capillaries → pushes fluid out of the capillary into the interstitium
   - going in high, 25-30 mmHg
   - going out low, 10-15 mmHg

2. Colloid Osmotic Pressure - attraction of protein molecules for water across membrane
   - proteins (75% albumin) act like a magnet pulling water back in

At the atrial end, high hydrostatic pressure pushes fluid out → venous end hydrostatic pressure drops COP allowed to pull more in

Syncope

Brief loss of consciousness caused by temporary cerebral hypoperfusion

• low CO, pulmonary embolism, arrhythmias, acute myocardial ischemia

Presyncope

lightheadedness or feeling faint

• lower O2 delivery - decreased energy

Palpitations

conscious awareness of one’s heartbeat

Bradycardia

slowed heart rate, below 60 BPM

tachycardia

fast heart rate, higher than 100 BPM

Stage 1 hypertension

systolic 130-139; diastolic 80-90

Stage 2 hypertension

systolic >140; diastolic >90

Stage 3 hypertension

systolic >180; diastolic >120

Arterial Pressure Measure Sites

• adult cardiac surgery: radial or femoral preferred

• pediatric cardiac surgery: dorsalis pedis

• carotid, branchial

Pulsus Alternans

regular alternation between strong and weak pulse amplitudes

• alternating stroke volume, may occur with LV dysfunction

Pulsus Paradoxus

Abnormal drop in systolic blood pressure during inspiration

• drop >10 mmHg

• may occur with cardiac tamponade, severe obstructive lung disease

Auscultation

• Listening to heart sounds, closure of heart valves

• S1 = closure of mitral and tricuspid valves → isovolumetric contraction

• S2 - closure of aortic and pulmonic valves → isovolumetric relaxation

Systolic murmur

when heart muscle contracts between S1 and S2

Diastolic murmur

when heart muscle relaxes between beats, after S2 and before S1

Cardiac Stress test: how, purpose

• uses a treadmill/exercise to put the heart under stress and measures heart rate/rhythm via EKG or ECHO

  • can be used to determine workload, blood flow, oxygenation, etc

Cardiac stress test for non-ambulatory patients

Give patients drugs that make the heart behave as if it’s been exercising

• regadenoson/lexiscan

• dobutamine

• adenosine

Why wouldn’t we perform a stress test

if patient is unstable

• acute MI

• severe hypertension

• unstable angina

• severe aortic stenosis

• heart failure

Coronary angiography/cardiac catheterization

invasive procedure that allows direct visualization of coronary anatomy

• presence and severity of coronary stenosis

• coronary blood flow

• intracardiac pressure

• hemodynamic

• possible interventions