cardiovascular/PVD

cardiac output

each time the heart beats, a volume of blood is ejected

cardiac output equation

CO \= HR x SV

what is cardiac output?

the amount of blood that the heart pumps out of left ventricle each minute

why is cardiac output diminished in heart failure?

the left ventricle is weakened and cannot adequately pump blood out of the chamber

what is stroke volume the difference between?

end diastolic volume - end systolic volume

end diastolic volume (EDV)

volume of blood at the end of relaxation

end systolic volume (ESV)

residual volume of blood remaining in the ventricle after ejection

what happens when something alters EDV or ESV?

stroke volume will change and this cardiac output will be changed as well

what three major factors influence stroke volume?

1. preload
2. afterload
3. contractility

preload

volume of blood in the heart at the end of diastole

afterload

force opposing ejection of the blood from the ventricle

contracility

contractile capabilities of the heart

preload definition

- stretch of cardiac muscle cells before contraction
- related to the chamber volume just prior to contraction

lower preload leads to lower what?

stroke volume

frank-starling law

- an increase in resting muscle fiber length results in greater muscle tension
- heart has the ability to change its force of contraction (and SV) in response to changes in venous return

starling's capillary forces

At every capillary-cell interface, there are three fluid compartments: intracellular, extracellular, and interstitial.

where is intracellular fluid found?

inside cells

where is interstitial fluid found?

surrounding cells

where is extracellular fluid found?

inside the capillary

hydrostatic pressure

a force that attempts to push fluid out of the capillary pores and into the interstitial and intracellular spaces

what particles within blood exert oncotic/osmotic pressure?

albumin, sodium and glucose

oncotic (osmotic) pressure

a force that attempts to pull fluid from the interstitial and intracellular spaces into the capillary

starling's law of capillary forces

Oncotic pressure forces and hydrostatic pressure forces oppose each other at every capillary membrane and attempt to balance each other out

afterload definiton

resistance that must be overcome in order to eject blood from the chamber

what is left ventricular afterload primarily determined by?

aortic blood pressure

what does an increase in afterload lead to?

decrease in stroke volume unless the heart compensates

contractility definition

contractile force of the heart muscle cells

what is contractility is primarily determined by?

the amount of free calcium within the myocardial

what happens with increased contractility?

increases stroke volume by causing a greater % of the volume to be ejected

Blood flow through the heart

R. atrium (deoxygenated), R. ventricle, pulmonary arteries, lungs, pulmonary veins (now oxygenated), L. atrium, L ventricle, aorta, body

what do cardiac muscles need a continuous supply of?

oxygen and nutrients

what do coronary arteries supply?

blood to the heart muscle

layers of the heart

pericardium, myocardium, endocardium

mycocardium

- cardiac muscle layer
- produces contractions

Why is the myocardium of the left ventricle 2-3x thicker than the myocardium of the right ventricle?

higher pressures are needed to eject blood into the arteries

endocardium

- layer of epithelial cells that line the heart chambers and valves
- a smooth surface on which blood can slide, preventing clotting
- continuous with the endothelium of vascular cells

pericardium

two layers that envelop the heart like a sac

visceral pericardium

inner layer that is attached directly to the myocardium's surface

parietal pericardium

outer layer that forms a sac around the outside of the heart

pericardial space

space between the visceral and parietal pericardial layers

what is pericardial space filled with?

10-30 mL serous fluid that lubricates surfaces and reduces friction

what controls the direction of blood flow between the atria and ventricles?

two atrioventricular valves

mitral valves

directs blood flow from left atrium to the left ventricle

tricuspid valve

directs blood flow from right atrium to right ventricle

chordae tendinae and papillary muscles

2 structures which hold AV valves closed so blood won't backflow

two semilunar valves

- pulmonary and aortic
- located at the outflow points of the ventricles
- thicker and not supported by fibrous cords

pulmonic valve

directs blood flow between the right ventricle and pulmonary artery

aortic valve

directs blood flow between the left ventricle and aorta

what are problems with the heart?

- electrical (conduction)
- plumbing (artery blockage, spasm or valve issues)
- pump (heart muscle)

what is a stable plaque characterized by?

- thick fibrous cap
- small lipid core

what is the primary etiology of coronary heart disease?

artherosclerosis

what are non-modifiable risk factors for CAD?

- age
- family history
- gender
- race

what are modifiable risk factors for CAD?

- hypertension
- tobacco
- diabetes
- inactivity
- diet
- hyperlipidemia
- depression/stress

what cause endothelial dysfunction?

- uncontrolled diabetes mellitus
- hypertension
- hypercholesterolemia
- smoking

what happens when there is endothelial dysfunction?

plaque starts to build up

what is stable angina?

predictable occurrence of angina r/t transient myocardial ischemia

why does stable angina occur?

with exertion or emotional upset

how long does chest discomfort lasts in classic angina pectoris?

2-5 minutes and max 10-15 minutes

clinical features of classic angina pectoris

- pt. is motionless
- hunched over with closed fist across chest
- anxiety
- sweating
- chest tightness

vitals signs in classic angina pectoris

- pulse rapid and bounding
- BP is elevated
- some dyspnea

what are atypical signs of angina in women?

- discomfort (hot, burning, tenderness in epigastric area)
- location : not always in chest
- indigestion, heart burn, nausea, fatigue, lightheadedness, dyspnea

what does unstable plaque look like?

- large lipid core
- active inflammation
- thin fibrous cap

how are 3 goals of stable angina pharmacotherapy?

- relieve pain
- reduce risk factors
- improve morbidity & mortality

how do you relieve pain for stable angina?

- nitrates
- beta blockers
- calcium channel blockers
- ranolazine

how do you reduce risk factors for stable angina?

- lipid lowering drugs (statins)
- aspirin or clopidogrel (plavix)

how do you improve morbidity & mortality?

ACE inhibitor or ARB

what is the mechanism of pain relief of nitrates for stable angina?

dilates veins which decreases preload

what is the mechanism of pain relief of beta blockers for stable angina?

decreases heart rate & contractility

what is the mechanism of pain relief of calcium channel blockers for stable angina?

- dilates arterioles, which decreases afterload
- decrease heart rate & contractility

what is the mechanism of pain relief of ranolazine for stable angina?

helps the myocardium generate energy more efficiently

nitroglycerin MOA

- dilates veins
- decreases preload

nitroglycerin adverse effects

- related to vasodilation: headache, hypotension, increase HR
- tolerance

how should nitroglycerin be taken?

take one tablet at 5 minute intervals up to 3 tablets until pain is relieved

nitroglycerin guide lines

if chest pain has not improved or it has worsened 5 minutes after taking the first nitro, call 911

why is it important to take nitroglycerin sitting down?

it reduces BP so to prevent from passing out

ranolazine MOA

unknown, possibly helps myocardium use energy more efficiently

ranolazine warnings

- prolong QT interval
- acute renal failure
- liver cirrhosis

ranolazine adverse effects

- headache
- dizziness
- nausea and constipation

ranolazine drug interactions

Do not use with CYP inhibitors or inducers

what is heart failure?

when the heart is insufficient to pump blood forward and can't meet body's demand

what is weakened in heart failure?

myocardium

what are factors affecting heart rate?

- autonomic innervation
- hormones,
- fitness levels
- age

what are factors affecting stroke volume?

- heart size
- fitness levels
- gender
- contractility
- duration of contration
- preload
- afterload

what factors determine cardiac output?

heart rate and stroke volume

what are major causes of heart failure?

- repeated ischemic episodes (ischemic cardiomyopathy)
- myocardial infarction +/- papillary muscle rupture
- chronic HTN
- COPD (RVF)
- dysrhythmias
- valve disorders; mitral insufficiency; aortic stenosis
- PE (RVF)

what are more causes of heart failure?

- hypertension
- diabetes
- within 6 months of MI
- men & postemenopausal women have same risk of CV disease

development of heart failure

- volume overload
- impaired ventricular
- weakened ventricular muscle
- decreased ventricular contractile function

what are major risk factors for heart failure?

- age : 65+
- ethnicity : african americans higher risk
- family history/genetics
- diabetes
- ischemic heart disease
- obesity
- HTN
- smoking & sedentary

what are other risk factors of heart failure?

- medications
- COPD
- sleep apnea
- congenital heart defects
- viruses
- alcohol/drug abuse
- kidney conditions

why can sleep apnea cause heart failure?

can cause hypoxia & increase risk of rhythm disturbances

why can kidney conditions cause heart failure?

excess blood volume, edema, HTN, and accumulation of nitrogenous waste can weaken the heart

heart failure classifications

- right vs left sided failure
- systolic vs diastolic failure

what symptoms are apparent with left sided HF?

- SOB
- dyspnea
- cough
- crackles
- wheezing
- orthopnea
- tachycardia
- cyanosis

what symptoms are apparent with right sided HF?

- fatigue
- increase peripheral venous pressure
- enlarged liver & spleen
- distended jugular veins
- weight gain
- edema

what happens with left sided heart failure?

blood backs up into the lungs

what happens with right sided heart failure?

blood backs up into the body

systolic heart failure

- impaired contraction
- ineffectively pumping blood out to body

diastolic heart failure

difficulty relaxing & filling with blood

what is chronic heart failure?

long term condition in which the heart's ability to pump blood effectively is comprised

what is acute heart failure?

a sudden and severe worsening of heart function that occurs over a short period of time, usually within hours to day