Basic Cardiology Concepts

What is CO?

Heart rate x SV

What controls heart rate?

Sympathetic nervous system (IDK RW CHECK)

What can cause a low heart rate?

Sick sinus syndrome

3rd degree AV block

Excessive vagal tone

What affects stroke volume?

Preload

Afterload

What is preload?

Stretching pressure on the myocardium during diastole

What determines preload?

Volume delivered to ventricle

What does dehydration do to the heart?

Decreased preload, decreased SV, increase in HR

What does too much preload do?

Congestion (edema)

What controls preload long term?

RAAS

What does this tell you?

As pre-load increases, stroke volume will increase until it cannot anymore then congestion begins

How much of a diuretic do you want to give a patient with congestion?

Enough to eliminate congestion but not reduce pre-load

What is a side effect of too much diuretic?

Decreased pre-load leading to decreased CO and hypoxic kidneys

What can you do to combat excess preload?

Diuretics (get rid of fluid)

Venodilators (increase amount of blood veins can hold)

What is afterload?

Forces opposing ventricular contraction during systole

Factors that affect wall stress

What effects afterload?

Arterial blood pressure

Wall thickness (thinner the wall, the more wall stress)

Counter-productive consequences of RAAS/SNS

Secondary to other disease

What do you do if afterload is too high?

Arterial dilators (reduce BP)

Negative chronotropes like a beta blocker (improve relaxation time and helps the heart accommodate high afterload easier)

How do you calculate afterload (T)?

Systemic BP * radius of ventricle / 2 * wall thickness

What happens if we fail to compensate and get poor CO?

Anorexia, lethargy, weakness, syncope (more common if sudden decompensation)

How can you differentiate poor CO vs dehydration?

A dehydrated dog will eat

What stimulates the RAAS system?

Low Na, Cl

Arterial underfilling

SNS activation

Mechanoreceptors

What does the RAAS system do?

Vasoconstriction, increased Na resorption, aldosterone release, renal water retention, release of AVP, increase thirst

What can long term aldosterone cause?

Myocardial fibrosis and remodeling

If we have a dehydrated patient, but they are eating what does that tell you about CO?

It is good

Why is long term activation of RAAS bad?

It increases pre-load and afterload (pressure and volume overload)

What mechanoreceptors in the SNS sense underfilling?

Left ventricle

Carotid sinus

Aortic arch

Renal afferent arteriole

What does activation of the SNS do?

Increased contractility form B1

Tachycardia from B1 and B2

Arterial vasoconstriction from alpha 1s

What C/S can clue you into heart failure?

Coughing dog WITH tachycardia

Why does the atria love to dilate?

That is the only way they can compensate because they cannot contract

T/F atrial dilation lets you differentiate between pressure and volume overload?

False

What are the ways the ventricle can change?

Concentric or eccentric hypertrophy

What causes concentric hypertrophy?

Pressure overload

Increased systolic wall stress

Valvular stenosis, arterial hypertesion

What causes eccentric hypertrophy?

Volume overload

Increased diastolic wall stress

Mitral regurgitation, dilated cardiomyopathy, patent ductus venosus

What does left heart disease cause?

Pulmonary edema

What does right heart disease cause?

Ascites

What is unique about cats?

They can have left sided heart disease and pleural effusion and pulmonary edema

T/F blood flows from high to low pressure areas?

True

What is the most reliable way to measure systolic BP?

Mitral regurgitation jet

What is the best way to measure pulmonary artery pressure?

Tricuspid regurg jet

What is normal blood velecity?

5 m/s

How do you determine blood pressure from velocity?

Measure first from mitral regurg jet then do P=4V²

How can you determine if a patient has heart disease?

Asymptomatic with murmur or arrhythmia, breed prevalence, coughing, respiratory rate and or effort, syncope, weakness and or exercise intolerance, abdominal distension

If a little dog is coughing and is fat, do you think heart disease?

No, probably respiratory disease

What is syncope?

Fainting or passing out

Why is there inspiratory dyspnea with heart diseaes?

Lungs will be heavy and wet and struggle to expand

What does expiratory dyspnea indicate?

Probably respiratory disease (asthma in cats)

What does ascites indicate?

Disease on the right side of the heart of pericardium

What does cyanosis tell you?

Uncommon, but suggests a serious problem with oxygen exchange or delivery

Probably severe pulmonary edema if this is present

What is required for syanosis?

5g/dL of hemoglobin must be deoxygenated (very hard)

Why cant extremely anemic patients be cyanotic?

They do not have enough hemoglobin to become cyanotic

T/F you should always feel the femoral pulse when you auscultate the heart?

True

What do weak pulses tell you?

Poor CO

What does femoral pulse quality tell you?

Difference between systolic and diastolic pressures

What will aortic regurgitation tell feel like?

Diastolic runoff will cause a “water hammer” pulse

Where does a normal jugular pulse extend?

1/3 up the neck

What do right heart disease do to the jugular?

Jugular distension or big pulses

What does really loud crackles without overt dyspnea imply?

Primary airway disease like chronic bronchitis

What should you look for?

BCS, respiratory effort, abdominal distension, mm color and CRT, pulse quality and synchrony, presence of jugular pulses, listen to lungs and heart

What valves can you hear on the left side?

Mitral, aortic, and pulmonic

Where do you listen to the mitral valve?

Apex of the heart on the left side under the ribs

Where do you listen to the aortic and pulmonary valve?

Base of the heart above the ribs on the left side

Where do you listen to the tricuspid valve?

On the right sight at the costocartilage junction

How do you listen to the PDA?

Cranial and dorsal to the apex of the heart

Where do you listen to cats?

Left and right parasternal

What is the S1 sound?

The lub where mitral and tricuspid valve closes

Systole

Where is the S1 sound heard best?

Apex of the heart

What is heart here?

S1 sound

What is the S2 sound?

The dub from closure of aortic and pulmonic valves

Diastole

Where do you hear the S2 sound?

Apex of heart

What is happening here?

S2

What does a split S2 of lub-BDUB mean?

Pathology

What is S3?

Lub DubUhW or ventricular gallop

What can cause an S3?

Severe mitral insufficiency

DCM

PDA

HCM

Systolic anterior motion of mitral valve with obstructive HCM

What is S4?

BuhLub Dub

Atrial gallop

What can cause an S4?

HCM

Concentric hypertrophy form systemic hypertension

DCM

What is it called when is speeds up and slows down with breathing?

Regularly irregular sinus arrythmia

What can cause chaotic rhythm?

Pulse deficits

Ventricular and supraventricular premature beats

A-fib