Cardiovascular System part 2

what is the most common clinically significant arrhythmia in the horse

Atrial Fibrillation

in which type of horses is Atrial Fibrillation most common

young male standardbreds and draft horses

what would you hear upon auscultation in a horse with Atrial Fibrillation

an irregularly irregular rhythm and pulse and variable intensity of heart sounds

what are some signs of Atrial Fibrillation

exercise intolerance (#1 complaint), epistaxis, weakness, weight loss, poor performance, dyspnea

what does an ECG reading of Atrial Fibrillation look like

fibrillation waves replace the p waves (squiggles)

how is Atrial Fibrillation treated if there is no other heart disease

quinidine treatment until conversion to normal sinus rhythm

true or false- Atrial Fibrillation often occurs with no obvious underlying heart disease

true

with Atrial Fibrillation, how is the conversion back to normal sinus rhythm maintained

enalapril (ACE inhibitor drug)

What is the prog with Atrial Fibrillation

most horses respond to therapy, if there is evidence of Congestive heart failure, the prognosis is poor

what are the two main congenital cardiovascular diseases

Ventricular Septal Defect (VSD) and Patent Ductus Arteriosus (PDA)

what is the most common CONGENITAL cardiac defect in the horse

VSD (ventricular septal defect)

With a VSD, why is there a left to right shunting of blood

Because the blood flows from high pressure to low pressure (left side is high pressure, right side is low pressure)

what are the main effects of Ventricular Septal Defect on blood flow

increased amount of blood to lungs, pulmonary hypertension, dilation of right ventricle, decreased amount of oxygenated blood to the body

what are some signs of Ventricular Septal Defect

exercise intolerance, lethargy, cyanosis, stunted, murmur, possible heart failure

what type of murmur is usually heard with Ventricular Septal Defect

harsh, holosystolic (entire time of systole) murmur on right side (blood hitting that side of the wall)

How is Ventricular Septal Defect diagnosed

auscultation, ultrasound and color-flow doppler

how is Ventricular Septal Defect managed

small defect: may require no special management

large defect: pasture use only

What is the ductus arteriosus?

A structure in embryo connecting the pulmonary artery to the aorta.

what normally happens to the ductus arteriosus after birth

The first few oxygenated breaths cause it to close

What does PDA stand for

patent ductus arteriosus

What is patent ductus arteriosus?

a congenital heart defect where a temporary fetal blood vessel connecting the pulmonary artery and the aorta fails to close after birth

What does the ductus arteriosus do in the womb?

it allows blood to bypass the non-functional lungs, as the placenta provides oxygen

patent ductus arteriosus produces a ________ to _________ shunting of blood between the ___________ and _____________

left, right, aorta, pulmonary artery

What does Patent Ductus Arteriosus produce and where?

A left to right shunting of blood between the aorta and pulmonary artery

In a horse with a left-to-right shunt caused by Patent Ductus Arteriosus (PDA), which heart chambers experience volume overload?

The left atrium and left ventricle.

What type of heart failure can result from a left-to-right shunt caused by Patent Ductus Arteriosus, and what are two possible outcomes?

Left-sided heart failure and sudden death.

what are some signs of Patent Ductus Arteriosus

stunted, increased RR, coughing, loud washing machine murmur

how can Patent Ductus Arteriosus be treated

surgery, possible flunixin meglumine (may block release of hormones that keep DA open)

What is endocarditis

lesions found on the heart valves

which valve is most commonly affected by endocarditis

aortic valve

What are 2 ways that cardiac function is affected with endocarditis

lesion affects the competence of the valve, lesion produces and obstruction to forward flow of blood

Does endocarditis produce a murmur and why

yes because there is disruption of laminar blood flow

what are the 2 main types of endocarditis

degenerative valvular lesions in older horses or bacterial endocarditis (causes vegetative growth)

what are signs of bacterial endocarditis

exercise intolerance, chronic intermittent pyrexia (fever), respiratory disease, DIASTOLIC murmur (aortic valve insufficiency usually)

How is bacterial endocarditis diagnosed

signs, murmur, echocardiography, blood (c+s)

How is degenerative endocarditis diagnosed

signs, murmur, and echocardiography

how is bacterial endocarditis treated

appropriate ATB based on C+S, NSAIDS, cardiac supportive drugs (furosemide, hydralazine, digoxin)

how is degenerative endocarditis treated if in congestive heart failure

furosemide, hydralazine, digoxin, avoid salt supplements, stall rest

Why should you avoid salt supplements when in congestive heart failure

salt increases fluid retention which increases the blood pressure, putting more strain on the heart

what is the prognosis for endocarditis

guarded to grave, sudden death may occur

What is myocarditis

inflammation of the myocardium

Is myocarditis common or uncommon in horses

uncommon, rare

what is myocarditis usu secondary to

septicemia or pericarditis caused by bacteria or viruses

what is the treatment for myocarditis

rest, ATB, drugs for heart failure

what does furosemide (Salix) do

it is a diuretic (helps kidneys get rid of unneeded salt and water which makes it easier for the heart to pump)

what does hydralazine do

It is an arterial vasodilator (dilates arteries - increases cardiac output and decreases pulmonary vascular resistance)

when is hydralazine used

endocarditis and congestive heart failure

what does digoxin do

Increases contractility of the heart (slows, strengthens, and regulates the heartbeat)

what is the prognosis for myocarditis

good if heart failure doesn't occur

what is pericarditis

inflammation of the pericardium which produces an excessive amount of fluid

What happens to the heart in pericarditis

extra pressure is put on the heart which compromises cardiac filling

what are the two types of pericarditis

effusive and constrictive

what is effusive pericarditis

excessive amount of fluid produced (makes it so heart can'f fill up with as much blood)

What is constrictive pericarditis?

pericardium is altered so that it s stiff and doesn't stretch as the heart fills

what is pericarditis usu secondary to

pleuritis

what are some clinical signs of pericarditis

fever, tachycardia, peripheral edema, jugular vein distension, increased CRT, muffled heart sounds (like the heart is under water), decreased amplitude of waves on ECG

how is pericarditis diagnosed

clinical signs and echocardiography

how is pericarditis treated

pericardiocentesis ( for effusive form - remove extra fluid), pericardiectomy (for constrictive for - remove parts of pericardium), ATB, NSAIDS

what is the prognosis for pericarditis

poor

What is dialated cardiomyopathy or DCM

enlarged heart

how is DCM diagnosed

echocardiogram

what does Right sided heart failure refer to

right ventricular hypertrophy (right ventricle of the heart becomes abnormally enlarged and thickened)

what is right ventricular hypertrophy secondary to

disorders that cause an excessive amount of blood to enter the pulmonary circulation

what are some signs of Right sided heart failure

possible murmur of tricuspid insufficiency, if hypertrophy has altered the valve, RAO signs, subcutaneous ventral edema

how is Right sided heart failure treated

digoxin, diuretics, treat underlying disease (management not cure)

which drug complements quinidine and increases fibrillation threshold so less quinidine can be used

digoxin

what are the 3 main things that happen with congestive heart failure

heart has undergone a change, heart no longer maintains adequate cardiac output, body starts to retain sodium and water (edema)

what is Left sided heart failure

left side of heart pumps inadequately usually due to the development of a faulty valve

what are some signs of Left heart failure

decrease in stroke volume, over circulation of pulmonary vascular bed ( blood backs up into lungs), pukmonary edema, increased RR and effort

what would be a sign of severe L heart failure

frothy, serous nasal discharge

what is right heart failure typically caused by

valvular disease, myocardial disease, or pericardial effusion

What are the main goals of therapy for congestive heart failure

support the heart, remove edema, decrease heart workload

what EMERGENCY drugs are used to increase cardiac output to improve tissue perfusion

dopamine and dobutamine

what LONGTERM drug is used to increase cardiac output to improve tissue perfusion

digoxin

What drugs are used to treat congestive heart failure

Digoxin, hydralazine, furosemide

which drug is most commonly used in congestive heart failure

digoxin