Cardiology Flashcards
Possible heart sounds in horse
2 to 4 S1 - lub = closure of AV valves S2 - dub = closure of semilunar valves S3 - ahh = end of rapid filling phase S4 - ba = atrial contraction
ECG
cannot perform typical vector analysis because Purkinje fibers deeply penetrate myocardium and do not polarize apex to base, more wringing action
Main ECG lead placement is base apex because maximizes depolarization
Normal variants
- notched P wave common
- negative QRS (intervetricular septum depolarization)
- large T wave
preferred method of evaluating equine heart
echocardiography
normal HR
26-44bpm
_______ predominates at rest in the horse
vagal tone
ECG lead placement
+ on left thorax
- on right jugular furrow
ground at any point remote form heart
Most common PHYSIOLOGICAL arrhythmia in the horse
Mobitz I 2nd degree AV block = Wenkebach
Most common pathological arrhythmia in the horse
Atrial fibrillation
is Mobitz Type II always pathologic?
yes
Presenting complaint of horse with Afib
exercise intolerance (quitting at 3/4post, pulling up) tachypnea EIPH CHF collapse myopathy, colic
2 forms of Afib
paroxysmal - occurs during race and can disappear with deceleration of the HR
- may be associated with K depletion in horses given furosemide or oral bicarb pre-race
Sustained - easier to Dx because rhythm sustained over long period of time
PE of horse with A fib
auscultation - irregularly irregular, sounds like shoe in drier
pulses - variable strength
ECG of an Afib horse
baseline fibrillation wavs (F waves) = soars or fine
QRST usually normal morphology but irregularly spaced
NO P WAVES
Treatment of Afib
If HR and echo normal –> give Quinidine
If HR high or abnormal echo –> Digoxin then Quinidine
If HF –> don’t Tx the Afib, Tx the HF
MOA of Quinidine as Tx for Afib
blocks fast inward Na current in myocardium
How do you Tx quinidine toxicity
Tx acute toxicity w. IV sodium bicarbonate
Idiosynchratic rxn to quinidine
causes rapid supra ventricular tachycardia
Dosing Quinidine
if acute <72h, can use IV
- give small bolus Q 10 min, do not exceed 12mg/kg
More typically, use PO quinidine
can use 5mg test dose, then 20-22mg/kg q2h until converted
stop if toxic side effects, or reach 60g
Ventricular tachycardia
associated with metabolic disease
caused by myocarditis, endotoxemia, hypoxia, electrolyte disturbances
Clinical signs of VT
exercise intolerance, can lead to syncope
Treating VT
LIDOCAINE, bolus or infusion
indicated in sick colicy patients
Pathological murmurs in the horse
mitral insufficiency - systolic murmur on L side
aortic insufficiency - diastolic murmur on L side
tricuspid insufficiency - systolic murmur on R side
most important murmur in the horse
mitral insufficiency
clinical signs of mitral insufficiency
vary depending on severity of valvular dysfunction
most likely valvular dysfunction leading to cardiac failure
mild: exercise intolerance
severe: sudden death, chord tendinae rupture, acute decompensation in failure (most common cause of valvular death in horses)
Most common site of bacterial endocarditis?
mitral valve
Diagnosing mitral valve insufficiency
LA and LV size, regurgitation fraction, PA size
may hear murmur if severe
may show Afib because enlarged atria
most likely to lead to HF
mitral valve insufficiency
if have mitral valve insufficiency and chord tendinae rupture, murmur sounds like
honking murmur like geese
if pulmonary artery ruptures
sudden death
Aortic insufficiency
seen in older horses
noisy musical diastolic murmur, mostly on L side
incidental finding but can lead to failure
Prognostic factors of valve insufficiency
type of valvular disease
degree of L sided volume overload
size of regurgitant jet
age of horse
Mitral: size of PA
Aortic: size of aortic root, presence/absence of concurrent L AV insufficiency
Vegetative endocarditis
mitral valve more commonly
young horses, males more than females
endothelial damage –> bacteria can adhere –> local clotting activated
CS: fever of unknown origin, tachycardia, murmur, poor doing colic (from ileus from perfusion problems)
Dx: CBC (inflammation), Chem (organ dysfunction from CV compromise), blood culture to isolate organism
Tx: 4-6w of antimicrobials minimum, anti inflammatories (aspirin or flunixin) to help w/ clotting
Follow up protocol for endocarditis
blood culture 60d after cessation of antibiotics
at least 3 cultures
3 important causes of HF
mitral valve insufficiency
pericarditis
ionophore toxicosis
3 forms of pericarditis
effusive - usually viral
constrictive (fibrinous) - usually bacterial, pleuropneumoniae
combined
clinical signs of pericarditis
FEVER, edema, distended jugular veins, poor pulses, weakness, listlessness, syncope, acute developing failure
Tx pericarditis
Effusive - drainage
Constrictive - pericardectomy
HF drugs diuretics - furosemide inotropes - digoxin ACEi - enalepril vasodilators - hydralazine
