Unit 1 - Cardiology (Ventricular arrythmias to end) Flashcards
What occurs when there is a first degree AV block?
There is an increase in the P-R interval above .4 seconds at rest - as the interval increases, so does the time in between S4 and S1
Is first degree AV block clinically significant?
no
What horses is second degree AV block common in?
large, fit horses
What does Mobitz I mean?
In reference to second degree AV block, there may be a gradual increase in the P-R interval, then impulse blocked at the AV node
What does Mobitz II mean?
In reference to second degree AV block, there may be no apparent increase in the P-R interval, with spontaneous occasional block at the AV node
What does second degree AV block sound like on auscultation?
the diastolic pause is twice the normal length with S4 in the middle of the pause
What is likely the cause of a second degree AV block?
It is probably a baroreceptor feedback that is vagally mediated
What can induce a second degree AV block?
alpha-2 agonists
Third degree AV block is due to a complete _________ with the AV node.
dissociation
What is a premature ventricular contraction?
When the beat is earlier and louder than normal, not preceded by the atrial sound - often followed by a compensatory pause
What is the etiology associated with premature ventricular contractions?
It isn’t completely understood - most horses have no cardiac lesions, 10-12% have inflammatory/degenerative lesions, some substances cause severe myocardial damage
When horses drop dead while being watched, or are found dead, what is the likely cause?
They probbaly suffer acute ventricular arrythmias - ventricular fibrillation or sustained ventricular tachycardia
In what population of horses are flow disorders typically detected in? Are they clinically significant?
older horses, most are not significant
True or False: The loudness of a murmr is not a good indication of size or significance of a lesion.
TRUE - the area over which a murmur radiates is usually more useful in determining the significance than is loudness
What are most equine murmurs due to?
non-infectious acquired lesions
Where are systolic murmurs audible?
over the aortic root or over the mitral valve
What is a common systolic murmur over the aortic root?
physiologic ejection murmur
What are systolic murmurs audible over the mitral valve mostly due to?
mild forms of mitral insufficiency
What happens if the mitral chordae tendinae ruptures?
animals drop dead, there is a sudden onset of pulmonary edema with dyspnea, heart failure develops in 24-48, and there is often a loud, widely radiating pansystolic murmur, often with a palpable thrill
What are over 90% of diastolic murmurs due to?
aortic insufficiency
What do diastolic murmurs sound like?
they vary from musical, a pure tone, to a noisy mixed murmur - usually pandiastolic
What valve is commonly affected by endocarditis?
the aortic valve
What clinical signs are associated with endocarditis?
fever, anorexia, and weight loss
When do murmurs associate with endocarditis typically develop?
late in disease - heart failure is common late in disease
What is the prognosis for horses with endocarditis?
grave
What is the most common congenital heart lesion in horses?
ventricular septal defect (VSD)
What horse breed is commonly affected by congenital heart lesions?
Arabian
What congenital lesion is very rare in horses?
Patent ductus arteriosis (PDA)
What treatment is required for maintaining patency of PDA?
Eicosanoids
What other medications are important for treatment of PDA?
NSAID’s
How long does it take for PDA to close?
in four days
Characterize pericarditis in horses.
It is often septic, a chronic, progressive disease course
Sound 3 of the cardiac cycle is produced by the sound associated with:
a. Closure of the aortic and pulmonic valves
b. Closure of the semilunar valves
c. rapid ventricular filling
d. Closure of the atrioventricular valves
c. rapid ventricular filling
Sound 4 of the cardiac cycle is produced by the sounds associated with:
a. closure of the aortic and pulmonic valves
b. rapid ventricular contraction
c. atrial contractio
d. closure of the ductus arteriosis
c. atrial contraction
A twice normal diastolic pause is auscultated in a horse. During the pause, a distinct heart sound is detected. The findings are most consistent with:
a. Atrical fibrillation
b. 2nd degree atrio-ventricular heart block
c. Atrial arrest with subsequent idioventricular contraction
d. sinoatrial block
b. 2nd degree atrio-ventricular heart block
In the attached ECG, the impulse is blocked at (which arrow) which produces a twice normal diastolic pause? (A, B, or C)
A. it is a sinoatrial block
