Cardiology Flashcards
Give 6 negative prognostic factors in structural heart disease.
○ Progressive chamber remodelling- dilated and altered chamber shape
○ Chamber dysfunction
○ Great vessel enlargement
○ PHT
○ CHF
Potentially dangerous arrhythmias
Give the 8 instances where echocardiography is recommended
- A previously diagnosed ‘functional’ murmur that is louder on serial examination
- A grade >3 left sided murmur compatible with MR or AR
- A grade >4 right sided murmur compatible with TR
- A suspected VSD or other congenital heart lesion
- Continuous or combined systolic/diastolic murmur
- Clinically important arrhythmias, even in the absence of a murmur
- Suspected myocardial injury
- Suspicion of CHF
What 2 factors should be incorporated into an exercising ecg?
Work intensity should be at or slightly exceeding the horse’s customary activities
Should include some method of stimulating unexpected sympathetic stimulation
What 4 specific measurements should be incorporated into an exercise test?
- Effects of exercise on auscultation (HR, rhythm, murmurs)
- Peak HR during exercise
- HR and rhythm during different phases of exercise and recovery
- Optional: Echo before and after exercise (stress echocardiography)
Describe a typical MR murmur
Mid-late systolic or holo/pansystolic left sided
Give 6 Underlying lesions that may be responsible for MR
Mitral valve dysplasia
Degenerative or inflammatory valve thickening.
Prolapse= MVP
Thickened or ruptured chordae tendinae= RCT
Flail leaflet
Secondary to valve annulus or ventricular dilatation in severe AR, non-restrictive VSD or, rarely, cardiomyopathy.
What secondary changes occur in severe MR?
PHT and enlargement of the LA and LV
In the absence of PA catheterisation, what measures can be used to estimate PHT?
TR velocity and PA diameter
Why is assessment of LV function difficult in MR?
increased preload and reduced afterload.
What changes occur to LV function in acute/severe MR disease?
LV hyperdynamic: increased FS, dynamic compression of the RV and exuberant septal motion
What changes occur to LV function in chronic MR disease?
progressive remodelling and LV dysfunction. -> reduced FS to within or below normal range
What kind of MR jet is often under-estimated?
An MR jet that is eccentric, wall hugging or flat
What are the major negative prognostic indicators for MR?
○ Moderate-severe regurgitation
○ Endocarditis
○ RCT
○ Flail leaflet
○ Severe valvular thickening
○ Concurrent PA dilation
○ Increased TR velocity
○ Significant MR with AF or tachycardia
What is the most common cause of AR?
degenerative valve thickening and/or AV prolapse
Give 7 less common causes of AR
Congenital malformations
Leaflet tearing
Endocarditis
Valvulitis
Fenestrations
Aortic root disease
In association with VSD.
describe the AR murmur
left sided holodiastolic
What is the most common structural change of the AV associated with AV, as visible on 2D echocardiography?
thickening as a fibrous band-like lesion appearing as an echoic line parallel to the free edge if the left coronary leaflet
Which AV leaflet is most commonly affected in AR?
left coronary leaflet
What does premature closing of the MV on M-mode indicate?
markedly increased LV end diastolic pressure= severe AR.
Why may the MV not fully open in AR?
Eccentric jets directed towards the MV can prevent full MV opening.
Why may the MV flutter in AR?
Diastolic fluttering of the mitral or aortic valves, aortic root or IVS if the jet is directed towards these structures.
What does LA enlargement indicate in AR?
ventricular dysfunction, volume retention or concurrent MR
Give 3 as yet unvalidated measurements of AR severity
regurgitant signal duration, pressure half time, velocity time integral of AR compared to forward flow.
Above which pulse pressure is AR progression more likely?
60mmHg
When is echocardiography of a suspected TR indicated?
grade 4/6 or louder
Poor performance
Concurrent thrombophlebitis
With fever of unknown origin
PPE
Give 3 findings that would indicate a TR was benign/ training related
Valve is structurally normal
RA and RV are normal in size
Regurgitant jet is thin and directed towards the aorta
Above which TR velocity should you suspect PHT?
3.5m/s
Give 3 findings on echo that would indicate a TR was clinically significant.
Structural or motion abnormalities in the TV
RA and RV enlargement
Jet is wider at origin and occupies a larger area in the RA (often central or towards the RA wall).
In which breeds is VSD predisposed?
- Welsh sec A, Standardbreds and Arabians over-represented
Describe the typical VSD
peri membranous, located ventral to the tricuspid leaflet and below the junction of the right and non-coronary cusps of the aortic valve.
Give 3 types of VSD
perimembranous, subarterial, muscular
describe a subarterial vsd
beneath the semilunar valves
describe a muscular VSD
apical
Up to what VSD diameter is the VSD unlikely to be haemodynamically important?
2.5cm
Flows above what peak velocity is indicative if a better prognosis in VSDs?
4.5m/s
what does a peak flow velocity of <4.5m/s across a VSD indicate?
greater shunt volume.
what may reduce the functional size of a VSD?
TV adhesions, fibrous tissue proliferation
Give 6 prognostic criteria for VSDs
Size of VSD
Size of cardiac chambers
Maximal shunt velocity
Presence of significant AR or MR
PHT
CHF
What arrhythmia is commonly associated with an aorto-pulmonary fistula?
VT
What breed is predisposed to aorto-cardiac fistulae?
Freisians
describe the clinical presentation of an aorto-cardiac fistula
bounding arterial pulses, tachycardia, and a grade 1–3/6 holosystolic and early-to-mid diastolic murmur loudest dorsal to the aortic valve
may be in acute CHF, or just poor performance
Describe the criteria for a high grade 2nd degree AVB
> 2 consecutively blocked P wave
Should horses with a high grade AVB be ridden?
Horses with high-grade second degree AVB that disappears with exercise should only be ridden or driven by an informed adult, and the HR and rhythm should be frequently monitored.
Horses with high-grade second degree AVB during exercise or after atropine administration should be rested and re-evaluated; they are considered less safe to ride or drive than their age-matched peers
describe the appearance of an APC on an ECG
ectopic, premature atrial activation (P’), usually with changes to P wave morphology
Can be conducted with a variable P’-R interval or blocked at the AVN
The conducted QRS is generally normal but can be abnormal with secondary ST segment and T wave changes.
Are horses with APCs safe to ride?
- Horses with occasional PACs that are over driven during exercise and those with occasional PACs during exercise are considered as safe to ride or drive as their age-matched peers
What is the definition of VT?
3+ repetitive or linked VPCs.
Do VPCs have a compensatory pause?
generally yes
What is ‘bruit de cannon’?
Rapid, generally irregular rhythm with variable intensity or ‘booming’ heart sounds associated with VT
Describe a PVC on an ECG
premature QRS without P, wide and bizarre, and followed by a large T wave of opposite polarity.
Give 5 characteristics of a complex or potentially “malignant” VA:
multiform or polymorphic QRS morphology
short coupling intervals (especially R-on-T timing)
sustained VT
rapid ventricular rate (exceeding 120 beats/min)
repetitive ectopic activity (couplets, VT).
Describe an accelerated idioventricular rhythm
Monomorphic
start with a relatively long coupling interval
become established at relatively slow ventricular rates (50–80/min at rest)
Following resolution of VT, how long should a horse be in NSR before re-evaluation?
4 weeks.
describe paroxysmal AF
Acute onset AF: generally spontaneously convert to NSR within 24-48hours.
decribe lone AF
AF in the absence of detectable underlying heart disease
In which breed has AF been demonstrated to be heritable?
standardbreds
Describe AF on an ECG
Irregularly irregular R-R interval with normal QRS morphology, the absence of P waves and the presence of “f” waves.
What is the difference between AF and atrial flutter
Flutter waves resemble saw-toothed P waves with-out an isoelectric shelf and have a regular atrial rate of about 170–275/min, while fibrillation waves are less organized and faster (275–500/min on intracardiac electrograms)
What is atrial flutter?
a slow macro-re-entry variation on AF.
Describe atrial flutter on an ECG
Flutter waves resemble saw-toothed P waves with-out an isoelectric shelf and have a regular atrial rate of about 170–275/min
AV conduction in atrial flutter is usually variable, resulting in a ventricular rate response that can be irregular or regular during periods of increased sympathetic tone.
Patterns of 3 : 1, 2 : 1, or 1 : 1atrial-to-ventricular conduction can be observed.
does a slighlty increased LAD in a horse with AF indicate structurally significant remodelling?
No: A slight increase in LA size can result from AF, even in the absence of MR.
Why is LV function difficult to assess in AF?
ventricular dyssynchrony=tachycardia induced LV dysfunction
Also hampered by the preload and HR dependence of many echo indices.
Aside from affect on performance, when is cardioversion of AF recommended?
Average max HR at normal activity level 220bpm
Concurrent VA observed (usually resolve after cardioversion).
Give 3 management strategies for AF
No treatment
Pharmacologic cardioversion
TVEC
When should horses not be cardioverted?
CHF
First 24-48hours of AF (may spontaneously convert
what is the reported success rate of AF cardioversion?
65–90%
Indications for Quinidine
Lone AF
AF with mild LA enlargement
Comorbidities in which GA or TVEC not option
Contraindications for quinidine
Rapid ventricular response to AF
Complex ventricular ectopy (risk polymorphic VT with Quinidine)
Indications for TVEC
one AF
AF with mild LA enlargement
horses either intolerant of or unresponsive to quinidine treatment or horses in which quinidine is contraindicated (see above)
What are the risks associated with TVEC?
GA
Development of fatal arrhythmia
The immediate recurrence of AF (IRAF) within the first 24 hours after cardioversion, although infrequent, is more likely than with quinidine cardioversion.
During which wave is the shock delivered in TVEC?
R
when is AF recurrence rate lowest?
○ Rate is lowest (15%) in lone AF of recent onset (<1month)
Give 5 anti-arrhythmic drugs that may reduce AF recurrence?
propafenone, sotalol, flecainide, amiodarone, phenytoin
What medications should be avoided after cardioversion of AF?
furosemide, supplements containing sodium bicarbonate, and thyroid hormones after cardioversion.
How long should horses with paroxysmal AF be rested?
1 week
How long should horses with sustained AF be rested after cardioversion?
4-6 weeks, or until LA function normalised
