EIM 9 Cardio Flashcards
Tricuspid Valve Regurg
usually physiologic, silent on auscultation in clinically normal horses
detectable by Doppler studies in many clinically normal horses.
What murmur grade is less likely to be clinically relevant?
2 or less
If a diastolic mitral valve fluttering is identified, what other pathology needs to be ruled out?
Aortic valve regurgitation
What is the most commonly recognized congenital heart defect in foals?
Perimembranous ventricular septal defect
When pulmonary-to-systemic flow ratio (Qp:Qs) of a shunt exceeds _____ the shunt is considered clinically relevant, resulting in obvious volume overload of the left atrium and left ventricle
1.8:1 (>1:1 implies a left to right shunt)
What is the most consistent physical examination finding associated with a ventricular septal defect?
Harsh holosystolic/pansystolic murmur loudest just below the tricuspid valve region–most defects communicate near the tricuspid valve
pentalogy of Fallot
Large, unrestrictive ventricular septal defect
Overriding and malalignment of the aortic root
Right ventricular outflow tract obstruction
Right ventricular hypertrophy
Patent ductus arteriosus
Which echographic finding is most indicative of hemodynamically important mitral regurgitation?
Circular, turgid appearance to the left atrium–often enlarged as well; indicative of volume overload and decreased function
Define the relationship between cardiac output in the left and right ventricles
COleft = COright
Because they are arranged in series, cardiac output on each side must be equivalent. Therefore compensatory changes can be seen in the opposite side of the heart in unilateral ventricular failure/dysfunction.
Incompetent valves
result in eccentric ventricular hypertrophy
Double apex sign
is an indicator of marked right ventricular enlargement
Which type of adrenergic receptors predominate in the equine heart?
Beta 1
Atrial contraction is responsible for ___% of ventricular filling at rest
15-20
direct determinants of ventricular stroke volume
Preload (ventricular end-diastolic volume)
Contractility
Afterload (wall tension required to eject blood)
Cardiac lesions increasing workload
Frank-Starling mechanism
The ability of the heart to change its force of contraction in response to changes in preload
This changes stroke volume, allowing the heart to respond to systemic changes
Systolic clicks
Over great vessels - benign
Over the mitral valve -thought to be a marker for MV disease or prolapse of the valve into the left atrium
Identify the two most common arrhythmias in the horse
2nd-Degree AV Block
Sinus arrhythmia
systolic ejection murmur
It is the most common functional murmur
It must occur between S1 and S2
It can be up to grade 4-5/6, with significant daily variation
It is best heard over the aortic and pulmonic valves, and may project into their arteries at the left cardiac base.
How soon after exercise must a stress echocardiogram be performed to identify global or regional myocardial dysfunction?
Up to 2-3 minutes, HR > 100 BPM
Treatment of AF is recommended for all horses that are still in use for any type of athletic activity when the average maximal HR during sustained maximal exercise exceeds how many beats/min
220
Electrical cardioversion (TVEC) involves a timed shock delivery on which ECG wave?
R
Ventricular origin impulses
Are conducted abnormally and more slowly, resulting in a widened QRS, an abnormal QRS orientation, and abnormal T waves.
Junctional impulses
Are more likely to result in a narrow, relatively normal-appearing QRS complex with normal initial activation and electrical axis, because they originate above the ventricular myocardium.
features of complex or potentially “malignant” ventricular arrhythmias:
-severe hemodynamic compromise (systemic hypotension, poor pulse quality, -prolonged capillary refill time, weakness, collapse)
-sustained VT
-rapid ventricular rate (greater than 120 beats/min)
-short coupling intervals (particularly with R-on-T complexes)
-multiform or polymorphic QRS morphology (including torsades de pointes)
hyperkalemia
Broadening and flattening of the P wave are the most consistently observed change. Prolongation of the PQ interval and bradycardia develop, excitability decreases, and atrial standstill (sinoventricular rhythm) characterized by complete absence of P waves may be observed.
Either inversion or enlargement (tenting) of the T waves is also likely.
Marked widening of the QRS complex may be noted as near-lethal concentrations of potassium are approached
