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LAIM Test > Cardio & Circulatory > Flashcards

Cardio & Circulatory Flashcards

1
Q

Which one of the following statements regarding atrial fibrillation in the horse is TRUE?

A. Digoxin should not be given to horses with atrial fibrillation before quinidine therapy.

B. Quinidine, a positive inotrope, is the drug of choice to convert atrial fibrillation to sinus rhythm.

C. The fourth heart sound is usually audible during cardiac auscultation.

D. The heart rate is rarely above 50 beats per minute unless there is underlying cardiac disease.

A

D. The heart rate is rarely above 50 beats per minute unless there is underlying cardiac disease.

Ref: Smith. LAIM 4th ed., 2009; p 483-486.

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2
Q

Idiopathic hemorrhagic pericardial effusion in cattle is BEST treated with which of the following?

A. Long term antibiotic therapy

B. Pericardial drainage and lavage

C. Rib resection and pericardial marsupialization

D. Vitamin K therapy and diuretics

A

B. Pericardial drainage and lavage

Ref: Peek, Simon. ACVIM Forum Proceedings. 2010. Jesty et al., J Am Vet Med Assoc. 2005; 226(9):1558-2. Firshman et al., J Vet Intern Med. 2006; 20:1499-1502.

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3
Q

The following ECG (paper speed 25 mm/sec) was recorded from a 3-year old cow. Which of the following would be the MOST correct interpretation of the rhythm?

*Narrowed QRS complexes and T wave deformed, with a peak appereance

A. Atrial premature contraction

B. Second degree A-V block

C. Sinus arrhythmia

D. Ventricular premature contraction

A

A. Atrial premature contraction

Ref: Vet Med, 10th, pp. 415-416.

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4
Q

Where are the peripheral chemoreceptors?

-How or what do they respond to?

A

Carotid and aortic bodies

Response to:

* decrease in arterial pO2 - increases in peripheral chemoreceptor by increasing RR

* increase in arterial pCO2 - increases peripheral chemoreceptor by increasing RR

* increase in arterial [H+] - creates metabolic acidosis by increasing RR

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5
Q

Which pair of anti-arrhythmic drugs can excessively prolongue action potential duration if given together?

a. Sotalol and mexiletine
b. Atenolol and quinidine
c. Procainamide and lidocaine
d. Sotalol and quinidine

A

d. Sotalol and quinidine

Quinidine is a class Ia drug, a Na channel blockers that increases the Action Potential Duration. Sotalol is class III drug, non-cardioselective beta-blocker that possesses K channel blocker properties, it prolongs the AP duration and effective refractory period in atrium and ventricle, and in nodal and extranodal tissue as it is a potent competitive inhibitor for potassium current.

* Class Ia drugs prolong both the QRS and QT of the normal heart by blocking the rapid potassium current (IKr) at therapeutic concentrations. These drugs also block cardiac Na channels in the open state, and then dissociate slowly & incompletely during diastolic intervals in-between beats. Hence block accumulates with each successive beat, resulting in enough Na channel block at normal sinus rates to significantly widen the QRS.

* Class III agents in the Vaughan-Williams classification system for antiarrhythmic medications possess K channel blocking effects. Sotalol exhibits reverse use-dependent effects, meaning that the maximal potassium current blocking effect occurs when the heart rate is slow, increasing the risk of QT prolongation and torsades de pointes in bradycardic conditions.

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6
Q

Which of the following will shift the O2-hemoglobin dissociation curve to the left?

a. Increased body temperature
b. Decreased blood pH
c. Decreased blood H+ ion concentration
d. Increased blood pCO2

A

c. Decreased blood H+ ion concentration

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7
Q

Which is a common ECG finding in a hyperkalemic patient?

a. Presence of U waves
b. Abbreviation of the QRS
c. Prescence of tall T waves
d. Depression of the ST segment

A

c. Prescence of tall T waves

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8
Q

What is the most common electrocardiographic findings in dogs with tricuspid valve dysplasia?

a. Atrioventricular block
b. Deep S-wave
c. Splintered QRS
d. Ventricular tachycardia

A

c. Splintered QRS

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9
Q

The solid line represents the ventricular function curve of a normal left vetricle. In which of the fllowing cardiac diseases will the primary underlying dysfunction result in the ventricular function curve represented by the dotted line?

a. Hypertrophic cardiomyopathy
b. Cardiac tamponade
c. Restrictive cardiomyopathy
d. Dilated cardiomyopathy

A

d. Dilated cardiomyopathy

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10
Q

CO2 in blood is predominantly transported as which of the following?

a. Dissolved CO2
b. CO2 bound to protein
c. HCO3
d. H2CO3

A

c. HCO3

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11
Q

Which of the following statements regarding total CO2 (TCO2) is correct?

a. TCO2 is the best suited parameter for diagnosing metabolic acidosis
b. TCO2 and HCO3 can be used interchangeably because both parameters are tightly and linearly correlated
c. Decreased TCO2 is consistent with metabolic acidossi but not with a compensatory respiratory alkalosis
d. TCO2 is a value calculated from the pCO2 in plasma
e. Isolated TCO2 measurement does not allow diagnosis of acid-base disturbances

A

e. Isolated TCO2 measurement does not allow diagnosis of acid-base disturbances

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12
Q

Describe the following ECG rhythm:

a) Atrial flutter with premature ventricular contraction
b) Prolonged T waves and large QRS secondary to hyperkaliemia
c) Second degree Mobitz type II atrioventricular block
d) Ventricular tachycardia with torsade de pointes

A

d) Ventricular tachycardia with torsade de pointes

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13
Q

ECG evaluation of a horse reveals a bradyarrhythmia with a tall, peaked T wave and a loss of P wave. Which of the following electrolyte abnormalities is most likely?

a) Hypercalcemia
b) Hyperchloremia
c) Hyperkalemia
d) Hypernatremia

A

c) Hyperkalemia

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14
Q

Atrial fibrillation in cattle is most commonly associated with which of the following:

a) Gastrointestinal disease
b) Primary cardiac disease
c) Respiratory disease
d) Toxic mastitis

A

a) Gastrointestinal disease

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15
Q

A descrescendo, pan-diastolic murmur heard loudest on the left side of the thorax is most likely what type of defect?

a) Aortic regurgitation
b) Aorto-cardiac fistula
c) Mitral regurgitation
d) Tricuspid regurgitation

A

a) Aortic regurgitation

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16
Q

Which of the following is true regarding the pressure-volume relationship of the left ventricle?

A. Pressure decreases during the entire ejection phase

B. When the aortic valve closes, pressure begis to increase

C. The net external work output is represented by the area inside of the pressure-volume loop

D. Pressure decreases during the filling phase

A

C. The net external work output is represented by the area inside of the pressure-volume loop

17
Q

Which of the following does NOT occcur during the period of isovolumic contraction in the left ventricle?

A. All the valves are closed

B. The pressure inside the ventricle increases to that equal of the pressure within the aorta

C. The pressure within the ventricle is approximately 80 mmHg

D. The ventricle expands to accept the influx of atrial blood

A

D. The ventricle expands to accept the influx of atrial blood

18
Q

Which of the following drugs does NOT cause contraction of vascular smooth muscle resulting in an increase in pulmonary vascular resistance?

A. Nitric oxide

B. Norepinephrine

C. Histamine

D. Serotonin

A

A. Nitric oxide

19
Q

This reflex is responsible for RA enlargement causing an increase in heart rate?

A. Brahman reflex

B. Bainbridge reflex

C. Atrial reflex

D. Baroreceptor reflex

A

B. Bainbridge reflex

Also called the atrial reflex, is an increase in heart rate due to an increase in central venous pressure. Increased blood volume is detected by stretch receptors (Cardiac Receptors) located in both atria at the venoatrial junctions.

Increased blood volume results in increased venous return to the heart, which leads to increased firing of B-fibers. B-fibers send signals to the brain (the afferent pathway of the neural portion of the Bainbridge reflex), which then modulates both sympathetic and parasympathetic pathways to the SA node of the heart (the efferent pathway of the neural portion of the Bainbridge reflex), causing an increase in heart rate. “Effects on cardiac contractility and stroke volume are insignificant.”

20
Q

All the following conditions can result in high output cardiac failure EXCEPT:

A. Hyperthyroidism

B. Anemia

C. Patent ductus arteriosus

D. Thrombosis

E. Thiamine deficiency

A

D. Thrombosis

High-output heart failure occurs when the cardiac output is higher than normal due to increased peripheral demand. There is circulatory overload which may lead to pulmonary edema secondary to an elevated diastolic pressure in the left ventricle. Patient usually has normal systolic function but has signs of heart failure. With time, this overload causes systolic failure. Ultimately cardiac output can be reduced to very low levels.

It may occur in situations with an increased blood volume, from excess of water and salt (kidney pathology, excess of fluid or blood administration, treatment with retaining water steroids), chronic and severe anemia, large arteriovenous fistula or multiple small arteriovenous shunts as in HHT, some forms of severe liver or kidney disorders, hyperthyroidism, and acutely in septic shock, especially caused by Gram-negative bacteria.

21
Q

This is the most rapidly acting control mechanism in arterial pressure regulation?

A. Baroreceptor feedback mechanism

B. Renin-Angiotensin-Aldosterone system mechanism

C. Capillary fluid shift mechanism

D. Renal body fluid pressure control mechanism

E. Stress relaxation mechanism

A

A. Baroreceptor feedback mechanism

22
Q

A crescendo, pan-systolic murmur heard loudest on the right side of the thorax is most likely associated with:

a. Aortic regurgitation
b. Aorto-cardiac fistula
c. Mitral regurgitation
d. Tricuspid regurgitation

A

d. Tricuspid regurgitation

23
Q

Describe the following ECG rhythm:

a. Atrial fibrillation with third-degree atrioventricular block
b. Second-degree atrioventricular block with atrial premature contractions
c. Atrial flutter with premature ventricular contraction
d. Ventricular fibrillation and tachycardia

A

b. Second-degree atrioventricular block with atrial premature contractions

24
Q

According to the 2014 Consensus Statement, in what situations should an echocardiogram be performed when assessing a horse with cardiac disease?

A

1) previously diagnosed ‘functional murmur’ that is louder on serial examinations
2) grade 3-6/6 left-sided murmur compatible with mitral regurgitation (MR) or aortic regurgitation (AR)
3) grade 4-6/6 right-sided murmur compatible with tricuspid regurgitation (TR)
4) suspected VSD or other congenital heart lesion
5) continuous or combined systolic-diastolic murmurs
6) clinically important arrhythmias, whether a murmur is present or not
7) suspected myocardial injury
8) suspicion of CHF

25
Q

What specific non-invasive cardiac assessments can be made during an exercise test?

A

1) effects of exercise on auscultation (rate, rhythm and murmurs)
2) peak HR during exercise
3) HR and rhythm during the different phases of the exercise test and during recovery
4) (optional) echocardiography before and after exercise (stress echocardiogram)

*Additional tests that might be indicated: analysis of gait, airway dynamics, arterial blood gas tensions and other clinical laboratory tests

26
Q

When evaluating a horse with a murmur, when should an echocardiogram be performed?

A

1) when auscultatory or clinical findings are not consistent with a physiologic murmur
2) if the murmur is moderate to loud
3) on occasion, when a murmur is detected as part of a pre-purchase examination

**Serial echocardiographic evaluations are more meaningful for prognostication than findings from a single examination

Physiologic murmurs:

  • Left thorax (systolic). Point of Maximal Impulse (PMI) over aortic and pulmonic valve area, early-to-midsystolic, crescendo-decrescendo or decrescendo, usually grade 1–3/6
  • Left thorax (diastolic). PMI over mitral & tricuspid valve area, early-diastolic (S2-S3) or late-diastolic (S4-S1), often musical/squeaking (Grade 1–3/6)
27
Q

List the underlying lesions responsible for MR

A

1) mitral valve dysplasia
2) degenerative or inflammatory valve thickening (including bacterial endocarditis)
3) prolapse (MVP)
4) thickened or ruptured chordae tendinae (RCT)
5) flail leaflet

MR can also develop secondary to: - valve annulus or ventricular dilatation (as with severe AR, non-restrictive VSD or rarely, dilated cardiomyopathy)

28
Q

Describe the echocardiographic appearance of a mitral valve prolapse

A

Convex bulging of a mitral leaflet into the left atrium (LA) along with a mid-to-late systolic murmur and Doppler confirmation of MR

29
Q

Describe the echocardiographic appearance of a ruptured chordae tendinae

A

Echoic, whip-like structure moving into the LA during systole which flips into and out of the imaging plane

30
Q

Describe the echocardiographic appearance of a flail mitral valve leaflet

A

Part of the valve leaflet is imaged in the LA and moving chaotically or independently from the rest of the mitral valve.

34
Q

Describe the differences detected during echocardiographic examination between acute and chronic MR and mild vs moderate MR

A
  • Progressive changes in LA and LV size and shape reflect the severity of MR.
  • an absence of remodelling is consistent with mild MR
  • marked enlargement and signs of Pulmonary hypertension (PHT) are typical of severe MR
  • when MR is acute and severe, the LV will be hyperdynamic with increased fractional shortening
  • diastolic compression of the RV with exuberant septal motion also suggests severe LV volume overload
  • chronic MR associated with progressive remodelling and LV dysfunction can lead to fractional shortening returning to the normal range or being obviously reduced
35
Q

Describe what features may help determine a prognosis in a horse with MR?

A
  • horses with mid-to-late crescendo murmur and mild MR usually have favourable prognosis
  • LA enlargement increases the risk of AF
  • MR unlikely to affect performance unless it is relatively severe
  • major negative prognostic indicators:

– moderate to severe regurgitation

– endocarditis – Ruptured chordae tendineae (RCT)

– flail leaflet – severe valvular thickening

– increased TR velocity – concurrent PA dilatation

– significant MR with AF or tachycardia

36
Q

When is it recommended that an exercise test is performed on a horse with MR?

A
  • all horses with moderate to severe MR
  • if AF becomes established
  • if MR progresses more rapidly than expected, in the absence of signs of CHF
37
Q

List the common causes of AR in horses

A

Most frequently detected:

  • degenerative valve thickening
  • aortic valve prolapse

Other causes:

  • congenital malformations - leaflet tearing
  • infective endocarditis - valvulitis
  • fenestrations - aortic root disease
38
Q

List the significance of a diagnosis of AR in horses

A
  • AR often mild and associated with normal performance and life expectancy
  • when AR is moderate to severe or first recognised in a younger horse (<10 years), the risks for reduced performance life and longevity are higher
  • fatal VA has been observed in horses with moderate to severe AR and can occur in isolation without a history of poor performance or CHF

LAIM Test (20 decks)

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