Chapter 40 - ventricular failure & myocardial infarction

Question 1

Difference between definition of heart failure and circulatory failure

Answer 1

Pathophysiologic state in which the heart is unable to pump sufficient blood to meet metabolic demands of the tissue and maintain arterial & venous blood pressure versus when the delivery of oxygenated blood is insufficient to meet the metabolic demands of the body tissue.

Question 2

Give examples of primary and secondary ventricular failure

Answer 2

primary (genetic, idiopathic):
DCM (left)
ARVC (right)

secondary:
PDA or VSD leading to left volume overload
severe valvular disease w/ systolic dysfunction
tachycardia-induced (sustained >180bpm for >3wks)
malnutrition (taurine, L-carnitine, vit E/selenium)
toxic myocarditis (doxorubicin)
sepsis
hypothyroidism
infectious myocarditis (tick borne disease, chagas disease, parvo)
sepsis

Question 3

How do you take a VHS? What are normals in dogs and cats?

Answer 3

measure short & long axis, measure no. of vertebrae on R lat from cranial border of 4th thoracic, add together. <8.0 in cats

Question 4

Describe Starling’s curve (SV versus preload) in a normal heart and a heart with ventricular failure.

Answer 4

normal: increase in preload leads to increase in stroke volume until a certain point, when preload plateaus and then declines with excessive preload

VF: overall reduced stroke volume with more modest increase in stroke volume, earlier plateau

Question 5

Describe Laplace’s law - clinical implications?

Answer 5

wall stress = [pressure x radius] / 2 x [wall thickness]

increases can by seen due to increased volume and increased pressure

increased wall stress = increased myocardial energy requirements

Question 6

is positive inotropic support indicated in ventricular failure in feline HCM? why/why not?

Answer 6

no - most cats present in CHF due to diastolic failure, contraindicated

Question 7

first thing to rule out in cats with forward failure and hypotension in the absence of congestive heart failure?

Answer 7

hypovolemia

Question 8

mechanism of action of pimobendan

Answer 8

inodilator
calcium sensitizer (positive inotrope)
phosphodiesterase 3 inhibitor - increased intracellular cAMP --> phosphorylation of protein kinases --> opens calcium channels --> increased influx of calcium from sarcoplasmic reticulum in phase 2 (plateau phase) of cardiac action potential - increased contraction (inotropy) (also increased lusitropy and vasodilation)

Question 9

Why is prophylactic antiarrhythmic therapy contraindicated in the absence of arrhythmias in animals with signs of ventricular failure?

Answer 9

all antiarrhythmics are proarrhythmic

Question 10

Which of the following causes of ventricular failure have the potential to be reversible?
tachycardia-induced cardiomyopathy
sepsis induced myocardial dysfunction
nutritional deficiency
doxorubicin toxicity

Answer 10

all but doxorubicin

Question 11

This is a term for a defect in the filling or relaxation function of the heart.

Answer 11

Diastolic heart failure

Question 12

The clinical syndrome that results when abnormal cardiac function causes accumulation and retention of fluid, resulting in signs of congestion and edema.

Answer 12

CHF

Question 13

The pathophysiologic state in which the heart is unable to pump sufficient blood to meet the metabolic demands of the tissue while maintaining normal arterial and venous pressures.

Answer 13

Heart failure

Question 14

Name a cause of forward heart failure.

Answer 14

DCM

Question 15

Name 2 primary causes of ventricular/ systolic failure.

Answer 15

DCM, ARVC

Question 16

T/F: Most cats that present with CHF have underlying systolic failure.

Answer 16

False, they do not

Question 17

T/F: Chronic, sustained tachycardia can also result in LV dysfunction and CHF.

Answer 17

True

Question 18

T/F: Sepsis can lead to myocardial depression.

Answer 18

True

Question 19

T/F: ECG provides no information regarding systolic function.

Answer 19

True

Question 20

If you have left sided heart disease, what may change on your ECG?

Answer 20

Tall R waves indicative of increased LV mass

Question 21

What is the gold standard for diagnosis of systolic failure?

Answer 21

Echo

Question 22

Using Starling’s curve, in a patient with ventricular failure, what happens to the overall curve in comparison to the normal heart?

Answer 22

The curve shifts downward

Question 23

How do you calculate wall stress?

Answer 23

(Pressure x radius)/ (2 (wall thickness))

Question 24

What are the body’s two main compensatory mechanisms for cardiac dysfunction that results in fluid retention?

Answer 24

Increase preload and sympathetic stimulation to increase HR and cardiac output

Question 25

Dobutamine’s mechanism of action?

Answer 25

Potent non-selective B agonist (moreso B1)

Question 26

What is a side effect of dobutamine?

Answer 26

Some peripheral vasodilation

Question 27

What is the mechanism of action of dopamine at high doses?

Answer 27

Concurrent alpha stimulation that results in peripheral vasoconstriction