Cardio. 38.

Question 1

Define heart failure

Answer 1

heart’s inability to meet the metabolic
needs of peripheral tissues, or instances when the heart can only do so in the presence of increased venous filling pressures.

forward failure (poor CO), backwards failure (congestion)

Question 2

primary trigger for activation of the RAAS

Answer 2

inability to provide normal renal perfusion. Decreased renal blood flow and Cl delivery to DCT induces renin
release from the macula densa.

Question 3

End result of RAAS activation in CHF

Answer 3

Fluid retention (which promotes development of CHF) and mal-adaptive myocardial and vascular remodeling

Question 4

SNS acute vs. chronic in heart failure

Answer 4

Acute response adaptive, chronic maladaptive –
SNS activity ultimately leads to further cardiac damage

humans with heart disease, increased NE significant
risk factor for mortality

Question 5

Myocardial tissue produces two main hormones that induce natriuresis, diuresis, and vasodilation:

produced primarily in response to:

Answer 5

These so-called natriuretic peptides:
atrial natriuretic peptide (ANP)
B-type natriuretic peptide (BNP)

stretch or stress of myocardial tissue
serves as a counterregulatory system to RAAS & SNS

overwhelmed in heart disease

Question 6

ET-1:
name:
produced by:
in response to (3):
causes:

Answer 6

Endothelin 1 is a potent vasoconstrictor
produced by vascular endothelial cells
response to sheer stress, angiotensin II, and CKs

increases cardiac afterload
elevated in dogs and cats with heart failure
> afterload &alters normal calcium cycling within muscle cells and is directly toxic to myocardiocytes

Question 7

Arginine vasopressin ADH MoA:

ADH activation results in:

Answer 7

increases reabsorption of free water within DCT & CT
activation closely resembles that of the RAAS and SNS

fluid overload, CHF, and dilutional hyponatremia

Question 8

Describe dilutional hyponatremia and the hormone involved:

Answer 8

heightened free water retention to the extent that serum sodium concentrations are decreased, despite an overall excess of body-wide sodium.
ADH
both humans and veterinary patients, dilutional hyponatremia is a marker of severe neurohormonal activation and is a poor prognostic sign

Question 9

List three maladaptive responses in heart failure following neurohormonal activation :

Answer 9

Myocardial remodeling
ABNORMAL Ca++ handling
ABNORMAL myocyte energy production

Question 10

response to pressure overload vs response to volume overload:

i.e.

Answer 10

pressure - hypertrophy sarcomeres replicate in parallel
volume - elongate - sacromes replicate in series

SAS, hypertension -conentric hypertrophy
MMVD - eccentric hypertrophy

Question 11

Cardiac hypertrophy consequences:

Answer 11

concentric: increased myocardial oxygen demand
ischemia, fibrosis, collagen disruption, and injury to small coronary vessels

eccentric: increased myocardial wall stress,
myocyte injury or necrosis, and myocyte slippage

Question 12

Describe path of Ca++ in an action potential:

Answer 12

• calcium ions enter vis L-type channel in T-tubules (terminal cisterna)
• Ca sensed at feet of RyR receptor triggers release of additional calcium ions from sarcoplasmic reticulum [SR]
• Ca stored in the SRs flows through the RyR ryanodine channel
• binds to troponin C located on the actin and myosin complex (concentration dependant manner)
• conformation change exposing myosin head
• myosin binds to actine - ATP hydrolysis
• “ratcheting contraction”
• ATP dependant release of Ca
• calcium ions are quickly sequestered into the SR
• via ATPase (SERCA) channel

Question 13

phospholamban

Answer 13

help regulate the reuptake of Ca++ by DECREASING/inhibiting SERCA

Question 14

myocardial energy source in CHF

Answer 14

heart can utilize both glucose and free fatty acids
In cases of heart failure, the heart preferentially
uses glucose, which requires less oxygen to metabolize

Question 15

CHF occurs at what pressure?
pulmonary venous congestion (left sided):
systemic venous congestion (right sided):

Answer 15

Pulmonary venous pressures greater than 25 mm Hg

systemic venous pressures greater than 20 mm Hg

Question 16

severe myocardial dysfunction = fail forward (rather than congestion), describe…

Answer 16

severe myocardial dysfunction, cardiac performance is insufficient to provide adequate CO and animals present with signs of low-output heart failure
-C/S: weakness, depressed mentation, cardiac shock,
and syncope

Question 17

CHF predominantly left- or right-sided failure or occasionally:

Answer 17

biventricular failure

Question 18

Common causes of left-sided heart failure:

Common causes of right-sided heart failure

Answer 18

dog - PDA, MMVD, DCM
cat - HCM restrictive cardiomyopathy

dog - DCM, TR (congenital of degenerative), PH
cats -rare

Question 19

Frank-Starling mechanism describes:

Answer 19

fundamental relationship between what is put into the heart (i.e., preload) and what comes out of the heart (i.e., cardiac output)

• increase in the initial volume or pressure (preload) within the ventricle increases the strength of the subsequent ventricular contraction
• Thus, up to a physiologic limit, preload and contractility are positively associated