Lecture 8 8/29/24 Flashcards
What is heart failure?
clinical syndrome in which impaired emptying or filling of the heart causes clinical signs of exercise intolerance and/or congestion
What happens when cardiac performance declines?
compensatory mechanisms are activated in order to preserve perfusion pressure and cardiac output
What are the priorities of the cardiovascular system that are preserved in the event of cardiac performance decline?
–systemic arterial pressure
-cardiac output
-venous pressures
What are the results of the cardiovascular compensatory mechanisms?
-vasoconstriction
-increases in inotropic state
-retention of salt and water
How does vasoconstriction help to preserve blood pressure?
BP = CO x VR; therefore, when cardiac output falls, a rise in vascular resistance can maintain blood pressure
What is eccentric hypertrophy?
-response to volume overload
-hypertrophy and lumen dilation
-wall thickness is normal compared to lumen size
What is concentric hypertrophy?
-response to pressure overload
-hypertrophy without lumen dilation
-wall thickness is increased compared to lumen size
What is the Frank-Starling Law of the Heart?
kidneys retain salt and water as a compensatory mechanism
What are the peripheral compensatory mechanisms during heart failure?
-activation of adrenergic nervous system
-activation of renin-angiotensin-aldosterone system
-other endocrine products
What are the functions of angiotensin II?
-vasoconstriction
-modulation of ANS/increase in sympathetic tone
-dypsogen release/increase in thirst
-stimulation of aldosterone release
-stimulation of ADH release
Why is CHF considered to have unstoppable progression?
activation of the compensatory mechanisms is only favorable in the short term; long term, activation of ANS and RAAS has detrimental effects
What do the physical findings in an animal with stage C heart failure typically reflect?
-causative disease
-consequences of congestion
-sympathetic activation
How does respiratory sinus arrhythmia relate to CHF?
the presence of RSA is virtually incompatible with a diagnosis of CHF
What are the main strategies of heart failure therapy?
-manipulation of the four main determinants of cardiac output
-treatment of neuroendocrine abnormalities
How can preload be reduced?
-diuretics; i.e. furosemide
-venodilators, i.e. nitroglycerin
What is important about preload reduction with diuretics such as furosemide?
progression of heart failure requires adjustments in the medication dosage
What are the mechanisms behind diuretics decreasing preload?
-increased urine production, altering water balance and decreasing intravascular volume
-decrease in intravascular volume decreases venous pressures so the lymphatic system can clear excess tissue fluid
What are the characteristics of furosemide?
-can be given PO, SQ, IM, or IV
-rapid onset of action when given IV
-generally administered every 12 hours when given orally as at-home therapy
What are the adverse effects of furosemide?
-hypovolemia
-pre-renal azotemia
-electrolyte derangements
