2: Lecture 3 Flashcards
What is the acute phase of heart failure?
Pulmonary embolism
First cause of congestive heart failure?
Left ventricular dysfunction
Failure of left ventricle impedes delivery of oxygen to the whole body
How to treat Left ventricular dysfunction
With positive ionotropic agents that increase contraction ability of heart to reestablish circulation
Second cause of congestive heart failure
Neuroendocrine activation involving the renin-angiotensin-aldosterone system
Can lead to pathological hypertrophy of heart (increase in size) with decrease in contractility and reduction of stroke volume (extra tissue is not cardiac muscle)
(physically hypertrophy is when extra tissue is heart muscle as seen in pregnant women and athletes)
What is systolic heart failure
When left ventricle (or sometimes right) cannot contract properly to eject blood due to weakened muscle
This causes a decrease in stroke volume
Occurs in patients after heart attacks
What is an ejection fraction
Measure of how much blood leaves the heart during contraction
Low in systolic heart failure
Used for diagnosis of heart failure (under 40%, 50-70% is healthy)
What is diastolic heart failure
A deficit in the filling capacity of the heart (resulting in less blood being ejected with each contraction)
Can have normal ejection fraction
Has reduced preload–>less distension on ventricle walls–>lower diastolic volume–>lower stroke volume
Main cause of diastolic heart failure
Narrowing of the ventricle lumen
Can occur from long-standing hypertension causing cardiac hypertrophy and a reduction in ventricular volume (smaller ventricle lumen)
Frank Starling Law
Healthy: small increase in preload–>large increase in stroke volume
Cardiovascular disease: increase in preload–>small increase in stroke volume
Heart attack: any size preload–>very low stroke volume
Factors that contribute to heart failure
Uncontrolled hypertension
Diabetes
Myocardial infarction (damage to heart muscle from scar tissue formation)
Valve dysfunction (heart valves don’t close properly causing backflow that inhibits heart contraction)
Viral myocarditis (infection of heart tissue)
Primary effects of Heart failure
Reduced cardiac output (to compensate for increase blood pressure/hypertension)
Compensation is by an increase sympathetic drive and salt and water retention
Problematic as eventually increases systolic and diastolic blood pressure (makes heart tire more easily)
Long term effects of heart failure
Remodeling of the heart (to compensate for heart’s inability to pump blood)–>pathological hypertrophy
Effects of Pathological hypertrophy
Leads to apoptosis of the cardiomyocytes and decrease in the number of cardiac muscle cells (forming a positive feedback loop)
What is cardiac Preload
Pressure in the atrium determined by amount of blood entering
Increased in heart failure and treated with salt reduction and diuretics
What is cardiac Afterload
Vascular resistance
Afterload is increased due to reflex sympathetic outflow and renin-angiotensin system
Increased afterload may reduce cardiac output
Treatment for decrease on contractility of heart (during heart failure)
Ionotropic drugs will work directly on heart to increase contractility to restore pump performance
Why does Heart rate increase during heart failure
sympathetic nervous system compensation to restore systemic blood flow
How does body detect reduced cardiac output
Through reduction in carotid sinus firing (baroreceptors) and reduction in renal blood flow
Response to decrease in baroreceptor signaling
Increase in sympathetic discharge from hypothalamus
Increase in force of contraction, heart rate, preload, and afterload
Response to decrease blood perfusion of the kidneys
Increase in angiotensin II release
Increase preload and afterload on heart, also lead to hypertrophy
Main action of positive ionotropic drugs
Work directly on muscle to increase force of contraction
Main action of ACE inhibitors
Reduce action of angiotensin II
Main action of Diuretics
Reduce the preload and afterload by reducing blood volume
Main action of Vasodilators
Reduce Preload and afterload by reducing arterial resistance
