Week 2 - Intro to Cardiac Disease Flashcards
What are the two categories of heart disease?
Congenital
Acquired (most cases)
List 5 primary causes of acquired heart disease?
Chronic degenerative valve disease
Cardiomyopathy
Endocardial infection
Pericardial disease
Rate/rhythm abnormalities
What is the hearts main goal?
To maintain blood pressure and perfusion by:
1. Normal systemic arteriole pressure
2. Cardiac output (HV x SV)
3. Venous pressure remain equal
What is blood pressure impacted by?
Vascular resistance - force exerted on the blood by the vasculature
Cardiac output
What are the three things that affect stroke volume?
Preload - the volume of blood/hydrostatic pressure within the ventricles at the end of diastole (when finished filling)
Afterload - pressure the heart works against to open the aorta in systole (main factor = arteriole blood pressure)
Contractility
Heart failure can be acute or chronic, which is the most common?
Chronic - usually degenerative conditions
Acute is rare
In simple terms, what is the first thing that happens in heart failure?
Cardiac output falls
Detected as a fall in blood pressure
How do the following conditions affect cardiac output?
CDVD, DCM, HCM, Congenital
What does this mean for clinical signs?
CDVD – regurgitation means fall in FORWARD flow and CO
DCM – systolic failure – ventricles cannot contract properly - fall in stroke volume and therefore CO
HCM/RCM, ventricle cannot FILL – fall in CO
Congenital disease – if develop failure because CO fall
CLINICAL SIGNS ALL THE SAME WHATEVER THE CAUSE
What are the mechanisms that the heart uses to restore blood pressure?
BODY THINKS DROP IN CO IS DUE TO TRAUMATIC BLOOD LOSS RATHER THAN HEART DISESE -> COMPENSATORY MECHANISMS DO MORE HARM!
Sympathetic NS activation
R.A.A.S
Cardiac enlargement (last consequence)
What does the sympathetic nervous system do to try and restore blood pressure?
Increase HR (problem in heart disease)
Vasoconstriction -> increase presser (problem if not enough blood or if heart sick and needs to cope with higher pressure)
Kidney release renin
What is the consequences of R.A.A.S activation?
- Systemic vasoconstriction (increase BP with heart cannot cope with)
- Increase blood volume (increasing the fluid the body has to deal with)
- Renal sodium and fluid retention (to increase blood volume)
What are the effects of the compensatory mechanisms?
Heart rate goes up
Vasoconstriction
Contractility goes up
Salt and water retained
(Cardiac enlargement)
CO DECREASE -> COMPENSATORY MECHANISMS -> SICK HEART HAS TO COPE, NO RISE IN CO -> REPEAT CYCLE
CLINICAL SIGNS START WHEN HEART STRUGGLES AND GO INTO FAILURE
What is the problem of the compensatory mechanisms?
CO DECREASE -> COMPENSATORY MECHANISMS -> SICK HEART HAS TO COPE, NO RISE IN CO -> REPEAT CYCLE
CLINICAL SIGNS START WHEN HEART STRUGGLES AND GO INTO FAILURE
Ideal in the short terms
- sudden blood loss (e.g. trauma)
Inappropriate in long term
- worsens heart function
- treatment is to pause compensatory mechanisms (e.g. preventing the kidneys from retaining fluid)
How does an increase in heart rate and contractility affect a sick hear?
HEART RATE GOES UP
-SICK HEART WORKING HARDER
-OXYGEN NEEDS GO UP
CONTRACTILITY GOES UP
-SICK HEART WORKING HARDER
-OXYGEN NEEDS GO UP
How does vasoconstriction of arteries affect a sick heart?
Increase afterload (increase aortic pressure) = CO Falls more
Blood will take the path of least resistance -> regurgitate through valves
Increase afterload – valves leak more (fluid accumulation)
