A general overview, and sometimes incomplete outline, of the things I know about hearts. This is how I structure info in my brain, and I thought it might be useful to other folks.

1. Hearts!
Stars and horseshoes to come . . .

2. Cardiac Output: the minute volume of the
heart
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Stroke volume x heart rate
Normal resting left ventricular stroke volume= 70 mL
Normal resting heart rate 70 bpm
Normal left ventricular cardiac output= 4900 mL

3. Things you can mess with
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Squeeziness (inotropy), relaxiness (loositropy),
speediness (chronotropy), and electricaliness
(dromotropy).

4. The measurable components of the heart
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The mechanical beating of the heart (measured by
peripheral pulses)
The electrical conduction of the heart (measured by
EKG)
And the perfusion of the heart muscle (measured by
diastolic pressure)

5. Depolarization: your electrical system

6. Syncitia! They makes depolarization weird

7. Blockers! You can mess with depolarization
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Four classes of antiarrhythmics:
Class I: Sodium channel blockers (Lidocaine)
Class II: Beta Blockers (Propanolol)
Class III: Potassium channel blockers (Amiodarone)
Class IV: Calcium channel blockers (Diltiazem)

8. Pressors
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The opposite of beta blockers
Used for low blood pressure in the absence of
hypovolemia
Dopamine commonly used in EMS
Dopamine’s effects are indirect, though
Epinephrine can be used. Much more direct
Norepinephrine can be administered by a physician

9. EKGs
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Are a lot more complicated than everyone makes them
out to be.
But you don’t have to understand how they work to use
them.
You only have to resort to the metrics that define a
rhythm when it’s not obvious.
Obviousness comes with seeing lots of rhythms.

10. EKG

11. Hearts, as seen by Warren Budd
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Electrolyte dysrhythmias
Infectious Etiologies
Decreased perfusion
Aneurysm
Conduction abnormalities
Myocardial weakness
Pericardial effusion/tamponade

12. Your heart uses blood
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And if that blood’s electrolytes are wonky, that can cause
depolarization changes
Some are easy to see on an EKG and hard to determine
clinically
Hyper/hypo -calcemia, -magnesemia, -kalemia, -natremia

13. Heart muscle can get tired, too
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The way your skeletal muscles get tired is by decreased
ability to oxygenate the muscle and offload CO2
Your heart muscle doesn’t overwork, it just underperfuses.
Hypoperfusion is caused by blockages in the arteries that
feed the muscle.
That muscle will accumulate lactic acid as it works
anaerobically, causing angina pectoris
Eventually that muscle will die (or infarct), leading to a
myocardial infarction, or ‘heart attack.’
Once 70% of this ventricular muscle is dead, heart failure
is imminent.

14. Aneurysm (dissection)
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Just a defect in the wall of a vessel
The medical relevance of this is either dissection or
rupture
A dissection of an aneurysm is when the inner layer of
the blood vessel (tunica intima) peals away from the rest
of the vessel (usually at the tunica media, the muscular
layer)
This flap of tunica intima can force blood into the space
between the tunica intima and the tunica media, creating
a “false lumen.”
This false lumen can grow big enough to occlude the real
lumen, causing decreased or absent perfusion to vessels.

15. Aneurysm (rupture)
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A ruptured aneurysm is much more obviously
catastrophic.
The vessel bursts, pouring blood into the interstitium.
While this can bleed can eventually tamponade itself with
hydrostatic pressure, it normally does so to the
detriment of the tissues around it.
In the brain, this means death
In the abdomen, the cavity too big to fill, so the
hydrostatic pressure of the peritoneum never gets high
enough to tamponade the artery and results in bleeding
to death (exsanguination).

16. Conduction abnormalities
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Electrical impulses and change in the polarity of
myocardial cells are what causes the heart muscle to
contract.
There’s a set route on which these impulses travel.
Impulses can go the wrong way sometimes, which is less
efficient, leading to the heart beating inefficiently.
There are places that this goes wrong much more
frequently than others, like the Bundle of Kent.
The result is an abnormal rhythm, which may not perfuse
the brain.

17. Myocardial weakness
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You heart muscle has an optimum range in which it
contracts most forcefully
If your blood pressure is too high, it will stretch heart
muscle past that range
This will weaken the heart muscle, causing it to beat
irregularly, or to dilate
This eventually leads to blood “backing up the system.”
It most frequently back up into the lungs, causing
pulmonary edema,
And the feet, causing pedal edema
It does it other areas in the body as well, but the feet
have gravity and distance working against it.

18. Pericardial Tamponade
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If the sack that holds your beating heart fills with blood
or pus, (pericardial effusion) then your heart will not be
able to relax to its full size and fill the ventricles all the
way.
This decreases the amount of blood you can pump.
The only definitive treatment for this is to drain
pericardial sac
Which can be done by a needle (pericardiocentesis)
Or by cracking the chest open, grabbing the heart,
knicking a hole in the sack, and squeezing (expressing)
the fluid (open thoracotomy)

19. Your heart can be infected
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Just like every other tissue in the body
Pericarditis
Myocarditis
Endocarditis

20. Pericarditis
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ST elevation in literally every lead.

21. Myocarditis

22. Endocarditis
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Vegetation can grow on valves, acutely causing a new
heart murmur
Occurs in IV drug users

23. Murmurs: an art in appreciation
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Murmurs are funny sounds your heart makes when blood
rushes through various apertures when it shouldn’t
There are systolic murmurs and diastolic murmurs
Systolic murmurs are caused my stenosed valves
Diastolic murmurs are caused by prolapsed valves
They can occur at any of the four valves (bicuspid,
tricuspid, pulmonary, and aortic)
There are also murmurs caused by malformations in the
heart (atrioseptal defects, vetriculoseptal defects)

24. Tachycardia Algorithm

25. Bradycardia Algorithm