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Know how to read a basic EKG
- P = firing of SA node/ depolarization of atria (.06-.12 sec) (PR interval = .12-.20)
- QRS = depolarization of AV node of ventricles (.04-.12 sec)
- T = repolarization of ventricles (QT interval = .31-.38)U = delayed ventricular repolarization OR hypokalemia
- Times between these waves IMPORTANT!
- R to R interval = pulse rate and should be equal
What affects cardiac output?
- ANS = affects HR
- Preload = ventricular volume at end of diastole (SV)
- --Starling’s Law: elasticity of heart will increase SV until it stretches so much that elasticity fails and SV will plummet.
- Contractility = increases ventricular emptying
- --Norepinephrine/ Epi by SNS (raises SV)
- Afterload = peripheral resistance
- --Affected by size of ventricle, wall tension & BP
- Cardiac Reserve = ability to respond to demands
- --HR of 180 bpm for short periods
- --Raise in SV by increasing preload or contractility
Cardiac function markers
- C-reactive protein
- Homocysteine: Both of these are markers for inflammation.
- BNP: How much ventricles are stretching.
- ANP: How much atriums are stretching.
- --Both are markers for heart failure.
- CK-MB/Myoglobin/Troponin: Muscle function markers.