Cardiovascular Physiology EC Flashcards
What are two ways to calculate cardiac output
CO=HR * SV
CO= O2 consumption / (arterial O2 - venous O2)
What are two ways to calculate mean arterial pressure?
MAP= CO * TPR
MAP= 2/3 diastolic + 1/3 systolic
How do you determine ejection fraction?
EF= SV/EDV
How do you determine cardiac flow, resistance, and pressure?
P=Q*R (like Ohm’s law)
Normal splitting
S2 is split during inspiration (normal)
w/ inspiration, venous return increases, increasing RV ejection time, and delaying closure of pulmonic valve
Wide splitting
Seen with delayed RV emptying (ie pulmonary stenosis)
Delay in RV emptying causes delayed pulmonic sound regardless of breath. Exaggeration of normal splitting
Fixed splitting
Seen in ASD
Left to Right shunt, Increased right side volume, regardless of breath pulmonic valve closure is delayed.
Paradoxical splitting
Seen in delayed LV emptying (ie aortic stenosis)
Normal order reversed so pulmonic closes first. On inspiration, P2 moves closer to A2, eliminating split on inspiration.
Phase 0 of ventricular action potential
Rapid upstroke - voltage gated Na channels open
Phase 1 of ventricular action potential
Initial repolarization - inactivation of voltage-gated Na channels, Voltage gated K channels reopen.
Phase 2 of ventricular action potential
Plateau - Ca influx balances out K efflux
Phase 3 of ventricular action potential
Rapid repolarization - massive K efflux and closure of Ca channels
Phase 4 of ventricular action potential
Resting potential - high K permeability
Phase 0 of pacemaker action potential
Upstroke - opening of voltage-gated Ca channels. (fast Na channels permanently inactivated due to less negative resting potential)
Phase 3 of pacemaker action potential
Inactivation of Ca channel and increase K efflux
Phase 4 of pacemaker action potential
Slow diastolic depolarization - slow depolarization due to Na conductance
What does the P wave on and ECG represent?
Atrial depolarization
What is the PR interval on an ECG?
Conduction through the AV node (<200msec)
What is the QRS complex on an ECG?
Ventricular depolarization (<120msec)
What is the QT interval on an ECG?
Mechanical contraction of ventricles
What is the T wave on an ECG?
Ventricular repolarization
What is the ST segment on an ECG?
Isoelectric, ventricles depolarized
What is the U wave on an ECG?
Caused by hypokalemia and bradycardia
