UNIT 3 CV 🫀 Flashcards
Define chronotropy
HR
Chronotropy refers to the heart rate and how it is influenced by various factors.
Define inotropy
Strength of contraction (contractility)
Inotropy describes the force of heart muscle contraction.
Define dromotropy
Conduction velocity (how fast the AP travels per time)
Dromotropy relates to the speed at which electrical impulses propagate through the heart.
Define lusitropy
Rate of myocardial relaxation (during diastole)
Lusitropy indicates how well the heart muscle relaxes after contraction.
What is the function of the sodium-potassium pump?
Maintains cell resting potential, removes Na+, returns K+
The sodium-potassium pump is crucial for maintaining the negative resting potential of cells, particularly in cardiac myocytes.
List the 5 phases of ventricular AP
Phase 0: depolarization (Na influx)
Phase 1: initial repolarization (K efflux, Cl influx)
Phase 2: plateau (Ca influx)
Phase 3: repolarization (K efflux)
Phase 4: resting membrane potential restoration
These phases describe the electrical activity during a cardiac action potential.
List the 3 phases of SA node AP
Phase 4: spontaneous depolarization (leaky to Na)
Phase 0: depolarization (Ca influx)
Phase 3: repolarization (K efflux)
The SA node’s action potential is crucial for initiating the heartbeat.
What determines the intrinsic HR?
Rate of spontaneous phase 4 depolarization in the SA node
This rate can be influenced by various physiological factors.
What is the calculation for MAP?
MAP = (1/3 x SBP) + (2/3 x DBP)
MAP is a critical parameter for assessing perfusion pressure.
What is the formula for SVR?
([MAP – CVP) / CO] x 80
SVR indicates systemic vascular resistance.
What is the formula for pulmonary vascular resistance?
[(MPAP – PAOP) / CO] x 80
This formula helps assess the resistance in the pulmonary circulation.
Describe the Frank-Starling relationship
Relationship between ventricular volume (preload) and output (CO)
It states that increased preload leads to increased cardiac output until a certain point.
What factors affect myocardial contractility (inotropy)?
Chemicals affecting contractility, particularly calcium
Contractility can be altered by various substances that influence calcium levels.
What is afterload?
The force the ventricle must overcome to eject its stroke volume
Afterload is an important determinant of cardiac performance.
What law describes ventricular afterload?
Law of LaPlace
This law relates wall stress to intraventricular pressure, radius, and wall thickness.
List 2 conditions that set afterload proximal to the systemic circulation
- Aortic stenosis
- Coarctation of the aorta
These conditions increase the workload on the heart.
What are the 6 stages of the cardiac cycle?
- Atrial systole
- Isovolumetric contraction
- Ventricular systole
- Isovolumetric relaxation
- Ventricular filling
- Atrial diastole
These stages describe the sequence of events during one heartbeat.
How do you calculate ejection fraction?
EF = (SV / EDV) x 100
Ejection fraction measures the percentage of blood ejected from the heart during systole.
What is the best TEE view for diagnosing myocardial ischemia?
Midpapillary muscle level in short axis
This view provides optimal visualization of the left ventricle.
What is the equation for coronary perfusion pressure?
Coronary PP = aortic DBP – LVEDP
This equation is essential for understanding blood supply to the myocardium.
Which region of the heart is most susceptible to myocardial ischemia?
LV subendocardium
This area is particularly vulnerable during diastole due to its blood supply dynamics.
What factors affect myocardial oxygen supply and demand?
Discuss the nitric oxide pathway of vasodilation
NO synthase catalyzes L-arginine to NO, which activates guanylate cyclase, increasing cGMP and causing smooth muscle relaxation
This pathway is crucial for vascular regulation.
What are the two primary ways a heart valve can fail?
- Stenosis
- Regurgitation
These failures can lead to significant hemodynamic consequences.