Module 2 - Heart Failure Flashcards
Cardiac Output
the amount of blood pumped out of the left ventricle in one minute
HR X SV = CO
litres/min
Heart Rate is determined by ?
pacemaker cells
sns
pns
circulating hormones
Stroke volume
the amount of blood pumped from the ventricle in a single beat
Stroke volume calculation
SV = EDV - ESV
Cardiac index
used to compare cardiac output of different individuals
Cardiac output (L/min) / body surface area (m^2)
Cardiac index is abnormal outside of what range?
2.5 - 5.0
Stroke volume is determined by 3 variables
preload, afterload and myocardial contractility
preload
passive tension created in the myocardium before contraction
depends primarily on venous return
represented by atrial pressure
afterload
the resistance against which the heart must push blood out and into the arteries
myocardial contractility
the tension that is developed within the muscle on contraction independent of it’s original length (at the end of diastole)
ejection fraction
the proportion of the end diastolic volume (EDV) expelled in each beat
usually this varies between 55-75%
mean = 65%
CHF
a complex of signs and symptoms that arrises when HF occurs
Causes of HF (6)
1) heart cannot pump hard enough to overcome (incr afterload)
2) increase in volume of blood to be pumped (incr preload)
3) impairment of atrial emptying
4) reduced myo contractility - impaired systolic function
5) reduced myo relaxation - impaired diastolic function
6) incr. demand for blood by tissues (high output failure)
Classifications of HF
Low Output Failure
most common
output falls below normal and can’t meet minimum criteria for body, even at rest
causes: arrhythmias, myo ischemia, and MI
Classifications of HF
High Output Failure
body requires more oxygen and heart can’t provide enough oxygenated blood
causes: pregnancy, exertion at high altitudes
Classifications of HF
Forward Failure
explains the effects of heart failure by the reduced tissue perfusion that occurs and by the adaptations that are brought into play to compensate for it.
Classifications of HF
Backward Failure
heart cannot efficiently pump the blood delivered to it
ie: broken mitral valve? blood backs up in LA - signs of backward failure
Classifications of HF
Left Heart Failure
most common; b/c this is a higher pressure/work zone
common causes: MI, hypertension, and valve disease
blood backs up in LA and in to pulmonary system
pulmonary capillary wedge pressure (PCWP)
catheter is placed in pulmonary artery circulation to measure the pressure
this pressure is approx LA pressure
orthopnea
difficulty breathing when lying down
cheyne stokes respiration
alternating periods of apnea and hyperventilation
Classifications of HF
Right Heart Failure
very rare to occur on it’s own
most frequent cause is cor pulmonale (hypertrophy of the RV associated w/ primary lung disease)
2nd most freq cause: pulmonary emboli (block)
Causes of High Output Failure
hyperthyroidism Paget’s disease chronic anemia renal failure arteriovenous shunts
arteriovenous shunts
an abnormal connection between an artery and a vein
Clinical presentation of Right Heart Failure
not much pulmonary edema/congestion systemic venous congestion hepatic and splenic enlargement peripheral edema (swelling in tissues) ascites
