Cardiology NMS Flashcards
What is CHF
the inability of th heart, working at normal or elevated filling pressure, to pump enough blood to meet the oxygen requirements of the body tissues.
Its a syndrome of disorders, not a diagnosis
Systole is governed by what 3 cardiac properties
Contractility
Afterload
preload
What is preload
the sarcomere stretch before contraction
What property of dysfunction is associated with most cases of CHF
decreased contractility
What are the causes of decreased contractility
- MI: portion of the mycardium undergoes necrosis and can no longer generate force
- Valvular heart disease: stenosis or regurgitation
- Hypertension
- Cariomyopathies
How can afterload be quantified
Stress = (pressure x radius) / (2 x thickness)
What is the frank-starling mechanism
Increased end diastolic volume increases sarcomere stretch (preload), which increases the number of systolic actin-myosin cross-bridges that develop. Greater number of cross-bridges, the greater the force of contraction.
What governs diastolic function
active and passive properties
What is the active property of diastolic function
Active relaxation occurs early in diastole as calium is pumped out of the myocardium, resulting in the near cessation of actin myosin cross bridge interaction
What is the passive property of diastole
passive filling occurs as the mitral valve opens, allowing the blood stored in the atria to fill the ventricles
What is the formula for stiffness
(delta P) / (delta V)
What causes an increased in stiffness
Hypertension
Amyloid
What are the types of heart failure
- HIgh output HF
- Left sided failure
- Right sided failure
What are some causes of high output HF
- Chronic severe anemia
- AV fistula
- beriberi
Discuss how chronic anemia leads to high output HF
Chronic severe anemia has a reduced oxygen carrying capacity
- Compensation is provided by increased forward cardiac output, which is facilitated by cardiac enlargement, decreased total PVR and increased venous return: leads to Volume overload
- Eventually the demands on the heart lead to cardiac failure; cardiac output, although high, still is not adequate to meet the circulatory demands placed on the heart by the anemia.
What three things will lead to volume overload
- .Cardiac enlargement
- Decreased PVR
- Increased venous return
What is the most common cause of Right sided failure
left sided failure.
COPD, PE, pulmonary HTN are also common in the absence of a left sided failure
What are the symptoms of CHF
- Dyspnea (most common)
- Orthopnea
- Paroxysmal nocturnal dyspnea
- Nocturia
- Edema
How does CHF cause nocturia
develops in CHF as a result of increased renal blood flow when the patient is recumbent and asleep.
a. During the day when the skeletal muscles are active, limited cardiac output is shifted away from the kidney toward the skeletal musculature. The kidney interprets this reduction in blood flow as hypovolemia and becomes sodium avid via activation of the renin angiotensin system.
b. During night, when the patient is at rest, cardiac output is shifted toward the kidney, and diuresis ensues.
When is peripheral edema is cardiac related, is it caused by right or left failure
RIGHT SIDE
What causes edema associated with cardiac
systemic hydrostatic venous pressure is greater than the systemic oncotic pressure.
What are the physical signs of CHF
not sure
