MHD: Congestive Heart Failure Flashcards
What are the major determinants of cardiac performance?
Heart rate
Preload
Afterload
Contractility
What effect does Ca2+ levels have on contractility
Ca2+ levels are the main determinant of contractility
More calcium, more contractility
How is ejection fraction calculated?
(EDV-ESV)/EDV x 100
What percent of the blood in the ventricle gets ejected each beat?
Diastolic filling is most closely related to what parameter of cardiac performance?
Diastolic filling is quantified by preload
More filling, increased stretching, increased stroke volume
What is the definition of afterload?
Impedance to ejection of blood
What are the general causes of congestive heart failure?
Impaired contractility
Increased afterload
Impaired ventricular relaxation/decreased filling
What is the difference between HFrEF and HFpEF?
Ejection fraction preservation.
r = reduced EF
p = preserved EF
How do SV and EDV change in HFrEF and HFpEF?
HFrEF: decreased SV, increased EDV
HFpEF: decreased SV, decreased EDV
Which side of the heart fails more easily?
Right: More compliant than left, very susceptible to acute changes in pulmonary vascular resistance
What can cause right sided heart failure?
Cardiac causes: LV failure, mitral stenosis/regurg, acute MI with RV infarct, pulmonic stenosis
Pulmonary parenchymal diseases: COPD, ARDS, fibrosis
Pulmonary vascular diseases: PE, pulmonary HT
What are the compensatory mechanisms to maintain cardiac output in CHF?
Frank-starling mechanism
Autonomic NS: baroreceptors
Renal: RAA system
Ventricular remodeling
Are compensatory mechanisms beneficial, or pathological?
Yes.
Initially, they help but can ultimately lead to decreased performance
Describe the vicious cycle associated with congestive heart failure
Ventricular performance decreases, leading to decreased CO. Decreased CO is compensated for by a variety of mechanisms including increased systemic vascular resistance. This increases afterload on the heart, which further decreases ventricular performance.
What is the time-course for ventricular remodeling following MI?
Acute changes occur within seconds
Infarct expansion occurs over hours-weeks
Hypertrophy and dilatation occurs over week-years
What is the difference between concentric and eccentric hypertrophy?
Concentric: decreased chamber size due to increased wall thickness
Eccentric: dilated chambers with ~normal wall thickness
