SM 138 Heart Failure Pathophysiology Flashcards
Define Heart Failure?
Heart Failure is a syndrome where the heart: cannot produce enough CO to meet metabolic demands of the body AND/OR can only produce enough CO at the expense of increased cardiac filling pressures
What is a syndrome?
A collection of symptoms with varied underlying causes
How does HF relate to other CV diseases?
HF is the end result of most CV diseases, including IHD, HTN +/- Diabetes, Valvular Heart Disease, and Arrhythmias
How can HF have a renal basis?
HF can arise from too much Na and fluid retention in the Kidneys
Compare forward failure to backward failure in HF?
Forward failure refers to a failure to supply the heart whereas backward failure refers to a failure of the heart to pump enough blood to the body
Describe the epidemiology of HF?
30 - 35% 5 year survival after hospitalization for HF, very low
Why is the prevalence of HF rising?
Rising rates of HTN, Diabetes, and Obesity as well as better treatment of ACS and effective treatments but no cures for HF lead to increased HF prevalence
What type of dysfunction is commonly attributed to HFrEF?
Systolic dysfunction
What type of dysfunction is commonly attributed to HFpEF?
Diastolic dysfunction
What can cause systolic dysfunction in HF?
Impaired contractility and elevated afterload
What can impair contractility in HF and what type of HF does it cause?
MI, Mitral and Aortic Regurg, and Dilated cardiomyopathies can impair contractility = HPrEF
What can increase afterload in HF and what type of HF does it cause?
Aortic Stenosis and Uncontrolled HTN can increase afterload = HPrEF
How does decreasing contractility in HPrEF change the PV loop?
Decreased contractility lowers the slope of the CO line, leading to a greater ESV. Volume begins to accumulate in the ventricle, shifting to a higher point on the lower volume curve, increasing EDV and raising pressure
How does increasing afterload change the PV loop?
Increased afterload forces the ventricle to reach a higher pressure before contraction, leaving less energy to contract and causing increased ESV; blood will accumulate in the ventricle to raise EDV, and pressure in the ventricle increases
What is cachexia?
Muscle wasting due to insufficient blood supply to the body
How does HFrEF present?
Fatigue, dyspnea, exercise intolerance, hypotension, cardiac cachexia
What can impair diastolic filling in HF?
LV hypertrophy, restrictive cardiomyopathy, and fibrosis
How does impaired diastolic filling lead to HFpEF?
Impaired diastolic filling leads to decreased compliance, which shifts the diastolic pressure-volume curve on the PV loop up, leading to a mostly preserved EF but less SV due to lower EDV and higher pressures in the ventricle
How does increased LV filling pressure present in HF?
Pulmonary venous congestion that causes dyspnea, ortopnea, and PND as well as pulmonary rales
How does increased RV filling pressure present in HF?
Systemic venous congestion that causes leg swelling and bloating, as well as increased JVP
What causes increased filling pressures?
Impaired LV/RV relaxation, reduced LV/RV compliance, and fluid overload
How does systolic/contractile dysfunction relate to systolic HF?
Contractile dysfunction can manifest as decreased EF in systolic HF, but it can also be asymptomatic; contractile dysfunction =/= systolic HF
What is systolic HF?
Systolic dysfunction + signs/symptoms of HF
How does diastolic dysfunction relate to diastolic HF?
Diastolic dysfunction implies impaired relaxation or non-compliant ventricles, which may manifest as increased filling pressures; however, it can also be asymptomatic so diastolic dysfunction =/= diastolic HF
What is diastolic HF?
Diastolic dysfunction + signs/symptoms of HF
What is the definition of HFrEF in terms of EF?
EF < 40-45%
What is the definition of HFpEF in terms of EF?
EF > 45-50%
Why is “systolic HF” misleading?
Many patients with systolic HF have systolic and diastolic dysfunction
Why is “diastolic HF” misleading?
Many patients with diastolic HF have abnormalities in systolic function despite normal EF
Does the Frank-Starling relationship hold in HF?
Yes; Frank-Starling says that with increased stretch/LVEDV/LVEDP, Stroke Volume rises; in HF, the curve shifts downward but increasing venous return can still partially compensate for HF, at the expense of greater pressures
Which branch of the nervous system is active in HF?
The SNS
How does the SNS respond to HF?
Decreased CO is detected by decreased stretch of the carotid and aortic baroreceptors, leading to increased sympathetic outflow to increase HR, Contractility, and TPR to preserve BP compensation
What role does Renin play in HF?
Kidneys secrete Renin in response to decreased plasma volume and salt conc., leading to more fluid retention to raise venous return and CO
What are the deleterious effects of Angiotensin II?
Abnormal vasoconstriction, ventricular remodeling, endothelial dysfunction
What are the effects of ADH/AVP?
ADH causes vasoconstriction through V1 receptors to increase TPR as well as increase water retention through V2 receptors to increase Preload
What role does ANP play in HF?
ANP is released in response to stress on the myocardium, caused by increased fluid volume and filling pressure, and counteracts the effects of SNS, RAAS, and AVP activity
How can ANP be used to diagnose HF?
ANP is released in response to stress on the heart to lower fluid volume, and elevated ANP indicates worse HF outcomes
Do SNS, RAAS, and AVP activation benefit or worsen HF?
Initially, they are beneficial and compensatory but overtime they worsen the HF syndrome
How can increased sodium and water retention worsen HF?
Increased sodium and water retention lead to increased congestion in the heart and lungs
How can increased vasoconstriction worsen HF?
Increased vasoconstriction leads to increased TPR and decreased CO
How can the RAAS system worsen HF?
Ang II and Aldosterone promote fibrosis
What can cause eccentric remodeling in HF?
Volume overload = systolic dysfunction
What can cause concentric remodeling in HF?
Pressure overload = diastolic dysfunction
Why is eccentric remodeling bad in HF?
Leads to mitral regurg and systolic dysfunction
Why is concentric remodeling bad in HF?
Leads to increased stiffness, predisposes ischemia and causes diastolic dysfunction
How does the La Place relationship dictate concentric remodeling in HF?
Since Tension = Pressure / Radius, to keep Tension constant with rising Pressure from volume overload, Radius must also increase leading to increased ventricular thickness
What are the common electromechanical problems in HF?
Scar formation, atrial enlargement, and electric remodeling
How does scar formation lead to HF?
Scar formation promotes focal re-entry = VT
How does atrial enlargement lead to HF?
Atrial enlargement causes fibrosis which promotes AFib
What can cause the heart to begin decompensation?
Decompensation refers to the compensatory mechanism becoming maladaptive, and can be induced by sodium intake, infection, uncontrolled HTN
Outline the progression of systolic HF?
CAD/HTN/Diabetes lead to LV injury; Pathologic remodeling occurs from compensatory SNS stimulation as well as endothelial dysfunction; symptoms such as dyspnea and edema arise from Low EF; proceed to HF and/or death
How does left sided HF present?
Dyspnea, PND, Fatigue, and pulmonary rales
How does right sided HF present?
Peripheral edema, elevated JVD, Hepatomegaly
What is the staging system for HF?
Stages A through D, progresses from high risk to end stage HFrEF
What is Stage A HF?
High risk for developing HF, such as HTN/DM/CAD
What is Stage B HF?
Asymptomatic HF that accompanies LV remodeling, such as MI and LV hypertrophy
What is Stage C HF?
Symptomatic HF such as HFpEF and HFrEF
What is Stage D HF?
End-stage HF = HFrEF
What is the class system for HF?
A way of categorizing HF from Class I to IV on the basis of severity of symptoms, ending with symptoms while at rest
Which ventricle is more compliant?
The RV is highly compliant and needs preload to function
Which ventricle is more sensitive to afterload?
The RV is more sensitive to afterload, and fails easily against increased afterload
What can increase RV afterload?
Pulmonic stenosis, lung disease that vasoconstricts, LV failure that leads to pressure backups
What is high output cardiac failure?
Different than HFpEF and HFrEF, leads to HF due to inability of the heart to sustain a high output in the context of hyperthyroidism and severe anemia
