After load is the amount of resistance the heart must pump against to eject blood from the heart into the body.
Cardiac output = SV X R stroke volume times rate is the amount of blood circulated through the body in a minute.
Stroke volume is the amount of blood pump from each ventricle during contraction
Starling’s Law of the Heart reflects the elasticity creating force of cardiac cells to contract. As heart goes into failure the cells are stretch and dilated and so loose the ability to contract with efficient force. Think of a rubber band, the more it is stretch and dilated the weaker it is and loses its recoil ability. This is the same physiology seen in heart failure.
How do the baroreceptors in the carotid arch influence hormone secretion in heart failure?
Baroreceptors sense the pressure with which the blood as ejected and fills the aorta. This is reflected in the blood pressure. If the pressure is low, word is sent out to secrete hormones of the body to contract the arteries, and retain fluid to fill the arteries thus raising the blood pressure.
Explain the role of these hormones in heart failure:
Adrenalin – causes vasoconstriction of blood vessels leading to hypertension
Aldosterone – binds with sodium to retain water and cause the symptom of edema
Antidiuretic Hormone closes the epithelial cells in the distal kidney tubule and thereby retains water that adds to the symptoms of hypertension and edema.
Renin is secreted by the juxtaglomulerus of the kidney in response to the request of the baroreceptors in the aortic arch. Renin then goes to the lungs to initiate the formation of Angiotensin I and II that will add to hypertension.
Angiotensin II goes to the cardiac cells to stimulate remodeling or the formation of immature cardiac cells that are not able to contract with the force necessary to eject the volume of blood necessary for adequate stroke volume, thus the cardiac output remains low and the heart continues into failure.
What is the physiology that causes the primary symptoms of dyspnea, edema, and fatigue in heart failure?
Dyspnea comes from lungs trying to compensate for decrease perfusion in alveoli.
Fatigue results from lack of oxygen and build up of carbon dioxide in cells as sluggish circulation cause tissues to not have normal cleaning and perfusion.
Edema is a safety mechanism to third space fluid and decrease the work load of the heart pumping blood.
Why does PND paroxysmal nocturnal dyspnea occur primarily at night?
Edema fluid held in the legs during the day while a person is sitting, returns to the general circulation when the person is horizontal in bed. This fluid causes overload and drowning sensation leading to symptoms of severe dyspnea, air hunger and pulmonary edema.
Contrast the etiology of left and right sided heart failure.
Left sided heart failure occurs after MI, hypertension, or other causes that weaken the pumping ability of the left ventricle. Occurs in response to resistance of blood pumping in afterload. Low blood flow over the carotid baroreceptors triggers the compensatory hormone mechanisms or Adrenalin, Aldosterone, ADH and Renin. Treatment is medication to reduce afterload or intraortic balloon pump is person goes into shock.
Right sided heart failure deals with preload. The edema fluid is trying to return to the already full distended right ventricle.
Think about it … blood can’t be pumped out to the body or lungs so ventricles are full of blood. Where is new blood trying to ender the heart going to go? It backs up so jugular veins distend and A/V waves can be seen when the heart contracts. The body employs safety measure of third spacing reducing the flow of blood back to the heart by pushing it into the tissues by increased hydrostatic pressure. This is similar to when a river is full of water; the water overflows the banks and seeps into the ground. Same thing in heart failure, the ground is the tissues of the body (pulmonary edema of lungs, ascites from the liver, and pitting edema in the legs.
Differentiate Cor Pulmonale from right sided heart failure.
Right sided heart failure occurs with MI, Cor Pulmonale occurs from COPD as heart has to pump against the resistance of lung tissue pathology.
Comparison of heart, kidney, and liver failure symptoms
| Symptom | heart | kidney | liver |
| Ascitesedema | ADH, renin, Aldosterone secretion, venous congestion into right ventricleIncreased hydrostatic pressure | ADH, renin, Aldosterone secretion, venous congestionLack of output | Decreased albuminPortal hypertension, increased capillary pressure, obstruction of venous flow |
| hypertension | ADH, renin, Aldosterone secretion, arterial congestion, edema, arterial constriction | ADH, renin, Aldosterone secretion, fluid retention | Liver does not metabolize aldosterone |
| breath | acetone | Fetor hepaticus | |
| Change sensorium | Decreased circulation and oxygen | Increased nitrogen and acidosis | Ammonia and nitrogen |
| hepatomegaly | Venous engorgement | Scar tissue, inflammation | |
| puritis | Uric acid crystals, uremic frost | Bile salts and jaundice | |
| anemia | Low hemoglobin and oxygen carrying power | Lack of erythropoietin | Inability to metabolize hemoglobin and clotting factors |
| Diagnostic labs | H &H, BNP, Aldosterone | BUN, creatinine, electrolytes Creatinine clearance | AST, ALT, PT, BUN, A/G ratio |
| acidosis | Decrease CO, inadequate tissue perfusion, decrease oxygen exchange in cells, lactic acidosis | Hydrogen retention | |
| anorexia | Venous stasis in the abdominal organs, ascites | Toxins, ammonia | Ascites, toxins |
| diet | DASH, low sodium, cholesterol, low triglycerides, and fluid restriction | Low sodium, potassium, protein, fluid restriction, high carbohydrate | High carbohydrate, low protein, low sodium |
| hepatomegaly | venous engorgement | Inflammation, scar tissue | |
| Treatments | diuretics | dialysis | Diuretics, SPA |
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