Question

Congestive Heart Failure

Activity One:

1)            Define preload, afterload, contractility, Frank Starling mechanism.

2)            Identify three factors that can change preload. Identify three factors that can change afterload.

3)            Describe what happens as filling volume increases, and how that affects pressure.

Activity Two:

1)            Describe reduced vs. preserved ejection fraction heart failure. Which gender is more likely to experience symptoms of CHF with exercise? Which gender is more likely to experience isolated systolic blood pressure increase? Support your answers with citation to either the course material or from online search for evidence-based practice.

2)            Compare left and right sided heart failure. What are the effects of each type of heart failure? Which type is a patient likely to experience first? Why? Which type can result in pitting edema? Which type can result in pulmonary edema?

Activity Three:

Consider this patient below. Identify the patients’ characteristics that put the patient at risk for congestive heart failure.

Sarah Freidan: 48 year old office worker, 5 feet 4 inches tall, weighs 190 lbs. Waist circumference 36 inches. Nonsmoker. No ETOH. Fasting blood glucose 155 mgt/dL. Triglycerides 200mg/dL. HDL-C 46 mg/dL. Blood pressure 148/80. Currently takes no medications.

Activity Four:

Identify pharmacologic agents for diuresis to reduce preload. Identify positive inotropes.   Identify phosphodiesterase inhibitors. Describe the mechanism of action of ACE inhibitors. Describe the mechanism of action of Human B-type natriuretic peptide. Describe the mechanism of action of Angiotensin II-receptor blockers.   Which of these agents is the most commonly used for left sided heart failure? Right sided heart failure?   You may use narrative writing or a table to answer these questions.  

Answer 1

1 ) Preload is the initial stretching of the cardiac myocytes prior to contraction or it is the amount of sarcomere stretch experienced by cardiac muscle cellscalled cardiomyocytes, at the end of ventricular filling during diastole. Preload is directlyrelated to ventricular filling.

Afterlod is the force or load against which the heart has to contract or eject the blood or it is the pressure the heart must work against to eject blood during systole.

Contractility is the intrinsic strength of the cardiac muscle independent of preload, but a change in preload will affect the force of contraction.

Frank-Starling mechanism is the description of cardiac heamodynamics as it relates to myocyte stretch and contractility. That is the stroke volume of the left ventricle will increase as the left ventricular volume increases due to the myocyte stretch using a more forceful systolic contraction.

2 - Factors that influence the preload include

Volume - Changes in the volume inside the left ventricle is the most important factor which determines preload. Increasing the volume with fluids or blood products increases preload, where as, dehydration or blood loss decreases preload.

Heart Rhythm - The slower the heart rate the higher the preload,on the other hand the higher the heart rate the lower the preload

Left ventricular relaxations - Preload is increased if the left ventricle is more in relaxed position

Factos that change afterload

Increased or decreased aortic pressure - When the blood pressure is increased there is a natural increase in the pressure the ventricle must press against and. increased, similarly, when the blood pressure reduced, there is less force to be pressed agaist by the ventricles and a reduction in afterload

Increased or decreased systemic vascular resistance - The SVR will affect the overall pressure and will change the resistance to outflow of the ventricles. Increased SVR will increse the afterload, while decreased SVR will decrease the afterload

Ventricular dilation - This will increase the afterload by increasing the radius of the heart chamber.

3 - If filling volume increases i will increase preload. Too much volume can cause heart failure.