2.09 - PV Loops & Heart Failure Flashcards
What are the major cardiac parameters that can be inferred from a PV Loop?
Stroke Volume
Ejection Fraction
EDV
Preload
Draw a Normal PV Loop highlighting all the observable parameters
Define Heart Failure
Heart failure is the pathophysiological state in which an abnormality of cardiac function is responsible for the failure of the heart to pump blood at a rate commensurate with the requirements of the metabolisiing tissues and/or allows it to do so only from an abnormally elevated diastolic volume
What is the general cause for heart failure?
Manifests itself only after compensatory mechanisms have been exhausted and typically after a precipitating cause.
Insufficient cardiac output –> output failure and/or volume retention
What are the five ways heart failure can be defined?
Cardiac cycle, Cardiac output, development, anatomy and perfusion
Describe the ‘cardiac cycle’ category for heart failure
Can be systolic (an inability to contract) or diastolic (inability to relax/fill)
Describe the ‘cardiac output’ category for heart failure
Can be either High-output (high demand - pregnancy, anaemia) or low output (low CO - ischaemic heart disease)
Describe the ‘development’ category for heart failure
Can be either acute (infarct, infection, rupture of papillary muscle etc.) or chronic (slow progress with lots of adaptation)
Describe the ‘Anatomy’ category for heart failure
Can be either left-sided (pulmonary symptoms) or right-sided (peripheral symptoms)
Describe the ‘perfusion’ category for heart failure
Can be either forward (insufficient perfusion) or backward (increased venous pressure)
Describe the pathophysiology of acute heart failure
Occurs in condtions such at AMI
Backward failure leads to an increase in RA pressure, this activates the CP reflex –> HR
Forward failure results in decreased blood pressure in the aorta –> activation of the arterial baroreceptor reflex–> increased sympathetic activity.
Therefore the CO is regained due to the increased sympathetic activity but at a cost of increase right atrial pressure and heart rate (an increase in internal work and decreased energy efficincy)
Describe the pathophysiology of forward heart failure
Due to an insufficient CO –> decreased perfusion. This leads to fluid retention (due to decreased renal perfusion)
The decrease in perfusion leads to sympathetic activation (AB reflex) –> increased HR
Describe the changes in the PV Loop in heart failure
Reduced contractility
Increased preload
Decreased systolic pressure
Decreased SV
Decreased EF
Decrease in external work and increase in internal work
Describe the events in decompensation in heart failure
A critical CO level of ~5L/min is required to maintain sufficient renal perfusion. If this is not met, sodium is actively retained via activation of the RAAS –> increased volume) at a price of increase RA pressure
Eventually of a few days, failure will result
Describe the therapeutic approach to treating Heart Failure.
Increase SV (increase contractility, decrease diastolic pressure, reduce central venous pressure, reduce venous return.
Decrease afterload (reduce peripheral resistance, reduce end-systolic volume (increase EF))
Ensure appropriate electrical pacing (reduce HR where appropriate, convert to sinus or “sinus like rhythm” to ensure a constant output)
Energy sparing treatments (paradoxical) - ACE inhibitors, aldosterone antagonists, beta blockers
