Homework 2 — Left Heart & Aorta (Cardio_SA_LV)

Interactive version of the Simulink model of Sutton/Lieber (from Hoppensteadt & Peskin). The left ventricle is a time-varying compliance CLV(t); the mitral and aortic valves are ideal diodes with small resistances; the systemic arteries are a Windkessel (Csa, Rs). Aortic insufficiency adds diastolic backflow through the parameter AoBkflo.  ← back to index

Scenario presets (from the assignment)

Normal course parameters from Command_Cardio_SA_LV.m.

Model parameters

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Arterial BP (sys/dia)
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Peak LV pressure (mmHg)
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Stroke volume (mL)
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Cardiac output (L/min)
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EDV / ESV (mL)
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Stroke work (J/beat)

Reading the model like the assignment does

Aortic stenosis (RAo 0.01→1): LV systolic pressure rises far above arterial pressure (a pressure gradient across the valve appears in the pressure plot), stroke volume falls. Compensation = stiffer hypertrophied ventricle (lower CLVS, CLVD, found by the iterative Ks/Pmax rule) plus a raised left atrial pressure to restore filling.
Mitral stenosis (Rmi 0.01→1): the ventricle can’t fill — SV, CO and arterial pressure collapse. Compensation is a markedly raised Pla (increase in 2–2.5 mmHg steps until CO is restored), at the cost of pulmonary congestion.
Aortic insufficiency (AoBkflo 0→0.002): negative aortic flow appears in diastole, diastolic arterial pressure drops (water-hammer pulse, wide pulse pressure), the PV loop widens and stroke work rises for the same forward output.
On the PV loop: bottom edge = diastolic filling (mitral open), right corner = end-diastolic volume, left edge top corner = end-systolic point; the loop area is the stroke work.