Overview
Selection order does not determine the result: the engine deduplicates and sorts the active conditions, then uses a fixed clinical priority. Severe pleural/pericardial obstruction, shock and acute valve failure can dominate the phenotype. Morphology flags for the other selected lesions remain available to downstream calculations.
Most shared filling pressures use the dominant burden rather than summing every congested preset. Resistance and flow are reconstructed from the combined state. This avoids counting the same pulmonary congestion or low-output state repeatedly.
Composition rules
When tamponade or acute severe MR/AR already supplies its linked shock phenotype, an added cardiogenic-shock label does not independently duplicate that myocardial penalty. A normal baseline selection drops out when a disease is selected.
The lowest relevant reference flow limits many combinations. Vasodilated/high-output states can add demand, scaled by remaining valve and pump reserve. Depletion plus another disease reduces flow and lowers filling. Combined pulmonary vascular and myocardial disease can reduce flow further. The highest selected reference PVR is retained rather than summing multiple valve-associated PA elevations.
Interacting valves
Independent severity burdens enter pair-specific terms. AS with MR increases modeled systolic LA loading and reduces forward reserve. MS with MR increases the transmitral inflow needed to recirculate regurgitant blood, increasing upstream LA pressure. TS with TR uses the analogous right-sided relation. PS with TR increases right-atrial systolic loading. AS/AR and PS/PR add pressure-plus-volume filling burdens.
The synthetic pair penalty is a bounded flow factor: 1 / (1 + sum of pair losses), with a floor of 0.70. Pair losses use coefficients 0.08–0.12 multiplied by the two lesion burdens; these coefficients are teaching choices, not measured clinical interaction strengths. The later rate, therapy and ventilation calculations can reduce flow further.
Preserve anatomic pressure differences
Mitral stenosis can keep LA pressure above LVEDP; tricuspid stenosis can keep RA pressure above RVEDP. Regurgitant atrial waves are retained when stenosis coexists. A stiff LV can have LVEDP above mean LA pressure. External constraint does not erase a separate mitral gradient. Pulmonic stenosis retains an RV-to-PA systolic gradient.
Limits of combination testing
Some clinical combinations are rare or depend on anatomy that is not modeled. A multi-lesion simulation is a bounded extrapolation, not a validated prediction. Clamps prevent invalid mathematical states; they do not prove that the combination is survivable or that its exact magnitude is realistic. The model does not automatically infer every possible complication or make shock invariably progress to VF.
References & further reading
