PISA Calculator
Calculate pisacalculator quickly with our cardiovascular system tool. Get results based on evidence-based formulas with clear explanations.
Reviewed by Rahul Singh, Health & Wellness Specialist
Formula
Meridional Stress = (0.334 x P x r) / (h x (1 + h/r))
Where P = systolic blood pressure (mmHg), r = LV internal radius (cm), h = wall thickness (cm). End-systolic stress uses end-systolic pressure and dimensions. Ventriculo-arterial coupling = Ees/Ea, where Ees = end-systolic elastance (ESP/ESV) and Ea = arterial elastance (ESP/SV).
Worked Examples
Example 1: Normal Cardiac Wall Stress Assessment
Problem:A healthy patient has SBP 120 mmHg, LVEDD 50 mm, wall thickness 10 mm, and EF 60%. Calculate wall stress parameters.
Solution:Meridional Wall Stress = (0.334 x 120 x 5.0) / (1.0 x (1 + 1.0/5.0))\n= 200.4 / 1.2 = 167.0 kdynes/cm2\n\nCircumferential Stress = (120 x 5.0) / (2 x 1.0) = 300.0 kdynes/cm2\n\nEnd-Systolic Pressure = 0.9 x 120 = 108 mmHg\nESD estimate = 5.0 x (1 - 0.36) = 3.2 cm\nEnd-Systolic Wall Stress = (0.334 x 108 x 3.2) / (1.15 x (1 + 1.15/3.2)) = 80.1 kdynes/cm2
Result:Meridional Stress: 167 | End-Systolic Stress: 80 | VA Coupling: Normal
Example 2: Dilated Cardiomyopathy Wall Stress
Problem:A heart failure patient has SBP 100 mmHg, LVEDD 70 mm, wall thickness 8 mm, and EF 25%. Calculate wall stress and coupling.
Solution:Meridional Wall Stress = (0.334 x 100 x 7.0) / (0.8 x (1 + 0.8/7.0))\n= 233.8 / 0.891 = 262.4 kdynes/cm2\n\nEnd-Systolic Pressure = 90 mmHg\nESD estimate = 7.0 x (1 - 0.15) = 5.95 cm\nESWT = 0.92 cm\nEnd-Systolic Wall Stress = markedly elevated\n\nStroke volume is reduced, arterial elastance elevated relative to LV elastance.
Result:Wall Stress: Severely Elevated | VA Coupling: Impaired | Afterload mismatch present
References
Reviewed by Rahul Singh, Health & Wellness Specialist · Editorial policy