Abstract 12880: A Clinical Index of Myocardial Afterload Can Replace Wall Stress Calculations

Introduction: Afterload at the myocardial level is a principal determinant of LV chamber and myocardial wall function, generated by interplay of LV pressure, volume, and mass. Quantitation has relied on wall stress indices which require additional measurements and calculations as well as incorrect assumptions. Unfamiliar to most clinicians, they have largely fallen out of use, but the role of myocardial afterload in contemporary heart failure pathophysiology and therapy merits reevaluation given the roles of EF and myocardial strains in prognostic indices and treatment guidelines. Hypothesis: A simple clinical afterload index using variables fundamental to wall stress indices (systolic pressure(mmHg) * LV volume(ml))/LV mass(g)) or PV/M correlates closely with stress indices and relates similarly to LV EF and myocardial strains. Methods: In 277 normals (54% female, mean age 50.9±12.9 yrs) and small cohorts with dilated non-ischemic cardiomyopathy(35), aortic stenosis(12) and cancer chemotherapy(43), each with matched controls, we used CMR LV volumes, mass and brachial systolic pressure during imaging to compare end-systolic PV/M to stress indices and systolic pressure alone using correlations and correlation standard errors(SEs). Results: There were extremely close correlations (r= 0.97-0.99, all p< 0.001) with minimal SEs between PV/M and Arts and Alters stress indices with similar slopes in all groups and in normal subgroups by age and gender. Negative correlations with EF, global strains and strain rates were also present and extremely similar in all groups. But Mirsky’s stress index and brachial pressure performed less well. Conclusions: A simple clinical afterload index correlates closely with wall stress indices and similarly with LV ejection fraction and strains. It can support efficient reassessment of the role of afterload at the myocardial level in research and potentially, in clinical practice.