Abstract 3494: The Enduring Importance of Left Ventricular Afterload after Myocardial Infarction
Background: Left ventricular remodeling (LVR) is an important predictor of outcomes after myocardial infarction (MI) and reducing LVR is the basis for ACE inhibitor use at that time. However, studies demonstrating this benefit were conducted prior to the use of early reperfusion and other contemporary therapies. We examined the role of arterial load on LVR after first ST-elevation MI (STEMI) in the present era.
Methods: Data from 122 subjects with STEMI were analyzed. Baseline and 6 month LV volumes and ejection fraction (LVEF) were assessed by resting gated blood pool scans and arterial load, quantified by arterial elastance (Ea; Ea=end-systolic pressure/stroke volume), with 2-D echo. Univariate and multivariate logistic regressions were used to assess LVR predictors described by the odds ratio (OR) and 95% confidence interval comparing the upper quintiles vs. the remaining subjects with respect to 6 month increases in end-diastolic (EDV) and end-systolic (ESV) volumes and decline in LVEF.
Results: At enrollment ≥90% of all subjects had successful reperfusion and during the 6 month study period were taking aspirin, clopidogrel, ACE-inhibitor or angiotensin receptor blocker, β-blocker, and an HMG-CoA reductase inhibitor. At baseline, mean LVEF was 55.6% ± 11.1 and Ea was 1.5 ± 0.4 mmHg/mL. Over 6 months, mean changes in LV volumes and LVEF were: ESV, 7.4 ± 26.6 mL; EDV, 12.4 ± 28.8 mL; LVEF 0.07 ± 7.7 %. After adjusting for baseline demographics including age and clinical variables including MI size by peak creatine kinase using multivariate regression, each standard deviation increase in Ea was associated with LVR [ESV-OR 2.00 (1.14–3.39); EDV- OR 1.52 (0.93–2.49); LVEF- OR 2.39 (1.36–4.22)]. Of the components of Ea, systemic vascular resistance (SVR), pulsatile load, and heart rate only SVR (per standard deviation increase) was a consistent, significant predictor of 6 month LVR [ESV- OR 1.49 (1.03–2.15); EDV- OR 1.39 (0.98–1.97); LVEF- OR 1.74 (1.20–2.52)].
Conclusions: With present STEMI therapies LVR in most patients is modest. The extent of LVR is well predicted by Ea and the most important component is SVR, even in the presence of afterload reducing therapies. Further strategies to improve outcomes post STEMI should target this simple, non-invasive measure.