Right ventricular systolic function and ventricular interaction during acute embolisation of the left anterior descending coronary artery in sheep

Objective: Regional LV ischemia involving the septum affects LV systolic fu nction and geometry. We investigated the effects of these changes on RV fun ction and geometry, Methods: Ln six closed-chest sheep end-systolic pressur e-volume relationships (ESPVRs) were constructed from ventricular volumes, measured with magnetic resonance imaging (MRI) and matching intranventricul ar pressures, before and after selective embolisation of the left anterior descending coronary artery (LAD), The extent of myocardial ischemia was ass essed post-mortem by coronary perfusion with Evans-Blue. Alterations in sep tal geometry were studied by measuring the curvature, segmental length and thickness of the septum in two midventricular (short-axis) MRI slices befor e and during ischemia. From these data, changes in LV and RV free wall segm ental lengths were calculated. Results: Selective embolisation of the LAD r esulted in left ventricular ischemia (15+/-2.1% of the total LV) with 23% o f the septum involved. Stroke volume did not change significantly, while LV systolic pressure decreased by 24 mmHg (p<0.05). Although RV systolic func tion decreased to a significantly lesser extent than LV function (p<0.01), systolic function of both ventricles diminished significantly as indicated by substantial rightward shifts of the ESPVRs: 121% for LV and 41% for RV ( both p<0.01). At mid-ventricular level and rnd-systole, the septum showed s ignificant increases in its radius of curvature and segmental length (both p<0.05), and a significant wall thinning (p<0.01). Calculated end-systolic lengths of LV and RV free walls also increased, by 57 and 14% respectively. Conclusions: LAD embolisation not only results in a significantly diminish ed LV systolic function but also causes RV systolic function to decline sig nificantly. Regional dysfunction by necessity entails global dysfunction as well. Analysis of ventricular geometry reveals that both the septum and th e RV free wall increase their length, which plays an important role in the pathophysiology of diminished RV systolic function concomitant with reduced LV function. (C) 1999 Elsevier Science B.V. All nights reserved.