Right ventricular free wall circumferential strain reflects graded elevation in acute right ventricular afterload

This study was designed to evaluate the concurrent changes in the right ventricular free wall (RVFW) movement in experimentally induced, acute mild, moderate, and severe right ventricle (RV) afterload conditions. In 14 open-chest pigs (weight 43 +/- 4 kg) with preserved pericardia, acute mild (>35 and <50 mmHg), moderate (> or =50 and < or =60 mmHg), and severe (>60 mmHg) increases in RV systolic pressure (RVSP) were induced by constriction of the pulmonary artery. At each step, longitudinal, radial, and circumferential strains and strain rates were measured in both the RVFW and the interventricular septum. The mean RVSPs were 31.0 +/- 4.3 mmHg at baseline and 41.1 +/- 2.7 mmHg during mild, 52.7 +/- 3.4 mmHg during moderate, and 61.7 +/- 1.6 mmHg during severe afterload conditions. The RVFW circumferential strains showed significant differences among baseline, mild, moderate, and severe afterload conditions (-10.5 +/- 3.9, -8.3 +/- 3.3, -5.4 +/- 2.7, and -7.5 +/- 5.3%, respectively, P = 0.008) and had significant linear correlation with RVSP (r = 0.636, P < 0.001) if the severe condition was excluded. Decrease of the RVFW circumferential strain magnitude is the most distinct response in acute mild and moderate RV afterload that could aid in detection of clinical conditions associated with acutely increasing RV afterload.