Left ventricular contractile reserve in stress echocardiography: the bright side of the force

Stress echocardiography (SE) is based on the detection of regional wall motion abnormalities (RWMA) mirroring a physiologically critical epicardial artery stenosis which determines subendocardial underperfusion. Recently, the core protocol of SE has been enriched by the addition of left ventricular contractile reserve (LVCR) based on force. Changes in force can be caused by microvascular and/or epicardial coronary artery disease, but also by myocardial scar, necrosis, and/or sub-epicardial layer disease. Left ventricular contractile reserve is calculated as the stress-to-rest ratio of force (systolic arterial pressure measured by cuff sphygmomanometer to end-systolic volume determined by two-dimensional echocardiography). In contrast to the ejection fraction, force is not dependent on changes in preload and afterload. Cut-off values for a preserved LVCR are > 2.0 for dobutamine or exercise stress and > 1.1 for vasodilators, which are weaker inotropic stimuli. Patients with a "strong" heart (normal LVCR values) have a better outcome than patients with a "weak" heart (reduced LVCR values), and this is the prognostic "bright side of the force," meaning that the prognostic value of force-based contractile reserve is higher than that of ejection fraction-based contractile reserve or RWMA. The addition of force to standard SE based on RWMA detection increases the spectrum of risk stratification without any significant increase in imaging time and only a slight increase in analysis time. In both ischaemic (with RWMA) and non-ischaemic (without RWMA) hearts, the preserved force is associated with a more benign prognosis. The prospective multicentre international Stress Echo 2020 trial which started in September 2016 has already recruited > 5000 patients with dual RWMA-force imaging and will systematically test the impact of force on the prognosis within and beyond coronary artery disease, including heart failure and hypertrophic cardiomyopathy.