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

Abstract

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. Cutoff 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.

Contractile reserve by left ventricular ejection fraction alone, or considering elastance. ¿Which is the best predictor of events after a Stress Echo without ischemia?

“…It has the advantages of having greater sensitivity than other parameters, and being able to globally assess systolic function both at rest and with effort. (4)(5)(6) As observed by the group of Picano et al, their behavior with exercise can show 3 responses: normal ascending (exertion values that double the baseline, related to high systolic blood pressure values with decreased end-systolic volume), abnormal biphasic (initial slight increase followed by a return to baseline), and abnormal flat (both pressure and volume remain unchanged during stress) (7) Considering the findings of these previous investigations, we can infer that the evaluation of CR by elastance during stress with exercise could have a higher prognostic value than the isolated measure-ment of the CR reserve by LVEF in patients with negative Stress Echo for ischemia (8,9), and even in early stages of cardiomyopathies.…”

Exercise stress echocardiography: Where are we now?

“…The variables are summarized in the ABCD protocol[ 88 ]. The four parameters converge conceptually, logistically, and methodologically: (1) Regional wall motion abnormalities[ 89 ]; (2) Comets or B-lines measured by lung ultrasound[ 90 ]; (3) Left ventricular contractile reserve assessed as the stress/rest ratio of elastance, also called force (systolic arterial pressure by cuff sphygmomanometer/ end-systolic volume from 2D)[ 91 ]; and (4) Coronary flow velocity reserve in the left anterior descending coronary artery (with color-Doppler-guided pulsed wave Doppler)[ 92 ]. This new way to conduct stress echo allows a functional assessment of epicardial coronary artery stenosis (wall motion), lung water (lung comets), myocardial function (left ventricular contractile reserve) and coronary small vessels (coronary flow velocity reserve in the mid or distal left anterior descending artery).…”

Echocardiography in patients with heart failure: recent advances and future perspectives

“…A promising option is the calculation of force-based contractile reserve (the stress-to-rest ratio of force expressed as systolic arterial pressure measured by cuff sphygmomanometer to end-systolic volume determined by two-dimensional echocardiography) that is load-independent. It appears to be more effective in identifying abnormal contractile potential and may improve diagnostic and risk stratification protocols in HF [40].…”