The new clinical standard of integrated quadruple stress echocardiography with ABCD protocol

Abstract

Background: The detection of regional wall motion abnormalities is the cornerstone of stress echocardiography. Today, stress echo shows increasing trends of utilization due to growing concerns for radiation risk, higher cost and stronger environmental impact of competing techniques. However, it has also limitations: underused ability to identify factors of clinical vulnerability outside coronary artery stenosis; operator-dependence; low positivity rate in contemporary populations; intermediate risk associated with a negative test; limited value of wall motion beyond coronary artery disease. Nevertheless, stress echo has potential to adapt to a changing environment and overcome its current limitations.

Integrated-quadruple stress-echo: Four parameters now converge conceptually, logistically, and methodologically in the Integrated Quadruple (IQ)-stress echo. They are: 1- regional wall motion abnormalities; 2-B-lines measured by lung ultrasound; 3-left ventricular contractile reserve assessed as the stress/rest ratio of force (systolic arterial pressure by cuff sphygmomanometer/end-systolic volume from 2D); 4- coronary flow velocity reserve on left anterior descending coronary artery (with color-Doppler guided pulsed wave Doppler). IQ-Stress echo allows a synoptic functional assessment of epicardial coronary artery stenosis (wall motion), lung water (B-lines), myocardial function (left ventricular contractile reserve) and coronary small vessels (coronary flow velocity reserve in mid or distal left anterior descending artery). In "ABCD" protocol, A stands for Asynergy (ischemic vs non-ischemic heart); B for B-lines (wet vs dry lung); C for Contractile reserve (weak vs strong heart); D for Doppler flowmetry (warm vs cold heart, since the hyperemic blood flow increases the local temperature of the myocardium). From the technical (acquisition/analysis) viewpoint and required training, B-lines are the kindergarten, left ventricular contractile reserve the primary (for acquisition) and secondary (for analysis) school, wall motion the university, and coronary flow velocity reserve the PhD program of stress echo.

Conclusion: Stress echo is changing. As an old landline telephone with only one function, yesterday stress echo used one sign (regional wall motion abnormalities) for one patient with coronary artery disease. As a versatile smart-phone with multiple applications, stress echo today uses many signs for different pathophysiological and clinical targets. Large scale effectiveness studies are now in progress in the Stress Echo2020 project with the omnivorous "ABCD" protocol.

Keywords: B-lines; Coronary flow reserve; Echocardiography; Force; Left ventricular contractility; Lung water; Stress echocardiography; Wall motion abnormalities.

Fig. 1

Utilization trends of stress echo. The utilization trends of stress echo compared to myocardial stress scintigraphy in Australia, years 2002–2012 (redrawn from Fonseca et al., ref. [10])

Fig. 2

The targets of integrated quadruple imaging stress echo. The 4 patho-physiological targets of IQ-SE: epicardial coronary artery stenosis (with RWMA); lung water (with B-lines); myocardial function (with LVCR); small vessels (with CFVR)

Fig. 3

The normal quadruple imaging response. The normal IQ-SE response of a non-ischemic (first row), dry (second row), strong (third row) and warm (fourth row) heart

Fig. 4

The abnormal quadruple imaging response. The abnormal IQ-SE response of an ischemic (first row), wet (second row), weak (third row) and cold (fourth row) heart

Fig. 5

The risk stratification with quadruple imaging. The risk stratification with SE, from binary (black or white) response based only to RWMA endorsed by current guidelines (upper row) to the spectrum of responses (from green of lowest to red of highest risk) obtained by quadruple imaging with RWMA supplemented with B-lines, LVCR and CFVR