Sustainability and Versatility of the ABCDE Protocol for Stress Echocardiography

Abstract

For the past 40 years, the methodology for stress echocardiography (SE) has remained basically unchanged. It is based on two-dimensional, black and white imaging, and is used to detect regional wall motion abnormalities (RWMA) in patients with known or suspected coronary artery disease (CAD). In the last five years much has changed and RWMA is not enough on its own to stratify patient risk and dictate therapy. Patients arriving at SE labs often have comorbidities and are undergoing full anti-ischemic therapy. The SE positivity rate based on RWMA fell from 70% in the eighties to 10% in the last decade. The understanding of CAD pathophysiology has shifted from a regional hydraulic disease to a systemic biologic disease. The conventional view of CAD encouraged the use of coronary anatomic imaging for diagnosis and the oculo-stenotic reflex for the deployment of therapy. This has led to a clinical oversimplification that ignores the lessons of pathophysiology and epidemiology, and in fact, CAD is not synonymous with ischemic heart disease. Patients with CAD may also have other vulnerabilities such as coronary plaque (step A of ABCDE-SE), alveolar-capillary membrane and pulmonary congestion (step B), preload and contractile reserve (step C), coronary microcirculation (step D) and cardiac autonomic balance (step E). The SE methodology based on two-dimensional echocardiography is now integrated with lung ultrasound (step B for B-lines), volumetric echocardiography (step C), color- and pulsed-wave Doppler (step D) and non-imaging electrocardiogram-based heart rate assessment (step E). In addition, qualitative assessment based on the naked eye has now become more quantitative, has been improved by contrast and based on cardiac strain and artificial intelligence. ABCDE-SE is now ready for large scale multicenter testing in the SE2030 study.

Keywords: coronary artery disease; functional test; heart failure; stress echo; sustainability.

Figure 1

The conceptual approach of advanced stress echocardiography (SE): from vulnerable stenosis to vulnerable patient. Left panel: in the classical or conventional approach that has been used for 40 years and in first-generation multicenter studies such as Echo-Persantine Cooperative (EPIC) and Echo-Dobutamine Cooperative (EDIC) studies, SE was only focused on the hemodynamic significance of the coronary stenosis. Right panel: the advanced ABCDE protocol used in the last 5 years in second-generation SE2020 and SE2030 multicenter studies. The focus is shifted to the patient as a whole and involves the assessment of vulnerability to ischemia (step A with RWMA is now corroborated by regional and global longitudinal strain and artificial intelligence), pulmonary congestion (step B), the left ventricular contractile and preload reserve (step C), coronary microcirculation (step D) and chronotropic reserve (step E). CAD—coronary artery disease; 2D—2-dimensional echocardiography; RWMA—regional wall motion abnormalities; LUS—lung ultrasound; ESV—end-systolic volume; EDV—end-diastolic volume; CFVR—coronary flow velocity reserve; HRR—heart rate reserve.

Figure 2

The prognostic approach with advanced SE. Left panel: in the classical or conventional SE approach risk stratification is based only on the presence and extent or regional wall motion abnormalities, which offers a limited measure of risk. Right panel: the advanced ABCDE protocol acts as a Newton’s prism that offers a multi-dimensional response that includes regional wall motion, pulmonary congestion, preload and afterload reserve, coronary microcirculation, and sympathetic reserve. Each color identifies a specific vulnerability and is a possible target for selective therapeutic interventions.