Exercise Echocardiography in the Diagnostic Work-up of Unexplained Dyspnoea: A Critical Narrative Review of Physiological Targets, Diagnostic Performance and Unresolved Controversies

Background: Chronic exertional dyspnoea frequently remains unexplained after clinical assessment, natriuretic peptide measurement and resting echocardiography. Many underlying cardiovascular abnormalities, particularly heart failure with preserved ejection fraction and exercise pulmonary hypertension, become apparent only during physiological stress. Exercise echocardiography is non-invasive, widely available and free of ionising radiation, but its diagnostic role outside ischaemia testing remains contested. Purpose and Scope: This critical narrative review evaluates the evidence supporting exercise echocardiography in adults with chronic exertional dyspnoea that remains unexplained after first-line evaluation. It examines test conduct and feasibility, the diastolic stress test, pulmonary vascular and right ventricular responses, ischaemic, valvular and dynamic obstructive causes, and multiparametric approaches incorporating lung ultrasound, cardiopulmonary exercise testing and artificial intelligence. Methods: Literature was identified through structured searches of bibliographic databases and scholarly indexes, supplemented by citation tracking and professional-society guidance. Evidence was appraised with attention to patient spectrum, reference standards, feasibility reporting and outcome relevance, and synthesised thematically. Principal Findings: Invasive studies consistently show that exercise unmasks haemodynamic abnormalities that resting tests miss. Exercise-derived echocardiographic abnormalities, including elevated filling-pressure surrogates, exercise pulmonary hypertension and exercise-induced pulmonary congestion, carry consistent prognostic information. The diagnostic accuracy of individual markers, especially the ratio of early mitral inflow to early diastolic annular velocity, is considerably less secure: validation studies conflict, largely because of differences in patient spectrum, reference standards and measurement timing. Tricuspid regurgitation signals are frequently unobtainable at peak exercise, and the incremental value of stress testing over probability scores appears modest in several invasive validation cohorts. Left atrial mechanics, systolic reserve, cardiac output-indexed pulmonary pressures and lung ultrasound show promise but require external validation. Unresolved Questions: Consensus is lacking on the reference standard, age- and sex-specific normal responses, optimal protocols and the effect of test-guided management on patient outcomes. Implications and Conclusion: Exercise echocardiography is best regarded as a question-driven, multiparametric physiological test integrated with pre-test probability and, where available, gas-exchange measurement, rather than as a single-parameter rule-in or rule-out tool. Prospective multicentre studies with invasive reference standards and outcome-oriented diagnostic trials are needed before stronger recommendations can be justified.