The Importance of Left Ventricular Outflow Tract and Mid-Ventricular Gradients in Stress Echocardiography: A Narrative Review

Abstract

This review aims to serve as a guide for clinical practice and to appraise the current knowledge on exercise stress echocardiography in the evaluation of intraventricular obstruction in HCM, in patients with cardiac syndrome X, in athletes with symptoms related to exercise, and in patients with normal left ventricular systolic function and exercise-related unexplained tiredness. The appearance of intraventricular obstruction while exercising is considered rare, and it usually occurs in patients with hypertrophy of the left ventricle. The occurrence of intraventricular obstruction when exercising has been evidenced in patients with hypertrophic cardiomyopathy, athletes, patients with cardiac syndrome X, patients with syncope or dizziness related to exercise, and patients with dyspnea and preserved ejection fraction. The clinical significance of this observation and the exercise modality that is most likely to trigger intraventricular obstruction remains unknown. Supine exercise and lying supine after exercise are less technically demanding, but they are also less physiologically demanding than upright exercise. Importantly, in everyday life, human beings generally do not become supine after exercise, as takes place in post-exercise treadmill stress echocardiograms in most echocardiography labs. The presence of induced intraventricular obstruction might be considered when patients have exercise-related symptoms that are not understood, and to assess prognosis in hypertrophic cardiomyopathy.

Clinical Application of Exercise Stress Echocardiography in an Outpatient Pediatric Population

“…The detection of exercise-induced intraventricular gradients (IVGs) related to symptoms such as angina, tiredness, or syncope in patients with normal echocardiogram (no hypertrophy) has previously been published [1,16,[40][41][42][43][44][45][46]. The association of IVGs with symptoms [1,23,24,45,46] in terms of pediatric age has been previously demonstrated, and our results, where a significant orthostatic exercise-induced IVG appeared, seem to confirm this association. The presence of IVG was considered a normal finding by only one group of investigators [40].…”

“…Following the exercise test, as appropriate, patients were promptly positioned in the left lateral decubitus posture, and images were reacquired in identical planes. In circumstances where standing posture was pertinent, such as for detecting and evaluating intraventricular gradients (IVGs) in cases of hypertrophic cardiomyopathy (HCM) or symptomatic children, subjects were instructed to remain standing post-stress test, facilitating echocardiography in this stance [23] (Video S1). Image acquisition during peak and immediately post-exercise was facilitated using a continuous image-capturing system.…”

“…Their average age was 14.1 ± 2.6 years (ranging from 6 to 17 years), and they underwent treadmill ESE using the previously mentioned methodology between 2002 and 2019. The children were categorized-for analytical purposes-into two groups: Group I consisted of 258 children, among whom 237 exhibited symptoms related to exercise (such as chest pain, fatigue, lipothymia/syncope), and 1 experienced aborted sudden death following participation in a triathlon [23]. Additionally, 15 children showed resting ECG alterations, and 6 tested positive according to the electrocardiographic criteria elicited by stress testing using a treadmill.…”

Cardiological Functional Assessment of National Olympic Team of Kazakhstan

“…Echocardiography is a valuable method for the evaluation of an athlete since it provides information on cardiac morphology, function, and hemodynamics at a low cost [21,23]. The echocardiograms of 240 athletes were analyzed.…”

“…Nowadays, the rapidly evolving landscape of diagnostics and screening makes it possible to develop new diagnostic methods or improve known ones and to combine different evaluation methods to obtain more data in a single test with the results already loaded into special software that can analyze many indicators and findings. One of the first methods developed was stress echocardiography, which, unlike classical TTE, is combined with physical, pharmacological, or electrical stress and is dedicated to the detection of many heart conditions, including myocardial ischemia and HCM [22,23].…”