Cardiopulmonary exercise testing continues to evolve

Cardiopulmonary exercise testing (CPET) continues to evolve and is becoming an increasingly utilized tool in the assessment and monitoring of patients with congenital heart disease (CHD). Although still somewhat underutilized, awareness and appreciation for this non-invasive study are growing as an adjunct to traditional cardiovascular evaluations. Many may underestimate the usefulness of CPET, mistakenly focusing solely on peak VO2 in patients performing a maximal voluntary exercise test. In reality, peak VO2 is just one well-described and widely understood piece of metabolic data that can be obtained from a well-performed CPET, which also involves selecting and utilizing the appropriate exercise ergometer and protocol. Numerous other metabolic parameters can be obtained, including oxygen pulse kinetics, ventilatory anaerobic threshold parameters, and ventilatory efficiency, as well as patterns on the classical 9-panel plot. These insights into physiological limitations can be valuable in clinical decision-making.

There is also a growing body of literature on submaximal tests, further emphasizing the importance of understanding and interpreting these studies correctly. This scientific statement builds upon previous American Heart Association (AHA) publications on CPET in pediatric and adult populations with CHD. It provides a clear illustration of how much more is now understood about specific heart lesions, transplant indications, mortality outcomes, and more. Although this paper does not offer a comprehensive list of all CPET indications or the heart lesions for which it is beneficial, it does outline some of the most common reasons for referring a patient for exercise testing. One thing this article does particularly well is creating a high-level quick reference for providers who may not be well-versed in interpreting exercise tests, offering guidance for interpreting results in common lesions, including simple repaired and unrepaired acyanotic heart lesions, the most common cyanotic heart lesions, AV valve disease, aortic disease, and single-ventricle physiology. While much more detailed and in-depth studies and textbooks exist on this topic, this article nicely summarizes it for busy clinicians or those looking to better understand how to utilize this evaluation modality in their practice.

More importantly, this scientific statement highlights the utility of CPET as an assessment tool over a patient's lifetime. CPETs can be used in a variety of ways. Similar to other invasive and non-invasive modalities, objective data from an isolated CPET can guide medical management, provide insight into the optimal timing for interventions or surgery, and even suggest a "watch-and-wait" approach, even in the presence of new symptoms. The article underscores that one of the strongest uses of CPET is to track trends over time. While useful data can be gathered from a single test, having baseline data and comparing subsequent tests over time—whether at routine visits or when new symptoms develop—can offer greater insight into a patient's overall progression. This statement also emphasizes how essential it is to recognize the importance of long-term monitoring and its future role in guiding patient care.

In healthy children and adolescents, exercise capacity peaks during adolescence and early adulthood before gradually declining. For patients with CHD, CPET can be valuable even when no new symptoms or intervention triggers are present. As more data are published and more practitioners utilize CPET, it is becoming clear that patients with CHD often experience a faster decline in exercise capacity compared to their healthy peers. This knowledge can prompt important discussions around lifestyle modifications, exercise training, and exercise risk stratification. A better understanding of how repaired and unrepaired congenital lesions—both simple and complex—change over time compared to the healthy population is crucial.

Given the growing understanding of the health benefits and risk-benefit profile of exercise in individuals with congenital heart disease (CHD), many cardiac lesions previously thought to severely limit or preclude physical activity are now being re-evaluated. The use of exercise testing, individualized exercise regimens, and emergency action plans, combined with well-established shared decision-making models, is becoming a more central conversation. This shift is especially important as the pediatric CHD population increasingly survives into adulthood and enters the workforce, potentially taking on physically demanding jobs.

This scientific statement emphasizes the need for ongoing research and reporting on CPET data in patients with CHD. This aligns with the current discussions within the field about the need for specialized training to interpret CPET results, potentially making it a subspecialty within pediatric and adult congenital cardiology. Looking ahead, there is a need for more studies to supplement the existing literature and guide management. There is likely to be increased interest in larger, multi-site studies that link CPET parameters to prognostic outcomes. As with other specialized testing in CHD, standardizing CPET protocols and interpretations is critical to reduce inter-observer variability. As CHD patients transition from one care site to another, consistency in testing capabilities is essential to avoid skewed outcomes or misinformed clinical decisions. This may call to action the need for standardization in exercise testing and interpretation and suggest that a registry of CPET data could help address many of the answerable questions identified in this statement.