Cardiopulmonary exercise stress testing (CPET) has numerous applications in cardiovascular medicine.1–5 These include both diagnostic applications, such as in patients with dyspnea of unknown cause or exercise intolerance and prognostic uses, as in heart failure (HF). CPET can also provide insights for risk stratification (such as in hypertrophic cardiomyopathy) and therapeutic optimization (including exercise training prescription in various contexts).1,2,6–9 Moreover, data suggest that incorporating CPET across different frameworks can help streamline patient care by providing useful ancillary data, whether on its own or in association with other diagnostic methods.2,6,9,10 While CPET is a core component of both preventive cardiology and HF programs, especially for those managing advanced HF, this comprehensive assessment is highly relevant multiple points across the cardiovascular continuum, as extensively detailed in various reports.1,3,11–14

The potential usefulness of this exam has been consistently highlighted in several reports, a notion further supported by the growing acknowledgment of functional capacity as a key parameter in patient assessment. CPET, which provides data on peak oxygen consumption (pVO2), is particularly important for this analysis.1,15,16 Despite this, its application has been described as suboptimal.1,3,17 While this may vary according to the setting, challenges to optimal implementation – such as those concerning availability, staffing, or funding – have been noted.1,17–19 Furthermore, a lack of familiarity with this methodology has also been identified as a possible barrier to its application.3,20

Given this background, assessing CPET implementation and its overall patterns of utilization is an important issue, including analyzing possible gaps and unmet needs in this area. These insights may help guide strategies to optimize its application, focusing on improving personalized patient care pathways.

Given its role in contemporary clinical practice, we aimed to assess the current use of CPET in cardiovascular medicine in Portugal, focusing on its overall use, potential barriers and training needs, and challenges to implementation.

A 26-item online open questionnaire (in Portuguese) was specifically designed for this national cross-sectional study to assess physicians’ perspectives on CPET application and training. Prior studies provided background information that was considered during the development of the survey, which was created considering established guidelines for designing questionnaires and the Checklist for Reporting Results of Internet E-Surveys (CHERRIES).18,19,21–25

The questionnaire was divided into three main sections to assess participant characteristics, training and application of CPET, and general knowledge in this field. The first section included ten questions on demographic and workplace-related information, such as the availability of CPET, cardiac rehabilitation (CR) or HF programs. The second section comprised seven questions focusing on the respondent's training in CPET and their usage patterns of this exam. The third section consisted of nine questions based on current literature such as guidelines, position statements, and review articles and focused on the respondent's knowledge of CPET. These questions covered general concepts such as indications for this exam as well as technical issues concerning test performance and data interpretation.1,3,5–7,9,16,17

The questionnaire was developed by an expert panel, which included members of the Portuguese Society of Cardiology's Working Group on Exercise Pathophysiology and CR, which approved the final version. This was then made available online to the society's mailing list; answers were collected from October to December 2024. This was an anonymous and voluntary survey, with no financial compensation being provided for participation. The population under study comprised physicians (based in Portugal) with a medical specialty in cardiology, including both specialists and residents in training who were enrolled in a specialty program, from the second year onward. This cut-off was implemented to allow for contact with different areas where CPET could be of interest. Informed consent was provided at the beginning of the questionnaire.

Results are presented as descriptive statistics and categorical variables are given as total count and percentages (n/%).

A total of 1073 potential participants were present in the mailing list of the Portuguese Society of Cardiology. Over the study period, a total of 70 (6.5%) individuals provided valid answers. Overall participant characteristics are reported in Table 1.

Most were male (52.9%), ≤50 years old (57.1%), specialists (81.4%), and reported performing most of their clinical activity in public centers (74.3%). Most had access to CPET in their workplace (58.6%), with a majority indicating that these exams were performed in cardiology departments (63.4%), whereas 24.4% reported both cardiology and other departments; 12.2% stated this test was performed in other departments. Among those who had access to CPET in their workplace, more than half (51.2%) reported that between 11 and 50 exams were performed per month, 26.8% reported up to ten exams per month, and 14.6% >50 exams each month. Data were unavailable for three (7.3%) individuals. Among those who did not have CPET available in their workplace, 48.3% reported referring patients to other centers. A total of 68.6% of survey participants had access to CR in their workplace, and 65.7% described having a HF program (Table 1). Among the latter, 43.5% reported having an advanced HF program including heart transplantation and ventricular assistance.

Regarding the second part of the questionnaire, an overview is presented in Table 2. Most participants (51.4%) had either dedicated or intended to allocate residency time to CPET training. Among those who did not, the most frequently reported reasons for not dedicating specific residency time to CPET training were lack of access (46.9%) and lack of personal interest (34.4%). Other reasons included lack of time (25.0%) and the fact it was not a specific item included in the assessment during specialty training (12.5%); 3.1% stated this exam was of no interest in cardiac patients. Most participants had participated in CPET exams during their residency (58.6%), 80.5% reported they had participated in these exams during a mandatory rotation, 39.0% during an optional rotation, and 22.0% during a scientific meeting or specific training session. Less than half (41.5%) of those who participated in CPET exams during residency considered they had become autonomous in their performance. As illustrated in Table 2, more than half of those who responded to this survey stated that including a minimum number of CPET exams during residency, including these during a rotation during residency and/or the promotion of courses dedicated to this area by scientific societies could improve the time allocated to CPET training during residency. Another reported way to improve this was by making CPET mandatory in advanced HF programs. In addition, a vast majority (97.1%) of participants thought that specific training in CPET during residency could improve its use.

More than half of participants (65.7%) used CPET in their clinical practice. Of these, 39.1% used it at least once a week, 28.3% at least once a month, 23.9% at least once every six months, 6.5% at least once a year, and 2.2% less than once per year. The most frequent setting in which CPET was used by these individuals was HF (84.8%), followed by the assessment of functional capacity (67.4%), the work-up of unexplained dyspnea or fatigue (60.9%) and exercise prescription (60.9%). Other settings included the assessment of patients prior to heart transplantation and/or left ventricular assist devices (56.5%), cardiomyopathies (54.4%), pulmonary hypertension (39.1%) and pre-operative risk stratification (28.3%). Of those who did not use CPET in their clinical practice, the most frequently selected reason was lack of access (72.7%); other reasons included difficulty in interpreting the results (27.3%) and doubts concerning its benefit (9.1%). When these individuals were asked about the settings in which CPET could be useful, the majority stated they thought prior to heart transplantation and/or left ventricular assist devices (95.5%), HF (90.9%) and the assessment of functional capacity (90.9%), unexplained dyspnea or fatigue (72.7%), cardiomyopathies (63.6%), pulmonary hypertension (59.1%), and exercise prescription (59.1%). Pre-operative risk stratification was selected by 36.4% of these individuals. A total of 71.4% of participants reported being either interested or very interested in CPET.

The overall findings from the third part of the questionnaire are presented in Table 3. Most participants (87.1%) reported being familiar with the indications and contraindications for CPET. More than half of the participants answered correctly to questions about general concepts – some of which also apply to exercise stress testing with electrocardiographic monitoring without respiratory gas analysis – specifically regarding CPET in patients prior to heart transplantation or mechanical circulatory support, as well as in hypertrophic cardiomyopathy. This trend was also observed when assessing knowledge of protocols (Table 3). When analyzing some of the more technical issues related to CPET such as different parameters (namely the respiratory exchange ratio or the VE/VCO2 slope) or the impact of distinct ergometers on pVO2, however, a substantial proportion of participants either did not respond correctly or did not respond (Table 3).

In this survey on the current use of CPET among cardiology physicians in Portugal, more than half of participants had access to this test, and 65.7% reported using it in their clinical practice. The most common indications were HF and the assessment of functional capacity. Notably, although just over half of the respondents reported having taken part in CPET exams during their residency, most did not consider they had become proficient in performing this test. Overall, 97.1% of participants considered that specific training in CPET during residency could improve its use. To the best of our knowledge, this is the first study in Portugal designed specifically to assess these topics.

The comprehensive assessment of cardiovascular disease (CVD) has advanced significantly over time.1,15,26 Although still relevant for certain indications, exercise testing with electrocardiographic monitoring has gradually been replaced by imaging-based modalities – driven by technological advancements and enhanced capabilities – in the assessment of patients with suspected or known ischemic heart disease.1,26,27 Over the years, however, data have emerged showing that incorporating respiratory gas analysis into exercise testing can provide several key parameters across a wide range of clinical contexts.2,4,5,13,15–17 Importantly, these may affect not only CVD but also a variety of other conditions, including respiratory and musculoskeletal diseases, as well as the care of athletes and cancer patients.1,6,10,28 Since some of the landmark studies in this field were conducted over fifty years ago, the importance of certain inputs – especially pVO2 – has been demonstrated in numerous studies involving participants ranging from apparently healthy individuals to those with HF.15,16,29–31 Although several guidelines have emphasized this notion and highlighted the potential use of CPET in various contexts, some reports have also noted limitations in its application.3,6–9,17

In this study, just over half of the respondents had dedicated or intended to dedicate residency time specifically to training in CPET (Table 2). In those who did not, lack of access or lack of personal interest were the most frequently selected reasons, while a quarter reported a lack of time. While 58.6% of overall survey participants participated in CPET during their residency, most considered that they had not become proficient in performing it. These points resonate with some of the challenges mentioned in prior statements, where the large number of potential variables under study (with increased complexity in their interpretation), coupled with the need for specific equipment and staffing, were cited as factors potentially limiting its use.3,17 Although most participants reported using CPET in their clinical practice, 31.4% did not. Among the reasons for this were lack of access (the most frequently cited motive), difficulty interpreting the results, and doubts concerning their benefit. These latter two points further reinforce the possible role of training in this field, both during residency and through continuous advanced training in the future. Indeed, most survey participants considered that specific training in CPET during residency could help improve its utilization. Nonetheless, of those who participated in these exams during residency, fewer than half considered themselves proficient. Furthermore, when analyzing specific concepts related to CPET – such as some of the parameters under study or the impact of ergometers on pVO2 values – a substantial number of participants did not respond correctly or did not respond. As such, similarly to other areas of cardiovascular medicine where training after residency is pivotal to ensuring adequate competency, a structured training program in this field could also help improve its application across different time points.11,32,33 When considered alongside fields such as CR, this concept could further help broaden the scope and overall applications of these interventions.22,34,35

An interesting finding is that, although 58.6% of subjects had access to CPET in their workplace and 48.3% of those who did not refer patients to other centers, the overall number of those using CPET in their practice (65.7%) was below what would be expected if everyone with access to CPET used this exam. As such, although lack of access (as mentioned in the “Results” section) presents a major barrier to its use, other factors should also be taken into consideration. Given the extensive applications of CPET, coupled with increased accessibility, further training and information dissemination may also be key factors in increasing its use. In this setting, considering a framework encompassing core concepts and basic interpretation, aiming to improve general knowledge on the relevance of CPET, basic interpretation, and (with a particular focus) its incorporation into clinical practice, could be particularly useful. For those performing this exam, a structured and dedicated training track focused on complex cases and advanced interpretation could further assist individuals involved in these exams across various settings.11,36–38

Some limitations should be acknowledged when analyzing the present data. Firstly, this survey was among individuals on the Portuguese Society of Cardiology's mailing list, and targeted cardiology physicians to provide an overview of this area in this specific context. Given the multiple applications across various fields and multidisciplinary settings, encompassing physicians from different specialties as well as other members of the care team, further studies should address these issues across these domains.1,18,37,39 Secondly, the response rate to the survey was relatively low (6.5%), especially when compared to other contemporary surveys.40,41 This point should be noted, especially that among those who did not use CPET, around a third cited a lack of personal interest in this area. On the other hand, it should be acknowledged that when assessing the totality of responses to the survey, most participants reported being interested or very interested in CPET. As mentioned in other studies, those more interested in the area might be more inclined to respond, a concept which should be considered, especially given that most participants had access to CR in their workplace, and also had an HF program.22,40 Indeed, while factors such as survey fatigue could have impacted the response rate, others (some of which were mentioned above) should also be considered when analyzing overall results and their application to other settings.42 Thirdly, to our knowledge, data concerning the number of potential members who did not fulfill the predefined criteria for the survey (namely first year residents) were not available. As such, a projected number of potential participants was considered.

Although these limitations should be acknowledged, given the relevance of CPET in contemporary cardiovascular medicine and the limited data on its use in the specific context of this survey, we believe this study provides valuable new insights in this field. These findings, grounded in a pragmatic framework, may help guide the development of strategies to enhance CPET training and use in Portugal.

This national survey provides information on patterns of CPET use and training among cardiology physicians in Portugal, while also highlighting some current hindrances and potential barriers to broadening its applications. HF and the assessment of functional capacity were the most frequent indications for CPET, whereas lack of access was the most common reason for not using this exam in clinical practice. Most respondents considered that specific training in CPET during residency could improve its utilization.

As the comprehensive assessment of CVD becomes increasingly intertwined with personalized care paradigms, these contemporary insights may provide a valuable foundation for developing strategies to enhance CPET utilization. This could help streamline the implementation of this highly versatile test, which can provide critical data for managing CVD.

No funding was obtained for this work.

The authors have no conflicts of interest to declare.