Beyond distance and heart rate: Reading 6-minute walk test via blood pressure variability in chronic heart failure

Abstract

The six-minute walk test (6MWT) remains a tool for assessing exercise capacity in heart failure, with six-minute walk distance as the endpoint. To enhance interpretability, vital signs such as heart rate and blood pressure may also be recorded in accordance with technical statements. However, beta-blockers often blunt heart-rate-based readouts during the 6MWT, thereby reducing the interpretability of six-minute walk distance. Akimova et al recently published a study in World Journal of Experimental Medicine, which identified blood pressure variability (BPV) as a minutes-scale recovery signal during a paired 6MWT. The index targets the 20-minute post-exercise recovery window and uses point-to-point systolic blood pressure change to help characterize cardiac reserve and to enhance interpretation of the 6MWT. The measure is low cost and easy to implement, and BPV remains associated with imaging indices such as left ventricular ejection fraction in beta-blocked heart failure populations. Importantly, this should be viewed as an early, proof-of-concept insight. Future work should confirm these findings in multicenter prospective studies, define operational protocols and thresholds for BPV, and explore relationships with clinical outcomes, thereby further enhancing the value of minutes-scale BPV.

Key Words: Six-minute walk test; Heart failure; Blood pressure variability; Beta-blockers; Cardiac function

Core Tip: The six-minute walk test (6MWT) is a tool for the assessment of exercise capacity in chronic heart failure. During beta-blocker therapy, heart-rate readouts during 6MWT are often blunted. Blood pressure variability measured in the recovery window following 6MWT may overcome this limitation, offering a low-cost method to assess compensatory reserve and enhance cardiac interpretation.

This editorial refers to “Short-term blood pressure variability as an indicator of the adaptive capacity of patients with chronic heart failure” by Akimova et al, 2025; https://doi.org/10.5493/wjem.v15.i4.110904.

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INTRODUCTION

The six-minute walk test (6MWT), a standardized tool for assessing cardiopulmonary function and exercise capacity, is widely used for clinical evaluation and rehabilitation follow-up in chronic heart failure (HF) since the 1990s[1,2]. Guidelines have established the prognostic value of six-minute walk distance (6MWD), with shorter distances predicting higher risks of mortality, non-fatal cardiovascular events, and HF rehospitalization[3-5]. Therefore, the 6MWT has been used to assess functional status in populations with different types of HF[6-8]. Its core outcome, and the only universally required quantitative endpoint, is the 6MWD. In routine reporting, it is best practice to document interruptions and rest periods, record vital signs at the start and end of the test, and note patient-reported symptoms[5]. These details strengthen clinical interpretation of functional status and enhances evaluation of test safety.

6MWT UNDER BETA BLOCKADE: USING BLOOD PRESSURE VARIABILITY TO AID CARDIAC INTERPRETATION

In a recent issue of the World Journal of Experimental Medicine, Akimova et al[9] evaluated a paired 6MWT protocol combined with short-term blood pressure variability (BPV). The study enrolled 74 compensated chronic HF patients (New York Heart Association II-III) due to coronary artery disease and/or hypertension, who were stratified by beta-blocker use. The following multipoint Doppler echocardiographic parameters were assessed: Left ventricular ejection fraction (LVEF) and tricuspid annular plane systolic excursion, adaptation parameters such as time to heart rate recovery (THRR) and adaptation index (a composite adaptability index as operationalized in the study), and BP differences/variability for systolic blood pressure (SBP) and diastolic blood pressure across the 6MWT protocol. THRR is treated as a noninvasive index of autonomic function. A reduced heart-rate recovery indicates impaired parasympathetic reactivation after physical activity and has been linked to increased cardiovascular risk[10,11]. Notably, beta-blocker use can blunt heart-rate dynamics and thereby weaken the independent interpretive value of HR-based measures such as heart rate recovery in clinical practice[12]. This pattern was also observed in the present study. Among patients not receiving beta-blockers, THRR and adaptation index correlated the expected directions with LVEF and with HF class. In the beta-blocker subgroup, these correlations weakened or disappeared, which suggesting that heart rate-based readouts have limited interpretability in medicated, real-world settings. Further analyses found that the SBP difference in the period between the end of the first 6MWT and 20 minutes of rest before the start of the second, referred to as BPV during 6MWT (ΔSBP at the 20-minute recovery window), showed the most stable and reproducible associations with tricuspid annular plane systolic excursion and LVEF across strata. Accordingly, the authors proposed that under beta blockade, short-term BPV, especially the change in SBP, can complement 6MWD as a medication resistant and more robust readout for characterizing compensatory and recovery capacity.

Most contemporary work on BPV examines its association with cardiovascular and cerebrovascular risk over long-term scales. Analyses from the TOPCAT and the HEAAL show that, in both HF with preserved ejection fraction (HFpEF) and with reduced ejection fraction, higher visit-to-visit BPV is independently associated with worse outcomes[13,14]. This pattern has been replicated across cohorts and supports the notion that long-term fluctuation relates to long-term risk[15,16]. By contrast, Akimova et al[9] investigate a minutes-scale phenomenon during a functional test. Their focus is the recovery window around the 6MWT, rather than monthly or yearly clinic BPV or 24-hour ambulatory BPV. Framed accordingly, the BPV during 6MWT should be viewed as a bedside, minutes-scale indicator of recovery and compensatory reserve, and as an early, proof-of-concept insight rather than a definitive prognostic standard. Beyond qualitative associations, defining thresholds for clinical applications is required. Existing evidence on short-term blood pressure responses suggests that both an insufficient rise in systolic pressure, which often indicates poor capacity, and an excessive rise (e.g., > 20 mmHg) are associated with higher risk[17]. This implies that the choice of cut point for BPV during the 6MWT, which is not yet defined, may influence interpretation and clinical risk stratification and therefore warrants further attention.

Assessment of exercise and functional capacity is critical throughout the management of HF. It supports stratification for rehospitalization risk and prognosis, providing a reliable follow up signal to reflect changes in health status[3,18,19]. Compared with cardiopulmonary exercise testing, which requires specialized equipment and staff, the 6MWT provides robust and, in selected heart-failure populations, near-comparable prognostic information for major outcomes, while offering greater accessibility and scalability, particularly in resource-limited settings and routine outpatient follow-up[20-22]. Given its high test-retest reliability and procedural reproducibility, the 6MWT should continue to prioritize 6MWD as the main endpoint. At the same time, adding BPV in the recovery window can create a two-dimensional frame that links functional performance with physiological coupling and helps interpret compensatory or recovery capacity. For clinicians, blood pressure can be measured immediately after the 6MWT and again after a short recovery period, especially in patients receiving beta-blockers. A lack of SBP recovery or marked instability during this window may indicate reduced adaptive reserve and should prompt closer follow-up or further evaluation. It should be noted that Akimova et al’s findings[9] come from a single center, and their optimal BPV during the 6MWT lies in the 20-minute interval from the end of the first test to the start of the second. Future studies should focus on three aspects. First, multicenter prospective studies are needed to confirm the relationship between minutes-scale BPV and imaging indices and to test associations with outcomes such as mortality and cardiovascular events. Second, analyses should evaluate whether these relationships differ among heart-failure phenotypes, New York Heart Association functional classes, and levels of neurohormonal blockade. Third, research should determine the shortest and optimal interval between the two blood-pressure measurements and assess whether similar information can be obtained with a simplified schedule, while validating these findings across multiple centers and diverse populations.

CONCLUSION

Incorporating minutes-scale blood pressure variability has the potential to enhance interpretation of cardiac function in the 6MWT, but further validation is needed.