Key result
Original Karvonen formula accurately estimates first ventilatory threshold on beta-blockers, outperforming modified formula.
Why the study?
CPET is the gold standard for determining VT1 but is not routinely available in cardiac rehabilitation, and the accuracy of indirect VT1 estimation methods in beta-blocker treated cardiac patients is unclear.
Do indirect estimation methods accurately predict the first ventilatory threshold compared to cardiopulmonary exercise testing in beta-blocked cardiac patients?
Cross-Sectional (n=26)
Double-blind (for threshold determination)
Do indirect estimation methods accurately predict the first ventilatory threshold compared to cardiopulmonary exercise testing in beta-blocked cardiac patients?
In beta-blocked cardiac patients, the original Karvonen formula and dyspnea threshold provide safer and more accurate estimations of the first ventilatory threshold than the modified Karvonen formula, which overestimates target intensity.
Answers are grounded in this paper and cite their sources.
Original Karvonen formula may better estimate VT1 than modified version in beta-blocked patients; leaves open prospective validation before guiding prescriptions.
AimsCardiopulmonary exercise testing (CPET) is the gold standard for determining the first ventilatory threshold (VT1), a key marker for prescribing exercise-training intensity, but is not routinely available in cardiac rehabilitation.We evaluated the accuracy of commonly used indirect methods for estimating VT1 in beta-blocker (BB) treated cardiac patients. Methods and resultsTwenty-six BB treated patients with cardiovascular disease underwent maximal CPET.VT1 estimations derived from the original and modified Karvonen formulas, rating of perceived exertion (Borg scale, target 12-14), and the dyspnea threshold were compared with CPET derived VT1 and VT2.Agreement was assessed using Lin's concordance correlation coefficients and Bland-Altman analysis.The original Karvonen formula (ρ c = 0.90; 95%CI 0.81-0.95;bias+5 bpm) showed the best agreement with VT1.The dyspnea threshold showed moderate agreement (ρ c = 0.86; 95%CI 0.71-0.93;bias +7 bpm), whereas perceived exertion showed poor agreement with VT1 (ρ c = 0.73; 95%CI 0.53-0.85;bias +12 bpm).The modified Karvonen formula had the poorest estimation of VT1 (ρ c = 0.68; 95%CI 0.50-0.85;bias+16 bpm) but closely matched VT2 (ρ c = 0.94; 95%CI 0.87-0.97;bias+0.3bpm). ConclusionIn the absence of CPET, the original Karvonen formula and the dyspnea threshold could be preferred for guiding exercise intensity in BB treated patients, whereas the modified Karvonen formula consistently overestimates VT1 by approximating VT2, making it unsuitable for secure exercise-intensity prescription.
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Martin et al. (2026) conducted a cross-sectional in Cardiovascular disease on beta-blocker therapy (n=26). Indirect estimation methods (Original Karvonen formula) vs. Cardiopulmonary exercise testing (CPET) was evaluated on Agreement of the original Karvonen formula with the CPET-derived first ventilatory threshold (VT1) (Concordance correlation coefficient (ρc) 0.90, 95% CI 0.81-0.95). The original Karvonen formula showed substantial agreement with the CPET-derived first ventilatory threshold (ρc 0.90) in beta-blocker treated patients, whereas the modified Karvonen formula systematically overestimated it.
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