Cardiopulmonary exercise testing parameters in healthy athletes vs. equally fit individuals with hypertrophic cardiomyopathy

Abstract

Aims: Cardiopulmonary exercise testing (CPET) is often used when athletes present with suspected hypertrophic cardiomyopathy (HCM). While low peak oxygen consumption (pV˙O2) augments concern for HCM, athletes with HCM frequently display supranormal pV˙O2, which limits this parameter's diagnostic utility. We aimed to compare other CPET parameters in healthy athletes and equally fit individuals with HCM.

Methods and results: Using cycle ergometer CPETs from a single centre, we compared ventilatory efficiency and recovery kinetics between individuals with HCM [percent predicted pV˙O2(ppV˙O2) > 80%, non-obstructive, no nodal agents] and healthy athletes, matched (2:1 ratio) for age, sex, height, weight and ppV˙O2. Consistent with matching, HCM (n = 30, 43.6 ± 14.2 years) and athlete (n = 60, 43.8 ± 14.9 years) groups had similar, supranormal pV˙O2 (39.5 ± 9.1 vs. 41.1 ± 9.1 mL/kg/min, 125 ± 26 vs. 124 ± 25% predicted). Recovery kinetics were also similar. However, HCM participants had worse ventilatory efficiency, including higher early V˙E/V˙CO2 slope (25.4 ± 4.7 vs. 23.4 ± 3.1, P = 0.02), higher V˙E/V˙CO2 nadir (27.3 ± 4.0 vs. 25.2 ± 2.6, P = 0.004) and lower end-tidal CO2 at the ventilatory threshold (42.9 ± 6.4 vs. 45.7 ± 4.8 mmHg, P = 0.02). HCM participants were more likely to have abnormally high V˙E/V˙CO2 nadir (>30) than athletes (20 vs. 3%, P = 0.02).

Conclusion: Even in the setting of similar and supranormal pV˙O2, ventilatory efficiency is worse in HCM participants vs. healthy athletes. Our results demonstrate the utility of CPET beyond pV˙O2 assessment in 'grey zone' athlete cases in which the diagnosis of HCM is being debated.

Keywords: Athlete’s heart; Cardiopulmonary exercise testing; Hypertrophic cardiomyopathy.

Figure 1

Ventilatory efficiency in healthy athletes vs. individuals with hypertrophic cardiomyopathy. Parameters of ventilatory efficiency measured as (A) $\stackrel{.}{\mathrm{V}}\mathrm{E}/\stackrel{.}{\mathrm{V}}{\mathrm{C}\mathrm{O}}_2$-early slope (through VT), (B) $\stackrel{.}{\mathrm{V}}\mathrm{E}/\stackrel{.}{\mathrm{V}}{\mathrm{C}\mathrm{O}}_2$-nadir, (C) $\stackrel{.}{\mathrm{V}}\mathrm{E}/\stackrel{.}{\mathrm{V}}{\mathrm{C}\mathrm{O}}_2$-total slope and (D) PETCO₂ at ventilatory threshold in individuals with hypertrophic cardiomyopathy vs. athletes. Horizontal solid lines indicate mean and standard deviation. For (A–C), the interrupted and dotted lines indicate the guideline-recommended $\stackrel{.}{\mathrm{V}}\mathrm{E}/\stackrel{.}{\mathrm{V}}{\mathrm{C}\mathrm{O}}_2$ cut-off of 30 and the prognostically useful threshold of 34, respectively.^,,

Figure 2

End-tidal CO₂ at the ventilatory threshold vs. $\stackrel{.}{\mathrm{V}}\mathrm{E}/\stackrel{.}{\mathrm{V}}{\mathrm{C}\mathrm{O}}_2$ metrics. PETCO₂ correlation between PETCO₂ at ventilatory threshold and (A) $\stackrel{.}{\mathrm{V}}\mathrm{E}/\stackrel{.}{\mathrm{V}}{\mathrm{C}\mathrm{O}}_2$-total slope (B) $\stackrel{.}{\mathrm{V}}\mathrm{E}/\stackrel{.}{\mathrm{V}}{\mathrm{C}\mathrm{O}}_2$-early slope (through VT), (C) $\stackrel{.}{\mathrm{V}}\mathrm{E}/\stackrel{.}{\mathrm{V}}{\mathrm{C}\mathrm{O}}_2$-nadir in individuals with hypertrophic cardiomyopathy vs. athletes. R value for Pearson correlation and corresponding P-value are shown.