Ventilatory efficiency in healthy athletes vs. individuals with hypertrophic cardiomyopathy. Parameters of ventilatory efficiency measured as (A) $V˙E/V˙CO2$-early slope (through $VT$⁠), (B) $V˙E/V˙CO2$-nadir, (C) $V˙E/V˙CO2$-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 $V˙E/V˙CO2$ cut-off of 30 and the prognostically useful threshold of 34, respectively.^10,13,23