Hemodynamic change of left ventricle at extreme exercise: Evaluation of upright bicycle stress echocardiography in cross country racers

In order to clarify the left ventricular (LV) bemodynamic change at extreme exercise, 6 male cross country racers underwent stress echocardiography with an upright bicycle ergometer. The heart rate (HR) achieved was 187±8.6 bpm, or 94.1%±4.5% of target rate. During exercise, stroke volume (SV) index (mL/m²) showed significant increase from resting (T₀) to the time when the HR achieved 120 bpm (T₁₂₀), and from T₁₂₀ to the time when the HR reached 150 bpm (T₁₅₀) (T₀:T₁₂₀:T₁₅₀=49±6:69±11:92±6; T₀ vs. T₁₂₀, p<0.01; T₁₂₀ vs. T₁₅₀, p<0.01); however, it fell significantly when subjects achieved extreme exercise (T(max): 78±10) (T₁₅₀ vs. T(max), p<0.05). Cardiac index (L/min/m²) significantly increased when HR approached T₁₅₀ and bit the ceiling limit (T₀: T₁₂₀: T₁₅₀' T(max)= 2.86 ± 0.77:8.3 2 ± 1.30: 13.80±1.85:14.67±2.21; T₀ vs. T₁₂₀, p<0.001; T₁₂₀ vs. T₁₅₀ p<0.001; T₁₅₀ vs. T(max) p=0.48). No significant difference in ejection fraction was observed. Results suggest that cardiac output of cross country racers reaches the ceiling before extreme exercise, and this is caused by the decrease of SV. Shortened filling period caused by tachycardia is thought to induce a decline in LV volume at extreme exercise.