Progressive and biphasic cardiac responses during extreme mountain ultramarathon

Investigations on the cardiac function consequences of mountain ultramarathon (MUM) >100 h are lacking. The present study assessed the progressive cardiac responses during the world's most challenging MUM (Tor des Géants; Italy; 330 km; 24,000 m of cumulative elevation gain). Resting echocardiographic evaluation of morphology, function, and mechanics of left and right ventricle (LV and RV) including speckle tracking echocardiography was conducted in 15 male participants (46 ± 13 yr) before (pre), during (mid; 148 km), and after (post) the race. Runners completed the race in 126 ± 15 h. From pre to post, the increase in stroke volume (SV) (103 ± 19 vs. 110 ± 23 vs. 116 ± 21 ml; P < 0.001 at pre, mid, and post) was concomitant to the increase in LV early filling (peak E; 72.9 ± 15.7 vs. 74.6 ± 13.1 vs. 82.1 ± 11.5 cm/s; P < 0.05). Left and right atrial end-diastolic areas, RV end-diastolic area, and LV end-diastolic volume were 12-19% higher at post compared with pre (P < 0.05). Resting heart rate and LV systolic strain rates demonstrated a biphasic adaptation with an increase from pre to mid (55 ± 8 vs. 72 ± 11 beats/min, P < 0.001) and a return to baseline values from mid to post (59 ± 8 beats/min). Significant correlations were found between pre-to-post percent changes in peak E and LV end-diastolic volume (r = 0.63, P < 0.05) or RV (r = 0.82, P < 0.001) or atrial end-diastolic areas (r = 0.83, P < 0.001). An extreme MUM induced a biphasic pattern of heart rate in parallel with specific cardiac responses characterized by a progressive increase in diastolic filling, biventricular volumes, and SV. The underlying mechanisms and their clinical implications remain challenging for the future.