Exercise left ventricular outflow track obstruction in hypertrophic cardiomyopathy: Peak exercise or post-exercise pressure gradients?

Introduction Left ventricular outflow track obstruction (LVOTO) is a key feature of hypertrophic cardiomyopathy(HCM). Exerciseechocardiography is necessary to unmask latent obstruction in patients with HCM. However, little is known about the role and impact of obstruction according to the precise time of occurrence during exerciseor immediate recovery. We hypothesized that LVOT pressure gradientscould be enhanced during immediate recovery after exercisecompared to peak exercisein patients with HCM. Method We conducted an observational, single center and retrospective study and included all the patients with HCM referred to our department between 2010 and 2018 for an exerciseechocardiography. All exerciseswere performed on a bicycle in a semi- supine positionand LVOT pressure gradientwere recorded continuously during and immediately after exercisein the same position. Results In total, 121 patients with HCM were included (age 49 ± 16 y, 64% male, 59% NYHA 2 and 3, LV ejection fraction 66 ± 7%, max LV wall thickness 19 ± 5 mm, 69% receiving betablockers). Overall, the maximal LVOT gradients increased from rest, to peak exerciseand recovery (respectively 17 ± 18, 39 ± 43 and 55 ± 60 mmHg, P 0,0001). Sixty-three patients (52%) had a gradient ≥ 30 mmHg at least in one phase, but a maximal gradient ≥ 50 mmHg (threshold for invasive treatment) was observed in 7% of the population at rest, 25% at peak exerciseand 37% at recovery ( P Conclusion The time course of significant LVOTO during exercisein HCM should be evaluated carefully. LVOTO is more severe and more prevalent during immediate recovery. Some patients exhibit only significant post- exerciseLVOT pressure gradients, which therefore cannot explain limitation during exercise.