P886Exercise left ventricular outflow track obstruction in hypertrophic cardiomyopathy: peak exercise or post-exercise pressure gradients?

Abstract Background Left ventricular outflow track obstruction (LVOTO) is a key feature of hypertrophic cardiomyopathy (HCM), associated with poor prognosis and requiring specific management in symptomatic patients. Furthermore, new drugs targeting LVOTO are under investigation. Exercise echocardiography is the more relevant test to unmask latent obstruction in patients with HCM and to link obstruction to symptoms during physical activity. However, little is known about the role and impact of obstruction according to the precise time of occurrence during exercise or immediate recovery. Objective We hypothesized that LVOT pressure gradients could be enhanced during immediate recovery after exercise compared to peak exercise in patients with HCM. Methods 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 exercise echocardiography. All exercises were performed on a bicycle in a semi-supine position and LVOT pressure gradient were recorded continuously during and immediately after exercise in the same position. Results 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). Exercise was performed until exhaustion at a mean workload of 118±58 Watts. Overall, the maximal LVOT gradients increased from rest, to peak exercise and recovery (respectively 17±18, 39±43 and 55±60 mmHg, p<0,0001). More than half of the patients (52%) had a gradient ≥30 mmHg at least in one phase, but a maximal gradient ≥50 mmHg (threshold for invasive treatment in symptomatic patients) was observed in only 7% of the population at rest, 25% at peak exercise and 37% at recovery (p<0.001). Finally, a maximal gradient ≥50 mmHg was recorded only during immediate recovery (69±25 mmHg) and not during exercise in 16 patients (13%). None of them experienced post-exercise syncope. Conclusion The time course of significant LVOTO during exercise in HCM should be evaluated carefully. LVOTO is more severe and more prevalent during immediate recovery. Some patients exhibit only significant post-exercise LVOT pressure gradients, which therefore cannot explain limitation during exercise.