Left ventricular diastolic function assessed with cardiovascular magnetic resonance imaging and exercise capacity in patients with non-obstructive hypertrophic cardiomyopathy.

Background: In patients with non-obstructive hypertrophic cardiomyopathy (HCM) and preserved left ventricular (LV) systolic function, diastolic dysfunction is one of the major factors contributing to limited exercise capacity. Cardiovascular magnetic resonance (CMR) imaging has become a useful tool in diagnosis, risk stratification and treatment monitoring in patients with HCM.

Aim: To assess the relationship between simple CMR parameters of LV diastolic function at rest and exercise capacity measured by means of cardiopulmonary exercise testing on a treadmill in patients with non-obstructive HCM and preserved LV systolic function.

Methods: The study included 13 patients with non-obstructive HCM and preserved LV systolic function who underwent cardiopulmonary exercise testing on a treadmill and CMR within 1 month. Analysed parameters of diastolic function included: LV mass index (LVMI), peak filling rate normalised to LV stroke volume index (PFR/LVSVI) and time from the end-systole to PFR normalised to heart rhythm (TPFR).

Results: There was a significant correlation between PFR/LVSVI at rest and peak oxygen uptake (V02peak) (r=0.64, p=0.02). Patients with V02peak below median (<30 ml/kg/min) had a significantly lower PFR/LVSVI than patients with higher V02peak [5.12 m2/s, interquartile range (IQR) 4.16-6.82 vs. 7.93 m2/s, IQR 7.49-8.21 respectively, p=0.035]. LVMI, TPFR were not related to exercise capacity. There was also no correlation between V02peak and age (r=-0.38, p=0.19), LV ejection fraction (r=-0.36, p=0.22) or normalised LV volume indices: LVEDVI (r=0.09, p=0.76), LVESVI (r=0.34, p=0.26).

Conclusions: Assessment of LV diastolic function by peak filling rate normalised to stroke volume index by means of CMR at rest in patients with non-obstructive HCM and preserved LV systolic function is a useful marker of exercise capacity.