Provocation of left ventricular outflow tract obstruction using nitrate inhalation in hypertrophic cardiomyopathy: Relation to electromechanical delay

Abstract

Background: Left ventricular outflow tract obstruction (LVOT) is an independent predictor of adverse outcome in hypertrophic cardiomyopathy (HCM). It is of major importance that the provocation modalities used are validated against each other. Aim: To define the magnitude of LVOT gradients provocation during both isosorbide dinitrate (ISDN) inhalation and treadmill exercise in non-obstructive HCM and analyze the correlation to the electromechanical delay using speckle tracking. Methods: We studied 39 HCM pts (64% males, mean age 38 ± 13 years) regional LV longitudinal strain and electromechanical delay (TTP) was analyzed at rest using speckle tracking. LVOT gradient was measured at rest and after ISDN then patients underwent a treadmill exercise echocardiography (EE) and LVOT gradient was measured at peak exercise. Results: The maximum effect of ISDN on LVOT gradient was obtained at 5 minutes, it increased to a significant level in 12 (31%) patients, and in 14 (36%) patients using EE, with 85.6% sensitivity & 100% specificity. Patients with latent obstruction had larger left atrial volume and lower E/A ratio compared to the non-obstructive group (p < 0.01). LVOTG using ISDN was significantly correlated with that using EE (p < 0.0001), resting LVOTG (p < 0.0001), SAM (p < 0.0001), EF% (p < 0.02) and regional electromechanical delay but not related to global LV longitudinal strain. Using multivariate regression, resting LVOTG (p = 0.006) & TTP mid septum (p = 0.01) were found to be independent predictors of latent LVOT obstruction using ISDN. Conclusion: There is a comparable diagnostic value of nitrate inhalation to exercise testing in provocation of LVOT obstruction in HCM. Latent obstruction is predominantly dependent on regional electromechanical delay.

2019 ESC Guidelines for the diagnosis and management of chronic coronary syndromes

“…Nitrates are not recommended in patients with hypertrophic obstructive cardiomyopathy 266 or co-administration of phosphodiesterase inhibitors.…”

Tissue tracking of segmental strain as a predictor of provoked dynamic left ventricular outflow tract obstruction

“… 30 This basal septum hypercontractility noticed in the current study can't be attributed to aging-related change as there was no age difference between the studied groups. The earlier mechanical activation of the basal septal segment generates a proximal septal bulge which narrows LVOT resulting in the increased flow velocity, 31 the largest radii longitudinal fibers of the basal septum in human heart and the additional load created by pressure from the right ventricle on the basal septum, 32 could be the proposed mechanisms of basal septal hypercontractility which consequent narrows LVOT in patients with inducible obstruction.…”

Four-Dimensional XStrain Echocardiographic Assessment of Left Ventricular Strain and Rotational Mechanics: Technology, Clinical Applications, Advantages and Limitations

“…XStrain STE has been used to evaluate subclinical myocardial damage (Figure 10) in patients with left ventricular hypertrophy and to characterize its various causes [30][31][32][33]. Badran et al [33] have shown that right atrial (RA) mechanics entirely follows right ventricular (RV) and LV function, as well as disease severity.…”