Provocation of left ventricular outflow tract obstruction using nitrate inhalation in hypertrophic cardiomyopathy: Relation to electromechanical delay
Tamer Abdelnaby Azab Zaki Elashkar, Hala Mahfouz Badran, Waleed Abdou Ibrahim, Naglaa Faheem, Rehab Yassin and Magdi Yacoub
Menoufiya University, Egypt
The BAHCM National Program, Egypt
Aswan Heart Center, Egypt
Imperial College, London, UK
: Int J Cardiovas Res
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 ¼ 0.006) & TTP mid septum (p ¼ 0.01) were found to be independent predictors of latent LVOT obstruction using ISDN.
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