New screening method for common heart disorder

A team of Egyptian cardiologists has discovered a simple new way of diagnosing the world’s most common genetically transmitted heart disorder and identifying affected patients who have an increased risk of adverse cardiovascular events¹.

Hypertrophic cardiomyopathy (HCM) affects approximately 1 in 500 people and is characterised primarily by abnormal thickening of the heart’s muscle tissue, which makes it harder for the heart to pump blood around the body. One common complication of the condition is obstruction of the left ventricular outflow tract (LVOT), in which the volume of blood pumped around the body is dramatically reduced.

LVOT obstruction can occur under stress and during exercise, when contractility of the left ventricle increases. It leads to progression of hypertrophic cardiomyopathy, and predicts adverse outcomes such as cardiac arrest and sudden death in HCM patients. Over 30 percent of patients who have non-obstructive cardiomyopathy do end up with obstruction under stress or exercise.

Clinicians can provoke LVOT obstruction in patients by exercise treadmill testing, in order to screen for and diagnose HCM, and to predict future complications, but this is not possible in those who are not able to do exercise for any reason.   

Hala Mahfouz Badran of Menoufiya University and her colleagues studied 39 HCM patients. They used echocardiography to measure the patients’ heart activity at rest, then compared exercise and an under-the-tongue spray of isosorbide dinitrate (ISDN) — which is used to treat angina — in their ability to induce and evaluate LVOT obstruction.

They found that ISDN inhalation provokes LVOT obstruction as effectively as exercise testing, as indicated by measurements of changes in the pressure produced by blood as it is pumped out of the left ventricle.

ISDN inhalation is therefore equivalent to exercise testing for detecting LVOT obstruction, and can be reliably used in a clinical setting to identify symptomatic HCM patients who cannot perform the exercise test.

1. Badran, H. M., Ibrahim, W.A., Faheem, N., Yassin, R., Alashkar, T., Yacoub, M. Provocation of left ventricular outflow tract obstruction using nitrate inhalation in hypertrophic cardiomyopathy: relation to electromechanical delay. Glob. Cardiol. Sci. Pract. 2015, 15 (2015). | article