left parasternal impulses

cardiac impulses categorized according to their location along the upper, mid, or lower left sternal border. An upper left parasternal impulse is usually caused by a systolic expansion of a dilated pulmonary artery; a mid to lower left parasternal impulse usually occurs as a result of a right ventricular contraction, and is characterized by an outward movement beginning synchronously with the first heart sound, but is sometimes caused by mitral incompetence.