<P> The abdominojugular test, when done in a standardized fashion, correlates best with the pulmonary arterial wedge pressure, and therefore, is probably a reflection of an increased central blood volume . In the absence of isolated right ventricular failure, seen in some patients with right ventricular infarction, a positive abdominojugular test suggests a pulmonary artery wedge pressure of 15 mm Hg or greater . </P> <P> Certain wave form abnormalities, include Cannon a-waves, or increased amplitude' a' waves, are associated with AV dissociation (third degree heart block), when the atrium is contracting against a closed tricuspid valve, or even in ventricular tachycardia . Another abnormality, "c-v waves", can be a sign of tricuspid regurgitation . The absence of' a' waves may be seen in atrial fibrillation . </P> <P> An elevated JVP is the classic sign of venous hypertension (e.g. right - sided heart failure). JVP elevation can be visualized as jugular venous distention, whereby the JVP is visualized at a level of the neck that is higher than normal . The paradoxical increase of the JVP with inspiration (instead of the expected decrease) is referred to as the Kussmaul sign, and indicates impaired filling of the right ventricle . The differential diagnosis of Kussmaul's sign includes constrictive pericarditis, restrictive cardiomyopathy, pericardial effusion, and severe right - sided heart failure . </P> <P> An exaggerated "x" wave or diastolic collapse of the neck veins from constrictive pericarditis is referred to as Friedreich's sign . </P>

What is an a wave in the heart