Extreme left to right shunting causes anatomic changes within the pulmonary arteries, which consequently lead to pulmonary hypertension. This is known as Eisenmenger syndrome. The ECG of a patients with this condition show extreme right axis deviation and tall R waves in V₁ and V₂. At times, alterations of the ST/T waves are present in the precordial leads (see ECG below).

Pulmonary Artery Hypertension Secondary to Eisenmenger Syndrome ECG ⁶⁵

The ECG above comes from a patient with Eisenmenger syndrome. Right atrial dilatation and RVHare seen on the patient’s 2-D echocardiograpm. Consequently, the ECG demonstrates extreme axis deviation of −150° and a right atrial and right ventricular strain pattern.