The boot like shape is due to the right ventricular hypertrophy present in TOF. Lung fields are often dark (absence of interstitial lung markings) due to decreased pulmonary blood flow. Electrocardiography shows right ventricular hypertrophy (RVH), along with right axis deviation. RVH is noted on EKG as tall R-waves in lead V1 and deep S-waves in lead V5-V6. Tet spells may be treated with beta-blockers such as propranolol, but acute episodes require rapid intervention with morphine or intranasal fentanyl to reduce ventilatory drive, a vasopressor such as phenylephrine, or norepinephrine to increase systemic vascular resistance, and IV fluids for volume expansion. Oxygen (100%) may be effective in treating spells because it is a potent pulmonary vasodilator and systemic vasoconstrictor. This allows more blood flow to the lungs by decreasing shunting of deoxygenated blood from the right to left ventricle through the VSD. There are also simple procedures such as squatting and the knee chest position which increase systemic vascular resistance and decrease right-to-left shunting of deoxygenated blood into the systemic circulation. If the spells are refractory to the above treatments, people are usually intubated and sedated. The treatment of last resort for tet spells is extracorporeal membrane oxygenation (ECMO) along with consideration of Blalock Taussig shunt (BT shunt). Total surgical repair of TOF is a curative surgery. Different techniques can be used in performing TOF repair. However, a transatrial, transpulmonary artery approach is used for most cases. The repair consists of two main steps: closure of the VSD with a patch and reconstruction of the right ventricular outflow tract. This open-heart surgery is designed to relieve the right ventricular outflow tract stenosis by careful resection of muscle and to repair the VSD. Additional reparative or reconstructive surgery may be done on patients as required by their particular cardiac anatomy. Timing of surgery in asymptomatic patients is usually between the ages of 2 months to one year. However, in symptomatic patients showing worsening blood oxygen levels, severe tet-spells (cyanotic spells), or dependence on prostaglandins from early neonatal period (to keep the ductus arteriosus open) need to be planned fairly urgently  Potential surgical repair complications include residual ventricular septal defect, residual outflow tract obstruction, complete atrioventricular block, arrhythmias, aneurysm of right ventricular outflow patch, and pulmonary valve insufficiency.