Comparison of Ultrasound with Fluoroscopy to Assess Diaphragmatic Paralysis After Congenital Heart Disease Surgery

Diaphragmatic paralysis is a common cause of delayed recovery and morbidity after cardiovascular surgery which accounts for 64% of all causes of phrenic nerve lesions. Similarly, congenital heart disease surgery is commonly associated with phrenic nerve injury resulting in diaphragmatic dysfunction in pediatric patients with an incidence of 0.3-5.4%. The phrenic nerve can be injured through various mechanisms such as hypothermia due to ice cold slush for myocardial protection, dissection near the pedicle area of the internal thoracic artery, dissection or conduction of heat along the path or area of the phrenic nerve, etc. Diaphragmatic paralysis is usually transient and not clinically significant in adult, but it is a serious and life-threatening complication that causes respiratory distress in pediatric patient.

Various diagnostic techniques can be used to assess diaphragmatic paralysis such as chest X-ray, fluoroscopy, computed tomography (CT), dynamic magnetic resonance imaging (MRI), and electromyography. The fluoroscopy test has been the method of choice to diagnose diaphragmatic paralysis as it is relatively easy to perform. Earlier studies diagnosed unilateral diaphragmatic paralysis by evaluating the dynamic motion of the diaphragm using fluoroscopy. However, there are several disadvantages of fluoroscopy tests such as requiring cooperation from the patient, requiring the patient in an upright position, the difficulty in transporting patients from the ICU to the fluoroscopy room or cath lab, especially in unstable patients who may deteriorate, the cumulative burden of exposure to radiation, and the relatively high costs.

Diaphragmatic ultrasound (two-dimensional combined with M-mode) is a fast, simple, cheap, accurate, non-radiation noninvasive study that is widely available and increasingly used both in clinical setting and researches. Bedside ultrasound can be used for immobilized or intensive care patients. The simpler procedure helps assessing diaphragmatic paralysis in pediatric patients. The combination of B-mode and M-mode in ultrasound can quantitatively assess the distance and amplitude of diaphragm motion on both sides so that it may provide objective quantification. Therefore, this study was conducted to compare diaphragmatic ultrasound with fluoroscopy as the diagnostic method of diaphragmatic paralysis after congenital heart disease surgery.