Seven-second X-ray scan detects severe pulmonary valve regurgitation with high accuracy

Researchers at Kyushu University have developed a simple, rapid, and low-radiation X-ray technique that can evaluate the severity of a heart condition known as pulmonary valve regurgitation-a common and clinically significant complication after surgical repair of a congenital heart defect known as Tetralogy of Fallot. The test only requires a scan of seven seconds and can evaluate the patient with 93% accuracy.

The new technique, published in the journal Radiology, can help diagnose patients who cannot undergo traditional diagnostic methods, improve access to accurate diagnosis, greatly improve efficiency, and bridge the gap between echocardiography and cardiac MRI.

Tetralogy of Fallot, or TOF, is the most common cyanotic congenital heart defect that affects approximately 1 in 3,500 newborns. It is characterized by defects in the heart's structure that reduce blood flow to the lungs, resulting in low oxygen levels.

Thankfully, with advances in surgical techniques and patient care, today over 90% of patients survive into adulthood. However, Pulmonary Regurgitation (PR) is a common long-term complication after surgical repair that can lead to increased risk of sudden cardiac arrest if left untreated. Monitoring PR severity is essential to determine when patients should be treated."

Yuzo Yamasaki, Assistant Professor, Kyushu University Hospital Radiology Center and first author of the study

Cardiac MRIs are the standard practice for quantifying the severity of PR. However, the procedure can be limiting to patients since MRIs can be expensive and require expertise and equipment typically available at specialized facilities. Additionally, MRIs cannot be performed in patients with incompatible pacemakers or defibrillators, or in those with claustrophobia.

To overcome these obstacles, the research team focused on utilizing an emerging imaging technique called dynamic chest radiography, or DCR. This method uses conventional X-ray equipment to capture sequential chest images while the patient holds their breath.

"DCR images are usually assessed visually. However, for this study, we analyzed temporal changes in pixel values over the pulmonary arteries in captured sequential images. These changes were converted into waveforms, allowing us to quantify blood flow dynamics," continues Yamasaki. "In patients with PR, blood flows back into the right ventricle during each heartbeat. The more severe the regurgitation, the more blood flows and that shows up as a more prominent waveform. We tested this new technique in 58 post-surgical patients and 14 healthy volunteers. We were able to detect severe PR with an accuracy of 93%."

Moreover, because DCR uses X-ray, it requires no contrast media and uses minimal radiation, approximately 0.2 mSv. A standard chest CT is around 6 mSv.

The team hopes that the implementation of their new technique will help both patients with PR access to quality care and hospitals reduce costs.

"DCR can also be used to study and diagnose other heart diseases like heart failure and pulmonary hypertension," concludes Yamasaki. "We are currently planning a multicenter study to further validate these findings and hopefully establish DCR in routine clinical practices."