Heart CT scan parameter predicts cardiovascular events in PH
High RV/LV ratio was best independent predictor of MACE
A higher diameter ratio on CT scans between the right ventricle and left ventricle, which are the heart’s lower chambers, independently predicts major adverse cardiovascular events in people with pulmonary hypertension (PH), a study reports.
“In our study, the [right ventricle/left ventricle] ratio not only well reflected PH severity, but also emerged as the strongest predictor of MACE [major adverse cardiovascular events],” the researchers wrote.
In addition, the size of the main pulmonary artery attached to the heart and its ratio with the ascending aorta, the major blood vessel that transports oxygen-rich blood from the heart, were also reliable indicators of PH severity, data shows.
“Identifying a noninvasive and simple CT imaging parameter that reflects PH severity could help identify clinically overlooked PH patients and provide guidance for further evaluation,” the researchers wrote. The study, “CT imaging biomarkers to predict severity and prognosis of pulmonary hypertension,” was published in PLOS One.
PH is a progressive disease associated with high blood pressure in the pulmonary arteries, the blood vessels that carry oxygen-poor blood from the heart to the lungs to be oxygenated. Because the right side of the heart pumps blood through these arteries, the pushback from elevated blood pressure can lead to right heart damage and failure.
The gold standard for PH diagnosis is right heart catheterization, or RHC, wherein a thin, flexible catheter is inserted into a vein in the neck, arm, or groin and passed into the right ventricle and pulmonary artery. This method can directly measure mean pulmonary artery pressure, or mPAP, and reveal the heart’s capacity to pump blood.
Because RHC is invasive and cannot be repeated often, physicians use the noninvasive echocardiogram, which creates images of the heart and blood vessels, to evaluate heart enlargement and heart wall thickening, and to estimate mPAP. Echocardiographic evaluation is challenging for people with obesity or advanced lung disease, however.
A CT scan is another noninvasive imaging technique that has several advantages in diagnosing PH, including being able to rapidly visualize the pulmonary arteries and the right heart structure. Still, data on which CT measurements reflect PH severity or predict major adverse cardiovascular events are limited.
Predicting cardiovascular events
To address this, researchers in South Korea retrospectively analyzed data from 144 people who had heart CT scans and RHC for suspected PH. They then looked for relationships between CT imaging parameters and RHC-assessed mPAP.
The patients’ mean age was 57.7 and more than half (57.4%) were women. Nearly half (41.2%) had high blood pressure, nearly 1 in 4 (23.3%) had altered blood fats, and nearly 1 in 5 (19.6%) had diabetes. Some patients had coronary artery disease (12.2%), where the blood supply to the heart is reduced or interrupted, or pulmonary thromboembolism (14.9%), where a blood clot blocks blood flow in the pulmonary arteries.
Based on mPAP values from RHC, most patients (80.2%) were eventually diagnosed with PH.
CT scans were analyzed to measure the size of the large blood vessels connected to the heart and the size of each ventricle. The septal angle, formed between the wall separating the two ventricles and the chest midline, was also assessed.
According to CT scan data, all the pulmonary artery diameters increased significantly with increasing mPAP values, reflecting more severe PH. These included the main pulmonary arteries, the left and right pulmonary arteries supplying each lung, and the ratio of the pulmonary artery and ascending aorta.
The diameter of the right ventricle and right atrium (the heart’s upper chamber), the right and left ventricles (RV/LV) ratio, the right and left atriums ratio, and the septal angle also significantly increased with increasing mPAP values.
Over a median follow-up of 36 months and up to 115 months, or about 9.5 years, 44 patients (30.6%) had major adverse cardiovascular events, resulting in 30 hospitalizations and 14 deaths.
Statistical analyses adjusted for potential influencing factors showed that a high RV/LV ratio was the best independent predictor of MACE, being significantly associated with a twofold higher risk. Older age was the second best predictor, being linked to a 3% higher risk. Pulmonary thromboembolism was not predictive of MACE, the researchers said.
“Among CT parameters, the RV/LV ratio was the strongest predictor of MACE in patients with PH, while the [pulmonary artery size] and [pulmonary to aorta ratio] were the reliable indicators reflecting mPAP levels,” they wrote.
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