Heart Imaging Useful in PAH Patients With Connective Tissue Disease
The use of imaging to evaluate the right side of the heart could be useful for non-invasively diagnosing and monitoring pulmonary arterial hypertension (PAH) in people with connective tissue diseases, according to a new study.
The study, “Evaluation of pulmonary arterial pressure in patients with connective tissue disease-associated pulmonary arterial hypertension by myocardial perfusion imaging,” was published in the Annals of Noninvasive Electrocardiology.
Connective tissue diseases, or CTDs, are a group of inflammatory conditions that, as the name suggests, affect the body’s connective tissue. Common CTDs include scleroderma, lupus, and rheumatoid arthritis. PAH, when the pressure in the lung’s blood vessels is abnormally high, can be a serious complication of CTDs.
High blood pressure in the lungs, as occurs in PAH, puts strain on the right ventricle — the part of the heart that pumps blood to the lungs to pick up oxygen. Once it picks up oxygen, the blood circles back to the heart’s left ventricle, which pumps it out to the rest of the body.
Myocardial perfusion imaging (MPI) is a technique to take pictures of blood flowing through muscle in the heart. Normally, the right ventricle, which is smaller and thinner than its left counterpart, does not show up on MPI scans. However, when it is strained in PAH, the right ventricle can become enlarged, making it visible on MPI scan.
Here, scientists in China reported on data from MPI scans of 88 people with CTDs; 58 had PAH, and the remaining 30 did not.
The MPI scans were used to calculate a value called right ventricle target/background ratio (T/B), which reflects how distinct the right ventricle appears relative to nearby tissue.
In the patients who had PAH, the right ventricle could be visualized in MPI scans, and the mean T/B was 1.72. By contrast, in patients without PAH, the right ventricle was not visualized by MPI, the researchers reported.
The T/B in PAH patients also showed good correlations with standard measures of PAH severity, such as mean pulmonary arterial pressure (mPAP).
Mean T/B was 1.47 for patients with mild PAH (based on mPAP values), higher at 1.71 for those with moderate PAH, and also significantly higher at 1.96 for severe PAH.
“Our results indicated that T/B exhibited good correlation with mPAP and had a relatively high sensitivity and specificity in diagnosing PAH of different severities,” the researchers concluded.
Sensitivity refers to a test’s ability to detect true-positives of a disease, whereas specificity refers to its ability to detect true-negatives.
The researchers then calculated a statistical measure called area under the curve (AUC) to test the diagnostic utility of the T/B for PAH in CTD. AUC is basically a test of how well a measure (in this case, T/B) can differentiate between two groups — in this instance, PAH or non-PAH. AUC values can range from 0.5 to 1, with higher values indicating a better ability to tell the two groups apart.
The AUC values for mild, moderate, and severe PAH were 0.912, 0.855, and 0.913, respectively — all indicating a relatively good ability to identify PAH among CTD patients.
The researchers noted this study was limited by its small size and that the accuracy of MPI still needs to be improved.