Routine, Non-Invasive Tests May Predict PH Severity, Mortality

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by Steve Bryson, PhD |

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Routine blood screenings and non-invasive clinical tests may predict disease severity and mortality in people with pulmonary hypertension (PH), a study suggested.

Specifically, the red blood cell distribution width (RDW) test, used in hematology laboratories to classify anemia, may help in assessing disease severity, while electrocardiographic ratios may predict mortality, according to the researchers.

“In our study, an increased RDW value was significantly (and independently) predictive of severity,” the team wrote, also noting that some routine heart measures were linked with worse prognosis.

The study, “Evaluating of Red Blood Cell Distribution Width, Comorbidities and Electrocardiographic Ratios as Predictors of Prognosis in Patients with Pulmonary Hypertension,” was published in the journal Diagnostics.

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The standard method of diagnosing PH is an invasive procedure called right heart catheterization, for which patients usually are given mild sedatives. Physicians pass a special catheter into the right side of the heart and arteries that supply blood to the lungs to measure blood pressure. Elevated pressure inside these pulmonary arteries is a hallmark of the lung condition.

Non-invasive tests such as an electrocardiogram (ECG), which measures the heart’s electrical activity to find abnormal heartbeats, and an echocardiogram, to examine the chambers of the heart, also can be used to diagnose PH. But because disease symptoms can develop over a long period of time and mimic those of other heart and lung conditions, it remains very difficult to detect and diagnose PH in routine physical exams.

Thus, further development of additional non-invasive diagnostic tools is still needed.

Red blood cell distribution width or RDW is a parameter that reflects variations in the size of red blood cells. It is commonly used to diagnose anemia ━ a condition characterized by a lack of healthy red blood cells to carry enough oxygen throughout the body. However, the ability of RDW to diagnose and predict disease outcomes (prognosis) in PH is unclear.

The goal of this study, conducted by investigators based at the National Institute of Respiratory Diseases Ismael Cosio Villegas, in Mexico, was to evaluate RDW and other routine non-invasive tests as prognostic markers in people with PH.

A total of 198 PH patients were enrolled, ranging in age from 18 to 91, and with a mean age at diagnosis of 57.01 years. More than half 54% of the participants were women.

Clinical and demographic data were collected from medical records, and participants were categorized according to disease severity as determined by pulmonary blood pressure, with higher pressure indicating more severe PH. Overall, 112 patients (56.6%) had mild PH and 51 (25.8%) had moderate disease, with severe PH was found in 35 (17.7%).

The researchers estimated the proportion of patients who developed severe PH since their diagnosis, as well as the number who survived after PH diagnosis.

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The overall analysis showed the development of severe PH was associated with abnormalities to the right side of the heart, scarring of the lungs (known as pulmonary fibrosis), and connective tissue diseases related to the protein collagen. Such diseases were identified as collagenopathies.

Mortality due to PH was linked to those older than 65, individuals smoking more than two packs of cigarettes per year, patients who needed intensive care, and those having irregular heartbeats.

Three measures that detect abnormal heartbeats by electrocardiogram or ECG are the P-wave, QRS-wave, and T-wave. The P-wave reflects the electrical activity resulting from the contraction of the atria, the heart’s top chambers, when blood is pushed into the ventricle. The QRS-wave, the large spike on the ECG, coincides with ventricle contraction and the main heartbeat, followed by the T-wave, in which the ventricle is reset.

Developing severe PH was associated with a lower P to T ratio, while a higher QRS to T ratio was linked to a higher risk of mortality. The P to QRS ratio was not related to mortality nor severity, the researchers said.

A statistical analysis, which included multiple clinical factors, found that an increased risk of PH severity was associated with higher RDW percentage and the presence of collagenopathies, whereas a lower risk of severe PH was found in women and those with a higher P to T ratio.

Increased risk of mortality was associated with older age and a higher QRS to T ratio. In contrast, mortality risk was slightly decreased in those with higher hematocrit levels, a measure of the volume of red blood cells to the total volume of blood ratio, and increased FEV1, or the amount of air forced from the lungs during a forced breath in one second.

“Our results support the importance of red blood cell distribution width, electrocardiographic ratios and collagenopathies for assessing pulmonary hypertension prognosis,” the researchers concluded.

“This study constitutes one of the largest cohorts of patients with pulmonary hypertension in Mexico, and mainly demonstrated that the presence of an increased red blood cell distribution width and electrocardiographic ratios were strongly associated with severity and mortality, respectively,” they wrote.