Pulmonary hypertension (PHT) is defined as an elevated pulmonary circulatory pressure, which results in right ventricular (RV) pressure overload causing compensatory RV myocardial hypertrophy followed by progressive systolic dysfunction and dilatation.
RV and left ventricular (LV) function and volumes were found to be powerful predictors of prognosis and treatment response, thus early detection of myocardial deformation abnormality and systolic impairment is of utmost importance.
Cardiac magnetic resonance feature tracking (CMR FT) is a novel efficient noninvasive tool for myocardial strain quantification that may allow detection of early myocardial abnormalities using routinely acquired cine images.
To determine the value of RV and LV longitudinal strain analysis by FT as a diagnostic tool in PHT patients.
Materials and methods
CMR exams were performed on a 1.5T machine to assess RV and LV volumes and function in 22 patients with PHT, 9 males and 13 females, with a mean age of 38 years (range = 19 – 67). Three of the patients had chronic thromboembolic pulmonary hypertension (CTEPH), 1 had an ASD with peripheral pulmonary vascular aneurysms and the rest of the patients had primary PHT. Mean calculated RV ejection fraction (EF) was 40 ±11%. Mean LV EF was 59 ±9%.
CMR exams of a control group of 20 healthy volunteers, 3 males and 17 females, with a mean age of 24 years (range = 20 – 50) were used. Mean RV EF was 61 ±6%. Mean LV EF was 62 ±6%.
Long axis standard steady-state in free-precession (SSFP) cine images were used for longitudinal strain quantification in both groups using CMR FT. Results of longitudinal strain values of both groups were compared and correlated with RV and LV CMR derived EFs.
RV global longitudinal strain was statistically significantly impaired in PHT patients compared to controls (with a mean -11.09 ±3.8 vs. -21.97 ±3.18), P< 0.0001.
In PHT patients, RV longitudinal strain values were directly proportional to RV EF. The lower the RV systolic function, the lower the RV longitudinal strain, P<0.0017.
Similarly, LV global longitudinal strain was statistically significantly impaired in PHT patients compared to controls (with a mean -11.66 ±2.22 vs. -18.04 ±1.84), P<0.0001, in spite of having a mean LV EF of 59 ± 9%, falling within the normal range.
LV longitudinal strain was found to assume a positive linear relationship with RV strain of those patients, P<0.0001, while it failed to assume a significant correlation with LV EF, P=0.6117. Analogously, LV EF had a weak correlation with RV strain, P=0.7952.
FT longitudinal strain analysis is a powerful tool than can add diagnostic value in patients with PHT. Not only that it was able to detect RV wall deformation abnormalities efficiently and objectively, but It was also able to identify early abnormalities in LV myocardial deformation before there was overt systolic LV dysfunction evidenced by decreased EF.