Abstract
The right ventricle and left ventricle are physically coupled through the interventricular septum. Therefore, changes in the geometry and mechanics of one ventricle can directly affect the function of the other. In treatment of pediatric pulmonary arterial hypertension, the left ventricle is often overlooked, with clinical focus primarily on improving right ventricular function. Pediatric pulmonary arterial hypertension represents a disease distinct from adult pulmonary arterial hypertension based on etiology and survival rates. We aimed to assess left ventricular torsion rate in pediatric pulmonary arterial hypertension and its role in right ventricular dysfunction. Cardiac magnetic resonance images with tissue tagging were prospectively acquired for 18 pediatric pulmonary arterial hypertension (WHO class I) patients and 17 control subjects with no known cardiopulmonary disease. The pulmonary arterial hypertension cohort underwent cardiac magnetic resonance within 48 hours of clinically indicated right heart catheterization. Using right heart catheterization data, we computed single beat estimation of right ventricular end-systolic elastance (as a measure of right ventricular contractility) and ventricular vascular coupling ratio (end-systolic elastance/arterial afterload). Left ventricular torsion rate was quantified from harmonic phase analysis of tagged cardiac magnetic resonance images. Ventricular and pulmonary pressures and pulmonary vascular resistance were derived from right heart catheterization data. Right ventricular ejection fraction and interventricular septum curvature were derived from cardiac magnetic resonance. Left ventricular torsion rate was significantly reduced in pulmonary arterial hypertension patients compared to control subjects (1.40 ± 0.61° vs. 3.02 ± 1.47°, P < 0.001). A decrease in left ventricular torsion rate was significantly correlated with a decrease in right ventricular contractility (end-systolic elastance) (r = 0.61, P = 0.007), and an increase in right ventricular systolic pressure in pulmonary arterial hypertension kids (r = –0.54, P = 0.021). In both pulmonary arterial hypertension and control subjects, left ventricular torsion rate correlated with right ventricular ejection fraction (controls r = 0.45, P = 0.034) (pulmonary arterial hypertension r = 0.57, P = 0.032). In the pulmonary arterial hypertension group, interventricular septum curvature demonstrated a strong direct relationship with right ventricular systolic pressure (r = 0.7, P = 0.001) and inversely with left ventricular torsion rate (r = –0.57, P = 0.013). Left ventricular torsion rate showed a direct relationship with ventricular vascular coupling ratio (r = 0.54, P = 0.021), and an inverse relationship with mean pulmonary arterial pressure (r = –0.60, P = 0.008), and pulmonary vascular resistance (r = –0.47, P = 0.049). We conclude that in pediatric pulmonary arterial hypertension, reduced right ventricular contractility is associated with decreased left ventricular torsion rate.
Highlights
Pulmonary arterial hypertension (PAH) in children is an incurable and progressive disease, characterized by increasing mean pulmonary arterial pressure and vascular resistance, resulting in right ventricular (RV) hypertrophy, and eventual ventricular failure.[1,2,3] In contrast to adult PAH, pediatric PAH etiology is predominantly idiopathic and associated with congenital heart disease[4] and has been shown to have a worse survival,[5] with adult studies greatly outnumbering pediatric research
Thirteen of the PAH patients were diagnosed as idiopathic PAH, one patient was diagnosed as PAH due to a connective tissue disease, three had PAH due to congenital heart disease, and two with hereditary PAH
No significant differences were found in left ventricular ejection fraction (LVEF) between
Summary
Pulmonary arterial hypertension (PAH) in children is an incurable and progressive disease, characterized by increasing mean pulmonary arterial pressure (mPAP) and vascular resistance, resulting in right ventricular (RV) hypertrophy, and eventual ventricular failure.[1,2,3] In contrast to adult PAH, pediatric PAH etiology is predominantly idiopathic and associated with congenital heart disease[4] and has been shown to have a worse survival,[5] with adult studies greatly outnumbering pediatric research. A study of the progression of PAH in children, separate from adult pathophysiology, is needed. LV torsion and rotation may reflect the ability of the left ventricle to contract and transfer mechanical energy to the right ventricle, and has been shown to be indicative of LV ejection, filling, and potential energy storage.[13,14] we hypothesize that the LV torsion rate is decreased in our sample of children with PAH, and that this reduction is associated with a decrease in RV function (e.g. contractility and ejection fraction), RV–pulmonary arterial decoupling (measured as the ventricular–vascular coupling ratio), and hemodynamic measures of pulmonary arterial and ventricular afterload
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