Importance of Right Pulmonary Artery Distensibility Index in the Diagnosis and Management of Pulmonary Arterial Hypertension Secondary to Canine Dilated Cardiomyopathy

The measurement of tricuspid regurgitant velocity is the commonly used non-invasive method for the diagnosis of pulmonary hypertension in dogs. It is anticipated that M-mode echocardiographic measurement of right pulmonary artery distensibility (RPAD) index is simple and provides accurate means for the diagnosis of pulmonary arterial hypertension when tricuspid regurgitant velocity is absent. Hence this study was undertaken to evaluate the importance of RPAD index in the diagnosis and management of pulmonary arterial hypertension secondary to dilated cardiomyopathy.

In the present study, a total of 165 dogs were subjected to echocardiography for diagnosis of pulmonary hypertension secondary to dilated cardiomyopathy. The maximum and minimum internal diameter of the right pulmonary artery during systole and diastole were quantified respectively to determine the right pulmonary artery distensibility (RPAD) index in right parasternal short axis M-mode echocardiogram. The M-mode morphology of right pulmonary artery (anterior dicrotic notch) also recorded.

Out of 165 dogs ten dogs had pulmonary arterial hypertension with dilated cardiomyopathy. Dogs with pulmonary hypertension showed a significant decrease in the mean right pulmonary artery distensibility index values and Acceleration time/Ejection time (AT/ET) ratio, while the mean tricuspid regurgitant systolic pressure gradient (TRPG) were significantly elevated when compared to the respective control group. The significant difference was observed in the mean values of tricuspid regurgitant systolic pressure gradient and RPAD index before and after the treatment.