PAH vs Left Heart PH: Echo Clues and Overlapping Physiology

In "PAH vs Left Heart PH: Echo Clues and Overlapping Physiology," the panel returns to the echocardiogram, this time to separate precapillary from left heart physiology.

Dr. McLaughlin asks Dr. Vaidya how the initial echo steers the evaluation toward Group 1 or Group 2 disease. Dr. Vaidya agrees that hemodynamics alone are not enough, because they capture a slice in time whereas the structure and Doppler profile of the echo reflect longer-term physiology. A precapillary, high-resistance picture shows a notched right ventricular outflow tract profile with a shortened acceleration time, along with a D-shaped septum and an abnormal eccentricity index that reflect high afterload. In the apical four-chamber view the right ventricle may form the apex, its basal diameter may equal or exceed the left ventricle, and the apical angle may open wide. These features do not arise from pure left heart disease, although they can appear in Group 3 or 4.

Features pointing to left heart disease include an enlarged left atrium, left ventricular systolic or diastolic abnormality, and transmitral and tissue Doppler findings that estimate filling pressures. She considers these among the most important parameters, because left heart disease is the most common cause of pulmonary hypertension.

Dr. Channick agrees but cautions that dichotomies, useful for teaching, can imply two buckets. Real patients lie on a spectrum, with some left heart disease alongside severe precapillary disease, and bucketing may leave them undertreated. Dr. Vaidya agrees the assessment must be integrated and longitudinal, since anyone may develop Group 1 disease over a lifetime, and she values provocative maneuvers during catheterization, preferring exercise, often with invasive cardiopulmonary exercise testing. Dr. Kim makes the case for picking a lane, citing negative and even harmful trials of PDE5 inhibitors in Group 2 disease, and he notes that the latest European guidelines suggested monotherapy in the gray zone.

Our next episode, "PAH Practice Pearls: Risk Assessment, Right Heart Focus, and Optimism," closes the series with each panelist's top practice message.