We have previously reported that during coronary sinus venography there can be reflux of dye from the coronary sinus ostium towards the distal part of the sinus against the anticipated direction of flow. This phenomenon appeared to be unrelated to the cardiac cycle or respiratory cycle. We postulated that variations in the pressure gradient between the right atrial pressure and coronary sinus pressure (CSp) are responsible for the observed phenomenon. Additionally, we postulated that this phenomenon may predict heart failure progression in patients with left ventricular (LV) dysfunction. A prospective, randomized study was performed with forty-seven patients who were undergoing ICD implant (single, dual chamber or CRT). Prior to lead placement, pulmonary artery pressure (PAp), CSp, and right atrial pressure (RAp) were recorded simultaneously during inspiration and expiration. Patients were categorized in high or low Pap groups (> 45 or ≤ 45 mm Hg). A trend towards increased CSp in patients with high PAp was observed as well as a pressure gradient reversal (RAp > CSp) during inspiration in twenty-four of twenty-nine (83%) patients ranging from 3% to 100% percent time of the cardiac cycle. There are dynamic changes in the RAp and CSp gradients during respiration that can induce reversal of flow gradient even with normal Pap. This may provide a mechanism to explain interventricular interdependence and LV dysfunction in patients with PHT.

New and Noteworthy: This is the first description of measurements of pressure gradients between the right atrium and coronary sinus and flow reversal in the coronary sinus in patients with congestive heart failure.