We would like to thank Dr. Thadani and colleagues for their thoughtful comments regarding our report and to apologize to Kircher et al if we misrepresented the results of their study. The correct reference for the use of a fixed value of 14 mm Hg for nonestimable right atrial pressure is from the work of Chan et al, and we have submitted an erratum clarifying this point. Although we agree that 14 mm Hg may not be the optimal value to substitute when right atrial pressure cannot otherwise be estimated, a well-validated alternative has yet to be defined. In recognition of this, we controlled for the possible influence of studies using the fixed 14 mm Hg value by repeating the analyses with these studies removed. Additionally, we directly compared the tricuspid regurgitation gradient to the invasive pulmonary artery systolic pressure (PASP) after the invasive right atrial pressure had been subtracted. Neither of these subanalyses significantly improved the correlations.

The purpose of our study was to evaluate the degree of agreement between invasively and noninvasively determined PASP in actual clinical practice. Invasively determined PASP is indeed subject to several potential sources of error; nonetheless, it remains the recommended “gold standard.” In our study, values were therefore taken “directly” from the catheterization clinical reports as described in the “Methods” section. Additionally, these reports were generated by experienced interventional cardiologists for the purposes of clinical care. With regard to the nonsimultaneous nature of the studies, this was addressed in a number of different ways, all of which provided limited improvement in agreement. Additionally, in a recent study that used near simultaneous measurements, the agreement was similar to that found in our study.

In pointing out the limitations of echocardiographically derived PASP, our study supports the point of Thadani et al that other noninvasive measures of pulmonary pressure should be investigated. The use of echocardiographically derived pulmonary artery mean pressure, diastolic pressure, and vascular resistance is promising, although widespread experience and validation are lacking. As additional data with these parameters are reported, it may be that these measures prove more accurate and reproducible than estimated PASP. Perhaps more important, these alternative estimates may prove better in the identification of patients with pulmonary hypertension and classifying the degree of pulmonary hypertension in these patients.