Author + information
- Francois Haddad, MD∗ (, )
- Anton Vonk-Noordegraaf, MD, PhD and
- Roham T. Zamanian, MD
- ↵∗Division of Cardiovascular Medicine, Stanford University, 300 Pasteur Drive, Palo Alto, California 94305
We agree with Drs. Palazzuoli and Ruocco that several other parameters determine prognosis in patients with pulmonary arterial hypertension (PAH). As summarized in Figure 1, these factors include, although are not limited to, parameters of right ventricular (RV) function, pulmonary resistance, functional class as well as the etiology of PAH. Stability of function over time is also emerging as an important prognostic factor in PAH (1). In addition, risk prediction models must be tailored to their context, i.e., prevalent (as in our study) versus incident cases and chronic versus acute decompensated right heart failure. In our study, we were not suggesting that “the right heart score” should replace well-validated risk prediction formulas or scores but that quantitative measures of right heart structure or function could simplify risk prediction. Moreover, because of our small sample size, it is difficult to account for the complexity of risk stratification without overfitting the data. In the future, these risk scores could help tailor therapy or improve stratified randomization for clinical trials.
We agree with the authors that right heart adaptation is a key determinant of survival in PAH (2). A ventricle that is able to hypertrophy or better increase its contractility in response to the increased afterload is more likely to have improved survival. In this regard, the concept of mass-to-volume ratio is interesting; for example, patients with a higher RV mass-to-volume ratio for a given pulmonary vascular resistance (PVR) are likely to have a better prognosis. Interpretation of RV mass-to-volume ratios should, however, take into account PVR and the acuity of the disease. For example, a lower mass-to-volume ratio would not necessarily indicate worst adaptation but may also be reflective of lower PVR. In contrast to the mass-to-volume ratio, metrics of RV function such as right ventricular ejection fraction (RVEF) or RV global longitudinal strain have been more validated and appear to be more robust metrics (2). Another concept related to ventricular function is the concept of proportionality of ventricular adaptation; for example, although a slight decrease in RVEF is expected in patients with a slight increase in PVR (e.g., 5 Wood units), a moderate to severe decrease in RVEF would be disproportional. Future studies are needed to identify a simple metric for the proportionality of ventricular adaptation and to determine its role in outcome analysis. In conclusion, risk prediction in patients with PAH can be simplified using quantitative measures of right heart size and function, but, as the authors highlight in their letter, a simple score is unlikely to capture the complexity of risk stratification.
Please note: The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
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