I recently added a z-score calculator for age-adjusted pulmonary artery acceleration time (PAAT), based on the manuscript "Normal Reference Values and z Scores of the Pulmonary Artery Acceleration Time in Children and Its Importance for the Assessment of Pulmonary Hypertension" (Circ Cardiovasc Imaging., 2017;10).

The manuscript provides PAAT z-scores for various children using age and body size as the predictors. As long as the patient has an age-appropriate HR, age is probably a reasonably fair predictor. But I wonder if the primary factor that influences PAAT isn't just heart rate.

Using data from the manuscript "Table 3. Age-Specific PAAT Values", I plotted the average heart rate for the age groups vs the PAAT:


The second order polynomial equation suggested by Google Sheets fit the data quite nicely.

While I think it may seem obvious that the primary influence is HR— beyond that the actual relationship might be even more usefully described when HR is expressed as the heart period. Firstly, the pulmonary artery ejection time is measured in milliseconds, so it should be intuitively helpful to have our predictor use the same units. Secondly, The ejection time is, functionally, a portion of systole; systole comprises a fairly predictable portion of the entire heart cycle/period. Predicting the PAAT from the heart period seems mechanistically sound.


The fit through this data is also well described with a second-order polynomial equation.

Apart from the maturational decrease in heart rate with age, until the PAAT is adjusted for heart rate, I am not sure what conclusions can be drawn about the effect of age on pulmonary artery acceleration time.