Two Survival Tree Models for Myocardial Infarction Patients

In the search of a better prognostic survival model for post-acute
myocardial infarction patients, the scientists at the Technical
University of Munich's "Klinikum rechts der Isar" and the German
Heart Center in Munich have developed some new parameters using
24-hour ECG (Schmidt et al 1999). A series of investigations were
done using these parameters on different data sets and the Cox-PH
model (Schmidt et al 1999, Ulm et al 2000). This paper is a
response to the discussion paper by Ulm et al (2000), which
suggests a Cox model for calculating the risk stratification of the
MPIP data set patients including the predictors ejection fraction
and heart rate turbulence. The current paper suggests the use of
the classification and regression trees technique for survival data
in order to deduct a survival stratification model for the NIRVPIP
data set. Two models are compared: one contains the variables
suggested by Ulm et al (2000) the other model has two additional
variables, namely presence of couplets and number of extra systolic
beats in the longest salvo of the patient's 24-hour ECG. The second
model is shown to be an improvement on the first one.