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KEYWORDS FOR DATASET: Medical, Biology, Physiology
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ACCOMPANYING DATA PROVIDED BY: Alan Garfinkel, PhD
UCLA, Department of Physiology
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GENERAL EXPLANATION OF THE STUDY
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This data is from a study that was trying to determine if a drug called
"dobutamine" could be used effectively in a test for measuring a
patient's risk of having a heart attack, or "cardiac event." For younger
patients, a typical test of this risk is called "Stress Echocardiography."
It involves raising the patient's heart rate by exercise--often by having
the patient run on a treadmill--and then taking various measurements, such
as heart rate and blood pressure, as well as more complicated
measurements of the heart. The problem with this test is that it often
cannot be used on older patients whose bodies can't take the stress of hard
exercise. The key to assessing risk, however, is putting stress on the heart
before taking the relevant measurements. While exercise can't be used to
create this stress for older patients, the drug dobutamine can. This study,
then, was partly an attempt to see if the stress echocardiography test was
still effective in predicting cardiac events when the stress on the heart
was produced by dobutamine instead of exercise. More specifically, though,
the study sought to pinpoint which measurements taken during the
stress echocardiography test were most helpful in predicting whether or not
a patient suffered a cardiac event over the next year. The complete
citation for the journal in which the results of the study were published
is as follows:
Garfinkel, Alan, et. al. "Prognostic Value of Dobutamine Stress
Echocardiography in Predicting Cardiac Events in Patients
With Known or Suspected Coronary Artery Disease."
Journal of the American College of Cardiology 33.3 (1999) 708-16.
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BRIEF DESCRIPTION OF THE DATA
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The accompanying data file contains the complete data for the final
study population, which included 220 men and 338 women. The data collected
on each subject is explained below.
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HOW TO USE THE DATA FILE
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The actual data file is a comma delimited text file. The first row contains
the abbreviations for the information recorded on each subject. The remaining
rows each represent a single patient's corresponding information.
For the purposes of the study, the "cardiac events" that the "Dobutamine
Stress Echocardiography" was attempting to predict were broken down into
four categories:
CARDIAC EVENTS: (1) myocardial infarction (MI)
(2) revascularization by percutaneous transluminal
coronary angioplasty (PTCA)
(3) coronary artery bypass grafting surgery (CABG)
(4) cardiac death
If you're not familiar with medical jargon, you can simply think of these
as four things that can go wrong with your heart, and that the test was
trying to predict. In the datafile you can see whether or not a patient
suffered one of these cardiac events in the year following the patient's
test by looking in the columns marked "newMI", "newPTCA", "newCABG", and
"death". Note that, contrary to statistical convention, a "1" means that
the patient DID NOT suffer the corresponding cardiac event, and a "0" means
that he DID.
The other variables are explained below.
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EXPLANATION OF DATA MEASUREMENT ABBREVIATIONS IN THE DATA FILE
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bhr BASAL HEART RATE
basebp BASAL BLOOD PRESSURE
basedp BASAL DOUBLE PRODUCT (= bhr x basebp)
pkhr PEAK HEART RATE
sbp SYSTOLIC BLOOD PRESSURE
dp DOUBLE PRODUCT (= pkhr x sbp)
dose DOSE OF DOBUTAMINE GIVEN
maxhr MAXIMUM HEART RATE
%mphr(b) % OF MAXIMUM PREDICTED HEART RATE ACHIEVED BY PATIENT
mbp MAXIMUM BLOOD PRESSURE
dpmaxdo DOUBLE PRODUCT ON MAXIMUM DOBUTAMINE DOSE
dobdose DOBUTAMINE DOSE AT WHICH MAXIMUM DOUBLE PRODUCT OCCURED
age PATIENT'S AGE
gender PATIENT'S GENDER (male = 0)
baseEF BASELINE CARDIAC EJECTION FRACTION (a measure of
the heart's pumping efficiency)
dobEF EJECTION FRACTION ON DOBUTAMINE
chestpain 0 MEANS THE PATIENT EXPERIENCED CHEST PAIN
posECG SIGNS OF HEART ATTACK ON ECG (0 = yes)
equivecg ECG IS EQUIVOCAL (0 = yes)
restwma CARDIOLOGIST SEES WALL MOTION ANAMOLY ON ECHOCARDIOGRAM
(0 = yes)
posSE STRESS ECHOCARDIOGRAM WAS POSITIVE (0 = yes)
newMI NEW MYOCARDIAL INFARCTION, OR HEART ATTACK (0 = yes)
newPTCA RECENT ANGIOPLASTY (0 = yes)
newCABG RECENT BYPASS SURGERY (0 = yes)
death THE PATIENT DIED (0 = yes)
hxofHT PATIENT HAS HISTORY OF HYPERTENSION (0 = yes)
hxofdm PATIENT HAS HISTORY OF DIABETES (0 = yes)
hxofcig PATIENT HAS HISTORY OF SMOKING (0 = yes)
hxofMI PATIENT HAS HISTORY OF HEART ATTACK (0 = yes)
hxofPTCA PATIENT HAS HISTORY OF ANGIOPLASTY (0 = yes)
hxofCABG PATIENT HAS HISTORY OF BYPASS SURGERY (0 = yes)
any event THIS IS THE OUTCOME VARIABLE. IT IS DEFINED AS
"death OR newMI OR newPTCA OR newCABG". IF ANY OF
THESE VARIABLES IS POSITIVE (= 0) THEN "ANY EVENT"
IS ALSO POSTIVE (= 0).
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* THE FOLLOWING REMAINING VARIABLES ARE THE RESEARCHER'S *
* TECHNICAL CALCULATIONS AND THEY MAY BE IGNORED *
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phat
event(#)
mics
deltaEF
newpkmphr
gdpkmphr
gdmaxmphr
gddpeakdp
gdmaxdp hardness
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STATISTICAL TESTS AND ANALYSES USED IN THE STUDY
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1) Two-sample z-test (or p-test) for difference in mean.
2) Chi-square test for independence.
3) Logistic regression analysis.
4) the Hosmer/Lemeshow "goodness of fit" test.
5) CART analysis (Classification and regression tree analysis).