High-frequency QRS electrocardiogram analysis during exercise stress testing for detecting ischemia.
BACKGROUND
ECG stress testing is an inexpensive and non-invasive detector of myocardial ischemia; addition of high-frequency QRS analysis (HFQRS) may improve accuracy. This study compared HFQRS during exercise in patients with and without ischemia as defined by multiple criteria.


METHODS
High-resolution ECGs were recorded for 139 patients undergoing T99-sestamibi/T201-thallium stress testing. Twenty-three were positive by at least two and 37 were negative for ischemia by all three of the following criteria: nuclear scan, ST-segment analysis and typical angina. Sixty-four not meeting criteria for positive or negative, six with adenosine test and nine patients with ECG recording artifacts were excluded. Mean age of the study group was 62+/-10 years, 83% were male. Ischemic patients had a higher incidence of previous myocardial infarction and coronary intervention than non-ischemic patients (74% vs. 46%; P=0.03 and 70% vs. 43%; P=0.05, respectively), but had a lower body mass index (28.7+/-5 vs. 33.0+/-8; P=0.015). HFQRS analysis consisting of signal averaging (150-250 Hz) and calculation of root mean squared values for each lead at different time points was performed and was similar between the groups. The relative change in HFQRS (RCQ) was calculated for each lead: {(maxHFQRS-minHFQRS)/maxHFQRS}. For each patient an RCQ index was calculated by averaging the two leads with the greatest RCQ value. The RCQ index was greater in ischemic vs. non-ischemic patients (45% vs. 34%; P=0.0069).


CONCLUSIONS
Maximum decrease in HFQRS, as quantified by RCQ index, was greater in ischemic vs. non-ischemic patients. Use of the RCQ index may improve the diagnosis of ischemia during exercise stress testing.
Lipton
Jonathan A
JA
Erasmus Medical Center, Rotterdam, The Netherlands. jonathanlipton@gmail.com
Warren
Stafford G
SG
Broce
Mike
M
Abboud
Shimon
S
Beker
Amir
A
Sörnmo
Leif
L
Lilly
Donald R
DR
Maynard
Charles
C
Lucas
B Daniel
BD
Wagner
Galen S
GS
D000368:Aged; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D004562:Electrocardiography / Q000379:methods*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis*; D011336:Probability; D012016:Reference Values; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D017256:Technetium Tc 99m Sestamibi
D017256:Technetium Tc 99m Sestamibi