e17Abstracts / Journal of Electrocardiology 44 (2011) e1–e64

Mikko Minkkinena, Tuomo Nieminenb,c,d, Richard L. Verrierb,Johanna Leinoa, Terho Lehtimäkie,f, Jari Viikg, Rami Lehtinena,h,Kjell Nikus i, Tiit Kööbia, Mika Kähönena

aDepartment of Clinical Physiology, Tampere University Hospitaland Medical School, University of Tampere, FinlandbBeth Israel Deaconess Medical Center, Harvard Medical School,Boston, MA, USAcDepartment of Pharmacological Sciences, Medical School,University of Tampere, FinlanddDepartment of Internal Medicine, Päijät-Häme Central Hospital,Lahti, FinlandeLaboratory of Atherosclerosis Genetics, Department of ClinicalChemistry, Tampere University Hospital, FinlandfMedical School, University of Tampere, FinlandgDepartment of Biomedical Engineering, Tampere University ofTechnology, FinlandhTampere Polytechnic – University of Applied Sciences, FinlandiHeart Centre, Department of Cardiology, Tampere UniversityHospital, Finland

Background: We tested the hypothesis that the prognostic capacityof clinically indicated exercise test is enhanced by combined analysisof exercise capacity, heart rate recovery (HRR), and T-wave alternans(TWA).Methods: A total of 3611 consecutive patients (2157 men) with a routineclinically indicated bicycle exercise test were included in the study from theFinnish Cardiovascular Study cohort. Patients with atrial fibrillation orflutter as well as patients with implantable cardiac devices were excluded.Exercise capacity was measured in metabolic equivalents (METs), HRR asdecrease in heart rate from maximum to 1 minute postexercise, and TWA bytime-domain modified moving average method. All the TWA values morethan 46 μV were overread by a physician. Cox regression analysis wasperformed with adjustment for sex, age, smoking, β-blocker therapy, andother common coronary risk factors.Results: During the median follow-up period of 56 months (interquartilerange, 35-78 months), there were 233 deaths. Of those, 96 were furthercategorized as cardiovascular deaths (primary end point). All 3 parameterswere independent predictors of death. The relative risk for cardiovasculardeath of low exercise capacity (MET b8) was 2.5 (95% confidence interval[CI], 1.4-4.7;P = .003); for reducedHRR (b19 beats/min), it was 2.1 (95%CI,1.3-3.3; P = .002); and for elevated TWA (at least 60 μV), it was 3.5 (95%CI,1.5-8.0; P = .003). The combination of the 3 parameters yielded relative riskfor cardiovascular mortality of 11.1 (2.9-42.6, P b .001) (Fig. 1) and for all-causemortality of 5.0 (1.5-17.2,P = .01) over patientswith none of the factors.

Fig. 1. Adjusted survival curves by Cox regression among patientsaccording to exercise capacity in metabolic equivalents (MET b8), heartrate recovery (HRR b19 beats/min) and exercise-based T-wave alternans(TWA at least 60 μV) for cardiovascular mortality. Numbers 0, 1, 2, and 3 inthe figure indicates the number of the positive parameters. Note that the scalefor the y-axis is from 0.875 to 1.00.

Conclusion: Exercise capacity, HRR, an index of parasympathetic activity,and TWA, a marker of cardiac electrical instability, both singly and incombination are strong predictors for cardiovascular mortality in patientsreferred for exercise testing.

doi:10.1016/j.jelectrocard.2010.12.049

O42ST-segment depression/heart rate hysteresis improves detection ofcoronary artery disease in womenKati Svarta, Rami Lehtinenc, Tuomo Nieminend,e, Kjell Nikus f,Terho Lehtimäkig,h, Tiit Kööbib, Kari Niemelä f, Väinö Turjanmaab,Mika Kähönenb, Jari ViikaaDepartment of Biomedical Engineering, Tampere University ofTechnology, FinlandbDepartment of Clinical Physiology, Tampere University Hospitaland Medical School, University of Tampere, FinlandcTampere Polytechnic —University of Applied Sciences, FinlanddDepartment of Pharmacological Sciences, Medical School, University ofTampere, FinlandeDepartment of Internal Medicine, Päijät-Häme Central Hospital,Lahti, FinlandfHeart Centre, Department of Cardiology, Tampere UniversityHospital, FinlandgLaboratory of Atherosclerosis Genetics, Department of ClinicalChemistry, Tampere University Hospital, FinlandhMedical School, University of Tampere, Finland

Background: The performance of exercise electrocardiography for thedetection of coronary artery disease (CAD) in women has been limited. ST-segment depression/heart rate (ST/HR) hysteresis has been proved to detectCAD in men more accurately than traditional methods, but the diagnosticperformance of ST/HR hysteresis in women is unclear.Methods: The study population comprised 161 female patients from theFinnish Cardiovascular Study. All patients were referred for a routinebicycle exercise test. The maximum values of ST/HR hysteresis, and ST/HR index, ST-segment depression at peak exercise (STpeak) weredetermined. Significant CAD was present in 48, whereas 65 womenshowed no angiographic CAD. Also, a group of 48 women with lowlikelihood of CAD was formed. Diagnostic performance of variables wasassessed by receiver operating characteristic (ROC) analysis. Furthermore,sensitivity values at 80% specificity and specificities at 80% sensitivitywere determined.Results: In a comparison between CAD and low likelihood of CADgroups, the ROC areas for ST/HR hysteresis, ST/HR index, and STpeakwere 0.89, 0.74, and 0.65, and sensitivities at 80% specificity were 88%,67%, and 52%, respectively. Comparing CAD and no-CAD groups, theROC areas were 0.73, 0.67, and 0.56, and specificities at 80% sensitivitywere 60%, 38%, and 27%.Conclusion: ST/HR hysteresis is a more competent method in the detectionof CAD in women than ST-segment depression or ST/HR index.

doi:10.1016/j.jelectrocard.2010.12.050

O43Spinal cord stimulation effects on myocardial ischemia, infarct size,ventricular arrhythmia, and noninvasive electrophysiology in a porcineischemia-reperfusion modelJacob Odenstedta, Bengt Linderothc, Lennart Bergfeldta, Olof Ekreb,Lars Gripa, Clas Mannheimerb, Paulin AndréllbaDepartment of Cardiology, Sahlgrenska University Hospital,Gothenburg, SwedenbMultidisciplinary Pain Center, Sahlgrenska University Hospital/Östra,Gothenburg, SwedencNeurosurgery, Karolinska Institute, Karolinska University Hospital,Stockholm, Sweden

e18 Abstracts / Journal of Electrocardiology 44 (2011) e1–e64

Background: Susceptibility to ventricular arrhythmias and sudden cardiacdeath can be reduced via modulation of autonomic tone. Spinal cordstimulation (SCS) presumably affects both the autonomic tone and reducesmyocardial ischemia. The aim was to investigate whether SCS could reducemyocardial ischemia, infarct size, and the occurrence of ventricular arrhythmiasas well as repolarization alterations in a porcine ischemia-reperfusion model.

Methods: Anesthetized common land-race pigs were randomized to SCS(n = 10) or sham treatment (n = 10) before, during, and after 45 minutes ofcoronary occlusion. Area at risk (AAR), infarct size (IS), and the amount ofspontaneous ventricular arrhythmias were analyzed. Continuous 3-Dvectorcardiography was recorded and analyzed with respect to ECGintervals, the ST-segment, and the T vector and T vector loop morphology.

Results: In the SCS group, ventricular arrhythmias occurred less frequently(P = .039), and the increase in ST-vector magnitude was less pronounced(P = .024). However, SCS showed no effect on AAR, IS, or IS/AAR.Tamplitude and Tarea increased in response to ischemia suggesting increasedrepolarization gradients, but SCS reduced these changes (P b .01 for both).No other parameters differed between the groups.

Conclusion: Spinal cord stimulation reduced the accumulated incidence ofspontaneous ventricular arrhythmias during ischemia-reperfusion in associ-ation with a reduction of repolarization alterations. Furthermore, vectorcar-diography signs of myocardial ischemia were reduced by SCS, but thisphenomenon was not accompanied by any effect on infarct size.

doi:10.1016/j.jelectrocard.2010.12.051

O44The cost-effectiveness of stress testing using high-frequency QRS analysisYizhar Torena, Linda R. Davratha, Shimon Abboudb, Guy AmitaaBiological Signal Processing Ltd, Tel Aviv, IsraelbTel Aviv University, Tel Aviv, Israel

Background: Exercise electrocardiogram (ECG) testing (EET), the first-line diagnostic for ischemic heart disease (IHD), is limited in accuracy, often

Fig. 1. Diagnostic workup model (left) and long-term outcome model (right) of isch

leading to superfluous imaging and angiography procedures. The HyperQstress test, based on computerized analysis of high-frequency QRScomponents of the ECG, provides an accurate index of myocardial ischemia,significantly improving the performance of EET. We analyzed the potentialeconomic and health care benefits of the improved diagnostic accuracy in theshort and long terms.Methods: A decision tree model (Fig. 1, left) was used to describe thediagnostic workup for IHD: All patients undergo either EET or HyperQ.Patients in whom IHD is not ruled out are referred to cardiac imaging (eg,single-photon emission computed tomography), followed by invasivecoronary angiography for positive cases. Confirmed IHD patients receivetreatment, whereas those misdiagnosed as healthy remain untreated. Basedon the proportions of treated and untreated patients, a prognostic Markovmodel (Fig. 1, right) was used to estimate cost of treatment during a givenperiod. The model stratifies the population into 6 outcome groups, by theoccurrence of acute coronary events, heart failure, or death. Usingparameters estimated from published data, the model was used to calculateshort- and long-term benefits of incorporating the HyperQ stress test into thestandard of care.Results: Sensitivity and specificity were 71% and 86%, respectively, for theHyperQ stress test, and 67% and 72% for EET, as previously reported. Witha disease prevalence of 10%, the improved specificity of HyperQ results in areduction of 13% in unnecessary imaging and 4% in angiographies. With anestimated 6 million yearly EET tests in the United States, the potentialimmediate annual savings amount to $1.2B. The long-term prognosticmodel, simulated over 20 years, demonstrated that the improved sensitivityof HyperQ entails a 4% reduction in the incidence of acute coronary events,5% reduction in heart failure, and 5% fewer deaths among IHD patients.These valuable effects are accompanied by a slight reduction in the overalllong-term medical costs and an increase in the quality-adjusted life years.Conclusion: The HyperQ stress test is a promising new tool for diagnosingIHD. Its improved performance compared with EET can reduce the numberof unnecessary cardiac imaging tests, thus lowering both medical costs andthe population's exposure to hazardous procedures while providingfavorable prognostic consequences.

doi:10.1016/j.jelectrocard.2010.12.052

emic heart disease. ACS indicates acute coronary syndrome; HF, heart failure.