DIAGNOSTIC IMPORTANCIg OF THE STATISTICAL VARIANCg O F E L E C ' r R O C A R D I O G I L A P l n c DATA Robert A. Wamcf, M.D., Ronald H. Seivesmr, M.D., Notma E Hill. R.N.. Galen S. Wagner, M.D Duke Universiw and Memorial Heart Institute, Dorlwa, North Carolina mul Long lkach California, USA

We studied the digital electrocardiographic da~ o f the QRS com- plexes o f Lead AVF o f 66 notmals - Group 1 - and 54 patients with aagiographi¢ ~ o f healnd inferior myocardial infarction (IMI) -Group 2. FOC evaW 4 naoc. interval o f sampling in all 120 pa- tiene;, we used l ie mean= and standard deviations (SD) o f the volts lo fGroups I and 2, respectively, to cal©ulme Z scores in relation to the population ofnosnmls mid the poltmll~ioa of[mtiena; with IMI. One cai~-~int~ Z score.s by dividing the differencea between the dam o f an individual and the mea~ data o f a population by the SD o f the data of the population. Therefore, Z scores, unlike simply the dif-

between individual and mean data, account for the vminace o f the daga in the p o ~ o a to which the individual is being corn- pined. For each interval ofsampliag for all the patients, we then suberacted the aommi Z score from the IM] Z score to yield the Z difference. Finally, we ¢ompmed the diagnostic peffommnces o f the differences in volts vs. the Z diffesenees:

Parameter Saocifi~w Sensidvitv Difference in Volts 93.3% 74.1%

Z D i ~ c e 93.3% 93.3% At the same level o f specificity, the Z difference is more sensitive than the difference in QRS voltage for diagnosing healed [MI.

Poster Session I 49

Analysis of microscopic alternans of T wave and monophasic ac t ion po ten t i a l Ken-ichi Ogata, Takurou Shinada, Shuichi Shimizu, Norihiko Ohno, Atsunobu Nomura, Masaaki Yashima, Yoshiyuki Hirayama, Yoshinori Kobayashi, Hirokazu Saitoh, Hirotsugu Atarashi, Takao Katoh, Hirokazu Hayakawa First Department of Internal Medicine. Nippon Medical School, Tokyo, Japan

BACKGROUND: Microvolt level T wave altemans (,uV-TWA),detected by CH2000 (Cambridge Henri Inc), attracted attention as an index of lethal ventricnlar arrhythmias. However, the characteristics of/z V-TWA is obscure. PURPOSES: To evaluate the possibility of analysis of microscopic TWA (m-TWA) and microscopic monophasic action potential altemans (m-MAP-A)

as an analogy to/zV-TWA. METHODS :Atrial pacings of 150 beats with cycle length of 500, 400 and 300msec were done in 7 open chest mongrel dogs. Suction eleOr~es and monopolar electtedes were placed on LV apex, base and in between them. Franz catheter was also placed in the LV apex. Monopolat ECG and MAPs were recorded from individual electrode and sampled with frequency of 500Hz. Areas under T waves were measured as 10msec width strips from the upstroke of QRS. Time series data of the area at the same time relative to the QRS were constructed. Altemans amplitude was defined as {(A-B)/B} X 100%;where A and B were the areas of consecutive beats with A>B. Positive m-TWA was defined as altemans amplitude of any timing exceed 0.2% constantly during 150 beats. Positivity of m-MAP-A was determined in the same mannes RESULTS: Although no visible altemans was detected in any experiment, m-TWA was detected 5 out of 7 dogs only with the shortest cycle length of 300msec.m-MAP-A tended to appear with shorter the pacing cycle length in each recording, m-TWA was always associated with m-MAP-A. CONCLUSION Both m-MAP-A and m-TWA could be reliably analyzed by the automatic process.

EvaIoahon of venmcular repolanzahon using surtace bC~ --comparison between QT, ARI, and QRSTi--- Nonhiko Ohno, Hirokazu Saitoh, Ken-ichi Ogata, Talmya Ono, Atsunobo Nomura, Hirotsugu Atarashi, Takao Katoh, Himkazu Hayakawa, First Department of lntemal Medicine, Nippon Medical School, Tokyo, Japan

BACKGROUND. QT dispersion of 12 leads ECG was used as an index for inhomogeneity of ventricular repolarization, Although activation recovery interval (ARt) and integral of QRST (QRSTi) arc also used as indices for ventricular repolarization, the relation between QT and the two parameters has not been elucidated yet. We compared the changes between each parameter produced by several autonomic stresses. METHODS. Fourteen pts without underlying heart disease were included. Body surface ECG (87 leads) were recorded in control, during cold pressor test and after administration of each drag, i.e. atropine, isoproterenol, propranolol, phenylephrine and phentolamine. We designed 4 electrodes near V1 and V2 as area A, 4 near V3 and V4 as area B, and 4 near V5 and V6 as Area C. QT, ARI and QRSTi were measured for each lead of each ares after each stress, i.e. 4 × 7=28 data were obtained for each parameter in each area. Correlation coefficient(r) between each two parameters was caluculated for each area and designed as r(QT-ARI), r(ARI-QRSTi), and r(QRSTi-ARI), respectively. RESULTS. (1)Significant positive correlation was obtained in 85.7% of area A, 71.4% of men B, 100% of area C for QT-ARI, and in 64.3% of area A, 71.4% of area B, 92.9% of men C for QT-QRSTi, and in 35.7% of area A, 57.1% of area B 85.7% of area C for ARI-QRSTi. (2) r(QT-ARI) was higher than r(QT-QRSTi)* and r(ARI-QRSTi)**in each area, respectively (* <0.10, ** <0.005). CONCLUSIONS. Highly positive correlation between ARI and QT indicated the similarity of the two indices and posibility of ARI dispersion to substitute for QT dispersion. On the other hand, QRSTi might have different characteristics compared with both QT and ARI.

The Incremental Prognostic Value of Therapy Responsive Continuous 12-lead ST-Segment Variables to Baseline Clinical Descriptors for the Prediction of Clinical Outcome After Acute Myocardial Infarction. Arthur Maas, Cindy Green, Kathleen Trollinger, Mitchell Krucoff. Duke University and VA Medical Centers, Durham, NC, USA 27510

Several patient descriptors have been associated with adverse clinical outcome after acute MI. We researched the incremental prognostic value of ST recovery parameters derived from digital continuous 12-lead ECG recordings when added to these adverse prognostic descriptors. 825 patients were analyzed from substudies of 6 major thrombolytic trials. ST recove~ parameters were: 'time to stable ST-recovery" and 'late ST elevation' after stable ST recovery. High-risk patients had >1 of the following GUSTO-I mortality model descriptors: age >70, systolic BP <110mmHg, heart rate >90, anterior ]vii, or previous MI. High, moderate, and low risk ST-groups were defined by the presence of both slow ST recovery (>2hr) and late ST elevation, one or the other, or neither, respectively. Clinical endpoints were death, re-infarction, and congestive heart failure. "Combined outcome table, "13=.038, ** p<.001 (%)"

Low ST Moderate ST High ST Overall Low clin.risk* 211143 (15) 14/ 99 (14) 7/19 (37) 42/261 (16) High olin.risk** 64/274 (23) 70/219 (32) 33/71 (49) 167/564 (30) Overall ** 85/417 (20) 84/318 (26) 40/90 (44) 209/825 (25) Age, and heart rate were independent predictors of mortality(c-index:0.81) Late ST elevation added incremental information to these variables (c-index:0.84). Combined with baseline clinical descriptors, the use of therapy responsive ST variables derived from a continuous 12-lead ST monitoring device significantly enhances the ability to predict outcome.