Prediction and stratification of the future cardiovascular arrhythmic events: Signal averaged electrocardiography versus ejection fraction.

Cardiac arrhythmias as cause of sudden cardiac death remains an important public health problem. The availability of effective treatment in terms of the implantable defibrillator makes it critical to identify individuals at risk. An essential step in this process is the use of noninvasive techniques to screen patients and identify those at risk. The detection of ventricular late potential using the SAECG as a non-invasive technique is being explored for this purpose. The objective of the study was to stratify the future cardiovascular events including life threatening cardiac arrhythmias, in different cardiac diseases through positive and negative predictive values of SAECG and comparing with EF% another mechanical determinant. The study was conducted on 152 subjects selected from the OPD and admitted case of the New Civil Hospital and Govt. Medical College, Surat; between 25 to 75 years of age group, from August 2001 to June 2004. 80 healthy subjects free from any major acute/chronic illness were selected as a control using our own normative values for SAECG. The statistical analysis was performed using SPSS package. The results obtained were analyzed for significance by using Chi square and Independent ‘t’ test. When we compared the cardiac arrhythmic events on 6 month follow-up study, based on SAECG and EF% separately we found that negative predictive value of SAECG was more (99.1%) than negative predictive value of EF% (93.6%). However positive predictive values for cardiac arrhythmic events of SAECG were less (28.9%) compare to EF% (42.9%).When both the parameters SAECG and EF% are considered together the negative as well as positive predictive values of these tests were quite high (100% and 50% respectively). In this study conducted on 152 patients we found that SAECG and EF% together were an accurate predictor of the cardiac arrhythmic events in terms of positive and negative predictive value while SAECG or EF% alone were not. However SAECG has got a more negative predictive value compare to EF%. In this study SAECG compared favorably or even better than EF% for risk stratification. SAECG and EF% together (and not separately) may be considered as a better investigational tool to stratify future cardiovascular arrhythmic events.

The changes in signal-averaged electrocardiogram after surgical correction of congenital heart disease / 소아과

PURPOSE: To analyze abnormal ventricular activation in childhood congenital heart disease induced by postoperative changes in ventricular volume and pressure and ventricular scar formation using signal-averaged electrocardiography (SAECG). METHODS: Fifty-two patients who had undergone open heart surgery (OHS) were enrolled. Patients were divided into the following 3 groups: right ventricular volume overload (atrial septal defect, group1), left ventricular volume overload (ventricular septal defect, group2), and right ventricular pressure overload (tetralogy of Fallot, group 3). The patients were monitored by standard 12-lead ECG and SAECG before and 2 months after the operation. QRS duration, QT and QTc intervals, filtered QRS (f-QRS), high frequency low amplitude potential (HFLA), and root mean square (RMS) voltage in the terminal 40 ms of SAECG were determined. RESULTS: In the preoperative period, group1 showed significant increase in QRS (P=0.011) compared to those of the other 2 groups. In the postoperative period, group3 showed significant increase in the QTc interval (P=0.004) compared to those in the other 2 groups. SAECG parameters showed no significant differences among the groups in the pre- or postoperative period. Of the 52 patients, 12 (23%) in the preoperative period and 21 (40%) in the postoperative period had at least 1 SAECG abnormality. The prevalence of SAECG abnormalities was significantly higher in the postoperative group 2 and group 3 (preoperative: 20% versus postoperative: 28%, P<0.001, preoperative: 14% versus postoperative: 64%, P<0.001, respectively). CONCLUSION: Abnormal SAECG patterns may be attributed to postoperative scars, OHS itself, and/or ventricular overload.

Effects of Patency of the Infarct-Related Artery on the Signal-Averaged ECG in Acute Myocardial Infarction

BACKGROUND: In patients after acute myocardial infarction, signal-averaged electrocardiography is used as the one of the non-invasive methods for the prediction for ventricular arrhythmia, one of the causes ofn death in acute myocardial infarction. Signal-averaged electrocardiography has allowed the identification of low-amplitude, high-frequency signals(late potentials)in the terminal portion of the QRS complex. They are thougt to be occured in the portion of electrophysiologically unstable myocardium. The presence of late potentials identifies regions of delayed conducton in the elctrophysiologically unstable border zone of an acute infarction. These electrophysiologic change of myocardium is influenced by the patency of infarct-related artery. A patent artery is associated with electrical stability of myocardium, decreased in cidence of late potentials and improved survival. METHODS: 58 patients of acute myocardial infarction underwent signal-averaged electrocardiography, coronary angiography within 10 days after AMI, 20 of healthy persons underwent signal-averaged electrocardiography. RESULTS: In patent group, late potentials were recorded in 7 of 38 patients(18%) as compared with 13 of 20 patients(65%) of non-patent group. The statistically significant parameters of signal-averaged electrocardiography beteen patent and non-patent group were filtered total QRS duration(TQRS, 106.7+/-20.9msec), high frequency low amplitude signal (HLAS, 30.8+/-7.5 vs 41.3+/-16.5 msec)with HLAS being the most powerful varialble in the model. CONCLUSION: These results suggest that the patency of infarct-related artery is associated with electrophysiologic stability of myocardium and signal-averaged electrocardiography is one of the useful non-invasive method in risk stratification of acute myocrdial infarction.

Comparision of signal - averaged electrocardiography (SAECG) determined by flank lead system (FLS) and pyramidal lead system (PLS) in healthy young adults / 영남의대학술지

It has recently become possible to record electrical activity originationg from abnormally conducting myocardium from the body surface with high-gain amplification and averaging technique. These signals, which result from delayed ventricular activation(late potentials), have been recorded in patients with documented ventricular tachyarrythmia. Several electrode lead system for detecting ventricular late potential were introduced. Pyramidal electrode lead system(PLS) is useful. Also interpretation of SAECG in the young could be of value in detecting those at risk for episodic ventricular tachycardia, but suffer from a lack of data in normal young people. There was no difference between normal values, determined by FLS and PLS at high pass filtering of 25 Hz and 80 Hz, but significant, difference was found in HFLAD and RMS-40 of 40 Hz (p<0.05). These results will provide a basis for interpretations of SAECG, determined by FLS and PLS in healthy young adults with normal QRS duration. SELECTION OF SUBJECTS: For this study, normal healthy young adult volunteers (age : mean 24 years) were recruited from the medical students at Yeungnam University Hospital, Internal Medicine. Twenty fourths male and seventeenths female subjects were selected. All subjects had normal resting ECGs as judged from both the standard 12 channel lead and echocardiography, and none had a history of cardiovascular disease. All subjects were considered to be in good general physical condition. SIGNAL-AVERAGED ELECTROCARDIOGRAPHY: In order to obtain low noise recordings with a small number of averaging cycles, all subject ware asked to relax completely in the supine position. Silver/silver chloride electrodes were attached after the skin was cleaned with alcohol, to constitute classic flank lead system(FLS) and pyramidal lead system(PLS). Signals were recorded and processed using a commercially available microprocessor-augmented ECG cart(Marquette Electronics, USA) suitable for portable bedside recording.