ORIGINAL ARTICLE
Print ISSN 1738-5520 / On-line ISSN 1738-5555 Copyright ⓒ 2008 The Korean Society of Cardiology
Korean Circ J 2008;38:17-22
Prognostic Significance of the Lown Grades and Late Potentials in Patients after Myocardial Infarction Jin Bae Lee, MD, Young Soo Lee, MD, Seung Pyo Hong, MD, So Yeon Kim, MD, Moo Gon Kim, MD, Jae Kean Ryu, MD, Ji Yong Choi, MD, Kee Sik Kim, MD and Sung Gug Chang, MD Cardiology Division, Department of Internal Medicine, Daegu Catholic University Medical Center, Daegu, Korea
ABSTRACT Background and Objectives: The aims of this study were to assess the long term overall survival of patients after an
acute myocardial infarction (AMI), and to determine the association of survival with the occurrence of ventricular arrhythmia, as recorded by Holter electrocardiography (ECG) and signal-averaged electrocardiography (SAECG). Subjects and Methods: One hundred fifty two patients with an AMI were enrolled between January 2000 and August 2006. SAECG and Holter ECG were performed before hospital discharge (at range of 2-10 day). The grading system of Lown was used to evaluate the ventricular premature beats on Holter ECG. Three groups of patients were identified based on the seriousness of the ventricular arrhythmia, as identified by the Holter ECG: Lown grade 0, Lown grades 1, 2 and Lown grades 3, 4, 5. SAECG was performed with a high pass frequency of 25 Hz and 40 Hz. The presence of late potentials (LPs) recorded on SAECG was evaluated. The predictors for survival were assessed using Cox’s proportional hazard model and Kaplan-Meier analysis. Results: The mean duration of follow-up was 45.8±25.5 months. Twenty four patients (15.8%) died during follow-up. The multivariate predictors of all cause death included age [hazard ratio (HR)=1.25, 95% confidence interval (CI)=1.08-1.47, p=0.003] and Lown grades 3, 4 and 5 (HR=19.17, 95% CI=1.25-290.80, p=0.034). Survival analysis did not show a significant relationship between LPs and overall patient survival. The only predictors for overall mortality were age and the Lown grade. Conclusion: SAECG did not predict mortality for the patient with AMI. The ventricular arrhythmias recorded by conventional Holter before hospital discharge may be a useful noninvasive prognostic test after an AMI. (Korean Circ J 2008;38:17-22) KEY WORDS: Myocardial infarction; Prognosis; Holter electrocardiography.
late ventricular potentials are thought to correspond to slow, non-homogeneous conduction through the damaged myocardium.9-12) The incidence of LPs after an AMI decreases after successful thrombolysis as this results in the improved patency of the infarct-related coronary arteries.13)14) The LPs registered on the body surface appear to be a manifestation of delayed activation of the myocardium. For this reason, LPs have been useful for the stratification of the risk of sudden arrhythmic death during the post-infarction period.15) Holter-based risk variables have been suggested to be useful for screening patients who are at risk for sudden cardiac death among the survivors of AMI.16) The occurrence of non-sustained ventricular tachycardia (VT) on Holter electrocardiography (ECG) has been shown to predict mortality in several previous post-AMI studies.17-19) A previous study has shown that a reduced post-ectopic turbulence slope and non-sustained VT seem to provide information about the risk of future sudden cardiac death in the current treatment era, and particularly among the post-AMI patients
Introduction The incidence of coronary artery disease (CAD) has recently increased exponentially in Korea, and CAD is one of the most important causes of sudden cardiac death, including acute myocardial infarction (AMI).1) In the initial phase of AMI, the myocardial conduction is slowed due to the damaged myocardium. The slowed myocardial conduction is accompanied by a high incidence of late potentials (LPs).2-5) The presence of low amplitude, high frequency signals in the terminal part of the QRS complex has been associated with the onset of ventricular tachyarrhythmia and sudden death.6-8) The Received: May 8, 2007 Revision Received: December 10, 2007 Accepted: December 19, 2007 Correspondence: Young Soo Lee, MD, Cardiology Division, Department of Internal Medicine, Daegu Catholic University Medical Center, 3056-6 Daemyeong 4-dong, Nam-gu, Daegu 705-718, Korea Tel: 82-53-650-3041, Fax: 82-53-621-3166 E-mail:
[email protected]
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18·Lown Grades and Late Potentials after Myocardial Infarction
with slightly reduced or preserved left ventricular function.20) However, the clinical utility of Holter ECG together with the measurement of the signal averaged ECG (SAECG) is not well known. The aim of this study was to assess the long term overall survival after an AMI and determine the association of survival with ventricular arrhythmias, as recorded by conventional Holter ECG and the SAECG.
Subjects and Methods Study population One hundred fifty two patients with an AMI were enrolled into this study. We excluded those patients with evidence of a previous myocardial infarction, coronary angioplasty or aorto-coronary bypass surgery, atrial fibrillation or bundle branch block on the resting ECG. The diagnosis of an AMI was based on at least two of the following criteria: typical chest pain lasting >30 min, a diagnostic increase of the serum creatine kinase-MB (>3.6 ng/mL) and the presence of one of the following ECG findings: a ST elevation of 2 mm in at least two adjacent precordial leads and a ST elevation of 1 mm in the limb derivations. Signal-averaged electrocardiography Prior to discharge (range of the hospital stay: 2-10 days, average: 5 days), the patients were tested with SAECG for ‘time-domain analysis’ with using the X, Y and Z orthogonal leads of a M1754A SAECG (HewlettPackard Company, Oregon, USA). The SAECG was performed with the patient in the supine position and after a 15 minutes rest period. With a noise limit 114 ms, 2) the root-mean-square voltage of the last 40 ms of the QRS complex (RMS 25 Hz) was 114 ms, 2) the root-mean-square voltage of the last 40 ms of the QRS complex (RMS 40 Hz) was
