Performance of the signal-averaged electrocardiogram: relation to baseline QRS duration

QRS prolongation on the signal-averaged electrocardiogram versus ST-segment changes on the 12-lead electrocardiogram: which is the most sensitive electrocardiographic marker of myocardial ischemia?

BACKGROUND

ST-segment changes and QRS prolongation are electrocardiographic (ECG) markers of myocardial ischemia.

HYPOTHESIS

This study was undertaken to investigate the appearance of QRS duration changes with or without concomitant ST-segment changes during a typical anginal episode.

METHODS

For this purpose, 126 patients underwent 12-lead surface ECG and signal-averaged electrocardiogram (SAECG) during typical anginal pain as well as at the time the patient was asymptomatic. In both periods, QRS duration and ST-segment changes were evaluated. All patients underwent cardiac catheterization.

RESULTS

Of the 126 patients, 108 (86%) had coronary artery disease (CAD), whereas the remaining 18 (14%) patients had normal coronary arteriograms. During typical anginal pain, 75 of the 108 (70%) patients with CAD and 2 of the 18 (11%) patients with normal coronary arteriograms developed QRS prolongation, whereas 60 of the 108 (56%) patients with CAD and 2 of the 18 (11%) patients with normal coronary vessels developed ST-segment changes. Thus, the sensitivities of QRS prolongation measured by SAECG and of ST-segment changes on the surface ECG for the detection of myocardial ischemia were found to be 70 and 56%, respectively, (p < 0.01), whereas the specificities were both found to be 89% (p = NS).

CONCLUSIONS

During typical anginal pain, QRS prolongation on the SAECG is more sensitive than are ST-segment changes on the ECG for the detection of myocardial ischemia.

Portable-type signal-averaged electrocardiography with dipyridamole to detect patients with coronary artery disease

BACKGROUND

In a retrospective study portable-type signal-averaged electrocardiography (SAECG) with dipyridamole stress was found to identify patients with coronary artery disease (CAD) at their bedside with high sensitivity and specificity, so the utility of this method was prospectively investigated in the present study.

METHODS AND RESULTS

Standard 12-lead QRS wave SAECG was performed before and after dipyridamole stress at the bedside in 71 patients with chest pain (43 males, mean age 63 +/-9 years). The filtered QRS duration (fQRSd) before and after dipyridamole stress was determined by multiphasic oscillation method for each of the standard 12 leads, and the maximal value of changes in fQRSd (MAX DeltafQRSd) among the 12 leads was determined. The positive test was defined as MAX DeltafQRSd >or=5 ms, and negative as MAX DeltafQRSd <5 ms based on the previous study. Selective coronary arteriography was performed next. In the positive group (n=31), 25 patients had significant stenosis of the coronary artery and 6 did not. In the negative group (n=40), 5 patients had significant stenosis and 35 did not. The sensitivity, specificity, positive predictive accuracy and negative predictive accuracy for CAD detection by SAECG was 83%, 85%, 81% and 88%, respectively.

CONCLUSIONS

Dipyridamole-stress portable SAECG is useful for detecting CAD at the patient's bedside with high sensitivity and specificity.

Portable type signal-averaged electrocardiography with dipyridamole: a new and convenient method to detect patients with coronary artery disease and ischemia

BACKGROUND

Whether or not patients with coronary artery disease (CAD) could be easily detected at the bedside using dipyridamole stress was investigated using a portable type signal-averaged electrocardiography (portable SAECG).

METHODS AND RESULTS

The standard 12-lead QRS wave SAECG was performed at the bedside before and after dipyridamole stress in 30 patients with angiographically significant stenotic lesions, who had positive myocardial ischemia in the dipyridamole-thallium myocardial perfusion imaging (CAD group), and 33 patients with no significant stenotic lesions, who had negative imaging (control group). The filtered QRS duration (fQRSd) before and after dipyridamole stress was determined by the vector magnitude method and the difference (DeltafQRSd) was obtained. Furthermore, the DeltafQRSd was obtained using the multiphasic oscillation method, as well at the same standard 12-lead, and the maximal value of changes in fQRSd (MAX DeltafQRSd) between the 12 leads was determined. The DeltafQRSd was similar between 2 groups (p = 0.11). The MAX DeltafQRSd associated was significantly greater in the CAD group (p < 0.0001). When a cut-off value of MAX DeltafQRSd > or = 5 ms was used for the detection of CAD, the sensitivity and specificity were 97 and 94%, respectively.

CONCLUSION

The portable dipyridamole-stress SAECG easily detect CAD and myocardial ischemia at the bedside.

Long-term outcome of patients with unexplained syncope treated with an electrophysiologic-guided approach in the implantable cardioverter-defibrillator era

OBJECTIVES

We evaluated the long-term outcome of patients with coronary artery disease and unexplained syncope who were treated with an electrophysiologic (EP)-guided approach.

BACKGROUND

Electrophysiologic studies are frequently performed to evaluate unexplained syncope in patients with coronary artery disease. Patients with this profile who have inducible ventricular tachycardia are considered at high risk for sudden death and increased overall mortality, and therefore are often treated with an implantable cardioverter-defibrillator (ICD). The impact of this EP-guided strategy is unknown because there are no data comparing the long-term outcome of ICD recipients with that of noninducible patients.

METHODS

We evaluated 67 consecutive patients with coronary artery disease and unexplained syncope. All patients were treated with an EP-guided approach that included ICD implantation in patients with inducible ventricular tachycardia.

RESULTS

Electrophysiologic testing suggested a plausible diagnosis in 32 (48%) of these patients. Inducible monomorphic ventricular tachycardia was the most common abnormality. Despite frequent appropriate therapy with ICDs, the total mortality for patients with inducible monomorphic ventricular tachycardia was significantly higher than for noninducible patients. The respective one- and two-year survival rates were 94% and 84% in noninducible patients and 77% and 45% in inducible patients (p = 0.02).

CONCLUSIONS

Electrophysiologic testing suggests an etiology for unexplained syncope in approximately 50% of patients and risk stratifies these patients with regard to long-term outcome. Patients who receive an ICD for the management of inducible ventricular tachycardia have a high incidence of spontaneous ventricular arrhythmias requiring ICD therapy. However, despite ICD implantation and frequent appropriate delivery of ICD therapies, patients with inducible ventricular tachycardia have a significantly worse prognosis than do those who are noninducible.

Mismatch between myocardial accumulation of 123I-MIBG and 99mTc-MIBI and late ventricular potentials in patients after myocardial infarction: association with the development of ventricular arrhythmias

BACKGROUND

Late ventricular potentials are widely used to predict life-threatening arrhythmias, although the predictive value is low. To improve prediction, we correlated the incidence of ventricular arrhythmias with mismatches in myocardial 99mTc-methoxyisobutylisonitrile (MIBI)/(123)I-metaiodobenzylguanidine (MIBG) accumulation and late ventricular potentials (LP).

METHODS AND RESULTS

Fifty patients with old myocardial infarctions were divided into an LP-positive group (n = 19) and an LP-negative group (n = 31). On bull's-eye single photon emission computed tomographic MIBI and MIBG images, the heart was divided into 9 segments to evaluate the accumulation of the 2 nuclides. There was no difference in total defect score (TDS) for MIBI between the LP-positive and LP-negative groups. However, TDS for MIBG and differences TDS between MIBI and MIBG (ATDS) were significantly greater in the LP-positive group.

CONCLUSIONS

The incidence of severe ventricular arrhythmias was greater among patients with an increased ATDS in the LP-positive group. Thus the combination of these two methods may improve the prediction of ventricular arrhythmias after myocardial infarction.

Precordial QT dispersion and inducible ventricular tachycardia

We compared the performance of precordial QT dispersion, late potentials on the signal-averaged electrocardiogram (ECG), and reduced left ventricular ejection fraction for identification of inducible ventricular tachycardia (VT) in 162 patients undergoing electrophysiologic study (EPS). QT(apex) dispersion in 56 patients with inducible VT (72 +/- 55 msec) was greater than that in 106 patients without inducible VT (55 +/- 36 msec, p < 0.01); dispersion was greater in both groups than in 144 normal subjects (33 +/- 19 msec). A QT(apex) dispersion partition of more than 68 msec, the upper ninety-fifth percentile in normal subjects, identified inducible VT with a specificity of 75% and a sensitivity of 45%. Although the performances of late potentials (specificity 82%, sensitivity 59%) and reduced ejection fraction (specificity 86%, sensitivity 54%) were each stronger than QT dispersion alone for identification of inducible VT, abnormal QT(apex) dispersion remained a significant additional predictor of inducible VT in a logistic regression model that included the three variables (specificity 78%, sensitivity 75%).