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Diagnostic value of exercise electrocardiography for predicting a positive scintigraphic test in patients with
C Mammana1, I D Cox, S Azzarelli
1Istituto di Cardiologia, Università degli Studi, Catania. hearttrnspl@cyberg.it
Insights
Exercise electrocardiography (ECG) has reduced diagnostic value for ischemia in patients with complete right bundle block (cRBBB). SPECT imaging may be a better first-line test for these individuals.
Area of Science:
- Cardiology
- Diagnostic Imaging
- Electrophysiology
Background:
- The diagnostic accuracy of exercise electrocardiography (ECG) for detecting myocardial ischemia in patients with complete right bundle branch block (cRBBB) is debated.
- Complete right bundle branch block can complicate the interpretation of standard exercise ECG tests.
Purpose of the Study:
- To evaluate the diagnostic accuracy of exercise ECG in identifying ischemia in patients with cRBBB.
- To compare the utility of exercise ECG in patients with cRBBB versus those with normal conduction.
Main Methods:
- A case-control study comparing 38 male patients with cRBBB to 38 matched controls with normal intraventricular conduction.
- Exercise ECG (modified Bruce protocol) and 99mTc-tetrofosmin single-photon emission computed tomography (SPECT) were performed.
- Exclusion criteria included left ventricular hypertrophy and prior revascularization.
Main Results:
- The diagnostic utility of exercise ECG was significantly lower in patients with cRBBB (0.1) compared to controls (0.28).
- ST-segment changes in lateral leads (V5-V6) showed better predictive accuracy than anterior leads (V1-V4) in cRBBB patients.
- Both positive and negative exercise ECG results had reduced diagnostic value in the cRBBB group.
Conclusions:
- Exercise ECG has diminished diagnostic value for ischemia in patients with cRBBB.
- SPECT imaging may be a more appropriate initial diagnostic tool for ischemia in this patient population.
- Lateral ECG lead analysis offers superior predictive accuracy compared to anterior leads in cRBBB.
Background:
The diagnostic value of exercise electrocardiography (ECG) in patients with complete right bundle block (cRBBB) remains controversial. The aim of this study was to investigate the diagnostic accuracy of exercise ECG for predicting ischemia in the presence of cRBBB.
Methods:
From a series of 1300 consecutive patients attending for exercise ECG and 99mTc-tetrofosmin single photon emission computed tomography (SPECT), we identified 38 male patients with cRBBB and 38 matched controls with normal intraventricular conduction. Patients with left ventricular hypertrophy or previous revascularization were excluded. Exercise ECG (modified Bruce protocol) was considered positive at > or = 1 mm ST horizontal or downsloping depression in > or = 2 adjacent leads. SPECT imaging at rest and post-exercise was performed at least 48 hours apart.
Results:
The odds ratio for ischemia comparing patients with positive and negative exercise ECGs was 11.0 (95% confidence interval 2.49-48.64, p = 0.002) in controls and 2.49 (95% confidence interval 0.64-9.08, p = 0.32) in cRBBB. The prior probability of ischemia was 0.37 in controls and 0.58 with cRBBB. The posterior probability after a positive test was 0.65 in controls and 0.68 in cRBBB. Thus, the utility of the test (posterior probability minus prior probability) was greater in controls (+0.28) than in cRBBB (+0.1). This difference was most pronounced in the anterior leads V1-V4 (controls +0.63 vs cRBBB +0.01) but less significant in the lateral leads V5-V6 (controls +0.26 vs cRBBB +0.21). Similar analysis also indicated reduced diagnostic value of negative exercise ECGs in cRBBB patients.
Conclusions:
The diagnostic value of exercise ECG is reduced in patients with cRBBB, although ST-segment changes in the lateral ECG territory provide superior predictive accuracy to those in the anterior leads. The use of SPECT as a first-line investigation may be justified in patients with cRBBB.