Diagnostic value of exercise electrocardiography for predicting a positive scintigraphic test in patients with complete right bundle branch block.
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.
Mammana
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Istituto di Cardiologia, Università degli Studi, Catania. hearttrnspl@cyberg.it
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Azzarelli
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Galassi
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Gulizia
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Rodi
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Giuffrida
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D000368:Aged; D002037:Bundle-Branch Block / Q000175:diagnosis* / Q000191:economics; D016001:Confidence Intervals; D003365:Costs and Cost Analysis; D004562:Electrocardiography / Q000191:economics / Q000379:methods / Q000706:statistics & numerical data; D005080:Exercise Test / Q000191:economics / Q000379:methods / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D011379:Prognosis; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000191:economics / Q000379:methods / Q000706:statistics & numerical data
D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C078700:technetium tc-99m tetrofosmin