Effects of left bundle-branch block on cardiac structure, function, perfusion, and perfusion reserve: implications for myocardial contrast echocardiography versus radionuclide perfusion imaging for the detection of coronary artery disease.
BACKGROUND
We aimed to investigate the cardiac effects of left bundle-branch block (LBBB) using myocardial contrast echocardiography (MCE) to ascertain the value of MCE for detecting coronary artery disease (CAD) and to uncover the mechanism that affects the accuracy of single-photon emission computed tomography (SPECT) in these patients.


RESULTS
Sixty-three symptomatic LBBB patients (group A), 10 left ventricular ejection fraction-matched control subjects without LBBB and no CAD (group B), and 10 normal control subjects (group C) underwent resting echocardiography. Rest and vasodilator MCE and SPECT were undertaken in LBBB patients. Septal (SW) and posterior wall (PW) thickness, thickening, quantitative myocardial blood flow (MBF), and MBF reserve were measured. SW/PW thickness and percentage thickening ratios were lower (P<0.01 and P<0.05, respectively) in group A compared with both groups B and C, but resting SW/PW MBF and MBF reserve ratios were similar in all 3 groups. MBF reserve but not MBF was reduced in groups A and B (2.2+/-0.7 versus 2.2+/-0.2; P=0.98) compared with group C (3.1+/-0.5; P<0.01). SW thickness was an independent predictor (P=0.006) of SPECT perfusion defects in LBBB patients without CAD. MCE (92%) had a sensitivity similar to SPECT (92%); however, the specificity of MCE (95%) was superior (P<0.0001) to SPECT (47%) for the detection of CAD.


CONCLUSIONS
Despite asymmetrical reduction in SW thickness and function, MBF is preserved and MBF reserve is homogeneously reduced in LBBB patients with left ventricular systolic dysfunction. Because of partial volume effects, the accuracy of SPECT for detecting CAD was significantly compromised compared with MCE in this patient cohort.
Hayat
S A
SA
Department of Cardiology and Institute of Postgraduate Medical Education and Research, Northwick Park Hospital, Harrow, UK.
Dwivedi
G
G
Jacobsen
A
A
Lim
T K
TK
Kinsey
C
C
Senior
R
R
D016477:Artifacts; D002037:Bundle-Branch Block / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003287:Contrast Media; D003326:Coronary Circulation; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D004452:Echocardiography; D018618:Echocardiography, Doppler, Color; D005189:False Positive Reactions; D006346:Heart Septum / Q000000981:diagnostic imaging*; D006801:Humans; D045423:Microbubbles; D012372:ROC Curve; D011859:Radiography; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon
D003287:Contrast Media; D017256:Technetium Tc 99m Sestamibi