Original Article
Myocardial perfusion SPECT identifies patients with left bundle branch block patterns at high risk for future coronary events

https://doi.org/10.1007/s12350-009-9183-9Get rights and content

Abstract

Background

The value of myocardial perfusion SPECT (MPS) for patients with left bundle branch block (LBBB) or right ventricular apical (RVA) pacing seems reduced. The prognosis of patients with only abnormal activation related perfusion defects (AARD) due to LBBB or RVA-pacing is similar to those with a normal MPS. We assessed the prognostic value of MPS in patients with LBBB or RVA pacing.

Methods

Patients with LBBB or RVA pacing referred for vasodilator stress MPS between April 2002 and January 2006 were analyzed. Group 1 are patients with normal MPS and MPS with AARD. Group 2 are patients with an MPS with a perfusion defect extending outside the AARD area. Events were cardiac death, acute myocardial infarction and coronary revascularization.

Results

In Group 1 (101 patients) 12 events and in Group 2 (96 patients) 45 events occurred during a mean follow-up of 2.6 ± 1.5 years. The prognosis of Group 2 was significantly worse (49%) compared with Group 1 (91%). The annual cardiac death rate was 0.7%/year in Group 1 and 6.4%/year in Group 2 (P < .001). The prognosis of patients with LBBB was not different from those with RVA pacing.

Conclusion

Group 2 had a significantly worse cardiac prognosis compared to Group 1. The annual cardiac death rate of <1% in Group 1 warrants a watchful waiting strategy, whereas the cardiac death rate in Group 2 warrants aggressive invasive coronary strategies.

Introduction

Epidemiological and clinical observations demonstrate that patients with left bundle branch block (LBBB) have a worse cardiovascular prognosis compared to patients with a normal QRS complex.1 LBBB is associated with increased age, hypertension, diabetes mellitus and congestive heart failure.1,2

Right ventricular apical (RVA) pacing, commonly resulting in a LBBB pattern, may evolve in unpredicted deterioration of left ventricular function (LVF).3,4 Even after pacemaker implantation, the cardiac prognosis of chronically paced patients is unclear.

Non-invasive coronary risk-stratification of patients with chest pain and LBBB or RVA pacing is challenging because ventricular conduction is intrinsically abnormal and delayed.5 The abnormal activation pattern frequently induces wall motion abnormalities,5,6 abnormal wall thickening7, 8, 9 and myocardial perfusion defects,10 which hampers the diagnostic accuracy of non-invasive coronary risk-stratification with stress-testing.9,11, 12, 13

We recently demonstrated that combined perfusion/contraction defects due to abnormal activation can easily be defined with gated myocardial perfusion single photon emission computed tomography (MPS) and in most cases can be distinguished from other causes of decreased regional myocardial14 perfusion.

The cardiac prognosis of patients with only abnormal activation related perfusion defects in otherwise normal perfused hearts is the same as in patients with the same conduction characteristics but completely normal myocardial perfusion.14 Obviously, the specific myocardial perfusion defects are strictly related to abnormal electrical activation.

We hypothesized that the worse cardiovascular prognosis of patients with chest pain and an LBBB pattern can solely be determined by perfusion abnormalities outside of the myocardial area surrounding the abnormally activated area.

The aim of our study was to demonstrate the relationship between the occurrence of stress-induced myocardial perfusion defects and the cardiovascular prognosis in patients with abnormal activated myocardial perfusion defects due to LBBB or RVA-pacing.

Section snippets

Methods

Data of consecutive patients with LBBB or RVA pacing and chest pain who were referred for vasodilator stress MPS between April 2002 and January 2006 were retrospectively analyzed. Further treatment after MPS was left to the discretion of the treating cardiologist. Excluded were patients with instable ventricular pacing during the MPS protocol, patients with bi-ventricular pacing, and patients in whom gated acquisition was not technically feasible. Patients were categorized according to the MPS

Patients

Between April 2002 and January 2006, a total of 2,454 adenosine stress MPS studies were performed. In 226 (9.2%) patients, a LBBB pattern or right ventricular pacing was present. Six patients were excluded because no ventricular pacing was present at the time of the MPS, eight patients because gating was not possible, six patients due to atrial arrhythmia, and two patients were excluded because of frequent ventricular ectopy during MPS acquisition and seven patients were excluded because the

Discussion

Our hypothesis was that myocardial perfusion SPECT in patients with LBBB or RVA pacing can differentiate between those with a low or with a high risk for future cardiac events. From the results of our study it became obvious that the cumulative cardiac event-free follow-up was significantly worse in patients with perfusion defects extending outside the area related to abnormal activation compared to patients with a normal perfusion or just AARD. Secondly, despite more coronary interventions

Advantages of Detecting AARD

The presence of AARD can be identified with the concomitant analysis of the myocardial perfusion SPECT images and wall motion analysis based on the gated-SPECT information. With the triad of (a) abnormal activation pattern by presence of LBBB or RVA pacing, (b) wall motion abnormalities and (c) perfusion abnormalities in pre-defined regions and otherwise normal myocardial perfusion, AARD can be appreciated.14 Since our assumption implies that AARD is strictly related to abnormal activation

Limitations

This is an observational retrospective outcome study using the original assessment made by the two observers in a single institution. Secondly, the patient characteristics of our study show a relatively old age and high pre-test probability for CAD (Table 1). Therefore, whether this also holds true for a patient population at lower cardiac risk remains to be determined. Third, patients in Groups 1 and 2 demonstrated different baseline characteristics. Because patients were categorized based on

Conclusions and Clinical Implications

The results of this study show that in patients with LBBB or LBBB related to right ventricular apical pacing, adenosine stress gated-SPECT can distinguish between patients with a low risk for future cardiac events and patients at high risk for future cardiac events. The cumulative cardiac death and AMI free follow-up was 94% in patients with a normal scan or not more than AARD and 67% in patients with perfusion defects extending outside this specific area after a mean follow-up of

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    This study was supported by an educational grant by Medtronic Trading NL B.V., Heerlen, The Netherlands.

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    Copyright © 2010 American Society of Nuclear Cardiology. Published by ELSEVIER INC. All rights reserved. Published by Mosby, Inc. All rights reserved.