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Published on: February 16, 2016
Risk stratification and prognostic assessment by myocardial perfusion-gated SPECT in patients with left bundle-branch
Luca Nai Fovino1, Giorgio Saladini, Gino Paolo Mormino
1Department of Cardiac, Thoracic and Vascular Sciences, University of Padua, Padua, Italy.
Insights
Gated SPECT effectively assesses cardiac risk in patients with left bundle-branch block (LBBB). The summed difference score (SDS) from myocardial perfusion imaging is the sole independent predictor of cardiac events in this population.
Area of Science:
- Cardiology
- Nuclear Medicine
- Diagnostic Imaging
Background:
- Left bundle-branch block (LBBB) complicates risk stratification in cardiac patients.
- Previous studies indicated functional parameters, not perfusion, offer prognostic value in high-risk LBBB patients.
Purpose of the Study:
- To evaluate the prognostic capability of gated single-photon emission computed tomography (SPECT) in patients with low-to-intermediate cardiac risk and LBBB.
Main Methods:
- 176 patients underwent 99mTc sestamibi-gated SPECT, divided into groups with (n=90) and without (n=86) LBBB.
- Patients were followed for cardiac events over 32 months.
- Cox regression and Kaplan-Meier analyses were employed.
Main Results:
- Patients with LBBB showed significantly higher rates of abnormal myocardial perfusion (67% vs 37%) and ischemia (53% vs 34%).
- The summed difference score (SDS) was the only independent predictor of cardiac events in both overall and LBBB groups (HR 3.08 and 4.99, respectively).
- Event-free survival was significantly lower in patients with abnormal scans and those with LBBB.
Conclusions:
- Gated SPECT provides valuable perfusion and functional data in LBBB patients.
- The summed difference score (SDS) is a critical independent predictor of cardiac events in LBBB patients.
- Gated SPECT's assessment of reversible ischemia aids in stratifying cardiac risk for LBBB patients.
Objective:
In high-risk patients with left bundle-branch block (LBBB), functional but not perfusion parameters yield incremental prognostic information. The aim of our study was to evaluate the prognostic value of gated single photon emission computed tomography (SPECT) in low-intermediate risk LBBB patients.
Methods:
One hundred seventy-six subjects underwent stress-rest dual-day protocol 99mTc sestamibi-gated SPECT and were dichotomized in two groups: without LBBB (Group 1, n = 86) and with LBBB (Group 2, n = 90). Patients were followed for 32 ± 18 months. Cox regression multivariate analysis was used to determine which variable was the best predictor of cardiac event. Event-free survival curves were computed by Kaplan-Meier method.
Results:
Myocardial perfusion scintigraphy was abnormal in 32 and 60 patients for Groups 1 and 2, respectively (37 vs. 67 %, p < 0.001). In Groups 1 and 2, the mean summed stress score (SSS) was 3.7 ± 5.6 versus 6.7 ± 6.4, while the mean summed difference score (SDS) was 1.6 ± 2.5 versus 2.7 ± 3.3 (both p < 0.005); therefore 34 % of patients in Group 1 and 53 % of those in Group 2 presented myocardial ischemia. All functional parameters were significantly different between the two subsets (all p < 0.005). Follow-up was completed in 161 patients (92 %); 10 events occurred in Group 1 and 20 in Group 2 (14 vs. 25 %). The event-free survival was significantly higher in patients with normal than in those with abnormal scan (85 vs. 63 %, p < 0.005); moreover, the prognosis of patients with LBBB was significantly worse. At multivariate analysis, SDS was found to be the only independent predictor of cardiac events both in all patients and in LBBB population (HR 3.08, and HR 4.99, p < 0.05).
Conclusions:
This is the first study to assess the prognostic value of gated SPECT in patients with LBBB and low-intermediate cardiac risk. Both perfusion and functional data obtained by gated SPECT are different between patients with and without LBBB. However, SDS is the only predictor of events. Thus, the amount of reversible ischemia at gated SPECT has a discriminative power in stratifying the cardiac risk of LBBB population.
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