World Journal of Surgery

, Volume 37, Issue 5, pp 1169–1173

Role of Pre-operative Multiple Gated Acquisition Scanning in Predicting Long-Term Outcome in Patients Undergoing Elective Abdominal Aortic Aneurysm Repair

Authors

  • Hashem M. Barakat
    • Academic Vascular Surgical UnitVascular Laboratory, Hull Royal Infirmary, Hull York Medical School, University of Hull
    • Academic Vascular Surgical UnitVascular Laboratory, Hull Royal Infirmary, Hull York Medical School, University of Hull
  • Junaid A. Khan
    • Academic Vascular Surgical UnitVascular Laboratory, Hull Royal Infirmary, Hull York Medical School, University of Hull
  • Peter T. McCollum
    • Academic Vascular Surgical UnitVascular Laboratory, Hull Royal Infirmary, Hull York Medical School, University of Hull
  • Ian C. Chetter
    • Academic Vascular Surgical UnitVascular Laboratory, Hull Royal Infirmary, Hull York Medical School, University of Hull
Article

DOI: 10.1007/s00268-013-1939-3

Cite this article as:
Barakat, H.M., Shahin, Y., Khan, J.A. et al. World J Surg (2013) 37: 1169. doi:10.1007/s00268-013-1939-3
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Abstract

Objective

To determine whether resting pre-operative left ventricular ejection fraction (LVEF) estimated by multiple gated acquisition scanning (MUGA) predicts long-term survival in patients undergoing elective abdominal aortic aneurysm (AAA) repair.

Methods

A retrospective study of MUGA scans which were performed to estimate pre-operative resting LVEF in 127 patients [106 (83 %) males, mean age 74 ± 7.6 years] who underwent elective AAA repair over a period of 4 years from March 2007. We compared outcomes and long-term survival between patients who had a pre-operative LVEF ≤ 40 % (Group 1, n = 60) and LVEF > 40 % (Group 2, n = 67).

Results

Overall 19 (15 %) patients died during the follow-up period (13 patients in group 1 and 6 patients in group 2). 30-day mortality was 8 %. There was no significant difference between group 1 and 2 in terms of patients’ mean age or median length of hospital stay (8 days for both groups, p = 0.61). However, group 2 had more females than group 1(18 vs. 3, p = 0.001). Median survival for patients in group 2 was significantly higher than patients in group 1 (1,258 days vs. 1,000 days, p = 0.03). In a Cox regression model which included age, sex, smoking status and LVEF as covariates, only smoking status and LVEF predicted survival [Hazard ratio (HR) = 1.06, p = 0.04 and HR = 0.93, p = 0.00, respectively].

Conclusion

This study shows that there is a role for pre-operative MUGA scan assessment of resting LVEF in predicting long-term survival post elective AAA repair and that the lower the pre-operative LVEF the poorer the long-term outcome.

Introduction

Cardiac complications remain the major contributors to morbidity and mortality in patients undergoing major vascular surgery [14]. Evaluation of cardiac function is a cornerstone in the preoperative assessment of moderate to high risk patients [58]. A high proportion of patients with abdominal aortic aneurysms (AAA) have co-existing coronary artery disease, so a significant percentage of deaths following open AAA repair remains cardiac in origin. The measurement of left ventricular ejection fraction (LVEF) is historically considered a valuable assessment tool in patients with heart failure and chronic coronary artery disease [9, 10]. It provides functional and prognostic information and aids in monitoring the response to treatment. LVEF can be measured using a variety of invasive and non-invasive methods [11]. Radionuclide ventriculography (RVN) by the multi-gated acquisition scan (MUGA) is a widely used imaging technology that allows interpreters to estimate LVEF and study myocardial wall motion dynamics using a gamma camera. Conflicting reports in literature specifically assessed the ability of MUGA scans to predict cardiac outcomes in open surgery for AAAs. There is uncertainty as to whether it provides any additional value as opposed to other tests in the short-term [12, 13]. The specific role of LVEF estimated using MUGA in predicting long-term survival remains unclear.

Methods

This was a retrospective study of prospectively collected data on 127 patients who underwent elective open repair of AAA who had LVEF estimated preoperatively via MUGA scans. Data was collected over a period of 4 years from March 2007. All scans were performed within 1 month preoperatively. MUGA scans were performed using a standard ECG-gated technique. Red blood cells were labelled with Technetium-99m in vivo after stannous pyrophosphate priming. A three-lead ECG was then used to give distinct R wave trace to enable the gated acquisition cycle. Imaging was done in two planes. Using an Infinia® (General Electric) Gamma camera, a left anterior oblique 40° projection was taken for 7 min followed by a 70° projection also for 7 min producing 32 frames per each R–R gated cycle. The global LVEF was computed using the Xelenis® functional imaging locally developed software (General Electric) which enables the interpreter to hand mark the region of interest, i.e. left ventricle. LVEF was determined in the usual manner by subtracting end-systolic from end-diastolic counts and dividing this by end-diastolic counts. Using this method the LVEF was considered normal when it was >40 %. It is worth mentioning, that at the department of nuclear medicine, the locally developed software was vigorously tested to show excellent inter-observer and intra-observer reproducibility. Based on the MUGA scan interpretation; which was provided by the same nuclear cardiologist, high cardiac risk patients were referred for cardiology consultation and any further cardiac interventions were decided by the cardiologists.

Statistical analysis

A Statistical Package for the Social Sciences Program (SPSS) version 19 for Windows (SPSS Inc. Chicago, IL) was used for statistical analysis. Continuous variables were expressed as mean ± SD for parametric variables and median (interquartile range) for non-parametric variables. Categorical data was presented as the number of subjects and percentage. Comparison between the groups was performed using unpaired t test for parametric variables and Mann–Whitney U test for non-parametric variables. Chi square test was used for categorical variables. Survival was calculated from the date of operation until the date of death or date of last follow-up. If patients did not attend for follow-up, the general practitioner was contacted to confirm the survival status. Kaplan–Meier survival function was used for survival analysis and the log-rank test was used for survival comparison between the two groups. Cox’s proportional hazard regression model was used to identify factors associated with long-term postoperative outcome. All statistical tests were two sided and a p value <0.05 was considered to be significant.

Results

Data on MUGA scans were available for 127 patients [106 (83 %) males, mean age 74 ± 7.6 years] who underwent elective AAA repair over the study period. Mean LVEF for all patients was 42.3 ± 10.3 %. Patients were divided into two groups according to their pre-operative LVEF. Group 1 had LVEF ≤ 40 % (n = 60) and Group 2 had LVEF > 40 % (n = 67). There was no significant difference between group 1 and 2 in terms of patients’ mean age or median length of hospital stay (8 days for both groups, p = 0.61). However, group 2 had more females than group 1 (18 vs. 3, p = 0.001) (Table 1).
Table 1

Patients characteristics in the two groups

Characeristics

Group 1 (n = 60)

Group 2 (n = 67)

p value

Age (years)

74 ± 8.7

75 ± 6.5

0.389

Female, n (%)

3 (5)

18 (27)

0.001*

LVEF (%)

33.9 ± 6.8

49.8 ± 6.6

<0.001*

Current smokers (%)

13

24

0.224

Hypertension (%)

51

55

0.309

IHD (%)

40

30

0.052

Diabetes mellitus (%)

20

10

0.292

Hypercholesterolaemia

33

34

0.906

Aspirin (%)

55

56

0.632

Statins (%)

68

69

0.504

Antihypertensives (%)

55

65

0.292

p value <0.05

Overall, 19 (15 %) patients died during the follow-up period (13 patients in group 1 and 6 patients in group 2) and 30-day mortality for all patients was 8 %. Median survival for patients in group 2 was significantly higher than patients in group 1 (1,258 days vs. 1,000 days, p = 0.03) (Fig. 1). In a Cox regression model which included age, sex, smoking status (Current or non-smoker), use of Aspirin, use of Statins and the group allocation based on LVEF as covariates, only smoking status and group allocation predicted survival [Hazard ratio (HR) = 4.21, p = 0.020 and HR = 3.41, p = 0.032, respectively]. LVEF ≤ 40 % (Group 1) was associated with a 3-fold increase in the risk of death after adjustment for all of the explanatory variables in the model when compared with group 1 (LVEF > 40 %). On the other hand, current smoking status was associated with a 4-fold increase in the risk of death compared to non-smokers. The effect of different variables on long-term survival is summarised in Table 2.
https://static-content.springer.com/image/art%3A10.1007%2Fs00268-013-1939-3/MediaObjects/268_2013_1939_Fig1_HTML.gif
Fig. 1

Kaplan-Meier survival analysis comparing between the two groups

Table 2

Multivariate analysis of factors affecting long-term survival

Variable*

Regression coefficient

Hazard ratio

95 % Confidence interval

p value

Age

0.008

1.00

0.95–1.06

0.796

Gender

0.365

1.44

0.35–5.81

0.608

Smoking

1.439

4.21

1.25–14.13

0.020†

Group

1.229

3.41

1.11–10.48

0.032†

Diabetes

−0.542

0.58

0.14–2.41

0.456

Renal disease

−0.068

0.93

0.10–7.98

0.951

Ischaemic heart disease

−0.495

0.61

0.22–1.69

0.342

Hypertension

−0.257

0.77

0.26–2.28

0.643

* Gender is coded as (1 = female, 0 = male), smoking (1 = current smoker, 0 = non-smoker), group (1 = LVEF ≤ 40 %, 0 = LVEF > 40 %), diabetes (1 = yes, 0 = no), renal disease (1 = yes, 0 = no), ischaemic heart disease (1 = yes, 0 = no), hypertension (1 = yes, 0 = no)

†Statistically significant (p < 0.05)

Discussion

This study shows that LVEF measured by MUGA scan independently predicted long-term mortality in patients undergoing elective AAA repair. Patients with LVEF < 40 % were at higher risk of death compared to patients with normal cardiac function. Kazmers et al. [14, 15] were the first to show that low LVEF measured using RVN correlates with poor long-term survival. Their patient sample size, however, was about half the sample size we studied here. Our patient group is one of the largest cohorts reported investigating the effect of LVEF measured using MUGA scan on long-term outcome specifically for elective AAA repairs.

It has been shown that cardiac damage in patients with AAA is generally associated with poor long-term outcome [16]. Left ventricular function has long been considered one of the most important measurements to determine the effects of acquired heart disease and is the single most important prognostic parameter in patients with coronary artery disease [17, 18]. Therefore LVEF estimation is recommended prior to cardiac and non-cardiac peripheral vascular surgery [19] and MUGA scanning provides a reasonably cost effective way of estimating LVEF.

Nonetheless, several studies failed to demonstrate the value of LVEF measurement using MUGA scan as a predictor of cardiac outcome in the short-term or the mid-term. However, with the addition of stress (e.g. exercise), MUGA scanning may provide a measure of LVEF that can be of more use. Kertai et al. compared the prognostic accuracy of several diagnostic tests for the purpose of cardiac risk stratification in major vascular surgery, concluding that dobutamine-stress echocardiography (DSE) shows better promise where there is left ventricular dysfunction [20].

Other parameters like dynamics of ventricular wall motion can be also assessed via MUGA scans. Karkos et al. [21] reported that the presence of ventricular wall motion abnormalities was a useful predictor of postoperative cardiac events, and concluded that resting MUGA scan is a useful screening preoperative test.

Patients at high risk of cardiovascular complications can also be identified using various risk scores. The most validated risk score indices are the Glasgow Aneurysm Score (GAS) [22] and the Revised Cardiac Risk Index (RCRI). These, however, may not be as applicable in the endovascular era [23, 24] and new emerging scores will certainly prove useful [2528].

Radioisotope LVEF estimation is accurate and reproducible [2931], therefore it gained a considerable recognition in the preoperative assessment prior to major vascular surgery. In the UK it was the second most popular assessment tool prior to elective AAA repair in a survey done in 1996 [32]. In the USA, it was used in 33 % of cases as well during the same period [33]. The use of MUGA is however declining, presumably due to emerging technologies of cardiac imaging. A revisit to the value of MUGA scanning in screening and outcome prediction in this day and age will provide the clinician with more recent insight on choosing the best modality of cardiac risk stratification for individual patients.

The limitations of the current study must be acknowledged. We included data for patients undergoing elective open repair of AAA, as it is generally associated with higher early morbidity when compared to endovascular repair. The current interest is in studying such traditionally useful tools to assess their accuracy in predicting outcomes following EVAR, but this was not the aim of this study. In addition, no comparison was made with other methods that can be used to estimate LVEF; we are aware of the superiority of DSE in predicting postoperative cardiac adverse events [20], however, in our view, MUGA is an affordable alternative that can just be as useful, hence the preference to use it at our centre.

Acknowledgments

None.

Copyright information

© Société Internationale de Chirurgie 2013