Bypass Grafting with coronary endarterectomy: immediate and long-term results

2002;124(3):553-560.

- Submitted by:Joel Dunning -
*RCS Research Fellow* - Institution:MRI
- Date submitted:8th May 2003

1
Objectives and hypotheses

1.1
Are the objectives of the study clearly stated?

The objective of this paper is to evaluate the early and late outcomes of Coronary Endarterectomy

2
Design

2.1
Is the study design suitable for the objectives?

This is a retrospective, non-consecutive uncontrolled Cohort study

This is adequate for evaluation of the technique although as there are previous cohort studies evaluating this technique, a study with matched controls or even better a PRCT would have been better.

This is adequate for evaluation of the technique although as there are previous cohort studies evaluating this technique, a study with matched controls or even better a PRCT would have been better.

2.2
Who / what was studied?

A retrospective study of 107 patients who underwent coronary revascularisation with coronary endarterectomy between 1989 and 2000 in a single USA institution.

This represented 3.7% of their workload.

This represented 3.7% of their workload.

2.3
Was a control group used if appropriate?

No control group used although it does seem that similar matched controls could have been found from their retrospective database

2.4
Were outcomes defined at the start of the study?

Early and late death.

NYHA score

CCS score

graft patency as measured by angiography

Ejection Fraction measured by Echocardiography

NYHA score

CCS score

graft patency as measured by angiography

Ejection Fraction measured by Echocardiography

2.5
Was this the right sample to answer the objectives?

This was a highly selected sample and no explanation of how patients were selected is given other than "consultant preference"

2.6
Is the study large enough to achieve its objectives? Have sample size estimates been performed?

This was a convenience sample. No power calculations performed

2.7
Were all subjects accounted for?

Yes. There were 5 in hospital deaths and 5 late deaths.

97.5% received complete follow up with angiography and Echocardiography

97.5% received complete follow up with angiography and Echocardiography

2.8
Were all appropriate outcomes considered?

Yes

2.9
Has ethical approval been obtained if appropriate?

Not appropriate

3
Measurement and observation

3.1
Is it clear what was measured, how it was measured and what the outcomes were?

Key outcomes :

Graft patency on angiography (mean 30mths after operation):

Grafts receiving endarterectomy - 72% +/- 11%

Grafts receiving conventional bypass - 73% +/-12%

Pre-op MeanEjection Fraction 49% +/- 8.8%

Post-op mean Ejection Fraction 56% +/-14.1%

Multivariate analysis of factors that predict mortality

Unstable Angina, Mitral valve replacement, and Ventricular fibrillation

Multivariate analysis of factors that predict post operative MI

Aortic Valve replacement

Graft patency on angiography (mean 30mths after operation):

Grafts receiving endarterectomy - 72% +/- 11%

Grafts receiving conventional bypass - 73% +/-12%

Pre-op MeanEjection Fraction 49% +/- 8.8%

Post-op mean Ejection Fraction 56% +/-14.1%

Multivariate analysis of factors that predict mortality

Unstable Angina, Mitral valve replacement, and Ventricular fibrillation

Multivariate analysis of factors that predict post operative MI

Aortic Valve replacement

3.2
Was the assessment of outcomes blinded?

No

3.3
Was follow up sufficiently long and complete?

Follow up period was 38 months with a range of 1 to 124 months

3.4
Are the measurements valid?

All measurement outcomes are valid

Angiography is gold standard for graft patency

Ejection fraction is valid

NYHA and CCS scores are well validated

Angiography is gold standard for graft patency

Ejection fraction is valid

NYHA and CCS scores are well validated

3.5
Are the measurements reliable?

Angiography is highly reliable

Ejection fraction as measured by 2-D Echocardiography is not a test that can reliably measure to the accuracy of 1% , so the pre and post operative ejection fraction results should be read with caution

NYHA and CCS scores are subjective scores and subject to bias when the operating surgeon asks the patient if their symptoms have improved postoperatively

Ejection fraction as measured by 2-D Echocardiography is not a test that can reliably measure to the accuracy of 1% , so the pre and post operative ejection fraction results should be read with caution

NYHA and CCS scores are subjective scores and subject to bias when the operating surgeon asks the patient if their symptoms have improved postoperatively

3.6
Are the measurements reproducible?

EF and angiography are reproducible

NYHA and CCS scores are reproducible but may have a different score if an independent reviewer had asked the questions

NYHA and CCS scores are reproducible but may have a different score if an independent reviewer had asked the questions

4
Presentation of results

4.1
Are the basic data adequately described?

Yes. 6 tables of results presented

4.2
Are the results presented clearly, objectively and in sufficient detail to enable readers to make their own judgement?

There is a prolific set of tables with every possible combination of results presented.

Of note Table 6 is a table describing the multivariate analysis of post-operative MI. The table takes up a full page out of a 6 page article and every single variable is presented as to how many people have the variable and a late MI and how many had the variable and did not have an MI.

Now comes the punch-line ! Out of 107 patients, ONLY 2 PATIENTS HAD AN MI ! This table is a complete waste of time and space and the multivariate analysis with only 2 positive cases is a severe mis-use of this statistical technique.

Of note Table 6 is a table describing the multivariate analysis of post-operative MI. The table takes up a full page out of a 6 page article and every single variable is presented as to how many people have the variable and a late MI and how many had the variable and did not have an MI.

Now comes the punch-line ! Out of 107 patients, ONLY 2 PATIENTS HAD AN MI ! This table is a complete waste of time and space and the multivariate analysis with only 2 positive cases is a severe mis-use of this statistical technique.

4.3
How large are the effects within a specified time?

The most interesting result presented in this paper is the fact that the non-endarterectomised vessels have exactly the same patency as non endarterectomised vessels that were also done on the same patients.

The difference in Ejection Fraction is very small.

The difference in Ejection Fraction is very small.

4.4
Are the results internally consistent, i.e. do the numbers add up properly?

NO.

In table 1, presenting the findings of all variables in the 107 patients, all variables add up except the NYHA score which adds up to 102 ! The culprit statistic seems to be the number given for NYHA grade IV, which is given as 14 but then they state that this is 15% of the 107 patients (i.e. 14/107 x 100)

In table 1, presenting the findings of all variables in the 107 patients, all variables add up except the NYHA score which adds up to 102 ! The culprit statistic seems to be the number given for NYHA grade IV, which is given as 14 but then they state that this is 15% of the 107 patients (i.e. 14/107 x 100)

5
Analysis

5.1
Are the data suitable for analysis?

The simple data is suitable for analysis, but the data is not suitable for multivariate analysis.

5.2
Are the methods appropriate to the data?

Multivariate analysis was performed on late mortality and postoperative MI

There were only 5 late deaths and 2 postoperative MI's out of the database of 107 patients and attempts to perform this type of analysis with so few positives demonstrates a lack of understanding of the technique.

There were only 5 late deaths and 2 postoperative MI's out of the database of 107 patients and attempts to perform this type of analysis with so few positives demonstrates a lack of understanding of the technique.

5.3
Are any statistics correctly performed and interpreted?

The statistics are not amenable to checking on the whole, but in the Statistical Analysis section they describe that an "impaired 2-tailed t-test" was performed. This is a typographical error and should clearly read "unpaired 2-tailed t-test".

6
Discussion

6.1
Are the results discussed in relation to existing knowledge on the subject and study objectives?

They report a study by Brenowitz et al that reported a 30-day mortality of 6.3% with coronary endarterectomy.

They also report that Livesay et al reported a mortality of 4.4% in a cohort of 3369 patients

These are the only significant references discussed

They also report that Livesay et al reported a mortality of 4.4% in a cohort of 3369 patients

These are the only significant references discussed

6.2
Is the discussion biased?

No, fair discussion

7
Interpretation

7.1
Are the author's conclusions justified by the data?

None of the multivariate analysis data should be considered useful.

The conclusion that Coronary Endarterectomy is a safe procedure with good long term results is justified

The conclusion that Coronary Endarterectomy is a safe procedure with good long term results is justified

7.2
What level of evidence has this paper presented? (using CEBM levels)

4

7.3
Does this paper help me to answer my problem?

The angiographic results are the most persuasive and demonstrate that endarterectomised vessels have the same long term patency as non endarterectomised vessels.They also report an acceptable mortality and post operative MI rate. This is a useful finding

8
Implementation

8.1
Can any necessary change be implemented in practice?

When necessary, endarterectomy should be used

8.2
What aids to implementation exist?

N/A

8.3
What barriers to implementation exist?

The experience with this uncommon technique may be a barrier to recently qualified surgeons.

8.4
Are the study patients similar to your own?

These are a highly selected cohort of american patients from a single institution. Other demographics seem similar to UK patients

8.5
Does the paper give any conclusions that will affect what you will offer or tell your patient?

This paper gives excellent data on graft patency in the longer term for vessels requiring this technique