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ORIGINAL ARTICLE Table of Contents  
Ahead of print publication
Prognostic value of dobutamine stress echocardiography in patients with myocardial dysfunction undergoing coronary artery bypass grafting


1 Department of Cardiac Surgery, Isfahan University of Medical Sciences, Isfahan, Iran
2 Department of Cardiology, Najafabad Branch, Islamic Azad University, Najafabad, Isfahan, Iran

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  Abstract 


Background: Given the high capability of dobutamine stress echocardiography (DSE) in the actual estimation of the ventricular function and the prediction of the intraoperative or postoperative outcomes of revascularization, especially following coronary artery bypass grafting (CABG), we aimed to assess the relationship between DSE findings and CABG outcomes. Methods: This retrospective case–control study was conducted on forty patients with left ventricular (LV) systolic dysfunction who underwent CABG during an 8-year period. All the patients were assessed with DSE to determine their ventricular functional status. Checklists containing DSE findings based on the latest guideline, demographics, and the outcomes of revascularization were filled out for the participants. Telephone follow-up was done for all the participants after 6 months. The data were analyzed using SPSS, version 16. Results: Resting LV ejection fraction (LVEF) ≤25%, peak DSE LVEF ≤35%, absolute increase in the LVEF (LVEF change) <8%, a minimum resting wall motion score index (WMSI) of 2, a post-DSE WMSI >2.25, a minimum pulmonary artery pressure (PAP) of 30 mmHg, and nonviable myocardium had positive correlations with the short- and long-term complications of CABG. These correlations were statistically significant between a maximum pre-DSE LVEF of 25% and an LVEF change of < 8% and the operating room complications (P < 0.001) and between nonviable myocardium and the complications in the intensive care unit (ICU; P < 0.001). However, our results did not show that the peak DSE LVEF, WMSI, PAP, and nonviable myocardium were the significant predictors of death due to CABG. It appears that only a pre-LVEF of <25% is a significant predictor of death after CABG (P < 0.001). Conclusions: DSE findings were able to predict complications in the operating room and in the ICU, especially in the participants with low LVEFs.

Keywords: Coronary artery bypass grafting, dobutamine stress echocardiography, myocardial dysfunction


How to cite this URL:
Sadeghi MM, Mirdamadi A, Arabi Z, Dardashti AB. Prognostic value of dobutamine stress echocardiography in patients with myocardial dysfunction undergoing coronary artery bypass grafting. Arch Cardiovasc Imaging [Epub ahead of print] [cited 2018 Dec 14]. Available from: http://www.cardiovascimaging.com/preprintarticle.asp?id=243188





  Introduction Top


Left ventricular (LV) dysfunction is the most common adverse consequence of coronary artery disease.[1] In coronary artery disease, LV dysfunction can be the result of permanent ventricular damage or cardiac fibrosis.[2] The term “myocardial hibernation” is mainly referred to impaired long-term ventricular contractions due to chronic ischemia.[3] In such patients, coronary artery bypass grafting (CABG) can repair this defect considerably and reduce the mortality rate by 25%.[4] The assessment of the cardiac components with hibernation can aid in the risk and benefit stratification of CABG in patients with myocardial infarction.[5] Several studies have assessed the relationship between the intraoperative and postoperative outcomes of CABG and baseline characteristics such as demographics, cardiovascular traditional risk factors, underlying cardiac and even noncardiac diseases, and the LV functional state assessed in terms of the LV ejection fraction (LVEF).

In this regard, the most important and applicable factor for the prediction of poor surgical prognoses is an impaired LV function.[6] Therefore, diagnostic tests that assess myocardial viability play a major role in predicting the results of revascularization, especially in patients with LV dysfunction. The high capability of dobutamine stress echocardiography (DSE) in the assessment of the different myocardial segments and, thus, the actual estimation of the ventricular function – especially following CABG – underscores its value in predicting the intraoperative or postoperative outcomes of CABG. Some authors have emphasized that DSE findings influence clinical decision-making in higher-risk patients and lead to a higher number of referrals for coronary angiography and revascularization.[7] In contrast, other investigators have maintained that the available evidence regarding the ability of this procedure to predict postoperative outcomes, particularly the recovery of the ventricular and valvular functions, is insufficient.[8] Accordingly, we conducted the present study to assess the relationship between DSE findings and the early and mid-term outcomes of CABG.


  Methods Top


This retrospective case–control study was conducted on 141 consecutive patients with LV dysfunction (LVEF <40%) who underwent CABG at Sina Hospital, Isfahan, Iran, during an 8-year period from 2005 to 2013. All the patients were assessed with DSE to determine their ventricular functional status.

The exclusion criterion was the unavailability of CABG results in the patients' hospital records and routine follow-ups.

The initial assessment was done on 141 patients, 40 of whom met the inclusion criteria and were finally evaluated. The data were collected using two questionnaires: a questionnaire for assessing DSE findings such as the LVEF before and after the dobutamine infusion (pre- and post-EF), improvement in the EF after the dobutamine infusion (EF changes), the septal thickness, the diastolic function, the LV dimensions, the wall motion abnormalities, and the pulmonary artery pressure (PAP) and a questionnaire for the baseline characteristics and clinical data such as demographics, medical history, cardiovascular risk factors, medications, early (in-hospital) mortality and morbidity, and the results of midterm post-CABG outcomes assessed with telephone follow-ups.

In the assessment of the cardiac function with DSE, the images of 16 myocardial segments were recorded after the sequential infusion of dobutamine at the rates of 5, 10, and 15 μ/kg/min for 3 min each. The findings were analyzed to determine the viability of the segments. In this regard, the term “nonviability” or “fibrosis” referred to the lack of contraction in a segment both before and after the infusion of dobutamine. Even for the akinetic segments with a preserved thickness, the absence of any contraction with the dobutamine infusion was interpreted as nonviability.

Based on the American Society of Echocardiography guideline, the LV is divided into 16 segments and each segment is graded on a scale from 1 to 4: Grade 1 is considered normal, Grade 2 hypokinetic, Grade 3 akinetic, and Grade 4 dyskinetic. The wall motion was analyzed, and the summation of all the scores divided by the number of the segments was defined as the wall motion score index (WMSI). A WMSI >1 was considered an abnormal DSE finding.[9]

Since all the patients were assessed with DSE for myocardial viability and not ischemia, their medication before the study commencement – especially beta-blockers – was not discontinued.

For the statistical analyses, the results were presented as means ± standard deviations for the quantitative variables and were summarized in absolute frequencies and percentages for the categorical variables. The categorical variables were compared using the χ2 test, and the quantitative variables were compared using the t-test or the Mann–Whitney U-test. The correlations were tested with the Pearson's or Spearman's rank-order correlation test. P ≤ 0.05 was considered statistically significant. The SPSS statistical software, version 16.0, for Windows (SPSS Inc., Chicago, IL, USA) was used.


  Results Top


Forty patients, including 36 (90%) men and 4 (10%) women at a mean age of 60.63 ± 9.44 years (range = 39–81 years), were eligible for assessment in the present study. Diabetes was reported in 17 (42.5%) patients, hypertension in 28 (70%), and hyperlipidemia in 22 (55%). Thirty (75%) patients were in the New York Heart Association functional class II. A previous myocardial infarction was reported in 34 (85%) patients and triple coronary vessel disease in 37 (92.5%). Ten (25%) patients were smoker.

Concerning the post-CABG complications in the operating room, in the intensive care unit (ICU), and at 6-month follow-up, 32% of the study population needed hemodynamic support with inotropes, 35% developed ventricular arrhythmias, and 5% were hospitalized or died. Apropos of the intraoperative findings, arrhythmias were reported in 32.5% of the study population and a need for intra-aortic balloon pumps in 10% before surgery and in 15% after surgery. During the ICU stay, 20% of the patients suffered hypotension, 15% bleeding, 35% arrhythmias, and 10% acute tubular necrosis. Five patients underwent reoperation: four for significant bleeding and one for residual ischemia. The mortality rate in the ICU was 5%. At 6-month follow-up, 91% of the entire study population had no significant problems.

The echocardiographic assessment revealed that 40% of the patients had a maximum pre-DSE LVEF of ≤25%, and while 22.5% had a maximum pre-DSE WMSI of 2, 47.5% had a post-DSE WMSI of <2.

As shown in [Table 1], the mean pre-DSE LVEF was ≤25%, the post-DSE LVEF was ≤35%, the absolute improvement in the LVEF with dobutamine was <8% (LVEF change <8%), the post-DSE WMSI was >2.25, and the PAP was ≥30 mmHg. In addition to nonviable myocardium had a positive correlation with the short- and long-term complications of CABG. In the operating room, the pre-DSE LVEF ≤25% and an LVEF improvement <8% with the dobutamine infusion were significantly correlated with the complications (P < 0.001), and nonviable myocardium was correlated with the complications in the ICU and in the operating room (P < 0.001 and P < 0.005, respectively).
Table 1: Association between Echo findings and complications

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[Table 2] depicts the correlations between the echocardiographic data and the complications at 6-month follow-up after CABG.
Table 2: Correlation between echocardiography data with complications during 6-month follow-up after coronary artery bypass grafting

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It appears that only a pre-LVEF of <25% is the significant predictor of death after CABG (P < 0.001).


  Discussion Top


DSE is a valuable method for predicting the prognosis of revascularization not only in high-risk patients with coronary artery disease in need of further interventions but also in low-risk patients, if unnecessary interventions are to be avoided.[10]

The results of the current study showed that the patients with lower LVEFs (≤25%) before DSE developed more complications after revascularization (P < 0.001). There was a linear correlation between an LVEF improvement of <8% with the dobutamine infusion and the operating room complications, which constituted statistical significance (P < 0.001). A lower LVEF was also correlated, albeit nonsignificantly, with the ICU and long-term complications. There was a nonsignificant, but positive, correlation between a lower LVEF and an LVEF improvement of <8% with the dobutamine infusion and the number of deaths in our study, which is close to the results of the studies by Chaudhry et al.[11] and Pagano et al.,[12] who showed a positive, although nonsignificant, correlation between an LVEF below 40% and cardiac deaths.

Our results are almost concordant with the results of the previous studies which reported higher operative and early mortality rates in patients with a low EF and a linear increase in the risk with a drop in the LVEF.[13],[14]

We found that the patients with nonviable myocardium developed more complications after CABG; this finding was, however, statistically significant only in terms of the ICU complications (P < 0.001). The rate of cardiac deaths was also higher in our patients with nonviable myocardium. Williams et al.[15] reported a high rate of cardiac events in their patients with viable myocardium by comparison with those who had nonviable myocardium, and Allman et al.[16] showed a higher cardiac death among their patients with viable myocardium. These findings do not chime in with our results. In contrast, similar results to those in the current study were reported by Afridi et al.,[17] who demonstrated a good postrevascularization outcome in their patients with viable myocardium, and Liao et al.,[18] who showed a lower cardiac death rate in their patients with viable myocardium. Furthermore, Rizzello et al.[19] demonstrated a strong prognostic value for myocardial viability insofar as their patients with more viable myocardium had a better postrevascularization outcome.

In the current study, the patients with a minimum pre-DSE WMSI of 2, a minimum post-DSE WMSI of 2.25, and a WMSI improvement of <0.35 with the dobutamine infusion had higher rates of complications and mortality after revascularization. These findings are consistent with the results of the studies by Knapp et al.,[20] Rizzello et al.,[19] and Bountioukos et al.[21]

According to our study results, the rate of cardiac events such as post-CABG mortality was higher among the patients who had a minimum PAP of 30 mmHg; this correlation, however, failed to reach statistical significance.


  Conclusion Top


In light of the results of the present study, we can conclude that DSE findings can predict post-revascularization complications in the operating room and in the ICU, especially in patients with a low LVEF. In our study population, mortality and short- and long-term complications were related to lower myocardial viability, lower LVEFs, and lower improvements in the cardiac function during DSE (WMSI >2.25 after the dobutamine infusion). Although our sample size was small, it appears that DSE findings can be employed in combination with other clinical predicting factors to predict the early and long-term outcomes of CABG.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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18.
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19.
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Knapp M, Musiał WJ, Lisowska A, Hirnle T. The value of dobutamine stress echocardiography in predicting clinical improvement following coronary artery bypass grafting in patients with left ventricular systolic dysfunction. Cardiol J 2007;14:174-9.  Back to cited text no. 20
    
21.
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Correspondence Address:
Ahmad Mirdamadi,
Department of Cardiology, Najafabad Branch, Islamic Azad University, Najafabad, Isfahan
Iran
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ACVI.ACVI_3_18




 
 
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