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Table of Contents
ORIGINAL ARTICLE
Year : 2022  |  Volume : 27  |  Issue : 2  |  Page : 131-136

Pre-operative lipid profile of cardiac surgery patients: Implications of incidental findings


1 Department of Medicine, University of Nigeria Teaching Hospital, Ituku/Ozalla, Enugu, Nigeria
2 Department of Chemical Pathology, University of Nigeria Teaching Hospital/College of Medicine, University of Nigeria, Ituku/Ozalla Campus, Enugu, Nigeria

Date of Submission04-Nov-2021
Date of Decision24-Jan-2022
Date of Acceptance30-Jan-2022
Date of Web Publication3-Mar-2022

Correspondence Address:
Ijeoma A Meka
Department of Chemical Pathology, University of Nigeria Teaching Hospital/College of Medicine, University of Nigeria, Ituku/Ozalla Campus, Enugu.
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijmh.IJMH_43_21

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  Abstract 

Background: Dyslipidemia is an established risk factor for cardiovascular disease (CVD). Different schools of thought hold different opinions regarding the use of statins in the perioperative period for cardiac surgery patients. There seems not to be a consensus yet on when to commence statin therapy for cardiac surgery patients not yet on treatment for dyslipidemia, but the beneficial effects of dyslipidemia management are not in doubt. Objectives: The objective was to characterize the pattern of dyslipidemia and atherogenic indices present in cardiac surgery patients. Materials and Methods: The study was a retrospective record review of patients who presented for open heart surgery between 2013 and 2017. Results of pre-operative lipid profile of patients were extracted and analyzed using SPSS version 22. Atherogenic risk was determined using three different risk ratios: atherogenic plasma index and Castelli’s risk indices-I and II. Results: The study included a total of 51 adult patients with the age range 18–75 years and male: female ratio of 1:1.4. Dyslipidemia observed in participants was majorly in the form of low high-density lipoprotein 24 (49.0%) and elevated low-density lipoprotein 11 (22.5%). Using atherogenic plasma index, more than one-quarter of participants 15 (30.6%) were found to be in the high- and medium-risk groups. Conclusion: Incidental findings of dyslipidemia made in this group of patients have its associated health implications. Hence, it buttresses the importance of assessing for and adequate management of the medical condition, particularly in a group of patients already burdened with CVD.

Keywords: Atherogenic plasma index, cardiac surgery, dyslipidemia, LDL/HDL ratio, TC/HDL ratio


How to cite this article:
Njoku PO, Meka IA, Mbadiwe N. Pre-operative lipid profile of cardiac surgery patients: Implications of incidental findings. Int J Med Health Dev 2022;27:131-6

How to cite this URL:
Njoku PO, Meka IA, Mbadiwe N. Pre-operative lipid profile of cardiac surgery patients: Implications of incidental findings. Int J Med Health Dev [serial online] 2022 [cited 2022 May 24];27:131-6. Available from: https://www.ijmhdev.com/text.asp?2022/27/2/131/339032




  Introduction Top


Dyslipidemia is an established risk factor for cardiovascular disease (CVD) and refers to elevated total cholesterol, low-density lipoprotein-cholesterol (LDL-C), triglyceride, or low levels of high-density lipoprotein-cholesterol (HDL-C).[1] Blood levels of LDL-C have been documented to significantly predict incident atherosclerotic CVD.[2] Hence, the traditional lipid components of lipid profile had been used as cardiovascular risk indices and the targets of therapy. However, in an attempt to optimize the predictive capacities of these lipid components, lipoprotein ratios and atherogenic indices were developed.

Although alterations in the lipid components of an individual’s lipid profile can predispose one to atherosclerosis, the atherogenic index of plasma (AIP) has been identified as a critical index that can be used as a standalone index for cardiac risk estimation.[3] It is hence adjudged to be more useful than individual lipid profile parameters as it is said to predict risk of atherosclerosis even when routine lipid parameters are within their optimal limits.

AIP, which is defined as logarithm of the ratio of plasma concentration of TG to HDL-C, has been documented to possess a significant correlation with CVD risk factors.[4]

Other clinically useful lipid ratios include Castelli’s risk index-1 (TC/HDL-C), Castelli’s risk index-II (LDL-C/HDL-C), and atherogenic coefficient (TC-HDL-C/HDL-C). These lipid indices have been demonstrated to be strong indicators of the CVD risk by their expressions of imbalance between atherogenic and antiatherogenic lipoproteins.[5],[6] AIP was however adjudged to be the most sensitive marker when compared with the other three.[7],[8]

Currently, there is no consensus as to which index is superior between the two Castelli’s risk indices, although a study[5] on ischemic heart disease risk has documented that variation in the TC/HDL-C ratio may be associated with more substantial alterations in metabolic indices predictive of ischemic heart disease risk and related to the insulin resistance syndrome than variation in the LDL-C/HDL-C ratio.

The prevalence of dyslipidemia varies widely globally and has been widely studied among patients with varying pathologies. It is worthy of note, however, that most of these studies have been centered on obesity, hypertension, diabetes mellitus, and apparently healthy individuals with data lacking among cardiac surgery patients.

In Nigeria, the pooled crude prevalence of hypercholesterolemia in Nigeria was reported to be 38%.[9] Dyslipidemia among diabetic patients has been recorded to be 69.3%,[10] 70%,[11] 89.0%,[12] and 90.7%[13] at different periods and among different regions in Nigeria, whereas the prevalence among hypertensive patients has been recorded to be 44%,[14] 44.3%,[15] 58.9%,[16] and 60%,[17] according to different researchers.

It is important to note the positions of different schools of thought concerning the perioperative effect of statin use in patients undergoing surgery. In 2002, a clinical advisory[18] recommended temporarily discontinuing statins in the perioperative periods due to their opinion of increased risk of statin-associated myopathy. However, in 2007, the American College of Cardiology and American Heart Association[19] began recommending uninterrupted use of statins around the time of non-cardiac surgery, noting its protective effect on cardiac complications. In 2008, Williams and Harken[20] in their review of studies evaluating outcomes of statin treatment in surgical series concluded that statins are protective in the preoperative period and must not be discontinued in surgical patients. In the work by Putzu et al.,[21] they reported that analyses of different randomized clinical trials showed no evidence that statin therapy in the days prior to cardiac surgery is beneficial for patients’ outcomes. In contrast, Collard et al.[22] reported that preoperative statin use was associated with better survival, whereas discontinuation of statin treatment after surgery was independently linked to an increased all-cause and cardiac mortality at 30 days.

There, however, seems not to be a consensus yet on when to commence statin therapy for cardiac surgery patients not yet on treatment for dyslipidemia, but the beneficial effects of dyslipidemia management are not in doubt. From the foregoing, it becomes clear that patients undergoing cardiac surgery ought to be properly evaluated and those found to have dyslipidemia should be well categorized, hence the purpose of this study.


  Materials and Methods Top


Study location

The study was carried out at the National Cardiothoracic Center for Excellence, University of Nigeria Teaching Hospital (UNTH), Enugu, Nigeria. This health institution is located in South-East Nigeria and is one of the foremost teaching Hospitals in Nigeria. It is a 500-bed capacity health institution which serves Enugu State and other South-East, North-Central, and South-South states.

Study design

The study employed a retrospective hospital-based study design. A record review of patients’ folders who presented for open heart surgery was carried out. Consenting adult patients with a diagnosis of valvular heart disease and shunts was included in the study. Relevant demographic data and results of baseline preoperative lipid profiles of patients were extracted from individual patient’s folders, cleaned, and analyzed.

Ethical consideration

Ethical clearance was obtained from the University of Nigeria Teaching Hospital Health Research Ethics Committee after research protocol review and approval.

Interpretation of data

Atherogenic index was calculated using the formula: log10(TG/HDL-C) and classified as follows: −0.3 to 0.1 for low risk, 0.1–0.24 for medium, and more than 0.24 for high risk of CVD.[23]

Castelli’s risk index-I was calculated as TC/HDL-C, and values greater than 5 were regarded as the risk level for primary prevention. Castelli’s risk index-II was calculated as LDL-C/HDL-C and values greater than 3.5 were regarded as the risk level for primary prevention.[6]

Optimal values of total cholesterol, LDL-C, and triglyceride were defined as <5.2 mmol/L; <3.4 mmol/L; and <1.7 mmol/L, respectively that of HDL-C were >1.0 mmol/L for men and >1.3 mmol/L for women.[24]

Statistical analysis

Data were input into a Microsoft Excel sheet and double-checked for errors. The analysis was done using Statistical Package for Social Sciences (SPSS) version 22. Categorical data were summarized using frequencies and percentages, whereas continuous variables were summarized as mean, standard deviation, numbers, and percentages. Pearson’s correlation was used to determine correlation between API, TC/HDL-C, and LDL-C/HDL-C. The level of significance was put at 0.05.


  Results Top


The study included a total of 49 adult patients. The mean (SD) age was 43.4 (15.1) years, age range 19–75 years, and male: female ratio 1:1.3. The majority [34 (69.4%)] of the participants had secondary education as their highest attained formal education. The participants’ sociodemographic characteristics are as described in [Table 1]. The distribution of the cardiac disorders among the participants is as shown in [Figure 1] with cardiac valvular disorders being the commonest 42 (85.7%). The lipid profile parameters collected were TC, LDL, HDL, and TG. Dyslipidemia observed in participants was majorly in the form of low HDL 24 (49.0%) and elevated LDL 11 (22.5%). Using API, more than one-quarter of the participants [15 (30.6%)] were found to be in the high- and medium-risk groups, whereas 11 (22.5%) and 16 (32.7%) of the participants had HDL/LDL and TC/HDL ratios above the target level for primary prevention [Table 2]. API was more strongly correlated with the TC/HDL-C ratio than with the LDL-C/HDL-C ratio [Figure 2] and [Figure 3].
Table 1: Sociodemographic characteristics of participants

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Figure 1: Distribution of cardiac disorders among participants

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Table 2: Distribution of lipid parameters and indices among participants, n = 49

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Figure 2: Correlation of API and LDL/HDL, r = 0.5488, P = 0.000044

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Figure 3: Correlation between API and TC/HDL, r = 0.6561, P < 0.00001

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  Discussion Top


Although atherosclerosis is a complex and multifactorial process, dyslipidemia has been established as one of the key contributory factors. Among patients already burdened with cardiac diseases and undergoing a surgical procedure, the finding of dyslipidemia is one which should not be taken lightly. In the present study, almost a quarter of the patients had LDL-C above the optimal limit, and more than a quarter had their API in the high- and medium-risk categories. API has been documented to be a sensitive marker for atherosclerosis risk, and atherosclerosis is the dominant cause of CVD. Fortunately, dyslipidemia is a modifiable cardiovascular risk factor; hence, its identification and treatment are highly desirable in this group of patients, to avoid a double burden of undergoing cardiac surgery and then coming down with other atherosclerosis-induced CVDs in future.

The most frequent lipoprotein disorder found in this study was low HDL-C. HDL-C is regarded as the cardioprotective lipoprotein. The Framingham study showed a strong, graded, independent, inverse relationship between HDL-C and both CVD and total mortality.[25] Hence, HDL-C is one of the risk parameters used in tools commonly used to assess cardiovascular risk, such as the Framingham Risk Scores and the Heart Score tools. Various foods, exercise, maintaining a healthy weight, and quitting smoking are some of the ways of elevating HDL-C, which can be harnessed in these patients. Measures targeted at reduction of plasma cholesterol such as therapeutic lifestyle changes are equally encouraged. Therapeutic lifestyle changes which incorporate diet, exercise, and weight management encourage practices such as intake of more fruits and vegetables, calorie restriction, limited intake of saturated fats and alcohol, quitting smoking, and engaging in active exercise.

In the present study, the TC/HDL ratio identified more patients at CVD risk than either TC or LDL-C alone. This agrees with the study by Kinosian et al.,[26] which equally recorded that the TC/HDL ratio is a superior measure of risk for coronary heart disease compared with either TC or LDL-C levels. The ability of this parameter to identify risk even when the lipid profile is within the desirable range ought to be emphasized.[6]

TC/HDL-C equally identified more individuals at risk than the LDL-C/HDL-C ratio in the present study. This is also in agreement with a previous study by Lemieux et al.,[5] which documented that TC/HDL-C may predict ischemic heart disease better than LDL-C/HDL-C. Both TC/HDL-C and LDL-C/HDL-C are very useful predictors of CVD; however, in a situation in which the LDL-C cannot be accurately determined or in individuals with high triglyceride concentrations, TC/HDL-C is preferred as LDL-C/HDL-C may underestimate the magnitude of lipoprotein abnormality present.[6]

The API correlated significantly and positively with both Castelli’s indices equally buttressing the usefulness and importance of both indices as predictors of risk.

Limitations and strength of the study

One major limitation of this study was the inevitable issue of missing data, which invariably reduced the number of participants.

Despite this limitation, its strength lies in it being among the first studies to the best of authors’ knowledge to describe these findings in open heart surgery patients.


  Conclusion Top


Identification of dyslipidemia in this group of patients will enable clinicians to incorporate appropriate management measures targeted at lipid lowering. The use of atherogenic indices rather than individual lipid components equally provides better markers of atherogenic risk and hence offers more sensitive basis for lipid targets aimed at reduction of atherogenic risk in the post-operative and follow-up periods for optimal overall patient outcome.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2]



 

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