You've probably heard somewhere that in winter there is a sudden increase in the number of cardiovascular events like acute myocardial infarction (AMI), but is it really true? If so, what is the pathophysiology behind this situation? This subject has intrigued the scientific community for many years and we will work with these issues throughout our text.

In 1999, the magazine “Nature" published a text by scientist Hannah Wunsch, in which the author compiled a compilation of recent publications at the time that pointed to evidence of the relationship between low temperatures and the increased incidence of cardiovascular events (1).

The literature review, published by Liu, Yavar and Sun, brings a detailed study of articles that evaluated the cardiovascular response to temperature changes. In the study, 99 references were evaluated that demonstrate the increase in cardiovascular events, such as AMI, in periods of low temperature, covering different parts of the world (2). Among the explanations pointed out by the article, there are hypotheses such as: alteration in the activity of the sympathetic system and the renin-angiotensin system; induction of the inflammatory response by changes in ambient temperature; molecular changes; atherosclerotic picture; endothelial dysfunction and adiponectin; pre-existing cardiac injury.

In Brazil, a recent study by Ferreira et al. evaluated six metropolitan regions, in a total of 64 cities, regarding ambient temperature and mortality due to AMI (3). The authors drew a cutoff temperature that, in certain regions of the country, should be considered as a potential risk for AMI in the population, namely: 19.5^OC in Rio de Janeiro, 12.5 ^OC in Porto Alegre, 16.1 ^OC in São Paulo and 20.4 ^OC in Brasilia.

Once it has been demonstrated that there is ample scientific documentation on the correlation between temperature decrease and the propensity for cardiovascular events, we need to understand the pathophysiological process behind this complication. To illustrate the above-mentioned mechanism, we base ourselves on an image published in the work of authors Liu, Yavar and Sun, which briefly but lucidly presents the process by which exposure to cold leads to the aggravation of cardiovascular diseases (2).

Figure 1: Representation of the action of cold in the cardiovascular event

Based on a figure published in the work entitled “Cardiovascular response to thermoregulatory challenges” (2).

In addition to the conditions presented in Figure 1, the work by Claeys et al. addresses the mechanism by which low temperatures lead to instability of the atherosclerotic plaque, which can cause atherothrombosis (4). The development of atherosclerotic plaque is a multifactorial event, with classic risk factors such as dyslipidemia, diabetes, smoking, hypertension and genetic factors (5). The atherosclerotic plaque instability process is illustrated in Figure 2.

Figure 2. Plausible biological mechanism that explains the relationship of cold with the atherothrombotic event.

Adapted from the figure published in the work entitled “Plausible biological mechanisms linking air pollution to atherothrombotic events” (4).

When evaluating the mechanisms in Figures 1 and 2, we can infer that, with regard to the laboratory aspect, some tests can help in the assessment of the population at risk for the development of cardiovascular complications when there is a decrease in ambient temperature.

The laboratory evaluation of parameters such as total cholesterol and fractions, triglycerides, C-reactive protein (CRP) and CKMB can be useful in the evaluation of these patients.

Considering the scientific evidence presented above, we realize that low temperatures can really be a risk factor for people with cardiovascular disease, especially for those with atherosclerosis plaque.

Within this entire context, Biotécnica offers its in vitro diagnostic reagents with the quality that is the company's trademark, offering highly qualified scientific advice to help our customers face the challenges of laboratory routine.

• Cholesterol

The dosage of this lipid is associated with the risk of developing cardiovascular diseases and the Brazilian Society of Cardiology (SBC), through the Update of the Brazilian Guideline on Dyslipidemia and Prevention of Atherosclerosis, published in 2017, indicates that the desirable value of cholesterol is lower than 190mg/dL (6).

Biotécnica makes the kit available in two presentations:
1 x 250 mL and 4 x 250 mL

Both have the standard included and an operating range up to 800 mg/dL, reducing the need for sample dilution and the consequent interference of this process in the cholesterol dosage.

• HDL-Cholesterol:

HDL-cholesterol (from English, high-density lipoprotein) is known to be the “good cholesterol”. That's because one of the functions it plays in metabolism is to remove cholesterol from the blood and carry it to the liver for use or excretion. According to the same SBC document, the desired HDL-cholesterol dosage must be greater than 40mg/dL (6).

Biotécnica offers two HDL-cholesterol dosage options:

Precipitating HDL

Manual method, but still widely used in several laboratories.

Direct HDL

It has 3 presentations (60 mL, 120 mL and 240 mL). Factor that demonstrates Biotécnica's concern to meet the most varied routines.

It is important to note that all presentations contain the Calibrator included. Vital factor for maintaining the accuracy of the test.

Pay attention to kits that do not provide the calibrator or standard, loss of accuracy can impair the quality of your results.

• LDL-Cholesterol

LDL-cholesterol (from English, Low-density lipoprotein) is known as the “bad cholesterol”, as it has an opposite role to that of HDL-cholesterol, carrying fat into the bloodstream and favoring the appearance of atherosclerotic plaque. The SBD classifies LDL-Cholesterol dosages according to risk category, as follows: < 130, low; < 100, intermediate; < 70 high and < 50 very high(6). A detail about cholesterol is that it can be estimated by the Friedwald formula, but this formula should not be used when the values of triglycerides are greater than 400 mg/dL.

However, we have a kit available for direct LDL-cholesterol dosage which provides a more assertive assessment of the levels of this lipoprotein in the patient's sample. With calibrator included and available in 40 mL presentation.

• Triglycerides:

Triglycerides are the main fat in our body and the increase in their concentration in the body is directly related to atherosclerotic plaque. As it is an analyte that varies according to fasting, the desirable values, according to the SBD, are 150mg/dL for fasting patients and 175mg/dL for non-fasting patients (3).

Biotécnica makes the kit available in three presentations:
5 x 50 ml, 5 x 100 ml and 10 x 100 ml

The fractional presentation is important, as it is a reagent that is very sensitive to contamination, if it occurs, it will not affect the total volume of the kit. Providing a good cost-benefit ratio.

Both have the standard included and an operating range up to 800 mg/dL, reducing the need for sample dilution and the consequent interference of this process in the cholesterol dosage.

• C-Reactive Protein (CRP):

Non-specific markers of inflammation may have an important predictive value in assessing the risk of cardiovascular diseases (8). Among the various possible methods for evaluating CRP, ultrasensitive evaluation, as the name suggests, can determine small concentrations of this analyte, helping to monitor patients who present a condition that may progress to cardiovascular complications.

BioTécnica offers three kits for PCR evaluation:

Latex PCR

Manual plate agglutination methodology. Possibility of kit with controls (+) and (-) or just latex.

Widely used for screening patients who, when positive, can be quantified using the turbidimetric kit.

Turbulent PCR

Turbidimetric methodology for analyte quantification. More accurate and agile method, as it can be automated in various equipment on the market.

The Biotécnica kit is marketed in a 50 mL presentation and with included calibrator.

Ultra Sensitive PCR

Able to detect small concentrations of this protein in the patient sample, which can have great diagnostic value as mentioned.

The Biotécnica kit is sold in a 50 mL presentation, with calibrator and control included.

• Rheumatoid Factor:

In winter, patients with rheumatic diseases may have worsening pain and the dosage of rheumatoid factor may help in monitoring and diagnosing this inflammatory disease.

Biotécnica provides two methods for evaluating the rheumatoid factor:

FR latex

Manual plate agglutination methodology. Possibility of kit with controls (+) and (-) or just latex.

Widely used for screening patients who, when positive, can be quantified using the turbidimetric kit.

Turbidimetric methodology for analyte quantification. More accurate and agile method, as it can be automated in various equipment on the market.

The Biotécnica kit is marketed in a 50 mL presentation and with included calibrator.

• CKMB:

The measurement of CKMB is vitally important for evaluating AMI, as it is an enzyme with specificity for myocardial cells and its sensitivity depends on the extent of the cardiac lesion, as well as on the time elapsed from the cardiac event.

BioTécnica offers reagent for CKMB dosage in two presentations, both with control included, and operating range from 7.16U/L to 600U/L.

References

1. Wunsch H. Temperature, pressure and heart attacks. Nature. 1999.
2. Liu C, Yavar Z, Sun Q. Cardiovascular response to thermoregulatory challenges. American journal of physiology Heart and circulatory physiology. 2015;309(11):H1793-812.
3. Ferreira LCM, Nogueira MC, Pereira RVB, de Farias WCM, Rodrigues MMS, Teixeira MTB, et al. Ambient temperature and mortality due to acute myocardial infarction in Brazil: an ecological study of time-series analyses. Scientific reports. 2019;9(1):13790.
4. Claeys MJ, Rajagopalan S, Nawrot TS, Brook RD. Climate and environmental triggers of acute myocardial infarction. European heart journal. 2017;38(13):955-60.
5. Bergheanu SC, Bodde MC, Jukema JW. Pathophysiology and treatment of atherosclerosis : Current view and future perspective on lipoprotein modification treatment. Netherlands heart journal : monthly journal of the Netherlands Society of Cardiology and the Netherlands Heart Foundation. 2017;25(4):231-42.
6. Faludi AA, Izar MCO, Saraiva JFK, Chakra APM, Bianco HT, Afiune AN, et al. Brazilian Archives of Cardiology. 2017;109(2 Suppl 1):1-76.
7. Martin SS, Blaha MJ, Elshazly MB, Toth PP, Kwitterovich PO, Blumenthal RS, et al. Comparison of a novel method vs the Friedewald equation for estimating low-density lipoprotein cholesterol levels from the standard lipid profile. Jama. 2013;310(19):2061-8.
8. Pearson TA, Mensah GA, Alexander RW, Anderson JL, Cannon RO, 3rd, Criqui M, et al. Markers of inflammation and cardiovascular disease: application to clinical and public health practice: A statement for healthcare professionals from the Centers for Disease Control and Prevention and the American Heart Association. Circulation. 2003;107(3):499-511.
9. School HM. Avoiding winter heart attacks 2016. Available from: https://www.health.harvard.edu/heart-health/avoiding-winter-heart-attacks.