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Sumario Vol. 42 - Nº 1 Enero - Marzo 2013

Multislice tomography characterization of coronary plaques in diabetic patients with acute coronary syndrome.

Claudio Pereyra Sueldo *, Mariano Rubio”, Claudio Ledesma, Luciana Moriconi, Lucas Corradi, Roberto Colque°.

Clínica Privada Vélez Sarsfield, Córdoba, Argentina.
Servicios de Cardiología Intervencionista, Tomografía Multicortes de 64 detectores y Ecocardiografía Doppler
E Mail

Recibido 07-SET-2012 – ACEPTADO después de revisión el 09-Enero de 2013.

The authors declare not having a conflict of interest.


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SUMMARY

Atherothrombotic  disease is a systemic condition with local manifestations. One of the main reasons for consultation and hospitalization is ischemic heart disease, including acute coronary syndromes. Traditional risk factors, diabetes, hypertension and dyslipidemia play a key role in the development and progression of atherosclerotic plaques, without knowing precisely the role of emerging risk factors
The objective of this study is to assess the impact of diabetes on the composition and arrangement of atherosclerotic plaques in coronary arteries
Material and Methods: Between November 2008and February 2010, we analyzed 114 patients with symptoms consistent with an acute coronary syndrome, stratified as intermediate risk, who underwent a coronary multislice 64-detector computed tomography study. According to the presence or absence of diabetes, associated with other risk factors, patients were located in 2 groups. The analysis of the results considered the composition of the plaques.
Results: 61% of the study population had diabetes (group I) as a risk factor, the remaining 39% joined the group of non diabetic subjects (group II). Fibrolipid plaques, in each of the coronary arteries, were more prevalent (>63%) in group I-DBT; in contrast to a prevalence of no more than 39%in non-DBT group II.
Conclusions: Most fibrolipid plaques in the diabetic population could be associated with a different mode of progression of these plaques and also morphologically distinct clinical presentation than in patients without diabetes. Images in cardiology are necessary for the plaque characterization and construction of risk scores in patients with similar clinical syndromes.

Key words: Coronary syndromes. Atherosclerosis. Multislide tomography. Diabetes. Atherosclerotic plaque.
Rev Fed Arg Cardiol. 2013; 42(1): 43-48

 

 

INTRODUCTION
Since the discovery of the atherothrombotic nature of coronary artery disease (CAD), the advancement of cardiology has been focused on the diagnosis and treatment of myocardial infarction. Since Mason Sones [1] with the addition of coronary angiography to the diagnosis and evaluation of coronary obstructions, there were significant advancements, among them the aortocoronary bypass surgery, developed at the Cleveland Clinic by Dr. Rene Favaloro stands out, as well as percutaneous coronary angioplasty [2], presently used systematically and as a routine in most of care centers.

The traditional risk factors are widely known, and those emerging as generators and facilitating the progression of atheromatous plaques are being added, though yet with their contribution in the composition and distribution of the atherothrombotic plaques to be investigated, to optimize the treatment of this pathology [3].

Plaque accidents [4], with overlapping thrombosis, contribute to the progression and growth of the plaque, with a wide spectrum of clinical presentation.

The sustained advancement of imaging in cardiology, since the conventional invasive coronary angiography, to the images contributed today in a non-invasive way by multislice tomography and nuclear magnetic resonance, is striking [5,6,7] and significant; however, the contribution of the images obtained in an invasive fashion by the use of vascular ultrasound or coronary angioscopy should be highlighted too, since these techniques allowed the advancement in the interpretation and in the pathophysiological knowledge of coronary atherosclerotic plaques [8,9].

Multislice tomography or coronary tomography with the use of multidetectors, started to have a practical usefulness in the evaluation of the coronary pathology since the use of 32 detectors, with tomography of 64 detectors being the one most widely used because of its usefulness according to the quality of the images. This method validated internationally has extended its implementation for the evaluation of “stable” patients and in those patients that being symptomatic may belong to one category of intermediary risk [4,5,6], or a group of major risk, particularly for the contribution of the morphological description of the atheromatous plaque [9].

The possibility that from imaging, clinical events may be predicted [10] is a historical challenge in full force in current cardiology, a search that includes methods such as intravascular echo, tomography by optical coherence and intravascular magnetic resonance [11,12,13].

The objective of this study was evaluating the participation of diabetes, considered an independent risk factor, in the composition, distribution and severity of arteriosclerotic plaques, in a cohort of patients evaluated through coronary tomography by multidetectors, who consulted by coronary symptoms interpreted in triage as being in intermediary risk.

 

MATERIAL AND METHODS
A retrospective analysis of data collected from the clinical history of patients evaluated with multislice tomography of 64 detectors (Toshiba Aquilion) in patients that consulted due to symptoms compatible with acute coronary syndrome in intermediary risk.

The tomographic studies of 158 patients with diagnostic suspicion of CAD, were analyzed consecutively in the period from November 1, 2008, to February 28, 2010.

There were 44 patients excluded from the present analysis, due to known or possible allergy to iodine, by the choice of the patient, the impossibility of using beta blockers (IV propranolol, 5 mg=5 ml) or by unspecified causes; from this 114 patients were included in the present study.

In their clinical history, emphasis was made on the presence or not of the traditional risk factors stated in the clinical history, particularly diabetes, to estimate its prevalence in the population studied. The type of diabetes and the modality of management (oral, insulin, or mixed) although requested, are not stated in the present analysis.

The studies were made with non-ionic contrast, with fasting of at least 4 hours and the administration of IV propranolol, in those patients that required it with the aim of reaching a heart rate below 70 bpm, with the ideal target being 60 +/- 5 beats per minute. Besides, the patients received sublingual isosorbide dinitrate, a usual practice to rule out vasoconstriction with the resulting coronary spasm, a phenomenon that may generate confusing images.
Two independent observers analyzed the coronary segments of the 3 main coronary arteries.

Figure 1. These arteries were scanned in a synchronized way with the electrocardiogram, obtaining correlative images with volumetric reconstructions. The calcium score was obtained from a slice thickness of 0.5 mm. The slices made were of 0.5 mm, characterizing the plaques according to their predominant fibrolipid content and calcium score (Agatston score). Plaques are considered significant when they reduced lumen in a ratio ≥60%. There were 72+/-6 coronary slices evaluated per patient.

Figure 1. Plane curve of analysis of coronary arteries.


According to the presence or not of diabetes, along with 2 other traditional risk factors (hypertension and dyslipidemia) the patients were grouped in 2 sets for the analysis of tomographic images.
Group I:Diabetic, hypertensive and dyslipidemic patients.
Group II: Non-diabetic, hypertensive and dyslipidemic patients.

 

RESULTS
From all the 114 patients analyzed, 70 patients (61%) made up group I of diabetic patients, most were also hypertensive, while 44 (39%) made up group II of non-diabetic patients, although also hypertensive. Figure 2.

Figure 2. Distribution by gender of all the analyzed patients.


The population included in the present analysis had in average 64.4 years, 73% were men and 27% women. Figure 3.

Figure 3. Ratio between diabetic and hypertensive patients.

From all non-diabetic patients included in group II, 39% presented fibrolipid (FL) plaques, from which: 85% were located in the territory of the Anterior Descending artery (ADA), and from them 48% were categorized as significant plaques (lumen <60%). Fourteen per cent of the FL plaques were located in the Right Coronary artery (RCA), and 45% were considered as significant plaques. Figure 4.

Figure 4.Distribution, composition and severity of the plaques in non-diabetic, hypertensive patients.

From the total of diabetic patients included in group I, 63% presented FL plaques in the ADA, from which 35% were considered as significant. In the Circumflex artery (Cx), in 64% FL plaques were found, from which 64% were considered significant, and finally in the RCA 70.6% had FL plaques but just 42% were categorized as significant. Figure 5.

Figure 5. Distribution, composition and severity of the plaques in diabetic and hypertensive patients.

 

DISCUSSION
The description of the coronary plaques, without defining their association with some clinical syndrome, has been ongoing for many years. Currently, important advancements were achieved in this field with the contribution of the noninvasive images that allow evaluating the wall of the artery with more accuracy [1].

Most coronary syndromes occur due to the activity of the so-called “vulnerable plaques” [6-10,14,17], which frequently present a significant fibrolipid core [18], the rationale for the use of statins [19,20], and a thin fibrous layer [21], an ideal combination that strengthens the risk of erosion and rupture of plaques and overlapped thrombotic complication.

The progressive growth of the plaque with lumen reduction of the vessel is accompanied by an underlying inflammatory state, from which smooth muscle cells, collagen, macrophages and lymphocytes participate [20].

The knowledge of the distribution and composition of the plaques could help to determine their predisposition to grow or their vulnerability to rupture. Today, multislice tomography with 64 detectors is the method of choice to provide useful information to identify and characterize the composition of the plaques and by this to attempt to predict their evolution [21-25].

In the patients in “intermediary risk”, the population that is the object of the present study, the way to follow poses major difficulties when making choices, unlike what happens with the patients in low and high risk, better characterized.

The retrospective analysis of the tomography studies of patients evaluated in a scenario of a coronary syndrome showed that diabetic patients (group I) presented a greater proportion of fibrolipid (FL) plaques in the three coronary arteries, although the severity of these FL plaques showed to be significantly lower. It is known that the vulnerable plaques are not necessarily significant (>60% of lumen reduction in the vessel) but they are predominantly fibrolipid. Figure 6.

Figure 6. Analysis of a fibrolipid plaque by multislice tomography (blue: fibrotic; red: lipid; yellow: calcium).

It is considered that the analysis of the plaques, their characterization and composition, with multislice tomography of 64 detectors will allow evaluating more appropriately the evolution of coronary arteriosclerosis.

There are no multicenter studies, although there are large cohorts analyzed, about the treatment that we should approach more specifically [25].

The input of new imaging methods emerging from the technological development will help to define the imagesconceptually [25]. A good example of this is the contribution of nuclear magnetic resonance, the tomography by optical coherence and angioscopy, although some of these techniques are invasive. The new techniques try to overcome the limits of the currently available technology; while this does not imply the usual implementation of an advanced technology as a screening or follow-up method.

Calcium score has been added in many of the algorithms for the risk stratification of coronary patients. The greatest concentration of calcium is associated to a greater probability of obstructive coronary disease; on the contrary, the absence of calcium is associated to a very low probability of having obstructive coronary disease [6,8].

The real usefulness of multislice tomography with 64 detectors, which is only available in a few centers in our area, has been quite discussed in recent years in temrs of the risk stratification of patients with acute coronary syndrome evaluated in chest pain units. An important topic of debate is the degree of exposition of the patients to radiation, a quite significant factor to take into account since an important proportion of imaging techniques use radiations [26].

The advancement in the pathophysiological knowledge on atherothrombosis will probably contribute valuable elements for a proper interpretation of the growth of the plaques [27], to guide the therapeutic management according to the composition of the atheroma plaques, to know the mechanisms that trigger a clinical event, to inactivate the vulnerable plaques, with the goal of achieving the regression of plaques by efficient therapeutic interventions.

Given the complexity and multiplicity of techniques available, the cardiologist should choose the method and time to use it, and in this context when to indicate a multislice tomography with 64 detectors and what information to request from this technique.

Limitations
In this analysis, the previous antiaggregation and glucose-lowering treatments the patients were receiving, were not considered in this analysis, because they were not stated in all the cases.

The electrocardiographic recordings were not available to correlate the type of plaque with the present electrocardiographic changes.

This study did not include in this stage, the follow-up of patients to know their clinical evolution, which is the cause for a future analysis.

 

CONCLUSIONS
Ischemic heart disease is a biological, dynamic process, with the active participation of the different risk factors. Diabetes is an inflammatory, systemic, multiorgan disease with diffuse vascular involvement, which involves the coronary artery tree in a significant manner.

In the present analysis, the coronary arteries were involved in many sectors. Fibrolipid plaques were more prevalent in diabetic subjects, more vulnerable, but with less significant involvement of the vessel lumen (<60%). The calcium score showed a great variability in diabetic patients (datum not included in this analysis), although the more calcified plaques, which caused severe obstructions, were found more frequently in non-diabetic patients.

New studies will be necessary with the contribution of the images to evaluate properly the plaques with a proper characterization of them and the patients carriers of these plaques, to adjust and optimize the therapeutic management of the finding of the images and make them less vulnerable.

 

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