Review and classification of diagnostic methods of the cardiovascular system

Vladislav A. Daguf, Maria A. Grebennikova, Anton R. Filonov, Georgiy K. Oflidi, Yulia A. Tretyakova. Review and classification of diagnostic methods of the cardiovascular system. Cardiometry; Issue 24; November 2022; p. 187-191; DOI: 10.18137/cardiome-try.2022.24.187191; Available from: issues/no24-november-2022/review-classification-diagnostic

WHO data show that cardiovascular disease (CVD) is the leading cause of death worldwide and accounts for 45% of all deaths in Europe [1]. Among elderly residents of Moscow, acute myocardial infarction occurred (in history) in 19.5% of cases, arterial hypertension in 78%, and chronic heart failure (CHF) in 31.7% of Muscovites [2]. The trend towards increasing life expectancy increases the relevance of CVD for the health care system and the social sphere. High morbidity and mortality encourage physicians and researchers to look for the most optimal way to diagnose, risk stratify and treat patients with CVD, among which acute coronary syndrome (ACS) and heart failure (HF) are the most problematic. The cause of ACS is the sudden occlusion of a coronary artery by a ruptured atherosclerotic plaque or thrombus, which leads to the development of a typical clinical picture and changes in the electrocardiogram. However, there are patients with a fuzzy clinical picture and the absence of characteristic signs on the ECG, which requires the inclusion of other diagnostic methods. Heart failure develops most often as a CVD complication in the absence of adequate therapy and reduced patient compliance with medical recommendations. Timely treatment of CVD can significantly slow down the development of complications.

The specificity and sensitivity of most diagnostic methods is far from 100%, and in the case of CVD this leads to fatal consequences. At the same time, the diagnostic arsenal of modern medicine has been steadily growing in recent years, which allows us to count on an increase in the frequency of correct diagnosis for all types of cardiovascular pathology. This article discusses the main diagnostic areas relevant for cardiac patients.

ECG

The ECG method was introduced into clinical practice about half a century ago and at first it was used only for diagnosing cardiac arrhythmias. Gradually, the direction developed, and today ECG makes it possible to diagnose any type of cardiac pathology and avoid diagnostic errors [3].

Interpretation of the ECG picture requires good qualifications from doctors of functional diagnostics. The expert must distinguish the true signs of the disease from artifacts. For example, an irregular baseline ECG may resemble atrial fibrillation. An unstable level of electric current, confusion when applying leads, some somatic pathology (Parkinson’s disease, tremor, taking certain drugs, etc.) can lead to distortion of the ECG [6]. Usually, an experienced physician differentiates well between random bursts and a stable clinically determined ECG picture.

The huge need for ECG, not only in clinical, outpatient practice, but also in everyday life, has led to the need to create automatic programs for analyzing and interpreting ECG results. For example, the Easy ECG Mobile PRO program makes it possible to take ECGs of different durations, use voice input to register patient information, print an ECG signal using a thermal printer or a regular computer printer, and filter the recorded ECG. The Poly-Spectrum-Mobile program works with a 12-channel electrocardiograph, which transmits information via bluetooth to a computer, as this program can also be installed on a smartphone or tablet. The analysis and formation of a syndromic ECG conclusion occurs in the cloud in about 2 seconds. The transmission of examination results can be transmitted via the Internet. The CardioSoft program analyzes not only ECG data, but also: spirometry and bronchodilation test; controls blood pressure; performs Holter monitoring [7].

In recent years, the capabilities of telemetry and remote syndromic ECG diagnostics and Holter monitoring have been tested. Automatic and medical conclusions were compared. ECG telemetry has demonstrated high efficiency in the diagnostics of left ventricular hypertrophy, MI, extrasystole, atrial fibrillation, and other cardiovascular pathologies [8]. A study of the results of remote monitoring, conducted on the basis of the research laboratory of the SSMU, with round-the-clock use of mobile ECG monitoring, showed that the sensitivity and specificity of such an ECG approached 100% in cardiac patients [9].

Ultrasound

In recent years, the ultrasound method has improved significantly due to the emergence of new modern sensors that allow you to create sound beams and selectively perceive signals in all projections of the volume of a tissue or object. Now you can constantly update the visual picture on the screen at high speed. This made it possible to obtain a high-quality three-dimensional image of the heart in almost real time. Because of the foregoing, this ultrasound option is called “live three-dimensional echocardiography” (live 3D-image). 3D ECHO-CG refines the information obtained using the standard ECHO-CG method.

In some hospitals, this is the only non-invasive way to obtain complete and reliable information about the state of the mitral, tricuspid valves, ventricular and atrial septal defects, and other cardiovascular pathologies [12].

Improvement in digital processing of ECHO-car-diographic data has led to the emergence of the so-called ECHO-CG speckle-tacking (STE). With this processing, each segment of the heart muscle is encoded with its own shade of gray. The STE evaluates the strains, which are the change in the length of the fiber relative to its (length) initial value. Strains are expressed as % of this change. The introduction of the STE method has significantly improved the quality of CVD diagnostics. An important advantage of STE is the possibility of differential diagnosis of left ventricular (LV) hypertrophy due to hypertension and hypertrophic cardiomyopathy. The STE technique is able to effectively diagnose IHD (longitudinal strain analysis), CHF (decrease in myocardial strain in the longitudinal, radial and circular direction), the phenomenon of cardiotoxicity in oncopathology, aortic valve pathology (decrease in longitudinal strain), myocardial infarction, etc. [16].

MRI

Magnetic resonance imaging (MRI), as a method, entered medical practice not so long ago, but showed high efficiency in the diagnosis of CVD. With the help of MRI, it is possible to obtain objective information about the area and properties of the post-infarction myocardial scar. For this, MRI is supplemented with gadolinium contrast, which makes it possible to clarify the boundaries between necrosis and healthy tissue. End-diastolic volume (EDV), end-systolic volume (ESV), and annulus diameter are determined much more accurately by MRI than by ECHO-CG. Contrasting with gadolinium followed by data analysis in 4 projections makes it possible to accurately determine the location and spread of the scar: this allows you to navigate the choice of the most appropriate treatment for ischemic cardiomyopathy [12].

Also, like many other instrumental methods, MRI makes it possible to clearly visualize the state of large coronary vessels. However, due to advances in technology, it is now possible to uncover the underlying mechanisms of microvascular disease that can lead to microvascular coronary disease, causing angina, MI, HF, and more. In the United States, microvascular dis- ease affects 3-4 million people and in 10-30% of them, invasive coronary angiography showed no signs of coronary artery disease [18, 19]. Since coronary microcirculation is less than the resolution achieved by coronary angiography, non-invasive methods for diagnosing microvascular disease have been proposed: MRI, contrast ECHO-CG and PET (positron emission tomography. Each method allows obtaining values of myocardial blood flow at rest and under stress, which makes it possible to assess perfusion [15].

CT scan

Dual-channel computed tomography, otherwise called “minimally invasive angiography” is a promising method for diagnosing the state of coronary blood flow. This is a type of multislice computed tomography (MSCT). The technique involves segment-by-segment tomographic scanning using two X-ray sources, which are located at an angle of 90º to each other. Snapshots are taken every 83ms, and this makes it possible to reproduce a high quality image even if the heart rate is much higher than normal. At the same time, the radiation dose is reduced by 50% compared to conventional helical CT due to the high synchronization of the emitters with the patient’s cardiogram [12].

Single photon emulsion CT (SPECT) has been a centerpiece of clinical imaging of the cardiovascular system for decades. SPECT-based assessment of the degree of myocardial ischemia as a percentage of left ventricular myocardium, together with concomitant measurements of left ventricular function and volume, has been well established for the diagnosis of myocardial ischemia [23]. SPECT not only has additional predictive value over clinical evaluation alone, but is also important for monitoring treatment. The current clinical paradigm that the degree of ischemia determines individual risk, which in turn should be used to make risk-based decisions about revascularization or optimized medical therapy, is based on a large number of SPECT perfusion imaging registries [24]. However, SPECT cannot distinguish between primary and collateral flow.

PET

The reference standard for non-invasive assessment of myocardial blood flow is positron emission tomography (PET, radionuclide tomography) with a load that allows you to quantify blood flow in ml / g / min. Clinically, quantification of myocardial blood flow by PET may help in the diagnosis of diffuse lesions and abnormal heart rhythms, which are associated with an increased risk of serious adverse cardiac events. In actual practice, the use of PET is limited by its availability (including radioisotopes), cost, and exposure to ionizing radiation [15, 25].

The studies showed that PET was more accurate (85%) than coronary CT angiography (74%) or SPECT (77%) in diagnosing myocardial ischemia and using FFR as a reference standard. The comparative accuracy of PET perfusion compared to CT or MRI, which have higher spatial resolution, has not yet been determined. The extent and severity of reversible perfusion defects recorded by PET contain important prognostic information, much more valuable than information obtained from the analysis of traditional cardiovascular risk factors. Coronary blood flow reserve obtained by PET showed additional predictive value for identifying women at risk with a higher incidence of non-obstructive coronary artery disease and potential microvascular dysfunction. Interestingly, apparently normal perfusion images with uniform indicator distribution can be reclassified based on diffusely blunted hyperemia of myocardial flow or coronary flow reserve: such patients have been shown to be at increased risk of future coronary events [25].

Biomarkers for cardiovascular disease

Lipid profile parameters are proven risk factors for CVD. Thus, at fixed values of LDL cholesterol, the risk of CVD increases 10 times with a decrease in HDL cholesterol.

CRP (C-reactive protein) is a marker of inflammation. In patients with acute heart failure, elevated CRP levels are associated with an increased risk of admission to the intensive care unit and in-hospital mortality. High CRP levels are associated with an increased risk of all-cause death (not specifically CVD death) and readmission for dilated cardiomyopathy.

The hydrophobic neuroendocrine peptide cates-tatin can become a useful biomarker for some cardiovascular diseases: myocardial infarction, arterial hypertension, chronic heart failure (CHF). Levels of catestatin increase in patients in the acute period of myocardial infarction and normalize only after 3 months. In hypertension, the concentration of cat-estatin decreases, and in chronic heart failure, its content positively correlates in accordance with the stage of CHF.

In recent years, active attempts have been made to discover new markers of cardiovascular diseases based on the study of large genomic associations (GWAS), transcriptomes, expression of individual key genes, non-coding RNAs, microRNAs, as well as using proteomics and lipidomics methods. Thus, growth and differentiation factor-15 (TGF-15) and soluble IL-33 receptor ST2 have become effective CVD biomarkers discovered using transcriptomic technologies. TGF-15 was elevated in NO-treated cardiomyocytes under oxidative stress in a congested left ventricle in mice with aortic stenosis and dilated cardiomyopathy. Elevated levels of ST2 led to myocardial hypertrophy, fibrosis, development of arterial hypertension, deterioration of left ventricular function.

Conclusions

A rich variety of modern diagnostic methods leads to an underestimation of the possibility of each of them. The ECG method remains relevant, which in most cases, with a highly qualified doctor of functional diagnostics, allows you to make the correct basic diagnosis. However, this is not enough, since a detailed functional assessment of cardiac activity and the state of large coronary and small vessels of the myocardium should be carried out. The most popular for assessing the state of the heart and its functional viability is the ECHO-CG method, which allows you to determine the degree of hypertrophy, dilatation of the left ventricle, diastolic volume and other important parameters of cardiac activity. However, this method is not very suitable for determining the degree of stenosis, and contrast coronary angiography should be performed, which allows you to perfectly visualize the localization, extent, extent of the stenotic lesion, and also determine its contours. Improving the methods of MRI, CT, SPECT, PET, 3-D ultrasound is gradually expanding their boundaries, and makes it possible to also assess vascular disorders. The introduction of tests for cardiac markers into clinical practice makes it possible to assess the severity of a cardiovascular problem and adequately determine the risks for each patient.

Statement on ethical issues

Research involving people and/or animals is in full compliance with current national and international ethical standards.

Conflict of interest

None declared.

190 | Cardiometry | Issue 24. November 2022

Author contributions

The authors read the ICMJE criteria for authorship and approved the final manuscript.