**7. Instrumental methods for diagnosing HF**

Echocardiography is most important for confirming the diagnosis of HF as a screening method, since if EF ≤40%, the diagnosis can be considered proven. But there are few such patients in outpatient practice. Thus, most outpatient patients have diastolic heart failure. The diastolic insufficiency is the inability of the heart to accept all the blood that flows to it, while there is stagnation (increased pressure) in front of the heart chambers. This situation can occur only with physical activity, and in advanced cases also at rest.

Global longitudinal strain (GLS) is a more reproducible parameter regardless of echocardiographic training and image quality compared to EF [17]. As GLS ordinarily varies with age, sex, and LV loading conditions, defining abnormal GLS is not uncomplicated. However, in adults, GLS <16% is abnormal, GLS >18% is normal, and GLS 16–18% is borderline [18].

Traditionally, diastolic insufficiency is assessed by the ratio of the velocity of early transmitral filling (e) and the average early velocity of diastolic movement of the base of the mitral valve ring (e') [19]. It is an accurate, reliable and easily reproducible method for evaluating left ventricular diastolic function. This method does not require a sinus rhythm. In normal persons the E/e' ratio is <8. Values >14 have high specificity for increased LV filling pressures. In the range e/e' from 8 to 14, it is not possible to determine definitely the presence of HF. The accuracy of the indicator is reduced in severe mitral valve calcification, mitral valve defects, pericarditis and the presence of violations of regional contractility of the left ventricle.

Since the left atrium is also overloaded when the filling pressure of the left ventricle increases, it is important to detect the enlargement of the left atrium for the diagnosis of HF. However, it should be taken into account that the atrium can be expanded in athletes and with atrial fibrillation and flutter.

In symptomatic patients with normal levels of NTproBNP, no reduction in EF and signs of stagnation, as well as normal cardiac filling pressures at rest may have markedly abnormal hemodynamic responses during exercise [20]. An exercise pulmonary artery systolic pressure ≥ 45 mm Hg identified HF with 96% sensitivity and 95% specificity. However, such invasive tests are not acceptable for outpatient clinics.

If the etiology of HF is unclear, the need to assess the structures of the heart and surrounding tissues, assess the severity of fibrosis, differential diagnosis of inflammatory, accumulative and ischemic causes, the patient should perform cardiovascular magnetic resonance (CMR) tracking with or without an assessment of late gadolinium enhancement (LGE). A fast long-axis strain (FLAS) at end-systole of 12.3% and less predict the presence of HF [21]. The sensitivity and specificity of the method is 93% and 86%, respectively. This method is reproducible, reliable, and effective, but expensive.

*Features of Diagnostics and Differential Diagnostics of Chronic Heart Failure in Outpatient… DOI: http://dx.doi.org/10.5772/intechopen.95863*
