ABC | Volume 114, Nº2, February 2020

Update Update of the Brazilian Guideline on Nuclear Cardiology – 2020 Arq Bras Cardiol. 2020; 114(2):325-429 identification of low-risk patients has been carried out more rapidly. In this process of diagnostic and prognostic assessment, the following play an important role: resting ECG, cardiac enzymes, and non-invasive exams such as ET, MPS, Doppler echocardiogram, and coronary angio-CT, in addition to cardiac resonance in specific cases. The choice of recommended imaging method should be based on the procedures available, local institutional experience, and present clinical situation. The exam with the highest diagnostic accuracy and negative predictive value (NPV) will offer more precise risk stratification, which is fundamental to decision making regarding need for hospital admission or safe discharge from the emergency unit. In addition to the 2 physiopathological conditions described (Non-ST segment Elevation Myocardial Infarction – NSTEMI and ST segment elevation myocardial infarction – STEMI), unstable angina also stands out, which does not feature myocardial necrosis as an initial consequence. 155,156 Nevertheless, unstable plaque and evolutive phenomena of erosion and rupture may progress to infarction and related complications, such as severe arrhythmias, ventricular dysfunction, and death. Conditions of vasospasm, in epicardial coronary arteries or with microvascular disease, have additionally been implicated in ACS without thrombosis and myocardial infarction, in the absence of obstructive lesions. 157-159 It is, finally, important to emphasize that, in patients with documented ACS and intermediate- to high-risk patients, invasive coronary cineangiography and percutaneous revascularization represent the most frequent forms of initial assessment, and non-invasive imaging methods are reserved for clinically stable situations and low- to intermediate-risk patients, with the aim of reclassifying risk, diagnosis, and stratification in the post-event phase. 160,161 7.2. Goals for Evaluating Acute Chest Pain and Participation of Non-invasive Methods in Assessing ACS 154,162,163 • Precise diagnosis for appropriate conduct in UA or AMI, whether with clinical treatment or invasive strategy via catheterization and angioplasty. • Early, safe discharge from the hospital if clinical data and exams show no abnormalities. Probability of severe cardiac events < 1% over 30 days of evolution following discharge from the emergency unit or hospital. Following serial evaluation of ECG, without modifications, in addition to normal cardiac enzymes and clinical situation characterized as low- to intermediate-risk, non-invasive functional exams may play an important role in risk stratification of patients with acute chest pain. The choice of MPS, cardiac resonance, or angio-CT will depend on the objective and the clinical question to be answered. Exercise testing: constitutes an important strategy for assessing patients with suspected ACS following stabilization, and it aids prognosis and medical management . Patients with chest pain in the emergency room, once they have been identified as low-risk, may undergo ET, a normal result of which confers low annual risk of cardiovascular events, allowing for earlier and safer discharge from the hospital. 164 Brazilian and international guidelines recommend ET as a first-choice exam for risk stratification in patients who are able to exercise, as the procedure is low-cost and widely available, and it has a low rate of complications, similar to that of tests conducted in normal conditions. 165 A treadmill or a cycle ergometer may be used, following appropriate protocols for the patient’s clinical conditions, such as the ramp protocol or the modified Naughton or Bruce protocol. Logistics related to performing ET in the emergency unit may, however, be compromised as a result of unavailable operational personnel or infrastructure during certain periods (e.g. weekends or night shifts). Summary of indications for ET in ACS (characterize low-risk after initial clinical stratification) • Baseline ECG and biomarkers (necrosis) without alterations. • Absence of symptoms (precordial pain or dyspnea). • Hemodynamic stability and adequate conditions for physical effort. If ET results are normal and the patient has shown good functional capacity, other procedures may be unnecessary, in virtue of the test’s high NPV. 165 Summary of Recommendations and Evidence Class of recommendation I. Level of evidence: B • Low-risk (clinical and ECG) patients with normal biomarkers should be referred for exercise test after 9 to 12 hours. Within the routines of chest pain units, these exams may be used as discharge criteria. If it is not possible to perform ET or if ECG is uninterpretable, the patient may undergo provocative tests for ischemia associated with non-invasive imaging. Doppler echocardiogram (ECHO): This is fundamental for evaluating patients with acute chest pain 166-168 and evolving ACS, initially considering LVEF, segmentary contractile alterations, and the presence of thrombi, in addition to mechanical complications (rupture of interventricular septum or papillary muscles) that result in severe events, such as cardiorespiratory arrest. Moreover, this method may also evaluate chest pain with non-coronary etiology, such as pericardial disease, hypertrophic cardiomyopathy, aortic dissection in the presence of renal insufficiency that makes it impossible to perform angio-CT, and others. In addition to assessing the presence and extent of ventricular dysfunction, it is able to quantify severity of valvular abnormalities that may be present and associated with ischemic etiology. Summary of Recommendations and Evidence Recommendation class I • Transthoracic ECHO is indicated when there is clinical suspicion of aortic and pericardial diseases, pulmonary embolism, and valvulopathies ( level of evidence: C ). • In cases with complications resulting from unstable ACS, such as interventricular communication and mitral insufficiency ( level of evidence: C ). • Stress echocardiography is considered an alternative to exercise testing in patients who cannot exercise ( level of evidence: B ). 354