ABC | Volume 114, Nº2, February 2020

Update Update of the Brazilian Guideline on Nuclear Cardiology – 2020 Arq Bras Cardiol. 2020; 114(2):325-429 Table 9 – Exercise testing parameters associated with unfavorable prognosis and multivessel coronary disease. • ECG: - ST-segment depression ≥ 2 mm, with descending morphology and early appearance (metabolic load < 5 - 6 METs), involving multiple leads, usually lasting for ≥ 5 minutes of recovery - Exercise-induced ST-segment elevations - Reproducible, symptomatic, or sustained ventricular tachycardia (> 30 s) • Metabolic load < 5 – 6 METs* • Chronotropic incompetence • Systolic blood pressure: inability to reach values ≥ 120 mmHg, or sustained decrease ≥ 10 mmHg, or fall below resting values during progressive exercise • Symptoms: angina pectoris when performing a lower workload , generally during the beginning of exercise, when conventional protocols are applied ECG: electrocardiogram; MET: metabolic equivalent. (*1 MET = oxygen consumption in supine resting conditions, equivalent to 3.5 mL.kg -1 .min -1 ) function, simultaneous with myocardial perfusion evaluation. This information adds data to the medical decision-making process within known incremental prognostic values, and it improves test accuracy, especially regarding specificity values. Considering this aspect, in situations where there are doubts between persistent perfusion defects and/or artifacts (due to breast or diaphragmatic attenuation), analysis of ventricular wall motility and thickness may contribute to differentiating these two causes. When apparent reduced relative uptake of a radiopharmaceutical is due to an artifact, the motility and systolic thickness of this wall are normal. The estimated results of left ventricular ejection fraction (LVEF) that are conventionally considered normal vary according to technique and methodology employed. With the Gated-SPECT technique, this value is ≥ 50% for both sexes; there are few references with differentiated values for men and women, in addition to different established limits of normality. Due to specific aspects related to methodologies used to calculate LVEF, values found in individuals who are shorter and individuals with smaller ventricular cavities and/ or hypertrophic ventricles, especially in women, may be overestimated, at times exceeding values of 75% to 80%. Calculations of LVEF and ventricular volumes obtained by Gated-SPECT may be utilized for prognostic stratification. LVEF < 45% and end systolic volume (ESV) > 70 ml are associated with increased risks of cardiac death. 42,43 This analysis may be carried out either while resting or under stress; it should preferably be done during both steps, however, considering the possibility of detecting transient LV dysfunctions induced by physical exercise or pharmacological stress. Cardiac arrhythmias pose difficulties to the acquisition of ECG-synchronized images and may significantly influence the results obtained for ejection fraction and produce artifacts in myocardial perfusion images. There is a technically defined time window for RR interval variation, generally around 20%, after which point heartbeats are rejected. This situation means that if there is an arrhythmia which produces variations between RR intervals above these established limits, such as persistent AF, the corresponding data from that specific cardiac cycle will be rejected, and there will consequently be lower counting statistics. In these cases, images should be acquired without ECG synchronization in order to avoid the occurrence of artifacts. 5.4. Cardiovascular Stress The basic principle of using cardiovascular stress associated with myocardial perfusion images consists of creating heterogeneity in blood flow between vascular territories irrigated by normal coronary arteries with significant obstructive stenoses. 44,45 The use of myocardial perfusion agents makes it possible to visualize this heterogeneity in regional blood flow. In practice, of all existing cardiovascular stressors, only ET and pharmacological tests have been used. Both stressmodalities, physical exercise and pharmacological vasodilation, have similar sensitivity and specificity for the detection of CAD via analysis of perfusion images. 46-48 Physical stress: ET is the associated method of choice for diagnostic and prognostic values, which have already been established in conformity with clinical, hemodynamic, and electrocardiographic variables obtained during exercise, which add incremental data to myocardial perfusion study. Stress tests have a higher chance of revealing abnormalities in patients with more severe and extensive obstructive arterial disease. Chest pain and/or decreased systolic blood pressure (SBP) during low levels of exercise are highly important findings that are associated with adverse prognoses and multivessel coronary disease. Other markers of unfavorable prognosis include high-magnitude ST segment depression, with a horizontal or downsloping aspect, which may appear early during low workloads or be characterized by late recovery after stress has ceased, present in multiple leads, among others (Table 9). Some studies have incorporated stress test variables into diagnostic and prognostic scores. 49 The most widely used in our context is the Duke prognostic score. Using Cox’s regression analysis, Mark DB et al. proposed 50 and validated 51 this score for use with the exercise treadmill test and the Bruce protocol. It is calculated by the following formula: DS = T (min) - (5 x ST) - (4 x AI) or Duke Score = exercise time (in minutes) - (5 × ST deviation in millimeters) – (4 × angina index) The angina index has a value of 0 (zero) if there are no symptoms during exercise, 1 (one) if non-limiting chest pain 338