ABC | Volume 114, Nº2, February 2020

Update Update of the Brazilian Guideline on Nuclear Cardiology – 2020 Arq Bras Cardiol. 2020; 114(2):325-429 exercise but who are using medications that limit increases in HR (betablockers, antiarrhythmic drugs, et al.). New drugs: There are 3 types of adenosine receptors (Table 16). The use of specific selective antagonists to A 2 receptors has shown evidence of adequate coronary hyperemia and lower intensity of systemic effects, especially chest pain and atrioventricular blockage. A double-blind, randomized (regadenoson or adenosine), multicenter study 78 involving 784 patients has shown that diagnostic information is similar and that there were no serious adverse effects; regadenoson, however, was tolerated better than adenosine. Second-degree atrioventricular blockage occurred in 3 patients with adenosine and in no patients with regadenoson. Regadenoson’s short biological half-life minimizes and limits the duration of adverse effects, diminishing monitoring time. It is administered via bolus, and it is not necessary to adjust dose to body weight (Figure 7). Its use is promising in patients with chronic obstructive pulmonary disease. The incidence of serious complications 79 with the performance of cardiovascular stress is related in Table 17. Table 14 – Contraindications to dobutamine use 24,46 Absolute • Cardiac arrhythmias including atrial fibrillation and ventricular tachycardia (sustained or non-sustained) • Severe aortic stenosis and hypertrophic obstructive cardiomyopathy • Systolic arterial hypotension (< 90 mmHg), uncontrolled systolic arterial hypertension (systolic > 200 mmHg), severe or stage III hypertension • Unstable angina or recent myocardial infarction • Aneurysms or aortic dissection • Symptomatic vascular cerebral insufficiency • Presence of implanted cardiac defibrillator • Alterations in metabolism of potassium Relative • Abdominal aortic aneurysm (> 5 cm in diameter) • Presence of thrombi in left ventricle • Left ventricular ejection fraction < 25% (due to increased risk of ventricular arrhythmias) Figure 6 – Myocardial perfusion scintigraphy associated with intravenous administration of dobutamine solution (250 mg or 1 vial diluted in 250 ml of saline solution). It may begin with an alternative initial dose of 5 mcg.kg - 1 .min -1 , for 3 minutes, with sequentially increasing doses every 3 minutes, up to 40 mcg.kg -1 .min -1 or until 85% of maximum heart rate has been reached (explained in the figure and the text), at which point the radiopharmaceutical (MIBI- 99m Tc or 99m Tc-tetrofosmin) is injected. In the event of inadequate increase in heart rate and in the absence of contraindications (glaucoma, prostatic hypertrophy), atropine is additionally recommended, either early on or starting at the third step. Injection of the radiopharmaceutical After reaching 85% maximum heart rate, the radiopharmaceutical is injected and the Dobutamine infusion continues for 1 more minute. Dobutamine IV Incremental IV infusion mcg.Kg -1 .min -1 DOBUTAMINE End 85% mcg/kg/min Time (minutes) Table 15 – Adverse effects related to dobutamine infusion for myocardial perfusion scintigraphy 24,46 Adverse effects % ST alterations 33 Precordial pain 31 Palpitation 29 Headache 14 Facial flushing 14 Dyspnea 14 Significant arrhythmias (supraventricular and ventricular) 8 to 10 343