Assessment of Myocardial Perfusion by Tomography and Scintigraphy in Patients With Cardiac Stress Test With Ischemia
Condition: Myocardial Perfusion
MeSH terms: Ischemia
Study type: Observational [Patient Registry]

Summary: 
      Cardiovascular diseases are important cause of death, and of these have highlighted the
      Coronary Artery Disease (CAD) and its various clinical manifestations. The chest pain
      suggestive of ischemic heart disease is frequent complaint in medical consultations and
      hospitalizations . Complementary tests and images exams for risk stratification as Cardiac
      Stress Test (ET), the Myocardial Perfusion scintigraphy of (SPECT) are established for risk
      stratification and assessment workup in suspected ischemic heart disease. Coronary tomography
      angiography (CTA) has emerged as a robust method for non-invasive assessment of CAD, showing
      data diagnostics that directly correlate with invasive coronary angiography. Recently, the
      Myocardial Perfusion by Tomography Computed (CTP) has emerged as a new technique to measure
      the flow limitation for coronary microcirculation. In clinical practice, the exercise testing
      with electrocardiogram changes compatible with myocardial ischemia can lead to other
      examinations for elucidation of ischemic etiology, the most usual myocardial scintigraphy.
      However, a SPECT without evidence of ischemia, does not explain ischemic electrocardiographic
      changes triggered by physical stress, although it is a good marker prognostic. A CTP is a
      emerging tool in the evaluation of myocardial ischemia. Recent studies point to a good
      accuracy of the method compared to nuclear medicine. To test this hypothesis, this study aims
      to evaluate whether the CTP has a better diagnostic performance in detecting of obstructive
      or not obstructive CAD compared to the SPECT in the population of patients with exercise
      stress testing compatible with myocardial ischemia, and the computed tomography angiography
      (CTA) as the reference method. In addition, data from the exercise test (functional capacity,
      hemodynamics, electrocardiogram changes) will be compared to findings of CTA and CTP.
    

Detailed description: 
      Patients will be recruited in private Nuclear Medicine Service to perform myocardial
      perfusion scintigraphy with physical stress (SPECT-ET) that present the exercise test (less
      than 60 days) positive for ischemia, as electrocardiographic criteria enshrined in current
      guidelines of the Brazilian Society of Cardiology. These patients will be invited to
      participate in the study, guided and included after signing an informed consent form.

      Patients included in the study will be submitted to 2 images exams protocols:

        1. Myocardial perfusion scintigraphy with physical stress (SPECT-ET):

           Patients referred from other services with exercise testing positive ischemic response
           will be instructed to discontinue the drugs in use that may affect the ET as negative
           and coronary vasodilator action inotropic drugs. They will undergo perfusion study
           myocardial scintigraphy (SPECT) at rest and physical stress (1 day protocol), starting
           with Sestamibi Tn in injection 99 mtc at a dose of 10 millicurie and capture resting
           scintigraphic images in Gamma Camera GE millenium. Then they will undergo phase of
           physical stress, with maximum ET exercise, until exhaustion or intense physical exertion
           on the Borg Scale modified under Bruce protocol. At the peak of the effort will be
           injected into the radio tracer TC-99m Sestamibi at a dose of 30 mCi (milli Curie), and
           then quantified in Gamma Camera GE millenium scintigraphic images after physical stress.

           During the exercise test electrocardiographic variables will be evaluated as magnitude
           and morphology of ST segment changes, precocity and duration of these changes,
           hemodynamic variables such as behavior of the pressure curve and clinical variables.

           The perfusion myocardial study by Gated SPECT (single-photon emission computed
           tomography) will be analyzed qualitatively by 2 experienced examiners and
           semi-quantitatively using severity scores widely validated in the literature (SSS -
           Summed Stress Score; SRS - Summed Rest Score: SDS - summed Difference Score).

        2. Myocardial Perfusion and Angiography by Computed Tomography. Patients will undergo
           myocardial perfusion computed tomography with multiple detectors after dipyridamole, as
           established protocol anteriores10 studies, followed by coronary angiography at rest
           (CTA) in tomography with 128 multi-detector channels Optima 660 CT (GE ).

      Patients will be instructed to perform absolute fast 4 hours for the exam, and fasting for 24
      foods with caffeine and medications containing xanthine derivatives. It will be obtained
      venous access caliber in the right upper limb and cardiac monitoring continues. They will be
      assessed and recorded weight, height, blood pressure (BP), heart rate (HR) at rest and
      respiratory rate before, during and after the examination tomography.

      The evaluation of the pharmacological stress PMTC be performed after dipyridamole
      administration in a dose of 0,56mg / kg for 4 minutes. images, according to protocol
      previously validated in this study instituição10 immediately after injection of iodinated
      contrast After 2 minutes of dipyridamole administration of completion will be performed.
      Approximately 60ml of nonionic iodinated intravenous contrast medium is administered by an
      automated gun to a 3ml / s.

      After the stress phase and the pharmacological reversal with aminophylline (240 mg), will be
      held the control of heart rate (metoprolol 5 mg IV every 5 minutes [max. 20mg] with the
      objective of reaching a HR ≤ 60), for carrying out the acquisition of coronary angiography.
      The acquisition parameters for CTA (resting phase) will be individualized according to the
      weight, sex and heart rate of each patient, in order to maintain a total dose of not more
      radiation 15mSv therefore a safe dose of radiation with the image quality maintenance.
      three-dimensional reconstructions and perfusion algorithm will be performed with the use of
      dedicated workstation (ADW4.6 [GE]).
    

Observational model: Case-Only
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Volunteers of the population with positive exercise test for ischemia
      
Keywords: Spect; Stress Test; Myocardial Perfusion CT; CT angiography