Myocardial Perfusion Imaging

IJCS

Editorial

Myocardial Perfusion Imaging: Always Evolving

Myocardial perfusion assessed by nuclear medicine began to be used in clinical practice in the 1970s with the radiotracer 201-thallium chloride in two-dimensional images.

Advances in the development of equipment, from the possibility of three-dimensional images by single-photon emission computed tomography (SPECT), and new tracers, such as those linked to 99-technetium, have allowed the consolidation of nuclear cardiology as a non-invasive tool with high diagnostic accuracy in the context of coronary artery disease.

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IJCS

Original Article

Comparison between Bruce and Ramp Protocols for Exercise Testing in the Diagnosis of Myocardial Ischemia

Thiago Teixeira da Silveira Fagundes et al. Carolina Christianini Mizzaci Susimeire Buglia Fabricio da Costa Wohnrath … Flavia Medina João França Rica Dodo Delmar Buchler Luiz Eduardo Mastrocola Romeu Sérgio Meneghelo

Abstract

Background:

Exercise tests are an important tool in the investigation of myocardial ischemia. The ramp protocol has gained increasing importance in clinical practice because of the possibility of individualizing its exercise intensity.

Objective:

To assess and compare the sensitivity, specificity, and accuracy of Bruce and ramp protocols for exercise testing in the diagnosis of myocardial ischemia considering myocardial perfusion scintigraphy as the reference standard. Secondary objectives included the assessment of hemodynamic profiles, functional capacity, and the incidence of arrhythmias in each of the protocols.

Methods:

Participants underwent exercise testing using the ramp and Bruce protocols, and the tests’ diagnostic power was assessed. For testing the difference between data provided by both protocols, we used a paired Student’s t-test or Wilcoxon test, depending on the assumption of data normality. The level of significance adopted for all tests was 5%.

Results:

The ramp protocol showed sensitivity, specificity, and accuracy values of 55.6%, 82.4%, and 76.7%, respectively, whereas the Bruce protocol had results of 77.8%, 64.7%, and 67.4%, respectively. The maximum heart rate and double product at peak exercise were significantly higher in the Bruce protocol (p = 0.043 and p = 0.040, respectively). No differences were observed between the incidence of arrhythmias in both protocols.

Conclusion:

The Bruce protocol presented higher sensitivity for detecting ischemia on the exercise test, while the ramp protocol presented higher specificity and accuracy.

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Original Article

Does Tight Glucose Control During the First 24 hours of Hospitalization Reduce Scintigraphic Infarct Size in STEMI Patients?

Kamil Gulsen et al. Burak Ayca Murat Baskurt Baris Okcun Murat Kazim Ersanli

Abstract

Background

Hyperglycemia at the time of admission is related to increased mortality and poor prognosis in patients diagnosed with ST-segment elevation myocardial infarction (STEMI).

Objective

We aimed to investigate whether tight glucose control during the first 24 hours of STEMI decreases the scintigraphic infarct size.

Methods

The study population consisted of 56 out of 134 consecutive patients hospitalized with STEMI in a coronary care unit. Twenty-eight patients were treated with continuous insulin infusion during the first 24 hours of hospitalization, while the other 28 patients were treated with subcutaneous insulin on an as-needed basis. The final infarct size was evaluated with single-photon emission computed tomography (SPECT) in all patients on days 4 to 10 of hospitalization. The groups were compared and then predictors of final infarct size were analyzed with univariate and multivariate linear regression analysis. A p-value < 0.05 was considered statistically significant.

Results

The mean glucose level in the first 24 hours was 130 ± 20 mg/dL in the infusion group and 152 ± 31 mg/dL in the standard care group (p = 0.002), while the mean final infarct size was 20 ± 12% and 27 ± 15% (p = 0.06), respectively. The multivariate linear regression analysis demonstrated that the mean 24-hour glucose level was an independent predictor of the final infarct size (beta 0.29, p = 0.026).

Conclusion

Tight glucose control with continuous insulin infusion was not associated with smaller infarct size when compared to standard care in STEMI patients. (Int J Cardiovasc Sci. 2020; [online].ahead print, PP.0-0)

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Case Report

Left Ventricular Dyssynchrony in a Patient with Normal Perfusion and Stress-Induced Left Bundle Branch Block

Maria Gazzilli et al. Rexhep Durmo Claudio Tinoco Mesquita Raffaele Giubbini

Introduction

Left bundle branch block (LBBB) is an electrocardiographic abnormality that occurs in approximately 0.5-1.1% of all patients who undergo exercise testing. The diagnosis of complete LBBB is made with the 12-lead electrocardiogram (ECG) if all the following criteria are met: conduction originating above the atrioventricular node; a QRS duration of 120 milliseconds or more; predominantly upright complexes with broad-slurred R waves in leads I, V5, and V6; and a QS or RS pattern in V1 with a normal intrinsicoid deflection of 35 milliseconds.

The precise mechanism and the prognostic significance of Exercise Induced-LBBB (EI-LBBB) remains unclear. EI-LBBB can be associated with coronary artery disease (CAD). However, in a group of patients, coronary arteries are normal. Several authors have attributed EI-LBBB to functional alterations of the conduction system mediated by autonomic influences in non-ischemic cases. We report a case of a 72-year-old female patient who developed LBBB during exercise stress testing and showed reversible abnormalities in cardiac contraction.

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