Myocardial Reperfusion/radionuclide imaging

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Editorial

Single Photon Computed Tomography-Myocardial Perfusion Scintigraphy. Diagnostic Tool Anticipating the Disease

Without making any value judgment, a large percentage of physicians who request tests to make diagnoses is observed in the contemporary clinical practice. On the other hand, a considerable percentage of physicians who make the diagnosis and possibly ask for tests to confirm the diagnosis is also observed. Both behaviors are considered valid when common good is achieved: The patients’ benefit. However, the request for tests without an appropriate criterion is not only harmful to the patient, but also to the system.

In present-day medicine, there is a large collection of tests considered normal throughout the medical knowledge area, including cardiology. In a publication by Dippe Jr et al. in this issue, the authors, in a retrospective analysis of a database, found this trend. Of 5,526 scans of myocardial perfusion scans performed on obese patients (grade 1), 77% were considered normal. Assuming that the exams were requested for investigation of myocardial ischemia, the authors related the presence of perfusion deficit with myocardial ischemia in only 23%. Based on these data, they found, after applying a “creative statistic”, a 245% risk-ratio for typical angina. It is known, in principle, that perfusion deficit is an expression of intrinsic myocardial abnormality.

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Original Article

Study of Myocardial Perfusion in Obese Individuals without Known Ischemic Heart Disease

Tufi Dippe Jr. et al. Cláudio Leinig Pereira da Cunha Rodrigo Julio Cerci Arnaldo Lafitte Stier Jr. João Vicente Vítola

Abstract

Background:

Obesity is associated with an increased risk of type 2 diabetes mellitus (DM), ischemic heart disease (IHD) and cardiovascular mortality. Several studies have demonstrated the diagnostic and prognostic value of single photon computed tomography-myocardial perfusion scintigraphy (SPECT-MPI) in the evaluation of patients with suspected IHD, including in obese population. Data on clinical risk factors and their association with abnormal myocardial perfusion in obese patients are scarce in the Brazilian population.

Objective:

To determine the factors associated with abnormal myocardial perfusion in obese individuals without known IHD.

Methods:

We studied obese patients without known IHD who were referred for evaluation through SPECT-MPI between January 2011 and December 2016. Clinical variables and results of SPECT-MPI were obtained systematically. The distribution of continuous variables was assessed using the Shapiro-Wilk and Shapiro-Francia tests. We used the unpaired Student t test to compare the means of continuous variables with normal distribution and the Chi Square test for binomial variables analysis. A p value < 0.05 was considered statistically significant. The association of the clinical variables for the presence of factors associated with abnormal myocardial perfusion was determined by univariate and multivariate logistic regression analysis, and respective odds ratios (OR) and 95% confidence intervals (CI).

Results:

The study sample consisted of 5,526 obese patients. Mean body mass index (BMI) of our patients was 33.9 ± 3.7 kg/m², 31% had DM, and myocardial perfusion abnormalities was observed in 23% of the total sample. The factors associated with abnormal myocardial perfusion on multivariate analysis were: age (OR: 1.02, 95% CI 1.01-1.03, p < 0.001), DM (OR: 1.57, 95% CI 1.31-1.88, p < 0.001), typical angina before the test (OR: 2.45, 95% CI: 1.82-3.31, p < 0.001), need for pharmacologic stress test (OR: 1.61, 95% CI: 1.26-2.07, p < 0.001), less physical effort evaluated in metabolic equivalents (METs) during the exercise treadmill test (OR: 0.89, 95% CI: 0.85-0.94, p < 0.001) and a lower post-stress left ventricular ejection fraction after stress (LVEF; OR: 0.989, 95% CI: 0.984-0.994, p < 0.001).

Conclusion:

The factors associated with abnormal myocardial perfusion in obese patients without known IHD were age, DM, presence of typical angina, ventricular dysfunction, and inability to undergo physical stress as clinical variables, in addition to functional capacity during physical stress.