Effect of dipyridamole on myocardial perfusion and function using technetium-99m MIBI

Simultaneous assessment of function and perfusion during dipyridamole-handgrip Tc-99m sestamibi imaging in chronic coronary artery disease

The main goal of this work was to know the value of ventricular function in addition to perfusion Tc-99m sestamibi images in the assessment of coronary artery disease (CAD) when using dipyridamole (DIP) associated to isometric exercise. We analyzed 52 patients with suspected CAD; 40 of them had coronary lesions > or = 50% and 12 patients without CAD, conforming study and control groups, respectively. Twenty-eight patients had prior myocardial infarction. A two-day sestamibi protocol was employed with i.v. DIP-handgrip and rest injections, acquiring ECG-gated first pass and planar perfusion images. Sensitivity for perfusion images was 85% and specificity was 91.7%. There was no change between rest and DIP ejection fraction (EF) in controls. CAD patients presented a significant EF decrease with DIP (p: 0.0015). Patients with ischemia in perfusion images had larger EF decrease (p: 0.0001). For the analysis, an EF drop > or = 5% and any wall motion abnormality (WMA) were considered as having an abnormal response to DIP. CAD sensitivity improved significantly to 92.5% when adding EF drop and to 90% when adding WMA parameters, but specificity decreased to 75% with EF drop, and to 58.3% with WMA. In conclusion, first pass parameters from DIP-isometric exercise in addition to perfusion images are not a significant help in the assessment of CAD.

Lupus carditis: evaluation with technetium-99m MIBI myocardial SPECT and heart rate variability

The objective of this paper was to investigate the incidence of myocardial perfusion defects in patients with systemic lupus erythematosus (SLE) associated with dysautonomic alterations. Twenty patients without any sign or symptoms of heart disease, selected from a larger population of patients with SLE, underwent technetium-99m sestamibi (Tc-99m MIBI) single photon emission computed tomography (SPECT), at rest and after dipyridamole infusion; they also underwent heart rate variability (HRV) examination by a 24 hour ambulatory electrocardiography, analyzing in the time domain the standard deviation of the R-R intervals average (SDNN) and the percentage of R-R adjacent intervals differing from each other more than 50 msec (pNN50); in the frequency domain the low (LF) and high frequencies (HF) were analyzed. Twenty healthy volunteers served as control group for heart rate variability. At MIBI-SPECT examination, the scan was found abnormal in 15 patients and normal in five: three patients demonstrated reversible defects in the anteroseptal region, four had irreversible defects in a region (two in the anteroseptal region and two in the lateral region), two had rest defects in two different regions (lateral and inferior, lateral and anteroseptal) that improved during dipyridamole scan, and six had both reversible and irreversible defects: four in a single segment (three anteroseptal and one lateral, and two in two different regions, particularly anteroseptal and lateral, lateral and inferior). All 20 patients showed significantly lower HRV parameters in comparison with the control group, except for pNN50, which indicates decreased physiologic periodic fluctuations of the autonomic nervous system. In six patients who underwent coronary angiography, the epicardial vessels were found completely normal. In view of the high incidence of myocardial hypoperfusion in patients with HRV alterations, the authors hypothesize that autonomic dysfunction may be associated with microvascular disease or metabolic alteration. They also believe that MIBI scintigraphy is a suitable technique in detecting myocardial damage in SLE patients free of clinical manifestation.