Assessment of the long-term reproducibility of baseline and dobutamine-induced myocardial blood flow in patients with stable coronary artery disease.
UNLABELLED
Although physical exercise is the preferred stimulus for cardiac stress testing, pharmacologic agents are useful in patients who are unable to exercise. Previous studies have demonstrated short-term repeatability of exercise and adenosine stress, but little data exist regarding dobutamine (Dob) stress or the long-term reproducibility of pharmacologic stressors in coronary artery disease (CAD) patients. PET allows accurate, noninvasive quantification of myocardial blood flow (MBF) and coronary flow reserve (CFR). The aim of the study was to investigate the long-term reproducibility of Dob stress on MBF and CFR in CAD patients using PET.


METHODS
Fifteen patients with chronic stable angina and angiographically proven CAD (>70% stenosis in at least 1 major coronary artery) underwent PET with (15)O-labeled water and Dob stress at baseline (time [t] = 0) and after 24 wk (t = 24). MBF at rest and MBF during Dob stress were calculated for the whole left ventricle, the region subtended by the most severe coronary artery stenosis (Isc), and remote myocardium subtended by arteries with minimal or no disease (Rem). Reproducibility was assessed using the Bland-Altman (BA) repeatability coefficient and was also expressed as a percentage of the mean value of the 2 measurements (%BA).


RESULTS
Dob dose (30 +/- 11 vs. 031 +/- 11 microg/kg/min; P = not significant [ns]) and peak Dob rate.pressure product (20,738 +/- 3,947 vs. 20,047 +/- 3,455 mm Hg x beats/min; P = ns) were comparable at t = 0 and t = 24. There was no significant difference in resting or Dob MBF (mL/min/g) between t = 0 and t = 24 for the whole left ventricle (1.03 +/- 0.19 vs. 1.10 +/- 0.20 and 2.02 +/- 0.44 vs. 2.09 +/- 0.57; P = ns for both), Isc (1.05 +/- 0.24 vs. 1.10 +/- 0.26 and 1.79 +/- 0.53 vs. 1.84 +/- 0.62; P = ns for both), or Rem (1.03 +/- 0.23 vs. 1.10 +/- 0.26 and 2.27 +/- 0.63 vs. 2.26 +/- 0.63; P = ns for both) territories. Global (1.98 +/- 0.40 vs. 1.90 +/- 0.46; P = ns) and regional CFR (Isc: 1.65 +/- 0.40 vs. 1.67 +/- 0.47, and Rem: 2.25 +/- 0.57 vs. 2.06 +/- 0.51; P = ns) were reproducible. The BA repeatability coefficients (and %BA) for MBF in ischemic and remote territories were 0.3 (28%) and 0.26 (24%) at rest and 0.49 (27%) and 0.58 (26%) during Dob stress.


CONCLUSION
In patients with clinically stable CAD, Dob induces reproducible changes in both global and regional MBF and CFR over a time interval of 24 wk. The reproducibility of MBF and CFR with Dob was comparable with the short-term repeatability reported for adenosine and physical exercise in healthy subjects.