Eva V Dubovsky | Search PubMed

PubMed2006

Outcome of patients with adenosine-induced ST-segment depression but with normal perfusion on tomographic imaging.

Most patients with ST depression during adenosine infusion have reversible perfusion defects by single-photon emission computed tomographic (SPECT) perfusion images. Occasionally ST depression is observed in the setting of normal perfusion images. The outcome of such patients is controversial. We identified 65 patients who underwent gated SPECT perfusion imaging with adenosine as the stress agent. These patients were selected based on the following criteria: none had previous myocardial infarction or coronary revascularization, all were in sinus rhythm, and none had left bundle branch block. The 65 patients had normal SPECT images but ischemic ST response (>or=1 mm ST depression). There were 52 women and 13 men who were 66 +/- 13 years of age. History of diabetes mellitus was present in 16 patients (25%) and hypertension in 48 patients (74%). At a mean follow-up of 24 months, there were no cardiac deaths or myocardial infarctions, and there were 6 coronary revascularization procedures (2 coronary artery bypass graftings and 4 coronary stentings of 1-vessel coronary disease). One patient died of cancer. In conclusion, patients with no previous myocardial infarction or coronary revascularization who have normal SPECT images have a benign outcome despite the presence of ST depression (0% for death or myocardial infarction and 4.6%/year for coronary revascularization). Balanced ischemia could not be a common cause for discordant perfusion and ST response.

Adenosine↗

PubMed2002

A Bayesian regression model for plasma clearance.

UNLABELLED: Nonlinear Bayesian regression permits curve fitting to a group of subjects simultaneously rather than individually. We evaluated this approach for interpreting plasma clearance curves with the goal of reducing curve-fitting failures and dealing objectively with problem datasets that may arise in clinical settings. METHODS: (99m)Tc-Diethylenetriaminepentaacetic acid plasma clearance curves from 79 subjects were analyzed. The data typically comprised 7-9 samples obtained from 5-10 to 180-240 min after injection. A 2-compartment model was fitted by Bayesian regression to yield compartmental hyperparameters V1, L21, and L12 corresponding to the volume of the compartment into which tracer was injected and the transfer rates from compartment 1 to compartment 2 and from compartment 2 to compartment 1, respectively. This also yielded a clearance estimate for each subject. RESULTS: Estimated hyperparameters were V1 = 8.9 L, L21 = 0.026 min(-1), and L12 = 0.040 min(-1). Conventional methods led to fitting failures in 2 of the 79 subjects but there were no failures with the Bayesian method. The hyperparameters were used to calculate the glomerular filtration rate for each subject from a single plasma sample with a root-mean-square error of 7.3 mL/min, which was not significantly different from the widely used Christensen-Groth formula. CONCLUSION: Fewer fitting failures were encountered than with conventional methods, offering an objective means of dealing with problem data. This conceptually simple model can be used directly to calculate clearance from a single plasma sample. It requires only the 3 parameters described above, whereas the Christensen-Groth method requires 6 parameters.

Adult↗