Metabolic SPECT imaging may predict cardiac mortality
A resting radionuclide scan that can identify metabolically impaired myocardium may be able to stratify patients with end-stage renal disease (ESRD) but no apparent heart disease, according to risk of death from cardiac causes, suggests a study in the Jan.15 issue of the Journal of the American College of Cardiology.

Masato Nishimura, MD, PhD, and colleagues at Toujinkai Hospital in Kyoto, Japan, evaluated the potential of single-photon emission CT (SPECT) to predict cardiac death in chronic hemodialysis patients using the iodinated fatty acid analogue iodine-123 (123I)–?-methyl iodophenyl-pentadecanoic acid (BMIPP).

The researchers prospectively enrolled 375 asymptomatic hemodialysis patients for ESRD who had undergone dual-isotope SPECT imaging using 123I–BMIPP and 201thallium (Tl) chloride as tracers, a group that was without cardiovascular symptoms or apparent heart disease, including no history of MI or coronary revascularization. Patients who had a clinical history of myocardial infarction and/or coronary revascularization were excluded from the study. The uptake on SPECT images was graded in 17 segments on a five-point scale (0 normal, four absent), and assessed as summed BMIPP or Tl scores.

Dual-isotope SPECT imaging using BMIPP and conventional 201Tl as tracers was performed in 375 patients on chronic hemodialysis for ESRD, a group that was without CV symptoms or apparent heart disease, including no history of MI or coronary revascularization. After exclusion of 57 patients who underwent SPECT-driven percutaneous coronary intervention or coronary artery bypass graft surgery, 318 patients were tracked and showed a 15.7 percent rate of cardiac death—including sudden cardiac death, fatal MI, or death from heart failure—over a mean follow-up of 3.6 years.

During a mean follow-up of 3.6 years, 57 patients who had undergone coronary revascularization within 60 days of SPECT were excluded from the analysis. Among the remaining 318 patients (male/female: 170/148; and a men age of 64 years), 50 died of cardiac events (acute myocardial infarction 22, congestive heart failure 17, cardiac sudden death 11).

The Stepwise Cox hazard analysis associated cardiac death with age (70 years) and with severely abnormal BMIPP SPECT images (BMIPP summed scores 12). The Kaplan-Meier analysis showed that the cardiac death-free survival rates at three years were 61 percent and 98 percent in patients with BMIPP summed scores of 12 and greater than 12, respectively.

As a result of the research, the authors found that severely impaired myocardial fatty acid metabolism, which might mainly reflect repetitive myocardial ischemia, can identify a high-risk group of cardiac death among hemodialysis patients.