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CLINICAL RESEARCH: CARDIAC IMAGING

Risk Stratification With Electrocardiographic-Gated Dobutamine Stress Technetium-99m Sestamibi Single-Photon Emission Tomographic Imaging

Value of Heart Rate Response and Assessment of Left Ventricular Function

Sachin M. Navare, MD^_*,, Deborah Katten, RN, MPH^_*, Lynne L. Johnson, MD^,, Jeffery F. Mather, MS^_*, Michael S. Fowler, MD^_*,, Alan W. Ahlberg, MA^_*, Nicholas Miele, BS^, and Gary V. Heller, MD, PhD^_*,,_*

^_* Nuclear Cardiology Laboratory of the Henry Low Heart Center, Hartford Hospital, Hartford, Connecticut
University of Connecticut School of Medicine, Farmington, Connecticut
Nuclear Cardiology Laboratory, Cardiology Division of the Rhode Island Hospital, Providence, Rhode Island
Brown University School of Medicine, Providence, Rhode Island.

Manuscript received March 10, 2005; revised manuscript received August 11, 2005, accepted September 19, 2005.

^_* Address for correspondence: Dr. Gary V. Heller, Nuclear Cardiology Laboratory, Hartford Hospital, 80 Seymour Street, Hartford, Connecticut 06102. (Email: gheller{at}harthosp.org).

OBJECTIVES: The purpose of this research was to evaluate the significance of heart rate response to dobutamine and the assessment of left ventricular (LV) function during risk stratification of patients undergoing dobutamine stress myocardial perfusion imaging (DSMPI).

BACKGROUND: Dobutamine stress myocardial perfusion imaging has been shown to effectively risk stratify highly selected patients. However, based on perfusion alone, patients with normal and abnormal tests have twice the risk as comparable patients with exercise testing. The added value of assessment of LV function and the heart rate response to dobutamine in risk stratification of these patients is unknown.

METHODS: Follow-up information (cardiac death or non-fatal myocardial infarction) was obtained on 1,367 consecutive patients who underwent DSMPI due to inability to perform adequate exercise and contraindications to vasodilators. Perfusion images were interpreted using a 17-segment model. Abnormal perfusion and function were defined as: summed stress score 4 and ejection fraction <50%, respectively.

RESULTS: Annualized event rates (AERs) were related to the extent/severity of perfusion defects and worsening LV function. A three-risk category model was constructed from combined assessment of perfusion and function, with AERs of 2.4% (both normal), 5.8% (discordant), and 11.3% (both abnormal); p < 0.001. Stress electrocardiogram (ECG) data added incremental value to myocardial perfusion alone but not to combined assessment of perfusion and function. Importantly, inability to achieve 85% of mean predicted heart rate was associated with worse outcomes and was an independent predictor of cardiac events. For patients in whom perfusion, function, and stress ECG response were normal, inability to achieve target heart rate was associated with significantly higher AER (1.5% vs. 3.4%, respectively, p = 0.021).

CONCLUSIONS: In highly selected patients undergoing DSMPI, assessment of perfusion and function is effective in risk stratification. The stress ECG and heart rate response to dobutamine have prognostic value and should be incorporated into image interpretation so as to maximize risk stratification.

Abbreviations and Acronyms   CAD = coronary artery disease   CHF = congestive heart failure   DSMPI = dobutamine stress myocardial perfusion imaging   ECG = electrocardiographic/electrocardiogram   LV = left ventricle or left ventricular   LVEF = left ventricular ejection fraction   MPHR = maximum predicted heart rate   MPI = myocardial perfusion imaging   SDS = summed difference score   SPECT = single-photon emission computed tomography   SRS = summed rest score   SSS = summed stress score   THR = target heart rate

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