Normal Myocardial Perfusion Scan And Prognosis

What Is The Prognostic Significance Of A Normal Myocardial Perfusion Scan?

2003. Determinants of risk and its temporal variation in patients with normal stress myocardial perfusion scans: What is the warranty period of a normal scan? Hachamovitch R, Hayes S, Friedman JD, Cohen I, Shaw LJ, Germano G, Berman DS. J Am Coll Cardiol. 2003 Apr 16;41(8):1329-40. UCLA and the Atlanta Cardiovascular Research Institute. Link to the full study in PDF format.

7,376 consecutive patients with normal exercise or adenosine MPS.
Excluded patients: (1) Patients with valvular heart disease or primary cardiomyopathy, (2) patients who underwent SPECT within 90 days after percutaneous transluminal coronary angioplasty (PTCA). Also: Patients with previous MI or revascularization were considered to have known CAD, but they were NOT excluded from the study (N = 1280).
Among those not known to have CAD, pre-test probability of CAD was 0.22 ± 0.41.
Among those known to have CAD, pre-test probability of ischemia was 0.38 ± 0.35.
Follow-up: 22 ± 6 months, follow-up 96% complete.
For the entire cohort, annualized risk of “hard” events (= death or non-fatal myocardial infarction) = 0.6% per year (1/167 per year). This breaks down further to 0.34% per year risk of death (1/294 per year) and 0.26% per year risk of non-fatal MI (1/385 per year).
[The annualized risk of “hard” events (=death or non-fatal myocardial infarction) for the 7,376 with normal myocardial perfusion scans was 1/6 that of the 8,091 patients with abnormal myocardial perfusion scans (who were eliminated from the study).]
Among the 7,376 patients in the study, predictors of higher risk for hard events included the following: (1) Known history of CAD; (2) Need for adenosine stress instead of treadmill stress; (3) Male gender; (4) Achievement of <80% of age-predicted maximum heart rate in those undergoing treadmill stress; (5) Age; (6) Diabetes mellitus, especially in women.
Among the 1280 patients with known coronary artery disease with normal myocardial perfusion scans, risk of hard events was higher in the second year of follow-up than in the first year of follow-up. This trend was not seen in those with no known coronary artery disease.
The highest risk subgroups had a maximal event rate of 1.4% to 1.8%/year. That is, a 1% per year risk of death (1/100 per year) and a 0.8% per year risk on non-fatal MI (1/125 per year). It is understood that when this highest risk subset is removed from the analysis, the remaining patients will have a substantially lower risk than when the highest risk subset is included.

2007. The Prognostic Value of Normal Exercise Myocardial Perfusion Imaging and Exercise Echocardiography: A Meta-Analysis. Louise D. Metz, MD, Mary Beattie, MD, Robert Hom, MD, Rita F. Redberg, MD, MSc, Deborah Grady, MD, MPHand Kirsten E. Fleischmann, MD, MPH. J Am Coll Cardiol, 2007; 49:227-237. NYU and UCSF. Link to the Abstract.

Only patients who underwent exercise (not pharmacologic stress) were included in the meta-analysis.
8008 patients were included in the meta-analysis.
The negative predictive value (NPV) for MI and cardiac death was 98.8% (95% confidence interval [CI] 98.5 to 99.0) over 36 months of follow-up for MPI, and 98.4% (95% CI 97.9 to 98.9) over 33 months for echocardiography.
The corresponding annualized event rates were 0.45% per year for MPI (total death + MI risk = 1/222 per year) and 0.54% per year for echocardiography (total death + MI risk = 1/185 per year). [Comment: These annualized event rates are slightly lower than those found in the Hachamovitch study which is discussed above. This is exactly the expected pattern, since inability to undergo exercise stress was a potent risk factor for death or MI in the Hachamovitch study.]
These annualized event rates are both similar to a normal age-matched population, who carry a rate of <1% per year. Thus, both noninvasive imaging modalities accurately identify low-risk patients.

2007. Clinical Outcomes After Both Coronary Calcium Scanning and Exercise Myocardial Perfusion Scintigraphy. Alan R, Berman DS, et al. J Am Coll Cardiol 2007 49: 1352-1361. Link to the Abstract.

We assessed the frequency of cardiac death and myocardial infarction over a mean follow-up of 32 ±16 months in 1,153 patients undergoing both CAC scanning and MPS. Results were compared with those from a referent cohort of 9,308 patients who had earlier undergone MPS only.
The frequency of myocardial ischemia rose with increasing CAC scores (p < 0.001), but ischemia was present in only 64 patients. Among the 1,089 nonischemic patients, of which only 3 (0.3%) underwent early revascularization, the annualized cardiac event rate was <1% in all CAC subgroups, including those with CAC scores >1,000. Among patients with nonischemic MPS studies, high CAC scores do not confer an increased risk for cardiac events.
Thus, although patients with high CAC scores may be considered for intensive medical therapy to prevent future coronary artery disease events, a normal MPS study in such patients suggests no need for more aggressive interventions.

2007. Long-Term Prognosis Associated With Coronary Calcification: Observations From a Registry of 25,253 Patients. Matthew J. Budoff, MD, Daniel S. Berman, MD, et al. J Am Coll Cardiol, 2007; 49:1860-1870.
Link to the Abstract.

The frequency of CAC scores was 44%, 14%, 20%, 13%, 6%, and 4% for scores of 0, 1 to 10, 11 to 100, 101 to 400, 401 to 1,000, and >1,000, respectively.
During a mean follow-up of 6.8 ± 3 years, the death rate was 2% (510 deaths). The CAC was an independent predictor of mortality in a multivariable model controlling for age, gender, ethnicity, and cardiac risk factors (model chi-square = 2,017, p < 0.0001).
The addition of CAC to traditional risk factors increased the concordance index significantly (0.61 for risk factors vs. 0.81 for the CAC score, p < 0.0001). Risk-adjusted relative risk ratios for CAC were 2.2-, 4.5-, 6.4-, 9.2-, 10.4-, and 12.5-fold for scores of 11 to 100, 101 to 299, 300 to 399, 400 to 699, 700 to 999, and >1,000, respectively (p < 0.0001), when compared with a score of 0.
Ten-year survival (after adjustment for risk factors, including age) was 99.4% for a CAC score of 0 and worsened to 87.8% for a score of >1,000 (p < 0.0001).

2007. Assessment by Coronary Computed Tomographic Angiography of Individuals Undergoing Invasive Coronary Angiography (ACCURACY). Min J., et al. In press.

64-slice CT coronary angiography was carried out in a real-world group of 232 unselected chest-pain patients referred for invasive coronary angiography from 16 sites. No patients were excluded due to high coronary artery calcification score, body mass index or vessel size. All patients underwent CT coronary angiography and invasive coronary angiography. Findings: Positive predictive value of the test was mediocre (33% to 62%), but negative predictive value was superb (97% to 99%). However, less than 15% of study patients had obstructive coronary artery disease (Comment: Is this referral pattern widespread?) and this low incidence of disease substantially influenced outcomes. Clearly, this study needs to be repeated in a larger and more varied patient group, but it appears to provide guidance for the moment. The arrival of even better CT scanners will doubtless render this study obsolete in the near future. Click here to read the news report.