Author + information
- Narendra C. Bhalodkar, MD* ( and )
- Steve Blum, PhD
- ↵*Division of Cardiology, Bronx Lebanon Hospital, 1650 Grand Concourse, Bronx, New York 10457
We read the paper by Chang et al. (1) and accompanying editorial (2) with great interest. The insightful single-center study addresses safety of normal stress-only myocardial perfusion imaging (MPI). However, it raises some concerns.
Careful examination of the paper suggests a conundrum. Annualized crude death rate for the stress-only MPI group is significantly lower than stress and rest MPI. However, after adjustment for clinical factors associated with mortality (Table 3 of Chang et al. ) this difference in crude mortality, which is lower in the stress-only group, disappears. This, despite the fact that the stress-only group was significantly less likely to have these risk factors associated with higher mortality, both in aggregate (Table 1 of Chang et al. ) (mean number of risk factors: 1.33 ± 1.1 vs. 1.57 ± 1.1, p < 0.001) and for each individual risk factor. The fact that the stress-only group was older by 1.1 years cannot possibly, it seems, explain this effect of adjustment.
The study, although large, is retrospective and has all of the limitations of retrospective studies (3,4).
The stress-only study was performed in patients weighing <200 lbs. Hence, the study's findings may be applicable to this subset of patients only, and furthermore, with the growing epidemic of obesity, its applicability will be further reduced. Chang et al. (1) did not indicate what percentage of these patients needed to undergo additional rest MPI. Additionally, height and/or body mass index were not considered in deciding stress-only protocol. With the same 200 lbs weight, a patient whose height is 60 inches would have a body mass index of 39.1 kg/m2, whereas for a patient whose height is 72 inches, it would be 27.1 kg/m2. The former patient (short and stubby) may present a significant challenge for stress-only MPI.
The end point was all-cause mortality derived from Social Security Death Index. Chang et al. (1) did not mention how many patients did not have a social security number and hence were lost to follow-up.
We do not have incidence of unstable angina pectoris, nonfatal myocardial infarctions, hospitalizations, revascularizations, and information regarding quality of life, all of which add to morbidity and health care cost.
Chang et al. (1) also projected cardiac mortality on the assumption of data applicable to a general population, which may be inaccurate, as study patients have a higher cardiac risk profile than the population at large.
Among patients with a low (<5%) Bayesian likelihood of coronary artery disease and normal MPI transient ischemic dilation, incidence is reported to be 4.1%. Moreover, transient ischemic dilation may be the only scan abnormality in patients with severe multivessel disease producing balanced ischemia that can be missed on stress-only MPI. These patients will be clinically missed and not receive appropriate management.
The findings of this study (1) need to be validated in a large, randomized, prospective, multicenter study.
- American College of Cardiology Foundation
- Chang S.M.,
- Nabi F.,
- Xu J.,
- Raza U.,
- Mahmarian J.J.
- Iskandrian A.E.
- Hess D.R.