Diagnostic accuracy of low-dose myocardial perfusion imaging in a real-world setting

BACKGROUND

This large-scale study analyzes factors affecting the diagnostic accuracy of low-dose myocardial perfusion imaging and correlation with coronary angiography in a real-world practice.

METHODS

We compared data extracted from routine reports of (i) low-dose [99mTc]sestamibi stress-MPI performed with no attenuation correction and predominantly exercise stress testing and (ii) the corresponding coronary angiography.

RESULTS

We considered 1070 pairs of coronary angiography/stress-MPI results reported by 11 physicians. Mean MPI effective dose was 4.5 ± 2.1 mSv. The extent of MPI-ischemia was predictive of >70% but not 50%-70% coronary stenoses. A positive test was associated with a sensitivity of 74.7% (413/553) and a specificity of 53.2% (275/517) for >70% stenosis detection. Positive predictive values were lower in patients with left bundle branch block or pacemakers (LBBB/PM) (45.6% vs 64.7%, P = .006) and markedly higher for patients with MPI-ischemia ≥3 segments or associated with ST-segment depression (75.0% (165/220)) as compared to those with <3 segments MPI-ischemia, MPI-infarction or isolated ST-segment depression (57% (248.0/435), P < .001). Negative predictive values were lower for patients with previous coronary artery disease (CAD) history (58.3%), male (61.0%), and elderly patients (59.6%) (vs 72.1%, 79.2%, and 72.4%, respectively, all P < .05).

CONCLUSIONS

Routine results from low-dose stress-MPI, predominantly associated with exercise stress testing and uncorrected for attenuation, correlate with real-world coronary angiography results. However, this correlation is lower than that achieved with conventional study designs and affected by the definition of significant CAD and context variables (LBBB/PM, CAD history, sex, and age). Better consideration of these interacting factors could improve patient monitoring.

Assessment of the routine reporting of very low-dose exercise-first myocardial perfusion SPECT from a large-scale real-world cohort and correlation with the subsequent reporting of coronary stenosis at angiography

PURPOSE

Our study assesses the routine reporting of exercise ischemia using very low-dose exercise-first myocardial perfusion SPECT in a large number of patients and under real-life conditions, by evaluating correlations with the subsequent routine reporting of coronary stenosis by angiography and with factors that predict ischemia.

METHODS

Data from 13,126 routine exercise MPI reports, from 11,952 patients (31% women), using very low doses of sestamibi and a high-sensitivity cardiac CZT camera, were extracted to assess the reporting of significant MPI-ischemia (> 1 left ventricular segment), to determine the MPI normalcy rate in a group with < 5% pretest probability of coronary artery disease (CAD) (n = 378), and to assess the ability of MPI to predict a > 50% coronary stenosis in patients with available coronary angiography reports in the 3 months after the MPI (n = 713).

RESULTS

The median effective patient dose was 2.51 [IQR: 1.00-4.71] mSv. The normalcy rate was 98%, and the MPI-ischemia rate was independently predicted by a known CAD, the male gender, obesity, and a < 50% LV ejection fraction, ranging from 29.5% with all these risk factors represented to 1.5% when there were no risk factors. A > 50% coronary stenosis was significantly predicted by MPI-ischemia, less significantly for mild (odds ratio [95% confidence interval]: 1.61 [1.26-1.96]) than for moderate-to-severe MPI-ischemia (4.05 [3.53-4.57]) and was also impacted by having a known CAD (2.17 [1.83-2.51]), by a submaximal exercise test (1.48 [1.15-1.81]) and being ≥ 65 years of age (1.43 [1.11-1.76]).

CONCLUSION

Ischemia detected using a very low-dose exercise-first MPI protocol in a large-scale clinical cohort and under real-life routine conditions is a highly significant predictor for the subsequent reporting of coronary stenosis, although this prediction is enhanced by other variables. This weakly irradiating approach is amenable to being repeated at shorter time intervals, in target patient groups with a high probability of MPI-ischemia.

Myocardial Ischemia in the Management of Chronic Coronary Artery Disease: Past and Present

For many years, stress-induced myocardial ischemia has been considered important in the management of chronic coronary artery disease. Early evidence focused on the exercise ECG and the Duke treadmill score. In the 1970s, randomized clinical trials, which compared coronary artery bypass surgery to medical therapy, enrolled patients who were very different from contemporary practice and had inconsistent results. Surgery appeared to be of greatest benefit in high-risk patients defined by anatomy (such as left main disease) or stress-induced ischemia. However, randomized clinical trials of revascularization versus contemporary medical therapy over the past 20 years have been surprisingly negative. Nuclear cardiology substudies from these trials reported inconsistent results. Two observational studies from a single-center provided the best evidence for the use of stress-induced ischemia to identify patients who were most likely to benefit from revascularization. The recently completed ISCHEMIA trial (International Study of Comparative Health Effectiveness With Medical and Invasive Approaches) was designed to test the hypothesis that revascularization would improve outcomes in patients with moderate-severe ischemia on stress testing. Unfortunately, 14.2% of the randomized patients had either mild or no ischemia on core lab review. Nearly one-quarter of the patients were randomized on the basis of an exercise ECG without imaging. The negative results of the trial reflect the long-term population decline in coronary artery disease and abnormal stress tests, as well as improvements in patient outcome due to optimal medical therapy. Topics requiring further research are presented. The implications of the trial for the use of both stress imaging and coronary computed tomography angiography in clinical practice are examined.

Epidemiology and pathophysiologic insights of coronary atherosclerosis relevant for contemporary non-invasive imaging

In the past few years significant changes have taken place in the diagnostic and therapeutic approach to patients with coronary artery disease (CAD) and/or ischemic heart disease (IHD). New discoveries about the development and progression of coronary atherosclerosis have changed the clinical landscape. At the same time a marked decrease in cardiovascular (CV) mortality and CAD incidence have been observed in many Countries but particularly in the most industrialized ones. This fall has been also observed in the incidence of stroke, sudden death, myocardial ischemia, myocardial infarction (MI), and prevalence of CAD. As a consequence, an increasing number of patients with chest pain exhibits non-significant stenosis at both invasive and non-invasive coronary angiography and the rate of coronary vessels revascularizations has greatly reduced. Coronary atherosclerosis and its characteristics have shown to be both diagnostic and therapeutic targets beyond obstructive CAD. The decreased prevalence of CAD in the general population has modified the pre-test probability (PTP) of disease. In this landscape the conventional stress imaging tests appear to have limited accuracy making the diagnosis of obstructive CAD very challenging. These diagnostic tests have been introduced and tested in a population with a much higher probability of disease and therefore the contemporary accuracy of these old tests appear much lower than in the past. In addition, in the past few years the relevance of the traditional ischemia guided coronary intervention strategy has been questioned. Given the low CV events granted by an optimal medical therapy in CAD the major attention has been directed on detecting coronary atherosclerosis. The earlier the better. At the same time, a growing number of data from clinical studies have shown a significant prognostic role for non-obstructive CAD and coronary atherosclerosis. All these facts have shifted the clinicians' attention from the functional evaluation of the coronary circulation to the anatomic burden of disease.

Coronary Disease Surveillance in the Community: Angiography and Revascularization

Background Temporal declines in cardiac stress tests results, coronary revascularization, and cardiovascular mortality have suggested a decline in the population burden of coronary disease until the 2000s. However, recent data indicate these favorable trends could be ending. We aimed to assess the evolution of the population burden of coronary disease in the community by examining trends in angiography and revascularization. Methods and Results We analyzed age- and sex-adjusted trends from all coronary angiographic diagnostic procedures and revascularizations performed in Olmsted County, MN from 2000 to 2018. A total of 12 981 invasive angiograms were performed among 9049 individuals (64% men; 55% aged ≥65 years). Adjusted angiography rates decreased by 30% (95% CI, 25%-34%) between 2000 and 2009 and leveled off thereafter. Including computed tomography, angiography uncovered an increase in angiography use in recent years (risk ratio=1.15 [95% CI, 1.07-1.23] for 2018 versus 2014) and a decline in the prevalence of anatomic CAD from 2000 to 2018. CAD severity declined substantially from 2000 to 2009, followed by a plateau. Among 6570 revascularizations (72% men; 57% aged ≥65 years), 77% were percutaneous coronary interventions and 23% coronary artery bypass graft surgeries. The adjusted revascularization rates declined by 34% (95% CI, 27%-39%) from 2000 to 2009, followed by a plateau (risk ratio=1.10 [95% CI, 1.00-1.22]). Conclusions Between 2000 and 2018 in the community, coronary angiography use declined initially, leveled off, and then increased. Trends in CAD severity and revascularization use decreased then plateaued. The most recent trends are concerning as they suggest the burden of coronary disease is no longer declining. This warrants reinvigorated primary prevention and population surveillance.