A novel clinically relevant segmentation method and corresponding maximal ischemia score to risk-stratify patients undergoing myocardial perfusion scintigraphy

Comparative analysis between myocardial perfusion reserve and maximal ischemia score at single photon emission computed tomography with new-generation cadmium-zinc-telluride cameras

BACKGROUND

Whether estimates of myocardial perfusion reserve (MPR) stemming from new-generation cadmium-zinc-telluride (CZT) cameras are accurate remains unclear.

METHODS

We queried our institutional database for patients undergoing MPR with CZT cameras. The primary goal was appraising the incremental diagnostic yield of MPR on top or at odds of maximal ischemia score (MIS).

RESULTS

A total of 66 subjects were included. When distinguishing patients according to normal vs abnormal MPR (cut-off 2.1 mL/min/g) and normal vs abnormal MIS, 4 groups could be identified: 12 (18.1%) individuals with normal MPR and MIS, 12 (18.1%) with normal MPR and abnormal MIS, 16 (24.2%) with abnormal MPR and normal MIS, and 26 (39.4%) with abnormal MPR and MIS. MIS was significantly associated with several baseline features, whereas MPR did not. There was no significant association between MPR and MIS, nor with regional perfusion. Clinical outcomes were uncommon and not significantly associated with MPR or MIS, whereas angiographically significant coronary artery disease (CAD) was associated solely with MIS (P < 0.05), and not with MPR.

CONCLUSIONS

There is limited agreement between CZT-derived MPR and baseline risk, perfusion and angiography results. Whether such discrepancies may still prove incrementally beneficial for the diagnosis or prognosis of CAD remains unclear.

Hybrid anatomo-functional imaging of coronary artery disease: Beneficial irrespective of its core components

Coronary artery disease (CAD) is the most common and important cause of ischemic heart disease, with major implications on global morbidity and mortality. Non-invasive testing is crucial in the diagnostic and prognostic work-up of patients with or at risk of CAD, and also to guide decision making in terms of pharmacologic and revascularization therapy. The traditional paradigm is to view anatomic (i.e., coronary computed tomography) and functional imaging (e.g., myocardial perfusion scintigraphy) tests as opposing alternatives. Such approach is too reductionist and does not capitalize on the strengths of each type of test while risking to overlook the inherent limitations. The combination of anatomic and functional tests in a logic of hybrid imaging holds the promise of overcoming the limitations inherent to anatomic and functional testing, enabling more accurate diagnosis, prognosis, and guidance for revascularization in patients with CAD.

Prognostic accuracy of myocardial perfusion imaging in octogenarians

BACKGROUND

Myocardial perfusion imaging (MPI) has an established role in the work-up of coronary artery disease (CAD), but its comparative accuracy is debated in elderly patients. We examined a large administrative database to appraise the performance of MPI in octogenarians.

METHODS

Our institutional database was queried for patients undergoing MPI without recent coronary revascularization or myocardial infarction (MI). We compared baseline, procedural, diagnostic, and prognostic features in patients aged < 80 vs ≥ 80 years with bivariate and propensity-adjusted analyses.

RESULTS

From 13,254 patients, 12,737 (96.1%) were < 80 years old and 517 (3.9%) ≥ 80 years. Octogenarians were less likely to undergo exercise testing, had more severe and extensive myocardial ischemia (all P < 0.001), whereas CAD was more prevalent and diffuse in them (P = 0.012), and major adverse cardiac events more common during follow-up (P = 0.009). Diagnostic accuracy of MPI was similar or higher in octogenarians than in younger patients (e.g., sensitivity for three-vessel disease 92% in octogenarians vs 91% in younger patients), as was prognostic accuracy. Using propensity-matched analyses, MPI again yielded satisfactory prognostic accuracy in octogenarians.

CONCLUSIONS

Use of MPI in octogenarians is associated with similar or better prognostic accuracy than in younger subjects.

Impact of specific coronary lesions on regional ischemia at single photon emission computed tomography

AIMS

Prior studies using stress myocardial perfusion imaging (MPI), which examined the association between obstructive epicardial coronary disease and presence of myocardial ischemia did not provide a detailed assessment on a regional level. We examined this relationship in a large population of patients in whom the coronary anatomy was defined by invasive coronary angiography.

METHODS

We retrospectively extracted details on individuals undergoing MPI with single photon emission computed tomography (SPECT) who had coronary angiography within 12 months. A 17-segment model for native coronary anatomy and a 7-region model for myocardial perfusion were used with a dedicated matching algorithm.

RESULTS

A total of 2564 patients were included, yielding a total of 6279 stenoses matched with 17 948 myocardial regions. From such a cohort, 151 (5.9%) patients had normal perfusion, 1878 (73.2%) had myocardial ischemia (reversible defects), 260 (10.1%) had myocardial necrosis (scar or fixed defects), and 275 (10.7%) had ischemia and necrosis. At per-patient analysis, significant angiographic disease was more common in the ischemic group (prevalence between 69.6 and 80.0%) than other groups. At per-region analysis, abnormal perfusion in the coronary-specific regions varied depending on location of stenosis; it was 96% for left main disease, 81% for proximal left anterior descending disease, 85% for proximal left circumflex disease, and 82% for proximal right coronary artery disease and <60% for posterior descending artery disease.

CONCLUSION

The correlation between significant coronary stenosis and presence of corresponding regional perfusion abnormality depends on the location of the lesion and the corresponding myocardial region.

Assessment of the fate of myocardial necrosis by serial myocardial perfusion imaging

BACKGROUND

Myocardial necrosis after myocardial infarction (MI) is common; extent and severity are however variable. The pattern is recognized by myocardial perfusion imaging (MPI) as fixed perfusion defects (FPD). The fate of such FPD is not well appraised. This study addressed this important issue in a large number of patients undergoing serial MPI in relation to type of intervening therapy.

METHODS

Patients with prior MI or MPI-evidence of myocardial necrosis undergoing serial MPI without intervening acute coronary syndromes were included. The fate of necrosis by MPI on per-patient and per-region analysis was analyzed, factoring also the impact of intervening coronary revascularization (CR).

RESULTS

A total of 3691 patients with 25,837 regions were identified, including 1413 (38.3%) subjects with 3358 (13.0%) regions exhibiting necrosis. Serial MPI after 29±21 months confirmed the persistent presence of myocardial necrosis FPD in the vast majority of patients and regions (86%); the consistency was even higher in the presence of moderate or severe necrosis (99%). Neither type nor site of CR significantly impacted on the presence and extent of myocardial necrosis at multivariable analysis.

CONCLUSIONS

The finding of myocardial necrosis by MPI remains highly consistent over time, and is not significantly altered by CR.

Temporal Trends in the Prevalence, Severity, and Localization of Myocardial Ischemia and Necrosis at Myocardial Perfusion Imaging After Myocardial Infarction

The definition, presentation, and management of myocardial infarction (MI) have changed substantially in the last decade. Whether these changes have impacted on the presence, severity, and localization of necrosis at myocardial perfusion imaging (MPI) has not been appraised to date. Subjects undergoing MPI and reporting a history of clinical MI were shortlisted. We focused on the presence, severity, and localization of necrosis at MPI with a retrospective single-center analysis. A total of 10,476 patients were included, distinguishing 5 groups according to the period in which myocardial perfusion scintigraphy had been performed (2004 to 2005, 2006 to 2007, 2008 to 2009, 2010 to 2011, 2012 to 2013). Trend analysis showed over time a significant worsening in baseline features (e.g., age, diabetes mellitus, and Q waves at electrocardiogram), whereas medical therapy and revascularization were offered with increasing frequency. Over the years, there was also a lower prevalence of normal MPI (from 16.8% to 13.6%) and ischemic MPI (from 35.6% to 32.8%), and a higher prevalence of ischemic and necrotic MPI (from 12.0% to 12.7%) or solely necrotic MPI (from 35.7% to 40.9%, p <0.001). Yet the prevalence of severe ischemia decreased over time from 11.4% to 2.0%, with a similar trend for moderate ischemia (from 15.9% to 11.8%, p <0.001). Similarly sobering results were wound for the prevalence of severe necrosis (from 19.8% to 8.2%) and moderate necrosis (from 8.5% to 7.8%, p = 0.028). These trends were largely confirmed at regional level and after propensity score matching. In conclusion, the outlook of stable patients with previous MI has substantially improved in the last decade, with a decrease in the severity of residual myocardial ischemia and necrosis, despite an apparent worsening in baseline features.

Impact of coronary revascularization vs medical therapy on ischemia among stable patients with or suspected coronary artery disease undergoing serial myocardial perfusion scintigraphy

BACKGROUND

Randomized trials have challenged the role of revascularization in stable coronary artery disease. We aimed to appraise the impact of revascularization on ischemia in patients undergoing serial myocardial perfusion scintigraphy (MPS).

METHODS

We queried our institutional database for stable subjects undergoing serial MPS and appraised the impact of revascularization on changes in ischemia.

RESULTS

A total of 3631 patients were included: 967 (27%) undergoing revascularization and 2664 (73%) receiving medical therapy only. Patients treated with revascularization had a significantly lower burden of myocardial ischemia at follow-up (odds ratio = 0.577 [95% confidence interval 0.483-0.689] vs medical therapy, P < .001). Among all those having moderate or severe ischemia at baseline, revascularization was associated with a follow-up prevalence of 80% for no, minimal, or mild ischemia and 20% for moderate or severe ischemia, vs 43% and 57% for medical therapy (P < .001). Even at multivariable analysis and propensity-adjusted, and propensity-matched analyses, revascularization was associated with a significantly lower prevalence of moderate or severe ischemia at follow-up (respectively P < .001, P = .001, and P = .042).

CONCLUSIONS

Revascularization appears superior to medical therapy in reducing ischemic burden and normalizing myocardial perfusion among subjects with moderate or severe ischemia at baseline.

Prognostic impact of location and extent of vessel-related ischemia at myocardial perfusion scintigraphy in patients with or at risk for coronary artery disease

BACKGROUND

Myocardial perfusion scintigraphy (MPS) has an established diagnostic and prognostic role in patients with or at risk for coronary artery disease, with ischemia severity and extent having already been identified as key predictors. Whether this is affected by the location of myocardial ischemia is uncertain. We aimed at comparing the prognostic outlook of patients undergoing MPS according to the site of ischemia.

METHODS

Our institutional database was queried for subjects undergoing MPS, without myocardial necrosis or recent revascularization. We focused on the prognostic impact of location of vessel-related ischemia (VRI) at MPS, distinguishing four mutually exclusive groups: single-VRI involving left anterior descending (LAD), single-VRI not involving LAD, multi-VRI involving LAD, and multi-VRI not involving LAD. The primary outcome was the long-term (>1 year) rate of death or myocardial infarction (D/MI).

RESULTS

A total of 13,254 patients were included. Moderate or severe VRI occurred in 2,627 (20%) patients. Clinical outcomes were significantly different among the groups of patients with moderate or severe VRI, including death, cardiac death, non-fatal myocardial infarction or their composites (overall P < .001). Specifically, and excluding subjects undergoing revascularization as first follow-up event, D/MI occurred in 8.4% of patients with single-VRI involving LAD, 5.5% of subjects with single-VRI not involving LAD, 16.5% of those with multi-VRI involving LAD, and 7.3% of patients with multi-VRI not involving LAD (overall P < .001). Even at incremental multivariable Cox proportional analysis, hierarchical VRI was independently associated with an increased risk of D/MI [hazard ratio = 1.17 (1.04-1.08) for each class increment, P = .010].

CONCLUSIONS

Location and extent of myocardial ischemia at MPS according to the VRI concept have a hierarchical predictive impact, with multi-VRI involving LAD being significantly and independently more prognostically ominous than other types of VRI.

Review of cardiovascular imaging in The Journal of Nuclear Cardiology in 2014: Part 2 of 2: Myocardial perfusion imaging

In this new feature of The Journal of Nuclear Cardiology we will summarize key articles that were published in the Journal in the previous year. In the first article of this 2-part series we concentrated on publications dealing with cardiac positron emission tomography, computed tomography, and neuronal imaging. This review will focus on myocardial perfusion imaging summarizing advances in the field including in diagnosis, prognosis, appropriateness, and safety of testing.

Time to and risk of cardiac events after myocardial perfusion scintigraphy

BACKGROUND

The burden of cardiovascular disease is increasing, yet it remains difficult to focus preventive strategies on populations at highest absolute and relative risks. We compared absolute and relative cardiovascular event counts, plus time to first event, among patients undergoing myocardial perfusion scintigraphy (MPS).

METHODS AND RESULTS

Our database was queried to identify subjects without myocardial necrosis or recent revascularization, focusing on cardiac death (CD) or myocardial infarction (MI). A total of 13,254 patients were included, 5436 (41%) without, and 7818 (59%) with ischemia. After 32±21 months, subjects without ischemia, compared to those with ischemia, had lower absolute (16 vs 75 events, 18% vs 82%, p<0.001) and relative (0.3% vs 1.3%, p<0.001) risk of CD. Similar findings were obtained for MI (52 vs 81 events, 39% vs 61%, p<0.001, with corresponding rates of 1.0% vs 1.4%, p<0.001, respectively). Medical therapy appeared associated with fewer outcomes in those without ischemia, with the opposite occurring for subjects with ischemia (p<0.001). Median times to event ranged between 13 and 25 months in patients without ischemia vs 2 and 14 months in those with ischemia (p<0.001 for all comparisons). Multivariable-adjusted and propensity matched analyses confirmed the independent prognostic role of myocardial ischemia and, apparently, revascularization.

CONCLUSION

Most fatal and non-fatal cardiac events appear to occur in patients with evidence of myocardial ischemia at MPS, especially those with moderate or severe ischemia not receiving revascularization during follow-up.