Serial changes on quantitative myocardial perfusion SPECT in patients undergoing revascularization or conservative therapy

Impact on cardiovascular outcome of coronary revascularization-induced changes in ischemic perfusion defect and myocardial flow reserve

PURPOSE

We evaluated the impact on cardiovascular outcome of coronary revascularization-induced changes in ischemic total perfusion defect (ITPD) and myocardial flow reserve (MFR) as assessed by 82Rb positron emission tomography (PET)/computed tomography (CT) imaging.

METHODS

The study included 102 patients referred to 82Rb PET/CT myocardial perfusion imaging before and after coronary revascularization. All patients were followed for the occurrence of cardiovascular events (cardiac death, nonfatal myocardial infarction, repeated revascularization, and heart failure) after the second imaging study.

RESULTS

During a median follow-up of 20 months, 21 events occurred. The clinical characteristics were comparable between patients with and without events. In the overall study population, after revascularization, there was a significant reduction (P < 0.001) of ITPD, while hyperemic myocardial blood flow (MBF) (P < 0.01) and MFR (P < 0.05) significantly improved. Event rate was higher in patients with ITPD (P < 0.005) or MFR (P < 0.001) worsening compared to those with unchanged or improved ITPD or MFR. At Cox univariable analysis, ITPD and MFR worsening resulted in predictors of events (both P < 0.05). Patients with worsening of both ITPD and MFR had the worst event-free survival (log-rank 32.9, P for trend < 0.001).

CONCLUSIONS

In patients with stable CAD, worsening of ITPD and MFR after revascularization procedures is associated with higher risk of cardiovascular events. Follow-up MPI with 82Rb PET/CT may improve risk stratification in patients submitted to coronary revascularization.

Proposal for a Display Method for Myocardial Single Photon Emission Computed Tomography Based on Left Ventricular Volume

Bull's eye view for the display of myocardial single-photon emission computed tomography (SPECT) 3-D perfusion maps does not reflect left ventricular (LV) volume, an important parameter. We created and evaluated a myocardial SPECT display method that reflects the LV volume.Using Digital Imaging and Communications in Medicine data, short-axis slices from the apex to the base were reconstructed and interpolated into 0.5-mm thickness. We obtained the radial lengths at 1° intervals throughout 360°, and calculated the length of the LV long axis and half circumference (1/2 circ). Myocardial perfusion was displayed as 2 ellipsoidal developments that exhibited the left anterior descending coronary artery (LAD) and non-LAD regions. We created a system that can display these processes on a personal computer. Myocardial SPECT data from 526 individuals without heart disease were analyzed. The long axis and 1/2 circ were compared with the body size, LV end-diastolic diameter (LVDd) obtained by echocardiography, and the end-diastolic volume (EDV) obtained by electrocardiogram-gated SPECT analysis. The 1/2 circle correlated with the LVDd and EDV. The images obtained allowed a diagnosis comparable to that made using the conventional coordinate display system.The new myocardial display reflects ischemia and LV volume within a single image, which cannot be achieved with conventional SPECT image display. Additional studies of this display system are required to allow its application to patients with heart disease.

Effect of changes in perfusion defect size during serial regadenoson myocardial perfusion imaging on cardiovascular outcomes in high-risk patients

BACKGROUND

The prognostic value of single-photon emission computed tomography myocardial perfusion imaging (MPI) is well established. There is a paucity of data on the prognostic value of changes in perfusion defect size (PDS) on serial MPIs.

METHODS

From the MPI database at the University of Alabama at Birmingham, consecutive patients who underwent two regadenoson stress MPIs between July 2008 and March 2013 were identified. The MPIs were analyzed side-by-side using an automated software program for presence and change in PDS. Improvement in PDS was defined as a reduction ≥5% of left ventricle. A drop in left ventricular ejection fraction (LVEF) was defined as a decrease ≥5%. The primary outcome was a composite of death, myocardial infarction (MI), and coronary revascularization (CR).

RESULTS

There were 698 patients (61 ± 11 years, 53% male, 48% diabetes, 25% prior MI, 49% prior CR) who underwent two regadenoson MPIs within 16 ± 9 months for clinical indications. The primary outcome occurred in 167 (24%) patients (8% death, 9% MI, 15% CR) during 24 ± 16 months of follow-up after the second MPI. The MPIs were normal in both studies in 399 (57%, Group 1), showed improvement in 94 (14%, Group 2, PDS 15% ± 16% vs 28% ± 18%, P < .001) and no change or worsening in 205 patients (29%, Group 3, 28% ± 17% vs 20% ± 17%, P < .001). The best outcomes were seen in Group 1 and the worst in Group 3 (log-rank P < .001). Similar trends were seen for the components of the primary outcome (P = .04 for death, P < .001 for MI, P < .001 for CR). In a Cox-regression model that adjusted for baseline factors including PDS and LVEF on initial MPI, the hazard ratios for primary outcome were 2.0 (P = .02) and 3.9 (P < .001) for Groups 2 and 3 compared to Group 1, respectively. In addition, an LVEF drop ≥5% was independently associated with the primary outcome (HR 1.5, P = .01).

CONCLUSION

Changes in PDS and LVEF on serial MPIs provide incremental prognostic information to initial and follow-up MPI findings. Lack of improvement or an increase in PDS and a drop in LVEF identify high-risk patients.

Angiogenic gene therapy for refractory angina

INTRODUCTION

Stimulation of coronary collateral vessel growth by therapeutic angiogenesis (TA) offers an alternative treatment option for patients with refractory angina. Several TA modalities, including delivery to the heart of angiogenic growth factors (proteins or genes) and cells have been tested in clinical trials in the past two decades, but so far none of them resulted in significant therapeutic efficacy in large scale studies. This review attempts to identify the main obstacles hindering clinical success and recommends measures to overcome them in the future.

AREAS COVERED

After stating the medical need and rational for TA, and listing and briefly discussing past and current TA clinical trials, three main areas of obstacles are described: conceptual questions, technical limitations and clinical design uncertainties. Based on scientific and technical advances and lessons learned in past clinical trials, potential solutions to overcome some of these obstacles are proposed.

EXPERT OPINION

Several success criteria are identified, which apply to any TA approach of choice. It is emphasized, that each of these criteria needs to be met in future clinical trials to have a chance of therapeutic success.

Ischaemia change with revascularisation versus medical therapy in reduced ejection fraction

Objective

Nuclear imaging data demonstrate that revascularisation leads to favourable effects on ischaemia burden and improved outcomes compared with medical therapy (MT). In patients with heart failure (HF), the effects of MT versus revascularisation on ischaemia change and its independent prognostic significance requires investigation.

Methods

From the Duke Databank, we performed a retrospective analysis of 278 consecutive patients with coronary artery disease (CAD) and ejection fraction (EF) ≤40%, who underwent 2 serial myocardial perfusion scans between 1993 and 2009. Ischaemia change was calculated for patients undergoing MT alone, or revascularisation. Cox proportional hazards regression modelling was used to identify factors associated with death/myocardial infarction (MI).

Results

The magnitude of ischeamia reduction was greater with revascularisation than with MT alone (median change of −6% vs 0%, p<0.001). With revascularisation, more patients experienced ≥5% ischaemia reduction compared with MT (52% vs 25%, p<0.01) and a similar percentage experienced ≥5% ischaemia worsening (13% vs 18%, p=0.37). After risk adjustment, ≥5% ischaemia worsening was associated with decreased death/MI (HR=0.58; 95% CI 0.36 to 0.96).

Conclusions

In patients with HF with CAD, revascularisation improves long-term ischaemia burden compared with MT. Ischaemia worsening on nuclear imaging was associated with reduced risk of death/MI, potentially related to development of ischaemic viable myocardium as opposed to scar tissue.

Serial myocardial perfusion imaging: defining a significant change and targeting management decisions

Myocardial perfusion imaging (MPI) with gated single-photon emission tomography provides important information on the extent and severity of myocardial perfusion abnormalities, including myocardial ischemia. The availability of software for automated quantitative assessment of myocardial perfusion in an objective and more reproducible manner than visual assessment has allowed MPI to be particularly effective in serial evaluation. Serial testing using MPI is widely used in guiding patient care despite the lack of well-defined appropriateness use criteria. This should not be surprising because ischemic heart disease is a life-long malady subject to dynamic changes throughout its natural course and particularly following man-made interventions that may improve or worsen the disease process, such as medical therapy and coronary revascularization. Serial MPI has filled an important clinical gap by providing crucial information for managing patients with changes in clinical presentations or in anticipation of such changes in patients with stable symptoms. In the research arena, serial MPI has been widely applied in randomized controlled trials to study the impact of various medical and interventional therapies on myocardial perfusion, as well as the relative merits of new imaging procedures (hardware and/or software), radiotracers, and stressor agents. Serial testing, however, unlike initial or 1-time testing, has more stringent requirements and is subject to variability because of technical, procedural, interpretational, and biological factors. The intrinsic variability of MPI becomes important in interpreting serial tests in order to define a true change in a given patient and to guide clinical decision making. The purpose of this first comprehensive review on this subject is to illustrate where serial MPI may be useful clinically and in research studies, and to highlight strategies for addressing the various issues that are unique to serial testing in order to derive more valid and robust data from the serial scans.

Assessing the prognostic implications of myocardial perfusion studies: identification of patients at risk vs patients who may benefit from intervention?

Stress myocardial perfusion imaging (MPI) has a well-established role in improving risk stratification. Recent analyses, compared with older data, suggest that the yield of stress MPI has decreased. In part, this trend relates to testing patients with heterogeneous, but improved, risk factor modification. In this setting, positron emission tomography with myocardial flow reserve enhances risk stratification as it reflects the end result of atherosclerosis. Recent studies have also emphasized the clinical impact of incremental risk stratification by assessing net reclassification improvement (NRI). Previous retrospective studies have favored an ischemic threshold to select patients that benefit from revascularization, but this finding has not been corroborated in randomized trials. However, no large randomized trial has directly tested a strategy of revascularization for patients with at least a moderate amount of ischemia at risk. Unfortunately, even when faced with a significantly abnormal MPI result, subsequent action is too often absent.

Ischemia change in stable coronary artery disease is an independent predictor of death and myocardial infarction

OBJECTIVES

The aim of this study was to evaluate the independent prognostic significance of ischemia change in stable coronary artery disease (CAD).

BACKGROUND

Recent randomized trials in stable CAD have suggested that revascularization does not improve outcomes compared with optimal medical therapy (MT). In contrast, the nuclear substudy of the COURAGE (Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation) trial found that revascularization led to greater ischemia reduction and suggested that this may be associated with improved unadjusted outcomes. Thus, the effects of MT versus revascularization on ischemia change and its independent prognostic significance requires further investigation.

METHODS

From the Duke Cardiovascular Disease and Nuclear Cardiology Databanks, 1,425 consecutive patients with angiographically documented CAD who underwent 2 serial myocardial perfusion single-photon emission computed tomography scans were identified. Ischemia change was calculated for patients undergoing MT alone, percutaneous coronary intervention, or coronary artery bypass grafting. Patients were followed for a median of 5.8 years after the second myocardial perfusion scan. Cox proportional hazards regression modeling was used to identify factors independently associated with the primary outcome of death or myocardial infarction (MI). Formal risk reclassification analyses were conducted to assess whether the addition of ischemia change to traditional predictors resulted in improved risk classification for death or MI.

RESULTS

More MT patients (15.6%) developed ≥5% ischemia worsening compared with those undergoing percutaneous coronary intervention (6.2%) or coronary artery bypass grafting (6.7%) (p < 0.001). After adjustment for established predictors, ≥5% ischemia worsening remained a significant independent predictor of death or MI (hazard ratio: 1.634; p = 0.0019) irrespective of treatment arm. Inclusion of ≥5% ischemia worsening in this model resulted in significant improvement in risk classification (net reclassification improvement: 4.6%, p = 0.0056) and model discrimination (integrated discrimination improvement: 0.0062, p = 0.0057).

CONCLUSIONS

In stable CAD, ischemia worsening is an independent predictor of death or MI, resulting in significantly improved risk reclassification when added to previously known predictors.

The Timing and Impact of Follow-Up Studies After Normal Stress Single-Photon Emission Computed Tomography Sestamibi Studies

Background—

The purpose of this study was to determine the prevalence and timing of routine follow-up single-photon emission computed tomography (SPECT) studies after a normal stress SPECT scan compared with the patient's warranty period (ie, time to 1% risk of death or myocardial infarction).

Methods and Results—

We identified patients at Mayo Clinic Rochester who had normal stress SPECT scans in 2002. Of 2354 patients without prior coronary artery disease, 309 (13%) had routine follow-up scans. The time to routine follow-up was a median of 2.1 years (25th percentile, 1.2 years; 75th percentile, 3.6 years). This interval was a median of 45% of the warranty period. Of the 309 patients, only 9 (3%) underwent subsequent coronary angiography, without revascularization. Of 656 patients with prior coronary artery disease, 171 (26%) had routine follow-up scans. The time to routine follow-up was a median of 1.6 years (25th percentile, 1.0 years; 75th percentile, 2.7 years). This interval was a median of 164% of the warranty period. Of the 171 patients, only 7 (4%) underwent coronary angiography, without revascularization.

Conclusions—

In patients without prior coronary artery disease, routine follow-up SPECT scans are performed infrequently but well before the end of the patient's warranty period. Routine follow-up scans are performed more commonly in patients with prior coronary artery disease but generally after the end of the warranty period. Routine follow-up SPECT scans have minimal impact on referral to catheterization or revascularization.

Optimal medical therapy with or without percutaneous coronary intervention to reduce ischemic burden: results from the Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) trial nuclear substudy

BACKGROUND

Extent and severity of myocardial ischemia are determinants of risk for patients with coronary artery disease, and ischemia reduction is an important therapeutic goal. The Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) nuclear substudy compared the effectiveness of percutaneous coronary intervention (PCI) for ischemia reduction added to optimal medical therapy (OMT) with the use of myocardial perfusion single photon emission computed tomography (MPS).

METHODS AND RESULTS

Of the 2287 COURAGE patients, 314 were enrolled in this substudy of serial rest/stress MPS performed before treatment and 6 to 18 months (mean=374+/-50 days) after randomization using paired exercise (n=84) or vasodilator stress (n=230). A blinded core laboratory analyzed quantitative MPS measures of percent ischemic myocardium. Moderate to severe ischemia encumbered > or = 10% myocardium. The primary end point was > or = 5% reduction in ischemic myocardium at follow-up. Treatment groups had similar baseline characteristics. At follow-up, the reduction in ischemic myocardium was greater with PCI+OMT (-2.7%; 95% confidence interval, -1.7%, -3.8%) than with OMT (-0.5%; 95% confidence interval, -1.6%, 0.6%; P<0.0001). More PCI+OMT patients exhibited significant ischemia reduction (33% versus 19%; P=0.0004), especially patients with moderate to severe pretreatment ischemia (78% versus 52%; P=0.007). Patients with ischemia reduction had lower unadjusted risk for death or myocardial infarction (P=0.037 [risk-adjusted P=0.26]), particularly if baseline ischemia was moderate to severe (P=0.001 [risk-adjusted P=0.08]). Death or myocardial infarction rates ranged from 0% to 39% for patients with no residual ischemia to > or = 10% residual ischemia on follow-up MPS (P=0.002 [risk-adjusted P=0.09]).

CONCLUSIONS

In COURAGE patients who underwent serial MPS, adding PCI to OMT resulted in greater reduction in ischemia compared with OMT alone. Our findings suggest a treatment target of > or = 5% ischemia reduction with OMT with or without coronary revascularization.

Gated SPECT imaging to detect changes in myocardial blood flow during progressive coronary occlusion

BACKGROUND

The ability to track dynamic changes in myocardial blood flow (MBF) and wall motion with serial gated perfusion imaging may be a limiting factor in assessing new therapies. The purpose of this study was to determine whether gated Tc-99 m sestamibi (MIBI) SPECT imaging can track small changes in MBF in a model of progressive ischemia.

METHODS

Eight pigs (20 kg) underwent lateral thoracotomy for placement of an ameroid constrictor on the left circumflex coronary artery (LCX) and indwelling femoral and left atrial catheters for serial microsphere determinations of absolute MBF. Animals underwent concurrent left atrial microsphere and Tc-99 m sestamibi (0.3 mCi/Kg IV) injections at weekly intervals over 6 weeks per animal. Gated SPECT imaging was acquired for each injection using high resolution collimation and standard processing. The animals were sacrificed on day 42. Mean signal intensity (SI) from regions of interest (ROI) corresponding to control and ischemic MBF by microspheres was measured for three SPECT short-axis images. Mean contrast ratio (MCR) was calculated from the ratio of ischemic to control SI per slice. Regional wall motion (RWM) from gated images was scored 1-5 using a 16 segment model and a score index (RWMI) was calculated.

RESULTS

MBF decreased progressively (27% below resting values [P < 0.0001]) but with a clear and significant partial recovery by day 42 (13% improvement from peak ischemia, [P < 0.01]). SPECT perfusion and gated RWM closely paralleled the dynamic pattern of MBF caused by the ameroid constrictor. SPECT MCR decreased 21% from baseline scans in the LCX territory (P < 0.0001) and improved 11% from peak ischemia (P < 0.01) while the gated RWMI (1.0 at baseline) peaked at 1.36 and improved to 1.13 by day 42.

CONCLUSION

Gated SPECT-a technique readily available-tracks dynamic changes in MBF closely with both perfusion and RWM. For trials of new therapies for the alleviation of chronic ischemia, these findings have direct implications for measuring efficacy.

To what degree is amelioration of angina following coronary revascularization associated with improvement in myocardial perfusion?

OBJECTIVE

To examine the association between changes in chest pain and changes in perfusion following revascularization as assessed by clinical evaluation and myocardial perfusion imaging (MPI) in patients with stable angina.

DESIGN

In a prospective series of 380 patients (58.8 +/- 8.8 years) referred to angiography because of known or suspected stable angina, changes in chest discomfort and changes in perfusion after 2 years were assessed in 144 patients, who underwent revascularization, and 236, who did not. The decision to treat invasively was made without knowledge of the result of MPI.

RESULTS

In revascularized patients, the presence of typical/atypical angina was reduced from 93% to 36% and the improvement was associated with improvement in perfusion. A small improvement in perfusion induced a high frequency of change from angina to no pain, whereas a further reduction caused little extra change. In non-revascularized patients the change in chest discomfort was not related to changes in perfusion, which were rarely present.

CONCLUSION

Alleviation of chest discomfort 2 years after revascularization is associated with improvements in perfusion. This association appeared to be an all-or-nothing phenomenon. Non-revascularized patients also exhibited improvements in chest discomfort despite insignificant changes in perfusion.

Noninvasive monitoring of medical therapy

An extensive literature base documents the substantial incremental prognostic value of nuclear cardiology compared with information provided by risk factors, clinical history, electrocardiographic stress testing results, and coronary arteriography. A smaller, well-established and growing literature addresses the unique potential of nuclear cardiology to assess therapeutic response of ischemic heart disease to lifestyle and medical therapies in individual patients. General guidelines focus on management of individual risk factors based on large studies, but may not reflect the optimum treatment strategy for an individual patient. The central rationale for noninvasive serial monitoring is to optimize the effectiveness and timing of lifestyle, medical, and revascularization therapies to minimize coronary event risk. Ideally, this monitoring of therapy should be early in the management of coronary artery disease (CAD) and guide the need for more intensive therapeutics. The application of technical advances in serial monitoring has the potential to revolutionize the way we diagnose and prevent CAD, even in asymptomatic patients. The potential long-term cost effectiveness of positron emission tomography and single-photon emission CT myocardial perfusion scintigraphy in detecting and monitoring treatment of CAD offers great promise for reducing coronary events in known or suspected ischemic heart disease.

Detecting changes in serial myocardial perfusion SPECT: a simulation study

BACKGROUND

New algorithms were evaluated for their efficacy in detecting and quantifying serial changes in myocardial perfusion from single photon emission computed tomography (SPECT).

METHODS AND RESULTS

We generated 72 simulations with various left ventricular positions, sizes, count rates, and perfusion defect severities using the nonuniform rational B-splines (NURBs)-based CArdiac Torso (NCAT) phantom. Images were automatically aligned by use of both full linear and rigid transformations and quantified for perfusion by use of the CEqual program. Changes within a given perfusion defect were compared by use of a Student t test before and after registration. Registration approaches were compared by use of receiver operating characteristic analysis. Changes of 5% were not detected well in single patients with or without alignment. Changes of 10% and 15% could be detected with false-positive rates of 15% and 10%, respectively, in single studies if alignment was performed before perfusion analysis. Alignment also reduced the number of studies necessary to demonstrate a significant perfusion change (P < .05) in groups of patients by about half.

CONCLUSION

Comparison of mean uptake by t values in SPECT perfusion defects can be used to detect 10% and greater differences in serial perfusion studies of single patients. Image alignment is necessary to optimize automatic detection of perfusion changes in both single patients and groups of patients.

Evidence for left ventricular remodeling after percutaneous coronary intervention

BACKGROUND

Post-stress ejection fraction (EF), end-diastolic (EDV) and end-systolic (ESV) volumes by gated myocardial perfusion SPECT (MPS) are well validated, reproducible and of prognostic significance. However, little is known about the impact of percutaneous coronary intervention (PCI) on left ventricular volumes and remodeling.

METHODS

Thirty-eight patients who underwent MPS before and 6 months after PCI were evaluated. MPS were interpreted deriving summed stress (SSS), rest (SRS) and difference (SDS = SSS-SRS; extent of ischemia) scores. EF, EDV and ESV were generated by QGS trade mark. Pre-PCI MPS were compared to post-PCI MPS.

RESULTS

Single vessel disease was present in 63% of patients. PCI of one vessel was performed in 82% of patients. After 6 months, SSS (10.6 +/- 6.3 vs. 2.8 +/- 4.3, p < 0.001) and SDS (8.2 +/- 5.6 vs. 1.4 +/- 2.3, p < 0.001) had improved; however, EF did not change significantly (55 +/- 10 vs. 57 +/- 13, p = ns). Still, EDV (105 +/- 25 ml vs. 96 +/- 25 ml, p = 0.006) and ESV (49 +/- 19 ml vs. 41 +/- 18 ml, p = 0.001) were significantly reduced.

CONCLUSION

Results of MPS documented the beneficial effect of PCI on symptoms and extent of ischemia. In addition, the findings showed a significant decrease in ESV and EDV after PCI as compared to pre-PCI findings which points to a positive effect on left ventricular remodeling even in the absence of significant changes in EF.

Value of low-dose dobutamine addition to routine dual isotope gated SPECT myocardial imaging in patients with healed myocardial infarction or abnormal wall thickening by echocardiogram

There is overlap in myocardial viability detection by thallium-201 uptake and contractile reserve (CR) using low-dose dobutamine (LDD). The dual isotope protocol was modified in this study by acquiring thallium-201 images using LDD to enhance viability detection in addition to coronary flow reserve assessment. One hundred twenty-four patients with coronary disease underwent gated single-photon emission computed tomographic thallium-201 imaging at rest with LDD (10 microg/kg/min) during acquisition followed by stress technetium-99m sestamibi myocardial perfusion (MP) imaging with dobutamine, adenosine, or treadmill exercise. F-18-fluorodeoxyglucose (FDG) positron emission tomography was obtained in 41 patients. Myocardial perfusion (MP) imaging was divided into normal, fixed, and ischemic segments, and subclassified by wall motion and/or thickening changes between 1-hour poststress and LDD into normal, fixed, or improved dysfunctional segments (CR present). Mean left ventricular ejection fraction was 39% at 1 hour after stress and 47% with LDD (p <0.001). In dysfunctional myocardium, CR was significantly higher (p <0.001) in ischemic (233 of 368) and fixed segments (150 of 335) than in normal MP segments (43 of 220). Combined MP and CR analysis showed higher accuracy and negative predictive value in identifying FDG-viable myocardium than either method alone, whereas a high positive predictive value was maintained, similar to both markers. Quantitative analysis showed significant increased wall motion and thickening with LDD compared with 1 hour after stress, which was highest in ischemic segments and lowest in fixed segments. Thus, LDD dual isotope is a practical protocol that improves viability detection by simultaneous MP and CR analysis in addition to coronary flow reserve assessment in 1 study. Moreover, it requires no extra imaging time or radioactivity than the routine protocol.

Myocardial perfusion scintigraphy: the evidence

This review summarises the evidence for the role of myocardial perfusion scintigraphy (MPS) in patients with known or suspected coronary artery disease. It is the product of a consensus conference organised by the British Cardiac Society, the British Nuclear Cardiology Society and the British Nuclear Medicine Society and is endorsed by the Royal College of Physicians of London and the Royal College of Radiologists. It was used to inform the UK National Institute of Clinical Excellence in their appraisal of MPS in patients with chest pain and myocardial infarction. MPS is a well-established, non-invasive imaging technique with a large body of evidence to support its effectiveness in the diagnosis and management of angina and myocardial infarction. It is more accurate than the exercise ECG in detecting myocardial ischaemia and it is the single most powerful technique for predicting future coronary events. The high diagnostic accuracy of MPS allows reliable risk stratification and guides the selection of patients for further interventions, such as revascularisation. This in turn allows more appropriate utilisation of resources, with the potential for both improved clinical outcomes and greater cost-effectiveness. Evidence from modelling and observational studies supports the enhanced cost-effectiveness associated with MPS use. In patients presenting with stable or acute chest pain, strategies of investigation involving MPS are more cost-effective than those not using the technique. MPS also has particular advantages over alternative techniques in the management of a number of patient subgroups, including women, the elderly and those with diabetes, and its use will have a favourable impact on cost-effectiveness in these groups. MPS is already an integral part of many clinical guidelines for the investigation and management of angina and myocardial infarction. However, the technique is underutilised in the UK, as judged by the inappropriately long waiting times and by comparison with the numbers of revascularisations and coronary angiograms performed. Furthermore, MPS activity levels in this country fall far short of those in comparable European countries, with about half as many scans being undertaken per year. Currently, the number of MPS studies performed annually in the UK is 1,200/million population/year. We estimate the real need to be 4,000/million/year. The current average waiting time is 20 weeks and we recommend that clinically appropriate upper limits of waiting time are 6 weeks for routine studies and 1 week for urgent studies.

Prospective serial evaluation of myocardial perfusion and lipids during the first six months of pravastatin therapy: coronary artery disease regression single photon emission computed tomography monitoring trial

OBJECTIVES

This study was designed to assess prospectively changes in serum lipid profile and myocardial perfusion with serial radionuclide single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) during the first six months of pravastatin therapy.

BACKGROUND

Morbid coronary events occur despite statin therapy and lipid-lowering in patients with coronary artery disease (CAD). A reliable strategy to identify responders with effective treatment from nonresponders on statin therapy before clinical events is needed.

METHODS

Rest and stress SPECT MPI and lipids were assessed serially in 25 patients (36% women) with CAD and dyslipidemia during the first six months of pravastatin therapy.

RESULTS

Total cholesterol, low-density lipoprotein cholesterol, and triglycerides declined (26%, 32%, and 30%, respectively) by six weeks and remained reduced at six months. Mean stress perfusion defect (summed stress score [SSS]) was severe (13.3 +/- 6.0) at baseline, showed no change at six weeks, and improved significantly at six months (10.3 +/- 7.3, p < 0.01). The six-month study SSS improved in 11 (48%) patients, was unchanged in 10 (43%) patients, and worsened in 2 (9%) patients. Changes in lipid levels did not reliably predict changes in myocardial perfusion at six weeks or six months in this small pilot study.

CONCLUSIONS

Serial SPECT MPI demonstrated improved stress myocardial perfusion in 48% of patients treated for six months with pravastatin. Time course of improved myocardial perfusion during pravastatin therapy is delayed compared to lipids. Direction and magnitude of changes in the myocardial perfusion vary and do not correlate closely with improvements in lipids.