Transdermal nitroglycerin patch therapy reduces the extent of exercise-induced myocardial ischemia: results of a double-blind, placebo-controlled trial using quantitative thallium-201 tomography

Medication and ECG Patterns That May Hinder SPECT Myocardial Perfusion Scans

Coronary artery disease (CAD) is the leading cause of death followed by cancer, in men and women. With risk factors being endemic and the increasing costs of healthcare for management and treatment, myocardial perfusion imaging (MPI) finds a central role in risk stratification and prognosis for CAD patients, but it comes with its limitations in that the referring clinician and managing team must be aware of and use at their advantage. This narrative review examines the utility of myocardial perfusion scans in the diagnosis and management of patients with ECG alterations such as atrioventricular block (AVB), and medications including calcium channel blockers (CCB), beta blockers (BB), and nitroglycerin which may impact the interpretation of the exam. The review analyzes the current evidence and provides insights into the limitations, delving into the reasons behind some of the contraindications to MPI.

Myocardial Assessment with Cardiac CT: Ischemic Heart Disease and Beyond

PURPOSE OF REVIEW

The aim of this review is to highlight recent advancements, current trends, and the expanding role for cardiac CT (CCT) in the evaluation of ischemic heart disease, nonischemic cardiomyopathies, and some specific congenital myocardial disease states.

RECENT FINDINGS

CCT is a highly versatile imaging modality for the assessment of numerous cardiovascular disease states. Coronary CT angiography (CCTA) is now a well-established first-line imaging modality for the exclusion of significant coronary artery disease (CAD); however, CCTA has modest positive predictive value and specificity for diagnosing obstructive CAD in addition to limited capability to evaluate myocardial tissue characteristics.

SUMMARY

CTP, when combined with CCTA, presents the potential for full functional and anatomic assessment with a single modality. CCT is a useful adjunct in select patients to both TTE and CMR in the evaluation of ventricular volumes and systolic function. Newer applications, such as dynamic CTP and DECT, are promising diagnostic tools offering the possibility of more quantitative assessment of ischemia. The superior spatial resolution and volumetric acquisition of CCT has an important role in the diagnosis of other nonischemic causes of cardiomyopathies.

The influence of clopidogrel on ischemia diagnosed by myocardial perfusion stress testing

BACKGROUND

Clopidogrel is a platelet adenosine receptor antagonist which can influence coronary vascular tone and thus can potentially interfere with myocardial perfusion imaging. We investigated whether clopidogrel can hamper the diagnosis of ischemia in patients undergoing myocardial perfusion testing.

METHODS

Data from a database of 6349 myocardial perfusion stress tests were analyzed. Using a propensity analysis, patients who were taking clopidogrel were compared with patients not taking clopidogrel for the presence of reversible perfusion defects on myocardial single-photon emission computed tomography scans.

RESULTS

Of the 6349 tests, the stress technique was adenosine in 2713 patients and exercise in 3636. At the time of the stress test, 277 (4.3%) of the patients were taking clopidogrel. The odds ratio (OR) for patients taking clopidogrel to have a reversible perfusion defect was 2.75 (95% confidence interval [CI] 2.09-3.62; P < .01). After adjusting for the propensity to take clopidogrel, the OR was 1.06 (CI 0.76-1.49; P = .73) for patients undergoing adenosine stress tests and 1.60 (CI 0.85-3.00; P = .14) for patients undergoing exercise stress tests.

CONCLUSIONS

We found no evidence that the use of clopidogrel decreases the likelihood of ischemia on adenosine or exercise stress myocardial perfusion scans.

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.

Study of the possible medical and medication explanatory factors of angiographic outcomes in patients with acute ST elevation myocardial infarction undergoing primary percutaneous intervention

Background:

Myocardial blush grade (MBG), thrombolysis in myocardial infarction (TIMI) and corrected TIMI frame count (cTFC) are indices of successful angiographic reperfusion. This study sought to determine the predictors of angiographically successful reperfusion including demographic, clinical and angiographic factors in patients with ST elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI).

Materials and Methods:

A cross-sectional study of patients with a confirmed diagnosis of STEMI undergoing pPCI was designed. Eligible patients referring to a university heart center were enrolled in the study from March 2012 to December 2012. Successful epicardial reperfusion was defned as TIMI flow grade 3 or cTFC<= 28 frames and successful myocardial reperfusion as MBG 2 or 3.

Results:

The study population consisted of 100 patients, including 74 males and 26 females, with mean ± standard deviation age of 58.27 ± 11.60 years. Achieving open microvasculature (MBG 2/3) was positively associated with a history of nitrate intake (P = 0.03) and history of calcium channel blocker (CCB) intake (P = 0.005). Hyperglycemia was inversely associated with achieving a final cTFC ≤ 28 frames (r = −0.32, P = 0.001).

Conclusions:

Our findings suggest that patients with a history of nitrate and CCB intake had a higher likelihood of successful PCI. In addition, patients with a higher blood glucose level on admission may have a reduced rate of reperfusion success. Future studies with a larger sample size are recommended to investigate the significant relationships observed in this study.

Importance of residual myocardial ischemia after intervention in the genesis of cardiovascular events among patients with chronic coronary artery disease

Recent randomized clinical trials support the strategy of ischemia-guided management for patients with stable ischemic heart disease. The application of serial testing to examine the efficacy of therapeutic intervention for ischemia suppression and to document the extent and severity of ischemia provides an important means to guide clinical decision making. This review provides a synopsis of available evidence on serial testing and meaningful thresholds for application of paired rest/stress myocardial perfusion single photon emission computed tomography imaging.

The accuracy of noninvasive stress myocardial imaging for detecting coronary artery disease in clinical practice

BACKGROUND

There is a wide variation in reported accuracy ofnoninvasive stress myocardial imaging as a screening tool for coronary artery disease (CAD). This study was undertaken to determine its current accuracy in a wide spectrum of patients with chest pain syndromes using invasive coronary angiography as the gold standard.

METHODS

The patient population consisted of consecutive patients undergoing coronary angiography in whom noninvasive stress imaging, either nuclear or echocardiographic, was performed within 6 months prior to the angiogram. The specificity, sensitivity, positive and negative predictive values, and diagnostic accuracy for detecting > or =1 lesions with > or =50% diameter coronary stenosis were determined for each modality.

RESULTS

Of the 227 eligible patients, 141 were men and 86 were women; 70% had significant CAD. The diagnostic accuracy overall was 71% and was no different for nuclear or echocardiographic testing. The positive predictive value (86% vs. 52%; P = 0.002) and diagnostic accuracy (83% vs. 51%; P = 0.002) were better in men than in women.

INTERPRETATION

In this study, noninvasive stress imaging lacked the accuracy of a good screening test for significant CAD. This finding was particularly true for women, for whom it was not much better than a coin toss.

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.

Prognostic value of normal exercise 99mTc-sestamibi myocardial tomography in patients with angiographic coronary artery disease

BACKGROUND AND AIM

Previous studies have documented the prognostic value of normal exercise Tl myocardial perfusion imaging in patients with angiographic coronary artery disease (CAD). However, data on exercise Tc-sestamibi myocardial single photon emission computed tomography (SPECT) are scant. Accordingly, the purpose of this study was to investigate the prognostic value of normal exercise Tc-sestamibi SPECT in patients with angiographic CAD.

METHODS

We retrospectively investigated 90 consecutive patients who had a normal exercise Tc-sestamibi myocardial SPECT but angiographic CAD. A group of 69 consecutive patients with both normal exercise Tc-sestamibi myocardial SPECT and coronary arteries were included as control.

RESULTS

During a mean follow-up of 50+/-19 months, a total of three hard cardiac events (non-fatal myocardial infarction) and seven soft cardiac events (late revascularization) were observed. The annual hard cardiac event rate between the two groups was not significantly different (0.6% vs. 0.3%, chi=0.47, P=NS), nevertheless the annual soft cardiac event rate was higher in patients with angiographic CAD (1.9% vs. 0, chi=5.74, P=0.02). Moreover, the annual hard cardiac events rate in patients with angiographic CAD who were treated medically was also not significantly different from that of the control group (0.8% vs. 0.3%, chi=0.77, P=NS). Among patients with angiographic CAD, the annual hard cardiac event rate was not statistically different between those treated medically and those who underwent revascularization (0.8% vs. 0, chi=0.53, P=NS).

CONCLUSIONS

Our data demonstrate that normal exercise Tc-sestamibi myocardial SPECT despite angiographic CAD suggests a low rate of cardiac death or non-fatal myocardial infarction but a relatively high rate of late revascularization during an intermediate term of follow-up.

Detection of hibernate myocardium by 99mTc sestamibi gated SPECT during low-dose dobutamine infusion plus nitrate in patients with first acute myocardial infarction

AIM

To investigate the role of Tc-MIBI gated SPECT imaging following the administration of low-dose dobutamine plus nitrate (LDD+nitrate) in the assessment of left ventricular function and the perfusion of hibernate myocardial tissue.

METHODS

The study group comprised 29 patients diagnosed as having acute myocardial infarction. In the first month post-infarction, Tc-MIBI gated SPECT imaging was performed in all patients at rest-dobutamine stress and LDD+nitrate. Ejection fraction, end diastolic volume (EDV), end systolic volume (ESV), stroke volume, volume, extent score, and reversibility score values were calculated.

RESULTS

The findings of Tc-MIBI gated SPECT imaging following the administration of LDD+nitrate and the rest Tc-MIBI gated SPECT findings revealed that while the levels of ejection fraction (P=0.004) and reversibility score (P=0.000) increased significantly, there was a significant decrease in EDV (P=0.001), ESV (P=0.001), volume (P=0.017), stroke volume (P=0.257) and extent score (P=0.039) values.

CONCLUSION

The use of Tc-MIBI gated SPECT concomitantly with the administration of LDD+nitrate is useful in the determination of myocardial hibernation in patients with left ventricular failure following acute myocardial infarction.

Functional capacity and cardiovascular assessment: submaximal exercise testing and hidden candidates for pharmacologic stress

Submaximal exercise testing is often used to estimate functional capacity in non-athletes, to assess cardiovascular disease in elderly or frail patients, to demonstrate exercise equipment, or to risk-stratify patients after myocardial infarction. However, submaximal exercise testing is not sufficiently sensitive, specific, or predictive to have widespread clinical utility, except in post-myocardial infarction protocols. Many patients for whom submaximal exercise testing is not useful are unable to exercise sufficiently for maximal testing and are referred for imaging with pharmacologic stress. Although some patients who are unable to exercise adequately are easily recognized, many are not. The identification of such patients before they fail a maximal exercise test attempt is beneficial to both the patient and the imaging laboratory.

Sequential single-photon emission computed tomography myocardial perfusion imaging

The utility of stress myocardial perfusion imaging (MPI) for the diagnosis and prognosis of coronary artery disease (CAD) has been firmly established in numerous clinical studies and has become an essential component of clinical practice. Stress MPI is now used regularly to guide initial risk stratification and management of patients with CAD. Because stress MPI provides an assessment of the physiologic significance of CAD, it is a particularly attractive procedure for assessing follow-up risk. Today, sequential stress MPI is being used increasingly to track disease progression, assess follow-up risk, detect restenosis following revascularization, and evaluate the efficacy of aggressive medical therapy and risk-factor modification. By providing serial snapshots of the disease and its impact on perfusion, sequential stress MPI may alter treatment decisions and ultimately improve long-term patient management and outcomes. Use of sequential stress MPI to detect changes in perfusion following surgical or medical therapies is being tested currently in the Clinical Outcomes Using Revascularization and Aggressive Drug Evaluation (COURAGE) and Adenosine Sestamibi Single-Photon Emission Computed Tomography Postinfarction Evaluation (INSPIRE) trials.

Acute beta-blockade reduces the extent and severity of myocardial perfusion defects with dipyridamole Tc-99m sestamibi SPECT imaging

OBJECTIVES

The goal of this study was to examine the effect of acute beta-blockade on dipyridamole Tc-99m sestamibi myocardial perfusion imaging (DMPI).

BACKGROUND

Studies suggest that antianginal drugs may reduce the presence and severity of myocardial perfusion defects with dipyridamole stress. However, there are no data regarding specific drugs.

METHODS

Patients with catheterization-proven coronary artery disease (CAD) were enrolled in this prospective, double-blind, placebo-controlled study and randomly assigned to DMPI after placebo, low-dose metoprolol (up to 10 mg), and high-dose metoprolol (up to 20 mg). Patients underwent one Tc-99m sestamibi study at rest on a separate day. The interval between DMPI studies was <or=14 days. Images were interpreted by three observers blinded to clinical data using a 17-segment, five-point model. For each image, a summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) were calculated (SDS = SSS - SRS). Images with an SSS <4 were considered normal.

RESULTS

Twenty-one patients completed all four Tc-99m sestamibi studies. The sensitivity of DMPI for detection of CAD was 85.7% with placebo versus 71.4% with low- and high-dose metoprolol. In comparison with placebo, the SSS was significantly lower (p < 0.05) with low- and high-dose metoprolol (12.0 +/- 10.1 vs. 8.7 +/- 9.0 and 9.3 +/- 10.6, respectively). The SDS also was significantly lower (8.4 +/- 8.8 with placebo vs. 5.0 +/- 6.7 [p < 0.001] and 5.4 +/- 7.9 [p < 0.01] with low- and high-dose metoprolol, respectively).

CONCLUSIONS

The presence and severity of CAD may be underestimated in patients receiving beta-blocker therapy undergoing dipyridamole stress myocardial perfusion imaging.

A randomized, double-blind, placebo-controlled trial of Ad5FGF-4 gene therapy and its effect on myocardial perfusion in patients with stable angina

OBJECTIVES

The primary objective of this study was to determine whether intracoronary administration of the adenoviral gene for fibroblast growth factor (Ad5FGF-4) can improve myocardial perfusion compared with placebo.

BACKGROUND

Animal studies and observational clinical studies have shown improvement in perfusion of the ischemic myocardium using genes encoding angiogenic growth factors; however, randomized, double-blind data in humans are lacking.

METHODS

We performed a randomized, double-blind, placebo-controlled trial of intracoronary injection of 10(10) adenoviral particles containing a gene encoding fibroblast growth factor (Ad5FGF-4) to determine the effect on myocardial perfusion. Fifty-two patients with stable angina and reversible ischemia comprising >9% of the left ventricle on adenosine single-photon emission computed tomography (SPECT) imaging were randomized to gene therapy (n = 35) or placebo (n = 17). Clinical follow-up was performed, and 51 (98%) patients underwent a second adenosine SPECT scan after 8 weeks.

RESULTS

Overall (n = 52), the mean total perfusion defect size at baseline was 32.4% of the left ventricle, with 20% reversible ischemia and 12.5% scar. At eight weeks, Ad5FGF-4 injection resulted in a significant reduction of ischemic defect size (4.2% absolute, 21% relative; p < 0.001) and placebo-treated patients had no improvement (p = 0.32). Although the change in reversible perfusion defect size between Ad5FGF-4 and placebo was not significant (4.2% vs. 1.6%, p = 0.14), when a single outlier was excluded a significant difference was observed (4.2% vs. 0.8%, p < 0.05). Ad5FGF-4 was well tolerated and did not result in any permanent adverse sequelae.

CONCLUSIONS

Intracoronary injection of Ad5FGF-4 showed an encouraging trend for improved myocardial perfusion; however, further studies of therapeutic angiogenesis with Ad5FGF-4 will be necessary.

The non-invasive assessment of hibernating myocardium in ischaemic cardiomyopathy--a myriad of techniques

Heart failure is placing an ever-increasing burden on society. Many subjects with heart failure and underlying coronary artery disease have a significant amount of akinetic but viable myocardium that is able to contract should myocardial perfusion improve (hibernating myocardium). Non-randomised studies have shown prognostic benefit in subjects with hibernating myocardium undergoing revascularisation. Several non-invasive techniques have been developed to assess the presence or absence of hibernating myocardium. This review will examine the epidemiology and underlying pathogenesis of hibernating myocardium; evaluate the non-invasive techniques for diagnosing hibernating myocardium, and look at therapeutic intervention in subjects with hibernating myocardium.

Risk assessment by myocardial perfusion imaging for coronary revascularization, medical therapy, and noncardiac surgery

Stress myocardial perfusion imaging (MPI) has become an important tool in risk stratification of patients with known coronary artery disease. A normal myocardial perfusion scan has a high negative predictive value and is associated with low annual mortality rate (< 1%). Patients with extensive ischemia (> 20% of the left ventricle), defects in more than 1 coronary vascular territory, transient or persistent left ventricular cavity dilation, and ejection fraction less than 45% have a high annual mortality rate (> 3%). Those patients should undergo coronary revascularization whenever feasible, as the cardiac event rate increases in proportion to the magnitude of the jeopardized myocardium. Stress MPI can be used to demonstrate ischemia in patients with symptoms early after coronary artery bypass surgery (< 5 years) or in those without symptoms late (>/= 5 years) after coronary artery bypass surgery. With respect to patients who underwent percutaneous interventions, stress MPI can help detect in-stent restenosis early after the intervention (3-6 months) or assess the progression of native coronary disease afterward. Since preliminary data suggest that a reduction in the perfusion defect size may translate to a reduction of coronary events, stress MPI can help assess the efficacy of medical management of coronary disease. Finally, stress MPI is indicated for perioperative cardiac risk stratification for noncardiac surgery in patients with intermediate risk predictors (mild angina, prior myocardial infarction or heart failure symptoms, diabetes mellitus, renal insufficiency) and poor functional capacity or in those who undergo high-risk surgery with significant implications in further preoperative management.

Effect of intravenous testosterone on myocardial ischemia in men with coronary artery disease

BACKGROUND

Studies on the effect of estrogen on atherosclerotic coronary artery disease (CAD) risk in women have produced conflicting results. Similar confusion, but fewer data, exists on the effect of testosterone on CAD risk in men.

METHODS

We used 99mTc sestamibi single-photon emission computed tomography (SPECT) myocardial perfusion imaging to examine the acute effect of intravenous testosterone in 32 men (mean age, 69.1 +/- 6.4 years) with provocable myocardial ischemia on standard medical therapy. Patients performed 3 exercise (n = 18) or adenosine (n = 16) stress tests during the infusion of placebo or 2 doses of testosterone designed to increase testosterone 2 or 6 times baseline.

RESULTS

Serum testosterone increased 137 +/- 58% and 488 +/- 113%, and estradiol levels increased 27 +/- 46% and 76 +/- 57%, (P <.001 for all) during the 2 testosterone infusions. There were no differences among the placebo or testosterone groups in peak heart rate, systolic blood pressure, maximal rate pressure product, perfusion imaging scores, or the onset of ST-segment depression.

CONCLUSIONS

Acute testosterone infusion has neither a beneficial nor a deleterious effect on the onset and magnitude of stress-induced myocardial ischemia in men with stable CAD.

Sustained reduction of exercise perfusion defect extent and severity with isosorbide mononitrate (Imdur) as demonstrated by means of technetium 99m sestamibi

BACKGROUND

The impact of long-acting nitrates on the extent and severity of stress-induced myocardial ischemia is not well described, especially after long-term treatment.

METHODS

Forty patients with chronic stable angina and reversible ischemia on an exercise stress myocardial perfusion single photon emission computed tomography (ex-SPECT) were prospectively studied in a 6-week period. At baseline, rest thallium-201/exercise stress technetium 99m sestamibi SPECT was performed, followed by treatment with extended-release isosorbide 5-mononitrate (5-ISMN, Imdur). Follow-up ex-SPECT was performed 5 days and 6 weeks after the initiation of therapy with extended-release 5-ISMN. The exercise treadmill testing (ETT) protocol and exercise duration of the follow-up studies were the same as that of the baseline ETT. Defect extent and severity were analyzed both by means of an automated quantitative method, with CEqual software, and visually, with a 20-segment scoring system (which was also used to derive a summed stress score [SSS]).

RESULTS

In the 6-week study period, significant reductions occurred in both the extent and the severity of exercise-induced ischemia by means of quantitative SPECT (13.8% [P<.0003] and 12.7% [P<.0003], respectively). There was no significant change in these variables between stages 2 (day 5) and 3 (6 weeks), indicating no development of tolerance to the nitrate effect. Similar reductions were noted by means of the visual analysis (SSS reduction of 13.0% [P<.002]) in the entire study period.

CONCLUSIONS

Patients with chronic-stable-angina treated with a long-acting nitrate demonstrate improvement in myocardial perfusion defect extent and severity in an extended period by means of both visual and quantitative analysis of sequential exercise testing to the same rate-pressure product end point.

The role of nuclear cardiology in clinical decision making

This review suggests that the field of nuclear cardiology is alive, well, and thriving, providing relevant information that aids in everyday clinical decision making for nuclear medicine and referring physicians alike. Despite the competition from other modalities, the clinically appropriate applications of nuclear cardiology techniques are likely to increase. The foundation of this optimism is based on the vast amount of data documenting cost-effective clinical applications for diagnosis, risk stratification, and assessing therapy in both chronic and acute coronary artery disease (CAD), the powerful objective quantitative analysis of perfusion and function provided by the technique, and the increasing general availability of the approach.

Silent myocardial ischemia and microalbuminuria in asymptomatic subjects with non-insulin-dependent diabetes mellitus

Microalbuminuria is an increase in urinary albumin not detected by conventional dipstick testing and is present in 20% of patients with non-insulin-dependent diabetes mellitus (NIDDM). Mortality in NIDDM patients with microalbuminuria is 60% at 8 years and is mainly due to cardiovascular disease. Because many deaths occur without warning symptoms, we have compared the prevalence and severity of silent myocardial ischemia in asymptomatic NIDDM patients with and without microalbuminuria. We have performed a cross-sectional, case-control study of asymptomatic NIDDM patients attending hospital diabetes clinics. Forty-three patients with microalbuminuria were matched for age, gender, diabetes duration, and smoking status with 43 normoalbuminuric patients. A symptom-limited exercise stress test was performed and reported blind to patient status. The degree of electrocardiographic ST-segment depression, exercise time, work performed, and maximum heart rate with exercise were recorded. Patients with microalbuminuria had a higher prevalence of ischemic response (>1 mm ST depression) (65% vs 40%, p = 0.016), reduced total exercise time (5 vs 7 minutes, p <0.001), reduced work (6 vs 8 METs, p <0.001), and reduced age-predicted maximum heart rate (94% vs 101%, p = 0.004). In multiple logistic regression, albumin excretion rate was shown to be the strongest independent predictor of ischemic response (p = 0.03). Silent myocardial ischemia is common in asymptomatic NIDDM patients but is more common in those with microalbuminuria. In these subjects, the higher prevalence of ischemic response at low workloads suggests a higher probability of future coronary events, and possibly a higher probability of potentially treatable coronary artery disease.

Tl-201 myocardial perfusion SPECT: role of nitrate-augmented redistribution

PURPOSE

TI-201 myocardial perfusion SPECT is commonly used to assess myocardial perfusion and viability. Nitrate-augmented redistribution with repeated injection facilitates the detection of reversible segments compared with standard redistribution. In this study, we investigated the potential of nitrate augmentation to improve myocardial perfusion and viability assessment without repeated injection and we also compared nitrate-augmented redistribution with delayed redistribution.

METHODS

Eighteen patients underwent a stress-redistribution TI-201 SPECT study. Immediately after redistribution SPECT, each patient was administered 0.6 mg glyceryl trinitrate and nitrate-augmented redistribution SPECT acquired 30 minutes later. Each patient then returned the next day and was injected with a booster dose of TI-201 30 minutes before the delayed redistribution SPECT acquisition. For each SPECT study, the myocardium was divided into 11 segments, and perfusion to each segment was scored on a four-point scale by consensus. An overall cardiac perfusion score was derived by summing the perfusion score for each segment.

RESULTS

Reduced stress perfusion was identified in 150 segments: 23 (15.3%) had improved perfusion after redistribution; 60 (40%) segments had improved perfusion after nitrate-augmented redistribution; 52 (34.7%) segments with reduced stress perfusion had improved perfusion after delayed redistribution. The cardiac perfusion score after stress was 15.9+/-5.5 (means+/-SD). The score increased to 17.4+/-5.4 after redistribution. The perfusion score improved to 19.7+/-5.8 (P < 0.05 versus redistribution) after nitrate augmentation. The cardiac perfusion score, 19.2+/-6.4, did not improve further after delayed redistribution.

CONCLUSIONS

TI-201 SPECT with nitrate-augmented redistribution is as good or better than delayed redistribution with repeated injection for myocardial perfusion and viability assessment. TI-201 SPECT with nitrate-augmented redistribution has significant logistical and economic advantages over traditional delayed redistribution with TI-201 repeated injection.

Intensive medical therapy versus coronary angioplasty for suppression of myocardial ischemia in survivors of acute myocardial infarction: a prospective, randomized pilot study

BACKGROUND

Patients who have inducible ischemia after acute myocardial infarction (AMI) generally undergo coronary angiography with the intent to revascularize. Whether this approach is superior to intensive treatment with anti-ischemic medications is unknown.

METHODS AND RESULTS

We performed a prospective, randomized pilot study comparing intensive medical therapy with coronary angioplasty (PTCA) for suppression of myocardial ischemia in 44 stable survivors of AMI. Myocardial ischemia was quantified with adenosine 201Tl tomography (SPECT) performed 4.5+/-2.9 days after AMI. All patients at baseline had a large total (>/=20%) and ischemic (>/=10%) left ventricular perfusion defect size (PDS). SPECT was repeated at 43+/-26 days after therapy was optimized. The total stress-induced PDS was comparably reduced with medical therapy (from 38+/-13% to 26+/-16%; P<0.0001) and PTCA (from 35+/-12% to 20+/-16%; P<0.0001). The reduction in ischemic PDS was also similar (P=NS) in both groups. Cardiac events occurred in 7 of 44 patients over 12+/-5 months. Patients who remained clinically stable had a greater reduction in ischemic PDS (-13+/-9%) than those who had a recurrent cardiac event (-5+/-7%; P<0.02). Event-free survival was superior in the 24 patients who had a significant (>/=9%) reduction in PDS (96%) compared with those who did not (65%; P=0.009).

CONCLUSIONS

In this small pilot study, intensive medical therapy and PTCA were comparable at suppressing ischemia in stable patients after AMI. Sequential imaging with adenosine SPECT can track changes in PDS after anti-ischemic therapies and thereby predict subsequent outcome. Corroboration of these preliminary findings in a larger cardiac-event trial is warranted.

Design of a randomized, placebo-controlled multicenter trial on the long-term effects of intermittent transdermal nitroglycerin on left ventricular remodeling after acute myocardial infarction. Transdermal Nitroglycerin Investigators Group

Nitrates are widely used in the treatment of patients with ischemic heart disease and in those with angina following acute myocardial infarction. Short-term studies indicate that the administration of nitrates may prevent left ventricular (LV) dilation and infarct expansion. Animal models suggest that prolonged nitroglycerin use after infarction may limit LV remodeling similar to that observed with angiotensin-converting enzyme inhibitors. However, to date there have been no trials evaluating the effects of nitrates on LV volumes in patients surviving acute myocardial infarction. We therefore performed a randomized double-blind, placebo-controlled trial designed to investigate the long-term (6 month) efficacy of intermittent transdermal nitroglycerin patches on LV remodeling in 291 survivors of acute myocardial infarction. Patients were randomized to receive either placebo or a nitroglycerin patch that delivered 0.4, 0.8, or 1.6 mg/hour. Gated radionuclide angiography was used to assess serial changes in LV ejection and cardiac volumes. The baseline characteristics of the study population were similar in all 4 treatment groups. The study protocol and the main design-related issues are described.

Nicotine patch therapy in smoking cessation reduces the extent of exercise-induced myocardial ischemia

OBJECTIVES

We sought to determine the effects of nicotine patch therapy, when used to promote smoking cessation, on myocardial ischemia in patients with coronary artery disease.

BACKGROUND

Nicotine patches substantially increase quit rates among cigarette smokers, but their safety in patients with myocardial ischemia who are attempting to quit smoking is unknown.

METHODS

This is a prospective study using exercise thallium-201 single-photon emission computed tomography (SPECT) to assess serial changes in the total and ischemic myocardial perfusion defect size at baseline while patients were smoking and during treatment with 14- and 21-mg nicotine patches. Entry criteria required that patients 1) smoked > or = 1 pack of cigarettes per day; 2) had known coronary artery disease; and 3) had myocardial ischemia (i.e., > or = 5% reversible perfusion defect) on SPECT. All patients performed symptom-limited treadmill exercise, and the baseline SPECT study served as its own control. We interpreted and computer quantified the SPECT images with no knowledge of the testing sequence.

RESULTS

Thirty-six of the 40 enrolled patients had exercise SPECT at baseline and during treatment with at least 14-mg nicotine patches. These patients had an initial perfusion defect size of 17.5 +/- 10.6% while smoking an average of 31 +/- 11 cigarettes per day for 40 +/- 12 years. A significant reduction in the total perfusion defect size (p < 0.001) was observed from baseline (17.5 +/- 10.6%) to treatment with 14-mg (12.6 +/- 10.1%) and 21-mg (11.8 +/- 9.9%) nicotine patches. This reduction occurred despite an increase in treadmill exercise duration (p < 0.05) and higher serum nicotine levels (p < 0.001). There was a significant correlation between the reduction in defect size and exhaled carbon monoxide levels (p < 0.001) because patients reduced their smoking by approximately 74% during the trial.

CONCLUSIONS

Nicotine patches, when used to promote smoking cessation, significantly reduce the extent of exercise-induced myocardial ischemia as assessed by exercise thallium-201 SPECT.

Achieving sustained improvement in myocardial perfusion: role of isosorbide mononitrate

The efficacy of antianginal agents in the treatment of patients with chronic stable angina has traditionally been evaluated by performance measures, such as the exercise treadmill test (ETT). Although reliable and reproducible, ETT is not a sensitive measure of changes in myocardial ischemia. The effects of antianginal agents on coronary blood flow and myocardial perfusion have been less frequently studied. Angiographic studies have demonstrated that nitrates may operate by preferentially directing blood flow to ischemic regions of the myocardium. These investigations have been limited, however, by the invasive nature of the evaluation. Measurements of regional myocardial perfusion may also be made with noninvasive tests. Both quantitative single-photon emission computed tomography (SPECT) and positron emission tomography (PET) have been employed, but few studies have used these techniques to assess the effects of antianginal drugs (in general) and nitrates (in particular) on changes in reversible myocardial perfusion defects. Studies that have evaluated the direct effects of nitrate treatment on coronary blood flow and myocardial perfusion defects in patients with chronic stable angina are reviewed, and preliminary data from a study of the effects of long-term nitrate treatment on myocardial perfusion are discussed.

Nitroglycerin-augmented 201T1 reinjection enhances detection of reversible myocardial hypoperfusion. A randomized, double-blind, parallel, placebo-controlled trial

BACKGROUND

Recent observations suggest that administration of nitrates before 201Tl reinjection enhances the detection of reversible myocardial hypoperfusion.

METHODS AND RESULTS

Ninety-six patients who underwent exercise-redistribution 201Tl single photon emission computed tomography (SPECT) and had persistent defects at 4-hour redistribution imaging were prospectively randomized into a double-blind protocol in which they received a reinjection of 201Tl (1.0 mCi) 5 minutes after either placebo or 0.8 mg sublingual nitroglycerin administration, followed by repeat SPECT imaging. Of the 69 patients who had coronary angiography, all except one had significant coronary stenoses. The overall extent of perfusion defect and the reversible component assessed by polar maps of the stress-redistribution images were similar in patients who received nitroglycerin or placebo. Among the 66 patients with persistent defects in the redistribution images, 58% of those receiving nitroglycerin showed improved reversibility after reinjection, compared with 33% of patients receiving placebo (P < .05). Among 68 patients with significant coronary stenoses, those who received nitroglycerin and had coronary collateral circulation were more likely to exhibit improved reversibility after reinjection than the remaining patients (50% versus 21%, P < .05). Moreover, the ratio of reversible to total defect in the vascular territories supplied by collaterals was > or = 0.50 after reinjection in 80% of patients who received nitroglycerin (n = 20) compared with 40% of the patients who received placebo (n = 15) (P < .05).

CONCLUSIONS

Nitrate-augmented 201Tl reinjection significantly, albeit modestly, improves detection of defect reversibility, especially in patients with coronary collateral circulation.

Relation between ambulatory electrocardiographic monitoring and myocardial perfusion imaging to detect coronary artery disease and myocardial ischemia: an ACIP ancillary study. The Asymptomatic Cardiac Ischemia Pilot (ACIP) Investigators

OBJECTIVES

This study sought to explore the relation between markers of ischemia detected by ambulatory electrocardiographic (AECG) monitoring and stress myocardial perfusion single-photon emission computed tomography (SPECT).

BACKGROUND

Stress myocardial SPECT and AECG monitoring are both utilized in evaluating patients with coronary artery disease. However, information is limited regarding the relation between the presence and extent of ischemia as detected by these two modalities.

METHODS

This was an ancillary study of the Asymptomatic Cardiac Ischemia Pilot (ACIP) trial. One hundred six patients with previous coronary angiography underwent AECG monitoring and stress SPECT within a close temporal time period. The frequency and duration of ischemia as assessed by AECG monitoring and the total and ischemic stress-induced myocardial perfusion defect sizes as assessed by SPECT were quantified in separate core laboratories. Multivariate logistic regression and linear regression analysis were used to determine associations between AECG and SPECT abnormalities with regard to angiographic, demographic and treadmill exercise variables.

RESULTS

Seventy-four percent of patients with significant (> or = 50%) coronary artery stenosis had SPECT abnormalities, whereas 61% had ischemia by AECG monitoring. The most important predictors of SPECT abnormalities were severity (p < 0.001) of coronary artery stenosis, followed by total exercise duration (p = 0.016) and patient age (p = 0.04). The only predictor of AECG abnormalities was the presence of ST segment depression on the initial exercise treadmill test (p = 0.021). Only a 50% concordance for normalcy or abnormalcy was observed between the SPECT and AECG results, and no relation was observed between the frequency or duration of AECG ischemia and the quantified total or ischemic myocardial perfusion defect size as assessed by SPECT.

CONCLUSIONS

Ischemia as detected by AECG monitoring does not correlate with the presence and extent of ischemia as quantified by stress SPECT. Because these techniques appear to detect different pathophysiologic manifestations of ischemia, they may be complementary in more fully defining the functional significance of coronary artery disease and, in particular, which patients are at highest risk for adverse cardiac events.

Beneficial actions of nitrates in cardiovascular disease

Nitroglycerin and the long-acting nitrates have been used in cardiovascular medicine for >100 years. Nitrates are widely utilized for the various anginal syndromes and are also used in congestive heart failure and patients with left ventricular dysfunction. The potential mechanisms for relief of myocardial ischemia with nitrates are multiple. The nitrovasodilators are a related group of drugs that result in the formation of nitric oxide (NO) within vascular smooth muscle cells. NO stimulates the enzyme guanylate cyclase, which results in increases in cyclic guanosine monophosphate and vasodilation. In the presence of atherosclerosis, endothelial dysfunction is ubiquitous and associated with decreased NO availability, probably due to increased destruction of NO by free radical anions. Nitrovasodilators, including the nitrates, supply exogenous NO to the vascular wall and improve the vasodilator state. When nitrates are administered, endothelial-dependent stimuli cause relaxation rather than constriction in the setting of endothelial dysfunction. Nitrates also have antiplatelet effects, and recent evidence confirms that these drugs decrease platelet aggregation and thrombosis formation. This may play an important role in the therapy of acute unstable myocardial ischemia, including unstable angina and myocardial infarction. Nitrate hemodynamic effects have been long known. They are primarily modulated through a decrease in myocardial work that results from smaller cardiac chambers operating with lower systolic and diastolic pressures. These changes are caused by a redistribution of the circulating blood volume away from the heart to the venous capacitance system, with a fall in venous return to the heart. The afterload or arterial effects of nitrates are also useful in decreasing myocardial oxygen consumption. Considerable evidence confirms a variety of mechanisms whereby nitrates increase coronary blood flow, including epicardial coronary artery dilation, stenosis enlargement, enhanced collateral size and flow, improvement of endothelial dysfunction, and prevention or reversal of coronary artery vasoconstriction. These effects help increase nutrient coronary blood flow to zones of myocardial ischemia. Recent data with the nitroglycerin patch confirm that myocardial ischemia is decreased after nitrate administration. Nitroprusside, another nitrovasodilator, is a commonly used intravenous agent for lowering arterial pressure and left ventricular filling pressure. This drug is highly effective for the treatment of acute or severe hypertension and congestive heart failure. However, there are data suggesting that nitroprusside may be deleterious in the presence of acute myocardial ischemia, perhaps by shunting blood away from zones of jeopardized myocardial blood flow. Therefore, nitroprusside cannot be recommended to treat myocardial ischemia; intravenous nitroglycerin should be used in this context.

Nitrate-augmented myocardial imaging for assessment of myocardial viability

201Tl myocardial perfusion imaging is presently done by several possible strategies. Stress/delayed redistribution, stress/redistribution/reinjection, and rest/redistribution imaging can be useful in the clinical assessment of myocardial viability. Unfortunately, the extent of myocardial viability may still be underestimated even by 201Tl reinjection imaging, compared with 18F-fluorodeoxyglucose positron emission tomography. 99mTc-labeled sestamibi imaging provides results similar to those of 201Tl imaging in the detection of coronary artery disease, but several previous studies suggest that stress/rest 99mTc-labeled sestamibi imaging significantly underestimates myocardial viability. Recently it has been reported that the administration of nitrates, before 201Tl reinjection, improves detection of defect reversibility. Several studies also suggested that administration of nitrates before the injection of 99mTc-labeled sestamibi significantly improved detection of reversibility with this agent, whereas additional studies showed further that this combination improves the predictive accuracy for recovery of left ventricular function and perfusion after coronary revascularization, compared with a standard rest 99mTc-labeled sestamibi study. Nitrate administration before the injection of 201Tl and 99mTc-labeled sestamibi may thus be a potentially attractive alternative for the evaluation of myocardial viability. Although the available results are encouraging, further studies are needed to evaluate the clinical value of 201Tl and 99mTc-labeled sestamibi imaging, in combination with nitrates, for predicting recovery of left ventricular dysfunction.

High reproducibility of myocardial perfusion defects in patients undergoing serial exercise thallium-201 tomography

The purpose of this study was to define the reproducibility of sequential quantitative exercise thallium-201 tomography. This was an ancillary study of a randomized, double-blind, placebo-controlled trial evaluating the short-term efficacy of transdermal nitroglycerin patches in stable patients with angiographic coronary artery disease and no prior myocardial infarction. All 18 patients had a baseline tomographic perfusion defect involving > or = 5% of the left ventricle after treadmill exercise. At a minimum of 3 days (mean 6.1 +/- 1.8) after double-blind randomization to placebo, exercise thallium-201 tomography was repeated (study 2) using the same exercise protocol as in the baseline study (study 1). No significant differences in exercise parameters were observed from studies 1 to 2. Seventeen of 18 patients (94%) had an abnormal repeat exercise perfusion scan and 96% of initially abnormal vascular territories remained abnormal. The mean tomographic perfusion defect size was not significantly different from studies 1 (17.4 +/- 13.3%) to 2 (16.6 +/- 15.3%), nor were the components defined as scar and ischemia. A > or = 10% change in total perfusion defect size in an individual patient defined the 95% confidence interval for exceeding the variability of the tomographic technique. Quantitative exercise thallium-201 tomography is highly reproducible and can be used to accurately interpret temporal changes in myocardial perfusion in individual patients.