High-frequency QRS analysis to supplement ST evaluation in exercise stress electrocardiography: Incremental diagnostic accuracy and net reclassification.

Background: Exercise stress electrocardiography (ECG) alone is underutilized in part due to poor diagnostic accuracy. High-frequency QRS analysis (HF-QRS) is a novel tool to supplement ST evaluation during stress ECG. We compared the diagnostic accuracy and net reclassification of HF-QRS analysis compared with ST evaluation for substantial myocardial ischemia by exercise SPECT myocardial perfusion imaging (MPI).

Prevalence and predictors of ischemia and outcomes in outpatients with diabetes mellitus referred for single-photon emission computed tomography myocardial perfusion imaging.

Background- The prevalence of ischemia and its prediction of events are unclear in outpatients with diabetes mellitus in the modern era of intensive medical management. We sought to identify the prevalence of ischemia, subsequent cardiac events, and impact of sex, stress type, and symptom status on these findings in a cohort of stable outpatients with diabetes mellitus referred for single-photon emission computed tomography myocardial perfusion imaging (MPI). Methods and Results- The study cohort included 575 consecutive outpatients with diabetes mellitus who underwent quantitative, gated single-photon emission computed tomography MPI.

The prevalence and predictive accuracy of quantitatively defined transient ischemic dilation of the left ventricle on otherwise normal SPECT myocardial perfusion imaging studies.

Aim: TID in the setting of otherwise normal MPI has been suggested as a marker of high risk CAD. In this study we estimate the variance of TID in a normal population and the statistical frequency of false positive TID. This will provide an indirect measurement of predictive accuracy (PA) in a mixed referral population.

Myocardial uptake of 7'-(Z)-[(123)I]iodorotenone during vasodilator stress in dogs with critical coronary stenoses.

Background: There is a well-recognized need for a new generation of single photon emission computed tomography (SPECT) perfusion tracers with improved myocardial extraction over a wide flow range. Radiotracers that target complex I of the mitochondrial electron transport chain have been proposed as a new class of myocardial perfusion imaging agents. 7-(Z)-[(125)I]iodorotenone ((125)I-ZIROT) has demonstrated superior myocardial extraction and retention characteristics in rats and in isolated perfused rabbit hearts.

Prognosis in patients achieving ≥10 METS on exercise stress testing: was SPECT imaging useful?

Background: The benefit of myocardial perfusion imaging (MPI) over exercise ECG stress testing alone is unclear in individuals attaining a workload of ≥10 METS. The purpose of this prospective study is to determine mortality and nonfatal cardiac events in patients at either intermediate pretest risk for CAD or patients with known CAD, achieving ≥10 METS regardless of peak exercise heart rate. The authors previously reported a low prevalence of significant ischemia in this patient cohort.

Achieving an exercise workload of > or = 10 metabolic equivalents predicts a very low risk of inducible ischemia: does myocardial perfusion imaging have a role?

Objectives: We sought to identify prospectively the prevalence of significant ischemia (> or =10% of the left ventricle [LV]) on exercise single-photon emission computed tomography (SPECT) imaging relative to workload achieved in consecutive patients referred for myocardial perfusion imaging (MPI).

Background: High exercise capacity is a strong predictor of a good prognosis, and the role of MPI in patients achieving high workloads is questionable.

Methods: Prospective analysis was performed on 1,056 consecutive patients who underwent quantitative exercise gated (99m)Tc-SPECT MPI, of whom 974 attained > or =85% of their maximum age-predicted heart rate.

The role of quantitation in clinical nuclear cardiology: the University of Virginia approach.

Measurement of regional myocardial tracer concentration after stress and at rest allows the establishment of normal standards for myocardial perfusion and reversibility and provides a reference from which to determine disease severity and change in response to treatment. Using the partial-volume effect, we can also conveniently estimate regional myocardial thickening fractions corresponding to the same segments used for perfusion quantitation. This adds close comparison of perfusion and function as an aid to viability assessment and for recognition of possible ischemic dysfunction in cases of balanced ischemia or globally exhausted coronary flow reserve.

Comparison between angiography and fractional flow reserve versus single-photon emission computed tomographic myocardial perfusion imaging for determining lesion significance in patients with multivessel coronary disease.

We hypothesized that myocardial perfusion imaging (MPI) would fail to identify all vascular zones with the potential for myocardial ischemia in patients with multivessel coronary disease (MVD). MPI is based on the concept of relative flow reserve. The ability of these techniques to determine the significance of a particular stenosis in the setting of MVD is questionable.

Cardioprotection by adenosine A2A agonists in a canine model of myocardial stunning produced by multiple episodes of transient ischemia.

We sought to determine whether administration of a very low, nonvasodilating dose of a highly selective adenosine A(2A) receptor agonist (ATL-193 or ATL-146e) would be cardioprotective in a canine model of myocardial stunning produced by multiple episodes of transient ischemia. Twenty-four anesthetized open-chest dogs underwent either 4 (n=12) or 10 cycles (n=12) of 5-min left anterior descending coronary artery (LAD) occlusions interspersed by 5 or 10 min of reperfusion. Left ventricular thickening was measured from baseline through 180 min after the last occlusion-reperfusion cycle.

Organ biodistribution and myocardial uptake, washout, and redistribution kinetics of Tc-99m N-DBODC5 when injected during vasodilator stress in canine models of coronary stenoses.

Background: Technetium 99m N-DBODC5 is a new myocardial perfusion tracer shown to exhibit high heart uptake and rapid liver clearance in normal rats. The objectives of this canine study were (1) to compare the organ biodistribution and myocardial uptake, washout, and redistribution kinetics of Tc-99m N-DBODC5 with Tc-99m sestamibi over a period of 3 hours in a more clinically relevant large animal species and (2) to compare the myocardial uptake of Tc-99m N-DBODC5 with thallium 201 when co-injected during vasodilator stress in dogs with coronary stenoses.

Methods And Results: At peak adenosine-induced hyperemia, 10 dogs with critical left anterior descending artery stenoses received either Tc-99m N-DBODC5 (n = 6) or Tc-99m sestamibi (n = 4) and microspheres, followed by serial imaging and blood sampling over a period of 3 hours.

Fractional flow reserve of infarct-related arteries identifies reversible defects on noninvasive myocardial perfusion imaging early after myocardial infarction.

Objectives: We hypothesized that fractional flow reserve (FFR) of an infarct-related artery (IRA) early after myocardial infarction (MI) identifies inducible ischemia on noninvasive imaging.

Background: Early after MI, IRAs frequently have angiographically indeterminant lesions. Whether FFR can detect reversible perfusion defects early after MI when dynamic microvascular abnormalities are present is not known.

The effects of enhanced external counterpulsation on myocardial perfusion in patients with stable angina: a multicenter radionuclide study.

Background: Enhanced external counterpulsation (EECP) reduces angina and extends time to exercise-induced ischemia in patients with symptomatic coronary disease. One- and two-center studies and a retrospective case series reported that EECP improves myocardial perfusion in stable angina pectoris. We sought to critically evaluate and quantify the effect of EECP on myocardial perfusion.

Reduction of infarct size and postischemic inflammation from ATL-146e, a highly selective adenosine A2A receptor agonist, in reperfused canine myocardium.

Adenosine and adenosine A(2A) receptor agonists have been shown to limit myocardial infarct size when given at vasodilatory doses during reperfusion. This beneficial effect is thought to be due, in part, to stimulation of adenosine A(2A) receptors on inflammatory cells. The specific aims of this study were to determine whether the anti-inflammatory and cardioprotective properties of a novel adenosine A(2A) receptor agonist, ATL-146e (ATL), alone or in combination with the phosphodiesterase IV inhibitor rolipram would occur using very low, nonvasodilating doses.

99mTc-N-DBODC5, a new myocardial perfusion imaging agent with rapid liver clearance: comparison with 99mTc-sestamibi and 99mTc-tetrofosmin in rats.

Unlabelled: (99m)Tc-[bis (dimethoxypropylphosphinoethyl)-ethoxyethylamine (PNP5)]-[bis (N-ethoxyethyl)-dithiocarbamato (DBODC)] nitride (N-PNP5-DBODC or N-DBODC5) is a new monocationic myocardial perfusion tracer. We sought to compare the myocardial uptake and clearance kinetics and organ biodistribution of (99m)Tc-N-DBODC5 with (99m)Tc-sestamibi and (99m)Tc-tetrofosmin.

Methods: Seventy-five anesthetized Sprague-Dawley rats were injected intravenously with 22.

Incremental value of cardiac imaging in patients presenting to the emergency department with chest pain and without ST-segment elevation: a multicenter study.

Background: We hypothesized that imaging of regional myocardial function (RF) and perfusion (PER) will add incremental value for both diagnosis and short-term prognosis to routine demographic, clinical, and electrocardiographic findings in patients presenting to the emergency department (ED) with chest pain and without ST-segment elevation on the electrocardiogram.

Methods: We compared contrast echocardiography (CE) with gated single-photon emission computed tomography (SPECT) for this purpose. Both CE and SPECT readings included separate and composite assessments of both RF and PER.

Accuracy of detection of myocardial viability and residual infarct vessel stenoses with rest Tl-201 and adenosine Tc-99m sestamibi imaging after coronary reperfusion in dogs with experimental acute myocardial infarction.

Background: We sought to determine whether a dual-isotope imaging strategy (rest thallium 201/stress technetium 99m sestamibi) might be useful for assessing myocardial viability and residual ischemia in the infarct zone very early after reperfusion.

Methods And Results: Fifteen open-chest dogs had left anterior descending coronary artery occlusion for 60 minutes, followed by full reperfusion (group 1, n = 8) or reperfusion through a residual critical stenosis (group 2, n = 7). Tl-201 was injected at rest 45 minutes after reperfusion, and initial and 2-hour redistribution images were acquired.

Incremental value of combined perfusion and function over perfusion alone by gated SPECT myocardial perfusion imaging for detection of severe three-vessel coronary artery disease.

Objectives: We hypothesized that combining functional assessment to perfusion enhances the ability of electrocardiographic gating Tc-99m sestamibi single photon emission computed tomography (gated SPECT) myocardial perfusion imaging (MPI) to detect defects in multiple vascular territories in patients with severe three-vessel coronary artery disease (3VD).

Background: In patients with 3VD, perfusion defects in multiple vascular territories may not always be evident due to globally reduced perfusion.

Methods: Gated SPECT MPIs were interpreted sequentially with perfusion first, followed by combined perfusion/function, in 143 patients with angiographic 3VD and a control group of 112 non-3VD patients.

Effects of increased lipid concentration and hyperemic blood flow on the intrinsic myocardial washout kinetics of (99m)TcN-NOET.

Unlabelled: Bis(N-ethoxy,N-ethyldithiocarbamato)nitrido technetium (V) ((99m)Tc) ((99m)TcN-NOET) is a myocardial perfusion imaging agent demonstrating significant redistribution and currently in phase III clinical trials. Previous studies have suggested that (99m)TcN-NOET is bound intravascularly. Therefore, we sought to determine whether modifications in the vascular compartment would provide further insights into the mechanisms of (99m)TcN-NOET myocardial washout and redistribution.

Electromechanical mapping for detecting myocardial viability and ischemia in patients with severe ischemic cardiomyopathy.

This study was designed to evaluate several electromechanical mapping parameters for assessment of myocardial viability and inducible ischemia as defined by dipyridamole single-photon emission computed tomographic (SPECT) imaging at rest in patients with severe ischemic cardiomyopathy. Unipolar voltage, normalized unipolar voltage, bipolar voltage, and fragmentation were compared with tracer uptake at rest and reversibility on stress or rest quantitative technetium-99m sestamibi SPECT imaging in 32 patients with severe ischemic cardiomyopathy (left ventricular ejection fraction 0.24 +/- 0.