Tolerance and diagnostic accuracy of an abbreviated adenosine infusion for myocardial scintigraphy: a randomized, prospective study

BACKGROUND

The objectives of this study were 2-fold: (1) to determine the tolerance of adenosine perfusion tomography with the use of an abbreviated (3-minute) infusion in comparison to the standard (6-minute) infusion, and (2) to assess the relative diagnostic accuracy of a 3-minute adenosine infusion in patients referred for arteriography. An abbreviated adenosine infusion may decrease the frequency and duration of side effects and be a more cost-effective alternative.

METHODS AND RESULTS

We prospectively randomized 599 patients undergoing adenosine myocardial perfusion tomography to either a 3-minute or 6-minute adenosine infusion at 140 microg/kg per minute. Among the 599 enrolled patients, 142 subsequently underwent coronary angiography. Patients randomized to the 3-minute adenosine infusion tolerated the procedure better than those randomized to the standard infusion (P <.01). Flushing, headache, neck pain, and atrioventricular block were all significantly less frequent (P <.01) with the abbreviated infusion. Moreover, patients receiving the abbreviated infusion had less hypotension and tachycardia (P <.05). The sensitivity of the test for detection of coronary artery disease was 88% for both the 3- and 6-minute infusions. In patients with abnormal scan results, perfusion defect size was slightly larger in those receiving a 6-minute infusion versus those receiving a 3-minute infusion (P =.05).

CONCLUSIONS

An abbreviated 3-minute adenosine infusion, in combination with perfusion tomography, has similar sensitivity for detection of coronary artery disease and is better tolerated than the standard 6-minute infusion.

Myocardial perfusion in patients with total occlusion of a single coronary artery with and without collateral circulation

BACKGROUND

Previous studies that investigated the effects of coronary collateral circulation on myocardial perfusion were compromised by inclusion of patients with multivessel coronary artery disease, incomplete occlusion, prior myocardial infarction, or a combination of these. In this study we ascertained the relationship between angiographic collateral circulation and myocardial perfusion only in patients with total occlusion of a single coronary artery, in the absence of myocardial infarction or significant stenosis in the other coronary arteries.

METHODS AND RESULTS

Seventy-one consecutive patients underwent stress myocardial single photon emission computed tomography within 90 days of angiography. Collateral circulation was present in 49 patients and absent in 22 patients. All but 2 patients had abnormal perfusion by single photon emission computed tomography imaging, with a mean defect size of 19% +/- 12%, and most (83%) had reversible perfusion defects. Defect count activities improved from stress to rest (or redistribution) (45% +/- 13% to 59% +/- 14%, P <.001). Abnormal myocardial perfusion occurred with similar frequency in patients with collateral circulation and in those without it. Total defect size was 19% +/- 12% in patients with and 18% +/- 11% in those without collateral circulation (P = not significant). The extent of reversibility and defect count activity during stress and rest were similar in patients with collateral circulation and in those without it.

CONCLUSIONS

In patients with a single-vessel total coronary occlusion and without myocardial infarction, stress-induced myocardial ischemia is almost always present, irrespective of presence or absence of angiographic collaterals. These data lend support to the premise that collateral circulation is rather insufficient to prevent stress-induced ischemia, although it can preserve myocardial viability.

Myocardial perfusion and angiographic correlations in patients with ST-segment elevation during dobutamine stress perfusion imaging

BACKGROUND

There is scanty information on the angiographic and myocardial perfusion correlates of dobutamine-induced ST-segment elevation.

METHODS AND RESULTS

We studied 39 patients who exhibited ST-segment elevation during dobutamine perfusion tomography and had recent coronary angiography performed (ie, within 3 months of the dobutamine study). Baseline characteristics, extent of coronary artery disease, relationship of Q waves to ST-segment elevation, ischemic burden, and angiographic findings were assessed. Twenty-nine patients (74%) had prior myocardial infarction, and 77% had abnormal Q waves at baseline. Ninety-three percent of patients had abnormal perfusion imaging. Eighty percent of patients had multivessel coronary artery disease. The left ventricular ejection fraction by contrast ventriculography was 35% +/- 7% (mean +/- SD), the perfusion defect size was 32% +/- 15%, and 73% of patients had some degree of myocardial ischemia. A predominance of ischemia (>50% reversibility) occurred in 38% of patients with Q waves and in 70% of those without Q waves. There was also good agreement between the site of ST-segment elevation and the site of ischemia by perfusion imaging (79%) and between the site of ST-segment elevation and the location of the vessel with significant coronary stenosis (95%).

CONCLUSIONS

Patients with dobutamine-induced ST-segment elevation have a depressed left ventricular ejection fraction, a high frequency of multivessel disease, and markedly abnormal myocardial perfusion tomography. In patients with ST-segment elevation and abnormal Q waves, substantial scarring and superimposed ischemia coexist, whereas in patients without Q waves, ST-segment elevation usually denotes severe ischemia.

Deceleration time in ischemic cardiomyopathy: relation to echocardiographic and scintigraphic indices of myocardial viability and functional recovery after revascularization

BACKGROUND

In patients with heart failure secondary to left ventricular (LV) systolic dysfunction, a short deceleration time (DT) successfully predicts clinical outcome. The impact of myocardial viability and revascularization on the mitral inflow velocities, however, is unknown.

METHODS AND RESULTS

Forty patients with ischemic cardiomyopathy underwent (201)Tl scintigraphy (SPECT) and 2D, Doppler, and dobutamine echocardiography (DE, to 40 microg. kg(-1). min(-1)) 2 days before CABG. Echocardiography was repeated 3 months after revascularization to determine recovery of function. Significant correlations were present between DT and LV contractile reserve by DE (r=0.72), scar perfusion defect by SPECT (r=-0.69), and the change in ejection fraction (DeltaEF) after surgery (r=0.77) (all P:<0.01). DT >150 ms effectively identified (sensitivity 79%, specificity 81%) patients with DeltaEF >/=5%. The population was divided into 2 groups according to DT: group 1 (DT >150 ms, n=21) and group 2 (DT </=150 ms, n=19). At baseline, NYHA class, LV EF, age, and use of cardiovascular drugs were similar between the 2 groups. The number of viable segments by both DE and SPECT, however, was higher in group 1 (both P:<0.01), and only patients in group 1 had an increase in EF (29+/-4.8% to 40+/-8%, P:<0.01) after surgery. Death and heart transplantation occurred in 7 patients from group 2 and 1 patient from group 1 (P:=0.017).

CONCLUSIONS

In patients with ischemic cardiomyopathy, the reduced amount of viable myocardium results in a restrictive mitral inflow pattern, which in turn predicts poor survival.

Real-time assessment of myocardial perfusion and wall motion during bicycle and treadmill exercise echocardiography: comparison with single photon emission computed tomography

OBJECTIVES

We sought to determine the feasibility and accuracy of real-time imaging of myocardial contrast echocardiography (MCE) in detecting myocardial perfusion defects during exercise echocardiography compared with radionuclide tomography.

BACKGROUND

Ultrasound imaging at a low mechanical index and frame rate (10 to 20 Hz) after intravenous injections of perfluorocarbon containing microbubbles has the potential to evaluate myocardial perfusion and wall motion (WVM) simultaneously and in real time.

METHODS

One hundred consecutive patients with intermediate-to-high probability of coronary artery disease underwent treadmill (n = 50) or supine bicycle (n = 50) exercise echocardiography. Segmental perfusion with MCE and WM w ere assessed in real time before and at peak exercise using low mechanical index (0.3) and frame rates of 10 to 20 Hz after 0.3 ml bolus injections of intravenous Optison (Mallinckrodt Inc., San Diego, California). All patients had a dual isotope (rest thallium-201, stress sestamibi) study performed during the same exercise session, and 44 patients had subsequent quantitative coronary angiography.

RESULTS

In the 100 patients, agreement between MCE and single photon emission computed tomography (SPECT) was 76%, while it was 88% between MCE and WM assessment. Compared with quantitative angiography, sensitivity of MCE, SPECT and WM was comparable (75%), with a specificity ranging from 81% to 100%. The combination of MCE and WM had the best balance between sensitivity and specificity (86% and 88%,respectively) with the highest accuracy (86%).

CONCLUSIONS

The real-time assessment of myocardial perfusion during exercise stress echocardiography can be achieved with imaging at low mechanical index and frame rates. The combination of WM and MCE correlates well with SPECT and is a promising important addition to conventional stress echocardiography.

Altered adrenergic receptor density in myocardial hibernation in humans: A possible mechanism of depressed myocardial function

BACKGROUND

Alterations in adrenergic receptor densities can potentially contribute to myocardial dysfunction. Their relevance to myocardial hibernation in humans is unknown.

METHODS AND RESULTS

Accordingly, 22 transmural myocardial biopsies were obtained in 11 patients with ischemic ventricular dysfunction during bypass surgery, guided by transesophageal echocardiography. Patients underwent dobutamine echocardiography (DE) and rest scintigraphic studies before revascularization and DE at 3 to 4 months. alpha- and ss-receptor density (ARD and BRD) and extent of fibrosis were quantified from the myocardial biopsies. Of the 22 segments, 16 had abnormal rest function and 6 were normal. Severely hypokinetic or akinetic segments showed a 2.4-fold increase in ARD with a concomitant 50% decrease in BRD compared with normal segments. An increase in ARD, a decrease in BRD to a lesser extent, and thus an increase in ARD/BRD ratio were seen in dysfunctional segments with contractile reserve compared with normal segments and were most pronounced in those without contractile reserve (P:<0.001). Similar findings were observed if recovery of function or scintigraphic uptake was analyzed as a marker for viability. No significant relation between either ARD or BRD and percent myocardial fibrosis was noted (r=0.37 and -0.39, respectively).

CONCLUSIONS

Thus, graded and reciprocal changes in alpha- and ss-adrenergic receptor densities occur in viable, hibernating myocardium and may account in part for the observed depression in resting myocardial function and preserved contractile reserve in this entity.

123I-IPPA SPECT for the prediction of enhanced left ventricular function after coronary bypass graft surgery. Multicenter IPPA Viability Trial Investigators. 123I-iodophenylpentadecanoic acid

Fatty acids are the prime metabolic substrate for myocardial energy production. Hence, fatty acid imaging may be useful in the assessment of myocardial hibernation. The goal of this prospective, multicenter trial was to assess the use of a fatty acid, 123I-iodophenylpentadecanoic acid (IPPA), to identify viable, hibernating myocardium.

METHODS

Patients (n = 119) with abnormal left ventricular wall motion and a left ventricular ejection fraction (LVEF) < 40% who were already scheduled to undergo coronary artery bypass grafting (CABG) underwent IPPA tomography (rest and 30-min redistribution) and blood-pool radionuclide angiography within 3 d of the scheduled operation. Radionuclide angiography was repeated 6-8 wk after CABG. The study endpoint was a > or =10% increase in LVEF after CABG. The number of IPPA-viable abnormally contracting segments necessary to predict a positive LVEF outcome was determined by receiver operating characteristic (ROC) curves and was included in a logistic regression analysis, together with selected clinical variables.

RESULTS

Before CABG, abnormal IPPA tomography findings were seen in 113 of 119 patients (95%), of whom 71 (60%) had redistribution in the 30-min images. The LVEF increased modestly after CABG (from 32% +/- 12% to 36% +/- 8%, P< 0.001).A > or =10% increase in LVEF after CABG occurred in 27 of 119 patients (23%). By ROC curves, the best predictor of a > or =10% increase in LVEF was the presence of > or =7 IPPA-viable segments (accuracy, 72%; confidence interval, 64%-80%). Among clinical and scintigraphic variables, the single most important predictor also was the number of IPPA-viable segments (P = 0.008). The number of IPPA-viable segments added significant incremental value to the best clinical predictor model.

CONCLUSION

Asubstantial increase in LVEF occurs after CABG in only a minority of patients (23%) with depressed preoperative function. The number of IPPA-viable segments is useful in predicting a clinically meaningful increase in LVEF.

Myocardial blood flow and myocardial uptake of (201)Tl and (99m)Tc-sestamibi during coronary vasodilation induced by CGS-21680, a selective adenosine A(2A) receptor agonist

BACKGROUND

We investigated the hemodynamic and coronary vasodilatory effects of CGS-21680, a potent selective adenosine A(2A) agonist, as well as its potential use as a new stress modality in combination with perfusion scintigraphy.

METHODS AND RESULTS

A stenosis of the left anterior descending coronary artery (LAD) was produced in dogs to reduce the reactive hyperemic response to <20%. Adenosine and CGS-21680 were then separately infused to maximize left circumflex coronary artery (LCx) flow velocity. (201)Tl (0.5 mCi) and (99m)Tc-sestamibi (5 mCi) were injected at the maximal dose of CGS-21680. Heart rate decreased with adenosine but increased during CGS-21680 infusion (P<0.005). The decrease in systolic blood pressure was more prominent with adenosine than with CGS-21680 (P<0.005). In the control LCx zone, maximal myocardial blood flow (MBF) (measured by radioactive microspheres) increased 3.1-fold during adenosine infusion (P<0.005) and 3.8-fold during CGS-21680 infusion (P<0.005). In the stenotic LAD zone, MBF did not change significantly. During adenosine and CGS-21680 infusion, stenosis/control zone MBF ratios were comparable (0.32+/-0.11 versus 0.27+/-0.10, P=NS), and transmural (201)Tl and (99m)Tc-sestamibi count-activity ratios (0.48+/-0.11 and 0.51+/-0.09, respectively) were also comparable (P=NS). Myocardial scintigraphy uncovered perfusion defects in all dogs.

CONCLUSIONS

CGS-21680 elicits coronary vasodilation comparable to that of adenosine and produces profound heterogeneity of MBF and of (201)Tl and (99m)Tc-sestamibi myocardial uptake, rendering it a promising agent for pharmacological myocardial perfusion imaging.

Use of invasive and nuclear stress testing in patients with acute ischemic coronary syndromes in a large, urban, university-affiliated hospital

BACKGROUND

Several recent studies have suggested a high use of invasive procedures after acute myocardial infarction, without a corresponding improvement in survival. We assessed the relative use of invasive procedures and nuclear cardiac testing during acute coronary syndromes.

METHODS AND RESULTS

We examined the in-hospital utilization rates of invasive and nuclear stress tests and their association with in-hospital mortality in all patients hospitalized with an acute coronary syndrome in a single, university-affiliated hospital for 3 years. The study cohort consisted of 1704 consecutive patients with acute myocardial infarction and 2414 patients with unstable angina pectoris. The utilization rate of nuclear stress testing was much lower than that of coronary angiography in patients with either acute myocardial infarction (11.9% vs. 73.9%, P<.001) or unstable angina (8.5% vs. 79.3%, P<.001). Patients examined with nuclear stress testing, as compared with patients examined solely by means of coronary angiography, had lower revascularization and in-hospital mortality rates, both after acute myocardial infarction (29.2% vs. 70%, P<.001, and 1.5% vs. 9.6%, P<.001, respectively) and unstable angina (14.6% vs. 80.6%, P<.001, and 1% vs. 5.1%, P<.001, respectively). Revascularization guided by means of nuclear stress testing had a lower mortality rate than that performed without the benefit of a nuclear test, both in patients with acute myocardial infarction (0% vs. 10.5%) and in patients with unstable angina (0% vs. 5.9%).

CONCLUSION

Noninvasive stress imaging was used much less often than coronary angiography in patients with acute coronary syndromes. The lower mortality rate of patients examined with nuclear stress testing, compared with patients examined solely by means of coronary angiography, deserves further study, especially in patients undergoing revascularization.

End-diastolic wall thickness as a predictor of recovery of function in myocardial hibernation: relation to rest-redistribution T1-201 tomography and dobutamine stress echocardiography

OBJECTIVES

The study assessed whether end-diastolic wall thickness (EDWT), measured with echocardiography, is an important marker of myocardial viability in patients with suspected myocardial hibernation, and it compared this index to currently established diagnostic modalities of dobutamine stress echocardiography (DSE) and rest-redistribution thallium-201 (T1-201) scintigraphy.

BACKGROUND

Because myocardial necrosis is associated with myocardial thinning, preserved EDWT may provide a simple index of myocardial viability that is readily available from the resting echocardiogram.

METHODS

Accordingly, 45 patients with stable coronary artery disease and ventricular dysfunction underwent rest 2D echocardiograms, DSE and rest-redistribution T1-201 tomography before revascularization and a repeat resting echocardiogram > or =2 months later.

RESULTS

Global wall motion score index decreased from 2.38 +/- 0.73 to 1.94 +/- 0.82 after revascularization (p < 0.001). Thirty-eight percent of severely dysfunctional segments recovered resting function. Compared to segments without recovery of resting function, those with recovery had greater EDWT (0.94 +/- 0.18 cm vs. 0.67 +/- 0.22 cm, p < or = 0.0001) and a higher T1-201 uptake (78 +/- 13% vs. 59 +/- 21%; p < 0.0001). An EDWT >0.6 cm had a sensitivity of 94% and specificity of 48% for recovery of function. Similarly, a T1-201 maximal uptake of > or =60% had a sensitivity of 91% and specificity of 50%. Receiver operating characteristic curves for prediction of recovery of regional and global function were similar for EDWT and maximum T1-201 uptake. Combination of EDWT and any contractile reserve during DSE for recovery of regional function improved the specificity to 77% without a significant loss in sensitivity (88%).

CONCLUSIONS

End-diastolic wall thickness is an important marker of myocardial viability in patients with suspected hibernation, and it can predict recovery of function similar to T1-201 scintigraphy. Importantly, a simple measurement of EDWT < or =0.6 cm virtually excludes the potential for recovery of function and is a valuable adjunct to DSE in the assessment of myocardial viability.

Comparison of global and regional left ventricular function assessed by gated-SPECT and 2-D echocardiography

Left ventricular (LV) function and volumes have major diagnostic and prognostic importance in patients with heart diseases. Those measurements are most commonly obtained with echocardiographic techniques. Recently, with the use of electrocardiographic gating during the acquisition of myocardial perfusion scintigraphy, it has become possible to simultaneously assess LV perfusion, function and volumes. Both technetium-99m labeled agents and thallium-201, the most commonly used tracers for perfusion scintigraphy, can be used for gated perfusion purposes. Many authors compared gated perfusion images to echocardiography, in regard to LV global and segmental wall motion as well as volumes. We performed gated single photon emission computed tomography (SPECT) and echocardiography in 109 consecutive patients (53 male, 56 female, mean age 63 +/- 14 years) within 15 days of each other. Gated tomographic data, including LV volumes, LV ejection fraction and segmental wall motion, were processed using an automatic algorithm whereas echocardiography used standard techniques. To obtain interobserver and intraobserver variability of regional wall motion, we randomly re-analyzed 34 of the 109 gated SPECT studies. The correlations between gated tomography and echocardiography with respect to end-diastolic volume, end-systolic volume and left ventricular ejection fraction were good to excellent (all p < 0.001, r values > or = 0.68) regardless of the use of post-stress or rest/redistribution images, thallium-201 or technetium-99m tracers. The agreement between both techniques, regarding segmental wall motion analysis were also good. Intraobserver and interobserver variability for regional wall motion were good to excellent, with an agreement of 90% and 88%, respectively. Other authors also had similar results in different studies with different populations, tracers, imaging acquisition and processing protocols. Thus, quantitative gated SPECT, using a variety of protocols and with either Tl-201 or Tc-99m tracers, has a good correlation with echocardiography for the measurements of absolute LV volumes and LV global and regional function. This technique is highly reproducible and can be used clinically for those measurements, with the additional advantage that the ventricular performance parameters are obtained from the perfusion images. Furthermore, contrary to echocardiographic techniques used to assess LV volumes and LV function, which are quite labor intensive and more observer-dependent, the gated SPECT technique is nearly totally automatic, and highly reproducible.

Severity of coronary artery calcification by electron beam computed tomography predicts silent myocardial ischemia

BACKGROUND

Detection of subclinical coronary artery disease (CAD) before the development of life-threatening cardiac complications has great potential clinical relevance. Electron beam computed tomography (EBCT) is currently the only noninvasive test that can detect CAD in all stages of its development and thus has the potential to be an excellent screening technique for identifying asymptomatic subjects with underlying myocardial ischemia.

METHODS AND RESULTS

Over 2.5 years, we prospectively studied 3895 generally asymptomatic subjects with EBCT, 411 of whom had stress myocardial perfusion tomography (SPECT) within a close (median, 17 days) time period. SPECT and exercise treadmill results were compared with the coronary artery calcium score (CACS) as assessed by EBCT. The total CACS identified a population at high risk for having myocardial ischemia by SPECT although only a minority of subjects (22%) with an abnormal EBCT had an abnormal SPECT. No subject with CACS <10 had an abnormal SPECT compared with 2.6% of those with scores from 11 to 100, 11.3% of those with scores from 101 to 399, and 46% of those with scores >/=400 (P<0.0001). CACS predicted an abnormal SPECT regardless of subject age or sex.

CONCLUSIONS

CACS identifies a high-risk group of asymptomatic subjects who have clinically important silent myocardial ischemia. Our results support the role of EBCT as the initial screening tool for identifying individuals at various stages of CAD development for whom therapeutic decision making may differ considerably.

Gated myocardial perfusion tomography for the assessment of left ventricular function and volumes: comparison with echocardiography

The purpose of this study was to evaluate left ventricular volumes and function by gated SPECT using different tracers and protocols in comparison with quantitative echocardiography. Gated myocardial perfusion scintigraphy permits simultaneous assessment of left ventricular perfusion, function and volumes. Information is scanty regarding the accuracy of absolute left ventricular volumes measurements by this technique.

METHODS

We performed gated SPECT and echocardiography within 15 d of each other in 109 consecutive patients (53 men, 56 women; mean age 63 +/- 14 y). Gated tomographic data, including left ventricular volumes and ejection fraction, were processed using an automatic algorithm, whereas echocardiography used standard techniques.

RESULTS

The correlations between gated tomography and echocardiography with respect to end-diastolic volume, end-systolic volume and left ventricular ejection fraction were good to excellent (all P < 0.001, r values > or = 0.68), regardless of the use of poststress or rest/redistribution images, 201Tl or 99mTc tracers. End-systolic volume was similar with gated tomography and echocardiography (P = ns), but end-diastolic volume and left ventricular ejection fraction were significantly higher with echocardiography (P < or = 0.05).

CONCLUSION

Quantitative gated tomography, using either 201Tl or 99mTc tracers, has a good correlation with echocardiography for the assessment of left ventricular volumes and ejection fraction. These results support the clinical use of this new technique.

Stress myocardial perfusion imaging versus echocardiography for the diagnosis and risk stratification of patients with known or suspected coronary artery disease

Stress perfusion imaging and stress echocardiography (ECHO) are both very useful for assessment of diagnosis and risk stratification of patients with coronary artery disease (CAD). Both techniques have been well validated during exercise and inotropic stress, but coronary vasodilation stress is better used in combination with perfusion imaging. The overall sensitivity for detection of CAD is slightly higher by single photon emission computed tomography (SPECT) than by two-dimensional (2D) ECHO during all stress modalities, whereas the specificity is slightly higher by ECHO, although the differences in general are not statistically significant. SPECT, however, appears to be superior to ECHO in the diagnosis of isolated circumflex stenosis, as well as for the correct identification of multivessel CAD. A substantially greater amount of information is available regarding risk stratification with SPECT than with 2D ECHO. Although the data suggest that both techniques are very useful for risk stratification of patients with stable CAD, after myocardial infarction, and for preoperative risk stratification, the risk for cardiac events is lower in the presence of a normal stress SPECT study than of a normal stress ECHO.

Relation of the contractile reserve of hibernating myocardium to myocardial structure in humans

BACKGROUND

Although dobutamine echocardiography (DE) is widely used to assess myocardial viability in humans, little is known about the relation between contractile reserve and myocardial structure.

METHODS AND RESULTS

We evaluated 20 patients with coronary disease (64+/-13 years old, ejection fraction 28+/-7.5%) with DE (up to 40 micrograms . kg(-1). min(-1)), rest-redistribution (201)Tl single photon emission CT, and quantitative angiography before bypass surgery. During surgery, patients underwent transmural myocardial biopsies (n=37) guided by transesophageal echocardiography to determine the extent of interstitial fibrosis and intracellular and interstitial proteins by histopathology and immunohistochemistry. Among the 37 segments biopsied, 16 recovered function as assessed 2 to 3 months later. Segments with postoperative functional recovery had more wall thickening at low-dose DE (28% versus 3%, P<0.001), higher thallium uptake (69% versus 48%, P=0.03), and less interstitial fibrosis (2% versus 28%, P<0.001). Quantitative angiographic parameters did not predict recovery of function. Segments with DE viability (contractile reserve and/or ischemia) had less fibrosis (2.7% versus 28%, P<0.001), less vimentin and fibronectin (both P<0.01), more glycogen (P=0.016), and higher thallium uptake (64% versus 35.5%, P<0.05) than those without viability. Viable segments by both DE and thallium had less fibrosis (1%) than those viable by 1 of the 2 techniques (9%) or not viable by both (28%, P=0.005). Thickening at low-dose DE correlated well with the extent of interstitial fibrosis (r=-0.83, P<0.01).

CONCLUSIONS

Contractile reserve during DE correlates inversely with the extent of interstitial fibrosis and the amount of fibronectin and vimentin and directly with rest-redistribution thallium uptake.

Accuracy of left ventricular ejection fraction determined by gated myocardial perfusion SPECT with Tl-201 and Tc-99m sestamibi: comparison with first-pass radionuclide angiography

BACKGROUND

We compared estimates of left ventricular ejection fraction (LVEF) assessed by gated single photon emission computed tomography (SPECT), using both technetium-99m sestamibi and thallium-201, with those obtained by first-pass radionuclide angiography (FPRNA) in patients with a broad spectrum of LVEF and perfusion abnormalities.

METHODS

Sixty-three patients were randomly selected to undergo a dual isotope gated SPECT study (rest Tl-201 followed by adenosine Tc-99m sestamibi scintigraphy). Studies were processed by use of the Cedars quantitative gated SPECT software. FPRNA was acquired during an intravenous bolus injection of Tc-99m sestamibi and processed with a commercially available software.

RESULTS

The estimates of LVEF were similar (P = NS) with Tl-201 gated SPECT (54% +/- 15%), Tc-99m gated SPECT (54% +/- 16%), and FPRNA (54% +/- 12%). There was an excellent correlation between Tc-99m and Tl-201 gated SPECT (Pearson's r = 0.92, P < .0001). There were also good linear correlations between Tc-99m sestamibi gated SPECT and FPRNA (Pearson's r = 0.85, P < .0001), as well as between Tl-201 gated SPECT and FPRNA (Pearson's r = 0.84, P < .0001). In the 16 patients with LVEF < 50%, Tc-99m sestamibi gated SPECT and FPRNA (Pearson's r = 0.84, P < .0001) and Tl-201 gated SPECT and FPRNA (Pearson's r = 0.92, P < .0001) correlated well.

CONCLUSION

LVEF can be accurately assessed by gated SPECT with either Tc-99m sestamibi or Tl-201 in properly selected patients with normal or depressed left ventricular function.

Evaluation of left ventricular wall motion, volumes, and ejection fraction by gated myocardial tomography with technetium 99m-labeled tetrofosmin: a comparison with cine magnetic resonance imaging

BACKGROUND

Whether left ventricular function can be assessed accurately by gated single photon emission computed tomography (SPECT) in patients with myocardial infarction and severe perfusion defects is not well known.

METHODS AND RESULTS

Twenty-five patients with an acute myocardial infarction underwent 99mTc-labeled tetrofosmin (99mTc-tetrofosmin) gated SPECT and cine magnetic resonance imaging (MRI). Wall motion was assessed in 13 left ventricular segments using a 5-point scoring system ranging from 3 (normal) to -1 (dyskinetic). Exact agreement for wall motion scores between gated SPECT and MRI was excellent (92%, kappa = 0.82). Furthermore, correlations between the two techniques were also good for end-diastolic volume (r = 0.81, P < .0001), end-systolic volume (r = 0.92, P < .0001), and ejection fraction (r = 0.93, P < .0001).

CONCLUSION

In patients with a recent myocardial infarction, 99mTc-tetrofosmin gated SPECT provides reliable evaluation of global and regional ventricular function and volumes.

Long-term prognostic value of exercise echocardiography compared with exercise 201Tl, ECG, and clinical variables in patients evaluated for coronary artery disease

BACKGROUND

The accuracy of exercise echocardiography and 201Tl single photon emission computed tomography (SPECT) is similar in the diagnosis of coronary artery disease (CAD). However, comparative data on long-term prognosis are lacking.

METHODS AND RESULTS

Clinical variables and exercise, echocardiographic, and 201Tl tomographic parameters were studied in 248 patients (age, 56+/-12 years [mean+/-SD]; 189 men) who underwent simultaneous treadmill exercise 201Tl SPECT and echocardiography. Follow-up was obtained in 225 patients (91%) at a mean of 3.7+/-2.0 years. A total of 64 cardiac events occurred. With the use of stepwise logistic regression, 4 models simulating clinical stress testing scenarios were evaluated in the prediction of all cardiac events, ischemic events, and/or cardiac death. The best clinical models were exercise echocardiography with exercise ECG and exercise 201Tl SPECT with exercise ECG. Both models were comparable in the prediction of cardiac events. For the exercise echocardiography model, exercise wall motion score index and induction of ischemia were the strongest predictors of events with ORs of 2.63 per unit increment (95% CI, 1. 34 to 5.17; P=0.005) and 4.1 (95% CI, 1.32 to 12.79; P=0.015), respectively. For the model with exercise 201Tl SPECT, the strongest predictor was ischemic perfusion defect (OR, 4.93; 95% CI, 1.72 to 14.08; P=0.003). The absence of ST changes during exercise decreased the risk of events. For the prediction of ischemic events and/or cardiac death, echocardiographic and 201Tl parameters were the only predictive variables.

CONCLUSIONS

In patients evaluated for CAD, exercise echocardiography and 201Tl combined with ECG variables provide comparable prognostic information and can be used interchangeably for risk stratification.

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.

Echocardiography-guided ethanol septal reduction for hypertrophic obstructive cardiomyopathy

BACKGROUND

Left ventricular outflow tract (LVOT) obstruction is frequently responsible for symptoms in hypertrophic obstructive cardiomyopathy (HOCM). Medical therapy is often not sufficient to control these symptoms, and surgical myotomy-myomectomy is required.

METHODS AND RESULTS

We enrolled 33 symptomatic patients with HOCM and obstruction (>/=40 mm Hg gradient at rest or >/=60 mm Hg dobutamine-provoked). By contrast echocardiography, the bulging septum was localized and infarcted by injection of 2 to 5 mL of absolute ethanol into the septal artery(ies) supplying the hypertrophied area. Baseline echocardiograms with Doppler, myocardial perfusion tomograms, and treadmill exercise or pharmacological testing were compared with those at 6 weeks and 6 months. The mean rise in creatine kinase was 1964+/-796 U. All patients experienced symptomatic relief; NYHA class decreased from 3. 0+/-0.5 to 0.9+/-0.6 (P<0.001). Exercise time increased from 286+/-193 to 421+/-181 seconds (P=0.03). The resting and dobutamine-provoked gradient decreased from 49+/-33 and 96+/-34 mm Hg to 9+/-19 (P<0.001) and 24+/-31 mm Hg (P<0.001), respectively. Echocardiograms repeated at 6 weeks after the procedure showed a 28% reduction in septal thickness and 17% reduction in left ventricular mass. Myocardial perfusion imaging showed a "septal amputation pattern," with scarring in the upper and middle septal areas. Complete heart block developed in 11 patients, who then required permanent pacemaker implantation.

CONCLUSIONS

Echocardiography-guided ethanol septal reduction in patients with HOCM is a safe, minimally invasive procedure that provides symptomatic relief with improved hemodynamic and left ventricular parameters.

Role of myocardial contrast echocardiography during nonsurgical septal reduction therapy for hypertrophic obstructive cardiomyopathy

OBJECTIVES

This study was undertaken to evaluate the ability of myocardial contrast echocardiography (MCE) to guide the targeted delivery of ethanol during nonsurgical septal reduction therapy (NSRT) and to assess the relation between the MCE risk area and infarct size determined by enzymatic and radionuclide methods.

BACKGROUND

NSRT with intracoronary ethanol is a new promising treatment for patients with hypertrophic obstructive cardiomyopathy (HOCM). Proper localization and quantification of the septal infarct before ethanol injection are highly desirable. MCE can provide accurate delineation of the vascular territory of the coronary arteries.

METHODS

Twenty-nine patients with HOCM and maximal medical therapy underwent NSRT. The left ventricular outflow tract (LVOT) gradient by Doppler echocardiography at baseline was 53 +/- 16 mm Hg (mean +/- SD). Before NSRT, MCE was performed in all patients with intracoronary sonicated albumin (Albunex). Diluted sonicated albumin (Albunex) was selectively injected into the septal perforator arteries during simultaneous transthoracic imaging. Immediately after MCE, ethanol was injected into the same vessel. Plasma total creatine kinase (CK), total CK-MB fraction and CK-MB fraction subforms were measured at baseline and serially for 36 h.

RESULTS

LVOT gradient decreased to 12 +/- 6 mm Hg (p < 0.001) after NSRT. Accurate mapping of the vascular beds of the septal perforators was successfully attained in all patients by MCE. Furthermore, the MCE risk area correlated well with peak CK (r = 0.79, p < 0.001). Six weeks after NSRT, 23 patients underwent myocardial perfusion studies performed with single-photon emission computed tomography (SPECT). Mean SPECT septal perfusion defect size involved 9.5 +/- 6% of the left ventricle and correlated well with MCE area (r = 0.7), with no statistically significant difference between the risk area estimated by MCE and that by SPECT.

CONCLUSIONS

Estimation of the size of the septal vascular territory with MCE is accurate, safe and feasible in essentially all patients during NSRT. MCE can delineate the perfusion bed of the septal perforators and can predict the infarct size that follows ethanol injection.

Diagnostic accuracy of stress thallium-201 tomography in patients with left ventricular hypertrophy

Two hundred patients with echocardiographically proven left ventricular hypertrophy underwent quantitative stress thallium tomography. The overall sensitivity and specificity were high (84% and 82%, respectively).

Assessment of myocardial viability with 99mTc-sestamibi tomography before coronary bypass graft surgery: correlation with histopathology and postoperative improvement in cardiac function

BACKGROUND

Assessment of myocardial viability by 99mTc-sestamibi remains controversial. Accordingly, we investigated the use of sestamibi as a marker of myocardial viability, defined by histopathology, and for predicting improvement of myocardial function after coronary artery bypass graft surgery (CABG).

METHODS AND RESULTS

99mTc-sestamibi perfusion tomography and radionuclide angiography were performed within 2 days before CABG in 21 patients with > or = 75% stenosis of the left anterior descending coronary artery and resting anterior wall dyssynergy. During CABG, transmural myocardial biopsies were obtained from the dyssynergic anterior wall and from normal myocardial segments to determine the extent of viable myocardium by histopathology. Improvement of regional left ventricular function was evaluated by radionuclide angiography at 6 to 8 weeks after CABG. There was a good correlation (r=.85, P<.001) between the quantified sestamibi activity and the extent of viable myocardium determined morphometrically. Among 21 biopsied dyssynergic myocardial segments, 11 improved their function after CABG and 10 failed to improve. Biopsied segments with improved postoperative function had significantly higher sestamibi activity (81+/-5% versus 49+/-16%, P<.0001) and significantly lower extent of interstitial fibrosis (7+/-4% versus 31+/-21%, P=.0002) than segments that failed to improve. A 55% threshold of 99mTc-sestamibi activity had positive and negative predictive values of 79% and 100%, respectively, for recovery of function after CABG in the biopsied segments.

CONCLUSIONS

Myocardial 99mTc-sestamibi activity correlates well with the extent of viable myocardium and predicts improvement in regional function after CABG. This lends support to the use of sestamibi as a myocardial viability agent.

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.

Association of angiotensin I-converting enzyme gene polymorphism with myocardial ischemia and patency of infarct-related artery in patients with acute myocardial infarction

OBJECTIVES

We determined the influence of angiotensin I-converting enzyme (ACE) insertion (I)/deletion (D) polymorphism on the extent of myocardial ischemia in patients with acute myocardial infarction.

BACKGROUND

The I/D polymorphism, which in part controls plasma and tissue expression of ACE, has been implicated in predisposition to myocardial infarction and ventricular remodeling.

METHODS

I/D genotyping, predischarge adenosine-thallium-201 perfusion tomography and radionuclide angiography were performed in 113 patients (72 men, 41 women) with a diagnosis of acute myocardial infarction. A subgroup of 96 patients also underwent coronary angiography.

RESULTS

Genotypes DD, ID and II were present in 27, 56 and 30 patients, respectively. There was no significant difference in the baseline characteristics of patients, total creatine kinase, peak MB fraction, Killip class, mean ejection fraction or the number of diseased vessels in patients with the DD, ID or II genotype. However, the size of the total and the reversible perfusion defects was greater in those with DD than in those with ID or II genotype (total defect size [mean +/- SD] 33.7 +/- 22.5%, 29.5 +/- 19.2% and 22.2 +/- 16.0%, respectively [p = 0.022]; reversible defect size 18.0 +/- 16.0%, 12.1 +/- 11.6% and 8.2 +/- 7.8%, respectively [p = 0.006]). Occlusion of the infarct-related artery was also more common in patients with DD genotype (odds ratio 3.9, 95% confidence interval 1.4 to 11.0). Multivariate analysis showed that the I/D genotype was an independent predictor of perfusion defect size and patency of the infarct-related artery (p = 0.001).

CONCLUSIONS

DD genotype was associated with a larger ischemic defect and occlusion of the infarct-related artery. Patients with DD genotype, having a larger ischemic defect, are expected to be at a greater risk for subsequent cardiovascular events.

Enhanced accuracy of defect detection by myocardial single-photon emission computed tomography with attenuation correction with gadolinium 153 line sources: evaluation with a cardiac phantom

BACKGROUND

Photon attenuation is a major cause of artifacts on single-photon emission tomographic imaging.

METHODS AND RESULTS

To study a new method to perform photon attenuation correction (AC), we used a cardiac phantom filled with (99m)Tc and imaged it (1) without extrinsic attenuation or defects, (2) with extrinsic attenuation but without defects, (3) without extrinsic attenuation but with defects involving 10% of the myocardial volume and activity ranging from 0% to 75% of maximum, and (4) with both extrinsic attenuation and defects. Transmission and emission images acquired with a dual-head single-photon emission computed tomographic system with 153Gd line sources were processed by iterative maximum-likelihood-expectation-maximization and were evaluated both qualitatively and quantitatively. The small defects were readily identified both before and after AC. Mean count activity (percent of maximal activity) of the segments with overlying extrinsic attenuation but without defects was only 56% +/- 4% without AC but increased to 86% +/- 4% with AC (p < 0.0001). Without AC, the count activities in the defects with overlying extrinsic attenuation were lower than the actual defect activities, but AC resulted in better approximation of actual defect activities in all but the most severe (0% tracer activity) defects.

CONCLUSION

This new AC method provided an improved estimation of actual myocardial count activity. Even small defects with mild reduction in tracer activity were still identifiable after AC.

Diagnosis of coronary artery disease by exercise thallium-201 tomography in patients with a right ventricular pacemaker

OBJECTIVES

We sought to study the accuracy of exercise perfusion scintigraphy in patients with an implanted apical right ventricular pacemaker.

BACKGROUND

The specificity of exercise perfusion scintigraphy is decreased in patients with a left bundle branch block. Patients with a permanent ventricular pacemaker have a similar conduction abnormality that may also potentially result in similar false positive perfusion defects.

METHODS

One hundred five patients with a right ventricular pacemaker underwent exercise thallium-201 tomography and coronary angiography within 7 days of each other. Patients with a previous myocardial infarction were excluded.

RESULTS

Patients were classified into four groups according to the agreement or disagreement between the thallium tomographic and coronary angiographic results. Only 8% of patients with normal results by both techniques were continuously paced during exercise, compared with 78% of patients with normal angiographic results but abnormal scintigraphic results. The mean defect size was 12% in the latter group. Most of the false positive defects were localized to the inferoposterior (71%), apical (50%) and inferoseptal (28%) walls.

CONCLUSIONS

Patients who are paced in the right ventricular apex and who continue to be paced throughout exercise have a high incidence of false positive thallium-201 single-photon emission computed tomographic defects.

Adenosine thallium-201 tomography in evaluation of graft patency late after coronary artery bypass graft surgery

OBJECTIVES

We sought to ascertain the utility of adenosine thallium-201 tomography for assessing graft stenoses late after coronary artery bypass graft surgery.

BACKGROUND

Although pharmacologic perfusion imaging has been increasingly used in the assessment of patients with coronary artery disease, the value of this stress modality for detecting coronary artery bypass graft stenosis late after surgery is unknown.

METHODS

We studied 109 patients who underwent both adenosine thallium-201 tomography and coronary angiography at 6.7 +/- 4.8 (mean +/- SD) years after coronary artery bypass graft surgery. Adenosine thallium-201 tomography was assessed quantitatively by computer-generated polar maps of the myocardial thallium-201 activity.

RESULTS

On coronary angiography, significant graft stenoses were present in 68 patients, 65 of whom had a corresponding perfusion defect as shown by thallium-201 tomography (sensitivity 96%). Significant stenoses were present in 107 (37.8%) of 283 grafts. The overall specificity by quantitative tomography was 61%. Seventy percent of the apparently false positive perfusion defects could be explained on the basis of unbypassed native disease or by the presence of fixed defects in patients with previous myocardial infarction.

CONCLUSIONS

Thus, results of adenosine thallium-201 tomography are nearly always abnormal in patients with late coronary graft stenosis. Most of the false positive defects appear to be due to either unbypassed native disease or a previous myocardial infarction.

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.

Identification of hibernating myocardium: comparative accuracy of myocardial contrast echocardiography, rest-redistribution thallium-201 tomography and dobutamine echocardiography

OBJECTIVES

We sought to evaluate the comparative accuracy of myocardial contrast echocardiography (MCE), quantitative rest-redistribution thallium-201 (Tl-201) tomography and low and high dose (up to 40 microg/kg body weight per min) dobutamine echocardiography (DE) in identifying myocardial hibernation.

BACKGROUND

Myocardial contrast echocardiography can assess myocardial perfusion and may therefore be useful in predicting myocardial hibernation. However, its accuracy in comparison to myocardial perfusion scintigraphy and to that of high dose DE remains to be investigated.

METHODS

Eighteen patients (aged [+/- SD] 57 +/- 10 years) with stable coronary artery disease and ventricular dysfunction underwent the above three modalities before coronary revascularization. Myocardial contrast echocardiography was achieved with intracoronary Albunex. Rest echocardiographic and Tl-201 studies were repeated > or = 6 weeks after revascularization.

RESULTS

Of 109 revascularized segments with severe dysfunction, 46 (42%) improved. Left ventricular ejection fraction increased from 38 +/- 14% to 45 +/- 13% at follow-up (p = 0.003). Rest Tl-201 uptake and the ratio of peak contrast intensity of dysfunctional to normal segments with MCE were higher (p < 0.01) in segments that recovered function compared with those that did not. Myocardial contrast echocardiography, thallium scintigraphy and any contractile reserve during DE had a similar sensitivity (89% to 91%) with a lower specificity (43% to 66%) for recovery of function. A biphasic response during DE was the most specific (83%) and the least sensitive (68%) (p < 0.01). The best concordance with MCE was Tl-201 (80%, kappa 0.57). Changes in ejection fraction after revascularization related significantly to the number of viable dysfunctional segments by all modalities (r = 0.54 to 0.65).

CONCLUSIONS

In myocardial hibernation, methods evaluating rest perfusion (MCE, Tl-201) or any contractile reserve have a similar high sensitivity but a low specificity for predicting recovery of function. A limited contractile reserve (biphasic response) increases the specificity of DE. Importantly, the three techniques identified all patients who had significant improvement in global ventricular function.

Diagnosis and management of acute myocardial infarction

Nuclear cardiology offers techniques for assessing cardiac perfusion and function that provide useful information for diagnosing and managing acute myocardial infarction (MI). In particular, myocardial perfusion imaging provides important data on infarct size and myocardial viability that can help determine the best treatment strategies for patients with acute MI. First-pass or blood pool radionuclide angiographic assessment of ventricular ejection fraction remains an important prognostic indicator in acute MI, regardless of whether thrombolytic therapy is used. Comparative studies of radiotracer techniques and coronary angiography show that myocardial perfusion and ejection fraction can predict the risk of future cardiac events reliably in patients with acute MI, whereas the anatomic data provided by coronary angiography (e.g., degree of stenosis and presence of multivessel disease) have little prognostic value. Managed-care organizations could reduce costs and improve patient outcomes by relying more on nuclear cardiology and less on angiography in the management of patients' with acute MI.

Dobutamine echocardiography and quantitative rest-redistribution 201Tl tomography in myocardial hibernation. Relation of contractile reserve to 201Tl uptake and comparative prediction of recovery of function

BACKGROUND

The purposes of this study were to evaluate the comparative accuracy of dobutamine echocardiography and quantitative rest-redistribution 201Tl tomography in the prediction of recovery of function after revascularization and to assess the relation of contractile reserve to thallium uptake.

METHODS AND RESULTS

Thirty-four patients with stable coronary disease and regional dysfunction underwent dobutamine echocardiography (2.5 up to 40 micrograms.kg-1.min-1) and rest-redistribution 201Tl tomography 1 day before revascularization. Resting echocardiography and scintigraphy were repeated at > or = 6 weeks. Before revascularization, resting 201Tl uptake was similar in segments demonstrating biphasic or sustained improvement and was higher than in those exhibiting no change or worsening function during dobutamine. After revascularization, 201Tl uptake increased only in segments that showed a biphasic response (from 66 +/- 12% to 78 +/- 13%; P < .05). Biphasic response had a sensitivity of 74% and specificity of 89% for prediction of recovery. The use of biphasic or sustained improvement responses increased the sensitivity to 86% with a decrease in specificity to 68%. Qualitative thallium assessment provided a high sensitivity (98%) but poor specificity (27%). Quantification of thallium uptake, however, improved its accuracy: a maximal uptake (at rest or redistribution) of > or = 60% yielded a 90% sensitivity and a 56% specificity.

CONCLUSIONS

In patients with myocardial hibernation, biphasic response during dobutamine is less sensitive but more specific for recovery of function, whereas indexes of 201Tl scintigraphy are in general more sensitive and less specific, the least accurate being a qualitative assessment of thallium uptake. The sensitivity and specificity of both methods, however, can be altered depending on the quantitative criteria of thallium uptake or combination of responses of the myocardium to dobutamine.

Assessing coronary artery disease with dipyridamole technetium-99m-tetrofosmin SPECT: a multicenter trial

Exercise 99mTc-tetrofosmin myocardial scintigraphy is as accurate as exercise 201TI imaging. Thus far, no data are available on tetrofosmin imaging during pharmacologic stress. We evaluated the feasibility of using. 99mTc-tetrofosmin myocardial SPECT during vasodilation with dipyridamole for detecting coronary artery disease.

METHODS

Sixty-four patients, enrolled in three centers in the U.S., underwent one-day dipyridamole/rest tetrofosmin SPECT. Coronary angiography, performed in 59 patients within 2 mo of the SPECT study, revealed normal coronary arteries or insignificant coronary stenosis in 11 patients and significant (> or = 50% luminal diameter stenosis) coronary stenoses in 48 patients.

RESULTS

Sensitivity and specificity of tetrofosmin SPECT for detecting coronary artery disease were 85% and 55%, respectively, in the overall population and 81% and 55% in patients without prior coronary artery bypass surgery. The overall sensitivity and specificity of tetrofosmin tomographic imaging for detection of individual coronary stenoses were 53% and 72%, respectively, in the overall population and 54% and 80% in the patients without prior coronary artery bypass surgery.

CONCLUSION

One-day dipyridamole/rest 99mTc-tetrofosmin myocardial perfusion imaging is feasible and has a high sensitivity for detection of coronary artery disease.

Visualization of ventricular fibroelastoma with a video-assisted thoracoscope

Left ventricular papillary fibroelastomas are associated with a high risk of cerebral embolization. Two-dimensional echocardiography and intraoperative transesophageal echocardiography are helpful in diagnosing tumors, planning a surgical approach, and achieving adequate excision. A video-assisted thoracoscope via the left atrium was used to visualize a left ventricular papillary fibroelastoma. Thoracoscopic visualization facilitated excision of a mass within the chordae tendineae between the anterolateral papillary muscle and the left ventricular wall. Video-assisted thoracoscopy greatly facilitates exposure/excision of deeper intracavitary left ventricular masses.

Prognostic value of exercise 201Tl tomography in patients treated with thrombolytic therapy during acute myocardial infarction

BACKGROUND

Although myocardial perfusion scintigraphy is of proven value in the risk stratification of patients with a recent myocardial infarction who receive conventional therapy, its value in patients undergoing thrombolytic therapy remains controversial.

METHODS AND RESULTS

Seventy-one patients who received thrombolytic therapy for acute myocardial infarction had exercise 201Tl tomography and coronary angiography before hospital discharge. Eleven (15%) of 71 patients had ischemic ST-segment depression during exercise, whereas 27 patients (38%) had scintigraphic ischemia. Twenty-five (37%) of 68 patients had a cardiac event consisting of either death (n = 2), recurrent myocardial infarction (n = 5), congestive heart failure (n = 7), or unstable angina (n = 11) during a follow-up of 26 +/- 18 months. Univariate predictors of cardiac events were as follows: Killip class (P = .04); left ventricular ejection fraction (P < .0005); total (P = .002) and ischemic (P < .0005) perfusion defect size; percent thallium lung uptake (P = .001); presence of infarct-zone redistribution (P = .02); and multivessel coronary artery disease (P = .01). By multivariate analysis, the significant joint predictors of risk were ejection fraction (P < .0005) and ischemic perfusion defect size (P = .005). The combination of ejection fraction and thallium tomography added significant incremental prognostic information to the clinical data, whereas angiography did not further improve a model that included clinical, ejection fraction, and tomographic variables.

CONCLUSIONS

Quantitative exercise 201Tl tomography provides important incremental, long-term prognostic information in patients receiving thrombolytic therapy for acute myocardial infarction.

Clinical and angiographic significance of a normal thallium-201 tomographic study in patients with a strongly positive exercise electrocardiogram

Among 23,059 patients who underwent exercise myocardial tomography between 1985 and 1994 at our institution, there were 817 (3.5%) with a strongly positive exercise electrocardiogram and normal myocardial tomograms. Among these, 52 patients had no conditions known to be associated with a false-positive exercise electrocardiogram and no previous coronary revascularization, and underwent coronary angiography. Of the 32 patients with significant coronary stenoses, 50% had 1-vessel disease and only 22% had 3-vessel disease (p < 0.05). Among 55 stenosed arteries, 56% were of moderate severity (50 to 74%), whereas only 9% had subtotal or total occlusion (95 to 100%) (p < 0.001). There was a significant gender difference in the prevalence of significant coronary stenoses (80% in male vs 24% in female patients, p < 0.0001). A strongly positive exercise electrocardiogram coupled with normal exercise myocardial tomograms is a rare clinical finding. In women, this finding is usually associated with normal coronary arteries, whereas in men it often denotes coronary artery disease, usually of mild to moderate degree.

Tolerance, hemodynamic changes, and safety of dobutamine stress perfusion imaging

BACKGROUND

Dobutamine myocardial perfusion imaging is being used increasingly for assessment of coronary artery disease. Heretofore, there have been no large series documenting its tolerance and safety. The aims of this study were to assess the tolerance, hemodynamic changes, and safety of dobutamine stress in conjunction with myocardial perfusion imaging.

METHODS AND RESULTS

The tolerance, hemodynamic changes, and safety of dobutamine myocardial perfusion imaging were investigated in a consecutive series of 1012 patients. Dobutamine was infused at incremental doses of 10, 20, 30, and 40 micrograms/kg/min at 3-minute intervals. Perfusion tomography was performed according to standard protocols with either 201Tl or 99mTc-labeled sestamibi. Seven hundred twenty-nine patients (72%) reached a maximal dobutamine dose of 40 micrograms/kg/min. Dobutamine significantly increased heart rate (76 +/- 14 beats/min to 127 +/- 20 beats/min; p < 0.001) and systolic blood pressure (141 +/- 20 mm Hg to 168 +/- 36 mm Hg; p < 0.001) from baseline to peak infusion rate. The most common side effects were chest pain (31%), headache (14%), dyspnea (12%), palpitations (10%), and flushing (10%). There was no death, myocardial infarction, pulmonary edema, ventricular fibrillation, sustained ventricular tachycardia, or cerebral vascular accident. Nonsustained ventricular tachycardia occurred in 43 patients (4.2%) but did not cause any hemodynamic instability.

CONCLUSIONS

When done with the necessary caution, dobutamine myocardial perfusion imaging is a safe diagnostic test, although side effects are common.

Assessment of myocardial viability with 99mTc sestamibi in patients undergoing cardiac transplantation. A scintigraphic/pathological study

BACKGROUND

99mTc sestamibi and 201 Tl are tracers that allow equivalent detection of myocardial infarction. However, because sestamibi does not undergo as much time-dependent redistribution as does 201Tl, it has been considered suboptimal for the detection of myocardial viability.

METHODS AND RESULTS

Fifteen consecutive patients with ischemic cardiomyopathy who underwent orthotopic cardiac transplantation received an intravenous injection of 99mTc sestamibi at 1 to 6 hours before transplantation. Rotational tomography of the excised, intact, native hearts was performed to quantify the extent of myocardial hypoperfusion. The hearts were then sliced and reimaged on a gamma camera, followed by pathological quantification of the extent and severity of scarred and normal myocardium. Samples of normally and abnormally perfused myocardium underwent gamma well counting to determine tissue radioactivity and were examined under light microscopy for delineation of myocardial structure after trichrome staining. The mean extent of scintigraphic scar quantified through the use of rotational tomography was 45 +/- 14% of the left ventricle and correlated closely with pathological scar size (r = .89), despite a slight overestimation. Scintigraphic scar size determined with planar imaging of the individual myocardial slices also correlated closely with pathological scar size (r = .88). A good correlation existed between tissue 99mTc sestamibi activity determined through well counting and histological evidence of myocardial viability (r = .89). Most hypokinetic and 40% of akinetic/dyskinetic myocardial segments contained scintigraphically and histologically normal myocardium.

CONCLUSIONS

99mTc sestamibi scintigraphy can be used to accurately quantify the extent of myocardial scarring. Furthermore, the relative sestamibi activity in perfusion defects, measured several hours after administration, is a good indicator of myocardial viability determined with microscopy.

Detection of left anterior descending coronary artery stenosis in patients with left bundle branch block: exercise, adenosine or dobutamine imaging?

OBJECTIVES

This study sought to assess the diagnostic value of myocardial perfusion imaging during exercise and pharmacologic stress in patients with left bundle branch block.

BACKGROUND

Patients with left bundle branch block often have septal perfusion defects during exercise perfusion tomography that mimic defects caused by coronary artery disease. These defects appear to be less frequent during pharmacologic stress using adenosine or dipyridamole. Data are scantly on the value of dobutamine tomography in these patients.

METHODS

We studied 383 consecutive patients with left bundle branch block referred for perfusion scintigraphy over a 5-year span. Perfusion tomography was performed in conjunction with exercise in 206 patients, adenosine in 127 and dobutamine in 50. Coronary angiography was performed within 1 month of the nuclear study in 77, 50 and 27 patients, respectively.

RESULTS

Exercise, adenosine and dobutamine tomography had similar sensitivity and specificity for the detection of > 50% stenosis in the left circumflex (74% and 96%; 50% and 100%; 63% and 91%, respectively) and right coronary arteries (96% and 86%; 82% and 91%; 79% and 100%, respectively) and similar sensitivity for left anterior descending coronary artery stenosis (88%, 79% and 100%, respectively). However, the false-positive rate for septal defects was higher by exercise tomography (26 [46%] of 57) than by pharmacologic methods (5 [10%] of 48, p < 0.001), and there was no significant difference between adenosine (4 [11%] of 35) and dobutamine (1 [8%] of 13, p = 0.7). The specificity and predictive value of a positive test response for left anterior descending coronary artery stenosis were 36% and 51% for exercise compared with 81% and 85% for adenosine (p < or = 0.001) and 80% and 90% for dobutamine (p < 0.05), respectively.

CONCLUSIONS

In patients with left bundle branch block, pharmacologic stress is more specific than exercise tomography in the diagnosis of left anterior descending coronary artery stenosis. Dobutamine and adenosine tomography appear to be equally specific in these patients.

Simultaneous perfusion tomography and radionuclide angiography during dobutamine stress

The purpose of this investigation was to evaluate the changes in left ventricular function and volumes concurrently with tomographic myocardial perfusion during dobutamine infusion.

METHODS

Ninety-two patients underwent first-pass radionuclide angiography using a multicrystal gamma camera and myocardial tomography after high-dose (40 micrograms/kg/min) dobutamine infusion and 99mTc-sestamibi administration.

RESULTS

Dobutamine increased systolic blood pressure (p < 0.0001), heart rate (p < 0.00017), left ventricular ejection fraction (p = 0.0001), cardiac output (p = 0.0001) and stroke volume (p = 0.042). The end-diastolic (p = 0.009) and end-systolic volumes (p = 0.0007) significantly decreased. Of 38 patients with cardiac catheterization, 28 had significant coronary artery disease and 10 had normal coronaries. The sensitivity and specificity for coronary artery disease detection by myocardial perfusion tomography were 78% and 90%, respectively. By radionuclide angiography, only 9 of 27 coronary artery disease patients experienced deterioration of wall motion during dobutamine (sensitivity 33%).

CONCLUSION

Changes in myocardial perfusion are more sensitive than changes in left ventricular function for detecting coronary artery disease during dobutamine stress.

Diagnostic utility of tomographic myocardial perfusion imaging with technetium 99m furifosmin (Q12) compared with thallium 201: results of a phase III multicenter trial

BACKGROUND

Based on physical properties, 99mTc-labeled perfusion agents offer several advantages over 201Tl for myocardial perfusion imaging. The results of in vivo and experimental studies, along with preliminary experience in human subjects, have shown 99mTc-labeled furifosmin to be a promising new perfusion tracer. The purpose of this study was to evaluate the safety of a new myocardial perfusion agent, 99mTc-labeled furifosmin (Q12), and determine the concordance of furifosmin perfusion scintigraphy to 201Tl imaging. In addition, we sought to determine the normalcy rate of myocardial scintigraphy with furifosmin.

METHODS AND RESULTS

One hundred fifty patients constituted the study group in this multicenter trial. Patients underwent exercise testing with furifosmin injected at peak exercise, and tomographic imaging was begun 15 to 30 minutes afterward. After a separate injection, resting images were obtained 3 to 4 hours later. Thallium scintigraphy was performed within 2 weeks of the furifosmin scans, after a similar exercise workload. Patients with a low likelihood of coronary artery disease (n = 39) also underwent furifosmin imaging. All images were processed and displayed in uniform manner and interpreted by a panel of readers. No adverse effects or clinically important laboratory alterations were related to furifosmin imaging. Image quality was slightly better with furifosmin than with thallium. The overall concordance between the perfusion studies was 86% (kappa value = 0.669). The normalcy rate for furifosmin scintigraphy was 100%.

CONCLUSIONS

99mTc-labeled furifosmin is a promising new 99mTc-labeled myocardial perfusion agent, providing diagnostic results similar to those obtained with 201Tl.

Preoperative risk stratification by adenosine thallium 201 single-photon emission computed tomography in patients undergoing vascular surgery

BACKGROUND

Adenosine perfusion scintigraphy is a powerful technique for diagnosing coronary artery disease and risk stratifying patients with recent myocardial infarction.

METHODS AND RESULTS

We investigated the use of adenosine 201Tl tomography to risk stratify 106 patients undergoing vascular arterial reconstruction consisting of lower limb arterial grafting in 44, aortic aneurysmectomy in 36, and carotid endarterectomy in 26 patients. Abnormal tomograms occurred in 57 patients (54%), 47 (82%) of whom had reversible perfusion defects. There were three postoperative deaths, all in the group that underwent aortic aneurysmectomy. Another patient with an aortic aneurysm had unstable angina and one patient who underwent lower limb arterial surgery had pulmonary edema after surgery. No patient without transient defects had an event (negative predictive value 100%). Cardiac events occurred only in patients with transient perfusion defects. However, only 5 of 47 such patients had events (positive predictive value 11%). The perfusion defect size (23% +/- 14% vs 8.9% +/- 135; p = 0.034) and the ischemic fraction (20% +/- 16% vs 5.6% +/- 8.9%; p = 0.009) were 2.5- and 3.5-fold larger, respectively, in patients with than in those without events. A history of diabetes mellitus or previous infarction did not enhance the predictive value of the test.

CONCLUSION

Thus absence of reversible hypoperfusion during adenosine scintigraphy ensures virtual absence of postoperative cardiac events. Patients undergoing aortic aneurysmectomy may be targeted preferentially for risk-stratification strategies in the future.

Exercise thallium-201 single photon emission computed tomography for evaluation of coronary artery bypass graft patency

Thallium-201 single photon emission computed tomography (SPECT) is superior to planar imaging for localizing native coronary stenoses, but has not yet been studied for assessing graft patency late after coronary artery bypass graft surgery (CABG). Accordingly, we studied 50 patients (40 males), aged 58 +/- 9 years (mean +/- SD), who presented for evaluation of angina (30 patients), atypical chest pain (20 patients), and other symptoms (9 patients), late after CABG (51 +/- 47 months). Patients with prior myocardial infarction were excluded. The mean ejection fraction was 58 +/- 17%. All patients underwent coronary angiography within 3 weeks of symptom-limited exercise thallium-201 SPECT. There were 119 grafts, of which 48 had > 50% stenosis by angiography. Thallium-201 SPECT detected 40 of these 48 (83%) stenosed grafts. The sensitivity of thallium-201 SPECT for detecting any graft stenosis was higher than that of the exercise electrocardiogram in patients with typical recurrent angina (84% vs 24%, p < 0.0001), as well as in those with atypical symptoms (70% vs 50%, p = 0.0039). The sensitivity of thallium-201 SPECT for correctly localizing the graft stenosis site was 82% for the left anterior descending, 92% for the right coronary, and 75% for the circumflex coronary artery. In conclusion, exercise thallium-201 SPECT is an excellent method to detect and localize graft stenosis late after CABG; it is far superior to the exercise electrocardiogram alone, both in patients with and without typical recurrent angina.