Classification of ischemic dysfunctional myocardium combining perfusion quantification and contractile reserve evaluation using nitrate-enhanced gated single photon emission computed tomography with dobutamine test.

AIM: In patients with ischemic cardiomyopathy, the differentiation of dysfunctional myocardium in scarred versus hibernating is oversimplified. We evaluated a more complex classification using an imaging technique currently employed for viability detection, having as reference the postrevascularization outcome of dysfunctional segments. METHODS: In 35 patients, we performed gated single-photon emission computed tomography (SPECT) (resting and nitrate-enhanced study, the latter with baseline and dobutamine acquisition) before revascularization. The outcome after revascularization was assessed by repeating resting gated SPECT. Dysfunctional segments without functional recovery in postrevascularization gated SPECT were defined scar (either nontransmural or transmural according to tracer activity); those with recovery were divided in stunned (unchanged uptake) or hibernating (improved postrevascularization activity). This reference classification was compared with the categorization based on prerevascularization gated SPECT. RESULTS: Contractile reserve in dobutamine gated SPECT differentiated scarred from viable segments with 78% accuracy. Tracer activity in nitrate imaging distinguished the degree of transmurality. Nitrate-induced activity increase was significantly higher (p<0.0001) in the hibernating segments (14.9+/-20.4%) than in transmural (4.8+/-13.4%) nontransmural scars (3.3+/-13%), or stunned segments (2.2+/-8%). The presence or absence of nitrate-induced activity increase predicted the postrevascularization perfusion changes in viable myocardium and differentiated hibernating from stunned segments. The prerevascularization classification showed a good agreement with the reference categorization (kappa=0.50). Conclusion. Combining contractile reserve evaluation and perfusion quantification within a single study with baseline-nitrate gated SPECT and dobutamine test it is possible to achieve a comprehensive classification of dysfunctional segments.

Usefulness of distinct activity thresholds according to baseline regional asynergy for predicting functional recovery in patients with chronic coronary artery disease and left ventricular dysfunction: a study with nitrate-enhanced sestamibi gated SPECT.

BACKGROUND: The role of gated single photon emission computed tomography (SPECT) in improving viability detection with the use of perfusion imaging is uncertain. This study aimed to verify whether the classification of baseline regional dysfunction with gated SPECT helps to predict functional recovery with the use of quantitative perfusion imaging. METHODS AND RESULTS: Resting nitrate-enhanced sestamibi gated SPECT was performed in 31 patients with left ventricular dysfunction, who later underwent coronary revascularization. With the use of a 16-segment model, tracer activity was quantified, and wall motion and thickening were estimated with a 4-point scoring scheme. Reversible dysfunction was assessed with follow-up gated SPECT. According to receiver operating characteristic curve analysis, the best overall cutoff for predicting reversible dysfunction in asynergic segments was 50% of peak activity or greater, with 83% sensitivity, 54% specificity, and 64% accuracy. When the segments were divided according to wall motion in resting gated SPECT, the optimal activity cutoff was greater than 68% for hypokinetic and 50% or greater for adyskinetic segments. With the use of 2 thresholds, the overall sensitivity remained good (76%), whereas specificity increased to 73% (P <.0005) and accuracy to 74% (P <.02). CONCLUSIONS: Regional dysfunction assessment directly on perfusion images permits use of different activity thresholds with an improvement over a single cutoff for all asynergic segments. Therefore combining perfusion and functional data with nitrate-enhanced gated SPECT at rest appears to be a promising approach for viability detection.

Prediction of functional recovery in patients with chronic coronary artery disease and left ventricular dysfunction combining the evaluation of myocardial perfusion and of contractile reserve using nitrate-enhanced technetium-99m sestamibi gated single-photon emission computed tomography and dobutamine stress.

This study aimed to assess whether contractile reserve evaluation using dobutamine gated single-photon emission computed tomography (SPECT) improves the capability of quantitative perfusion analysis to predict functional recovery of viable hibernating myocardium. Resting and dobutamine nitrate-enhanced technetium-99m sestamibi (sestamibi) gated SPECT studies were performed in patients with coronary artery disease who had left ventricular dysfunction. Tracer activity was quantified, and wall motion and thickening visually scored. Reversible dysfunction was identified with gated SPECT repeated after coronary revascularization. Using the best activity threshold, perfusion quantification achieved 85% sensitivity and 55% specificity. Contractile reserve detection was significantly less sensitive (64%, p <0.0005), but more specific (88%, p <0.00001) than perfusion quantification. However, in the subgroup of hypokinetic segments, the sensitivity of contractile reserve assessment was just slightly lower than perfusion quantification (72% vs 91%, p = NS), whereas specificity was significantly higher (94% vs 23%, p <0.00001). Conversely, in the adyskinetic segments, perfusion quantification was significantly more sensitive than contractile reserve (82% vs 59%, p <0.005), but similarly specific (76% vs 85%, p = NS). Therefore, the identification of reversible dysfunction based on perfusion quantification in adyskinetic segments and on contractile reserve detection in hypokinetic segments was significantly more specific (83% vs 55%, p <0.00001) than standard quantitative perfusion SPECT, without major loss in sensitivity (78% vs 85%, p = NS). In conclusion, contractile reserve evaluation using dobutamine gated SPECT enhances the reliability of nitrate-enhanced sestamibi SPECT when used to predict reversible dysfunction in hypokinetic segments, whereas perfusion quantification remains superior in adyskinetic segments.

Nitrate-enhanced gated technetium 99m sestamibi SPECT for evaluating regional wall motion at baseline and during low-dose dobutamine infusion in patients with chronic coronary artery disease and left ventricular dysfunction: comparison with two-dimensional echocardiography.

BACKGROUND: The value of gated single photon emission computed tomography (SPECT) in the assessment of wall motion (WM) in patients with severe perfusion defects and in the evaluation of low-dose dobutamine (LDD)-induced changes is not yet established. In patients with chronic coronary artery disease who have left ventricular (LV) dysfunction, the results of nitrate-enhanced technetium 99m sestamibi (sestamibi) gated SPECT for the evaluation of resting and LDD WM were compared with those of baseline and LDD echocardiography (LDDE). METHODS AND RESULTS: Thirty-seven patients underwent echocardiography and nitrate-enhanced sestamibi gated SPECT within 1 week at rest and during LDD infusion. WM was scored from 1 (normal) to 4 (dyskinetic) by using a 16-segment model. Segments with sestamibi uptake less than 30% were considered unsuitable for WM analysis (36 of 592 segments). Echocardiography was technically unreliable in 10 of 592 segments. The precise agreement between echocardiography and gated SPECT for baseline regional WM was 68.4% (kappa = 0.54), without significant differences for the involved coronary artery territory. The agreement for +/- 1 WM scoring was 96.5% (kappa = 0.94). Contractile reserve during LDD was detected by means of echocardiography in 36% and by means of sestamibi gated SPECT in 33% of baseline asynergic segments. Agreement for detection of WM improvement in response to LDD was 74% (kappa = 0.41). The overall and +/-1 WM score agreement for LDD WM was 67.5% (kappa = 0.50) and 94.7% (kappa = 0.91), respectively. A significant correlation between echocardiography and gated SPECT was observed for both baseline (p = 0.78) and LDD (p = 0.74) WM score index. CONCLUSIONS: In patients with coronary artery disease who have LV dysfunction, nitrate-enhanced sestamibi gated SPECT allows a reliable WM evaluation, both at rest and during LDD infusion, in almost all segments and provides results in agreement with LDDE.

Comparison of baseline and low-dose dobutamine technetium-99m sestamibi scintigraphy with low-dose dobutamine echocardiography for predicting functional recovery after revascularization.

Injection of sestamibi during low-dose dobutamine (LDD) infusion might improve tracer ability to detect viable myocardium. This study investigated the potential value of LDD technetium-99m sestamibi (sestamibi) single-photon emission computed tomography (SPECT) in predicting functional recovery after revascularization by comparing its results with those of sestamibi SPECT at rest and of LDD echocardiography. Before revascularization, 23 patients with chronic coronary artery disease and regional left ventricular dysfunction underwent sestamibi SPECT at rest and, on a separate day, LDD echocardiography and sestamibi SPECT with tracer injection during LDD infusion. Echocardiography at rest was repeated after revascularization. Semiquantitative sestamibi uptake results (grading from 0 = normal to 4 = absent) and wall motion (grading from 1 = normal to 4 = dyskinesia) were evaluated with a 16-segment model. The ventricular wall was divided into 3 vascular territories. At follow-up, 20 of 32 asynergic vascular territories showed functional recovery, whereas 12 showed no changes. For prediction of functional recovery, LDD SPECT achieved better accuracy than SPECT at rest (87% vs 65%, p <0.05); positive and negative predictive values of LDD SPECT were 90% and 83%, respectively, which was not significantly different from the related LDD echocardiographic values (84% and 69%). Thus, LDD sestamibi SPECT appears to be a promising method for detecting myocardial viability, which provides better accuracy than sestamibi SPECT at rest, and achieves predictive values comparable to those of LDD echocardiography.

[Changes in myocardial Tc-99m-sestamibi uptake in asynergic territories during low-dose echo-dobutamine test]. / Modificazioni della captazione miocardica di Tc-99m-sestamibi in territori asinergici durante test eco-dobutamina a bassa dose.

BACKGROUND: Recent data suggest that contractile reserve in dysfunctional but viable myocardium during low-dose dobutamine infusion might be elicited not only by a direct inotropic stimulation but also by an increase in coronary blood flow. Aim of the study was to evaluate the effects of low-dose dobutamine on myocardial perfusion and function in asynergic but viable myocardium. METHODS: Nineteen patients with coronary artery disease and severe regional dysfunction were studied. Both regional ventricular function and myocardial perfusion were assessed at rest (PRE), during low-dose dobutamine (DOB) and, in twelve patients, after revascularization (POST). Regional ventricular function was evaluated with two-dimensional echocardiography using a score index ranging from 1 to 4. Myocardial perfusion was studied using Tc-99m-sestamibi Single Photon Emission Tomography (SPET); uptake defects were graded from 0 (normal) to 4 (absent uptake). For both evaluations the left ventricle was divided in 16 segments and two vascular territories were considered. RESULTS: Low-dose dobutamine elicited contractile reserve in 12 of 24 asynergic vascular territories (DOB+). Compared with PRE scintigraphy, DOB SPET showed perfusion improvement in 10/12 DOB+ and in 3/12 DOB- asynergic territories (p = 0.006). Mean uptake score decrease significantly in DOB+ (from PRE SPET 21.0 +/- 7.2 to DOB SPET 17.6 +/- 7.1; p = 0.0005) but not in DOB- (from SPET PRE 19.0 +/- 5.3 to SPET DOB 19.5 +/- 6.8, p = NS) abnormal territories. Fourteen asynergic territories underwent revascularization. Among them, 9 showed functional recovery after intervention (viable myocardium) and 5 showed no changes (fibrotic myocardium). A functional improvement under dobutamine was observed in 7 viable and in 1 fibrotic territories. Conversely, perfusion improved under dobutamine in 8 viable and in one fibrotic territory. After revascularization the perfusion defect score decreased significantly in viable territories (from PRE SPET 22.1 +/- 7.9 to POST SPET 13.3 +/- 6.6; p = 0.00001) but not in fibrotic regions (from PRE SPET 17.8 +/- 6.0 to POST SPET 15.6 +/- 4.9). CONCLUSIONS: In asynergic myocardium contractile reserve elicited by low-dose dobutamine is associated in most cases with an improvement in Tc-99m-sestamibi uptake. This suggests a possible link between increased blood flow and functional improvement during dobutamine in viable myocardium.

[Late thrombolysis in acute myocardial infarct. Demonstration of myocardial tissue salvage by the assessment of pre- and post-thrombolytic perfusion and left ventricular function]. / Trombolisi tardiva nell'infarto miocardico acuto. Dimostrazione del salvataggio di tessuto miocardico mediante valutazione pre- e post-trombolisi della perfusione e della funzione ventricolare sinistra.

BACKGROUND: Pre and post treatment perfusion scintigraphy with Tc-99m-sestamibi is an accurate method to evaluate the effectiveness of thrombolytic therapy in patients with acute myocardial infarction. In the present study this method was used to verify whether thrombolytic therapy performed late (6 to 24 hours) after symptoms onset was still able to produce significant salvage of jeopardized myocardial tissue. METHODS: Fifteen patients (mean age 60.9 +/- 9 years) admitted to CCU 8-23 hours (mean 13.2 +/- 4 hours) after symptoms onset of their first acute myocardial infarction were studied. Both myocardial perfusion and left ventricular function were assessed before and after thrombolysis. Myocardial perfusion was studied using Tc-99m-sestamibi Single Photon Emission Tomography (SPET) before (pre-lysis SPET), 4.4 +/- 0.9 days (post-lysis SPET A) and 32 +/- 6 days (post-lysis SPET B) after thrombolysis. Uptake defects were graded from 0 to 4 using a 20-segment scheme. Regional ventricular function was evaluated using two-dimensional echocardiography before (pre-lysis ECHO), simultaneously with post-lysis SPET A (post-lysis ECHO A) and 32 +/- 4 days after treatment (post-lysis ECHO B); asynergy was graded from 1 to 4. Global left ventricular function was estimated using gated blood pool imaging and measuring the ejection fraction (EF) 5.3 +/- 1 (GBP 1) and 32 +/- 4 days after treatment (GBP 2). Within 6-9 days of admission all patients underwent coronary angiography. RESULTS: In pre-lysis SPET all patients had uptaken defects (score range 17-52, mean 34.6 +/- 12). According to the comparison between pre-lysis SPET and post-lysis SPET A, patients were divided into two groups: 7 patients with perfusion recovery (Group I) and 8 patients with absent or minimal perfusion recovery (Group II). In Group I the mean uptaken score decreased significantly (from pre-lysis SPET 34.2 +/- 12 to post-lysis SPET A 21.7 +/- 7, p < 0.05); in Group II the uptaken score remained unchanged (from pre-lysis SPET 34.8 +/- 12 to post-lysis SPET A 33.6 +/- 12, ns). In post-lysis SPET B both groups showed a defect reduction compared to post-lysis SPET A; however, the defect score of SPET B in Group I was significantly lower than that in Group II (18.7 +/- 16 vs 30.1 +/- 10, p < 0.05). The asynergic score in pre-lysis ECHO was the same in the two groups (19.5 +/- 4); in post-lysis ECHO A no significant decrease was observed in the two groups. In post-lysis ECHO B a significant decrease was seen in Group I (14.8 +/- 5, p < 0.05 vs pre-lysis ECHO and vs post-lysis ECHO A), but not in Group II (19.8 +/- 5, ns); the asynergic score in post-lysis ECHO B was significantly lower in Group I than in Group II (p < 0.05). In GBP 1 the EF was 38% +/- 6 in Group I and 40% +/- 6 in Group II (ns). In GBP 2 a significant increase was registered in Group I (47% +/- 10, p < 0.05), whereas in Group II the EF remained unchanged (40% +/- 6, ns). Coronary angiography showed a patent infarct related vessel in all Group I patients and in 2 Group II patients (p < 0.05). CONCLUSIONS: These results show that in patients with acute myocardial infarction treated with thrombolysis late after symptoms onset it is still possible to obtain an effective reperfusion and the consequent salvage of jeopardized tissue, as demonstrated by the recovery of both regional and global left ventricular function.

[Myocardial scintigraphy with 99mTc MIBI. The use of a single-day protocol in a multiregional center: a comparison between planar and tomographic imaging]. / Scintigrafia miocardica con 99mTc MIBI. Utilizzo del protocollo single-day in un centro multizonale: confronto fra imaging planare e tomografico.

The use of a single-day protocol for 99mTc MIBI myocardial scintigraphy is particularly well-suited for the nuclear medicine departments that are the referral centres for the cardiology departments of several community hospitals. The aim of the study was to compare, in the same patient population, the diagnostic accuracy of planar and SPECT imaging with 99mTc MIBI using a single-day protocol. Thirty-nine patients (31 males and 8 females, age range 32-69 years) were studied because of effort chest pain. Of them, 7 had a pre-test probability of coronary artery disease less than 2.5%; coronary angiography demonstrated significant coronary obstructions in the remaining 32 subjects and 21 of them also had a history of previous myocardial infarction. All patients underwent 99mTc MIBI myocardial scintigraphy with acquisition of planar and SPECT images after injection of a low dose (370 MBq) at rest and after a second higher dose (1110 MBq), injected approximately four hours later during exercise stress testing. The normalcy rate in the 7 patients with low pre-test probability was 100% using both imaging techniques. For the diagnosis of previous infarction, the sensitivities of planar and SPECT images were 71% and 96% respectively. For the diagnosis of effort ischemia the sensitivity values were 34% and 88%, respectively, using planar and SPECT imaging. With regard to the classification of the diseased coronary arteries, the sensitivities of planar and SPECT studies were 42% and 79% respectively, and the related specificities were 91% and 77%. We may conclude that using a single-day protocol planar imaging seems to allow lower levels of diagnostic accuracy both for the diagnosis of effort ischemia and the classification of the diseased vessels as compared to SPECT, which appears therefore in a similar setting the imaging technique of choice.