A. Iain McGhie

Regional cardiac adrenergic function using I-123 meta-iodobenzylguanidine tomographic imaging after acute myocardial infarction

The effect of acute myocardial infarction (AMI) on regional cardiac adrenergic function was studied in 27 patients mean +/- standard deviation 10 +/- 4 days after AMI. Regional adrenergic function was evaluated noninvasively with I-123 meta-iodobenzylguanidine (MIBG) using a dedicated 3-detector tomograph. Four hours after its administration, there was reduced MIBG uptake in the region of infarction, 0.38 +/- 0.31 counts/pixel/mCi x 103 compared with 0.60 +/- 0.30 counts/pixel/mCi x 103 and 0.92 +/- 0.35 counts/pixel/mCi x 103 in the zones bordering and distant from the infarct area, respectively, p less than 0.001. In all patients, the area of reduced MIBG uptake after 4 hours was more extensive that the associated thallium-201 perfusion defect with defect scores of 52 +/- 22 and 23 +/- 18%, respectively, p less than 0.001. After anterior wall AMI, the 4-hour MIBG defect score was 70 +/- 13% and the degree of mismatch between myocardial perfusion and MIBG uptake was 30 +/- 9% compared with 39 +/- 17 and 21 +/- 17% after inferior AMI, p less than 0.001 and p = 0.016, respectively. The 4-hour MIBG defect score correlated inversely with the predischarge left ventricular ejection fraction, r = -0.73, p less than 0.001. Patients with ventricular arrhythmia of greater than or equal to 1 ventricular premature complexes per hour, paired ventricular premature complexes or ventricular tachycardia detected during the late hospital phase had higher 4-hour MIBG defect scores, 62.5 +/- 15.0%, than patients with no detectable complex ventricular ectopic activity and a ventricular premature complex frequency of less than 1 per hour, 44.6 +/- 23.4%, p = 0.036.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of angioscopy, intravascular ultrasound imaging and quantitative coronary angiography in predicting clinical outcome after coronary intervention in high risk patients

OBJECTIVESnThe purpose of this study was to identify qualitative or quantitative variables present on angioscopy, intravascular ultrasound imaging or quantitative coronary arteriography that were associated with adverse clinical outcome after coronary intervention in high risk patients.nnnBACKGROUNDnPatients with acute coronary syndromes and complex lesion morphology on angiography are at increased risk for acute complications after coronary angioplasty. Newer devices that primarily remove atheroma have not improved outcome over that of balloon angioplasty. Intravascular imaging can accurately identify intraluminal and intramural histopathologic features not adequately visualized during coronary arteriography and may provide mechanistic insight into the pathogenesis of abrupt closure and restenosis.nnnMETHODSnSixty high risk patients with unstable coronary syndromes and complex lesions on angiography underwent angioscopy (n = 40) and intravascular ultrasound imaging (n = 46) during interventional procedures. In 26 patients, both angioscopy and intravascular ultrasound were performed in the same lesion. All patients underwent off-line quantitative coronary arteriography. Coronary interventions included balloon (n = 21) and excimer laser (n = 4) angioplasty, directional (n = 19) and rotational (n = 6) atherectomy and stent implantation (n = 11). Patients were followed up for 1 year for objective evidence for recurrent ischemia.nnnRESULTSnPatients whose clinical presentation included rest angina or acute myocardial infarction or who received thrombolytic therapy within 24 h of procedure were significantly more likely to experience recurrent ischemia after intervention. Plaque rupture or thrombus on preprocedure angioscopy or angioscopic thrombus after intervention were also significantly associated with adverse outcome. Qualitative or quantitative variables on angiography, intravascular ultrasound or off-line quantitative arteriography were not associated with recurrent ischemia on univariate analysis. Multivariate predictors of recurrent ischemia were plaque rupture on preprocedure angioscopy (p < 0.05, odds ratio [OR] 10.15) and angioscopic thrombus after intervention (p < 0.05, OR 7.26).nnnCONCLUSIONSnAngioscopic plaque rupture and thrombus were independently associated with adverse outcome in patients with complex lesions after interventional procedures. These features were not identified by either angiography or intravascular ultrasound.

Searching for Hibernating Myocardium Time to Reevaluate Investigative Strategies

He wakes, he lives, tis death is dead not he. —Percy Bysshe ShellynnIn the early 1980s, development of clinical methods for coronary revascularization (CABG/PTCA) was rapidly followed by presentation of data that indicated that dysfunctional myocardial segments supplied by vessels with reduced or seemingly absent flow could often recover function after flow was restored. The term “hibernating” has been used to describe myocytes that reside in regions that receive blood flow sufficient to support the low energy–requiring functions needed to maintain structural integrity but inadequate to sustain the high-energy requirements of contraction.1 The recognition that such regions exist and that clinical recovery is possible is particularly important in patients with poor ventricular function and has driven research for reliable, noninvasive methods to detect hibernation. A variety of such techniques is available and can be broadly divided into two groups2 3 : (1) radioactive tracers of perfusion that depend on the integrity of the sarcolemmal membrane for myocardial uptake and retention (eg, 201Tl or 82Rb) or on preservation of myocardial metabolism (eg, [18F] fluorodeoxyglucose [FDG]) to indicate viability and (2) stimulants of inotropic reserve, of which the most widely used is low-dose dobutamine stress echocardiography (LDDSE). Thus the nuclear techniques, with which there is greater experience, evaluate structural viability, whereas LDDSE defines viability on the basis of functional recovery. When assessing these techniques, it is important to remember that inherent in the definition of hibernation is ultimate recovery in function. Therefore, it is only after function has been restored that the effects of ischemia can be shown to have been transient and that the dysfunctional myocardium can be confirmed to have been hibernating. LDDSE, which predicts that function can recover, would appear to be a more direct predictor of functional recovery, but there has …

Regadenoson pharmacologic rubidium-82 PET: A comparison of quantitative perfusion and function to dipyridamole

BackgroundDipyridamole is used for stress 82rubidium chloride (82RbCl) PET because of its long hyperemic duration. Regadenoson has advantages of a fixed dose and favorable symptom profile, but its mean maximal hyperemia is only 2.3xa0minutes. To determine its suitability for 82RbCl PET, we imaged subjects using a regadenoson protocol based on its hyperemic response and compared the images in the same subjects having dipyridamole PET.MethodsIn 32 subjects (23 M), we assessed visually by blinded interpretation and quantitatively compared summed stress and difference scores, total perfusion deficit (TPD), LVEF, LV volumes, and change in stress-rest function. Linear correlation and Bland-Altman analysis of the paired measurements were applied for evaluation of differences. Paired t test and Pearson’s correlation were applied for testing of significance.ResultsThe images were interpreted the same by visual assessment. Twenty-six (26) subjects had reversible defects; by quantitation the SSS was 12.9xa0±xa07.0 and 14.1xa0±xa06.4 (Pxa0=xa0.23) and SDS was 7.0xa0±xa06.8 versus 7.6xa0±xa06.2 (Pxa0=xa0.40) for dipyridamole and regadenoson, respectively. Six (6) subjects had <5% likelihood of CAD and were normal by both. All paired measurements showed a high positive correlation between regadenoson and dipyridamole; stress segmental perfusion Regxa0=xa00.93Dipxa0+xa04.4, rxa0=xa00.88; TPD Regxa0=xa00.94Dipxa0+xa00.41, rxa0=xa00.93; LVEF Regxa0=xa00.92Dipxa0+xa04.7, rxa0=xa00.95; stress minus rest LVEF Regxa0=xa00.87Dipxa0−xa00.99, rxa0=xa00.82.ConclusionRegadenoson stress 82RbCl PET perfusion defect and cardiac function measurements are visually and quantitatively equivalent to dipyridamole studies and can be obtained with the clinical advantages of regadenoson.

Reduction of SPECT MPI Radiation Dose Using Contemporary Protocols and Technology

The nuclear cardiology field embarked several years ago on an aggressive effort to reduce radiation exposure for single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) [(1)][1]. Several reports suggest substantial lag in the adoption of radiation-sparing approaches [(2