Absolute myocardial flow quantification with (82)Rb PET/CT: comparison of different software packages and methods.

PURPOSE: In clinical cardiac (82)Rb PET, globally impaired coronary flow reserve (CFR) is a relevant marker for predicting short-term cardiovascular events. However, there are limited data on the impact of different software and methods for estimation of myocardial blood flow (MBF) and CFR. Our objective was to compare quantitative results obtained from previously validated software tools. METHODS: We retrospectively analyzed cardiac (82)Rb PET/CT data from 25 subjects (group 1, 62 ± 11 years) with low-to-intermediate probability of coronary artery disease (CAD) and 26 patients (group 2, 57 ± 10 years; P=0.07) with known CAD. Resting and vasodilator-stress MBF and CFR were derived using three software applications: (1) Corridor4DM (4DM) based on factor analysis (FA) and kinetic modeling, (2) 4DM based on region-of-interest (ROI) and kinetic modeling, (3) MunichHeart (MH), which uses a simplified ROI-based retention model approach, and (4) FlowQuant (FQ) based on ROI and compartmental modeling with constant distribution volume. RESULTS: Resting and stress MBF values (in milliliters per minute per gram) derived using the different methods were significantly different: using 4DM-FA, 4DM-ROI, FQ, and MH resting MBF values were 1.47 ± 0.59, 1.16 ± 0.51, 0.91 ± 0.39, and 0.90 ± 0.44, respectively (P<0.001), and stress MBF values were 3.05 ± 1.66, 2.26 ± 1.01, 1.90 ± 0.82, and 1.83 ± 0.81, respectively (P<0.001). However, there were no statistically significant differences among the CFR values (2.15 ± 1.08, 2.05 ± 0.83, 2.23 ± 0.89, and 2.21 ± 0.90, respectively; P=0.17). Regional MBF and CFR according to vascular territories showed similar results. Linear correlation coefficient for global CFR varied between 0.71 (MH vs. 4DM-ROI) and 0.90 (FQ vs. 4DM-ROI). Using a cut-off value of 2.0 for abnormal CFR, the agreement among the software programs ranged between 76 % (MH vs. FQ) and 90 % (FQ vs. 4DM-ROI). Interobserver agreement was in general excellent with all software packages. CONCLUSION: Quantitative assessment of resting and stress MBF with (82)Rb PET is dependent on the software and methods used, whereas CFR appears to be more comparable. Follow-up and treatment assessment should be done with the same software and method.

Incremental value of left ventricular systolic and diastolic function to determine outcome in patients with acute ST-segment elevation myocardial infarction: the echocardiographic substudy of the OASIS-6 trial.

BACKGROUND: The echocardiographic substudy of the OASIS-6 trial evaluated the prognostic implications of left ventricle (LV) systolic and diastolic dysfunction early postacute ST-segment elevation myocardial infarction (STEMI) in patients treated with fondaparinux versus usual care. METHODS: Comprehensive echocardiograms were performed a median of 6 days after the index STEMI in 528 patients, 258 randomized to fondaparinux and 270 to usual care (unfractionated heparin or placebo), to assess LV systolic and diastolic function, LV mass, and LV end-systolic and end-diastolic volumes. A total of 245 (46.4%) patients were followed up for 3 months and 283 (53.6%) for 6 months. Major cardiac events (MACE) were defined as the composite of death, reinfarction, heart failure, or cardiogenic shock and resuscitated cardiac arrest. RESULTS: Patients with LV ejection fraction (LVEF) ≤ 45% and restrictive diastolic function (RDF) were at greatly increased risk of MACE (hazard ratio [HR] = 8.85, 95% CI, 4.21­18.60) compared to patients with LVEF ≥ 45% and without RDF. RDF remained a strong predictor for MACE in patients with LVEF ≥ 45% (HR = 4.38, 95% CI, 1.52­12.60) and in multivariate models adjusted for LVEF, LV end-systolic volume, and clinical variables. CONCLUSION: In this large international trial, LV systolic and diastolic function, as determined by echocardiography early following STEMI, are incremental predictors of MACE. In addition, RDF is a strong independent predictor of MACE after STEMI across a broad range of LVEF.

Cardiac PET/CT misregistration causes significant changes in estimated myocardial blood flow.

UNLABELLED: Misregistration of cardiac PET/CT data can lead to misinterpretation of regional myocardial perfusion. However, the effect of misregistration on the quantification of myocardial blood flow (MBF) has not been studied. METHODS: Cardiac (82)Rb-PET/CT scans of 10 patients with normal regional myocardial perfusion were analyzed. Realignment was done for the baseline and stress PET/CT images as necessary, and MBF was obtained from dynamic data. Then, the stress images were misregistered by 5 mm along the x-axis (left) and z-axis (cranial) and again by 10 mm. A 10-mm misregistration in the opposite direction (-10 mm along the x-axis [right] and z-axis [caudal]) was also tested. Stress MBF was recalculated for 5-, 10-, and -10-mm misregistrations. RESULTS: Stress MBF of the left ventricle decreased by 10% ± 6% (P = 0.005) after 5-mm misregistration and by 24% ± 15% (P = 0.001) after 10-mm misregistration. In descending order, the most important stress MBF changes occurred in the anterior (39% ± 9%), lateral (34% ± 9%), apical (20% ± 16%), inferior (12% ± 10%), and septal (10% ± 12%) walls after 10-mm misregistration. Lesser changes were observed after 5-mm misregistration, with the same wall distribution. In contrast, -10-mm misregistration increased global MBF by 9% ± 6% (P = 0.004). In descending order, the overestimation of estimated MBF after -10-mm misregistration occurred in the lateral (15% ± 8%), apical (15% ± 18%), anterior (9% ± 5%), and inferior (9% ± 11%) walls. CONCLUSION: Misregistration of the stress PET/CT dataset leads to significant global and regional artifactual alterations in the estimated MBF. Quantitative error was observed throughout the myocardium and was not confined to those heart regions that extended into the lung on misregistered CT.

Relationship of delayed enhancement by magnetic resonance to myocardial perfusion by positron emission tomography in hypertrophic cardiomyopathy.

BACKGROUND: Presence of delayed enhancement (DE) on cardiac magnetic resonance (CMR) is associated with worse clinical outcomes in hypertrophic cardiomyopathy. We investigated the relationship between DE on CMR and myocardial ischemia in hypertrophic cardiomyopathy. METHODS AND RESULTS: Hypertrophic cardiomyopathy patients (n=47) underwent CMR for assessment of DE and vasodilator stress ammonia positron emission tomography to quantify myocardial blood flow and coronary flow reserve. The summed difference score for regional myocardial perfusion was also assessed. Patients in the DE group (n=35) had greater left ventricular wall thickness (2.09±0.44 versus 1.78±0.34 cm; P=0.03). Stress myocardial blood flow (2.25±0.46 versus 1.78±0.43 mL/min per gram; P=0.01) and coronary flow reserve (2.78±0.32 versus 2.01±0.52; P<0.001) were significantly lower in DE-positive patients. Summed difference score (7.3±6.6 versus 0.9±1.4; P<0.0001) was significantly higher in patients with DE. A coronary flow reserve <2.00 was seen in 18 patients (51%) with DE but in none of the DE-negative patients (P<0.0001). CMR and positron emission tomography showed visually concordant DE and regional myocardial perfusion abnormalities in 31 patients and absence of DE and perfusion defects in 9 patients. Four DE-positive patients demonstrated normal regional myocardial perfusion, and 3 DE-negative patients had (apical) regional myocardial perfusion abnormalities. CONCLUSIONS: We found a close relationship between DE by CMR and microvascular function in most of the patients studied. However, a small proportion of patients had DE in the absence of perfusion abnormalities, suggesting that microvascular dysfunction and ischemia are not the sole causes of DE in hypertrophic cardiomyopathy patients.

Intracardiac shunt with hypoxemia caused by right ventricular dysfunction following pericardiocentesis.

Significant hypoxemia can result from right-to-left intracardiac shunting through a patent foramen ovale, an atrial septal defect or a ventricular septal defect. Pulmonary embolus, congenital heart disease and pericardial tamponade are well-recognized causes of right-to-left shunting. However, right-to-left shunting can also follow pericardiocentesis. A case of profound hypoxemia caused by right ventricular hypokinesis precipitated by pericardial tap is reported. This under-recognized entity can be responsible for significant morbidity in the critical care setting. The clinical presentation, natural history, diagnosis and treatment of hypoxemia caused by intracardiac shunt following pericardiocentesis are discussed.

The Venture-balloon crush technique to treat a severely angulated bifurcation lesion via the radial approach--lessons learned.

We present the first described use of the Venture (St. Jude Medical Inc.) catheter to accomplish balloon crush stenting of a severely angulated bifurcation via the radial approach. We outline the lessons learned and pitfalls of performing percutaneous intervention to severely angulated bifurcations such as this one.

Ostial RCA intervention: guiding catheter challenges and use of a buddy wire to perform focused-force angioplasty on a severely calcific ostial right coronary lesion.

Ostial coronary disease presents a challenge from multiple perspectives with regard to percutaneous intervention. We present a novel case of a technically challenging ostial right coronary artery calcified lesion with a bar of calcium at the aorto-ostial junction which prevented intubation with multiple guiding catheters. We describe the use of a buddy wire as a technique for focused-force angioplasty with slow incremental balloon inflation of increasing diameter for plaque modification prior to stenting in a situation where rotational atherectomy and cutting balloon angioplasty were not an option.