Postoperative changes after surgical mesh hernia repair: a pitfall in interpretation of 18F-FDG PET-CT.

OBJECTIVE: A number of case reports have demonstrated FDG uptake around mesh prostheses after hernia repair surgery. This study characterizes FDG PET-CT findings after hernia repair with synthetic mesh in a series of cancer patients. MATERIALS AND METHODS: FDG PET-CT studies were reviewed for increased FDG uptake consistent with CT appearances of post-surgical hernia repair in cancer patients. The findings were correlated with clinical data and follow-up studies. RESULTS: 53 PET-CT studies in 22 patients (18 males, 31-79 years) were identified. Surgery for repair of inguinal (n = 14), ventral (n = 5) or umbilical (n = 3) hernia was performed, 4-204 months prior to PET-CT. FDG avidity was focal or linear in the region of the anterior abdominal or pelvic wall (mean SUV max 4.0 ± 2.3). Corresponding nonspecific CT findings included soft tissue thickening (n = 18), fat infiltration (n = 20) and fluid collection (n = 19) in the region of the omentum, adjacent to or in the inner abdominal or pelvic wall at the surgical site. Linear hyper-dense structures (n = 9) or metallic clips (n = 8) seen on CT suggested benign postoperative changes. In 10/12 (83.3%) patients with repeat PET-CT, FDG uptake remained unchanged, one showed more diffuse uptake and another showed reduced uptake on follow-up. There was neither significant change in CT appearance at the surgical site in these 12 patients, nor in 3 additional patients with only CT follow-up. Another 3 patients had previous CT demonstrating hernia at the same location. CONCLUSION: With increasing use of synthetic mesh, awareness of variations in FDG PET-CT appearance is important to avoid false interpretation in cancer patients.

Model-based correction for scatter and tailing effects in simultaneous 99mTc and 123I imaging for a CdZnTe cardiac SPECT camera.

An advantage of semiconductor-based dedicated cardiac single photon emission computed tomography (SPECT) cameras when compared to conventional Anger cameras is superior energy resolution. This provides the potential for improved separation of the photopeaks in dual radionuclide imaging, such as combined use of (99m)Tc and (123)I . There is, however, the added complexity of tailing effects in the detectors that must be accounted for. In this paper we present a model-based correction algorithm which extracts the useful primary counts of (99m)Tc and (123)I from projection data. Equations describing the in-patient scatter and tailing effects in the detectors are iteratively solved for both radionuclides simultaneously using a maximum a posteriori probability algorithm with one-step-late evaluation. Energy window-dependent parameters for the equations describing in-patient scatter are estimated using Monte Carlo simulations. Parameters for the equations describing tailing effects are estimated using virtually scatter-free experimental measurements on a dedicated cardiac SPECT camera with CdZnTe-detectors. When applied to a phantom study with both (99m)Tc and (123)I, results show that the estimated spatial distribution of events from (99m)Tc in the (99m)Tc photopeak energy window is very similar to that measured in a single (99m)Tc phantom study. The extracted images of primary events display increased cold lesion contrasts for both (99m)Tc and (123)I.

Can upright myocardial perfusion imaging be used alone with a solid-state dedicated cardiac camera?

AIM: The novel solid state dedicated cardiac cameras provide fast high resolution cardiac imaging. The D-SPECT camera enables semi-reclining (upright) positioning, increasing comfort and potentially reducing movement during myocardial perfusion imaging. Physicians are generally familiar with supine imaging and the different positioning in upright imaging could potentially cause diagnostic challenges. The aim of this study was to compare the upright and supine imaging for diagnostic ability to assess Physician confidence and determine any artefacts in upright imaging. METHODS: Fifty-five patients underwent myocardial perfusion imaging on the D-SPECT camera in both upright and supine positions. Where both images showed the same defects the 2 techniques were regarded as equally diagnostic. Where only one set showed a defect this was regarded as artefact and was defined as non-diagnostic. The location and cause of the artefact was recorded. RESULTS: In 13 /55 patients either form of imaging was regarded as equally diagnostic. In 24/55 the supine images revealed artefact affecting interpretation. The reasons for this were most frequently large BMI, motion and gut uptake. In 18/55 upright images were considered non-diagnostic. In 16/18 this was due to an infero-apical defect seen in female patients (14/16) with raised BMI and/or large breasts. CONCLUSION: Upright myocardial perfusion imaging on D-SPECT shows a common artefact (in up to 1/3 of cases) in the infero-apical region mainly in overweight female patients. Getting acquainted with this artefact this may increase Physician confidence in reporting, similarly as to conventional supine imaging. Indeed, some of the artefacts seen on supine imaging appear less commonly with upright imaging. Thus, upright imaging can potentially be used alone for diagnosis with D-SPECT. Performance of both supine and upright imaging can be reserved for overweight patients thereby minimizing impact on scanning time and clinical throughput in busy departments.

PET/CT for atherosclerotic plaque imaging.

Atherosclerosis is one of the leading causes of morbidity and mortality in the world. Rupture of atherosclerotic plaques and thrombi formation are the primary mechanisms of myocardial infarction or cerebrovascular accident. Angiography is considered to represent the gold standard technique for imaging of the arterial lumen. However, in recent years it has been realized that the primary determinant of the atherosclerotic plaque stability is the composition of the plaque and other imaging modalities have been suggested. The purpose of this review is to briefly summarize the knowledge accumulated to present date regarding the potential role of fluodeoxyglucose imaging in the assessment of atherosclerosis and to compare this modality to additional available imaging approaches for the detection of vulnerable plaques.

The added value of spiral computed tomographic angiography after lung scintigraphy for the diagnosis of pulmonary embolism.

OBJECTIVES: The objectives of this study were to evaluate the added clinical value of spiral computed tomographic angiography (CTA) after ventilation-perfusion lung scintigraphy (V/Q) for the management of patients with suspected pulmonary embolism (PE). METHODS: Of 987 patients who had V/Q during 2001, 64 patients (6%) had CTA performed for further evaluation. V/Q and CTA findings were retrospectively analyzed by 2 clinicians who were blinded to the patients' outcome. Patient management was determined based on clinical and V/Q data and was reassessed after the addition of CTA data. RESULTS: CTA was performed in 2 patients with normal V/Q, 16 patients with low probability, 28 patients with intermediate, 4 patients with high probability, and 14 patients with nonconclusive V/Q. Three patients (19%) with low probability, 9 (32%) with intermediate probability, 4 (29%) with nonconclusive, and 4 (100%) with high probability V/Q had PE diagnosed by CTA. CTA findings changed the management in 2 patients (13%) with low probability, 15 (54%) with intermediate probability, and 4 (29%) with nonconclusive V/Q. CONCLUSION: In our institution, V/Q remains the main imaging modality for evaluation of patients with clinically suspected PE. CTA was performed after V/Q in 6% of patients. Patients with intermediate probability and those with nonconclusive V/Q, and to a much lesser extent, patients with low probability V/Q could benefit from the addition of CTA after V/Q. In patients with normal V/Q and those with high-probability V/Q, the addition of CTA does not seem to influence patient management.

Ventricular mapping during atrial and ventricular pacing. Relationship of multipotential electrograms to ventricular tachycardia reentry circuits after myocardial infarction.

AIMS: Conduction through separated myocyte bundles causes multipotential electrograms and reentrant ventricular tachycardia. We hypothesized that without initiating tachycardia, the reentry region could be detected by analysing the change in multipotential electrograms during two different activation sequences. METHODS AND RESULTS: During catheter mapping and ablation in 16 patients with ventricular tachycardia late after infarction ventricular electrograms were recorded from 1072 sites during atrial and right ventricular paced ventricular activation. Multipotential electrograms were present during both activation sequences at 285 (27%) sites, during atrial pacing only at 159 (15%) sites and during right ventricular pacing only at 152 (14%) sites. Sites with multipotential electrograms during both activation sequences were more often related to a ventricular tachycardia circuit isthmus (43%) as compared to sites where such electrograms were present during one activation sequence (20%). Multipotential electrograms with >2 low amplitude deflections and a >100 ms difference in duration between the two activation sequences were infrequent but highly predictive of the reentry circuit. CONCLUSION: Regions with fixed multipotentials consistent with conduction block might be useful guides for ablation approaches that target large regions of the infarct, but are not sufficiently specific to be the sole guide for focal ablation approaches.

Characterisation of acute myocardial ischaemia in a canine model based on principal component analysis of unipolar endocardial electrograms.

The study presents a method for identifying endocardial electrical features relevant to local ischaemia detection at rest. The method consists of, first, normalisation of electrograms to a uniform representation; secondly, the use of principal component analysis to reduce the dimensionality of the electrogram vector space; and, thirdly, a search for a classification axis that matches the degree of ischaemia present in the tissue. Left ventricular myocardial states were assessed by echocardiography and NOGA mapping in eight dogs at baseline and then immediately after, 5h after and 3 days after occlusion of the left anterior descending coronary artery. Five principal components were required to approximate electrograms with an average error of less than 10% of the peak-to-peak amplitude. Correlations of 0.77, 0.80 and 0.84 were obtained between the principal component-based parameters and the echocardiography scores at the three ischaemic stages, respectively. Expression of these parameters in the time domain showed that the major changes occurred in the depolarisation segment of the endocardial electrogram as well as in the ST-segment. In conclusion, the proposed method provides a suitable alternative co-ordinate system for the classification of ischaemic regions and highlights signal segments that change as a result of pathology.

Three-dimensional electromechanical mapping: imaging in the operating room of the future.

BACKGROUND: Three-dimensional electromechanical mapping has previously been shown to be a clinically important tool for cardiac imaging and intervention. We hypothesized that this technology may be beneficial as an intraoperative modality for assessing cardiac hemodynamics and viability during cardiac surgery. We report here the use of this technology as an imaging modality for intraoperative cardiac surgery. METHODS: The tip of a locatable catheter connected to an endocardial mapping and navigating system is accurately localized while simultaneously recording local electrical and mechanical functions. Thus the three-dimensional geometry of the beating cardiac chamber is reconstructed in real time. The system was tested on 6 goats that underwent acute dynamic cardiomyoplasty and on 5 dogs that underwent left anterior descending (LAD) coronary artery ligation. RESULTS: The electromechanical mapping system provided an accurate three-dimensional reconstruction of the beating left ventricle during cardiomyoplasty. After the wrapping procedure, significant end-diastolic area reduction was noted in the base and mid parts of the heart (948 +/- 194 mm2 vs 1245 +/- 33 mm2, p = 0.021; and 779 +/- 200 mm2 vs 1011 +/- 80 mm2, p = 0.016). The area of the cross-section of the apex did not change during the operation. Acute infarcted tissue was characterized 3 days after LAD ligation by concomitant deterioration in both electrical and mechanical function. CONCLUSIONS: By providing both a clear view of the anatomical changes that occur during cardiac surgery, and an accurate assessment of tissue viability, electroanatomic mapping may serve as an important adjunct tool for imaging and analysis of the heart during cardiac surgery

Detailed endocardial mapping accurately predicts the transmural extent of myocardial infarction.

OBJECTIVES: This study delineates between infarcts varying in transmurality by using endocardial electrophysiologic information obtained during catheter-based mapping. BACKGROUND: The degree of infarct transmurality extent has previously been linked to patient prognosis and may have significant impact on therapeutic strategies. Catheter-based endocardial mapping may accurately delineate between infarcts differing in the transmural extent of necrotic tissue. METHODS: Electromechanical mapping was performed in 13 dogs four weeks after left anterior descending coronary artery ligation, enabling three-dimensional reconstruction of the left ventricular chamber. A concomitant reduction in bipolar electrogram amplitude (BEA) and local shortening indicated the infarcted region. In addition, impedance, unipolar electrogram amplitude (UEA) and slew rate (SR) were quantified. Subsequently, the hearts were excised, stained with 2,3,5-triphenyltetrazolium chloride and sliced transversely. The mean transmurality of the necrotic tissue in each slice was determined, and infarcts were divided into <30%, 31% to 60% and 61% to 100% transmurality subtypes to be correlated with the corresponding electrical data. RESULTS: From the three-dimensional reconstructions, a total of 263 endocardial points were entered for correlation with the degree of transmurality (4.6 +/- 2.4 points from each section). All four indices delineated infarcted tissue. However, BEA (1.9 +/- 0.7 mV, 1.4 +/- 0.7 mV, 0.8 +/- 0.4 mV in the three groups respectively, p < 0.05 between each group) proved superior to SR, which could not differentiate between the second (31% to 60%) and third (61% to 100%) transmurality subgroups, and to UEA and impedance, which could not differentiate between the first (<30%) and second transmurality subgroups. CONCLUSIONS: The degree of infarct transmurality extent can be derived from the electrical properties of the endocardium obtained via detailed catheter-based mapping in this animal model.

Long-term effect of low energy laser irradiation on infarction and reperfusion injury in the rat heart.

Low-energy laser irradiation (LELI) has been found to modulate biological processes. The present study investigated the effect of LELI on infarct size after chronic myocardial infarction (MI) and ischemia-reperfusion injury in rats. The left anterior descending (LAD) coronary artery was ligated in 83 rats to create MI or ischemia-reperfusion injury. The hearts of the laser-irradiated (LI) rats received irradiation after LAD coronary artery occlusion and 3 days post-MI. At 14, 21, and 45 days post-LAD coronary artery permanent occlusion, infarct sizes (percentage of left ventricular volume) in the non-laser-irradiated (NLI) rats were 52 +/- 12 (SD), 47 +/- 11, and 34 +/- 7%, respectively, whereas in the LI rats they were significantly lower, being 20 +/- 8, 15 +/- 6, and 10 +/- 4%, respectively. Left ventricular dilatation (LVD) in the chronic infarcted rats was significantly reduced (50-60%) in LI compared with NLI rats. LVD in the ischemia-reperfusion-injured LI rats was significantly reduced to a value that did not differ from intact normal noninfarcted rats. Laser irradiation caused a significant 2.2-fold elevation in the content of inducible heat shock proteins (specifically HSP70i) and 3.1-fold elevation in newly formed blood vessels in the heart compared with NLI rats. It is concluded that LELI caused a profound reduction in infarct size and LVD in the rat heart after chronic MI and caused complete reduction of LVD in ischemic-reperfused heart. This phenomenon may be partially explained by the cardioprotective effect of the HSP70i and enhanced angiogenesis in the myocardium after laser irradiation.

Novel magnetic technology for intraoperative intracranial frameless navigation: in vivo and in vitro results.

OBJECTIVE: To characterize the accuracy of the Magellan electromagnetic navigation system (Biosense Webster, Tirat HaCarmel, Israel) and to demonstrate the feasibility of its use in image-guided neurosurgical applications. DESCRIPTION OF INSTRUMENTATION: The Magellan system was developed to provide real-time tracking of the distal tips of flexible catheters, steerable endoscopes, and other surgical instruments, using ultra-low electromagnetic fields and a novel miniature position sensor for image-correlated intraoperative navigation and mapping applications. METHODS: An image registration procedure was performed, and static and qualitative accuracies were assessed in a series of phantom, animal, and human neurosurgical studies. EXPERIENCE AND RESULTS: During the human study phase, an accuracy error of up to 5 mm was deemed acceptable. Results demonstrated that this degree of accuracy was maintained throughout all procedures. All anatomic landmarks were reached with precision and were accurately viewed on the display screen. Navigation that relied on the system was also successful. No interference with operating room equipment was noted. The accuracy of the system was maintained during regular surgical procedures, using standard surgical tools. CONCLUSION: The system provides precise lesion localization without limiting the line of vision, the mobility of the surgeon, or the flexibility of instruments. Electromagnetic navigation promises new advances in neuronavigation and frameless stereotactic surgery.

Attenuation of infarct size in rats and dogs after myocardial infarction by low-energy laser irradiation.

BACKGROUND AND OBJECTIVE: The aim of the present study was to investigate the possibility that low-energy laser irradiation attenuates infarct size formation after induction of chronic myocardial infarction (MI) in small and large experimental animals. STUDY DESIGN/MATERIALS AND METHODS: Laser irradiation was applied to the infarcted area of rats and dogs at various power densities (2.5 to 20 mW/cm(2)) after occlusion of the coronary artery. RESULTS: In infarcted laser-irradiated rats that received laser irradiation immediately and 3 days after MI at energy densities of 2.5, 6, and 20 mW/cm(2), there was a 14%, 62% (significant; P < 0.05), and 2.8% reduction of infarct size (14 days after MI) relative to non--laser-irradiated rats, respectively. In dogs, a 49% (significant; P < 0.01) reduction of infarct size was achieved. CONCLUSION: The results of the present study indicate that delivery of low-energy laser irradiation to infarcted myocardium in rats and dogs has a profound effect on the infarct size after MI.

Cardiac contractility modulation with the impulse dynamics signal: studies in dogs with chronic heart failure.

The intravenous use of positive inotropic agents, such as sympathomimetics and phosphodiesterase inhibitors, in heart failure is limited by pro-arrhythmic and positive chronotropic effects. Chronic use of these agents, while eliciting an improvement in the quality of life of patients with advanced heart failure, has been abandoned because of marked increase in mortality when compared to placebo. Nevertheless, patients with advanced heart failure can benefit from long-term positive inotropic support if the therapy can be delivered 'on demand' and in a manner that is both safe and effective. In this review, we will examine the use of a novel, non-stimulatory electrical signal that can acutely modulate left ventricular (LV) contractility in dogs with chronic heart failure in such a way as to elicit a positive inotropic support. Cardiac contractility modulation (CCM) with the Impulse Dynamic(trade mark) signal was examined in dogs with chronic heart failure produced by intracoronary microembolizations. Delivery of the CCM signal from a lead placed in the great coronary vein for periods up to 10 minutes resulted in significant improvements in cardiac output, LV peak+dP/dt, LV fractional area of shortening and LV ejection fraction measured angiographically. Discontinuation of the signal resulted in a return of all functional parameters to baseline values. In cardiomyocytes isolated from dogs with chronic heart failure, application of the CCM signal resulted in improved shortening, rate of change of shortening and rate of change of relengthening suggesting that CCM application is associated with intrinsic improvement of cardiomyocyte function. The improvement in isolated cardiomyocyte function after application of the CCM signal was accompanied by an increase in the peak and integral of the Ca(2+) transient suggesting modulation of calcium cycling by CCM application. In a limited number of normal dogs, intermittent chronic delivery of the CCM signal for up to 7 days showed chronic maintenance of LV functional improvement. In conclusion, pre-clinical results to date with the Impulse Dynamics CCM signal indicate that this non-pharmacologic therapeutic modality can provide short-term positive inotropic support to the failing heart and as such, may be a useful adjunct in the treatment of advanced heart failure. Additional, long-term studies in dogs with heart failure are needed to establish the safety and efficacy of this therapeutic modality for the chronic treatment of this disease syndrome.

Electrical modulation of cardiac contractility: clinical aspects in congestive heart failure.

Heart failure is a highly prevalent disease in western society. Drug therapies aimed at increasing myocardial contractility have been associated with decreased survival. Several short and mid term clinical studies have suggested adjuvant or alternative therapies to congestive heart failure using modified pacing techniques that were aimed to increase contractility (e.g. Paired pacing) or restore synchrony of contraction (biventricular pacing). While delivery of paired pacing was abandoned during the early 70's, biventricular pacing has recently emerged as an adjuvant treatment to limited group of congestive heart failure patients with aberrant left ventricular conduction. In this brief review, we describe our initial safety and efficacy experience in patients with heart failure using a novel non-stimulatory electrical approach to the delivery of positive inotropic therapy to the failing myocardium. The study suggests that unlike modified pacing techniques, delivery of the signal to the left ventricle during the refractory period resulted in a rapid increase in myocardial contractility and improved hemodynamic performance. The near instantaneous contractility improvement achieved by this type of stimulus was shown to be safe and effective independently of the primary cause of heart failure or the function of the conduction system. Unlike pharmacologic treatments, which have a relatively constant effect, use of electrical stimuli may prove useful as a new therapeutic modality in the treatment of heart failure with which contractility can be improved when and as needed.

Assessment of NOGA catheter stability during the entire cardiac cycle by means of a special needle-tipped catheter.

The NOGA system maps regional myocardial function and delivers local catheter-based therapeutics, requiring stability and precise localization of the catheter tip throughout the cardiac cycle. A special catheter having a retractable needle at its tip was used to compare tip stability with and without needle insertion into the myocardium, assuming this prevents catheter slippage. For multiple sites in seven pig left ventricles, we recorded sets of three consecutive point locations: pre-, post-, and during needle insertion. In-point location stability (LocStab), defined as the mean displacement between catheter tip trajectories of two consecutive cardiac cycles at a specific point, did not differ among the three groups of points (mean, 1.33 +/- 0.61 mm; P = 0.37 by ANOVA), indicating that trajectories are equally stable and repeatable with or without needle insertion. Between-point LocStab(p1,p2), i.e., displacement between the trajectories of two different points (p1 and p2) at the same location, was not increased when p1 = a needle insertion point and p2 = a noninsertion point, compared to both p1,p2 = noninsertion points, suggesting that slippage of noninsertion points is negligible. In conclusion, catheter tip trajectories at any location are highly stable throughout the cardiac cycle.

Three-dimensional endocardial impedance mapping: a new approach for myocardial infarction assessment.

Precise identification of infarcted myocardial tissue is of importance in diagnostic and interventional cardiology. A three-dimensional, catheter-based endocardial electromechanical mapping technique was used to assess the ability of local endocardial impedance in delineating the exact location, size, and border of canine myocardial infarction. Electromechanical mapping of the left ventricle was performed in a control group (n = 10) and 4 wk after left anterior descending coronary artery ligation (n = 10). Impedance, bipolar electrogram amplitude, and endocardial local shortening (LS) were quantified. The infarcted area was compared with the corresponding regions in controls, revealing a significant reduction in impedance values [infarcted vs. controls: 168.8 +/- 11. 7 and 240.7 +/- 22.3 Omega, respectively (means +/- SE), P < 0.05] bipolar electrogram amplitude (1.8 +/- 0.2 mV, 4.4 +/- 0.7 mV, P < 0. 05), and LS (-2.36 +/- 1.6%, 11.9 +/- 0.9%, P < 0.05). The accuracy of the impedance maps in delineating the location and extent of the infarcted region was demonstrated by the high correlation with the infarct area (Pearson's correlation coefficient = 0.942) and the accurate identification of the infarct borders in pathology. By accurately defining myocardial infarction and its borders, endocardial impedance mapping may become a clinically useful tool in differentiating healthy from necrotic myocardial tissue.