Real-time three-dimensional transesophageal echocardiography for guiding interventional electrophysiology: feasibility study

At present, there are limited methods of acquiring three-dimensional visualization of cardiac structure and function in real-time during interventional electrophysiology procedures. Images acquired for integration of computerized tomography and magnetic resonance imaging with electroanatomic mapping systems are static and are obtained earlier in time. The purpose of this study was to test the feasibility of real-time three-dimensional transesophageal echocardiography for the guidance of interventional electrophysiological studies. A matrix array transducer with 504 channels operating at 5 MHz in a 1 cm diameter steerable esophageal probe was used in conjunction with a scanner capable of real-time 3D scanning of pyramidal volumes from 65 degrees to 120 degrees at rates up to 30 volumes per second. This device has a spatial resolution of approximately 3 mm at 5 cm depth. The authors acquired real-time three-dimensional images of anatomic landmarks of value for electrophysiological procedures in five closed chest canines. Real-time, three-dimensional ultrasound imaging was also used for visualization and guidance of interventional catheter devices within the canine heart. Real-time three-dimensional images of the atria, pulmonary veins, and coronary sinus were acquired. Real-time 3-D color flow Doppler was employed to confirm patency. Multiple image planes of image volumes and rendered views were used to track catheter position and orientation. Images of left veno-atrial junctions have been confirmed by dissection. This study has demonstrated the feasiblity of using real-time three-dimensional transesophageal echocardiography for guiding interventional electrophysiology. The technology has the potential to fill a niche as an adjunct modality for cost-effective real-time interventional guidance and assessment, providing catheter and pacing lead visualization simultaneously with functional volumetric cardiac imaging.

Physostigmine for gamma-hydroxybutyrate coma: inefficacy, adverse events, and review

Physostigmine has been proposed as an antidote for gamma hydroxybutyrate (GHB) intoxication, based on associated awakenings in 1) patients anesthetized with GHB and 2) five of six patients administered physostigmine for GHB intoxication. However, there are neither well-supported mechanisms for physostigmine reversal of GHB effects, supportive animal studies, nor randomized, placebo-controlled trials demonstrating safety, efficacy, or improved outcomes. We sought to determine the outcomes of patients with GHB-induced coma after a physostigmine treatment protocol was instituted in an urban Emergency Department and ambulance service. Our search of medical records located five cases of GHB toxicity, all with co-intoxicants, who received physostigmine. None demonstrated response and, further, there were associated adverse events, including atrial fibrillation (2), pulmonary infiltrates (1) and significant bradycardia (1), and hypotension (1). We also reviewed 18 published GHB toxicity case series for incidence of adverse effects, stimulant co-intoxicants (which may heighten risk of physostigmine), complications, and outcomes of supportive care for GHB toxicity. We conclude that physostigmine is not indicated for reversal of GHB-induced alteration of consciousness; it is not efficacious, it may be unsafe, particularly in the setting of recreational polydrug use; and supportive care results in universally good outcomes.

Integrated endoscope for real-time 3D ultrasound imaging and hyperthermia: feasibility study

The goal of this research is to determine the feasibility of using a single endoscopic probe for the combined purpose of real-time 3D (RT3D) ultrasound imaging of a target organ and the delivery of ultrasound therapy to facilitate the absorption of compounds for cancer treatment. Recent research in ultrasound therapy has shown that ultrasound-mediated drug delivery improves absorption of treatments for prostate, cervical and esophageal cancer. The ability to combine ultrasound hyperthermia and 3D imaging could improve visualization and targeting of cancerous tissues. In this study, numerical modeling and experimental measurements were developed to determine the feasibility of combined therapy and imaging with a 1 cm diameter endoscopic RT3D probe with 504 transmitters and 252 receive channels. This device operates at 5 MHz and has a 6.3 mm x 6.3 mm aperture to produce real time 3D pyramidal scans of 60-120 degrees incorporating 64 x 64 = 4096 image lines at 30 volumes/sec interleaved with a 3D steerable therapy beam. A finite-element mesh was constructed with over 128,000 elements in LS-DYNA to simulate the induced temperature rise from our transducer with a 3 cm deep focus in tissue. Quarter-symmetry of the transducer was used to reduce mesh size and computation time. Based on intensity values calculated in Field II using the transducer's array geometry, a minimum I(SPTA) of 3.6 W/cm2 is required from our endoscope probe in order to induce a temperature rise of 4 degrees C within five minutes. Experimental measurements of the array's power output capabilities were conducted using a PVDF hydrophone placed 3 cm away from the face of the transducer in a watertank. Using a PDA14 Signatec data acquisition board to capture full volumes of transmitted ultrasound data, it was determined that the probe can presently maintain intensity values up to 2.4 W/cm2 over indefinite times for therapeutic applications combined with intermittent 3D scanning to maintain targeting. These values were acquired using 8 cycle bursts at a prf of 6 kHz. Ex vivo heating experiments of excised pork tissue yielded a maximum temperature rises of 2.3 degrees C over 5 minutes of ultrasound exposure with an average rise of 1.8 +/- 0.2 degrees C over 5 trials. Modifications to the power supply and transducer array may enable us to reach the higher intensities required to facilitate drug delivery therapy.

Sumatriptan for the treatment of undifferentiated primary headaches in the ED

OBJECTIVE

In this study, we determine the effectiveness and adverse effects of sumatriptan when used in the emergency department (ED) as a first-line treatment for benign undifferentiated headaches, and determine if the International Headache Society (IHS) classification of migraine, probable migraine, or tension-type headache has any effect on the effectiveness of the treatment. We hypothesize that there is no difference in the effectiveness of pain relief or frequency and severity of adverse effects between patients with migraine, probable migraine, or tension-type headaches when treated with sumatriptan.

METHODS

This was a prospective observational study of adult ED patients undergoing treatment for primary headaches (ie, patients in whom head trauma, vascular disorders, infection, or disorders of facial or cranial structures have been clinically excluded). Other exclusions were renal impairment, hepatic impairment, and risk factors for coronary artery disease. Consenting patients then were asked to complete a 100-mm visual analog scale (VAS) representing their perceived pain, after which they were interviewed by a research assistant who completed a headache diagnosis worksheet, which differentiates the headache by IHS criteria. The patient repeated the VAS score at 30 and 60 minutes. Data were analyzed using descriptive statistics and chi squared tests.

RESULTS

One hundred forty-seven patients were enrolled: 84 (57.1%) patients with migraine headache, 45 (30.7%) with a probable migraine headache, and 18 (12.2%) with a tension headache. A 50% reduction in VAS scores 60 minutes postdose was seen in 87 (59%) of 147 patients; 50 (60%) of 84 of migraine patients, 25 (56%) of 45 of probable migraine patients, and 12 (67%) of 18 tension patients (P = .72). There were no serious adverse events reported. Forty-seven patients (32%) received rescue medications after the 60-minute VAS score: 29 (34.5%) patients in the migraine group, 15 (33.3%) patients in the probable migraine group, and 3 (15.8%) patients in the tension-type headache group (P = .26).

CONCLUSIONS

Most of the patients presenting with primary headaches had migraine or probable migraine headaches. There was no difference in sumatriptan's effectiveness based on the classification of the headache using IHS criteria.

Some realism about end of life: the current prohibition and the euthanasia underground

This well-known quotation from one of America's foremost judges provides an important admonishment about the role of history within the law. Holmes’ admonishment is that, even in common law systems, we should not allow ourselves to become too dependent on legal rules laid down in the past. Legal rules laid down long ago are as likely as newly constructed ones to have flaws in their reasoning or be difficult to implement in real-life situations. Furthermore, even in cases where the rule may have originally served some purpose, it may nevertheless be out of date and therefore have little continuing benefit to a particular legal system.

3-D ultrasound guidance of surgical robotics: a feasibility study

Laparoscopic ultrasound has seen increased use as a surgical aide in general, gynecological, and urological procedures. The application of real-time, three-dimensional (RT3D) ultrasound to these laparoscopic procedures may increase information available to the surgeon and serve as an additional intraoperative guidance tool. The integration of RT3D with recent advances in robotic surgery also can increase automation and ease of use. In this study, a 1-cm diameter probe for RT3D has been used laparoscopically for in vivo imaging of a canine. The probe, which operates at 5 MHz, was used to image the spleen, liver, and gall bladder as well as to guide surgical instruments. Furthermore, the three-dimensional (3-D) measurement system of the volumetric scanner used with this probe was tested as a guidance mechanism for a robotic linear motion system in order to simulate the feasibility of RT3D/robotic surgery integration. Using images acquired with the 3-D laparoscopic ultrasound device, coordinates were acquired by the scanner and used to direct a robotically controlled needle toward desired in vitro targets as well as targets in a post-mortem canine. The rms error for these measurements was 1.34 mm using optical alignment and 0.76 mm using ultrasound alignment.

Real-time stereo 3D ultrasound

Real-time 3D ultrasound was developed at Duke University in 1991 and has since been used with a variety of transducers and shown effectiveness in clinical applications and in vivo animal imaging studies. Methods for displaying the 3D pyramid of data acquired by the system include selecting 2D image slices or integrating data into a volume rendered view. A third method, real-time stereo 3D imaging, is discussed here. The clinical commercial 3D system has been modified in our laboratory to display a real-time stereo image pair on the scanner display to be viewed through a stereoscope. This merges the pair into a single image, with a sensation of depth. Stereoscopic displays have previously been demonstrated to provide benefits, including improved depth judgments and increased perception of image quality in other applications. Previously-saved volumes of ultrasound data are shown in stereo 3D using the new system.

Phase-aberration correction with a 3-D ultrasound scanner: feasibility study

We tested the feasibility of using adaptive imaging, namely phase-aberration correction, with two-dimensional (2-D) arrays and real-time, 3-D ultrasound. Because of the high spatial frequency content of aberrators, 2-D arrays, which generally have smaller pitch and thus higher spatial sampling frequency, and 3-D imaging show potential to improve the performance of adaptive imaging. Phase-correction algorithms improve image quality by compensating for tissue-induced errors in beamforming. Using the illustrative example of transcranial ultrasound, we have evaluated our ability to perform adaptive imaging with a real-time, 3-D scanner. We have used a polymer casting of a human temporal bone, root-mean-square (RMS) phase variation of 45.0 ns, full-width-half-maximum (FWHM) correlation length of 3.35 mm, and an electronic aberrator, 100 ns RMS, 3.76 mm correlation, with tissue phantoms as illustrative examples of near-field, phase-screen aberrators. Using the multilag, least-squares, cross-correlation method, we have shown the ability of 3-D adaptive imaging to increase anechoic cyst identification, image brightness, contrast-to-speckle ratio (CSR), and, in 3-D color Doppler experiments, the ability to visualize flow. For a physical aberrator skull casting we saw CSR increase by 13% from 1.01 to 1.14, while the number of detectable cysts increased from 4.3 to 7.7.

Upwardly concave ST segment morphology is common in acute left anterior descending coronary occlusion

ST elevation (STE) in anterior precordial leads, in association with upwardly convex morphology (M) or straightM, is associated with anterior acute myocardial infarction (aAMI). Upwardly concaveM is characteristic of pseudoinfarction patterns such as early repolarization. A retrospective review was done of diagnostic electrocardiograms (EKG) of consecutive patients presenting to our Emergency Department (ED) who underwent emergent primary percutaneous intervention (PCI) and had proven left anterior descending (LAD) occlusion. If all leads from V2-V6 were upwardly concave, the EKG was classified as concaveM. If one lead was convex, the EKG had convexM. If no leads were convex and at least one was straight, it had straightM. Non-concaveM was defined as either convexM or straightM. Borderline STE was defined if the EKG did not have 2 consecutive leads with >or= 2 mm of STE. "Subtle," as opposed to "diagnostic," morphology was defined as concaveM without terminal QRS distortion. Data were analyzed with descriptive statistics. There were 37 patients identified who met the inclusion criteria and whose records were available for review. ConcaveM was found in 16 of 37 (43%), 4 with terminal QRS distortion. Measurements resulted in a classification of borderline STE in 15 of 37 (41%) (9 of whom had subtle morphology) for Rater 1 and 12 of 37 (32%) (7 of whom had subtle morphology) for Rater 2, while 19% to 24% had both "subtle" morphology and borderline ST elevation. ConcaveM, as compared with convexM or terminal QRS distortion, was associated with a shorter duration of symptoms (p < 0.05). It is concluded that concave morphology cannot be used to exclude STEMI with LAD occlusion. Many patients with LAD occlusion have borderline ST elevation with subtle morphology. Concave morphology is associated with a shorter duration of symptoms.

ST segment elevation differs depending on the method of measurement

OBJECTIVES

The literature seldom specifies the location or method of measurement of ST segment elevation (STE) for determining eligibility in reperfusion trials. The objective of this study was to assess if different methods of measurement of STE in precordial leads of patients with anterior acute myocardial infarction due to left anterior descending occlusion result in significantly different scores.

METHODS

This was a retrospective review of diagnostic electrocardiograms (ECGs) of consecutive patients presenting to our emergency department with acute myocardial infarction who had emergent primary percutaneous coronary intervention, left anterior descending occlusion, and no bundle branch block. STE was measured at the J point and at 60 milliseconds after the J point, relative to the PR segment, in leads V1-V6. STE by the two methods was compared for each lead, as were ST scores (sum of STE in leads V1-V6) and the sum of the STE in V2-V4. Eligibility for reperfusion therapy using 1-mm and 2-mm STE criteria in two consecutive anterior leads, as well as ST scores and the sum of the STE in V2-V4, were evaluated.

RESULTS

Thirty-seven ECGs were analyzed. Mean ST measurements in every lead were significantly lower when measured at the J point versus 60 milliseconds after the J point, as were ST scores (9.7 +/- 2.14 mm vs. 14.9 +/- 2.69 mm; p < 0.00001). Fewer ECGs met enrollment criteria when based on STE at the J point versus at 60 milliseconds after the J point. Fewer ECGs met an ST score of 6 mm when measured at the J point (70% vs. 88%).

CONCLUSIONS

In anterior STE myocardial infarction, STE measurements produce different results depending on the method of measurement. Future clinical trials should specify the method of measurement.

Acute coronary syndromes

Despite technologic advances in many diagnostic fields, the 12-lead ECG remains the basis for early identification and management of an acute coronary syndrome. This article reviews the use of the ECG in acute coronary syndromes.

Real-time, 3-D ultrasound with multiple transducer arrays

Modifications were made to a commercial real-time, three-dimensional (3-D) ultrasound system for near simultaneous 3-D scanning with two matrix array transducers. As a first illustration, a transducer cable assembly was modified to incorporate two independent, 3-D intra-cardiac echo catheters, a 7 Fr (2.3 mm O.D.) side scanning catheter and a 14 Fr (4.7 mm O.D) forward viewing catheter with accessory port, each catheter using 85 channels operating at 5 MHz. For applications in treatment of atrial fibrillation, the goal is to place the sideviewing catheter within the coronary sinus to view the whole left atrium, including a pulmonary vein. Meanwhile, the forward-viewing catheter inserted within the left atrium is directed toward the ostium of a pulmonary vein for therapy using the integrated accessory port. Using preloaded, phasing data, the scanner switches between catheters automatically, at the push of a button, with a delay of about 1 second, so that the clinician can view the therapy catheter with the coronary sinus catheter and vice versa. Preliminary imaging studies in a tissue phantom and in vivo show that our system successfully guided the forward-viewing catheter toward a target while being imaged with the sideviewing catheter. The forward-viewing catheter then was activated to monitor the target while we mimicked therapy delivery. In the future, the system will switch between 3-D probes on a line-by-line basis and display both volumes simultaneously.

The killing of severely disabled newborns: the spectre behind the legalisation of physician-assisted suicide and euthanasia

Arguments made by those in favour of the legalisation of physician-assisted suicide (PAS) and euthanasia often rely upon the idea of the quality of life. This idea states that an individual's life is not valuable as an intrinsic good, but is only good based upon the things which it allows us to do. It thus allows the argument that it is morally permissible to kill individuals whose lives have fallen below an acceptable 'quality of life.' However, this concept may require that one accept the killing of individuals who have not expressly request to be killed such as severely disabled newborns. This paper will examine the issue of whether those who utilise a quality of life approach to justify the legalisation of PAS and euthanasia must logically accept the policy of killing severely disabled newborn children. First, there will be an examination of the concept of quality of life and its importance in the arguments for the legalisation of PAS or euthanasia. This paper will then consider how notions of personhood interact with the concept of quality of life in order to create the problem faced by those who favour the legalisation of PAS or euthanasia. Finally, this paper will consider how the notion of autonomy may be used as a way to avoid this difficulty created by the quality of life approach.

Finite-element analysis of temperature rise and lesion formation from catheter ultrasound ablation transducers

A model using finite-element analysis (FEA) has been developed to calculate the temperature rise in tissue from intracardiac ultrasound ablation catheters and to predict if this temperature rise is adequate for producing a lesion in the tissue. In the model, acoustic fields are simulated with Field II, and heat transfer is modeled with an FEA program. To validate the model, we compare its results to experimental results from an integrated, real-time three-dimensional (3-D) ultrasound imaging and ultrasound ablation catheter. The ultrasound ablation transducer is a ring transmitting at 10 MHz capable of producing an acoustic intensity of 16 W/cm2. It was used to ablate four lesions in tissue, and temperature rise as a function of time was monitored by embedded thermocouples. The average absolute difference between final temperatures predicted by FEA and those measured is 1.95 +/- 0.72 degrees C. Additionally, model and experimental lesion size are in good agreement. The model then is used to design a new ultrasound catheter with a 7.5 MHz linear phased array for ablation. Eight designs are modeled, and acoustic intensity, temperature rise, and ablation ability are compared.

Real-time 3D laparoscopic ultrasonography

We have previously described 2D array ultrasound transducers operating up to 10 MHz for applications including real time 3D transthoracic imaging, real time volumetric intracardiac echocardiography (ICE), real time 3D intravascular ultrasound (IVUS) imaging, and real time 3D transesophageal echocardiography (TEE). We have recently built a pair of 2D array transducers for real time 3D laparoscopic ultrasonography (3D LUS). These transducers are intended to be placed down a trocar during minimally invasive surgery. The first is a forward viewing 5 MHz, 11 x 19 array with 198 operating elements. It was built on an 8 layer multilayer flex circuit. The interelement spacing is 0.20 mm yielding an aperture that is 2.2 mm x 3.8 mm. The O.D. of the completed transducer is 10.2 mm and includes a 2 mm tool port. The average measured center frequency is 4.5 MHz, and the -6 dB bandwidth ranges from 15% to 30%. The 50 omega insertion loss, including Gore MicroFlat cabling, is -81.2 dB. The second transducer is a 7 MHz, 36 x 36 array with 504 operating elements. It was built upon a 10 layer multilayer flex circuit. This transducer is in the forward viewing configuration and the interelement spacing is 0.18 mm. The total aperture size is 6.48 mm x 6.48 mm. The O.D. of the completed transducer is 11.4 mm. The average measured center frequency is 7.2 MHz, and the -6 dB bandwidth ranges from 18% to 33%. The 50 omega insertion loss is -79.5 dB, including Gore MicroFlat cable. Real-time in vivo 3D images of canine hearts have been made including an apical 4-chamber view from a substernal access with the first transducer to monitor cardiac function. In addition, we produced real time 3D rendered images of the right pulmonary veins from a right parastemal access with the second transducer, which would be valuable in the guidance of cardiac ablation catheters for treatment of atrial fibrillation.

T/QRS ratio best distinguishes ventricular aneurysm from anterior myocardial infarction

OBJECTIVES

Reperfusion therapy for acute myocardial infarction (AMI) is indicated in the presence of ST elevation (STE) and ischemic symptoms. Previous MI may present with persistent STE or "left ventricular aneurysm" (LVA) morphology that mimics AMI. Hypothesis A high ratio of T amplitude to QRS amplitude best distinguishes AMI from LVA.

METHODS

This was a retrospective cohort analysis. Patients with anatomical LVA by echocardiography were identified and those who presented to the ED with ischemic symptoms and STE of at least 1 mm in 2 consecutive leads and ruled out for acute left anterior descending coronary artery (LAD) occlusion were selected. Electrocardiograms (ECGs) were compared with a control group of 37 consecutive anterior AMI (aAMI) with proven acute LAD occlusion. Bundle-branch block was excluded. Various ECG measurements and ratios were compared.

RESULTS

Twenty patients with LVA met the inclusion criteria. The best discriminator was T amplitude sum to QRS amplitude sum ratio V1-V4, misclassifying only 4 (6.8%) of 59 cases at a cutoff of >0.22 for AMI. For aAMI and LVA, respectively, mean (+/-95% CI) ratio of the sum of T amplitudes in V 1 to V 4 to the sum of QRS amplitude in V1-V4 was 0.54+/-0.085 and 0.16+/-0.021 (P<.00012). Thirty-five of 37 aAMI had a ratio>0.22; the false negatives (ratio<0.22) had 11.5 and 6 hours of symptoms before the ECG. Twenty of 22 LVA had a ratio<or=0.22. Mean highest T/QRS ratio in V1-V4 was 1.1+/-0.29 for an AMI and 0.26+/-0.056 for LVA (P<10(-7)).

CONCLUSION

T amplitude/QRS amplitude ratio best distinguishes aAMI from LVA in ECGs that meet STE criteria for reperfusion therapy. A high ratio is associated with an AMI.

Agitation is common in γ-hydroxybutyrate toxicity

Gamma-Hydroxybutyrate (GHB)-related compounds are most commonly described as depressants, with emphasis on somnolence, obtundation, stupor, and coma (SOSC). We sought to demonstrate the full spectrum of clinical presentations of GHB intoxication, including agitation and other nonsedative effects. Our observational study identified 66 patients with GHB toxicity, 40 of whom manifested agitation; 25 had agitation before or after SOSC, 10 had agitation alternating abruptly with SOSC, and 5 had agitation only. Fourteen presentations also included "bizarre" or self-injurious behaviors. Of 40 presentations with agitation, 19 had stimulant co-intoxicants confirmed by screen (14) or history (5). The remaining 21 patients with agitation were negative for stimulants by screen (12) or history (9). Gas chromatography/mass spectrometry detected GHB in 25 cases; 12 manifested agitation, 4 of which also screened negative for stimulants. Clinicians should broaden their definitions of GHB toxicity to include nonsedative effects such as agitation, combativeness, and bizarre or self-injurious behavior.