Remote intensive management to improve antiplatelet adherence in acute myocardial infarction: a secondary analysis of the randomized controlled IMMACULATE trial

This study aim to investigate if remote intensive coaching for the first 6 months post-AMI will improve adherence to the twice-a-day antiplatelet medication, ticagrelor. Between July 8, 2015, to March 29, 2019, AMI patients were randomly assigned to remote intensive management (RIM) or standard care (SC). RIM participants underwent 6 months of weekly then two-weekly consultations to review medication side effects and medication adherence coaching by a centralized nurse practitioner team, whereas SC participants received usual cardiologist face-to-face consultations. Adherence to ticagrelor were determined using pill counting and serial platelet reactivity measurements for 12 months. A total of 149 (49.5%) of participants were randomized to RIM and 152 (50.5%) to SC. Adherence to ticagrelor was similar between RIM and SC group at 1 month (94.4 ± 0.7% vs. 93.6±14.7%, p = 0.537), 6 months (91.0±14.6% vs. 90.6±14.8%, p = 0.832) and 12 months (87.4±17.0% vs. 89.8±12.5%, p = 0.688). There was also no significant difference in platelet reactivity between the RIM and SC groups at 1 month (251AU*min [212-328] vs. 267AU*min [208-351], p = 0.399), 6 months (239AU*min [165-308] vs. 235AU*min [171-346], p = 0.610) and 12 months (249AU*min [177-432] vs. 259AU*min [182-360], p = 0.678). Sensitivity analysis did not demonstrate any association of ticagrelor adherence with bleeding events and major adverse cardiovascular events. RIM, comprising 6 months of intensive coaching by nurse practitioners, did not improve adherence to the twice-a-day medication ticagrelor compared with SC among patients with AMI. A gradual decline in ticagrelor adherence over 12 months was observed despite 6 months of intensive coaching.

Impact of Diabetes on Myocardial Fibrosis in Patients With Hypertension: The REMODEL Study

BACKGROUND

Compared with patients with hypertension only, those with hypertension and diabetes (HTN/DM) have worse prognosis. We aimed to characterize morphological differences between hypertension and HTN/DM using cardiovascular magnetic resonance; and compare differentially expressed proteins associated with myocardial fibrosis using high throughput multiplex assays.

METHODS

Asymptomatic patients underwent cardiovascular magnetic resonance: 438 patients with hypertension (60±8 years; 59% males) and 167 age- and sex-matched patients with HTN/DM (60±10 years; 64% males). Replacement myocardial fibrosis was defined as nonischemic late gadolinium enhancement on cardiovascular magnetic resonance. Extracellular volume fraction was used as a marker of diffuse myocardial fibrosis. A total of 184 serum proteins (Olink Target Cardiovascular Disease II and III panels) were measured to identify unique signatures associated with myocardial fibrosis in all patients.

RESULTS

Despite similar left ventricular mass (P=0.344) and systolic blood pressure (P=0.086), patients with HTN/DM had increased concentricity and worse multidirectional strain (P<0.001 for comparison of all strain measures) compared to hypertension only. Replacement myocardial fibrosis was present in 28% of patients with HTN/DM compared to 16% of those with hypertension (P<0.001). NT-proBNP (N-terminal pro-B-type natriuretic peptide) was the only protein differentially upregulated in hypertension patients with replacement myocardial fibrosis and independently associated with extracellular volume. In patients with HTN/DM, GDF-15 (growth differentiation factor 15) was independently associated with replacement myocardial fibrosis and extracellular volume. Ingenuity Pathway Analysis demonstrated a strong association between increased inflammatory response/immune cell trafficking and myocardial fibrosis in patients with HTN/DM.

CONCLUSIONS

Adverse cardiac remodeling was observed in patients with HTN/DM. The novel proteomic signatures and associated biological activities of increased immune and inflammatory response may partly explain these observations.

Evaluation of 2 Novel Ratio-Based Metrics for Lumbar Spinal Stenosis

BACKGROUND AND PURPOSE

Quantitative metrics of the dural sac such as the cross-sectional area are commonly used to evaluate central canal stenosis. The aim of this study was to analyze 2 new metrics to measure spinal stenosis on the basis of the ratio between the dural sac and disc cross-sectional areas (DDRCA) and the dural sac and disc anterior-posterior diameters (DDRDIA) and compare them with established quantitative metrics of the dural sac.

MATERIALS AND METHODS

T2-weighted axial MR images (n = 260 patients) were retrospectively evaluated, graded for central canal stenosis as normal (no stenosis), mild, moderate, or severe from L1/L2 through L5/S1 with 1 grade per spinal level and annotated to measure the DDRCA and DDRDIA. Thresholds were obtained using a decision tree classifier on a subset of patients (n = 130) and evaluated on the remaining patients (n = 130) for accuracy and consistency across demographics, anatomic variation, and clinical outcomes.

RESULTS

DDRCA and DDRDIA had areas under the receiver operating characteristic curve of 98.6 (97.4-99.3) and 98.0 (96.7-98.9) compared with dural sac cross-sectional area at 96.5 (95.0-97.7) for binary classification. DDRDIA and DDRCA had κ scores of 0.75 (0.71-0.79) and 0.80 (0.75-0.83) compared with dural sac cross-sectional area at 0.62 (0.57-0.66) for multigrade classification. No significant differences (P > .1) in the area under the receiver operating characteristic curve were observed for the DDRDIA across variations in the body mass index. The DDRDIA also had the highest area under the receiver operating characteristic curve among symptomatic patients (visual analog scale ≥ 7) or patients who underwent surgery.

CONCLUSIONS

Ratio-based metrics (DDRDIA and DDRCA) are accurate and robust to anatomic and demographic variability compared with quantitative metrics of the dural sac and better correlated with symptomatology and surgical outcomes.

Markers of Focal and Diffuse Nonischemic Myocardial Fibrosis Are Associated With Adverse Cardiac Remodeling and Prognosis in Patients With Hypertension: The REMODEL Study

BACKGROUND

The prognostic significance of focal and diffuse myocardial fibrosis in patients with cardiovascular risk factors is unclear.

METHODS

REMODEL (Response of the Myocardium to Hypertrophic Conditions in the Adult Population) is an observational cohort of asymptomatic patients with essential hypertension. All participants underwent cardiovascular magnetic resonance to assess for myocardial fibrosis: nonischemic late gadolinium enhancement (LGE), native myocardial T1, postcontrast myocardial T1, extracellular volume fraction including/excluding LGE regions, interstitial volume (extracellular volume×myocardial volume), and interstitial/myocyte ratio. Primary outcome was a composite of first occurrence acute coronary syndrome, heart failure hospitalization, strokes, and cardiovascular mortality. Patients were recruited from February 2016 and followed until June 2021.

RESULTS

Of the 786 patients with hypertension (58±11 years; 39% women; systolic blood pressure, 130±14 mm Hg), 145 (18%) had nonischemic LGE. Patients with nonischemic LGE were more likely to be men, have diabetes, be current smokers, and have higher blood pressure (P<0.05 for all). Compared with those without LGE, patients with nonischemic LGE had greater left ventricular mass (66±22 versus 49±9 g/m²; P<0.001), worse multidirectional strain (P<0.001 for all measures), and elevated circulating markers of myocardial wall stress and myocardial injury, adjusted for potential confounders. Twenty-four patients had primary outcome over 39 (30-50) months of follow-up. Of all the cardiovascular magnetic resonance markers of myocardial fibrosis assessed, only nonischemic LGE (hazard ratio, 6.69 [95% CI, 2.54-17.60]; P<0.001) and indexed interstitial volume (hazard ratio, 1.11 [95% CI, 1.04-1.19]; P=0.002) demonstrated independent association with primary outcome.

CONCLUSIONS

In patients with hypertension, myocardial fibrosis on cardiovascular magnetic resonance is associated with adverse cardiac remodeling and outcomes.

Remote Postdischarge Treatment of Patients With Acute Myocardial Infarction by Allied Health Care Practitioners vs Standard Care: The IMMACULATE Randomized Clinical Trial

Question

Is remote postdischarge treatment of low-risk patients with acute myocardial infarction by a centralized nurse clinician team under physician supervision feasible and safe?

Findings

In this multicenter randomized clinical trial of 301 participants, there were no significant differences in safety events, medication adjustment, or left ventricular reverse remodeling outcomes in low-risk patients with acute myocardial infarction treated for 6 months after discharge by a centralized nurse practitioner–led telehealth program compared with standard in-person care by a cardiologist.

Meaning

Remote telehealth-enabled allied health care practitioner–led postdischarge management of low-risk patients with acute myocardial infarction is feasible and should be studied in higher-risk acute myocardial infarction cohorts.

Importance

There are few data on remote postdischarge treatment of patients with acute myocardial infarction.

Objective

To compare the safety and efficacy of allied health care practitioner–led remote intensive management (RIM) with cardiologist-led standard care (SC).

Design, Setting, and Participants

This intention-to-treat feasibility trial randomized patients with acute myocardial infarction undergoing early revascularization and with N-terminal–pro-B-type natriuretic peptide concentration more than 300 pg/mL to RIM or SC across 3 hospitals in Singapore from July 8, 2015, to March 29, 2019. RIM participants underwent 6 months of remote consultations that included β-blocker and angiotensin-converting enzyme inhibitor/angiotensin receptor blocker (ACE-I/ARB) dose adjustment by a centralized nurse practitioner team while SC participants were treated face-to-face by their cardiologists.

Main Outcomes and Measures

The primary safety end point was a composite of hypotension, bradycardia, hyperkalemia, or acute kidney injury requiring hospitalization. To assess the efficacy of RIM in dose adjustment of β-blockers and ACE-I/ARBs compared with SC, dose intensity scores were derived by converting comparable doses of different β-blockers and ACE-I/ARBs to a scale from 0 to 5. The primary efficacy end point was the 6-month indexed left ventricular end-systolic volume (LVESV) adjusted for baseline LVESV.

Results

Of 301 participants, 149 (49.5%) were randomized to RIM and 152 (50.5%) to SC. RIM and SC participants had similar mean (SD) age (55.3 [8.5] vs 54.7 [9.1] years), median (interquartile range) N-terminal–pro-B-type natriuretic peptide concentration (807 [524-1360] vs 819 [485-1320] pg/mL), mean (SD) baseline left ventricular ejection fraction (57.4% [11.1%] vs 58.1% [10.3%]), and mean (SD) indexed LVESV (32.4 [14.1] vs 30.6 [11.7] mL/m²); 15 patients [5.9%] had a left ventricular ejection fraction <40%. The primary safety end point occurred in 0 RIM vs 2 SC participants (1.4%) (P = .50). The mean β-blocker and ACE-I/ARB dose intensity score at 6 months was 3.03 vs 2.91 (adjusted mean difference, 0.12 [95% CI, −0.02 to 0.26; P = .10]) and 2.96 vs 2.77 (adjusted mean difference, 0.19 [95% CI, −0.02 to 0.40; P = .07]), respectively. The 6-month indexed LVESV was 28.9 vs 29.7 mL/m² (adjusted mean difference, −0.80 mL/m² [95% CI, −3.20 to 1.60; P = .51]).

Conclusions and Relevance

Among low-risk patients with revascularization after myocardial infarction, RIM by allied health care professionals was feasible and safe. There were no differences in achieved medication doses or indices of left ventricular remodeling. Further studies of RIM in higher-risk cohorts are warranted.

Trial Registration

ClinicalTrials.gov Identifier: NCT02468349

Reduced Jet Velocity in Venous Flow after CSF Drainage: Assessing Hemodynamic Causes of Pulsatile Tinnitus

BACKGROUND AND PURPOSE

Idiopathic intracranial hypertension is commonly associated with transverse sinus stenosis, a venous cause of pulsatile tinnitus. In patients with idiopathic intracranial hypertension, CSF drainage via lumbar puncture decreases intracranial pressure, which relieves the stenosis, and may provide at least temporary cessation of pulsatile tinnitus. The objective of this study was to evaluate changes in venous blood flow caused by lowered intracranial pressure in patients with pulsatile tinnitus to help identify the cause of pulsatile tinnitus.

MATERIALS AND METHODS

Ten patients with suspected transverse sinus stenosis as a venous etiology for pulsatile tinnitus symptoms underwent MR imaging before and after lumbar puncture in the same session. The protocol included flow assessment and rating of pulsatile tinnitus intensity before and after lumbar puncture and MR venography before lumbar puncture. Post-lumbar puncture MR venography was performed in 1 subject.

RESULTS

There was a lumbar puncture-induced reduction in venous peak velocity that correlated with the opening pressure (r = -0.72, P = .019) without a concomitant reduction in flow rate. Patients with flow jets had their peak velocity reduced by 0.30 ± 0.18 m/s (P = .002), correlating with a reduction in CSF pressure (r = 0.82, P = .024) and the reduction in subjectively scored pulsatile tinnitus intensity (r = 0.78, P = .023). The post-lumbar puncture MR venography demonstrated alleviation of the stenosis.

CONCLUSIONS

Our results show a lumbar puncture-induced reduction in venous peak velocity without a concomitant reduction in flow rate. We hypothesize that the reduction is caused by the expansion of the stenosis after lumbar puncture. Our results further show a correlation between the peak velocity and pulsatile tinnitus intensity, suggesting the flow jet to be instrumental in the development of sound.

Plasma Ceramides as Prognostic Biomarkers and Their Arterial and Myocardial Tissue Correlates in Acute Myocardial Infarction

•

Targeted profiling of ceramides identified a 12-ceramide plasma signature that predicted 12-month cardiovascular death, MI, and stroke in 2 prospective cohorts of AMI patients.

•

Among coronary artery bypass grafting patients, plasma ceramides were higher in those with recent AMI compared with those without recent acute MI.

•

Analysis of rat ischemic myocardium revealed a consistent increase in ceramide levels and overexpression of 3 enzymes in ceramide biosynthesis.

We identified a plasma signature of 11 C14 to C26 ceramides and 1 C16 dihydroceramide predictive of major adverse cardiovascular events in patients with acute myocardial infarction (AMI). Among patients undergoing coronary artery bypass surgery, those with recent AMI, compared with those without recent AMI, showed a significant increase in 5 of the signature’s 12 ceramides in plasma but not simultaneously-biopsied aortic tissue. In contrast, a rat AMI model, compared with sham control, showed a significant increase in myocardial concentrations of all 12 ceramides and up-regulation of 3 ceramide-producing enzymes, suggesting ischemic myocardium as a possible source of this ceramide signature.

Prognostic Implications of Dual Platelet Reactivity Testing in Acute Coronary Syndrome

Studies on platelet reactivity (PR) testing commonly test PR only after percutaneous coronary intervention (PCI) has been performed. There are few data on pre- and post-PCI testing. Data on simultaneous testing of aspirin and adenosine diphosphate antagonist response are conflicting. We investigated the prognostic value of combined serial assessments of high on-aspirin PR (HASPR) and high on-adenosine diphosphate receptor antagonist PR (HADPR) in patients with acute coronary syndrome (ACS). HASPR and HADPR were assessed in 928 ACS patients before (initial test) and 24 hours after (final test) coronary angiography, with or without revascularization. Patients with HASPR on the initial test, compared with those without, had significantly higher intraprocedural thrombotic events (IPTE) (8.6 vs. 1.2%, p ≤ 0.001) and higher 30-day major adverse cardiovascular and cerebrovascular events (MACCE; 5.2 vs. 2.3%, p = 0.05), but not 12-month MACCE (13.0 vs. 15.1%, p = 0.50). Patients with initial HADPR, compared with those without, had significantly higher IPTE (4.4 vs. 0.9%, p = 0.004), but not 30-day (3.5 vs. 2.3%, p = 0.32) or 12-month MACCE (14.0 vs. 12.5%, p = 0.54). The c-statistic of the Global Registry of Acute Coronary Events (GRACE) score alone, GRACE score + ASPR test and GRACE score + ADPR test for discriminating 30-day MACCE was 0.649, 0.803 and 0.757, respectively. Final ADPR was associated with 30-day MACCE among patients with intermediate-to-high GRACE score (adjusted odds ratio [OR]: 4.50, 95% confidence interval [CI]: 1.14-17.66), but not low GRACE score (adjusted OR: 1.19, 95% CI: 0.13-10.79). In conclusion, both HASPR and HADPR predict ischaemic events in ACS. This predictive utility is time-dependent and risk-dependent.

Long-Term Effectiveness of Direct CT-Guided Aspiration and Fenestration of Symptomatic Lumbar Facet Synovial Cysts

BACKGROUND AND PURPOSE

Lumbar facet synovial cysts are commonly seen in facet degenerative arthropathy and may be symptomatic when narrowing the spinal canal or compressing nerve roots. The purpose of this study was to analyze the safety, effectiveness, and long-term outcomes of direct CT-guided lumbar facet synovial cyst aspiration and fenestration for symptom relief and for obviating an operation.

MATERIALS AND METHODS

We retrospectively reviewed the medical records and imaging studies of 64 consecutive patients between 2006 and 2016 who underwent 85 CT-guided lumbar facet synovial cyst fenestration procedures in our department. We recorded patient demographics, lumbar facet synovial cyst imaging characteristics, presenting symptoms, change in symptoms after the procedure, and whether they underwent a subsequent operation. We also assessed long-term outcomes from the medical records and via follow-up telephone surveys with patients.

RESULTS

Direct CT-guided lumbar facet synovial cyst puncture was technically successful in 98% of procedures. At first postprocedural follow-up, 86% of patients had a complete or partial symptomatic response. During a mean follow-up of 49 months, 56% of patients had partial or complete long-term relief without the need for an operation; 44% of patients underwent an operation. Patients with calcified, thick-rimmed, or low T2 signal intensity cysts were less likely to respond to the procedure and more likely to need an operation.

CONCLUSIONS

CT-guided direct lumbar facet synovial cyst aspiration and fenestration procedures are safe, effective, and minimally invasive for symptomatic treatment of lumbar synovial facet cysts. This procedure obviates an operation in a substantial number of patients, even at long-term follow-up, and should be considered before surgical intervention.

Differential risk reclassification improvement by exercise testing and myocardial perfusion imaging in patients with suspected and known coronary artery disease

OBJECTIVE

The objective of this study is to compare the incremental prognostic and net risk reclassification value of exercise testing alone vs exercise myocardial perfusion imaging (MPI) for estimating the risk of death in patients with suspected and known coronary artery disease (CAD).

METHODS

6702 patients with suspected CAD and 2008 with known CAD had treadmill exercise MPI and were followed for 2.5 ± 0.9 years for the occurrence of all-cause death. The estimation of risk of death and net reclassification improvement (NRI) were examined in three models. Model 1: clinical variables; Model 2: model 1+Duke Treadmill Score; and Model 3: model 2+ MPI variables. Risk estimates were categorized as <1%, 1-3%, and >3% risk of death per year.

RESULTS

In patients with suspected CAD, the global Chi-square for predicting risk of death increased significantly for Model 2 compared to Model 1 (74.78 vs 63.86 to (P = .001). However, adding MPI variables in Model 3 did not further improve predictive value (Chi-square 79.38, P = .10). In patients with suspected CAD risk, reclassification improved significantly in Model 2 over Model 1 (NRI = 0.12, 95% CI 0.02 to 0.22, P = .019), but not in Model 3 (NRI = 0.0009, 95% CI -0.072 to 0.070; P = .98). In contrast, in patients with known CAD Model 2 did not yield significant improvements for predicting risk and risk reclassification compared to Model 1. However, global Chi-square of Model 3 was significantly higher than that of Model 2 (30.03 vs 6.56, P < .0001) with associated significant reclassification improvement (NRI = 0.26 95% CI 0.067 to 0.46. P = .0084).

CONCLUSION

Risk reclassification by diagnostic testing is importantly influenced by baseline characteristics of patient cohorts. In patients with suspected CAD, NRI is predominately achieved by exercise variables, whereas in patients with known CAD, greatest NRI is obtained by MPI variables.

Diffusivity measurements differentiate benign from malignant lesions in patients with peripheral neuropathy or plexopathy

BACKGROUND AND PURPOSE

Peripheral nerve disorders caused by benign and malignant primary nerve sheath tumors, infiltration or compression of nerves by metastatic disease, and postradiation neuritis demonstrate overlapping features on conventional MR imaging but require vastly different therapeutic approaches. We characterize and compare diffusivities of peripheral nerve lesions in patients undergoing MR neurography for peripheral neuropathy or brachial or lumbosacral plexopathy.

MATERIALS AND METHODS

Twenty-three patients, referred for MR neurography at our institution between 2003 and 2009 for a peripheral mononeuropathy or brachial or lumbosacral plexopathy and whose examinations included DWI, received a definitive diagnosis, based on biopsy results or clinical and imaging follow-up, for a masslike or infiltrative peripheral nerve or plexus lesion suspicious for tumor. Mean ADC values were determined within each lesion and compared across 3 groups (benign lesions, malignant lesions, and postradiation changes).

RESULTS

Both ANOVA and Kruskal-Wallis tests demonstrated a statistically significant difference in ADC values across the 3 groups (P = .000023, P = .00056, respectively). Post hoc pair-wise comparisons showed that the ADC within malignant tumors differed significantly from that within benign tumors and postradiation changes. ADC within benign tumors and postradiation changes did not differ significantly from each other.

CONCLUSIONS

DWI may be highly effective for the differentiation of benign from malignant peripheral nerve masslike or infiltrative lesions.

Differences in late cardiovascular mortality following acute myocardial infarction in three major Asian ethnic groups

AIM

the purpose of this study was to investigate differences in long-term mortality following acute myocardial infarction (AMI) in patients from three major ethnicities of Asia.

METHODS AND RESULTS

We studied 15,151 patients hospitalized for AMI with a median follow-up of 7.3 years (maximum 12 years) in six publicly-funded hospitals in Singapore from 2000-2005. Overall and cause-specific cardiovascular (CV) mortality until 2012 were compared among three major ethnic groups that represent large parts of Asia: Chinese, Malay and Indian. Relative survival of all three ethnic groups was compared with a contemporaneous background reference population using the relative survival ratio (RSR) method. The median global registry of acute coronary events score was highest among Chinese, followed by Malay and Indians: 144 (25th percentile 119, 75th percentile 173), 138 (115, 167), and 131 (109, 160), respectively, p<0.0001; similarly, in-hospital mortality was highest among Chinese (9.8%) followed by Malay (7.6%) and Indian (6.4%) patients. In contrast, 12-year overall and cause-specific CV mortality was highest among Malay (46.2 and 32.0%) followed by Chinese (43.0 and 27.0%) and Indian (35.9 and 25.2%) patients, p<0.0001. The five-year RSR was lowest among Malay (RSR 0.69) followed by Chinese (RSR 0.73) and Indian (RSR 0.79) patients, compared with a background reference population (RSR 1.00).

CONCLUSIONS

We observed strong inter-Asian ethnic disparities in long-term mortality after AMI. Malay patients had the most discordant relationship between baseline risk and long-term mortality. Intensified interventions targeting Malay patients as a high-risk group are necessary to reduce disparities in long-term outcomes.

Reducing patient radiation dose during CT-guided procedures: demonstration in spinal injections for pain

BACKGROUND AND PURPOSE

CT guidance may improve precision for diagnostic and therapeutic spinal injections, but it can increase patient radiation dose. This study examined the impact of reducing tube current on patient radiation exposure and the technical success for these procedures, by using axial acquisitions for short scan lengths and eliminating nonessential imaging.

MATERIALS AND METHODS

Our institutional review board approved retrospective analysis of records from 100 consecutive outpatients undergoing spinal injections for pain before and after the CT protocol modification to reduce radiation dose. Data collected included patient age and sex, response to injection, number of sites and spinal levels treated, injection type, performing physician, CT acquisition method, number of imaging series, tube current, scan length, and DLP.

RESULTS

Image contrast was reduced with the low-dose protocol, but this did not affect technical success or immediate pain relief. Mean DLP for all procedures decreased from 1458 ± 1022 to 199 ± 101 mGy · cm (P < .001). The range of radiologist-dependent DLP per procedure also was reduced significantly with the modified protocol. Selective nerve root blocks, lumbar injections, multiple injection sites, and the lack of prior imaging were each associated with a slightly higher DLP (<50 mGy · cm).

CONCLUSIONS

Radiation to patients undergoing CT-guided spinal injections can be decreased significantly without affecting outcome by reducing tube current, using axial acquisitions for short scan lengths, and eliminating nonessential imaging guidance. These measures also decrease variability in radiation doses between different practitioners and should be useful for other CT-guided procedures in radiology.

Controlled hypothermia in post-resuscitation management: what is so cool about it?

Survivors of successful resuscitated cardiac arrest have a high incidence of severe neurological deficits. The pathophysiology of cerebral injury is thought to be multifactorial, and therapeutic mild hypothermia is one of the strategies that have been shown to minimise this complication. In this article, we outline the theoretical basis for this strategy as well as the clinical evidence to support current practice guidelines advocating its use. We also review the technical aspects of implementing hypothermia after resuscitation as well as the potential side effects. Finally, unresolved issues are discussed as we outline the ongoing prospective clinical trial underway in Singapore in order to evaluate its safety and efficacy in our local population. We advocate further research into this topic, as it has great potential to improve the outcomes of comatose resuscitated patients of cardiac arrest.

Reduced field-of-view diffusion imaging of the human spinal cord: comparison with conventional single-shot echo-planar imaging

BACKGROUND AND PURPOSE

DWI of the spinal cord is challenging because of its small size and artifacts associated with the most commonly used clinical imaging method, SS-EPI. We evaluated the performance of rFOV spinal cord DWI and compared it with the routine fFOV SS-EPI in a clinical population.

MATERIALS AND METHODS

Thirty-six clinical patients underwent 1.5T MR imaging examination that included rFOV SS-EPI DWI of the cervical spinal cord as well as 2 comparison diffusion sequences: fFOV SS-EPI DWI normalized for either image readout time (low-resolution fFOV) or spatial resolution (high-resolution fFOV). ADC maps were created and compared between the methods by using single-factor analysis of variance. Two neuroradiologists blinded to sequence type rated the 3 DWI methods, based on susceptibility artifacts, perceived spatial resolution, signal intensity-to-noise ratio, anatomic detail, and clinical utility.

RESULTS

ADC values for the rFOV and both fFOV sequences were not statistically different (rFOV: 1.01 ± 0.18 × 10(-3) mm(2)/s; low-resolution fFOV: 1.12 ± 0.22 × 10(-3) mm(2)/s; high-resolution fFOV: 1.10 ± 0.21 × 10(-3) mm(2)/s; F = 2.747, P > .05). The neuroradiologist reviewers rated the rFOV diffusion images superior in terms of all assessed measures (P < 0.0001). Particular improvements were noted in patients with metal hardware, degenerative disease, or both.

CONCLUSIONS

rFOV DWI of the spinal cord overcomes many of the problems associated with conventional fFOV SS-EPI and is feasible in a clinical population. From a clinical standpoint, images were deemed superior to those created by using standard fFOV methods.

Focused ultrasound and microbubbles for enhanced extravasation

The permeability of blood vessels for albumin can be altered by using ultrasound and polymer or lipid-shelled microbubbles. The region in which the microbubbles were destroyed with focused ultrasound was quantified in gel phantoms as a function of pressure, number of cycles and type of microbubble. At 2MPa the destruction took place in a fairly wide area for a lipid-shelled agent, while for polymer-shelled agents at this setting, distinct destruction spots with a radius of only 1mm were obtained. When microbubbles with a thicker shell were used, the pressure above which the bubbles were destroyed shifts to higher values. In vivo both lipid and polymer microbubbles increased the extravasation of the albumin binding dye Evans Blue, especially in muscle leading to about 6-8% of the injected dose to extravasate per gram muscle tissue 30 min after start of the treatment, while no Evans Blue could be detected in muscle in the absence of microbubbles. Variation in the time between ultrasound treatment and Evans Blue injection, demonstrated that the time window for promoting extravasation is at least an hour at the settings used. In MC38 tumors, extravasation already occurred without ultrasound and only a trend towards enhancement with about a factor of 2 could be established with a maximum percentage injected dose per gram of 3%. Ultrasound mediated microbubble destruction especially enhances the extravasation in the highly vascularized outer part of the MC38 tumor and adjacent muscle and would, therefore, be most useful for release of, for instance, anti-angiogenic drugs.

Drosophila CAPS is an essential gene that regulates dense-core vesicle release and synaptic vesicle fusion

Calcium-activated protein for secretion (CAPS) is proposed to play an essential role in Ca2+-regulated dense-core vesicle exocytosis in vertebrate neuroendocrine cells. Here we report the cloning, mutation, and characterization of the Drosophila ortholog (dCAPS). Null dCAPS mutants display locomotory deficits and complete embryonic lethality. The mutant NMJ reveals a 50% loss in evoked glutamatergic transmission, and an accumulation of synaptic vesicles at active zones. Importantly, dCAPS mutants display a highly specific 3-fold accumulation of dense-core vesicles in synaptic terminals, which was not observed in mutants that completely arrest synaptic vesicle exocytosis. Targeted transgenic CAPS expression in identified motoneurons fails to rescue dCAPS neurotransmission defects, demonstrating a cell nonautonomous role in synaptic vesicle fusion. We conclude that dCAPS is required for dense-core vesicle release and that a dCAPS-dependent mechanism modulates synaptic vesicle release at glutamatergic synapses.

Predicting the acoustic response of a microbubble population for contrast imaging in medical ultrasound

Although the behavior of a bubble in an acoustic field has been studied extensively, few theoretical treatments to date have been applied to simulate the acoustic response of a real population of variably sized microbubbles in a finite-width sound beam. In this paper, we present a modified Trilling equation for single bubble dynamics that has been solved numerically for different conditions. Radiated waveforms from a large number of such bubbles are combined, reflecting their size distribution and location and the shape of a real acoustic beam. The resulting time-domain pressure waveforms can be compared with those obtained experimentally. The dependence of second-harmonic radiation on incident focal amplitude at different frequencies is presented. This model is particularly suited to the study of interaction between a medical ultrasound beam and microbubble contrast agents in aqueous media.

Growth of Qinghai Tibetans living at three different high altitudes

This study compares the stature, weight, skinfolds, upper arm muscle area, and chest dimensions of Tibetan children, adolescents, and young adults who were born and raised, or who had lived from infancy, at 3,200 m, 3,800 m, and 4,300 m in Qinghai Province, People's Republic of China. While the individuals measured in Qinghai are among the tallest and heaviest Tibetans reported in the literature, they are nevertheless smaller and lighter than well-off children living at low altitude. The pattern of size variation among Tibetan males and females measured at the three high altitudes, along with evidence of a secular trend at 4,300 m, suggests that nutrition may significantly effect growth at high altitude. Only minor differences in thorax dimensions exist between Tibetan males and females measured at 3,200 m and 3,800 m. However, Tibetan males at 4,300 m possess slightly narrower and deeper chests (during and after adolescence) than males at 3,200 m and 3,800 m. Since individuals from 3,800 m and 4,300 m belong to the same local populations, this characteristic is unlikely to be genetically determined. However, it may be related to differences in the degree of hypoxia or to the influences of other environmental conditions.

Pediatric Chiari I malformations: do clinical and radiologic features correlate?

BACKGROUND

Although Chiari I malformation is increasingly recognized in children, little is known about its clinical presentation in this age group.

OBJECTIVE

To evaluate the relationship between clinical and MRI features of pediatric Chiari I malformations.

METHODS

We performed a chart review and MRI analysis of 49 children with Chiari I malformation. The degree of tonsillar ectopia was compared with age at onset, presence of syringomyelia, and a neurologic severity score as follows: asymptomatic = 0, symptomatic with normal neurologic examination = 1, and symptomatic with abnormal examination = 2.

RESULTS

Age at onset of symptoms ranged from 10 months to 14 years. Fifty-seven percent of patients were asymptomatic. Headache and neck pain were the most frequent complaints. Syringomyelia was detected in 14% of patients and skull base abnormalities in 50%. The magnitude of tonsillar ectopia (5 to 23 mm) correlated with severity score (p = 0.04) but not with other clinical measures.

CONCLUSIONS

The clinical symptoms of Chiari I malformations in children are nearly identical to those seen in adults. Children with greater amounts of tonsillar ectopia on MRI are more likely to be symptomatic.

Pulse inversion Doppler: a new method for detecting nonlinear echoes from microbubble contrast agents

A novel technique for the selective detection of ultrasound contrast agents, called pulse inversion Doppler, has been developed. In this technique, a conventional Doppler or color Doppler pulse sequence is modified by inverting every second transmit pulse. Either conventional or harmonic Doppler processing is then performed on the received echoes. In the resulting Doppler spectra, Doppler shifts from linear and nonlinear scattering are separated into two distinct regions that can be analyzed separately or combined to estimate the ratio of nonlinear to linear scattering from a region of tissue. The maximum Doppler shift that can be detected is 1/2 the normal Nyquist limit. This has the advantage over conventional harmonic Doppler that it can function over the entire bandwidth of the echo signal, thus achieving superior spatial resolution in the Doppler image. In vitro measurements comparing flowing agent and cellulose particles suggest that pulse inversion Doppler can provide 3 to 10 dB more agent to tissue contrast than harmonic imaging with similar pulses. Similar measurements suggest that broadband pulse inversion Doppler can provide up to 16 dB more contrast than broadband conventional Doppler. Nonlinear propagation effects limit the maximum contrast obtainable with both harmonic and pulse inversion Doppler techniques.

Usefulness of contrast material in MR of patients with neurofibromatosis type 1

PURPOSE

Our objective was to determine the usefulness of routine administration of contrast material in brain MR imaging for the evaluation of areas of probable myelin vacuolization and neoplasms in patients with neurofibromatosis type 1 (NF-1).

METHODS

We retrospectively reviewed 112 consecutive contrast-enhanced brain MR studies obtained over a period of 7 years in 109 symptomatic and asymptomatic patients compiled from two institutional NF-1 data bases. MR studies were analyzed for areas of probable myelin vacuolization, with attention to degree of enhancement and its impact on lesion detection and characterization. Usefulness of contrast material was graded as 0 = not useful, 1+ = somewhat useful, and 2+ = useful.

RESULTS

Of 112 studies, 45% (n = 49) were normal. In the remaining 63 studies, 88 regions of probable myelin vacuolization and 52 tumors were identified. Enhancement was not observed in any regions of probable myelin vacuolization. Enhancement was present in 31% of tumors, and, of these, was found to be useful in 44%, somewhat useful in 12%, and not useful in 44%. For enhancing tumors, contrast agent was useful for lesion detection in 19% and for lesion characterization in 25%.

CONCLUSION

Contrast administration is useful in baseline MR studies to maximize tumor detection and characterization, to add confidence to the diagnosis of benign probable myelin vacuolization, and to document stability of neoplasms on follow-up examinations.

Gallbladder nonvisualization with pericholecystic rim sign: morphine-augmentation optimizes diagnosis of acute cholecystitis

This study investigated the value of morphine-augmentation in patients who demonstrated gallbladder nonvisualization with a pericholecystic rim sign at 1 hr, a cholescintigraphic pattern considered highly predictive of acute cholecystitis.

METHODS

Retrospectively, 170 consecutive morphine-augmented cholescintigrams were analyzed for the presence of a pericholecystic rim sign, marked or mild, associated with gallbladder nonvisualization at 1 hr (before morphine); those with a pericholecystic rim sign were further evaluated for persistent gallbladder nonvisualization versus gallbladder visualization after morphine. Scintigraphic interpretations were correlated with surgical pathology or clinical diagnosis.

RESULTS

Before morphine, 43/170 (25%) patients demonstrated gallbladder nonvisualization with a pericholecystic rim sign. Since only 31 had acute cholecystitis, a diagnosis based solely on that scintigraphic pattern would have resulted in 12 false-positives. After morphine, gallbladder visualization correctly excluded acute cholecystitis in seven; a single false-negative was encountered; five false-positives remained. Morphine-augmentation improved the positive predictive value from 72% (gallbladder nonvisualization with pericholecystic rim sign before morphine) to 86% (gallbladder nonvisualization after morphine). Of 24 patients with marked pericholecystic rim signs, 21 had acute cholecystitis. Of 31 with acute cholecystitis, however, 10 (32%) had a mild pericholecystic rim sign.

CONCLUSION

Morphine-augmented cholescintigraphy optimizes the diagnosis of acute cholecystitis in patients with the suggestive, but not pathognomonic, cholescintigraphic pattern at 1 hr of gallbladder nonvisualization with a pericholecystic rim sign, regardless of its intensity.

Serological evidence of Hantaan virus infection in the United States

We found low titers of fluorescent antibodies against Hantaan virus, the etiologic agent of Korean hemorrhagic fever, in sera from 7 of 1,035 patients with febrile illnesses of unknown origin and from 6 of 664 blood donors in the United States. All but 1 of these individuals possessed neutralizing antibodies against Hantaan virus. This was a 31-year-old research technician who had worked with laboratory rodents with virus-induced tumors, but had not traveled abroad, suggesting that infection with Hantaan virus or a closely related agent was locally acquired. However, the precise source of his infection remains unclear.

The effects of betel-nut chewing on the buccal mucosa: a histological study

Sixty-two "leukoplakias" from the cheeks of betel-nut chewers in West Malaysia were studied histologically. Ten biopsies were from non-tobacco betel-nut chewers. An amorphous von Kossa positive layer was seen on the keratin surface in 42 specimens. Tobacco did not appear essential for its formation, and it appeared to be significantly associated with parakeratosis. Its possible significance as a cuticle-like layer prolonging contact between carcinogens and the mucosa is discussed.Parakeratosis appeared to be the most common form of cornification seen, and the mitotic activity in parakeratinized leukoplakias appeared to be significantly greater than orthokeratinized leukoplakias.Comparison with studies on other population samples using different quids suggested that severe histological changes were more likely to be seen when tobacoo-containing quids were chewed as compared to non-tobacco-containing quids.An attempt to correlate the histological changes seen with the clinical habit in leukoplakias from chewers using tobacco-containing quids suggested that epithelial atrophy appeared to be significantly related to the duration of the habit but not to the "intensity" of the habit.

The effects of betel-nut chewing on the buccal mucosa of 296 Indians and Malays in West Malaysia. A clinical study

Changes in the buccal mucosa of 296 Indian and Malay betel-nut chewers in Perak, West Malaysia, were studied clinically. 167 out of 212 Indian subjects incorporated tobacco in their quids, while 45 out of 84 Malay subjects incorporated. "Gambir". The Indians appeared to show a higher proportion of mucosal changes, particularly when tobacco was used. "Gambir" did not appear to be potent in the production of mucosal changes. Comparison with studies in other parts of the world suggested comparable findings with respect to both tobacco and non-tobacco chewing samples, and there would appear to be some evidence that tobacco-containing quids are likely to produce a higher proportion of mucosal changes as compared to non-tobacco-containing quids. An attempt to demonstrate a dose-effect relationship by dividing the subjects into "slight" and "heavy" chewers did not yield significant differences between these two categories in each of the groups.