Navigator assessment of breath-hold duration: impact of supplemental oxygen and hyperventilation.
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Adult↗
Biomedical subjects
W J Manning
Publications and source records attributed to W J Manning.
Impact of respiratory maneuvers on cardiac volume within left-breast radiation portals.
BACKGROUND: Late cardiac morbidity and mortality have been reported among left-breast cancer survivors treated with radiation therapy. Radiation-induced cardiotoxicity is affected by the volume of myocardium included in the radiation portals. We hypothesize that simple respiratory maneuvers may alter the position of the heart relative to the portals without altering the radiation dose delivered to the breast. METHODS AND RESULTS: Fourteen healthy female adult volunteers underwent cardiac MRI to determine the cardiac volume included in the typical left-breast radiation field during respiratory maneuvers. Cardiac volume within the radiation portals was assessed from a transverse stack of 14 1-cm-thick contiguous slices covering the entire heart, obtained during breath holding at end-tidal volume (baseline), deep inspiration, and forced expiration. Thirteen subjects (92%) had inclusion of a portion of the heart within the radiation portals at end-tidal volume (median, 20.9 cm3; range, 1.3 to 88.4 cm3). In these subjects, inspiration decreased the cardiac volume included within the radiation portals (median change: -10.7 cm3 [-40.2%], P<.001 versus end-tidal volume), whereas expiration increased the cardiac volume included (median change: 4.0 cm3 [21.5%]; P<.001 versus end-tidal volume). CONCLUSIONS: Inclusion of a portion of the heart in the left-breast radiation field is common. The use of simple inspiratory maneuvers significantly decreases cardiac volume within the radiation portals. Such an approach during delivery of radiation therapy may allow for preservation of radiation dosage to the breast while reducing cardiac involvement and subsequent mortality.
Adult↗
Role of transesophageal echocardiography in the management of thromboembolic stroke.
Cardiac causes of stroke account for approximately 20% of strokes occurring in the United States. Transthoracic echocardiography (TTE) remains the cornerstone of non-invasive cardiac imaging, but transesophageal echocardiography (TEE) is superior for identifying potential cardiac sources of emboli, including left atrial thrombi, valvular vegetations, thoracic aortic plaque, patent foramen ovale, and spontaneous left atrial echocardiographic contrast. The diagnostic yield of TEE for potential cardiac causes of thromboembolism exceeds 50%. The impact of TEE on the clinical management of this group, however, remains undefined for most TEE-specific diagnoses. Thus, routine use of TEE in these patients has been questioned. The diagnostic yield is highest if the clinical history/physical examination suggests a cardiac source. However, the clinical scenario often dictates patient management, and TEE data are used to "validate" the clinical impression. Data from large, prospective, randomized (aspirin/warfarin) studies, in which TEE data are obtained from patients with suspected cardiac thromboembolism, are needed. If specific TEE diagnoses can be identified in which defined therapies are beneficial, "source of embolism" will continue to be the most common indication for TEE referral. In this paradigm, TEE (without initial TTE) will probably become a more direct diagnostic pathway. However, if these studies demonstrate that all patients with suspected cardiac source benefit from one (or no) therapy, independent of TEE data, referrals for TEE will decline. Results of ongoing randomized trials to evaluate the efficacy of TEE in patients with cryptogenic stroke or transient ischemic attack are awaited.
Anticoagulants↗
Risk for clinical thromboembolism associated with conversion to sinus rhythm in patients with atrial fibrillation lasting less than 48 hours.
BACKGROUND: It has been assumed that cardioversion in patients with atrial fibrillation lasting less than 48 hours is associated with a low risk for thromboembolism. However, no clinical data support this assumption. OBJECTIVE: To determine the incidence of cardioversion-related clinical thromboembolism among patients presenting with atrial fibrillation lasting less than 48 hours. DESIGN: Patients were prospectively identified on admission, and clinical data on the duration of atrial fibrillation were recorded. Data on cardioversion and thromboembolism were obtained retrospectively from hospital and outpatient records. SETTING: Academic medical center. PATIENTS: 1822 consecutive patients admitted to the hospital for atrial fibrillation were screened. Three hundred seventy-five adults (mean age +/- SD, 68 +/- 16 years) with atrial fibrillation that had lasted less than 48 hours were identified. One hundred eighty-one patients (48.3%) had a history of atrial fibrillation; 23 (6.1%) had a history of thromboembolism. RESULTS: 357 patients (95.2%) converted to sinus rhythm during the index admission; spontaneous conversion occurred in 250 patients (66.7%) and active pharmacologic or electrical conversion was done in 107 patients (28.5%). Three patients (0.8% [95% CI, 0.2% to 2.4%]), all of whom had converted spontaneously after ventricular rate control was begun, had a clinical thromboembolic event: One had a stroke, 1 had a transient ischemic attack, and 1 had a peripheral embolus. None of these 3 patients had a history of atrial fibrillation or thromboembolism, and all had normal left ventricular systolic function. CONCLUSION: Among patients presenting with atrial fibrillation that was clinically estimated to have lasted less than 48 hours, the likelihood of cardioversion-related clinical thromboembolism is low. These data support the current recommendation for early cardioversion in these patients.
Adult↗
Prospective adaptive navigator correction for breath-hold MR coronary angiography.
Current MR coronary angiography (MRCA) methods use breath-holding to minimize respiratory motion. A major limitation to this technique is misregistration between imaging slices due to breath-hold variability. Prospective adaptive correction of image location using real-time navigator measurement of diaphragm position is a potential method for improving slice registration in breath-hold MRCA. Ten subjects underwent MRCA using an ECG-gated, fat-suppressed, segmented k-space, gradient-echo sequence. Transverse and coronal images were acquired using standard breath-holding with and without prospective navigator correction. Breath-hold MRCA with prospective navigator correction resulted in a 47% reduction in craniocaudal slice registration error compared to standard breath-holding (0.9 +/- 0.2 mm versus 1.7 +/- 0.4 mm, P = 0.04). Prospective adaptive navigator correction of image location significantly improves slice registration for breath-hold MRCA and is a promising motion correction technique for cardiac MR.
Adult↗
Simultaneous acquisition of spatial harmonics (SMASH): fast imaging with radiofrequency coil arrays.
SiMultaneous Acquisition of Spatial Harmonics (SMASH) is a new fast-imaging technique that increases MR image acquisition speed by an integer factor over existing fast-imaging methods, without significant sacrifices in spatial resolution or signal-to-noise ratio. Image acquisition time is reduced by exploiting spatial information inherent in the geometry of a surface coil array to substitute for some of the phase encoding usually produced by magnetic field gradients. This allows for partially parallel image acquisitions using many of the existing fast-imaging sequences. Unlike the data combination algorithms of prior proposals for parallel imaging, SMASH reconstruction involves a small set of MR signal combinations prior to Fourier transformation, which can be advantageous for artifact handling and practical implementation. A twofold savings in image acquisition time is demonstrated here using commercial phased array coils on two different MR-imaging systems. Larger time savings factors can be expected for appropriate coil designs.
Abdomen↗
Cost-effectiveness of transesophageal echocardiographic-guided cardioversion: a decision analytic model for patients admitted to the hospital with atrial fibrillation.
OBJECTIVES: Using a decision-analytic model, we sought to examine the cost-effectiveness of three strategies for cardioversion of patients admitted to the hospital with atrial fibrillation. BACKGROUND: Transesophageal echocardiographic (TEE)-guided cardioversion has been proposed as a method for early cardioversion of patients with atrial fibrillation. The cost-effectiveness of this approach, relative to conventional therapy, has not been studied. METHODS: We ascertained the cost per quality-adjusted life-year (QALY) of three strategies: 1) conventional therapy--transthoracic echocardiography (TTE) and warfarin therapy for 1 month before cardioversion; 2) initial TTE, followed by TEE and early cardioversion if no thrombus is detected; 3) initial TEE, with early cardioversion if no thrombus is detected. With strategies 2 and 3, if a thrombus is seen, follow-up TEE is performed. If no thrombus is seen, cardioversion is then performed. All strategies utilized anticoagulation before and extending for 1 month after cardioversion. Life expectancy, utilities (quality-of-life weights) and event probabilities were ascertained from published reports. Cost estimates were based on published data and hospital accounting information. RESULTS: Transesophageal echocardiographic-guided early cardioversion (strategy 3: cost $2,774, QALY 8.49) dominates TTE/TEE-guided cardioversion (strategy 2: cost $3,106, QALY 8.48) and conventional therapy (strategy 1: cost $3,070, QALY 8.48) because it is the least costly with similar effectiveness. Sensitivity analyses demonstrated that TEE-guided cardioversion (strategy 3) dominates conventional therapy if the risk of stroke after TEE negative for atrial thrombus is slightly less than that after conventional therapy (baseline estimate 0.8%). The results also depend on the risk of major hemorrhage but are less sensitive to baseline estimates of morbidity from TEE, cost of TTE, cost of hospital admission for cardioversion and utilities for health states. CONCLUSIONS: On the basis of a decision-analytic model, TEE-guided early cardioversion, without TTE, is a reasonable cost-saving alternative to conventional therapy for patients admitted to the hospital with atrial fibrillation. Such a strategy appears particularly beneficial for patients with an increased risk of hemorrhagic complications. Future clinical studies examining the TEE strategy should consider eliminating initial TTE and carefully assess both the thromboembolic and hemorrhagic risk.
Aged↗
Prospective navigator correction of image position for coronary MR angiography.
PURPOSE: To determine the potential benefit of prospective navigator correction of image position for coronary magnetic resonance (MR) angiography. MATERIALS AND METHODS: Two-dimensional MR angiograms were obtained with free breathing in 12 adult subjects. Navigator gating was used with and without prospective correction and with gating windows set at 3, 5, and 7 mm. MR angiograms were compared with those obtained with conventional, end-expiratory breath holding. RESULTS: Navigator gating with correction resulted in image quality equivalent to that obtained with breath holding, even with the 7-mm gating window. In contrast, navigator gating without correction allowed only maintenance of image quality similar to that obtained with breath holding for the 3- and 5-mm windows and resulted in decreased image quality with the 7-mm window (P < .05). Use of navigator gating with correction and the 7-mm window resulted in a 28% decrease in imaging time compared with breath holding and a 33% decrease compared with the 3-mm gating window (P < .05 for both comparisons). CONCLUSION: Prospective, adaptive navigator correction of image position for free-breathing coronary MR angiography is a promising, novel approach to compensate for respiratory motion.
Adult↗
Comparison of respiratory suppression methods and navigator locations for MR coronary angiography.
OBJECTIVE: Currently, breath-holding during MR coronary angiography is used to minimize respiratory motion. This technique requires patient cooperation and is associated with slice registration errors. The goal of this study was to evaluate alternative non-breath-hold techniques for MR coronary angiography during free breathing. SUBJECTS AND METHODS: Subjects underwent MR coronary angiography using an ECG-gated, fat-suppressed, segmented K-space, gradient-echo sequence. Images were obtained during free breathing using both real-time navigator gating and respiratory bellows gating. These were compared with images obtained during conventional breath-holding. The optimal navigator location (diaphragmatic or cardiac) was also studied. Image quality, registration error, and scan time were measured for all scans. RESULTS: Navigator gating for MR coronary angiography during free breathing resulted in image quality equivalent to that obtained during breath-holding and was superior to that obtained with respiratory bellows gating (p < .04). Also, navigator gating reduced registration errors by 75% compared with breath-holding (p < .01) and did not increase scan time. No significant differences in the parameters measured were observed among the different navigator locations. CONCLUSION: Real-time navigator gating for MR coronary angiography during free breathing achieved image quality and scan time equivalent to breath-holding. Navigator gating also significantly reduced registration error. Compared with breath-holding and respiratory bellows gating, navigator gating during free breathing is a more optimal approach for suppression of respiratory motion during MR coronary angiography.
Adult↗
Evaluation of left atrial appendage anatomy and function in recent-onset atrial fibrillation by transesophageal echocardiography.
Data regarding left atrial (LA) and LA appendage anatomy and function among patients with newly recognized atrial fibrillation (AF) who have not received long-term warfarin are currently unknown. To identify echocardiographic indexes which characterize those at increased risk for thrombus formation, we analyzed transesophageal echocardiographic studies in 100 consecutive patients with newly recognized AF (duration 2.6 +/- 0.3 week) who had not received long-term warfarin. Fourteen percent of patients had LA thrombi. LA thrombi were associated with larger LA appendages, more depressed LA appendage outflow velocities, and a higher prevalence of severe spontaneous LA contrast. Patients with spontaneous contrast had larger LA and LA appendage anatomy and lower LA appendage ejection velocity. Among patients presenting with their first episode of AF, greater LA appendage ejection and filling velocities and smaller LA and LA appendage sizes were seen among those with AF of <2 weeks duration compared with those with AF of >2 weeks. Thus, patients with recent onset AF and LA thrombi or spontaneous echo contrast have more dilated LA and LA appendage anatomy, and more depressed LA appendage systolic function. Data from patients with their first episode of AF suggests that AF is associated with rapid LA remodeling.
Adult↗
Olestra and the FDA.
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Contraindications↗
Ambient ozone (O3) in three Class I wilderness areas in the northeastern USA: measurements with Ogawa passive samplers.
Ambient ozone (O(3)) was measured in two Class I wilderness areas, one within the White Mountain National Forest in north central New Hampshire (NH) and one within the Green Mountain National Forest in southwestern Vermont (VT), for six weeks between 5 July and 16 August 1994, using Ogawa passive nitrite-coated filter samplers and a one week exposure period each time. Results for 7-day mean ambient O(3) concentrations from the passive samplers were compared to results from a co-located continuous ultraviolet photometric O(3) analyzer both in NH and VT. Although the size of the data set was small, agreement through simple linear regression between mean 7-day O(3) concentrations determined by the continuous monitors, and those obtained from the passive samplers was generally very good (adjusted R(2) = 0.759; p = 0.0003). Overall, excluding the one outlier value, any observed differences in the results obtained by the two methods when comparing co-located passive samplers to the continuous monitor within a given study location, appeared to be solely due to experimental error.
Journal Article↗
Cardiac risk of noncardiac surgery in patients with asymmetric septal hypertrophy.
BACKGROUND: Many data are available regarding cardiac risk in patients with coronary artery disease undergoing noncardiac surgery, but few data are available regarding risk for patients with hypertrophic cardiomyopathy and asymmetric septal hypertrophy. METHODS: Seventy-seven patients with asymmetric septal hypertrophy were identified in whom an echocardiogram had been performed within 24 months of noncardiac surgery. Patients' charts were reviewed for data regarding surgical operations, including length of surgery, type of anesthesia, and intravascular monitoring used. Data regarding adverse perioperative cardiac events also were gathered. RESULTS: Forty percent (n = 31) of patients had one or more adverse perioperative cardiac events, including one patient who had a myocardial infarction and ventricular tachycardia that required emergent cardioversion. There were no perioperative deaths. All 31 patients had minor outcomes. Of the 77 patients, perioperative congestive heart failure developed in 12 (16%). Factors associated with adverse cardiac events were increasing length of surgical time (P < 0.01) major surgery (P < 0.05), and intensity of monitoring (P < 0.05). Age, gender, resting outflow tract gradient, systolic anterior motion of the anterior mitral leaflet, prior myocardial infarction, severity of mitral regurgitation, type of anesthetic, septal thickness, and the interval between echocardiogram and surgery were not associated with the occurrence of adverse cardiac events. CONCLUSION: Patients with asymmetric septal hypertrophy undergoing noncardiac surgery have a high incidence of adverse cardiac events, frequently manifested as congestive heart failure. However, irreversible cardiac morbidity and mortality was extremely low. Important independent risk factors for adverse outcome in all patients include major surgery and increasing duration of surgery.
Adult↗
Antithrombotic therapy in atrial fibrillation.
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Anticoagulants↗
Magnetic resonance coronary angiography in heart transplant recipients.
BACKGROUND: Annual coronary angiography is routinely performed to evaluate cardiac allografts. Recently, magnetic resonance coronary angiography has been used to imagine native coronary arteries, but its use in transplant recipients, with rapid heart rates, metallic sternal sutures, and altered cardiac orientation, has not been described. Our goal was to describe the feasibility of noninvasive magnetic resonance coronary angiography in cardiac allograft recipients, detect flow-limiting focal stenoses, and quantify the altered coronary artery orientation. METHODS AND RESULTS: We performed magnetic resonance coronary angiography is 18 adult heart transplant recipients (15 men and 3 women) with use of a breath-hold ECG-gated segmented k-space technique. Multiple transverse and oblique images were obtained in each subject. A control population of 16 adult patients without transplant and without angiographic evidence of coronary disease provided a reference for the coronary artery length visualized by magnetic resonance coronary angiography. This technique identified the left main coronary artery in 15 of 15 transplant recipients with normal coronary anatomy. Magnetic resonance coronary angiography demonstrated a +25-degree anterior (clockwise) right coronary artery ostial rotation in transplant recipients (p = 0.0001 versus control group) with corresponding realignment of the left main ostium. By magnetic resonance coronary angiography, the mean contiguous length of coronary artery visualized in the transplant recipients was similar to that in the control subjects for all major vessels (p = not significant). Five transplant recipients had nine discrete stenoses (50% or greater luminal diameter) identified by contrast angiography, of which seven stenoses were identified as signal voids by magnetic resonance coronary angiography. coronary stenoses not seen by this technique were located in the distal one third of the artery. CONCLUSIONS: These data confirm and for the first time quantify the previously observed anterior rotation of the coronary ostia, which may be used to guide coronary engagement for subsequent interventions. In addition, these data demonstrate the potential of magnetic resonance coronary angiography to image noninvasively the coronary arteries and identify focal stenoses in cardiac allograft recipients.
Adolescent↗
Identification of anomalous coronary arteries and their anatomic course by magnetic resonance coronary angiography.
BACKGROUND: Anomalous coronary arteries are a rare but recognized cause of myocardial ischemia and sudden death. Identification currently requires x-ray angiography, which may have difficulty defining the three-dimensional course of the anomalous vessel. Magnetic resonance coronary angiography (MRCA) has been shown to image coronary artery anatomy noninvasively. We hypothesize that MRCA may be useful in the identification of anomalous coronary arteries and their anatomic course. METHODS AND RESULTS: Sixteen patients (9 men, 7 women, age 44 to 81 years) with anomalous aortic origins of the coronary arteries by conventional x-ray angiography underwent MRCA. Multiple images of the major epicardial coronary arteries were obtained by use of a breathhold, fat-suppressed, segmented-k space, gradient-echo technique by investigators blinded to all patient data. Anomalous coronary artery pathology, by x-ray angiography, included right-sided left main coronary artery (n = 3), right-sided left circumflex artery (n = 6), separate left-sided left anterior descending and left circumflex arteries (n = 2), left-sided right coronary artery (n = 4), and an anteriorly displaced right coronary artery (n = 1). MRCA correctly identified the anomalous coronary vessel(s) in 14 of 15 patients. In 1 patient, the anomalous vessel was incorrectly identified, and in 2 patients the course of the anomalous vessel was not clearly seen; one of these was a nondominant, anomalous right coronary artery. CONCLUSIONS: MRCA is a useful technique for the noninvasive identification of anomalous coronary arteries and their anatomic course.
Adult↗
Accuracy of transesophageal echocardiography for identifying left atrial thrombi. A prospective, intraoperative study.
OBJECTIVE: To determine the ability of transesophageal echocardiography to accurately identify or exclude left atrial thrombi. DESIGN: Prospective cohort study. SETTING: University hospital. PATIENTS: 231 consecutive patients having transesophageal echocardiography before elective repair or replacement of the mitral valve or excision of a left atrial tumor. Fifty-six percent of patients had a history of atrial fibrillation, and 17% had a history of thromboembolism. MEASUREMENT: Identification of left atrial thrombi during transesophageal echocardiographic examination and comparison with direct near-simultaneous visualization during cardiac surgery. RESULTS: Transesophageal echocardiography identified 14 left atrial thrombi in 14 patients (6%). Thrombus size range from 3 to 80 mm. Surgery confirmed 12 of 14 thrombi (86%), including 9 thrombi confined to the left appendage. No additional thrombi were found on direct inspection of the atria (sensitivity, 100% [95% CI, 74% to 100%]; specificity, 99% [CI, 97% to 99.9%]; positive predictive value, 86% [12/14]; negative predictive value, 100% [217/217]; for a population that had a 5.2% prevalence of thrombi). All 12 surgically confirmed thrombi were identified by two independent observers. Neither thrombus seen by only a single observer on transesophageal echocardiography was confirmed during direct inspection of the atria at surgery. CONCLUSION: Transesophageal echocardiography is highly accurate for identifying left atrial thrombi and can be used clinically to exclude left atrial thrombi.
Adult↗
Prevalence of residual left atrial thrombi among patients with acute thromboembolism and newly recognized atrial fibrillation.
BACKGROUND: Thromboembolism related to atrial fibrillation (AF) is a major cause of morbidity and mortality. Patients with acute thromboembolism and AF are at high risk for early recurrent events. OBJECTIVE: To determine the prevalence of left atrial thrombi in patients who had acute thromboembolism and newly diagnosed AF. PATIENTS AND METHODS: Adult inpatients with AF were screened to identify those with acute (< 36 hours) systemic thromboembolism and newly recognized AF. Of 41 qualifying patients, 31 (76%) agreed to undergo transesophageal echocardiographic study, including 24 with acute neurologic events and seven with peripheral thromboembolism. A control population consisted of 88 adults with newly recognized AF without clinical thromboembolism. RESULTS: Transesophageal echocardiography identified left atrial thrombi in 13 (43%) of the 30 study patients who underwent transesophageal echocardiography compared with nine (10%) of 87 controls (P < .001). Spontaneous echo contrast was identified in 27 (87%) of the study population vs 42 (48%) of controls (P < .001). The prevalence of this marker of blood stasis did not differ between patients with left atrial thrombi without thromboembolism (P = .69). Duration of AF, prevalence of abnormal left ventricular function, left atrial size, and mitral regurgitation were similar in both groups. CONCLUSIONS: Left atrial thrombi were identified in more than 40% of patients with acute thromboembolism and newly recognized AF. These data suggest that a major source of recurrent thromboembolism in this group may be residual thrombus migration. Among patients with AF and atrial thrombi, clinical thromboembolism seems to occur randomly, or is related to an unidentified process.
Acute Disease↗