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Biomedical subjects

Kirk T Spencer

Publications and source records attributed to Kirk T Spencer.

At least 19 recordsLinked to original sources
PubMed2006

Color encoding of endocardial motion improves the interpretation of contrast-enhanced echocardiographic stress tests by less-experienced readers.

BACKGROUND: We hypothesized that color encoding of endocardial motion could aid less-experienced readers in detection of wall-motion abnormalities at rest and stress in patients with poor acoustic windows. METHODS: Color-encoded images (color kinesis) were obtained at rest and peak dobutamine stress in 4 standard views during intravenous infusion of contrast agent in 117 patients with poorly visualized endocardium. In 101 of 117 patients (86%), in whom contrast enhancement allowed endocardial tracking, images were reviewed by two expert readers without color overlays. Each reader graded regional wall motion as normal, abnormal, or uninterpretable, and their consensus grades served as a gold standard. The same images were then reviewed and graded with and without color overlays by 3 cardiology fellows. The accuracy of the interpretation was calculated against the gold standard separately for the 3 vascular territories (left anterior descending, left circumflex, and right coronary arteries) and averaged for the 3 fellows. RESULTS: With the addition of color encoding: (1) the number of uninterpretable segments decreased by 55% at rest and 61% at peak stress; and (2) all 3 fellows reached higher levels of accuracy in all 3 vascular territories both at rest (6%-82% average) and at stress (73%-80%). CONCLUSION: The addition of color encoding of wall motion to contrast-enhanced images obtained in patients with poor acoustic windows during stress tests improves the interpretation of regional left ventricular function by less-experienced readers.

Dobutamine↗
PubMed2006

Computerized evaluation of echocardiographic stress tests in patients with poorly visualized endocardium using analysis of color-encoded contrast-enhanced images.

AIMS: We hypothesized that real-time color encoding of contrast-enhanced images would allow objective detection of stress-induced wall motion abnormalities (WMA). METHODS: We studied 117 patients with poorly visualized endocardium undergoing dobutamine stress tests. Color-encoded images (Philips, color kinesis) were obtained at rest and peak stress in four standard views during i.v. infusion of Definity. Images were reviewed without color overlays by two expert readers, who graded regional wall motion as normal or abnormal. In 101/117 patients (86%), in whom contrast enhancement allowed endocardial tracking, regional fractional area changes were calculated from the color overlays, and thresholds for calling a stress-induced WMA were optimized in a randomly selected subgroup of 34 patients (ROC analysis) to achieve maximum agreement with expert grades. This computerized detection of stress-induced WMA was then tested prospectively in the remaining 67 patients, using the expert grades as a "gold standard". RESULTS: 20/67 patients had resting WMA and 13/67 patients developed WMA at peak stress. The automated technique detected stress-induced WMA in at least one vascular territory with a sensitivity, specificity and accuracy of 0.80, 0.65 and 0.69, while the level of agreement between the two experts was 0.62, 0.91 and 0.85, respectively. CONCLUSION: Analysis of color-encoded, contrast-enhanced images allows objective, accurate, automated detection of stress-induced WMA in patients with poor acoustic windows.

Cardiotonic Agents↗
PubMed2005

Automated border detection on contrast enhanced echocardiographic images.

BACKGROUND: Accurate determination of left ventricular ejection fraction (LV EF) is of paramount importance in the evaluation of patients with cardiovascular disease. Quantitative techniques for the automated calculation of EF exist however, the robustness of these techniques is dependent on adequate endocardial border definition and therefore are difficult to use in patients with limited images. We sought to combine the endocardial border enhancing effects of contrast echocardiography with an automated border detection technique to provide quantitative and accurate determination of LV EF. METHODS: Thirty-nine consecutive patients referred to nuclear cardiology for EF determination underwent radionuclide angiography followed by echocardiographic imaging using prototype software that allowed automated border detection during contrast infusion. RESULTS: Adequate LV cavity opacification with contrast was possible in 38/39 patients. The mean radionuclide EF was 50+/-16% (range 19-73). There was no statistically significant difference between the mean nuclear EF and averaged echocardiographically determined EF (51+/-18%). The mean bias was 0.6 with limits of agreement that were +15 and -14. CONCLUSION: This study demonstrated that prototype software successfully tracked the contrast enhanced endocardial border allowing accurate calculation of LV EF.

Adult↗
PubMed2005

Effectiveness of echocardiographic imaging by nurses to identify left ventricular systolic dysfunction in high-risk patients.

Recognizing left ventricular (LV) systolic dysfunction is critical. The investigators sought to evaluate whether nurses could be trained to use a hand-carried ultrasound (HCU) device to screen for LV systolic dysfunction in high-risk patients. Sixty-three patients from an outpatient diabetes clinic underwent brief echocardiographic examinations by nurses using HCU devices. Of the 63 patients enrolled in the study, 3 (4.7%) had LV systolic dysfunction. The nurses correctly identified these 3 patients as having LV systolic dysfunction (sensitivity 100%, negative predictive value 100%). The identification of occult LV systolic dysfunction in diabetic patients may allow the initiation of therapies known to improve prognosis.

Ambulatory Care↗
PubMed2005

Use of hand-carried ultrasound devices to augment the accuracy of medical student bedside cardiac diagnoses.

BACKGROUND: Hand-carried ultrasound (HCU) devices used by cardiologists as extensions of the physical examination have been shown to improve the accuracy of bedside diagnoses. We tested the feasibility of teaching medical students to use HCU devices to make bedside cardiac diagnoses and compared the accuracy of their HCU and physical examinations. METHODS: In all, 10 fourth-year medical students enrolled in a 4-week medical school course on the cardiac examination. Students examined 12 standardized patients at 3 different time intervals: (1) on day 1 of the course; (2) on day 10 after review of cardiac physical examination using traditional teaching methods; and (3) after instruction on the use of HCU devices. Students were scored at each time interval for primary findings (most salient) and all findings, accounting for both errors of commission and omission. Scores could range from +12 to -12 for primary findings and from +22 to -22 for all findings. A perfect score was +12 for primary findings and +22 for all findings. RESULTS: The average score for all students at baseline was -3.2 +/- 3.1 and -5.7 +/- 4.8 for primary and all findings, respectively. A significant improvement in the scores was noted with use of the HCU device (2.6 +/- 3.1 and 5.2 +/- 6.6 for primary and all findings, respectively) compared with the baseline and two subsequent physical examinations. CONCLUSION: Instruction of fourth-year medical students on the use of HCU device is feasible and results in significantly more accurate bedside diagnoses.

Analysis of Variance↗
PubMed2005

Clinical features of complications from transesophageal echocardiography: a single-center case series of 10,000 consecutive examinations.

BACKGROUND: Transesophageal echocardiography (TEE) is an essential diagnostic tool that has gained widespread use in clinical cardiology. It is considered reasonably noninvasive and safe; however, insertion and operation of the TEE probe may cause hypopharyngeal, esophageal, or gastric trauma. The current study reports a single-center experience of esophagogastric trauma in 10,000 consecutive TEE examinations. METHODS: TEE examinations were performed by 9 attending physicians who were trained in endoscopic procedures and had been performing TEE studies for at least 1 year. RESULTS: One case of hypopharyngeal perforation (0.01%), 2 cases of cervical esophageal perforation (0.02%), and no cases of gastric perforation (0%) occurred after TEE examination. No fatalities (0%) occurred. We describe the clinical characteristics of individuals who experienced esophageal perforation during this 10-year period. CONCLUSIONS: This single-center study demonstrates that TEE examinations are associated with a very low risk of esophagogastric trauma when performed in a safe setting by experienced operators.

Echocardiography, Transesophageal↗
PubMed2004

Differential diagnosis of cardiac masses using contrast echocardiographic perfusion imaging.

OBJECTIVES: We investigated the usefulness of echocardiographic contrast perfusion imaging in differentiating cardiac masses. BACKGROUND: Two-dimensional echocardiography is the primary diagnostic modality for cardiac masses. However, differentiation between the different types of cardiac masses may be difficult at times. We hypothesized that echocardiographic contrast perfusion imaging would differentiate the neo-vascularization of malignancies from the avascularity of thrombi and the sparse vascularity of stromal tumors. METHODS: Sixteen patients with cardiac masses underwent power-modulation imaging after echocardiographic intravenous contrast administration. Pixel intensities in the mass and an adjacent section of myocardium were analyzed visually and by dedicated software. All masses had a pathologic diagnosis or resolved after anticoagulation. In a subset of patients, video-intensity curves of contrast replenishment in the mass and myocardium over time were generated. The post-impulse steady-state pixel intensity (A) and initial rate of contrast replenishment after impulse (beta) were compared with an index of blood vessel area on pathology. RESULTS: In seven of 16 patients, contrast enhancement resulted in greater pixel intensity in the mass than in the adjacent myocardium. All of these masses were classified pathologically as malignant (n = 6) or benign and vascular (n = 1). Nine masses demonstrated decreased pixel intensity, compared with the myocardium, and were diagnosed pathologically as myxomas (n = 2) or thrombi (n = 5), or they resolved with anticoagulation (n = 2). For the subset of patients, beta correlated with the vessel area index (r = 0.60). CONCLUSIONS: Echocardiographic contrast perfusion imaging aids in the differentiation of cardiac masses. Compared with the adjacent myocardium, malignant and vascular tumors hyper-enhanced, whereas stromal tumors and thrombi hypo-enhanced.

Adult↗
PubMed2004

Harmonic imaging for endocardial visualization and myocardial contrast echocardiography during transesophageal echocardiography.

BACKGROUND: Although harmonic imaging (HI) improves endocardial visualization and is necessary for myocardial perfusion imaging, it has yet to be implemented in transesophageal echocardiography. Our goal was to determine whether HI implemented in a prototype transesophageal echocardiography probe improved endocardial visualization and allowed perfusion imaging. METHODS: In 23 patients, fundamental and harmonic images were obtained in the transgastric short-axis (TSAX) and midesophageal 4-chamber views, and reviewed for endocardial visualization by 3 readers blinded to imaging mode. In 14 additional patients, perfusion imaging was performed in the TSAX view during contrast infusion. RESULTS: HI improved overall endocardial visualization, most noticeably in the anterior and lateral segments (P <.004) in the TSAX view, and in the lateral segments (P <.01) in the midesophageal 4-chamber view. The salvage rate was 8.3% in the TSAX view and 12.6% in the midesophageal 4-chamber view. Myocardial perfusion was consistently confirmed in the inferior (86%), posterior (100%), and lateral (79%) segments, but rarely in the septal (21%), anteroseptal (0%), and anterior (14%) segments. CONCLUSION: Use of HI with transesophageal echocardiography improves endorcardial visualization and allows partial assessment of myocardial perfusion.

Coronary Circulation↗
PubMed2004

Age dependency of the Tei index of myocardial performance.

Despite its clinical use as a sensitive measure of left ventricular performance, little is known about whether the Tei index is influenced by aging. We determined the Tei index in 141 subjects without cardiovascular disease (age 16-78 years). There were statistically significant variations in ejection time, isovolumic relaxation time, and the Tei index with aging. There was a moderate linear correlation between isovolumic relaxation time and age (r = 0.49, P <.001) and the Tei index and age (r = 0.33, P <.001). This investigation demonstrated that when assessing myocardial performance in patients using this index, age-normalized values should be used.

Adolescent↗
PubMed2004

Hand-carried cardiac ultrasound as a tool to screen for important cardiovascular disease in an underserved minority health care clinic.

The disparity in cardiovascular outcomes among racial and social strata may be, in part, because of delayed detection of cardiovascular disease in minority patients. The low cost and portability of hand-carried cardiac ultrasound devices may make screening of underserved patients for cardiac disease feasible. A general internist evaluated 153 patients at a clinic serving an underserved population with a hand-carried cardiac ultrasound device. A total of 27 cases of significant valvular heart disease or ventricular dysfunction were detected in 19 patients (12.4%). Detection of a major cardiac abnormality could not be predicted by cardiac risk factors, age, or chief symptom, whereas patients presenting for new or acute clinic visits were more likely to have an abnormality. The low cost and portability of hand-carried cardiac ultrasound devices may make them important tools for the early detection of cardiovascular disease in minority and underserved populations and, thereby, help to reduce disparities in cardiovascular outcomes.

Cardiovascular Diseases↗
PubMed2004

Automated quantitative assessment of wall motion in patients with poor acoustic windows.

BACKGROUND: No technique exists for objective evaluation of left ventricular wall motion in contrast-enhanced images. We tested a new technique for quantification of regional fractional area change using contrast-enhanced power modulation imaging with color kinesis. METHODS: The feasibility of this technique for detecting acute ischemia was first tested in 11 pigs. Next, the accuracy for detecting resting wall-motion abnormalities was determined in 52 patients requiring contrast and compared with conventional interpretation of 2-dimensional images by inexperienced readers. Expert interpretation of 2-dimensional images served as the gold standard. RESULTS: In pigs, coronary occlusion resulted in reversible hypokinesis and reduced regional fractional area change. In patients with poor acoustic windows, this technique's accuracy for quantitative detection of resting wall-motion abnormalities was 86% compared with 81% for conventional interpretation by inexperienced readers (P <.01). CONCLUSIONS: Regional wall motion can be accurately assessed using color-encoded power modulation imaging for patients requiring contrast. This technique may prove a useful diagnostic aid to echocardiographers of varying levels of experience.

Animals↗
PubMed2003

Unsuspected clinically important findings detected with a small portable ultrasound device in patients admitted to a general medicine service.

OBJECTIVE: We sought to determine whether physicians with training in echocardiography could successfully use a small echocardiographic device to detect occult cardiovascular disease in patients admitted to a general medical service. METHODS: In all, 103 consecutive patients had a physician-performed bedside echocardiographic examination with a small portable ultrasound device. RESULTS: Of patients, 70% did not have a clinical indication for echocardiography and of these patients, 39% had an abnormal study with the portable ultrasound device. There was a high rate of false-positive examinations, but approximately 17% of patients without a clinical indication for echocardiography had an important cardiac abnormality detected, including 10% with unsuspected left ventricular systolic dysfunction. CONCLUSIONS: Many patients on a general medical hospital ward have unsuspected, clinically important cardiac findings such as left ventricular dysfunction that can be screened for by physicians with training in echocardiography using small portable ultrasound devices.

Academic Medical Centers↗