Consistency of echocardiographic ejection fraction: variation and 'drift' by interpreter and practice site.

AIMS: Visual analysis of ejection fraction by echocardiography (echo) is commonly performed, but little data exists regarding consistency among interpreters. We postulate that an active echo group evolves a standard to which interpreters cluster, with variation or 'drift' occurring at satellite sites distant from the main practice centre. Assuming that echo ejection fraction follows a normal distribution, average ejection fraction for high volume readers should be similar. METHODS AND RESULTS: From May 1997 to June 1999, 8187 echoes were read by 16 (average 512) readers of a single practice at several sites. Composite and individual ejection fraction (visual estimate) means and standard deviations were compared. Composite ejection fraction was 54.17+/-11.35. Mean ejection fraction varied significantly overall among readers (P<0.0001) with 37 comparisons between individual readers being significantly different (P<0.05). However, analysis suggested that these individual differences involved only five readers, four of whom practised at satellite sites. If these five readers were excluded, no significant individual differences were seen (n=6202). If only the four satellite readers were excluded, just four significant individual differences were seen (n=6915). CONCLUSIONS: (1) Within a busy single practice site, mean echo ejection fraction is very similar, suggesting a self-evolved practice standard that is consistently adhered to. (2) 'Drift' or variability is seen at smaller satellite sites, perhaps due to less exposure to the echo interpretations of others. (3) This type of analysis may provide a useful quality assurance tool for echo laboratories.

Guidelines for cardiac sonographer education: recommendations of the American Society of Echocardiography Sonographer Training and Education Committee.

In 1992, the American Society of Echocardiography published a report of the Sonographer Education and Training Committee's recommendations for education of sonographers who perform echocardiographic procedures. Since the publication of the original document, there has been continual progress in technology with the development of more sophisticated diagnostic applications that allow more information to be obtained from echocardiographic procedures. These recent changes in the clinical application of echocardiography should be included in all cardiac sonographer education programs. The American Society of Echocardiography, a professional society that currently represents approximately 2500 cardiac sonographers, provides these updated guidelines.

Digital echocardiography: its role in modern medical practice.

Digital echocardiography has evolved rapidly during the last decade, and the all-digital echocardiographic laboratory has just reached the threshold of reality. This review article explains what this transition means for the modern medical practice and concisely presents what a digital echocardiogram is, the technical aspects of digital image acquisition and processing, and the advantages and limitations of digital echocardiography vs analog echocardiography. This review should serve as a useful source of information for the general cardiologist not working closely with digital echocardiography, as well as a resource for the noncardiologist.

Transition to an all-digital echocardiography laboratory: a large, multi-site private cardiology practice experience.

Acquisition, interpretation, and storage of digital echocardiographic images has many advantages over the standard videotape-based method. Archival, transmission, and comparative interpretation are all optimized with digital echocardiography. A study performed at one site can be immediately available for viewing and analysis at another site by means of standard data transfer technology. Echocardiograms can be interpreted in the context of prior studies, which are readily available for side-by-side comparison. The transition to an all-digital laboratory involves the commitment of persons at multiple levels in the cardiology practice, including administrators, information technology specialists, sonographers, and physicians. Quality of patient care, use of physicians' and sonographers' time, and long-term financial benefit are all areas where improvement may be realized with the use of digital echocardiography. We present our experience in the development of an all-digital echocardiography laboratory, and we conclude that digital echo-cardiography is practical and can be implemented readily in a clinical setting. We performed several correlative analyses during this transition to validate the consistency and accuracy of digital interpretation compared with those of analog methods. The transition process from analog (videotape) to digital, including full wide area network exchange, took approximately 8 months. As technology advances, issues surrounding storage, comparison, and acquisition formats will continue to develop. We hope that our experience will help others make the transition to the digital environment and benefit from the ease of image access, the ability to comparatively interpret echocardiograms, and the superior image quality afforded by this advancement.

Noninvasive assessment of the direct action of oral nifedipine and nicardipine on left ventricular contractile state in patients with systemic hypertension: importance of reflex sympathetic responses.

OBJECTIVES: This study was designed to noninvasively assess the direct action of calcium channel blockers on left ventricular contractility in humans and to establish a framework for determining the importance of reflex sympathetic responses to any pharmacologic intervention. BACKGROUND: Assessment of left ventricular contractility in patients taking calcium channel blockers by using traditional indexes of systolic performance is difficult because of the after-load-reducing and reflex sympathetic effects of the drugs. METHODS: Fifteen hypertensive patients (mean blood pressure 127 +/- 15 mm Hg) were studied with Doppler echocardiography and calibrated subclavian pulse tracings while receiving placebo and 1 week after randomization to treatment with oral nifedipine (20 mg three times daily; n = 7) or nicardipine (30 mg three times daily; n = 8). Left ventricular circumferential end-systolic wall stress versus rate-corrected velocity of shortening (Vcfc) relations were generated over a range of loads using nitroprusside. Data were acquired before and during esmolol infusion, thereby allowing assessment of hemodynamic responses with the sympathetic nervous system functionally intact as well as ablated. The adequacy of sympathetic blockade was confirmed with isoproterenol challenges. In each case, left ventricular contractile state was measured relative to placebo and esmolol data as delta Vcfc at a common end-systolic wall stress. Increased and decreased contractility were defined as delta Vcfc > 0 and delta Vcfc < 0, respectively. RESULTS: Nifedipine and nicardipine equally decreased blood pressure and end-systolic wall stress and increased left ventricular percent fractional shortening and stroke volume. Neither drug alone consistently altered ventricular contractility compared with placebo. Ablation of reflex sympathetic tone with esmolol unmasked a negative inotropic effect for nifedipine (p = 0.03 vs. esmolol alone) but not nicardipine (p = 0.68 vs. esmolol alone). The difference between the contractility effects of nifedipine plus esmolol versus those of nicardipine plus esmolol approached statistical significance (p = 0.07). CONCLUSIONS: Totally noninvasive techniques showed a differential effect on left ventricular contractility between nifedipine and nicardipine when alterations in afterload and reflex sympathetic responses were eliminated as confounding variables. This diagnostic approach, based on the use of pharmacologic probes, should have wide applicability for assessing the direct inotropic effect of any agent, even in the presence of complex primary and secondary physiologic modes of action.

Influence of histamine receptors on basal left ventricular contractile tone in humans: assessment using the H2 receptor antagonist famotidine and the beta-adrenoceptor antagonist esmolol as pharmacologic probes.

Histamine has a positive inotropic action in humans. Recent controversial data have suggested that histamine2 (H2) receptor blockade depresses overall left ventricular systolic performance in healthy volunteers. To explore the possibility that H2 receptors positively influence basal left ventricular contractile tone, 10 normal subjects were studied by using imaging and Doppler echocardiography and calibrated subclavian pulse data in a blinded, randomized, two-period crossover trial with measurements obtained at the end of each 7-day period. Oral drug administration consisted of either the potent H2 antagonist famotidine (40 mg/day) or placebo. Left ventricular circumferential end-systolic wall stress-rate-corrected velocity of fiber shortening (Vcfc) relations were generated over a range of loads with methoxamine. Contractility was assessed by using Vcfc at a common end-systolic wall stress. During each study, data were obtained before and during high dose intravenous esmolol administration to determine the contributions, if any, of sympathetic reflex responses. Famotidine did not alter blood pressure, left ventricular percent fractional shortening, circumferential end-systolic wall stress, stroke volume index, cardiac index, total vascular resistance or ventricular contractile state in comparison with placebo but did decrease heart rate by 3 beats/min (p less than 0.05). With beta-adrenergic blockade, no differences in contractility were evident between esmolol alone and famotidine plus esmolol. Thus, H2 receptor blockade with famotidine does not alter myocardial mechanics or cardiac sympathetic tone, suggesting that in humans basal left ventricular contractile state is not physiologically dependent on the H2-mediated effects of histamine.

Synthesis of 2-deoxy-D-arabino-(6-13C)hexose.

2-Deoxy-D-arabino-[6-13C]hexose (10), to be used to test the stability of 2-deoxy-D-arabino-hexose 6-phosphate in brain tissue, was prepared. 2-Deoxy-D-arabino-hexose was labeled at C-6 because of the large difference in chemical shift between C-6 in the free sugar and C-6 in the 6-phosphate. The synthetic scheme resembled that used for the synthesis of D-[6-13C]glucose that involved the removal of C-6 from D-glucose followed by its replacement with 13C. The protected derivative methyl 2-deoxy-alpha-D-arabino-hexofuranoside was prepared, using trifluoroacetic acid in methanol. This was treated with periodate, which cleaves only between C-5 and C-6, to afford an aldehyde which reacted directly with K13CN to give a mixture of the D-arabino and L-xylo nitriles. The enriched nitriles were reduced with hydrogen in the presence of 5% Pd-carbon catalyst to a mixture of 6-aldehydo sugars. These were reduced with NaBH4 to a mixture of the two labeled methyl furanosides. Acid hydrolysis followed by ion-exchange chromatography on AG-50(Ca2+) resin at 65 degrees gave 10 in an overall yield of 16% from K13CN.