Lateral annular systolic excursion ratio: A novel measurement of right ventricular systolic function by two-dimensional echocardiography.

Introduction: Accurate assessment of right ventricular (RV) systolic function has prognostic and therapeutic implications in many disease states. Echocardiography remains the most frequently deployed imaging modality for this purpose, but estimation of RV systolic function remains challenging. The purpose of this study was to evaluate the diagnostic performance of a novel measurement of RV systolic function called lateral annular systolic excursion ratio (LASER), which is the fractional shortening of the lateral tricuspid annulus to apex distance, compared to right ventricular ejection fraction (RVEF) derived by cardiac magnetic resonance imaging (CMR). Methods: A retrospective cohort of 78 consecutive patients who underwent clinically indicated CMR and transthoracic echocardiography within 30 days were identified from a database. Parameters of RV function measured included: tricuspid annular plane systolic excursion (TAPSE) by M-mode, tissue Doppler S', fractional area change (FAC) and LASER. These measurements were compared to RVEF derived by CMR using Pearson's correlation coefficients and receiver operating characteristic curves. Results: LASER was measurable in 75 (96%) of patients within the cohort. Right ventricular systolic dysfunction, by CMR measurement, was present in 37% (n = 29) of the population. LASER has moderate positive correlation with RVEF (r = 0.54) which was similar to FAC (r = 0.56), S' (r = 0.49) and TAPSE (r = 0.37). Receiver operating characteristic curves demonstrated that LASER (AUC = 0.865) outperformed fractional area change (AUC = 0.767), tissue Doppler S' (AUC = 0.744) and TAPSE (AUC = 0.645). A cohort derived dichotomous cutoff of 0.2 for LASER was shown to provide optimal diagnostic characteristics (sensitivity of 75%, specificity of 87% and accuracy of 83%) for identifying abnormal RV function. LASER had the highest sensitivity, accuracy, positive and negative predictive values among the parameters studied in the cohort. Conclusions: Within the study cohort, LASER was shown to have moderate positive correlation with RVEF derived by CMR and more favorable diagnostic performance for detecting RV systolic dysfunction compared to conventional echocardiographic parameters while being simple to obtain and less dependent on image quality than FAC and emerging techniques.

Evaluation of echocardiographic derived parameters for right ventricular size and function using cardiac magnetic resonance imaging.

BACKGROUND: Cardiac Magnetic Resonance Imaging (cMRI) is the gold standard for right ventricular (RV) assessment due to its high spatial resolution. The American Society of Echocardiography (ASE) recommends eight structural and six functional quantitative parameters for evaluation of the RV. This study sought to simplify echocardiographic RV assessment by examining the relative diagnostic value of the echo recommended parameters by applying them to cMRI imaging of the RV. METHODS: We applied ASE recommended measures of RV size and function to 56 cMRI's and compared them to RV volumetric analysis obtained from cMRI. Pearsons' correlation coefficient was used to compare ASE prescribed parameters to corresponding cMRI calculated RV end diastolic volume (RVEDV) and RV ejection fraction (RVEF). The diagnostic performance of each parameter in predicting abnormal RV size or function was analyzed using receiver operator characteristic curves. Youden-J index was used to determine optimal sensitivity/specificity cut-points. Stepwise regression modeling was performed to identify measurements independently associated with RV size or RVEF. RESULTS: RV end diastolic area (RVEDA) correlated best with RVEDV (r = .76, p < 0.001) and RV fractional area change (RVFAC) correlated best with RVEF (r = .7, p < 0.001). The best ASE parameter for identifying RV dilatation was RVEDA (Youden-J index = .84), the optimal cutoff was 32.3 cm2 which yielded sensitivity/specificity of 84% and 100%, respectively. The best parameter for diagnosing RV dysfunction was RVFAC (Youden-J index = .52), with an optimal cutoff of 42% leading to sensitivity/specificity of 64% and 88%, respectively. CONCLUSION: The area based echocardiographic parameters for RV size and function, RVEDA and RV fractional area change outperform linear measurements in predicting RV dilation and RV systolic dysfunction. These parameters should be examined in further echocardiographic based studies as the primary parameters to guide quantitative RV assessment.

Relation of Venous Thromboembolism Risk to Ischemic Stroke Risk in Hospitalized Patients with Cancer.

Patients with cancer are at increased risk for venous thromboembolism (VTE). However, the relationship of cancer type to the risk of arterial thrombosis in patients with high VTE risk has not been described. The goal of this study is to determine the rate of arterial thrombosis in patients with different types of solid tumors stratified by VTE risk. Using the 2012 National Inpatient Sample, we identified 373,789 hospitalizations involving patients ≥18 years associated with solid tumors, stratified by type. Data were collected on clinical characteristics, VTE (deep vein thrombosis [DVT] and pulmonary embolism [PE]), and arterial thrombosis (primary diagnosis of myocardial infarction [MI] and ischemic stroke). Subjects with solid tumors (stages I to IV) were stratified by VTE risk - high versus low. Certain solid tumor types (esophageal, lung, melanoma, ovarian, pancreatic, stomach, and uterine) were found to be associated with a higher rate of VTE compared with other cancer types (6.8% vs 3.9%, p < 0.001). Multivariate analysis applied to the high VTE risk group showed no increased risk for MI (odds ratio [OR] 0.93, p = 0.74), however, the rate of ischemic stroke was increased (OR 1.22, p < 0.001). Those in the high VTE risk group who had metastatic disease were at higher risk for arterial thrombosis (MI OR 1.35, p < 0.001, ischemic stroke OR 2.43, p < 0.001). In conclusion, different cancer types are associated with increased risk of both venous and arterial thrombosis and the risk is further increased by the presence of metastatic disease.

The association of QRS duration with atrial fibrillation in a heart failure with preserved ejection fraction population: a pilot study.

BACKGROUND: Heart failure is a significant cause of morbidity and mortality, yet patient risk stratification may be difficult. Prevention or treatment of atrial fibrillation (AF) may be an important strategy in these patients that could positively affect their outcome. It has been demonstrated that in patients with systolic dysfunction, prolonged QRS duration (QRSd), an easily measured electrocardiographic parameter, is associated with AF. HYPOTHESIS: Prolonged QRSd is associated with an increase in prevalence of AF in patients with heart failure with preserved ejection fraction(HFPEF). METHODS: Between February 2006 and February 2009, 718 patients were discharged with a diagnosis of HF from the Dartmouth-Hitchcock Medical Center. Of these, 206 had EF ≥50% by echocardiography performed within 72 hours of admission. After exclusions, 82 patients remained, of which 25 had AF and 57 had sinus rhythm. Characteristics of the AF and sinus-rhythm patients were compared in this pilot study. RESULTS: After adjustment for age, prior diagnosis of HF, and left atrial area, there was a nonsignificant trend (odds ratio: 2.2, 95% CI of 0.3-17.2) for a QRSd >120 ms to be associated with AF. CONCLUSIONS: Similar to results in patients with systolic dysfunction, patients with preserved EF may have an association between a prolonged QRSd and AF.

Tricuspid Regurgitation Following Implantation of Endocardial Leads: Incidence and Predictors.

BACKGROUND: Endocardial leads, permanent pacemaker (PPM), or implantable cardioverter defibrillator (ICD) placed across the tricuspid valve can lead to tricuspid regurgitation (TR). The reported incidence of this complication has varied widely. There are limited data predicting which patients will develop this complication. This study sought to describe the incidence of worsening TR post-PPM or ICD and to identify patient-specific predictors of increased TR following lead placement. METHODS: Patients (N = 382) who received a PPM or ICD from January 1, 2006 to December 31, 2010 and had echocardiograms both within 365 days prior to and up to 1,200 days after device placement were studied. TR was assessed on a 6-point scale (none/trace, mild, mild to moderate, moderate, moderate to severe, severe). Primary outcome was a two-grade increase in the severity of TR. Echocardiographic and clinical predictors of worsening TR were examined using multivariate regression. RESULTS: A two-grade increase in TR occurred in 10.0% of our patient population. Age, lead position, atrial fibrillation, right atrial (RA) area, right ventricular systolic pressure (RVSP), left atrial area, and severity of mitral regurgitation were univariate predictors of worsening TR post lead placement. In the multivariate analysis, predevice RA area and RVSP were associated with increased TR after endocardial lead placement. Percentage of time spent pacing did not appear to be associated with increased TR. CONCLUSION: The incidence of increased TR postendocardial lead placement was 10.0%; this is lower than prior estimates. Predevice RA area and RVSP are predictors of increased TR after lead placement.

Quantification of the variability associated with repeat measurements of left ventricular two-dimensional global longitudinal strain in a real-world setting.

BACKGROUND: Global longitudinal strain (GLS) derived from two-dimensional speckle-tracking is an emerging technology, but lack of industry standards limits its application. Prior studies support using this tool to identify subclinical disease through serial changes, but the variability introduced by a change in vendor or reader is not well defined. METHODS: Fifty study subjects were prospectively identified to include four subgroups to ensure a broad range of GLS: normal (n = 20), left ventricular hypertrophy (n = 10), ST-segment elevation myocardial infarction (n = 10), and systolic heart failure (n = 10). Raw data were obtained using equipment from two vendors during the same session, and GLS was analyzed using an offline workstation. Intraobserver and interobserver variation was measured using correlation coefficients, intraclass correlation coefficients, and Bland-Altman plots. RESULTS: GLS measurements were highly reproducible by the same reader or a different reader using vendor 1 and vendor 2 or comparing vendors (correlation coefficients and intraclass correlation coefficients ≥ 0.95). However, the Bland-Altman plots suggested that the variation in repeat GLS measurements may range from ± 2% to ± 5% on the basis of a change in vendor, reader, or both. CONCLUSIONS: The expected variation in GLS measurements associated with a change in vendor, reader, or both should be considered when making conclusions about significant changes in serial measurements.

Regional patterns of dyssynchrony: lateral wall delay is desirable but not essential for left ventricular remodeling in biventricular pacing.

BACKGROUND: Tissue synchronization imaging (TSI), a parametric imaging technique based on tissue velocity imaging, often demonstrates patterns other than lateral delay in patients evaluated for cardiac resynchronization therapy (CRT). The prevalence of these patterns and their response to CRT has not been well described. We hypothesized that regional patterns of dyssynchrony might correlate with the extent of reverse remodeling. METHODS: A consecutive series of 32 patients underwent echocardiographic study prior to CRT implant and 3 months postimplant. TSI was used to color-code the time-to-peak positive systolic velocity at six basal and six mid-LV segments. Each patient was assigned to one of four groups based on the predominant location of greatest delay (≥ 2 segments): (1) posterolateral delay, (2) septal delay, (3) no dyssynchrony, or (4) other. RESULTS: Patients were classified as follows: posterolateral delay in 44% of patients (n = 14), septal delay in 28% (n = 9), no dyssynchrony in 16% (n = 5), and other pattern in 13% (n = 4). At 3-month follow-up, the group with the lateral delay pattern was associated with the greatest decrease in left ventricular end-systolic volume (LVESV) and the largest improvement in left ventricular ejection fraction (LVEF) (-45 mL and +9.3%, respectively, P < 0.05). The LVESV in the other three groups changed as follows: -24 mL (septal), -28 mL (no dyssynchrony), and -15 mL (other). Similar trends were observed for LVEF and left ventricular end-diastolic volume. CONCLUSIONS: Despite the presence of wide QRS and a left bundle branch block, the most delayed segment is not always the posterolateral wall. Posterolateral delay is associated with the best response to CRT, while other patterns respond at a lower magnitude.

Predictors of rapid aortic dilatation in adults with a bicuspid aortic valve.

BACKGROUND AND AIM OF THE STUDY: The role of atherosclerosis and atherosclerotic risk factors in predicting progressive aortic dilatation in patients with bicuspid aortic valve (BAV) is not well defined. The study aim was to assess the role of these risk factors in progressive aortic dilatation in patients with this condition. METHODS: Adult patients were identified with BAV who displayed rapid aortic dilatation, and the association of the condition with hemodynamic and atherosclerotic risk factors was assessed. By using the Dartmouth-Hitchcock and Hartford Hospital echocardiographic databases between 1997 and 2009, a total of 135 patients with BAV and serial echocardiograms recorded at least one year apart were allocated to groups of rapid progressors (RP; n = 53) or slow progressors (SP; n = 82). Rapid aortic progression was defined as an annual rate of progression > or = 75th percentile at the sinus of Valsalva or ascending aorta level. Univariate atherosclerotic and hemodynamic variables that correlated with rapid aortic dilatation were analyzed, and independent predictors of rapid aortic dilatation identified. RESULTS: The RP group had higher mean random blood glucose levels, greater coronary artery disease, more tobacco use, and a higher National Heart, Lung and Blood Institute 10-year risk of developing coronary heart disease (10-year risk). An elevated 10-year risk of > 7% (OR 4.5; 95% CI 1.92-10.73), tobacco use (OR 5.05; 95% CI 1.51-16.86) and higher random blood glucose level (OR 1.01; 95% CI 1.002-1.03) were independent predictors of rapid aortic dilatation. CONCLUSION: In adults with BAV and non-dilated aortas at baseline, an elevated 10-year risk, tobacco use and hyperglycemia may serve as predictors of rapid aortic dilatation.

A call to action: variability in guidelines for cardiac evaluation before renal transplantation.

BACKGROUND AND OBJECTIVES: Candidates for renal transplantation are at increased risk for complications related to cardiovascular disease; however, the optimal strategy to reduce this risk is not clear. The aim of this study was to evaluate the variability among existing guidelines for preoperative cardiac evaluation of renal transplant candidates. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: A consecutive series of renal transplant candidates (n=204) were identified, and four prominent preoperative cardiac evaluation guidelines, pertaining to this population, were retrospectively applied to determine the rate at which each guideline recommended cardiac stress testing. RESULTS: The rate of pretransplant cardiac stress testing would have ranged from 20 to 100% depending on which guideline was applied. The American Heart Association/American College of Cardiology (ACC/AHA) guideline resulted in the lowest rate of testing (20%). In our population, 178 study subjects underwent stress testing: 17 were found to have ischemia and 10 underwent revascularization. The ACC/AHA approach would have decreased the number of noninvasive tests from 178 to 39; it would have identified only 4 of the 10 patients who underwent revascularization. The three other guidelines (renal transplant-specific guidelines) recommended widespread pretransplant cardiac testing and thus identified nearly all patients who had ischemia on stress testing. CONCLUSIONS: The ACC/AHA perioperative guideline may be inadequate for identifying renal transplant candidates with coronary disease; however, renal transplant-specific guidelines may provoke significant overtesting. An intermediate approach based on risk factors specific to the ESRD population may optimize detection of coronary disease and limit testing.

Defining patient-prosthesis mismatch and its effect on survival in patients with impaired ejection fraction.

BACKGROUND: How best to define patient-prosthesis mismatch (PPM) continues to be debated. Over time, the indexed effective orifice area has become the most widely used method. However, the clinical relevance of PPM remains controversial. METHODS: The indexed geometric orifice area and indexed effective orifice area were calculated for 143 patients having undergone aortic valve replacement with a normal left ventricular function 0.45 or less. Using the indexed geometric orifice area method, PPM was defined as nonsignificant if 1.2 cm(2)/m(2) or greater and as significant if less than 1.2 cm(2)/m(2). Using the indexed effective orifice area method, PPM was considered as nonsignificant if greater than 0.85 cm(2)/m(2), as moderate if greater than 0.65 cm(2)/m(2) and less than or equal to 0.85 cm(2)/m(2), and as severe PPM if 0.65 cm(2)/m(2) or less. RESULTS: The number of patients classified as having PPM differed according to the method used to predict its presence (PPM: Effective orifice area method = 72.7%; geometric method = 19.6%). Regardless of the method used to classify PPM there was no significant effect on mortality (adjusted hazard ratio: 2.65 at 1 year, 0.99 at 5 years, 0.92 at 9 years; p = not significant). The postoperative mean transvalvular gradient (17.1 ± 6.5 mm Hg) and left ventricular function (0.50 ± 0.145) improved significantly compared with the preoperative findings. CONCLUSIONS: The method used to calculate PPM resulted in significant classification discordance. However, regardless of classification, the presence of PPM did not adversely affect long-term outcome.

Two-dimensional longitudinal strain in patients with aortic stenosis can be reliably acquired at the bedside without additional benefit of offline analysis.

BACKGROUND: Two-dimensional strain echocardiography (2DS) has been used to assess ventricular function in several disease states. In previous studies of 2DS, strain analysis was usually performed offline by experienced echocardiographers. The applicability of 2DS in busy clinical labs would be enhanced if 2DS could be reproducibly measured by sonographers at the time of the echo exam. In this study we compared the reproducibility of strain measurements between sonographers at the time of the echo exam with those performed offline by an experienced echocardiographer. METHODS: Apical left ventricular (LV) B-mode images were acquired in 98 consecutive patients being evaluated for aortic stenosis. 2DS analysis was performed at the time of the exam by a sonographer. The same images were analyzed offline by an experienced echocardiographer. Global longitudinal strain (GLS) results were analyzed for interobserver reproducibility. Additionally, the regional longitudinal strain (RLS) of 20 randomly selected patients was analyzed for intraobserver reproducibility. RESULTS: Acceptable data quality was available in 97.8% of the segments measured at the time of the exam and in 96.9% at the workstation. Interobserver reproducibility of the global peak strain was high (r = 0.855, P < 0.001). Additionally, applying cutoffs for separating normal from abnormal GLS revealed good agreement between sonographer and experienced echocardiographer [kappa analysis (κ= 0.739, P < 0.001)]. Overall RLS intraobserver reproducibility was high (raw mean adjusted r = 0.915). CONCLUSION: The GLS in aortic stenosis patients can be reliably measured at the bedside by a sonographer without additional benefit of offline analysis.

Myocardial hypertrophy in the absence of external stimuli is induced by angiogenesis in mice.

Although studies have suggested a role for angiogenesis in determining heart size during conditions demanding enhanced cardiac performance, the role of EC mass in determining the normal organ size is poorly understood. To explore the relationship between cardiac vasculature and normal heart size, we generated a transgenic mouse with a regulatable expression of the secreted angiogenic growth factor PR39 in cardiomyocytes. A significant change in adult mouse EC mass was apparent by 3 weeks following PR39 induction. Heart weight; cardiomyocyte size; vascular density normalization; upregulation of hypertrophy markers including atrial natriuretic factor, beta-MHC, and GATA4; and activation of the Akt and MAP kinase pathways were observed at 6 weeks post-induction. Treatment of PR39-induced mice with the eNOS inhibitor L-NAME in the last 3 weeks of a 6-week stimulation period resulted in a significant suppression of heart growth and a reduction in hypertrophic marker expression. Injection of PR39 or another angiogenic growth factor, VEGF-B, into murine hearts during myocardial infarction led to induction of myocardial hypertrophy and restoration of myocardial function. Thus stimulation of vascular growth in normal adult mouse hearts leads to an increase in cardiac mass.

Selective regulation of arterial branching morphogenesis by synectin.

Branching morphogenesis is a key process in the formation of vascular networks. To date, little is known regarding the molecular events regulating this process. We investigated the involvement of synectin in this process. In zebrafish embryos, synectin knockdown resulted in a hypoplastic dorsal aorta and hypobranched, stunted, and thin intersomitic vessels due to impaired migration and proliferation of angioblasts and arterial endothelial cells while not affecting venous development. Synectin(-/-) mice demonstrated decreased body and organ size, reduced numbers of arteries, and an altered pattern of arterial branching in multiple vascular beds while the venous system remained normal. Murine synectin(-/-) primary arterial, but not venous, endothelial cells showed decreased in vitro tube formation, migration, and proliferation and impaired polarization due to abnormal localization of activated Rac1. We conclude that synectin is involved in selective regulation of arterial, but not venous, growth and branching morphogenesis and that Rac1 plays an important role in this process.

Early mitral filling/diastolic mitral annular velocity ratio is not a reliable predictor of left ventricular filling pressure in the setting of severe mitral regurgitation.

The early mitral filling velocity (E)/early diastolic mitral annular velocity (E') ratio is increasingly being used as a simplified approach to estimate left ventricular (LV) filling pressure. The validity of applying this Doppler parameter to patients with severe mitral regurgitation is unknown. We retrospectively identified 20 patients in sinus rhythm who had LV end-diastolic pressure (LVEDP) invasively measured within 72 hours of a full echocardiogram including diastolic parameters. We observed a poor correlation between E/E' ratio and LVEDP in these patients (r = -0.07, P = not significant). Previously described E/E' cut-off values did not accurately identify patients with low, intermediate, and high LVEDP. Of the diastolic parameters measured, the most significant correlation with LVEDP was found with mitral deceleration time (r = -0.66, P = .002) and systolic/diastolic peak velocity ratio (r = -0.52, P = .02). We conclude that E/E' ratio is not reliable in predicting LV filling pressure in the setting of severe mitral regurgitation, and that in these cases mitral deceleration time or systolic/diastolic peak velocity ratio may be better indicators of LVEDP.

Live 3D echo guidance of catheter-based endomyocardial injection.

Local delivery of therapeutic agents into the myocardium is limited by suboptimal imaging. We evaluated the feasibility and accuracy of live 3D echo to guide left ventricular endomyocardial injection. An intramyocardial injection catheter was positioned in the left ventricle in five healthy Yorkshire pigs using fluoroscopy. All other catheter manipulations were performed with live biplane and 3D echo guidance. In each animal, a total of 12 endomyocardial injections (volume, 50-100 microl) of echo contrast mixed with blue tissue dye were performed. Four injections, 10 mm apart, were directed to three myocardial target zones: the anterior septum at the mitral valve level (zone 1); the posterolateral wall between the heads of the papillary muscles (zone 2); and the apex (zone 3). The injections were aimed to form a transverse line in zones 1 and 2 and an inverted triangular pyramid in zone 3. The animals were sacrificed, the hearts were inspected and the left ventricular endocardium was examined to create a map of injection marks. Success, defined as a visible injection of tissue dye, was 95%, and accuracy, defined as an injection into the target zone, was 83%. There was no significant difference in accuracy between the zones. Live 3D echo can successfully guide endomyocardial injections by accurately targeting specific myocardial zones, verifying catheter apposition and, when combined with echo contrast, providing real-time visualization of injectate deposition.

Stability of ascending aortic dilatation following aortic valve replacement.

BACKGROUND: Replacement of the ascending aorta (Asc Ao) at the time of aortic valve replacement (AVR) is controversial because the risk of progressive dilatation following valve replacement is uncertain. Our aim was to determine the natural history of ascending aortic dilatation following AVR. METHODS AND RESULTS: We studied 185 patients undergoing AVR at our institution between 1992 and 1999. Clinical and echocardiographic data were obtained by merging our institutional echocardiographic database with the DHMC component of the Northern New England Cardiovascular Disease Study Group database. Baseline Asc Ao measurements obtained from intraoperative transesophageal echocardiograms or early (<8 weeks) postoperative transthoracic echocardiograms were compared with late follow-up measurements (mean follow-up 30.0+/-23.4 months). During follow-up, there was no increase in the mean Asc Ao diameter (3.6+/-0.6 cm versus 3.6+/-0.6 cm, p=NS). Progressive aortic dilatation, defined as an increase in diameter >0.3 cm, occurred in 27/185 patients (15%). Baseline Asc Ao dilatation (>or=3.5 cm) was present in 107/185 patients (58%). In this subset of patients, there was no increase in mean Asc Ao diameter (4.0+/-0.4 versus 3.9+/-0.6 cm, p=NS) and progressive aortic dilatation occurred in only 10 patients (9.3%). No patients with baseline aortic dilatation (range, 3.5 to 5.3 cm) dilated beyond 5.5 cm on follow-up (range, 2.4 to 5.5 cm). There were no clinical or valvular characteristics that predicted progressive Asc Ao dilatation. CONCLUSIONS: An increase in Asc Ao dilatation occurs infrequently following AVR and therefore, argues against routine Asc Ao replacement at the time of AVR.

Integrated backscatter during harmonic and fundamental frequency imaging--effect of depth, mechanical index, and tissue anisotropy: implications for myocardial tissue characterization.

OBJECTIVE: To explore the potential advantages of tissue harmonic imaging (THI) versus fundamental frequency imaging (FFI) when applied to tissue characterization. METHODS: A Philips Medical Systems Sonos 5500 echocardiograph equipped with a broadband transducer (S4) and an on-line quantitative analysis software package (Acoustic Densitometry) was used for imaging. The effect of mechanical index (MI), imaging depth, and anisotropy on relative backscatter amplitude was evaluated. RESULTS: This study demonstrated that imaging with tissue harmonics generated relatively greater backscatter values at clinically relevant imaging depths and instrument settings referenced to FFI. This effect was dependent on MI setting. A direct relationship between backscatter amplitude and MI was demonstrated. Additionally, tissue anisotropy had similar effects on integrated backscatter amplitude during both THI and FFI. However, relative backscatter values at each fiber orientation are greater during THI at similar instrument settings when referenced to FFI. CONCLUSION: Tissue harmonic imaging may offer advantages over FFI for myocardial tissue characterization.

Reversible myocardial dysfunction after traumatic brain injury: mechanisms and implications for heart transplantation.

Reversible myocardial dysfunction is known to occur in patients with cerebrovascular accidents and brain death. Several mechanisms for transient myocardial dysfunction have been proposed, including increased sympathetic activity, hormone depletion, and a reduction in coronary perfusion pressure. The relative importance of each of these mechanisms remains controversial. We report the case of a 19-year-old man who suffered traumatic brain death associated with reversible myocardial dysfunction despite elevated cardiac enzymes. Myocardial recovery occurred after correcting his hemodynamic instability and hypothermia emphasizing the importance of normalization of coronary perfusion pressure and core body temperature. The mechanisms for reversible myocardial dysfunction and their implications for heart transplantation following traumatic brain death are reviewed. A diagnostic strategy is proposed that would allow early recognition of reversible myocardial dysfunction in brain-dead patients.