Accurate guidance of a catheter by ultrasound imaging and identification of a catheter tip by pulsed-wave Doppler.

BACKGROUND: With the advent of numerous minimally invasive medical procedures, accurate catheter guidance has become imperative. We introduce and test an approach for catheter guidance by ultrasound imaging and pulsed-wave (PW) Doppler. METHODS: A steerable catheter is fitted with a small piezoelectric crystal at its tip that actively transmits signals driven by a function generator. We call this an active-tip (AT) catheter. In a water tank, we immersed a "target" crystal and a rectangular matrix of four "reference" crystals. Two-dimensional (2D) ultrasound imaging was used for initial guidance and visualization of the catheter shaft, and then PW Doppler mode was used to identify the AT catheter tip and guide it to the simulated target that was also visible in the 2D ultrasound image. Ten guiding trials were performed from random initial positions of the AT catheter, each starting at approximately 8 cm from the target. RESULTS: After the ten navigational trials, the average final distance of the catheter tip from the target was 2.4 ± 1.2 mm, and the range of distances from the trials was from a minimum of 1.0 mm to a maximum of 4.5 mm. CONCLUSIONS: Although early in the development process, these quantitative in vitro results show promise for catheter guidance with ultrasound imaging and tip identification by PW Doppler.

Percutaneous closure of mitral paravalvular leaks: a systematic review and meta-analysis.

BACKGROUND AND AIM OF THE STUDY: The percutaneous closure of mitral paravalvular leak (PVL) is emerging as an alternative treatment for high-risk surgical candidates. Several cases have been reported, and a few small studies have been conducted to investigate the outcome of the technique. A meta-analysis of the combined data would be considered helpful in deriving more powerful data; hence, the study aim was to conduct a meta-analysis of the percutaneous closure of mitral PVLs, as reported in the medical literature. METHODS: Searches were conducted of the PubMed, Embase, and CINAHL databases for reports of mitral PVL percutaneous closure. The data were extracted by two reviewers, who aggregated the information by using a random-effects model. RESULTS: Eight studies were included in the meta-analysis, with a total of 100 patients. The percutaneous closure of mitral PVLs was associated with a 15% cardiovascular mortality during the first year of follow up. Clinical success was noted in 48% of patients, while 52% failed to show any clinical improvement. Failures were mainly attributed either to deployment failure (18%), to the presence of a persistent leak, to hemolysis, or both (31%). Procedure-related complications (e.g., bleeding, stroke, endocarditis) were observed in 16% of patients. CONCLUSION: The percutaneous closure of mitral PVLs carries a 15% risk of cardiovascular mortality. The reported mortality rates for surgically treated patients ranged from 12% to 37%, but most patients who underwent percutaneous closure were considered high-risk surgical candidates with multiple comorbidities. While percutaneous closure appears promising, the development of lesion-specific occluders, standardized imaging techniques and parameters, and the design of randomized clinical trials to compare the outcome of surgical versus percutaneous intervention, are required before any final judgment may be made.

Potential role of Reynolds number in resolving Doppler- and catheter-based transvalvular gradient discrepancies in aortic stenosis.

BACKGROUND AND AIM OF THE STUDY: Discrepancies in mean transvalvular gradient have been observed between Doppler echocardiography and catheter-based techniques in the assessment of aortic stenosis (AS). The Reynolds number (RE) has been shown to influence Doppler-derived gradients, and may be useful in resolving Doppler- and catheter-based gradient discrepancies in AS. The study aim was to assess the influence of the RE on such discrepancies. METHODS: A pulsatile in-vitro heart model using a bioprosthetic aortic valve with leaflets sutured together was used to simulate AS. Simultaneous gradients were measured using Doppler echocardiography and high-fidelity catheters while the RE was varied, by testing solutions of different density and viscosity across a range of cardiac outputs. RESULTS: The echocardiographic and catheter-derived mean gradient (MG) values were correlated (r = 0.89; p < 0.0001); however, significant differences in the MG were observed across hemodynamic states. A direct linear relationship was identified between RE and the absolute difference in MG measured using the two techniques (r = 0.94, p < 0.0001). Relative to catheter-based measurements, the MG was underestimated by Doppler (range: 13-16 mmHg) at low RE (median 6,999) and overestimated (7-33 mmHg) at high RE (median 34,268). However, agreement between catheter- and Doppler-derived gradients was within 5 mmHg at intermediate RE (median 17,284) (p < 0.0001). CONCLUSION: The underestimation of Doppler-derived MGs at low RE relative to catheter-based measurements may be due to an exclusion of viscous friction from the simplified Bernoulli equation, while the overestimation of Doppler-derived MGs at high RE may be due to a pressure recovery effect. However, within an intermediate range of RE, where the effects of viscous and inertial forces are balanced, the agreement between catheter- and Doppler-derived gradients was excellent.

Flow velocity vector fields by ultrasound particle imaging velocimetry: in vitro comparison with optical flow velocimetry.

OBJECTIVES: We performed an in vitro study to assess the precision and accuracy of particle imaging velocimetry (PIV) data acquired using a clinically available portable ultrasound system via comparison with stereo optical PIV. METHODS: The performance of ultrasound PIV was compared with optical PIV on a benchmark problem involving vortical flow with a substantial out-of-plane velocity component. Optical PIV is capable of stereo image acquisition, thus measuring out-of-plane velocity components. This allowed us to quantify the accuracy of ultrasound PIV, which is limited to in-plane acquisition. The system performance was assessed by considering the instantaneous velocity fields without extracting velocity profiles by spatial averaging. RESULTS: Within the 2-dimensional correlation window, using 7 time-averaged frames, the vector fields were found to have correlations of 0.867 in the direction along the ultrasound beam and 0.738 in the perpendicular direction. Out-of-plane motion of greater than 20% of the in-plane vector magnitude was found to increase the SD by 11% for the vectors parallel to the ultrasound beam direction and 8.6% for the vectors perpendicular to the beam. CONCLUSIONS: The results show a close correlation and agreement of individual velocity vectors generated by ultrasound PIV compared with optical PIV. Most of the measurement distortions were caused by out-of-plane velocity components.

Cardiac abnormalities in primary hyperoxaluria.

BACKGROUND: In patients with primary hyperoxaluria (PH), oxalate overproduction can result in recurrent urolithiasis and nephrocalcinosis, which in some cases results in a progressive decline in renal function, oxalate retention, and systemic oxalosis involving bone, retina, arterial media, peripheral nerves, skin, and heart. Oxalosis involving the myocardium or conduction system can potentially lead to heart failure and fatal arrhythmias. METHODS AND RESULTS: A retrospective review of our institution's database was conducted for all patients with a confirmed diagnosis of PH between 1/1948 and 1/2006 (n=103). Electrocardiogram (ECG) and echocardiography were used to identify cardiac abnormalities. Ninety-three patients fulfilled the inclusion criteria, 58% were male. Mean follow-up was 11.9 (median 8.8) years. In 38 patients who received an ECG or echocardiography, 31 were found to have any cardiac abnormalities. Cardiac findings correlated with decline in renal function. CONCLUSIONS: Our data suggests that physicians caring for patients with PH should pay close attention to cardiac status, especially if renal function is impaired.

Impact of pericardial adhesions on diastolic function as assessed by vortex formation time, a parameter of transmitral flow efficiency.

BACKGROUND: Pericardial adhesions are a pathophysiological marker of constrictive pericarditis (CP), which impairs cardiac filling by limiting the total cardiac volume compliance and diastolic filling function. We studied diastolic transmitral flow efficiency as a new parameter of filling function in a pericardial adhesion animal model. We hypothesized that vortex formation time (VFT), an index of optimal efficient diastolic transmitral flow, is altered by patchy pericardial-epicardial adhesions. METHODS: In 8 open-chest pigs, the heart was exposed while preserving the pericardium. We experimentally simulated early pericardial constriction and patchy adhesions by instilling instant glue into the pericardial space and using pericardial-epicardial stitches. We studied left ventricular (LV) function and characterized intraventricular blood flow with conventional and Doppler echocardiography at baseline and following the experimental intervention. RESULTS: Significant decreases in end-diastolic volume, ejection fraction, stroke volume, and late diastolic filling velocity reflected the effects of the pericardial adhesions. The mean VFT value decreased from 3.61 ± 0.47 to 2.26 ± 0.45 (P = 0.0002). Hemodynamic variables indicated the inhibiting effect of pericardial adhesion on both contraction (decrease in systolic blood pressure and +dP/dt decreased) and relaxation (decrease in the magnitude of -dP/dt and prolongation of Tau) function. CONCLUSION: Patchy pericardial adhesions not only negatively impact LV mechanical functioning but the decrease of VFT from normal to suboptimal value suggests impairment of transmitral flow efficiency.

Selective echocardiographic analysis of epicardial and endocardial left ventricular rotational mechanics in an animal model of pericardial adhesions.

AIMS: Diagnosis of pericardial adhesions is challenging. Twisting of the left ventricle (LV) is essential for normal LV functioning. We experimentally characterized the impact of pericardial adhesions on epicardial and endocardial LV rotational mechanics with velocity vector imaging (VVI). METHODS AND RESULTS: In nine open-chest pigs, the heart was exposed while preserving the pericardium. Early-stage pericardial adhesions were simulated by instilling tissue glue to pericardial space. Using VVI, LV rotational mechanics was quantitatively assessed endocardially and epicardially along with haemodynamic data at baseline and following the experimental intervention. End-diastolic volume, ejection fraction, stroke volume, late diastolic filling velocity, and LV endocardial torsion decreased significantly. LV epicardial torsion showed only a trend towards decrease (P = 0.141). Endocardial twist and torsion decreased significantly (P = 0.007) from 8.6 +/- 2.2 degree and 1.497 +/- 0.397 degree/cm to 5.3 +/- 1.8 degree and 0.97 +/- 0.38 degree/cm, respectively; epicardial twist showed a trend towards a decrease in its magnitude. Gradients of endocardial/epicardial twist and torsion did not significantly change. CONCLUSION: The model suggests that early-stage pericardial adhesions reduce both epicardial and endocardial LV twist and torsion without a significant alteration in their transmural gradient. Selective endocardial/epicardial analysis of LV twisting mechanics may have a diagnostic role in detection of early formation of pericardial adhesions.

Increase in the late diastolic filling force is associated with impaired transmitral flow efficiency in acute moderate elevation of left ventricular afterload.

OBJECTIVE: Analysis of intraventricular flow force and efficiency is a novel concept of quantitatively assessing left ventricular (LV) hemodynamic performance. We have parametrically characterized diastolic filling flow by early inflow force, late inflow force, and total inflow force and by vortex formation time (VFT), a fundamental parameter of fluid transport efficiency. The purpose of this study was to determine what changes in inflow forces characterize a decrease in diastolic blood transport efficiency in acute moderate elevation of LV afterload. METHODS: In 8 open-chested pigs, the flow force and VFT parameters were calculated from conventional and flow Doppler echocardiographic measurements at baseline and during a brief (3-minute) moderate elevation of afterload induced by increasing the systolic blood pressure to 130% of the baseline value. RESULTS: Systolic LV function decreased significantly during elevated afterload. Early inflow force did not significantly change, whereas late inflow force increased from 5,822.09 +/- 1,656.5 (mean +/- SD) to 13,948.25 +/- 9,773.96 dyne (P = .049), and total inflow force increased from 13,783.35 +/- 4,816.58 to 21,836.67 +/- 8,635.33 dyne (P = .031). Vortex formation time decreased from 4.09 +/- 0.29 to 2.79 +/- 1.1 (P = .0068), confirming suboptimal flow transport efficiency. CONCLUSIONS: Even a brief moderate increase of LV afterload causes a significant increase in late diastolic filling force and impairs transmitral flow efficiency.

Patients with Alzheimer disease have altered transmitral flow: echocardiographic analysis of the vortex formation time.

OBJECTIVE: There is considerable epidemiologic evidence that Alzheimer disease (AD) is linked to cardiovascular risk factors and associated with an increased risk of symptomatic left ventricular (LV) dysfunction. Formation of a vortex alongside a diastolic jet signifies an efficient blood transport mechanism. The vortex formation time (VFT) is an index of optimal conditions for vortex formation. We hypothesized that AD and its associated cardiovascular risk factors impair diastolic transmitral flow efficiency and, therefore, shift the VFT value out of its optimal range. METHODS: Echocardiographic studies were performed on 45 participants in total: 22 patients with AD diagnosed according to the American Psychiatric Association's criteria and 23 age-matched individuals as a control group with cognitive function within normal limits. RESULTS: The echocardiographic ratio of the early to atrial phases of the LV filling velocities was significantly lower in the AD group (mean +/- SD, 0.67 +/- 14) when compared with the control individuals (0.79 +/- 0.14; P = .003). The interventricular septum diastolic thickness, left ventricular posterior wall diastolic thickness, and right ventricular end-diastolic diameter were significantly higher in the AD group (P

Three methods for evaluation of left atrial volume.

AIM: To compare and contrast 3 different echocardiographic methods used to measure left atrial (LA) volume: biplane area length (AL), biplane modified Simpson (SIMP), and prolate ellipse (PE) methods. METHODS AND RESULTS: A review of consecutive patients who presented to our outpatient echocardiography laboratory for a resting transthoracic study between April 2006 and May 2006 was performed. Echocardiograms were reexamined and LA volume measured using the AL, SIMP, and PE methods. Of 102 consecutive patients evaluated, 97 had a measure of LA volume using all 3 methods. A significant difference in the measurement of mean +/- SD LA volume was noted among the 3 different methods: 37 +/- 16 mL/m(2) for AL, 34 +/- 14 mL/m(2) for SIMP, and 27 +/- 12 mL/m(2) for PE. The PE method yielded routinely smaller values compared with either the AL or SIMP method (P < 0.001). Differences increased with increased LA volume. The SIMP method derived consistently smaller (<5 mL/m(2)) values than those of the AL method, consistent across the full range of LA volumes. CONCLUSION: Significant differences exist among these 3 commonly used methods for measuring LA volume. Standardization of the measurement of LA volume is recommended.

The metabolic syndrome and cardiovascular disease: Part I.

The metabolic syndrome is a constellation of metabolic risk factors and physical conditions that are accompanied by an enhanced propensity toward the development of type 2 diabetes, atherosclerosis, and cardiovascular disease. It presents a combination of atherosclerosis risk including atherogenic dyslipidemia, hypertension, elevated plasma glucose, hypercoagulability, and a proinflammatory state. The 2 major underlying risk factors for the metabolic syndrome are obesity and insulin resistance. Exacerbating factors are physical inactivity, advancing age, and endocrine and genetic factors. Associated hyperinsulinemia, hyperglycemia, and elevated adipokine levels (adipose cytokines) lead to vascular endothelial dysfunction, an abnormal lipid profile, hypertension, and vascular inflammation, all of which promote the development of atherosclerotic cardiovascular disease. In this 2-part series, the authors present an up-to-date and detailed systematic review of the literature on this important topic.

An uncommon cause of epistaxis: cartoid cavernous fistula.

We report on an uncommon cause of epistaxis presenting to the emergency room. Epistaxis is not an uncommon presentation to emergency rooms across the world. The majority are easily controlled and have low mortality. We present a case of a carotid-cavernous fistula presenting with massive epistaxis culmination in cardiovascular collapse and death. Awareness of this entity will reduce the frequency of this condition resulting in major morbidity and mortality.

Detection of progressive myocardial tissue injury by ultrasonic integrated backscatter immediately after coronary reperfusion.

Myocardial reperfusion following ischemia may paradoxically cause additional injury, including microvascular damage and edema. These structural alterations augment tissue echogenicity, which is measurable by ultrasonic integrated backscatter (IB). We sought to characterize alterations in myocardial IB in an ischemic and reperfused region of the rat heart. Myocardial IB of the regions of interest in 12 adult male Sprague-Dawley rats was studied at baseline, during ischemia, and chronologically after coronary reopening, using an ultrasound frequency of 8 MHz. IB did not significantly change between baseline and ischemia. However, within 1 min of reperfusion, IB significantly increased and continued to increase until 10 min of reperfusion, when a plateau was reached. Areas of high echogenicity were comparable to infarcted areas on gross pathologic slices and had edema with extravasation of red blood cells. Myocardial reperfusion following ischemia significantly augments tissue echogenicity. A continuing increase of IB suggests a rapid progression of reperfusion injury.

Constrictive pericarditis and restrictive cardiomyopathy in the modern era.

The differentiation between constrictive pericarditis and restrictive cardiomyopathy can be clinically challenging. Pericardial constriction results from scarring and consequent loss of pericardial elasticity leading to impaired ventricular filling. Restrictive cardiomyopathy is characterized by a nondilated rigid ventricle, severe diastolic dysfunction and restrictive filling producing hemodynamic changes, similar to those in constrictive pericarditis. While constrictive pericarditis is usually curable by surgical treatment, restrictive cardiomyopathy requires medical therapy and in appropriate patients, the definitive treatment is cardiac transplantation. Sufficient differences exist between the two conditions to allow noninvasive differentiation, but no single diagnostic tool can be relied upon to make this distinction. Newer echocardiographic techniques such as speckle-track imaging, velocity vector imaging, as well as cardiac computed tomography and cardiac MRI can help differentiate constriction from restriction with high sensitivity and specificity. Outcomes are better with early diagnosis of constriction in particular and early surgical resection.

Ultrasound-guided placement of a renal artery stent using an intracardiac probe for transvascular imaging.

In this set of images obtained during an experimental study using a porcine animal model, we introduce ultrasound guidance of percutaneous transluminal renal angioplasty and renal stenting. A state-of-the-art intracardiac ultrasound catheter is used here for transvascular scanning from within the lumen of the abdominal aorta, thus providing a field of view for navigation of a balloon catheter and a wire coil ("stent") into each renal artery of a pig. This study is intended as a contribution to the growing field of minimally invasive interventions and their navigation by non-ionizing ultrasound imaging.

Risk of adverse events after coronary artery bypass graft and subsequent noncardiac surgery.

AIMS: Coronary artery bypass grafts (CABGs) are increasingly performed in elderly patients. Risk factors and outcomes are poorly described for those undergoing noncardiac surgery within 1 year after CABG. Our objectives were to assess the risk and predictors of major adverse events associated with noncardiac surgery within 1 year after CABG. METHODS: In a retrospective review of medical records at Mayo Clinic (Rochester, MN, USA), over a period of 5 years, we identified patients who underwent noncardiac procedures within 1 year post-CABG. All events that occurred within 30 days after noncardiac surgery and deaths within 1 year after noncardiac surgery were considered to be related to CABG. RESULTS: We identified 211 patients; of these, 21 patients had 24 adverse events. Within 1 year, 11 died, and within the first 30 days, three myocardial infarctions, six acute congestive heart failure episodes, three cerebrovascular accidents and one deep vein thrombosis episode had occurred. Predictors of an adverse event included emergency operation (odds ratio: 6.8), ejection fraction less than 45% (p < 0.001) and elevated right ventricular systolic pressure by 40 mmHg or more (p = 0.03). After the noncardiac procedure, patients requiring dialysis (p = 0.02), ventilatory support (p = 0.03) and longer hospital stay (p = 0.03) had greater rates of adverse outcomes. CONCLUSION: Post-CABG, preoperative ejection fraction less than 45%, right ventricular systolic pressure of 40 mmHg or more, as well as emergent noncardiac surgery, were predictors of adverse outcomes after the noncardiac procedure. Longer postoperative hospital stay, dialysis, as well as ventilatory support, were predictors of adverse outcomes after CABG.

The left ventricle responds to acute graded elevation of right ventricular afterload by augmentation of twist magnitude and untwist rate.

BACKGROUND: The right and left ventricles share the interventricular septum, which mechanically transmits pressure gradients. The aim of this study was to investigate how acute mild or moderate right ventricular (RV) afterload affects left ventricular (LV) function. METHODS: In 14 open-chest pigs (mean weight, 43 ± 4 kg) with preserved pericardium, acute mild (>35 and ≤50 mm Hg) and moderate (>50 and ≤60 mm Hg) RV pressure loading conditions were induced by constriction of the pulmonary artery. Hemodynamic parameters and LV twist and untwist were evaluated under each condition. RESULTS: From baseline to mild and moderate RV afterload, the mean RV systolic pressure increased from 31.0 ± 4.3 to 41.1 ± 2.7 and 52.7 ± 3.4 mm Hg (P < .001), while LV twist magnitudes increased from 15.4 ± 5.1° to 18.5 ± 3.1° and 19.8 ± 5.0° (P = .004), respectively. Absolute values of LV untwist rate increased from -116.9 ± 64.9°/sec to -160.0 ± 53.3°/sec and -169.1 ± 47.0°/sec, respectively (P = .001). After adjusting for all variables, only the ratio of the early and atrial components of mitral inflow and RV outflow tract acceleration time was significantly associated with the LV twist magnitude and LV untwist rate. CONCLUSIONS: In an acute setting, the left ventricle responds to suddenly elevated RV afterload and decreased RV stroke volume by promptly increasing its twist magnitude and untwist rate.

Epicardial fat and its association with cardiovascular risk: a cross-sectional observational study.

BACKGROUND: The association between visceral obesity and cardiovascular risk has been well described. Some studies show a proportional relationship between the presence of visceral obesity and epicardial fat. Measuring the amount of epicardial adipose tissue (EAT) can be a novel parameter that is inexpensive and easy to obtain and may be helpful in cardiovascular risk stratification. However, the relationship between epicardial fat and cardiac function and that between epicardial fat and cardiac risk factors is less well described. OBJECTIVES: To evaluate the association between echocardiographic epicardial fat and the morphologic and physiologic changes observed at echocardiography and to evaluate the association between epicardial fat and cardiac risk factors. A cross-sectional study of 97 echocardiographic studies (females, n = 42) was conducted. Two groups were identified: epicardial fat ≥ 5 mm (group I) and <5 mm (group II). RESULTS: Epicardial fat >5 mm was associated with LA enlargement, with lower ejection fraction, increased left ventricular mass, and abnormal diastolic function. On a multivariable regression analysis, all these parameters also correlated individually with EAT thickness independent of age. Hyperglycemia (DM), systolic hypertension, and lipid parameters for metabolic syndrome showed a trend for positive association, but this was not statistically significant. The association was not significant even for higher cutoff limits of EAT thickness. CONCLUSION: Epicardial fat >5 mm is associated with cardiac abnormalities on echocardiography. This is a sensitive assessment of body fat distribution, is easily available at echocardiography, and is simple to acquire at no added cost. Further studies looking at the appropriate cut-off thickness of EAT and the sites of measurement to be used are needed. Comparison of this simple and inexpensive measure with other measures of obesity, such as waist-hip ratio, body mass index, Dexa scan of visceral fat, and magnetic resonance imaging of visceral, are needed.

Critical appraisal on the utility of echocardiography in the management of acute pulmonary embolism.

Echocardiography can be used for rapid and accurate risk stratification of patients with pulmonary embolism to appropriately direct the therapeutic strategies for those at high risk. Echocardiography is an ideal risk stratification tool in this regard because of its easy portability to the emergency room or to the bed side. It can be performed at a relatively low cost and at no risk to the patient. Furthermore, echocardiography allows repetitive noninvasive assessment of the cardiovascular and hemodynamic status of the patient and the response to the therapeutic interventions. Right ventricular hypokinesis, persistent pulmonary hypertension, a patent foramen ovale, and a free floating right heart thrombus are echocardiographic markers that identify patients at a higher risk for morbidity and mortality. Such patients warrant special consideration for thrombolysis or embolectomy.

Pulmonary thromboembolic disease spectrum: diagnostic and therapeutic strategies.

Pulmonary thromboembolic disease continues to be a challenge in terms of diagnosis and management. This is true for both the acute and chronic forms. Clinical presentation can be nonspecific and manifestations protean, hence a high index of clinical suspicion is warranted so that appropriate tests are performed to help clinch the diagnosis. Acute pulmonary embolus can result in death if untreated, and may progress to chronic thromboembolic pulmonary hypertension if not diagnosed or if it is undertreated. This extensive literature review provides an up-to-date evidence-based approach to the management of acute and chronic pulmonary thromboembolic disease.