A Pilot Study on Novel Use of Color Doppler Imaging for Navigation of Wiring in Coronary Interventions.

OBJECTIVE: To test the Doppler guide wire (DGW) for navigation of the wire positioning by color Doppler ultrasound in the setting of percutaneous coronary intervention (PCI). METHODS: An acoustically active DGW was tested in a water tank before its in vivo use. A waveform generator was connected to the DGW, and a transducer scanned the DGW to visualize a Doppler shift signal between the vibrating piezoelectric crystal located at the DGW tip and Doppler signal from the transducer as a distinct, instantaneous color marker. An intracoronary injection was tested in four male domestic pigs using an open-chest setting. A Judkins left coronary guiding catheter was inserted into the ascending aorta via the right carotid artery under B-mode ultrasound guidance. The DGW with an infusion catheter or over-the-wire (OTW) balloon catheter was inserted into the guiding catheter. The color marker instantaneously defined the DGW tip and navigated the catheter into the left anterior descending artery (LAD). RESULTS: The tip of the DGW was visualized within the guiding catheter by a distinct color marker and helped to engage the guiding catheter to the left main orifice. The DGW with an infusion or OTW balloon catheter was inserted into the LAD. We confirmed that the catheter was positioned in the proximal LAD by the colored territory perfused by an injected indigo carmine solution. CONCLUSION: Ultrasound navigation using acoustically active DGW was feasible. Our pilot study introduces a new concept of color Doppler-navigated wire positioning in the coronary artery in the setting of PCI.

Doppler-Guided Acoustically Active Injection Catheter: Transendocardial Delivery Assessed by an Efficacy Testing Animal Model.

Percutaneous transendocardial injections of therapeutic agents into the myocardium may not always be effective. We used an animal model for assessing the efficacy of the injections using linoleic acid as a testing agent. Efficacious delivery into the myocardium of a beating heart was indicated by rapidly developed local myocardial necrosis and wall motion abnormalities using echocardiography. We employed this experimental model to test our innovative technology, an acoustically active injection catheter. The Doppler ultrasound-guided acoustically active injection catheter effectively delivers the substance to the myocardium but needs further technical improvements to minimize an unwanted systemic distribution of the agent.

A Case of Severe Mitral Valve Regurgitation in a Patient with Leadless Pacemaker.

An 85-year-old man with cardiac history notable for atrial fibrillation diagnosed 10 years ago which was being treated with atenolol and warfarin presented to our institution with persistent atrial fibrillation. His echocardiogram showed ejection fraction (EF) of 56%, no regional wall motion abnormalities, mild mitral and pulmonary regurgitation, and trivial tricuspid regurgitation. Despite this treatment, he had recurrent episodes of paroxysmal symptomatic atrial fibrillation with a rapid rate requiring multiple emergency department visits and hospital admissions. Given difficulty to control the rate, he underwent atrioventricular (AV) nodal ablation and leadless pacemaker insertion. Fifteen days after the procedure, he was found to have a severe mitral regurgitation murmur.

Real-Time Visualization of an Acoustically Active Injection Catheter With Ultrasound Imaging: Algorithm and In Vivo Validation in a Swine Model.

OBJECTIVE: To independently visualize a catheter and needle during minimally invasive surgery in order to aid in precisely guiding them to their intended location. METHODS: Symmetric frequency detection allows for the visualization of the acoustically active catheter tip as a unique color in live imaging. This study extends the algorithm to identify two different crystals by unique colors, validating the algorithm with in vivo pig experiments while simulating the human condition using different attenuation pads. RESULTS: The catheter and needle tip were identified with unique colors, differentiable from common Doppler colors, with a frame rate varying between 8 and 10 Hz. Both were visible at graded levels of attenuation induced by interposed polymer pads. Reducing ensemble length increased the frame rate and decreased the signal-to-noise ratio (SNR), though not significantly. At the highest in-path attenuation of 12 dB at 5 MHz, the catheter spot marker was visible whereas the needle was not. The SNR of the catheter signal varied between 12.50 and 18.24 dB and the size of the spot marker varied between 149 and 1015 mm2. The SNR of the needle signal varied between 6.37 and 16.3 dB and the size of the spot marker between 59 and 169 mm2. A reliability index greater than 50% was achieved for all cases except for the needle crystal at the highest attenuation setting. CONCLUSION: Modified symmetric frequency detection algorithm can uniquely visualize both catheter and needle in real time with in-path attenuation. SIGNIFICANCE: Unambiguous and distinct visualization of separate locations on the catheter facilitates real-time tracking of minimally invasive procedures.

A Real-time Color Doppler Marker for Echocardiographic Guidance of an Acoustically Active Extracorporeal Membrane Oxygenation Cannula.

B-mode ultrasound imaging guidance of cannulas can be compromised by noise, artifacts, and echogenicity that is not distinctive from that of surrounding anatomy. We have modified a venovenous extracorporeal membrane oxygenation cannula by embedding piezoelectric crystals into each of its 3 blood flow ports. Each vibrating crystal acoustically interacts with a Doppler imaging signal and produces an instantaneous color marker. The aim of this study was to compare identification of the extracorporeal membrane oxygenation cannula ports by B-mode imaging versus the color Doppler marker. Unlike B-mode imaging, the color Doppler marker identified the corresponding port even in highly challenging closed-chest scans in anesthetized pigs. The method could improve guidance accuracy of cannulas by ultrasound scans.

An Interposed Pad in Open-Chest Echocardiographic Porcine Scans for Mimicking Ultrasound Signal Attenuation in a Human Chest.

Opening a chest in an experimental echocardiographic animal study eliminates ultrasound signal attenuation by the chest wall. We developed a scanning technique that involves the use of an attenuative pad created from a mixture of urethane and titanium dioxide. The pad was interposed within transmission gel between the transducer face and cardiac surface in open-chest scans in a porcine model. Comparative measurements of left ventricular echogenicity without and with the pad demonstrate that the pad reproducibly causes ultrasound signal attenuation that closely mimics chest attenuation in clinical transthoracic echocardiographic studies.

Left Ventricular Septal Hypertrophy in Elderly Patients With Aortic Stenosis.

OBJECTIVES: Left ventricular (LV) septal hypertrophy in aortic stenosis raises diagnostic and therapeutic questions. However, the etiology and clinical consequences of this finding have not been well studied. The aim of this study was to perform a morphologic evaluation of the LV in aortic stenosis and to investigate the contributing factors and consequences of septal hypertrophy. METHODS: Patients with moderate or severe aortic stenosis were prospectively enrolled. Patients with previous myocardial infarction, wall motion abnormalities, at least moderate valvular regurgitation, known cardiomyopathy, an LV ejection fraction of less than 50%, and age younger than 65 years were excluded. RESULTS: Forty-one patients underwent a final analysis. Septal hypertrophy (LV septal wall thickness ≥15 mm) was confirmed in 21 of 41 patients. The septal hypertrophy group had higher peak aortic valve velocity, a higher diabetes mellitus rate, and a higher rate and longer duration of hypertension than those without septal hypertrophy. The peak aortic valve velocity (odds ratio, 7.1; 95% confidence interval, 1.4-37.1) and diabetes mellitus (odds ratio, 7.4; 95% confidence interval, 1.2-46.2) were the significant factors associated with septal hypertrophy by multivariate analysis. Intraventricular conduction disturbance on electrocardiography was more frequent in the septal hypertrophy group (P = .021). CONCLUSIONS: Left ventricular septal hypertrophy was commonly observed in elderly patients with aortic stenosis, and a higher aortic valve velocity, hypertension, and diabetes mellitus were associated factors. Intraventricular conduction disturbance occurred more often in patients with septal hypertrophy than those without, which implies the pathophysiologic consequence. Further studies are needed to determine the impact of septal hypertrophy and intraventricular conduction disturbance on the prognosis of patients after aortic valve interventions.

Acoustically Active Catheter for Intracardiac Navigation by Color Doppler Ultrasonography.

Navigation of intracardiac catheters by echocardiography is challenging because of the fundamental limitations of B-mode ultrasonography. We describe a catheter fitted with a piezoelectric crystal, which vibrates and produces an instantaneous marker in color flow Doppler scans. The navigation learning curve was explored first in six pigs. Accuracy and precision of targeting with the navigation marker "off" (i.e., B-mode imaging) and "on" were assessed in another six pigs. Paired comparisons confirmed significantly (p = 0.04) shorter mean distances achieved in each pig with the color Doppler marker. Pooled (mean ± standard deviation) distance of the catheter tip from the target crystal was 5.27 ± 1.62 mm by B-mode guidance and 3.66 ± 1.45 mm by color Doppler marker navigation. Dye injection targeted into the ischemic border zone was successful in 8 of 10 pigs. Intracardiac catheter navigation with color Doppler ultrasonography is more accurate compared with conventional guidance by B-mode imaging.

Predictors of Elevated Cardiac Enzyme Levels in Hospitalized Patients with Atrial Fibrillation and No Known Coronary Artery Disease.

We retrospectively studied the predictive capabilities of elevated cardiac enzyme levels in terms of the prognosis of patients who were hospitalized with atrial fibrillation and who had no known coronary artery disease. Among 321 patients with atrial fibrillation, 60 without known coronary artery disease had their cardiac enzyme concentrations measured during hospitalization and underwent stress testing or cardiac catheterization within 12 months before or after hospitalization. We then compared the clinical and electrocardiographic characteristics of the 20 patients who had elevated cardiac enzyme levels and the 40 patients who had normal levels. Age, sex, and comorbidities did not differ between the groups. In the patients with elevated cardiac enzyme levels, the mean concentrations of troponin T and creatine kinase-MB isoenzymes were 0.08 ± 0.08 ng/mL and 6.49 ± 4.94 ng/mL, respectively. In univariate analyses, only peak heart rate during atrial tachyarrhythmia was predictive of elevated enzyme levels (P <0.0001). Mean heart rate was higher in the elevated-level patients (146 ± 22 vs 117 ± 29 beats/min; P=0.0007). Upon multivariate analysis, heart rate was the only independent predictor of elevated levels. Coronary artery disease was found in only 2 patients who had elevated levels and in one patient who had normal levels (P=0.26). Increased myocardial demand is probably why the presenting heart rate was predictive of elevated cardiac enzyme levels. Most patients with elevated enzyme levels did not have coronary artery disease, and none died of cardiac causes during the 6-month follow-up period. To validate our findings, larger studies are warranted.

Diagnosis and management of patients with asymptomatic severe aortic stenosis.

Aortic stenosis (AS) is a disease that progresses slowly for years without symptoms, so patients need to be carefully managed with appropriate follow up and referred for aortic valve replacement in a timely manner. Development of symptoms is a clear indication for aortic valve intervention in patients with severe AS. The decision for early surgery in patients with asymptomatic severe AS is more complex. In this review, we discuss how to identify high-risk patients with asymptomatic severe AS who may benefit from early surgery.

Visual Estimation of the Severity of Aortic Stenosis and the Calcium Burden by 2-Dimensional Echocardiography: Is It Reliable?

OBJECTIVES: Guidelines have recommended aortic valve surgery in asymptomatic patients with severe aortic stenosis and a large aortic valve calcium burden. The purpose of this study was to determine whether visual assessment of aortic valve calcium and stenosis severity are reliable based on 2-dimensional echocardiography alone. METHODS: We prospectively enrolled 68 patients with aortic stenosis and compared them with 30 control participants without aortic stenosis. All had aortic valve calcium score assessment by computed tomography. In a random order, 2-dimensional images without hemodynamic data were independently reviewed by 2 level 3-trained echocardiographers, who then classified these patients into categories based on aortic valve calcium and stenosis severity. RESULTS: The 68 patients (mean age ± SD, 74 ± 10 years) were classified as having mild (n = 28), moderate (n = 22), and severe (n = 18) aortic stenosis. When the observers were asked to grade the degree of valve calcification, the agreement between them was poor (κ = 0.33-0.39). The visual ability to determine stenosis severity compared with Doppler echocardiography had high specificity (81% and 88% for observers 1 and 2). However, sensitivity was unacceptably low (56%-67%), and the positive predictive value was poor (44%-50%). Agreement was fair (κ= 0.58-0.69) between the observers for determining severe stenosis. CONCLUSIONS: Our results suggest that visual assessment of aortic valve calcium has high interobserver variability; the visual ability to determine severe aortic stenosis has low sensitivity but high specificity. Our results may have important implications for treatment of patients with aortic stenosis and guiding the use of handheld echocardiography. Further research with larger cohorts is needed to validate the variability, sensitivity, and specificity reported in our study.

Does valvuloarterial impedance impact prognosis after surgery for severe aortic stenosis in the elderly?

BACKGROUND: Valvuloarterial impedance (Zva) was introduced as a prognostic measure in patients with aortic stenosis (AS). However, it is unclear whether Zva has a prognostic impact on survival after surgical aortic valve replacement (AVR) in patients with severe AS with preserved ejection fraction (EF). METHODS: We retrospectively reviewed 929 consecutive patients who had AVR. We investigated 170 elderly patients (age >65 years, mean 76 years) who had AVR secondary to severe AS (mean gradient ≥40 mm Hg; aortic valve area ≤1 cm(2); peak velocity ≥4 m/s). Patients with EF <50%, greater than moderate aortic regurgitation, prior heart surgery and concomitant mitral or tricuspid valve surgery were excluded. Zva was calculated and the patients were divided into two groups; low Zva, Zva <4.3 (n=82) and high Zva, Zva ≥4.3 (n=88). The end point was all-cause of death. Survival curves were calculated according to Kaplan-Meier method. RESULTS: Age, prevalence of hypertension, diabetes, chronic kidney disease (CKD), atrial fibrillation, symptoms, EF, E/e' and concomitant coronary artery bypass graft were not different between the groups. Survival was not different between the groups at 5 years (70% in low Zva and 81% in high Zva; p=0.21) and for the entire follow-up period (p=0.23). Only age was a significant factor in predicting survival by multivariate analyses in Cox proportional hazards model after adjusting for Zva, CKD, atrial fibrillation and hypertension. CONCLUSIONS: Our results suggest that preoperative Zva does not have a prognostic impact on postoperative survival in elderly patients with severe AS with preserved EF. Further investigation is needed to elucidate the controversial results.

Acoustically active injection catheter guided by ultrasound: navigation tests in acutely ischemic porcine hearts.

Catheters are increasingly used therapeutically and investigatively. With complex usage comes a need for more accurate intracardiac localization than traditional guidance can provide. An injection catheter navigated by ultrasound was designed and then tested in an open-chest model of acute ischemia in eight pigs. The catheter is made "acoustically active" by a piezo-electric crystal near its tip, electronically controlled, vibrating in the audio frequency range and uniquely identifiable using pulsed-wave Doppler. Another "target" crystal was sutured to the epicardium within the ischemic region. Sonomicrometry was used to measure distances between the two crystals and then compared with measurements from 2-D echocardiographic images. Complete data were obtained from seven pigs, and the correlation between sonomicrometry and ultrasound measurements was excellent (p < 0.0001, ρ = 0.9820), as was the intraclass correlation coefficient (0.96) between two observers. These initial experimental results suggest high accuracy of ultrasound navigation of the acoustically active catheter prototype located inside the beating left ventricle.

Long-term clinical outcome after intramuscular transplantation of granulocyte colony stimulating factor-mobilized CD34 positive cells in patients with critical limb ischemia.

BACKGROUND: Our phase I/IIa clinical trial revealed that intramuscular transplantation of autologous, GCSF-mobilized CD34+ cells was safe, feasible and potentially effective at week 4 and 12 post cellular therapy in 17 patients with chronic critical limb ischemia (CLI) (5 patients with atherosclerotic peripheral arterial disease (PAD) and 12 with Buerger's disease). However, long-term outcome of the cell therapy has yet to be reported. METHODS AND RESULTS: Incidence of major clinical events and physiological parameters of limb ischemia were evaluated at week 52, 104, 156 and 208 post CD34+ cell therapy. No patients died by week 104, whereas 3 patients with PAD died by week 156 and 1 patient with Buerger's disease died by week 208 due to cardiac complications. No patients underwent major amputation, whereas 1 patient with Buerger's disease underwent unplanned minor amputation by week 104. CLI-free ratio was 88.2% at week 52 and 104, 92.3% at week 156 and 84.6% at week 208 in all patients. Significant improvement of toe brachial pressure index versus baseline was sustained up to week 208 and that of transcutaneous partial oxygen pressure was kept up to week 156. The Wong-Baker FACES pain rating scale, ulcer size and exercise tolerance significantly improved at week 52, the final evaluation time point, compared with baseline. Subgroup analysis revealed the similar outcome in patients with Buerger's disease. CONCLUSIONS: Favorable clinical outcomes as well as physiological evidences strongly indicate the long-term benefit of GCSF-mobilized CD34+ cell transplantation for retrieval from CLI, especially in patients with Buerger's disease.

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.

Newly diagnosed glucose intolerance and prognosis after acute myocardial infarction: comparison of post-challenge versus fasting glucose concentrations.

BACKGROUND: Recent studies have demonstrated that newly diagnosed glucose intolerance is common among patients with acute myocardial infarction (AMI). The purpose of this study was to assess the long-term clinical cardiovascular outcomes in participants with AMI with abnormal fasting glucose compared with normal fasting glucose and an abnormal oral glucose tolerance test (OGTT) compared with a normal OGTT. METHODS: A prospective study was performed in 275 consecutive patients with AMI, 85 of whom had pre-diagnosed diabetes mellitus (DM). Those without DM were divided into two groups based on the 75 g OGTT at the time of discharge. Abnormal glucose tolerance (AGT) was defined as 2 h glucose ≥140 mg/dl; 78 patients had normal glucose tolerance (NGT) and 112 had AGT. The same patients were also reclassified into the normal fasting glucose group (NFG; n=168) or the impaired fasting glucose group (IFG; n=22). The association between the glucometabolic status and long-term major adverse cardiovascular event rates was evaluated. RESULTS: Kaplan-Meier survival curves showed that the AGT group had a worse prognosis than the NGT group and an equivalent prognosis to the DM group (p<0.0005). Cox proportional hazard model analysis showed that the HR of AGT to NGT for major adverse cardiovascular event rates was 2.65 (95% CI 1.37 to 5.15, p=0.004) while the HR of DM to NGT was 3.27 (1.68 to 6.38, p=0.0005). However, Cox HR of IFG to NFG for major adverse cardiovascular event rates was 1.83 (0.86 to 3.87), which was not significant. CONCLUSION: In patients with AMI, an abnormal OGTT is a better risk factor for future adverse cardiovascular events than impaired fasting blood glucose.

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.

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.

Fulminant fatal cardiotoxicity following cyclophosphamide therapy.

A 59-year-old male with an abdominal mass that showed a diffuse large B cell lymphoma underwent extirpation of the tumor and chemotherapy. He subsequently received high-dose chemotherapy containing cyclophosphamide (1.5 g/m(2)/day x 2 days), followed by autologous peripheral blood stem cell transplantation. He developed congestive heart failure 5 days after administration of cyclophosphamide. His electrocardiogram showed extremely low voltage with ST segment change and echocardiogram showed diffusely increased left ventricular wall thickness, an increase in myocardial echogenicity, pericardial effusion, and generally decreased systolic function. Congestive heart failure progressed rapidly and he died the following day. Post-mortem examination of the heart revealed myocardial hemorrhage, yellowish brown pericardial effusion, and fibrinous pericarditis. His liver was atrophic and focal necrosis was observed histologically. Cyclophosphamide-induced cardiotoxicity occurred, even though the patient had both shown normal cardiac function before high-dose chemotherapy and had received a lower dose of cyclophosphamide. Concomitant administration of cytarabine might have affected his liver function and there might have been interaction between the drugs.