Andrew Weintraub

Intracardiac, intravascular, two-dimensional, high-frequency ultrasound imaging of pulmonary artery and its branches in humans and animals

Intravascular ultrasound imaging is a promising new method for assessing vascular morphology. We evaluated the capability of intravascular ultrasound to quantify pulmonary artery (PA) morphology in vitro and explored the feasibility of in vivo PA imaging in animals and humans. In the in vitro study of 15 PA segments, we used a 20-MHz prototype ultrasound catheter. Intravascular ultrasound (y) provided crisp images of PA segments and demonstrated excellent correlations with anatomic measurements (x) in the estimation of luminal area (y = 0.89x + 2.95, r = 0.99, p less than 0.001), luminal diameter (n = 30, y = 0.79x + 0.96, r = 0.92, p less than 0.001), and vessel wall thickness (n = 60, y = 0.65x + 0.33, r = 0.85, p less than 0.001). We subsequently introduced the probe into the PA of 10 dogs and were able to obtain real-time, two-dimensional images of the main PA, its major branches, and farther smaller branches as far as the wedge level. To evaluate the in vivo feasibility of PA imaging in conscious humans, we used a commercially available, 20-MHz intravascular ultrasound (IVUS) catheter in 22 subjects through a femoral or jugular venous sheath at the end of standard diagnostic cardiac catheterization. In 20 subjects, we acquired dynamic, high-resolution, cross-sectional images of the proximal and distal PA. Changes in shape and decreasing luminal area could be clearly recognized as the IVUS catheter reached branching points and as it passed more distally. There were no complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracardiac echocardiography in humans using a small-sized (6F), low frequency (12.5 MHz) ultrasound catheter methods, imaging planes and clinical experience

OBJECTIVES This study was designed to determine the clinical utility and feasibility of using 12.5-MHz ultrasound catheters for intracardiac echocardiography. BACKGROUND Intracardiac echocardiography is a potentially useful technique of cardiac imaging and monitoring in certain settings. The feasibility of intracardiac echocardiography using 20-MHz ultrasound catheters in patients has been demonstrated. High resolution images of normal cardiac structures as well as cardiac abnormalities have been obtained. However, imaging has been limited by the shallow depth of field inherent in high frequency ultrasound imaging. METHODS Intracardiac echocardiography with 12.5-MHz catheters was performed in eight mongrel dogs and 92 patients. Catheters were introduced percutaneously in 80 patients studied in the catheterization laboratory and directly into the heart in 12 patients in the operating room. Right heart imaging was performed in 68 patients and arterial and left heart imaging in 35 patients. RESULTS When these catheters were introduced into the venous system, the right atrium, tricuspid valve, right ventricle, pulmonary valve and pulmonary artery were visualized. Pericardial effusion, intracardiac masses and atrial septal defects were correctly identified. The left ventricle, left atrium, mitral valve, aortic valve, aorta and coronary arteries could be imaged from the arterial circulation. Diseases identified included valvular aortic stenosis, subvalvular aortic stenosis and Kawasaki disease. Average imaging time was 10 min. No complications occurred as a result of intracardiac echocardiography. CONCLUSIONS Intracardiac echocardiography with 12.5-MHz ultrasound catheters is safe and feasible; it also provides anatomic and physiologic information. This feasibility study provides a foundation for wider clinical use of intracardic echocardiography.

Real-time intravascular ultrasound imaging in humans

The capability of obtaining cross-sectional, high resolution images of arteries with the use of ultrasound catheters has recently been demonstrated in animal studies. In this study the in vivo feasibility of intravascular ultrasound imaging in humans was evaluated. In 26 patients who had undergone diagnostic cardiac catheterization or iliofemoral arteriography, 1 of 3 different models of 20-MHz ultrasound catheters was advanced retrograde, into the iliac arteries and aorta or anterograde into the femoral arteries and real-time cross-sectional images of the arteries were obtained in all. In 10, the iliac arteries were normal and appeared circular and pulsatile with a 3-layered wall and crisply defined lumens. In 7 patients with nonobstructive plaques, the plaque was easily identified in the ultrasound image as a linear, bright, adynamic echo-dense structure. In 4 with obstructive disease in the iliac artery, the arterial lumen appeared irregular, bordered by a thickened, nonpulsatile wall. Variable grades of atheromatous abnormalities in the wall could be visualized. In all 5 patients with arteriographic evidence of obstructive disease of the femoral artery, intravascular ultrasound displayed reduced lumens and irregular borders with protruding high-intensity echoes in the wall. In all patients, the arterial lumen and the normal or abnormal wall were well visualized in the ultrasound images. There were no complications. This study thus demonstrates the feasibility of intravascular ultrasound imaging of arterial circulation in humans. With further improvements in catheter design and image quality, this imaging approach is likely to have a number of potential applications in the assessment of peripheral and coronary arterial diseases and in guiding interventional therapeutic procedures.

A Multicenter Randomized Controlled Evaluation of Automated Home Monitoring and Telephonic Disease Management in Patients Recently Hospitalized for Congestive Heart Failure: The SPAN-CHF II Trial

BACKGROUND We performed a prospective, randomized investigation assessing the incremental effect of automated health monitoring (AHM) technology over and above that of a previously described nurse directed heart failure (HF) disease management program. The AHM system measured and transmitted body weight, blood pressure, and heart rate data as well as subjective patient self-assessments via a standard telephone line to a central server. METHODS AND RESULTS A total of 188 consented and eligible patients were randomized between intervention and control groups in 1:1 ratio. Subjects randomized to the control arm received the Specialized Primary and Networked Care in Heart Failure (SPAN-CHF) heart failure disease management program. Subjects randomized to the intervention arm received the SPAN-CHF disease management program in conjunction with the AHM system. The primary end point was prespecified as the relative event rate of HF hospitalization between intervention and control groups at 90 days. The relative event rate of HF hospitalization for the intervention group compared with controls was 0.50 (95%CI [0.25-0.99], P = .05). CONCLUSIONS Short-term reductions in the heart failure hospitalization rate were associated with the use of automated home monitoring equipment. Long-term benefits in this model remain to be studied.

Bivalirudin Is a Dual Inhibitor of Thrombin and Collagen-Dependent Platelet Activation in Patients Undergoing Percutaneous Coronary Intervention

Background— Bivalirudin, a direct thrombin inhibitor, is a widely used adjunctive therapy in patients undergoing percutaneous intervention (PCI). Thrombin is a highly potent agonist of platelets and activates the protease-activated receptors, PAR1 and PAR4, but it is not known whether bivalirudin exerts antiplatelet effects in PCI patients. We tested the hypothesis that bivalirudin acts as an antiplatelet agent in PCI patients by preventing activation of PARs on the platelet surface. Methods and Results— The effect of bivalirudin on platelet function and systemic thrombin levels was assessed in patients undergoing elective PCI. Mean plasma levels of bivalirudin were 2.7±0.5 &mgr;mol/L during PCI, which correlated with marked inhibition of thrombin-induced platelet aggregation and significantly inhibited cleavage of PAR1. Unexpectedly, bivalirudin also significantly inhibited collagen-platelet aggregation during PCI. Collagen induced a conversion of the platelet surface to a procoagulant state in a thrombin-dependent manner that was blocked by bivalirudin. Consistent with this result, bivalirudin reduced systemic thrombin levels by >50% during PCI. Termination of the bivalirudin infusion resulted in rapid clearance of the drug with a half-life of 29.3 minutes. Conclusions— Bivalirudin effectively suppresses thrombin-dependent platelet activation via inhibition of PAR1 cleavage and inhibits collagen-induced platelet procoagulant activity as well as systemic thrombin levels in patients undergoing PCI.

Intravascular ultrasound imaging in acute aortic dissection

OBJECTIVES This study was performed to determine the potential of intravascular ultrasound in the detection and delineation of aortic dissection. BACKGROUND Intravascular ultrasound is a new technique capable of displaying real-time cross-sectional images of arterial vasculature. Its clinical use has been explored mostly in coronary and peripheral arterial circulation. METHODS Intravascular ultrasound imaging of the aorta was performed using a 20-MHz ultrasound catheter in 28 patients with suspected aortic dissection. All patients underwent contrast angiography; 7 had computed tomography; and 22 had transesophageal echocardiography. RESULTS Imaging of the aorta from the root level to its bifurcation was performed in all patients in an average of 10 min. No complications occurred. Dissection was present in 23 patients and absent in 5. In the patients without dissection, intravascular ultrasound revealed normal aortic anatomy. In all 23 patients with dissection, intravascular ultrasound demonstrated the intimal flap and true and false lumena. The longitudinal and circumferential extent of aortic dissection, contents of the false lumen, involvement of branch vessels and the presence of intramural hematoma in the aortic wall could also be identified. In cases where aortography could not define the distal extent of the dissection, intravascular ultrasound did. CONCLUSIONS Our experience in this series of patients with aortic dissection indicates that intravascular ultrasound could be valuable in the identification and categorization of aortic dissection and in the description of associated pathologic changes that may be clinically important. It can be performed rapidly and safely and could serve as an alternative or adjunct diagnostic procedure in patients with aortic dissection.

The pulmonary artery pulsatility index identifies severe right ventricular dysfunction in acute inferior myocardial infarction.

Background: Right ventricular dysfunction (RVD) is a major cause of morbidity and mortality in the setting of acute inferior wall myocardial infarction (IWMI), and early detection may improve clinical outcomes. We defined a novel hemodynamic index, the pulmonary artery pulsatility index (PAPi), and explored whether the PAPi correlates with severe RVD in acute IWMI.

Real‐Time Intracardiac Two‐Dimensional Echocardiography: An Experimental Study of In Vivo Feasibility, Imaging Planes, and Echocardiographic Anatomy

The traditional transthoracic and transesophageal echocardiographic examination have proven to be useful imaging tools for studying cardiac morphology, pathology, and function. Recently, catheter‐based ultrasound transducers have been available for intravascular ultrasonic imaging. We supposed that echocardiographic examination performed from within the heart itself can provide useful information about cardiac structure and function, especially in settings where transthoracic or transesophageal echocardiography may be technically difficult to perform or poorly tolerated by the patient. To explore this concept, we performed intracardiac echocardiography in vivo in 22 dogs using both 5‐MHz and 20‐MHz transducers. High‐quality images were obtained in all animals. Using the higher frequency transducer, detailed images with only a limited depth of field were obtained. With the 5‐MHz transducer, a comprehensive cardiac examination was feasible from within the right atrium and inferior vena cava. We were able to visualize the great vessels, all cardiac valves, and cardiac chambers in a multitude of imaging planes. Alterations in ventricular function were instantly recognized. Color Doppler capabilities allowed visualization of flow abnormalities as well. We conclude that intracardiac echocardiography is feasible and could be potentially useful in certain clinical situations. With further research and development, this technique may have an important clinical impact in cardiac therapy and diagnosis.

Intracardiac Echocardiographic Imaging of Cardiac Abnormalities, Ischemic Myocardial Dysfunction, and Myocardial Perfusion: Studies With a 10 MHz Ultrasound Catheter

Intracardiac echocardiography (ICE), an echocardiographic examination from within the heart itself, has been proposed as a new modality for cardiac imaging. A major shortcoming has been the limited depth of field provided by previously available devices. We used 10 MHz catheters for ICE to determine if this lower frequency would allow for greater display of cardiac anatomy. We performed ICE in seven animals; myocardial ischemia was induced in three. With the imaging catheter in the right atrium, all four cardiac chambers and valves could be imaged. Advancing the transducer into the right ventricle allowed for short-axis images of the left ventricle. Coronary perfusion territories and segmental wall motion abnormalities could be observed. We then performed ICE in six patients by advancing the catheter into the right side of the heart percutaneously. Structures of the right side of the heart, the mitral valve, aortic valve, left atrium, and portions of the left ventricle, were visualized. Congenital and acquired abnormalities could be identified. There were no complications. We conclude that ICE with 10F, 10 MHz ultrasound catheters allows for expanded imaging capabilities because of the increased depth of field. With this imaging modality, congenital and acquired abnormalities as well as myocardial ischemia can be detected.

Intracardiac Two-dimensional Echocardiography in Patients with Pericardial Effusion and Cardiac Tamponade

The utility of intracardiac two-dimensional echocardiography in the identification of pericardial effusion was assessed in five patients with pericardial effusion and cardiac tamponade. A 20 MHz, mechanically rotating ultrasound catheter was used for intracardiac imaging. In all five patients, intracardiac echocardiography yielded high resolution of images of the right atrial cavity, the right atrial wall, and the pericardial effusion. In two patients, right atrial collapse could be identified during real-time imaging. Although the entire right atrial cavity and the pericardial effusion could not be displayed in a single imaging field because of the limited depth of field associated with the 20 MHz catheter, manipulation of the catheter allowed visualization of the pericardial effusion and the parietal pericardium in each patient. The effusion was seen to surround the superior vena cava, as well, in all patients. After pericardiocentesis, the reduction in the size of the effusion and increase in the right atrial cavity size could be recognized by intracardiac echocardiography. The introduction and manipulation of the ultrasound catheter was easily performed without any complications. This experience presents one clinical application for intracardiac echocardiography and indicates its potential value in the invasive cardiac laboratory.