Intracardiac Ultrasound Imaging Research Articles

Intracardiac ultrasound detection of right ventricular infarction in a canine model

Our objective was to demonstrate that right ventricular (RV) infarction could be demonstrated by intracardiac ultrasonography in a canine model. RV infarction is a common and important clinical condition in patients with myocardial infarction. Traditional methods for diagnosing RV infarction have limitations. Intracardiac echocardiography, in which an ultrasonic transducer on the tip of a catheter is placed intravenously into the RV chamber, should allow detection of RV infarction. Nine closed-chest dogs were studied. The animals were instrumented with a 10 MHz ultrasound catheter placed into the right ventricle. The right coronary artery was occluded with a balloon angioplasty catheter for 20 minutes and subsequently embolized with elemental mercury. Intracardiac ultrasound images were obtained at baseline, during balloon occlusion, and during embolization. RV cross-sectional end-diastolic and end-systolic areas were calculated and fractional area change were calculated; RV wall motion abnormalities were also evaluated. The interventricular septal thickening was also calculated. The 10 MHz intracardiac ultrasound catheter allowed visualization of much of the RV chamber and interventricular septum. The RV cross-sectional area increased with mercury embolization, which was also associated with regional wall motion abnormalities. RV end-systolic area was 1.6 cm 2 and end-diastolic area 3.9 cm 2 at baseline; these increased to 4.8 cm 2 and 6.5 cm 2 after embolization ( p <0.05). Interventricular septal thickening remained unchanged. The echocardiographic features of RV infarction, which include RV dilation and RV regional wall motion abnormalities, could be demonstrated in a canine infarct model with a 10 MHz intracardiac ultrasound catheter. (J Am Soc Echocardiogr 1997;10:352-6.)

Percutaneous transvenous intracardiac ultrasound imaging in dogs: a new approach to monitor left ventricular function.

To evaluate the feasibility and ability of percutaneous transvenous intracardiac echocardiography (ICE) to image the left ventricle (LV) and monitor its function from the right ventricular (RV) cavity. A 10 MHz catheter was advanced into the RV from the jugular vein and positioned along the septum at the LV papillary muscle level in five dogs. The catheter was manipulated until a stable catheter position along the septum, which provided on-axis images of LV, was obtained. Different states of LV size and systolic function (n = 80) were created with dobutamine or esmolol, both in the presence and absence of coronary stenoses. LV stroke area (cm2) obtained by ICE was measured at the mid-ventricular level and compared with stroke volume (cm3) obtained simultaneously with a transaortic flow probe. LV end diastolic, end systolic, and stroke areas obtained by ICE were also compared with those obtained by short-axis epicardial echocardiography. In 96% of the stages, short axis images of the LV could be obtained and measured by ICE. LV end diastolic, end systolic, and stroke areas measured by ICE were not significantly different from epicardial echocardiographic values. Stroke area correlated with stroke volume in each dog (mean correlation coefficient 0.79 (SEE 0.19) cm2) (P < 0.001). Percutaneous intracardiac ultrasound imaging allows monitoring of LV function from the RV with an accuracy comparable to a short-axis epicardial echocardiogram. The present device can be used in closed chest experimental studies. With the development of lower frequency devices, this technique may be valuable for continuous monitoring of LV function in patients in the intensive care unit or operating room.

Use of a new semi-automated method to determine regional left ventricular wall thickening from intracardiac ultrasound images

Use of a new semi-automated method to determine regional left ventricular wall thickening from intracardiac ultrasound images

Intracardiac Ultrasound Imaging During Transseptal Catheterization

The purpose of this study was to assess the feasibility of using small 12.5- or 20-MHz intracardiac ultrasound catheters to image the fossa ovalis and guide transseptal catheterization. The study was performed in three phases. First, in vitro imaging of human autopsy hearts was performed to define the intracardiac ultrasound appearance of the fossa ovalis and transseptal apparatus. Subsequently, the optimum approach for imaging the fossa ovalis in vivo was established in 30 patients. Finally, intracardiac ultrasound imaging was performed during transseptal catheterization of 10 patients undergoing percutaneous mitral commissurotomy. Intracardiac ultrasound imaging was performed with a 12.5- or 20-MHz single-element mechanical device in which a central imaging core is rotated within a 6F polyethylene sheath. In both in vitro and in vivo studies, the fossa ovalis was easily identifiable as a thin membranous region surrounded by the thicker muscular portion of the interatrial septum. Initial in vivo studies established venous access by the femoral route to be superior to the internal jugular approach for catheter introduction. Studies performed during transseptal catheterization established the utility of using the fluoroscopic image of the catheter adjacent to the fossa ovalis to generate a guiding shot for positioning the transseptal apparatus. In addition, distention of the fossa prior to needle perforation could be demonstrated. However, since it was often difficult to track the tip of the needle, actual puncture of the fossa was rarely demonstrated. Intravascular ultrasound imaging can precisely locate the fossa ovalis in virtually all subjects. It therefore may assist transseptal catheterization.

1002-84 Three-Dimensional Reconstruction of Atrial Septal Defect from Intracardiac Ultrasound Imaging: Dynamic Shape Change of the Defect in Cardiac Cycle

Currently available transcatheter techniques closing atrial septal defect (ASD) are only suitable for small to moderate sized ones. Assessment of the shape and size of ASD as well as their changes in cardiac cycle may be important when transcatheter closure is applied to larger sized defects. We have developed a three-dimensional reconstruction (3DR) of ASD from images obtained with intracardiac ultrasound (ICUS). Preliminary study disclosed inadequate image quality of ICUS probes with 15 MHz or higher transmission frequency for ASD assessment. Newly developed 10 MHz, 6 Fr. reusable rotating probes was used in this study. ICUS images were obtained from 4 patients with secundum ASD; age 2.3 to 12 years (median 6.5), weight 11.5 to 44 kg (median 19). A 7 Fr. guiding long sheath was introduced from the femoral vein and placed in the superior vena cava. A 6 Fr. ICUS probe was introduced into the long sheath and ECG gated serial ICUS images were obtained through it. Images were recorded on videotape with 1 mm step manual pullback to the inferior vena cava. The probe was stable in cardiac cycle and the 3DR was achieved with high resolution images. En face view of ASD could be obtained from the both sides of the septum in all patients. Cross-sectional area of the defect (2.47 ± 0.15 cm 2 ) changed significantly in cardiac cycle (4 to 58% larger in systole than in diastole). The largest size of the defect in the cardiac cycle was in endsystole coincided with peak Doppler left to right shunt across the defect. This dynamic shape change of the ASD may have necessitated various conventional transcatheter ASD closure devices double in size to the actual defect. We concluded that 3DR of ASD from ICUS images can provide important information for the development of new transcatheter ASD closure devices.

Intracardiac ultrasound determination of left ventricular volumes: In vitro and in vivo validation

Objectives. This study was designed to assess the feasibility of calculating left ventricular volumes using intracardiac ultrasound.Background. Previous studies have validated transthoracic echocardiographic determinations of left ventricular volumes and have indicated the superiority of Simpson rule reconstruction algorithms. The feasibility of imaging the left ventricle with intracardiac ultrasound has also been demonstrated.Methods. The determination of left ventricular volumes with Simpson rule reconstruction of intracardiac ultrasound images was evaluated in two phases. In vitro validation was performed in 29 animal hearts preserved in either a nondistended or distended state. Latex cast volumes were the reference standard. In vivo studies used 14 pigs, and compared intracardiac ultrasound volumes and ejection fraction with single-plane contrast angiographic values. A 12.5-MHz device was used to record short-axis images at 0.5-cm intervals. These were used to reconstruct the ventricle as a stack of cylindric elements using all imaged levels as well as sections recorded every 1 and 2 cm and at a single midventricular level.Results. In the in vitro hearts, when all recorded sections were used, there was excellent agreement between intracardiac ultrasound and latex cast volumes (intracardiac ultrasound volume = 0.89 latex cast volume + 2.22, r = 0.95; intracardiac ultrasound volume = 0.97 latex cast volume + 0.91, r = 0.99) for nondistended and distended hearts, respectively. In vivo, there was again close correspondence between ultrasound and angiographic volumes (intracardiac ultrasound volume = 1.04 angiographic volume −3.6, r = 0.91). The relation between intracardiac ultrasound and angiographic ejection fraction was fair (intracardiac ultrasound ejection fraction = 1.00 angiographic ejection fraction + 6.85, r = 0.69). Excellent correlations for the volumes were maintained as the number of cross sections was reduced to those recorded every 1 and 2 cm (r = 0.87 to 0.99). With a single midventricular site more variable but generally good correlations were obtained (r = 0.77 to 0.99).Conclusions. The application of Simpson rule reconstruction to short-axis images of the left ventricle obtained with intracardiac ultrasound provides accurate determination of left ventricular volumes in animal hearts. This technique may prove useful in the analysis of left ventricular structure and function.

Utility of in vivo, intracardiac two-dimensional echocardiography in the assessment of myocardial risk area and myocardial dyssynergy during coronary occlusion and reperfusion.

We have previously reported the potential use of intracardiac echocardiography (ICE) in a variety of clinical settings, including detection of pericardial effusion, intracardiac masses, congenital cardiac defects, and during simulated balloon valvuloplasty. The utility of intracardiac ultrasound imaging of the left ventricle (LV) in patients with coronary disease needs to be further explored. We performed this study with the purpose of evaluating risk area and regional wall-motion abnormalities produced by ischemia using ICE. Ten episodes of ischemia were produced by transiently occluding the left anterior descending coronary artery in five dogs. ICE was performed with a modified 5-MHz transesophageal echocardiographic probe placed in the right atrium. Continuous short-axis images of the LV were obtained before, during, and after coronary occlusion. Risk area was defined using myocardial contrast echocardiography. In all cases, ICE provided high resolution images of the LV. Risk area and regional wall-motion abnormalities were readily detected. There was good correlation between the risk area (x) and extent of dyssynergy (y), defined by the equation y = 0.76x + 6.38 (r = 0.80, P less than 0.01). We conclude that ICE provides potentially useful information concerning regional LV dysfunction, and, when combined with myocardial contrast echocardiography, area at risk. This technique may be useful during interventional procedures once a catheter-based ultrasound transducer with adequate depth of field to provide images of the entire LV can be developed.

Intravascular and intracardiac ultrasound imaging: current research and future directions.

Intravascular and intracardiac ultrasound imaging is a newly emerging catheter-based imaging modality with considerable promise. This review article presents the rationale behind attempts at developing intravascular imaging methods, the design features of intravascular instrumentation, the knowledge obtained with in vitro studies, the in vivo experience in humans, and the potential applications of intravascular imaging in arterial atherosclerosis. The feasibility of pulmonary artery imaging and the potential applications of intracardiac echocardiography are discussed. Finally, future directions in intravascular imaging are outlined.

Transvascular and intracardiac two-dimensional echocardiography.

Recent developments in transesophageal and catheter-based ultrasound instrumentation have allowed invasive ultrasound imaging. This experimental study presents a new application of invasive ultrasound, transvascular and intracardiac ultrasound imaging. In six pigs, we introduced a 7-mm, 5-MHz esophageal ultrasound probe into both the abdominal aorta and inferior vena cava and explored the imaging potential of this approach. Transvascular imaging from the aorta allowed visualization of the various cardiac structures, the neural canal and interspaces, and peritoneal anatomy. Advancement of the transducer to the level of the aortic valve or into the left ventricle yielded images of the cardiac valves and chambers. With transvascular imaging from the inferior and superior vena cava, the aorta, neural canal, pancreas, and liver were well visualized. Intracardiac imaging from the inferior venae cavae and various regions of the right heart, the left heart structures could be visualized. This in vivo feasibility study demonstrates the potential application of transducer-tipped catheters for transvascular and intracardiac imaging.

Directions for the use of intracardiac high-frequency ultrasound scanning for monitoring pediatric interventional catheterization procedures.

Intravascular and intracardiac ultrasound imaging using high-frequency ultrasound catheters has a number of potential applications in pediatric cardiology. This article reviews the current difficulties associated with interventional procedures for congenital heart lesions, the feasibility of intravascular ultrasound imaging in children, and its potential applications.

Intravascular and intracardiac ultrasound imaging. An old concept, now on the road to reality.

Intravascular and intracardiac ultrasound imaging. An old concept, now on the road to reality.