Biomedical subjects
Publications and source records attributed to K Chandrasekaran.
Reduced brain glucose utilization in early stages of Alzheimer disease, as measured with in vivo positron emission tomography, reflects potentially reversible down-regulation of gene expression for oxidative phosphorylation within neuronal mitochondria. Such down-regulation may occur when neuronal energy demand is first reduced by synaptic dysfunction or loss.
The aim of this study was to evaluate the risk of performing cardiac catheterization or intraaortic balloon pump placement in patients with transesophageal echocardiographically detected atherosclerotic aortic debris. Cardiac catheterization was performed in 70 patients with atherosclerotic aortic debris (in 11 via the brachial approach and in 59 via the femoral approach) and in 71 control patients. An embolic event occurred in 10 (17%) of 59 patients with atherosclerotic aortic debris after femoral catheterization compared to 2 (3%) of 71 control patients without atherosclerotic aortic debris (p = 0.01). None of the 11 patients with atherosclerotic aortic debris who underwent brachial catheterization had an embolic event. An intraaortic balloon pump was placed in 10 patients with atherosclerotic aortic debris and in 12 control patients. An embolic event related to placement of the intraaortic balloon pump occurred in 5 (50%) of 10 patients with atherosclerotic aortic debris; no control patient had an embolic event (p = 0.02). Patients with mobile atherosclerotic aortic debris were at the highest risk for catheter-related embolism. The strongest clinical predictors of atherosclerotic aortic debris were advanced age and peripheral vascular disease. Transesophageal echocardiographic recognition of atherosclerotic aortic debris identifies patients at high risk of stroke or peripheral embolism after cardiac catheterization or intraaortic balloon pump placement. If the aortic debris is mobile, the risk is particularly high. When atherosclerotic aortic debris is detected, especially if the debris is mobile, substituting brachial for femoral catheterization and avoiding placement of an intraaortic balloon pump may reduce the risk of embolism.
Localized pericardial effusion leading to cardiac tamponade is seen occasionally in patients after cardiac surgery. This condition may be difficult to diagnose clinically because of unusual presenting symptoms and absence of conventional signs of cardiac tamponade. A case of localized pericardial effusion with presenting symptoms of fever and increasing fatigue is described in this study. The definitive diagnosis was made using transesophageal echocardiography. Surgical drainage of localized effusion resulted in prompt hemodynamic and symptomatic improvement.
Thrombosis of upper extremity veins and superior vena cava (SVC) can occur in patients with indwelling central venous catheters. Contrary to earlier reports, pulmonary embolism (PE) can result from these thrombi, especially when they are attached to catheters (sleeve thrombi) in contrast to venous wall (mural thrombi). Removal of catheters may be required when sepsis occurs or to reduce risk of sepsis when lines have been left in for several days. We describe two patients with thrombi in SVC related to central venous catheters in whom transesophageal echocardiography (TEE) was performed during catheter removal to monitor for thrombus dislodgement. TEE may have a role in showing thrombus dislodgement and embolization during removal of venous catheters complicated by SVC thrombi. Direct visualization of thrombus dislodgement may aid in early diagnosis of PE because signs and symptoms of PE are often missed or mistaken for underlying cardiopulmonary disease. TEE may also play a role in implementing appropriate treatment in patients with PE who show right ventricular strain.
UNLABELLED: Smaller intra-aortic balloons (IAB) may minimize peripheral vascular complications. To determine the influence of different IAB volumes on cardiac performance, we studied 20 hemodynamically stable patients on IAB counterpulsation. Variables were measured with either a 40cc or 32cc IAB displacement, at an assist ratio of 1:1 or 1:8: Heart rate, Ao and PA pressures, and Fick cardiac output. By echo-Doppler, the velocity time integral (VTI) across the LV outflow tract, a measure of stroke volume was also calculated. The mean age was 60 yr (range 18-77), height 5'6" (5'2"-5'11"), and body surface area 1.9M2 (1.5-2.3). Results presented as mean values were: [table: see text] *P < 0.005 1:1 vs 1:8 for both 40 and 32cc IAB. CONCLUSION: IAB pumping at 1:1 with either 40 cc or 32 cc volume displacement yields similar degrees of improvement in cardiac performance. A larger cohort is required to determine if smaller balloons may decrease complications without compromising efficacy.
OBJECTIVES: This study was designed to define the frequency and explanation of false negative diagnosis of aortic dissection by aortography and transesophageal echocardiography. BACKGROUND: Aortography and transesophageal echocardiography have been widely utilized to diagnose aortic dissection. Previous reports have not fully addressed the reasons why these studies yield false negative results in a large number of patients with aortic dissection. METHODS: Sixty-five consecutive patients with aortic dissection underwent aortography and transesophageal echocardiography. Diagnosis of aortic dissection was confirmed at operation or by computed tomography in all patients. RESULTS: Biplane transesophageal echocardiograms yielded false negative results in two patients (sensitivity 97% [63 of 65]). Both patients had well localized DeBakey type II aortic dissection. The diagnosis was probably missed because of image interference from the air-filled trachea and mainstem bronchi. In both patients, the dissection was readily identified by aortography. Aortograms yielded false negative results in 15 patients (sensitivity 77% [50 of 65]); the aortic dissection was type I in 7 patients, type II in 1 and type III in 7. The dissection in all 15 patients was readily identified by transesophageal echocardiography. The missed diagnosis was probably due to a completely thrombosed false lumen or intramural hematoma with noncommunicating dissection in 13 patients and to a large ascending aortic aneurysm with nearly equal flow on both sides of the intimal flap in 2. In no patient was the diagnosis missed by both aortography and transesophageal echocardiography. CONCLUSION: Transesophageal echocardiography is an excellent screening tool for aortic dissection. However, it may miss small type II aortic dissections localized to the upper portion of the ascending aorta because of image interference from the air-filled trachea. An intramural hematoma cannot be easily visualized by aortography, and this lesion is the principal reason for false negative aortographic findings.
STUDY OBJECTIVE: To determine whether standard clinical and transthoracic echocardiographic criteria considered to be suggestive of the presence of endocarditis-associated paravalvular abscess are predictive of which patients would benefit from reliable but invasive transesophageal echocardiographic investigations for abscess. DESIGN: Retrospective chart review. SETTING: A 630-bed university hospital. PATIENTS: Forty-eight patients with 51 episodes of definite endocarditis and 24 paravalvular abscesses. MEASUREMENTS AND RESULTS: A comparison of abscess and nonabscess populations revealed that clinical parameters (patient demographics, valvular involvement, presence of a prosthesis, infection with a virulent organism, pericarditis, persistent fever, persistent bacteremia, congestive heart failure, history of intravenous drug use, embolization) and transthoracic echocardiographic parameters were insensitive predictors of the presence of abscess. The only statistically significant correlate was the presence of previously undetected atrioventricular or bundle branch block. Paravalvular abscesses were common in our population and were associated with increased mortality. Improved survival correlated with the absence of mitral valve involvement and the absence of moderate-to-severe congestive heart failure. CONCLUSIONS: Given the accuracy and safety of transesophageal echocardiography and the unreliability of clinical and transthoracic echocardiographic criteria, we recommend that transesophageal echocardiography be considered in all endocarditis patients with previously unrecognized conduction disturbances, aortic or prosthetic valve involvement, or both, or indications for valve replacement, or all of the foregoing.
Arterial embolization from thrombolytic therapy for acute myocardial infarction is rare. We report two cases of spontaneous arterial embolization following the use of tissue plasminogen activator for acute myocardial infarction. Transesophageal echocardiography was able to identify the source of embolism as mobile atherosclerotic debris within the thoracic aorta. This information was of value in the management of these patients, in that femoral catheterization which could have precipitated further embolization was avoided.
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Brains from 5 patients with Alzheimer's disease (AD) showed a 50%-65% decrease in mRNA levels of the mitochondrial-encoded cytochrome oxidase (COX, a marker of oxidative metabolism) subunits I and III in the middle temporal association neocortex, but not in the primary motor cortex, as compared to 5 control brains. The amount of mitochondrial-encoded 12S rRNA was not altered, nor was the amount of nuclear-encoded lactate dehydrogenase B mRNA (a marker of glycolytic metabolism). These data suggest that the decrease in COX I and III subunits mRNA in affected brain regions may contribute to reduced brain oxidative metabolism in AD.
Previous studies assessing the value of transthoracic echocardiography (TTE) in blunt chest trauma are limited because patients with severe chest wall injury often have suboptimal echocardiographic findings. Transesophageal echocardiography (TEE) can provide high quality images when the transthoracic image quality is poor. To provide complete echocardiographic assessment of cardiac structure and function we prospectively performed TTE in 105 patients with severe blunt chest trauma and TEE in 20 of the 105 patients (19%) whose TTE examination results were suboptimal. Myocardial contusion was diagnosed in 31 patients (30%), 22 by TTE and nine by TEE. Cardiac complications developed in 8 of 31 patients (26%) with myocardial contusion compared with 2 of 74 patients (3%) with normal echocardiographic findings (p = 0.001). Cardiac complications required treatment in only four patients. Echocardiography was of value in detecting severe right ventricular dysfunction as the cause of hypotension in two patients with suspected cardiac tamponade. Four patients with myocardial contusion died compared with two patients with normal echocardiographic findings (p = NS). No death was related to the cardiac status. In addition, TEE detected aortic injury in five patients, four with focal intimal tears and one with an aortic transection. We conclude that myocardial contusion is common following blunt chest trauma, rarely requires treatment, and is associated with a favorable prognosis. Only patients who develop cardiac complications benefit from echocardiography. Transesophageal echocardiography is of value when the TTE examination results are suboptimal and when aortic injury is suspected.
Acute paraplegia from an aortic occlusion or dissection is a surgical emergency. Prompt recognition and treatment may mitigate irreversible spinal cord injury. Aortography is commonly used when an aortic lesion is suspected as the cause of acute paraplegia. Transesophageal echocardiography is becoming increasingly used for the evaluation of aorta, diagnosing aortic dissection promptly at the bedside, and was able to define the cause of the spinal cord ischemia.
The objectives of this study were to evaluate: (1) the feasibility of generating three-dimensional (3-D) ultrasound (US) volumetric images of arterial segments from intravascular (IV) US images by retaining full range of gray levels; (2) the feasibility of volumetric quantitation of various arterial wall pathology from the 3-D volume US images of arterial segments. IVUS provides morphologic details of arterial wall diseases. This is seen as variation in gray levels. However, when a 3-D US image is generated currently, the full range of gray levels is not utilized. This limits optimal assessment of arterial wall pathology. Sequential cross-sectional IVUS images from 11 arterial segments consisting of various pathology were obtained in vitro by calibrated withdrawal of an IVUS catheter. These images were digitized by an 8 bit digitizer to retain full 256 gray levels of brightness. 3-D volume generation was carried out using "ANALYZE" software. After the IVUS imaging, arterial segments were sectioned transversely in a 0.3-0.4 mm cross section and stained with hematoxylin, eosin and elastin. Geometrical measurements and gross morphological changes of the arterial segments were noted and correlated with the corresponding section of the image from the three-dimensional volume. Arterial wall pathology, its extent and its effect on lumen geometry were easily appreciated in multiple tomographic sections of a 3-D volume image. Similarly, arterial wall pathology was easily quantitated from 3-D volume. The above assessments were only feasible by retaining full range of gray levels in the 3-D volume image. This study indicates that (1) it is feasible to generate a 3-D US volume image by retaining full range of gray levels from IVUS images, (2) retaining full range of gray levels allows optimal assessment of arterial wall pathology and its extent in 3-D volume, and (3) IVUS allows quantitation of arterial wall pathology, and thereby one can assess the effect of intervention.
Mortality is high in unrecognized pulmonary embolism (PE), but the diagnosis is difficult to establish, especially in patients with coexisting cardiopulmonary disorders. We describe a group of 14 patients with pulmonary thromboemboli in whom transesophageal echocardiography (TEE) performed for coexisting cardiopulmonary conditions established the clinical diagnosis of PE not suspected prior to TEE. The patients had initial clinical diagnoses of heart failure (eight patients), cardiogenic shock (two patients), atrial septal defect (two patients), aortic dissection (one patient), and pneumonia (one patient). Thirteen patients had risk factors for PE. Transthoracic echocardiography (TTE) demonstrated right heart strain in eight patients but did not visualize PE in any of the patients. The TEE diagnosis of occult central pulmonary artery thromboembolism changed treatment in all 14 patients. Ten of the 14 patients were successfully discharged from the hospital. We conclude that occult central pulmonary artery thromboemboli are not uncommon in patients presenting with acute cardiopulmonary disorders and the presence of risk factors for PE and right heart strain on TTE should alert the physician to suspect PE. If and when TEE is performed in patients with acute cardiopulmonary disorders with risk factors for PE and right heart strain, the physician should evaluate the main pulmonary artery and its branches for central pulmonary artery thromboemboli.
Contrast echocardiography produced by peripheral injection of agitated saline solution is widely used for detecting intracardiac and intrathoracic extracardiac shunts, like pulmonary arteriovenous malformation (PAVM). Currently, localization of PAVM requires pulmonary angiography even after detection by computed tomography of the chest. Pulsed Doppler along with contrast echocardiography of the pulmonary veins performed during transesophageal echocardiography may aid in the localization of PAVM and in its diagnosis.
The application of intravascular ultrasound (IVUS) in diagnosing pulmonary artery atherosclerosis is described. To the best of our knowledge, this is the first description of the use of this technique in the recognition of pulmonary atherosclerosis. We describe a patient with long-standing primary pulmonary hypertension with evidence of pulmonary artery calcification seen on a chest x-ray film. The IVUS imaging of the pulmonary arteries identified intimal disruption with complex atherosclerosis. Thus, IVUS can be a useful tool in the diagnosis of pulmonary artery atherosclerosis.
We investigated the usefulness of reverse transcriptase-polymerase chain reaction (RT-PCR) to quantify glucose transporter 1 (GLUT1) mRNA in cerebral microvessels. The technique was validated using an in vitro-transcribed RNA fragment (riboprobe) of partial 3' noncoding sequence of rat brain GLUT1 gene. A known amount of the riboprobe was reverse-transcribed to cDNA (target DNA). PCR primers were made to amplify a 292-bp fragment of the target DNA. The 5' primer was end labeled with 32P. An oligonucleotide of 100 bp containing the same sequences as the first 30 and the last 70 bases of the 292-bp fragment of the target DNA was synthesized and used as competitive DNA. The target DNA was coamplified with increasing amounts of competitive DNA using the same two primers. The ratio of radioactivity between amplified products of the target DNA (292-bp fragment) and the competitive DNA (100-bp fragment) was determined quantitatively after separation by gel electrophoresis and radioactivity counting. This method gave an accurate estimation of the amount of the riboprobe in the reaction and a 2- to 5-fold change in the amounts could be detected. By this method, the mean amount of GLUT1 mRNA from purified rat brain microvessels was estimated to be 1.5 +/- 0.1 x 10(-6) ng/ng total RNA. This value was about 10-fold higher than that in rat cell line PC12.