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Navin C. Nanda

Publications and source records attributed to Navin C. Nanda.

At least 19 recordsLinked to original sources
PubMed1999

Real-Time Contrast Echo Assessment of Myocardial Perfusion at Low Emission Power: First Experimental and Clinical Results Using Power Pulse Inversion Imaging.

Power pulse inversion (PPI) has been developed for echocontrast specific imaging in order to reduce destruction of microbubbles. The purpose of this study was to evaluate PPI for real-time contrast echocardiography. Therefore, in vitro studies in a physiological flow-phantom and clinical examinations in patients with coronary artery disease were performed. The in vitro rersults of this study indicate that PPI allows real-time imaging at low emission power and is almost nondestructive to contrast microbubbles of Definity. At this low emission power a strong linear relationship between the dosage of the contrast agent and the resulting PPI signal intensity was found (R = 0.998, p < 0.001). In the clinical examinations real-time imaging using low mechanical index PPI resulted in strong myocardial signals and a complete filling of the cavities indicating absence of bubble destruction. Most striking was the ability of PPI to display myocardial thickening and wall motion simultaneously with the assessment of myocardial contrast replenishment following ultrasound induced bubble destruction by high power frames. We conclude that PPI allows nondestructive contrast imaging both in experimental and clinical settings. Therefore, real-time imaging of myocardial perfusion and real-time assessment of contrast replenishment following ultrasound induced destruction of microbubbles is feasible. Moreover, PPI allows simultaneous assessment of perfusion and myocardial function.

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PubMed1999

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Journal Article↗
PubMed1999

Lambl's Excrescences Involving the Pulmonary Valve Detected by Transesophageal Echocardiography.

We report the first case of echocardiographically detected Lambl's excrescences on the pulmonary valve in a 72-year-old man who was referred for transesophageal echocardiography as a part of an evaluation for ischemic stroke. A total of four excrescences were noted on the arterial aspect of the pulmonary valve; two of them were on the anterior cusp, one was on the left cusp, and one was on the right cusp. The excrescence on the left cusp was the largest, measuring 5 mm in length. These valvular strands (Lambl's excrescences) represented an incidental finding and were not associated with any disease process.

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PubMed1999

Transesophageal Echocardiographic Diagnosis of Proximal Coronary Artery Stenosis in Patients with Ischemic Stroke.

Atherosclerosis is the leading cause of death worldwide. It encompasses several clinical entities, including coronary artery disease and cerebrovascular disease. Because the underlying pathophysiological mechanism is the same, coronary artery disease and cerebrovascular disease frequently coexist. Transesophageal echocardiography (TEE) is routinely done in patients with ischemic stroke to exclude possible cardiac sources of cerebral embolism. Since the introduction of multiplane transesophageal transducers, it has become easier to visualize the proximal coronary arteries during transesophageal examinations. We report three cases in which routine TEE for ischemic stroke revealed significant coronary artery disease that was not previously suspected. In one patient, the stroke was so severe that further evaluation of the coronary artery disease was not deemed useful. The other two patients underwent coronary angiography based on the echocardiographic findings, confirming the lesions noted on the echocardiogram. Subsequently, both patients were successfully revascularized: one by percutaneous transluminal coronary angioplasty and the other by coronary artery bypass graft surgery. We conclude that the examination of coronary arteries during routine TEE for ischemic stroke may become a useful screening tool for the detection of coexisting, asymptomatic, significant proximal coronary artery disease.

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PubMed1999

Transesophageal Echocardiographic Examination of Left Subclavian Artery Branches.

This preliminary study demonstrates the feasibility of examining the proximal segments of the branches of the left subclavian artery during probe withdrawal toward the end of a routine transesophageal echocardiographic study. The branches identified most commonly were the vertebral and the internal mammary arteries.

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PubMed1999

Lambl's Excrescences (Valvular Strands).

We review the literature on Lambl's excrescences (valvular strands). With the widespread use of cardiac imaging modalities, most importantly, with transesophageal echocardiography, abnormal valvular structures are frequently identified on both native and prosthetic heart valves. However, there is no consensus in the literature on the correct terminology of these structures. The relationship between valvular strands (the so-called Lambl's excrescences) and papillary fibroelastomas has not been well established. In this review, we attempt to summarize the available echocardiographic descriptors and the gross macroscopic and histological features of Lambl's excrescences (valvular strands). In addition, we review the etiology, pathogenesis, and clinical implications of these cardiac excrescences. Also, we describe features that help to distinguish between Lambl's excrescences and papillary fibroelastomas. Because valvular strands (Lambl's excrescences) have been implicated in systemic thromboembolism, we also review the available management principles for patients with valvular strands; unfortunately, no specific therapeutic guidelines can be proposed at the present time.

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PubMed1998

Analysis of the Proximal Orifice Flowfield Under Pulsatile Flow Conditions and Confining Wall Geometry: Implications in Valvular Regurgitation.

Hemodynamic studies of regurgitant lesions in the heart focus on identifying a reliable noninvasive method of volumetric flow calculation. In these studies the influence of blood viscosity to the flowfield under pulsatile flow conditions and constraining wall geometry has not been examined in detail. Pulsatile flow studies in straight tubes have shown that viscous effects significantly influence the periodic flowfield, especially near the wall. The purpose of this study is to investigate the significance of transient effects in the flowfield proximal to a lesion under constraining wall geometry. The proximal flowfield was analyzed with computational fluid dynamics (CFD) computer simulations and color flow Doppler mapping (CFM). Three different stroke volumes and regurgitant waveforms were investigated for upstream wall orientations that varied from -64 degrees to +64 degrees (measured from the orifice plane). Results showed that for each upstream wall orientation, a single instantaneously normalized centerline velocity distribution characterized the flowfield throughout the cycle. The centerline distributions were in phase with the pressure gradient and almost identical to the corresponding steady-state distributions. Minor deviations were observed near the wall, where viscous effects were predominant. Transient flow effects such as blunt profiles and pressure velocity phase shifts, which were observed in straight circular tubes, were not observed in regurgitant orifice flowfields. This is true even under severe confinement conditions.

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PubMed1998

Transesophageal Echocardiographic Diagnosis of Right-Sided Aortic Arch.

We present the transesophageal echocardiographic findings in two adult patients with right-sided aortic arch: one without dissection and the other with traumatic aortic injury (dissection). In both patients, the branching pattern was the left common carotid artery and then the right common carotid artery, followed by the right and left subclavian arteries. The technique for the diagnosis of this anomaly and the identification of adjacent vascular structures using contrast echocardiography is described. Three-dimensional reconstruction of the aortic arch also was performed in both patients.

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PubMed1998

Improvement in Endocardial Border Delineation Using Tissue Harmonic Imaging.

BACKGROUND AND METHODS: For years, tissue has been assumed to be a linear medium in diagnostic ultrasound applications; thus, no backscattered signals in the second harmonic band are expected in harmonic imaging without the injection of a contrast agent. However, it has been shown that a useful tissue image is formed even without a contrast agent. The aim of this study was to evaluate whether this tissue harmonic image provided improved visualization of endocardial borders. Fifty-six adult patients with various heart diseases were investigated using conventional two-dimensional echocardiography and tissue harmonic imaging. In 30 of these patients, the left ventricular endocardial borders were well defined in the standard parasternal and apical views using conventional two-dimensional echocardiography. In the remaining 26 patients, delineation of endocardial borders was not possible in at least two segments. The equipment used was an ATL HDI-3000 diagnostic system equipped with harmonic imaging. RESULTS: In all 56 patients, the myocardium and valves could be imaged with tissue harmonic imaging. Harmonic recordings were sharper and contained fewer clutter artifacts than conventional recordings. Most striking was the enhancement of left ventricular endocardial borders. In the 26 patients with incomplete delineation of left ventricular endocardial borders, wall motion could be evaluated in 290 of 312 (93%) segments with tissue harmonic imaging compared with only 168 of 312 (54%) segments with conventional echocardiography (P < 0.001). CONCLUSIONS: Tissue harmonic imaging improves image quality and can be used to enhance the definition of left ventricular endocardial borders. These findings can be explained by the nonlinear propagation of ultrasound within the tissue, which results in distortion of the transmitted signal and, thus, harmonic generation.

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