Georgeanne Lammertin

Biplane stress echocardiography using a prototype matrix-array transducer.

BACKGROUND Rapid image acquisition after cessation of exercise is essential for accurate stress echocardiography. Recently, a prototype matrix-array transducer has been developed that allows simultaneous acquisition of 2 imaging planes (biplane [BP] imaging). METHODS In all, 19 healthy volunteers underwent 2 separate stress echocardiographic studies. Images were acquired in traditional 2-dimensional or BP format pre-exercise and postexercise. RESULTS Total image acquisition time for 2-dimensional stress echocardiography was 38 +/- 8 seconds versus 29 +/- 8 seconds for BP imaging (P <.05). Heart rates were acquired closer to age-predicted maximum with BP imaging in the apical 3- and 2-chamber and parasternal long- and short-axis views (82%, 75%, 70%, 70% for BP vs 76%, 72%, 68%, 66% for 2-dimensional, respectively). CONCLUSION BP imaging using a recently developed matrix-array probe allows more rapid imaging postexercise, resulting in acquisition of poststress images at higher heart rates without compromising image quality.

Use of Carotid Intima-Media Thickness to Identify Patients With Ischemic Stroke and Transient Ischemic Attack With Low Yield of Cardiovascular Sources of Embolus on Transesophageal Echocardiography

Background and Purpose— Carotid intima-media thickness (CIMT) is associated with systemic atherosclerosis and cardioembolic conditions and predicts the risk of recurrent strokes. We sought to establish the relationship between CIMT and cardiovascular sources of embolus (CSE) on transesophageal echocardiography (TEE) and hypothesized that a noninvasive strategy of CIMT assessment and transthoracic echocardiography bubble study would identify patients with ischemic stroke or transient ischemic attack in whom TEE would provide little incremental diagnostic yield. Methods— In 180 patients with ischemic stroke or transient ischemic attack of undetermined origin referred for TEE, we prospectively performed CIMT measurement/plaque screen (Phase 1, n=96) or CIMT measurement/plaque screen and transthoracic echocardiography bubble study (Phase 2, n=84) before TEE. Phase 1 results were used to construct receiver operating characteristic curves to demonstrate the ability of CIMT to detect CSE on TEE and to identify the optimal CIMT cutoff value for prospective strategy testing (Phase 2). Results— In Phase 1, CIMT was found to correlate with TEE markers of aortic atherosclerosis, including complex aortic plaques, and combined CSE. The optimal CIMT cutoff for detection of CSE on TEE was 0.78 mm. In Phase 2, a positive noninvasive strategy test (CIMT ≥0.78 mm, +carotid plaque, and/or a positive transthoracic echocardiography bubble study) was present in 61%. The prevalence of CSE on TEE was significantly higher among those with a positive compared with a negative noninvasive strategy test (65% versus 9%, P<0.001), and this strategy had a sensitivity of 92% and a negative predictive value of 91% for the detection of any CSE on TEE. Conclusion— In patients with stroke or transient ischemic attack of undetermined origin, a noninvasive strategy of CIMT assessment/plaque screen and transthoracic echocardiography bubble study can identify patients in whom further invasive evaluation with TEE will be of low diagnostic yield.

Semi-automated analysis of dynamic changes in myocardial contrast from real-time three-dimensional echocardiographic images as a basis for volumetric quantification of myocardial perfusion

AIMS Despite the potential of real-time three-dimensional (3D) echocardiography (RT3DE) to assess myocardial perfusion, there is no quantification method available for perfusion analysis from RT3DE images. Such method would require 3D regions of interest (ROI) to be defined and adjusted frame-by-frame to compensate for cardiac translation and deformation. Our aims were to develop and test a technique for automated identification of 3D myocardial ROI suitable for translation-free quantification of myocardial videointensity over time, MVI(t), from contrast-enhanced RT3DE images. METHODS AND RESULTS Twelve transthoracic RT3DE (Philips) data sets obtained in pigs during transition from no contrast to steady-state enhancement (Definity) were analysed using custom software. Analysis included: (i) semi-automated detection of left ventricular endo- and epicardial surfaces using level-set techniques in one frame to define a 3D myocardial ROI, (ii) rigid 3D registration to reduce translation and rotation, (iii) elastic 3D registration to compensate for deformation, and (iv) quantification of MVI(t) in the 3D ROI from the registered and non-registered data sets to assess the effectiveness of registration. For each MVI(t) curve we computed % variability during steady-state enhancement (100 x SD/mean) and goodness of fit (r2) to the indicator dilution equation MVI(t) = A[1-exp(-betat)]. Analysis of myocardial contrast throughout contrast inflow was feasible in all data sets. Three-dimensional registration improved MVI(t) curves in terms of both % variability (2.8 +/- 1.8 to 1.5 +/- 0.9%; P < 0.05) and goodness of fit (r2 from 0.79 +/- 0.2 to 0.90 +/- 0.1; P < 0.05). CONCLUSION This is the first study to describe a new technique for semi-automated volumetric quantification of myocardial contrast from RT3DE images that includes registration and thus provides the basis for 3D measurement of myocardial perfusion.

Quantitative assessment of myocardial perfusion using real-time three-dimensional echocardiographic imaging

The new real-time three-dimensional (RT3D) echocardiographic technology offers an opportunity for myocardial perfusion imaging in the entire heart without the need for reconstruction from multiple slices and repeated contrast maneuvers. Our aims were to develop and validate a technique for quantitative volumetric assessment of myocardial perfusion. Studies were conducted in 5 isolated rabbit hearts and in 5 patients with ischemic heart disease. In rabbits, RT3D datasets were acquired over 30 sec, during which infusion of contrast agent definity was initiated and reached steady-state myocardial enhancement. Data were obtained at 3 different levels of coronary flow. At each level, myocardial videointensity (MVI) was measured over time in 3 LV short-axis slices of fixed thickness and peak contrast inflow rate (PCIR) was calculated. Administration of contrast resulted in clearly visible and measurable dynamic changes in MVI. PCIR followed the changes in coronary flow (p<0.0I). Feasibility in humans was tested by imaging the interventricular septum during initiation of infusion of definity at rest and during adenosine infusion. Dynamic changes in MVI were visible and suitable for quantitative analysis. In 2 patients, adenosine resulted in dark regions, reflecting lack of myocardial filling in stenosis-related territories. RT3D imaging and quantification of myocardial perfusion using our algorithm are feasible. This approach can potentially allow more accurate assessment of the extent of perfusion defects than 2D myocardial contrast echocardiography.

Semi-automated segmentation and registration of triggered three-dimensional echocardiographic images as a basis for volumetric analysis of myocardial perfusion

We developed a technique for automated identification of 3D myocardial ROI suitable for translation-free quantification of myocardial videointensity over time, MVI(t), from RT3DE images. Our software was tested on 12 ECG-triggered RT3DE datasets obtained in pigs during transient contrast inflow. Analysis included: (1) semi-automated detection of endo- and epicardial surfaces using level-set techniques to define a 3D myocardial ROI, (2) rigid 3D registration to reduce translation and rotation, (3) elastic 3D registration to compensate for deformation, and (4) quantification of MVI(t) with and without registration to assess its effectiveness. Analysis of myocardial contrast throughout contrast inflow was feasible in all datasets. 3D registration improved MVI(t) curves in terms of both % variability during steady-state enhancement: 2.8plusmn1.8% to 1.5plusmn0.9%, and goodness of fit to the indicator dilution equation MVI(t)=Aldr(1-exp(-betat)): r2 from 0.79plusmn0.2 to 0.90plusmn0.1. This is the first study to describe a new technique for semi-automated volumetric quantification of myocardial contrast from RT3DE images that includes registration and thus provides the basis for 3D measurement of myocardial perfusion.

Echocardiographic imaging and quantification of myocardial perfusion based on interrupted contrast infusion

Echocardiographic quantification of myocardial perfusion, based on analysis of contrast replenishment foliowing destructive high-energy ultrasound impulses flash-echo). has multiple limitations. We present an alternative approach. based on analysis of conrrast replenishment afier brief interruptions of contrast infksion (ICI). Images were acquired in 8 isolated rabbit hearts at 3flow levels (baseline; 50% and 15%) during contrast infusion (Defnily) with flash-echo and, asfer ICI. Peak contrast inflow rate (PCIR) was calculated from ICI data and compared with Jash-echo dda. Clinical feasibiliQ was rested in 5 subjects with the ICI technique at rest and stress. In rabbit hearts, PCIR foilowed changes in coronary flow (p<0.0001) and had lower inter-measurement variability than the flashecho data. In humans, stress PCIR was 284±142% of resting value. ICI provides the basis for accurate and reproducible quuntification of myocurdial perfision and may consritule on alternative to the currently used techniques.