The International Journal of Cardiovascular Imaging

Baroni, Monica; Torres, Marco; Maffei, Stefano; Varga, Albert; Terrazzi, Marco; Biagini, Andrea; Picano, Eugenio

doi: 10.1023/A:1006122725824pmid: 10517376

Background: Infra-low dose dipyridamole allows one to selectively explore myocardial viability. Transesophageal echocardiography Doppler measurement of left anterior descending coronary artery flow at baseline and following dipyridamole is an efficient tool to assess coronary flow response. Aim of this study was to determine the flow-function relationship during coronary vasodilatory stress in patients with coronary artery disease and baseline dysfunction. Methods and results: Twelve patients with resting dyssynergies and 6 controls underwent assessment of regional function and of left anterior descending blood flow velocity. Flow and function were evaluated at rest and following infra-low dose dipyridamole (0.28 mg/Kg over 4 min). Controls showed a normal function at rest and after dipyridamole. Six patients (‘Responders’) with resting dyssynergies showed an improvement in segments of left anterior descending artery territory, whereas the other six ones (‘Non-responders’) showed no functional change. Controls and ‘Responders’ had similar values of resting peak diastolic left anterior descending artery flow velocity both at rest and after dipyridamole, whereas ‘Non-responders’ showed a blunted flow response to dipyridamole. Conclusion: Myocardial segments with a resting dysfunction and a contractile reserve more often exhibit a residual flow response, whereas segments with fixed pattern show a flat flow response during coronary vasodilator stress.

Shahid, Maie; Hatle, Liv; Mansour, Hend; Mimish, Layth

doi: 10.1023/A:1006070708952pmid: 10517377

This is a two-dimensional and Doppler echocardiographic study of the hemodynamic changes in patients with heatstroke and heat exhaustion. It demonstrates that the hemodynamic changes in severe heat exposure reflect a hyperdynamic circulation with tachycardia and high cardiac output states. Relative hypovolemia was more pronounced in patients with heatstroke compared to patients with heat exhaustion. Signs of peripheral vasoconstriction were more often present in patients with heatstroke, while patients with heat exhaustion more often demonstrated peripheral vasodilatation.

Williams, Michael; Stewart, Ralph; Low, Clive; Wilkins, Gerard

doi: 10.1023/A:1006279228534pmid: 10517378

The pressure-area relation of coronary arteries provides important information about the mechanical properties of these vessels. In human subjects methodological limitations have precluded measurement of instantaneous compliance and coronary stress in vivo. The purpose of this study was to assess a new method for measuring instantaneous values of coronary artery compliance and wall stress utilizing simultaneously acquired pressure and intravascular ultrasound measurements of vessel area. Ten subjects with coronary artery disease had intravascular ultrasound studies of the proximal left anterior descending or circumflex coronary arteries. Coronary luminal area was measured with a 30-MHz (3F or 3.5F) intravascular ultrasound catheter and simultaneous coronary pressure measured with a 2F micromanometer-tipped catheter. Using this technique the nonlinear pressure-area relation and mean circumferential wall stress were determined over the physiological pressure range. Coronary artery compliance at 100 mmHg ranged from 0.010 to 0.052 mm2/mmHg (mean ± SD, 0.020 ± 0.012 mm2/mmHg). Peak systolic circumferential stress ranged from 0.52 to 2.03 × 106 dyn/cm2 (1.09 ± 0.42×106 dyn/cm2). This study describes a new method of determining coronary artery mechanical properties over the physiological pressure range. This technique may be useful in further studies of coronary artery mechanics.

Ge, Junbo; Liu, Fengqi; Bhate, Rahul; Haude, Michael; Görge, Günter; Baumgart, Dietrich; Sack, Stefan; Erbel, Raimund

doi: 10.1023/A:1006125205217pmid: 10517379

Background: Coronary artery remodeling is a common phenomenon in human atherosclerotic arteries. Controversies exist concerning the presence of absence of the remodeling process in diseased human coronary saphenous vein bypass grafts. The purpose of the study was to observe the vessel and lumen dimensions in patients who had undergone saphenous vein grafting with intravascular ultrasound to find out whether the remodeling process exists in the diseased human saphenous vein bypass grafts. Methods: A total of 43 saphenous vein bypass grafts from 43 patients (39 males, 4 females, mean age 63 ± 8 years); 1–16 years (mean 9.3 ± 4.0 years) after grafting, who had not undergone previous catheter intervention, were studied using intravascular ultrasound. The vessel, lumen and plaque area were measured at the lesion segment as well as in the proximal and distal reference segments. The percent stenosis was calculated. Results: In 43 bypass grafts having severe stenosis before intervention, plaque was eccentric in 69.4% and concentric in 30.6%. No calcification was detected in 75% cases and 25% cases has mild-moderate intimal calcification. The vessel area in the lesion segment was 19.0 ± 9.7 mm2, significantly larger than the proximal reference segment 12.8 ± 4.0 mm2 as well as the distal reference segment 12.9 ± 3.6 mm2 (p < 0.001). It was also larger than that of the average area of the proximal and distal reference segments (p < 0.001). The vessel area increased in accordance with plaque area (p < 0.001). A weak relationship existed between vessel area and percent stenosis (r = 0.37, p = 0.04). Conclusion: In contrary to previous findings, diseased human saphenous vein bypass grafts undergo focal compensatory enlargement (remodeling) in the presence of plaque formation. The underlying mechanism is probably similar to that in de novo atherosclerosis.

Ratanasopa, Sarah; Bolson, Edward; Sheehan, Florence; McDonald, John; Bashein, Gerard

doi: 10.1023/A:1006184726733pmid: 10517380

Objectives: We investigated the accuracy of mitral annular reconstruction from noisy, sparse data typical of three-dimensional (3D) transthoracic echocardiograms. Background: Our Fourier-based method for reconstructing the annulus from dense, accurate 3D transesophageal echo (TEE) data has been validated in vitro with four harmonics in the x, y, and z coordinates (4,4,4). Methods: Thirteen mitral annuli were reconstructed from ‘complete’ 3D TEE data using four harmonics (4,4,4) and used to measure area, eccentricity, height, perimeter, and interpeak and intervalley distances; these were the ‘true values’. To simulate transthoracic echo data, the TEE data sets were reduced evenly and unevenly (randomly). The complete and reduced data sets were used to reconstruct the annuli using three sets of fitting parameters: (4,4,4), (1,1,3), and (1,1,4). The resulting size and shape measurements were compared with true values. Results: Regardless of the fitting parameters used, area, 2D perimeter, and 3D perimeter measurements were more accurate using reconstructions from evenly-reduced than randomly-reduced data sets (p < 0.006), and depended significantly on both data density (p < 0.015 for all) and data distribution (p < 0.02 for all). Perimeter, height, and eccentricity of the reconstructed annuli were more accurately measured using four harmonics (4,4,4). Conclusions: Mitral annuli can be reconstructed from sparse, noisy data using the (4,4,4) fit if at least 25 points are obtained from evenly distributed imaging planes. These results suggest that detailed analysis of mitral annular size and shape can be made accurately from 3D transthoracic echocardiograms.

Petrank, Yael; Dong, Sheng; Tyberg, John; Sideman, Samuel; Beyar, Rafael

doi: 10.1023/A:1006132709895pmid: 10517381

Objectives: We aimed to characterize regional geometry in relation to load in two groups of patients with hypertrophic cardiomyopathy (HCM) and right ventricular pressure overload (RVPO) in relation to a group of subjects with normal left ventricular (LV) function. Background: Both these diseases are associated with marked changes in LV shape and function, which have not been studied with detailed three dimensional tools. Methods: Three dimensional (3D) tagged magnetic resonance imaging (MRI) was used to characterize the 3D geometry and regional stresses of the left ventricles in patients with HCM and RVPO. Curvatures, stresses, wall thickness, and endocardial motion were calculated from surface and volume elements. Results: Hearts with RVPO exhibited more circumferential and meridional flattening of the septum than normal and HCM hearts. The stress indices were lowest in the HCM hearts, compared to normal and RVPO hearts, due to the larger thicknesses. There was a more significant difference between lateral wall motion and other regional wall motions in the HCM and RVPO hearts as compared to normal hearts. Conclusions: It is suggested that curvature and stress mapping by 3D tagged MRI can be used as an important clinical tool for characterizing and distinguishing between healthy and diseased hearts. The results provided here validated previous knowledge on HCM and RVPO known from planary imaging methods.

Niezen, R.; Beekman, Rudolf; Helbing, Willem; van der Wall, Ernst; de Roos, Albert

doi: 10.1023/A:1006112529535pmid: 10517382

In this article the value of magnetic resonance (MR) imaging for the evaluation of double outlet right ventricle (DORV) is reviewed from the literature and illustrated with several cases. MR imaging can be used for the determination of cardiac anatomy at initial diagnosis and may provide functional information during the follow-up of patients after surgical correction.

Horigome, Hitoshi; Tsukada, Keiji; Kandori, Akihiko; Shiono, Junko; Matsui, Akira; Terada, Yasushi; Mitsui, Toshio

doi: 10.1023/A:1006136525382pmid: 10517383

Background: Tangential components to the body surface on magnetocardiography theoretically reflect regional myocardial current sources just below the gradiometer. The usefulness of tangential component mapping on magnetocardiography in determination of regional myocardial abnormalities has not been investigated in children. Methods: Twenty-six children with ventricular hypertrophy, including a child with a left ventricular diverticulum (aged 7 to 15), and age matched 22 healthy children (aged 7 to 15) were studied. Tangential components on magnetocardiography were measured using a newly-developed superconducting quantum interference device system housed in a magnetically shielded room. Isomagnetic maps and current vector maps were constructed from the data obtained. Results: The peak magnetic fields and current dipoles were demonstrated to be located at the interventricular septum initially, and then were shifted to the anterior and inferior walls of the left ventricle and to the right ventricular outflow tract, successively. In patients with right ventricular hypertrophy whose systolic right ventricular pressure was over 60 mmHg, the peak magnetic fields were located in the right half with rightward directed current vectors throughout ventricular depolarization. In patients with left ventricular hypertrophy, the maximal magnetic fields during depolarization were shifted to the hypertrophic site, showing significantly stronger forces than those in healthy children (35.5 ± 11.7 pT vs 26.5 ± 11.9 pT, p < 0.01). In a patient with left ventricular diverticulum, two discrete depolarizing current dipoles were visualized. The mean time required in measuring MCGs among all subjects was 10 minutes. Conclusion: he time course as well as the location of the regional electrical activities of the myocardium in children can be visualized, in a short time, as a two-dimensional projection to the frontal plane by tangential component mapping on magnetocardiography.