Short-term hemodynamic performance of the mitral Carpentier-Edwards PERIMOUNT pericardial valve. Carpentier-Edwards PERIMOUNT Investigators.

BACKGROUND: Although long-term durability data exist, little data are available concerning the hemodynamic performance of the Carpentier-Edwards PERIMOUNT pericardial valve in the mitral position. METHODS: Sixty-nine patients who were implanted with mitral PERIMOUNT valves at seven international centers between January 1996 and February 1997 consented to participate in a short-term echocardiography follow-up. Echocardiographs were collected at a mean of 600+/-133 days after implantation (range, 110 to 889 days); all underwent blinded core lab analysis. RESULTS: At follow-up, peak gradients were 9.09+/-3.43 mm Hg (mean, 4.36+/-1.79 mm Hg) and varied inversely with valve size (p < 0.05). The effective orifice areas were 2.5+/-0.6 cm2 and tended to increase with valve size (p = 0.08). Trace mitral regurgitation (MR) was common (n = 48), 9 patients had mild MR, 1 had moderate MR, none had severe MR. All MR was central (n = 55) or indeterminate (n = 3). No paravalvular leaks were observed. Mitral regurgitation flow areas were 3.4+/-2.8 cm2 and were without significant volumes. CONCLUSIONS: In this multicenter study, these mitral valves are associated with trace, although physiologically insignificant, central MR. Despite known echocardiographic limitations, the PERIMOUNT mitral valves exhibit similar hemodynamics to other prosthetic valves.

Real-time three-dimensional color Doppler echocardiography for characterizing the spatial velocity distribution and quantifying the peak flow rate in the left ventricular outflow tract.

Quantification of flow with pulsed-wave Doppler assumes a "flat" velocity profile in the left ventricular outflow tract (LVOT), which observation refutes. Recent development of real-time, three-dimensional (3-D) color Doppler allows one to obtain an entire cross-sectional velocity distribution of the LVOT, which is not possible using conventional 2-D echo. In an animal experiment, the cross-sectional color Doppler images of the LVOT at peak systole were derived and digitally transferred to a computer to visualize and quantify spatial velocity distributions and peak flow rates. Markedly skewed profiles, with higher velocities toward the septum, were consistently observed. Reference peak flow rates by electromagnetic flow meter correlated well with 3-D peak flow rates (r = 0.94), but with an anticipated underestimation. Real-time 3-D color Doppler echocardiography was capable of determining cross-sectional velocity distributions and peak flow rates, demonstrating the utility of this new method for better understanding and quantifying blood flow phenomena.

Hypotension, autonomic failure, and cardiac hypertrophy in transgenic mice overexpressing the alpha 1B-adrenergic receptor.

alpha(1)-Adrenergic receptors (alpha(1A), alpha(1B), and alpha(1D)) are regulators of systemic arterial blood pressure and blood flow. Whereas vasoconstrictory action of the alpha(1A) and alpha(1D) subtypes is thought to be mainly responsible for this activity, the role of the alpha(1B)-adrenergic receptor (alpha(1B)AR) in this process is controversial. We have generated transgenic mice that overexpress either wild type or constitutively active alpha(1B)ARs. Transgenic expression was under the control of the isogenic promoter, thus assuring appropriate developmental and tissue-specific expression. Cardiovascular phenotypes displayed by transgenic mice included myocardial hypertrophy and hypotension. Indicative of cardiac hypertrophy, transgenic mice displayed an increased heart to body weight ratio, which was confirmed by the echocardiographic finding of an increased thickness of the interventricular septum and posterior wall. Functional deficits included an increased isovolumetric relaxation time, a decreased heart rate, and cardiac output. Transgenic mice were hypotensive and exhibited a decreased pressor response. Vasoconstrictory regulation by alpha(1B)AR was absent as shown by the lack of phenylephrine-induced contractile differences between ex vivo mesenteric artery preparations. Plasma epinephrine, norepinephrine, and cortisol levels were also reduced in transgenic mice, suggesting a loss of sympathetic nerve activity. Reduced catecholamine levels together with basal hypotension, bradycardia, reproductive problems, and weight loss suggest autonomic failure, a phenotype that is consistent with the multiple system atrophy-like neurodegeneration that has been reported previously in these mice. These results also suggest that this receptor subtype is not involved in the classic vasoconstrictory action of alpha(1)ARs that is important in systemic regulation of blood pressure.

Relationship of echocardiographic indices to pulmonary capillary wedge pressures in healthy volunteers.

OBJECTIVES: We sought to determine the relationship between different echocardiographic indices and pulmonary capillary wedge pressures (PCWP) in normal volunteers. BACKGROUND: Indices based on tissue Doppler (TDE) and color M-mode (CMM) echocardiography have been proposed to reflect left (LV) ventricular filling pressures. These include the ratio of early diastolic transmitral velocity (E) to early myocardial velocity measured by TDE (E') and the ratio of E to the wave propagation velocity (Vp) measured from CMM images. These indices, however, have not been validated in normal individuals. METHODS: We studied seven volunteers during two phases of preload altering maneuvers, baseline, with two stages of lower body negative pressure, and repeat baseline with two stages of volume loading. The PCWP obtained from right heart catheterization was compared with diastolic indices using pulsed Doppler, TDE and CMM echocardiography. RESULTS: The PCWP ranged from 2.2 to 23.5 mm Hg. During preload alterations, significant changes in E and septal E' (both p < 0.05) but not lateral E' or Vp were observed. Furthermore, E, septal E' and E/Vp correlated with PCWP (all r > 0.80) but not combined E and TDE indices (both r < 0.15). Within individuals, a similar linear relationship was observed among E/Vp, E and septal E' (average r > 0.80). CONCLUSIONS: In subjects without heart disease, E, septal E' and E/Vp correlate with PCWP. Because the influence of ventricular relaxation is minimized, the ratio E/Vp may be the best overall index of LV filling pressures.

Internet-based transfer of cardiac ultrasound images.

A drawback to large-scale multicentre studies is the time required for the centralized evaluation of diagnostic images. We evaluated the feasibility of digital transfer of echocardiographic images to a central laboratory for rapid and accurate interpretation. Ten patients undergoing trans-oesophageal echocardiographic scanning at three sites had representative single images and multiframe loops stored digitally. The images were analysed in the ordinary way. All images were then transferred via the Internet to a central laboratory and reanalysed by a different observer. The file sizes were 1.5-72 MByte and the transfer rates achieved were 0.6-4.8 Mbit/min. Quantitative measurements were similar between most on-site and central laboratory measurements (all P > 0.25), although measurements differed for left atrial width and pulmonary venous systolic velocities (both P < 0.05). Digital transfer of echocardiographic images and data to a central laboratory may be useful for multicentre trials.

Intraoperative echocardiographic detection of regurgitant jets after valve replacement.

BACKGROUND: Paravalvular jets, documented by intraoperative transesophageal echocardiography, have prompted immediate valve explantation by others, yet the significance of these jets is unknown. METHODS: Twenty-seven patients had intraoperative transesophageal two-dimensional color Doppler echocardiography, performed to assess the number and area of regurgitant jets after valve replacement, before and after protamine. Patients were grouped by first time versus redo operation, valve position and type. RESULTS: Before protamine, 55 jets were identified (2.04+/-1.4 per patient) versus 29 jets after (1.07+/-1.2 per patient, p = 0.0002). Total jet area improved from 2.0+/-2.2 cm2 to 0.86+/-1.7 cm2 with protamine (p<0.0001). In all patients jet area decreased (average decrease, 70.7%+/-27.0%). First time and redo operations had similar improvements in jet number and area (both p>0.6). Furthermore, mitral and mechanical valves each had more jets and overall greater jet area when compared to aortic and tissue valves, respectively. CONCLUSIONS: Following valve replacement, multiple jets are detected by intraoperative transesophageal echocardiography. They are more common and larger in the mitral position and with mechanical valves. Improvement occurs with reversal of anticoagulation.

Impact of temporal resolution on flow quantification by real-time 3D color Doppler echocardiography: numerical modeling and animal validation study.

Real-time, 3D color Doppler echocardiography (RT3D) is capable of quantifying flow at the LV outflow tract (LVOT). However, previous works have found significant underestimation for flow rate estimation due to finite scanning time (ST) of the color Doppler. The authors have, therefore, developed a mathematical model to correct the impact of ST on flow quantification and validated it by an animal study. Scanning time to cover the entire cross-sectional image of the LVOT was calculated as 60 ms, and the underestimation due to temporal averaging effect was predicted as 18 +/- 7%. In the animal experiment, peak flow rates were obtained by spatially integrating the velocity data front the cross-sectional color images of the LVOT. By applying a correction factor, there was an excellent agreement between reference flow rate by an electromagnetic flow meter and RT3D (angstroms=-5.6 ml/s, r=0.93), which was significantly better than without correction (p<0.001). Real-time, color 3D echocardiography was capable of quantifying flow accurately by applying the mathematical correction.

Integrated backscatter for quantification of left atrial spontaneous echo contrast.

OBJECTIVES: This study was designed to develop a quantitative method of spontaneous echo contrast (SEC) assessment using integrated backscatter and to compare integrated backscatter SEC measurement with independent qualitative grades of SEC and clinical and echocardiographic predictors of thromboembolism. BACKGROUND: Left atrial SEC refers to dynamic swirling smokelike echoes that are associated with low flow states and embolic events and have been graded qualitatively as mild or severe. METHODS: We performed transesophageal echocardiography in 43 patients and acquired digital integrated backscatter image sequences of the interatrial septum to internally calibrate the left ventricular cavity and left atrial cavity under different gain settings. Patients were independently assessed as having no, mild or severe SEC. We compared intensity of integrated backscatter in the left atrial cavity relative to that in the left ventricular as well as to the independently assessed qualitative grades of SEC. Fourier analysis characterized the temporal variability of SEC. The integrated backscatter was compared with clinical and echocardiographic predictors of thromboembolism. RESULTS: The left atrial cavity integrated backscatter intensity of the mild SEC subgroup was 4.7 dB higher than that from the left ventricular cavity, and the left atrial intensity of the severe SEC subgroup was 12.5 dB higher than that from the left ventricular cavity. The left atrial cavity integrated backscatter intensity correlated well with the qualitative grade. Fourier transforms of SEC integrated backscatter sequences revealed a characteristic dominant low frequency/high amplitude spectrum, distinctive from no SEC. There was a close relationship between integrated backscatter values and atrial fibrillation, left atrial size, left atrial appendage flow velocities and thrombus. CONCLUSIONS: Integrated backscatter provides an objective quantitative measure of SEC that correlates well with qualitative grade and is closely associated with clinical and echocardiographic predictors of thromboembolism. The relationship between integrated backscatter measures and cardioembolic risk will be defined in future multicenter studies.

JPEG compression of digital echocardiographic images: impact on image quality.

Routine echocardiograms are not handled digitally because of enormous storage needs. Image compression techniques can reduce memory requirements, but the impact on diagnostic content is unknown. We studied the effect of an internationally accepted compression algorithm called Joint Photographic Experts Group (JPEG) on digital echocardiographic images. Diagnostic and image quality of JPEG compressed, two-dimensional echocardiograms at ratios ranging from 4:1 to 40:1 was compared with that of uncompressed images both subjectively by a blinded expert panel (540 observations) and objectively by quantitative image-processing parameters (180 images). Accuracy of 432 measurements performed on compressed M-mode and spectral Doppler tracings was determined. Simultaneously acquired videotaped images and their never-compressed digital counterparts were compared quantitatively for image fidelity. This study demonstrates that the JPEG compression algorithm produces little degradation of echocardiographic images at compression ratios of at least 20:1, with less measured distortion than is produced by videotape recording. With JPEG, digital storage and retrieval in routine echocardiography are feasible.

Reliability of echocardiographic measurements of myocardial perfusion using commercially produced sonicated serum albumin (Albunex).

OBJECTIVES: The purpose of this study was to assess the reproducibility and pitfalls of intracoronary and aortic root sonicated albumin injections, using time-intensity curves, in a large sample of normal dogs. BACKGROUND: The utility of a new myocardial contrast echocardiographic agent, sonicated serum albumin (Albunex), is currently under investigation. However, the reproducibility, injection techniques and general pitfalls of this contrast agent have not been well characterized. METHODS: We administered sequential intracoronary and aortic root injections (518 injections) of sonicated albumin in 25 closed chest normal dogs to measure the effectiveness and reproducibility of this product. Time-intensity curves, as a measure of myocardial perfusion, were derived and quantified using an on-line videodensitometric analysis system and two-dimensional echocardiography. Measurements included peak intensity, area under the curve, half-time of descent, alpha-parameter and transit time within a 31- x 31-pixel "region of interest" in the anterior septum. Analyses provided 80% power and a type I error protection of 95%. RESULTS: The best reproducibility of the variables was half-time of descent for aortic root injections (coefficient of variation [CV] 20%) and peak intensity for intracoronary injections (CV 25%), whereas aortic root area under the curve showed the most variability (CV 41%). Analysis of variance for repeated measures of serial intracoronary and aortic root injections showed no significant systematic variability within subjects for the measured variables. In a comparison between intracoronary and aortic root injection sites, paired t tests showed no significant difference for mean values between these two techniques. There was also no statistically significant difference between manual versus power intracoronary injections. Finally, there was no significant difference among three injection rates (1, 2 and 3 ml/s) in paired intracoronary injections, nor was there a difference among injection rates in paired aortic root injections, except for a lower peak intensity with a 1-ml/s injection rate compared with a 2-ml/s injection rate (p = 0.01). Potential pitfalls include preparation of sonicated albumin, delivery techniques and measurement variables. CONCLUSIONS: We conclude that the results of serial injections of sonicated albumin show no systemic change or trend in normal dogs. Both intracoronary and aortic root injections at standard injection rates by hand or power injector can be used to quantify time-intensity curves, as measure of myocardial perfusion, with similar variability ranging from 20% to 41%. These results are important in the human model, especially after coronary interventions.