Rapid construction of a patient-specific torso model from 3D ultrasound for non-invasive imaging of cardiac electrophysiology.

One of the main limitations in using inverse methods for non-invasively imaging cardiac electrical activity in a clinical setting is the difficulty in readily obtaining high-quality data sets to reconstruct accurately a patient-specific geometric model of the heart and torso. This issue was addressed by investigation into the feasibility of using a pseudo-3D ultrasound system and a hand-held laser scanner to reconstruct such a model. This information was collected in under 20 min prior to a catheter ablation or pacemaker study in the electrophysiology laboratory. Using the models created from these data, different activation field maps were computed using several different inverse methods. These were independently validated by comparison of the earliest site of activation with the physical location of the pacing electrodes, as determined from orthogonal fluoroscopy images. With an estimated average geometric error of approximately 8 mm, it was also possible to reconstruct the site of initial activation to within 17.3 mm and obtain a quantitatively realistic activation sequence. The study demonstrates that it is possible rapidly to construct a geometric model that can then be used non-invasively to reconstruct an activation field map of the heart.

Ventricular septal aneurysm: a complication of myocardial infarction.

We report the case of a ventricular septal aneurysm in a patient with a previous inferior myocardial infarction. Two-dimensional echocardiography demonstrated a cystic cavity in the muscular septum with a small communication into the left ventricle. No evidence of left-to-right shunt was detected with Doppler echocardiography or during left ventriculography.

Initial experience with the freestyle stentless aortic bioprosthesis.

AIMS: We report our initial experience with the Freestyle aortic bioprosthesis. METHODS: This prosthesis was implanted in 40 patients between February 1993 and December 1998. Operative indications were aortic stenosis in 32 patients (80%), aortic regurgitation in seven patients (18%) and a combined lesion in one (3%). The mean patient age was 71.4+/-9.7 (SD) years, with 29 (72%) females. Pre-operative New York Heart Association (NYHA) class was III or IV in 28 (70%). Left ventricular systolic function was impaired in four (10%). Six (15%) patients had undergone previous cardiac surgery. Concomitant procedures were carried out in 21 patients (53%). RESULTS: Early mortality was zero. Early morbidity included three re-operations for bleeding, one cerebrovascular event, one haemorrhagic complication and one case of valve dysfunction. At follow up (range 4.6 to 75.6 months, mean 29.5+/-25.5) there has been one (3%) late death which was non valve related, one (3%) episode of study-valve endocarditis, and three (8%) thromboembolic episodes. NYHA Class was I or II in all but one survivor. Echocardiographic follow-up has shown no further instances of valve dysfunction with satisfactory haemodynamic parameters at 24-months post-operation, and a significant and sustained regression of left ventricular mass. CONCLUSIONS: The initial experience with the Freestyle valve is that it results in good clinical and haemodynamic performance, suggesting it as an ideal bioprosthesis for this patient group.

Early experience with the mosaic bioprosthesis: a new generation porcine valve.

BACKGROUND: The Mosaic bioprosthesis is a new generation stented porcine valve. METHODS: Between May 1995 and April 1998, this valve was implanted in the aortic position in 98 patients (70 men; mean age, 69.2 years [34.2 to 83.6 years]). Preoperatively 35 patients were in New York Heart Association functional class 3 or 4. Fifty-nine patients underwent concomitant procedures. The mean duration at follow-up in January 1999 was 23.7 +/- 10.2 months (0.3 to 39.4 months) and totaled 193 patient-years. All but one survivor was in New York Heart Association class 1 or 2. RESULTS: Early complications included 1 death, 3 reoperations for bleeding, greater than mild regurgitation (paravalvar) in 1 patient and thromboembolism in 4 patients. Late complications included four deaths, study-valve endocarditis in 3 patients, more than mild regurgitation or hemolysis in 2, and thromboembolism in 2 patients. Late follow-up echocardiography in all survivors showed a mean transaortic gradient of 13.6 +/- 6.7 mm Hg, and an aortic valve area of 1.80 +/- 0.61 cm2. Valve replacement was followed by a significant and sustained decrease in left ventricular mass for all valve sizes. There has been no primary structural valve failure. CONCLUSIONS: The early experience with the Mosaic valve in the aortic position has been promising.

Three-dimensional echocardiographic assessment of annular shape changes in the normal and regurgitant mitral valve.

OBJECTIVES: To compare mitral annular shape and motion throughout the cardiac cycle in patients with normal hearts versus those with functional mitral regurgitation (FMR). BACKGROUND: The causes of mitral regurgitation without valvular disease are unclear, but the condition is associated with changes in annular shape and dynamics. Three-dimensional (3D) imaging provides a more comprehensive view of annular structure and allows accurate reconstructions at high spatial and temporal resolution. METHODS: Nine normal subjects and 8 patients with FMR undergoing surgery underwent rotationally scanned transesophageal echocardiography. At every video frame of 1 sinus beat, the mitral annulus was manually traced and reconstructed in 3D by Fourier series. Annular projected area, nonplanarity, eccentricity, perimeter length, and interpeak and intervalley spans were determined at 10 time points in systole and 10 points in diastole. RESULTS: The mitral annulus in patients with FMR had a larger area, perimeter, and interpeak span than in normal subjects (P <.001 for all). At mid-systole in normal annuli, area and perimeter reach a minimum, nonplanarity is greatest, and projected shape is least circular. These cyclic variations were not significant in patients with FMR. Annular area change closely paralleled perimeter change in all patients (mean r = 0.96 +/- 0.07). CONCLUSIONS: FMR is associated with annular dilation and reduced cyclic variation in annular shape and area. Normal mitral valve function may depend on normal annular 3D shape and dimensions as well as annular plasticity. These observations may have implications for design and selection of mitral annular prostheses.

Physical examination in valvular aortic stenosis: correlation with stenosis severity and prediction of clinical outcome.

BACKGROUND AND METHODS: The goal of this study was to examine the ability of physical examination to predict valvular aortic stenosis severity and clinical outcome in 123 initially asymptomatic subjects (mean age 63 +/- 16 years, 70% men) followed up for a mean of 2.5 +/- 1.4 years. RESULTS: Doppler aortic jet velocity correlated with systolic murmur intensity (P =.003) and timing (P =.0002), a single second heart sound (P =.01), and carotid upstroke delay (P <.0001) and amplitude (P <.0001). However, no physical examination findings had both a high sensitivity and a high specificity for the diagnosis of severe valvular obstruction. Clinical end points were reached in 56 subjects (46%), including 8 deaths and 48 valve replacements for symptom onset. Univariate predictors of outcome included carotid upstroke delay (P =.0008) and amplitude (P =.0006), systolic murmur grade (P <.0001) and peak (P =.0003), and a single second heart sound (P =.003). On multivariate Cox regression analysis, the only physical examination predictor of outcome was carotid upstroke amplitude (P =.0001). CONCLUSIONS: Although physical examination findings correlate with stenosis severity, echocardiography still is needed to exclude severe obstruction reliably when this diagnosis is suspected.

Cardiac surgery in octogenarians--The Green Lane Hospital Experience 1995-1998.

BACKGROUND: An increasing number of patients aged 80 years and over are being considered and accepted for cardiac surgery. AIM: To review the experience of surgery in this elderly group of patients at our institution. METHODS: Hospital records of octogenarians undergoing surgery between January 1995 and September 1998 were reviewed and follow-up was obtained by general practitioner (GP) and patient questionnaires. RESULTS: Thirty-seven patients underwent cardiac surgery. The mean age was 82.8+/-1.4 years (range 80.8 to 86.2 years). Twenty-three (62%) were male. All were independent pre-operatively with severe symptoms and minor co-existing morbidity. All operations were urgent except two (emergency). Twenty patients (54%) had isolated coronary surgery, six (16%) aortic valve replacement alone, and 11 (30%) combined surgery. There were four (11%) early deaths and five (14%) peri-operative neurological events. The mean duration of post-operative intensive care stay was 2.4+/-3.9 days (range 0.05 to 16, median 1.0) and post-operative hospital stay 14.0+/-13.9 days (range 0 to 79, median 11). At the time of follow-up (mean duration 20.0+/-11.2 months) two further patients had died (non-cardiac). Twenty-six of the 31 survivors were living at home (23 independently), one with relatives, and four in residential care. Their cardiac symptoms were well controlled. The GPs of all hospital survivors, and all surviving patients themselves, felt that cardiac surgery had been beneficial. CONCLUSIONS: Cardiac surgery in the very elderly has been reserved for those with severe disease or symptoms and little co-morbidity. Early mortality is higher than for the general population undergoing cardiac surgery, but post-operative resource use is acceptable and the intermediate-term outcome for survivors is good.

System for quantitative three-dimensional echocardiography of the left ventricle based on a magnetic-field position and orientation sensing system.

Accurate measurement of left-ventricular (LV) volume and function are important to monitor disease progression and assess prognosis in patients with heart disease. Existing methods of three-dimensional (3-D) imaging of the heart using ultrasound have shown the potential of this modality, but each suffers from inherent restrictions which limit its applicability to the full range of clinical situations. We have developed a technique for image acquisition using a magnetic-field system to track the 3-D echocardiographic imaging planes and 3-D image analysis software including the piecewise smooth subdivision method for surface reconstruction. The technique offers several advantages over existing methods of 3-D echocardiography. The results of validation using in vitro LV's show that the technique allows accurate measurement of LV volume and anatomically accurate 3-D reconstruction of LV shape and is, therefore, suitable for analysis of regional as well as global function.

Three-dimensional measurement of the mitral annulus by multiplane transesophageal echocardiography: in vitro validation and in vivo demonstration.

Ten phantoms were scanned with a multiplane transesophageal echocardiographic probe in a water bath to assess a new method for three-dimensional modeling of the mitral annulus. The annulus was reconstructed from manually outlined borders with Fourier series in each of the three spatial coordinates. Comparisons with direct measurements by least-squares linear regression gave coefficients of determination of 0.99 for annular height, area, and circumference. Expressed as a percentage of their true values, the mean +/- SD of the errors were -0.1% +/- 3.0% for annular height, -2.8% +/- 3.1% for area, and -0.2% +/- 1.7% for circumference. The mean residual error length for phantoms was 0.64 mm compared with 1.21 mm in nine patients studied during general anesthesia. This method gives accurate and precise measurements of the mitral annulus in vitro and should be valuable for studying its morphology and dynamics in vivo.

Prospective study of asymptomatic valvular aortic stenosis. Clinical, echocardiographic, and exercise predictors of outcome.

BACKGROUND: Only limited data on the rate of hemodynamic progression and predictors of outcome in asymptomatic patients with valvular aortic stenosis (AS) are available. METHODS AND RESULTS: In 123 adults (mean age, 63 +/- 16 years) with asymptomatic AS, annual clinical, echocardiographic, and exercise data were obtained prospectively (mean follow-up of 2.5 +/- 1.4 years). Aortic jet velocity increased by 0.32 +/- 0.34 m/s per year and mean gradient by 7 +/- 7 mm Hg per year; valve area decreased by 0.12 +/- 0.19 cm2 per year. Kaplan-Meier event-free survival, with end points defined as death (n = 8) or aortic valve surgery (n = 48), was 93 +/- 5% at 1 year, 62 +/- 8% at 3 years, and 26 +/- 10% at 5 years. Univariate predictors of outcome included baseline jet velocity, mean gradient, valve area, and the rate of increase in jet velocity (all P < or = .001) but not age, sex, or cause of AS. Those with an end point had a smaller exercise increase in valve area, blood pressure, and cardiac output and a greater exercise decrease in stroke volume. Multivariate predictors of outcome were jet velocity at baseline (P < .0001), the rate of change in jet velocity (P < .0001), and functional status score (P = .002). The likelihood of remaining alive without valve replacement at 2 years was only 21 +/- 18% for a jet velocity at entry > 4.0 m/s, compared with 66 +/- 13% for a velocity of 3.0 to 4.0 m/s and 84 +/- 16% for a jet velocity < 3.0 m/s (P < .0001). CONCLUSIONS: In adults with asymptomatic AS, the rate of hemodynamic progression and clinical outcome are predicted by jet velocity, the rate of change in jet velocity, and functional status.

Effects of aortic valve replacement on exercise duration and functional status in adults with valvular aortic stenosis.

OBJECTIVE: To evaluate the effect of aortic valve replacement on left ventricular function, functional status and exercise duration in an adult population with valvular aortic stenosis. DESIGN: Prospective study of initially asymptomatic patients with pre- and postvalve replacement echocardiography, functional status score and exercise data. SETTING: University-affiliated, tertiary care teaching hospital. PATIENTS: Valvular aortic stenosis patients referred from academic and private practice internists and cardiologists (n = 34, 65% men, mean age 68 +/- 11 years, preoperative aortic valve area 0.9 +/- 0.4 cm2). INTERVENTIONS: Annual Doppler echocardiography, functional status questionnaires and, if possible, Bruce protocol maximal exercise tolerance tests. MAIN RESULTS: Aortic valve replacement resulted in a decrease in maximum jet velocity (pre 4.7 +/- 0.7 versus post 2.9 +/- 0.7 m/s, P = 0.0001) and left ventricular mass (pre 167 +/- 37 versus post 134 +/- 32 g, P = 0.0001) and an increase in left ventricular ejection fraction (pre 65 +/- 11 versus post 69 +/- 10%, P = 0.05) at rest. However, there was no change in the ratio of early to atrial diastolic filling velocities (pre 1.2 +/- 0.5 versus post 1.4 +/- 0.8, not significant), exercise tolerance as assessed by estimated functional aerobic impairment (pre 26 +/- 32 versus post 22 +/- 27%, not significant) or functional status score (pre 89 +/- 13 versus post 91 +/- 11, not significant). CONCLUSIONS: When the aortic valve is replaced promptly at symptom onset, despite improvement in resting left ventricular systolic performance, there is no evidence of improvement in exercise capacity or functional status.

How positionally stable is a transesophageal echocardiographic probe? Implications for three-dimensional reconstruction.

Three-dimensional (3D) reconstruction from a single esophageal scanning position requires a stable relationship between the probe and the heart. The purpose of this study was to examine the movement of a transesophageal echocardiographic probe during 3D image acquisition. A new dual-axis multiplane probe was used that includes a miniature (6 x 6 x 9 mm) magnetic sensor in the tip. The sensor identifies the probe's 3D position and 3D orientation in space with respect to the location of a magnetic field generator placed beneath the subject. In vivo 3D scanning was performed in five anesthetized, ventilated dogs, with positional determinations acquired every 66 msec. Probe movement was estimated by computing the deviations of each x, y, and z position and orientation determination, compared with the average values during each 3D scan or cardiac cycle. Ten 3D scans were analyzed, involving 263 cardiac cycles and 2328 determinations. The range and SD of the translational movement of the transducer were 2.3 and 0.8 mm, 1.7 and 0.5 mm, and 2.4 and 0.7 mm in x, y, and z directions, respectively, during 3D scanning. Translational movement was more dominant than was rotational movement. Misregistration of three-dimensional reconstructions may be due to subtle probe movement. The ability to monitor probe movement may be helpful in optimizing 3D data sets.

Automatic border detection and three-dimensional reconstruction with echocardiography.

This article reviews two important innovations in echocardiography resulting from the recent advances in the capabilities of microprocessors. The first, automatic endocardial border detection, has been implemented on computers contained entirely within echocardiograph machines and is gaining wide clinical use. The second, three-dimensional imaging, is currently under intense investigation and shows great promise for clinical application. It requires, however, further development of the specialized transducer apparatus necessary for image acquisition and the sophisticated computer-processing capability necessary for image reconstruction and display.

Aortic root complications in Marfan's syndrome: identification of a lower risk group.

OBJECTIVES: The purpose of this study was to examine clinical and echocardiographic predictors of outcome in a cohort of patients with Marfan's syndrome. BACKGROUND: Serial echocardiographic measurements of aortic root dimensions are an important clinical method for monitoring patients with Marfan's syndrome. However, there are few data on the prognostic importance of echocardiographic variables for risk stratification and timing of aortic root replacement. METHODS: In 89 consecutive patients with Marfan's syndrome (age range 1-54 years) clinical and serial echocardiographic data (n = 62) were evaluated as potential predictors of outcome (mean (range) follow up 4 (< 1-16) years). Aortic sinus diameter and an aortic ratio normalised for age and body surface area were examined using Kaplan-Meier life table and Cox regression analysis, with the end point defined as death or surgery for ascending aortic dissection and events defined as an end point or surgery for ascending aortic aneurysm. RESULTS: Overall actuarial survival at two and five years was 96% and 92% and event free survival was 85% and 76%, respectively. There were five deaths due to aortic dissection, four patients survived surgery for ascending dissection, and nine underwent root replacement with a composite graft for ascending aneurysm. Those with aortic events were older (35 (12) v 25 (13) years, P = 0.007) and had greater initial aortic root dimensions (47 (14) v 33 (8) mm, P < 0.0001) and ratios (1.6 (0.5) v 1.3 (0.2), P < 0.0001). In the 62 patients with serial echocardiographic follow up, the rate of aortic root dilatation was more rapid in those with events (15 (17) v 0 (3)%/year, P < 0.0001). Utilising a Cox proportional hazards model, the groups with an initial aortic ratio > or = 1.3 or an annual change in aortic ratio > or = 5% had a relative risk of an aortic complication of 2.7 and 4.1, respectively (95% confidence limits 1.5 to 4.8 and 1.8 to 9.3). Only one of 31 patients with an initial aortic ratio of < 1.3 and a rate of change of < 5% had an event (five year event free survival 97%). CONCLUSIONS: A low risk subgroup of patients with Marfan's syndrome can be identified as those with an aortic ratio < 1.3 and an annual change in aortic ratio of < 5%. These findings are helpful in optimising echocardiographic monitoring and risk stratification of patients with Marfan's syndrome.

Gender differences in left ventricular function at rest and with exercise in asymptomatic aortic stenosis.

In 29 women and 53 men with asymptomatic aortic stenosis, two-dimensional (2-D) and Doppler echocardiography were performed at rest and immediately after treadmill exercise testing to examine gender differences in left ventricular geometry, systolic and diastolic function, functional status, and exercise capacity. Aortic stenosis severity was similar between men and women. Women reported more functional impairment than men (88% +/- 14% vs 95% +/- 7%; p = 0.02). When indexed to body surface area, women had a smaller end-diastolic volume (39 +/- 14 vs 50 +/- 15 ml/m2; p = 0.002), end-systolic volume (13 +/- 6 ml/m2 vs 18 +/- 9 ml/m2; p = 0.01) and left ventricular mass (73 +/- 26 gm/m2 vs 84 +/- 21 gm/m2; p = 0.05), but a higher relative wall thickness in systole (1.5 +/- 0.4 cm vs 1.3 +/- 0.4 cm; p = 0.05), and fractional shortening (43% +/- 7% vs 39% +/- 10%; p = 0.03). Women had higher early and late transmitral velocities than did men (early, 92 +/- 24 cm/sec vs 79 +/- 29 cm/sec; p = 0.05; late, 97 +/- 30 cm/sec vs 68 +/- 23 cm/sec; p < 0.0001), a higher time-velocity integral in early diastole (18.2 +/- 4.8 cm vs 15.1 +/- 4.3 cm; p = 0.006), a significantly shorter exercise duration (4.5 +/- 4.1 minutes vs 8.0 +/- 3.9 minutes; p < 0.0001), a greater degree of functional aerobic impairment (25% +/- 48% vs 2% +/- 33%; p = 0.02), and a smaller increase in cardiac output with exercise (5.4 +/- 3.5 L/min vs 8.0 +/- 4.3 L/min; p = 0.01), in spite of similar peak heart rate and blood pressure responses. In these asymptomatic subjects with aortic stenosis, women had smaller, relatively hypercontractile ventricles, a different diastolic filling profile, more exercise limitation, and poorer functional capacity. These findings demonstrate the importance of gender in the response of the left ventricle to chronic pressure overload.

Fiberoptic cardioscopy under cardiopulmonary bypass: potential for cardioscopic surgery?

Attempts at cardioscopy have been hampered by the inability to see through blood. We describe a new method of intracardiac fiberscopic visualization performed in sheep using cardiopulmonary bypass, asanguineous cardioplegic arrest, and replacement of intracardiac blood with a clear fluid. Right heart endoscopic visualization was achieved in 4 sheep using a method that could allow extrapolation to a percutaneous approach. Two of these animals were weaned successfully from cardiopulmonary bypass. Venting and flushing aspects of the procedure were of primary importance. Further development of this technique may open the way to percutaneous endoscopically guided intracardiac operations in humans.