Dominic Y. Leung

Comparison of Aortic Root Dimensions and Geometries Before and After Transcatheter Aortic Valve Implantation by 2- and 3-Dimensional Transesophageal Echocardiography and Multislice Computed Tomography

Background—3D transesophageal echocardiography (TEE) may provide more accurate aortic annular and left ventricular outflow tract (LVOT) dimensions and geometries compared with 2D TEE. We assessed agreements between 2D and 3D TEE measurements with multislice computed tomography (MSCT) and changes in annular/LVOT areas and geometries after transcatheter aortic valve implantations (TAVI). Methods and Results—Two-dimensional circular (&pgr;×r2), 3D circular, and 3D planimetered annular and LVOT areas by TEE were compared with “gold standard” MSCT planimetered areas before TAVI. Mean MSCT planimetered annular area was 4.65±0.82 cm2 before TAVI. Annular areas were underestimated by 2D TEE circular (3.89±0.74 cm2, P<0.001), 3D TEE circular (4.06±0.79 cm2, P<0.001), and 3D TEE planimetered annular areas (4.22±0.77 cm2, P<0.001). Mean MSCT planimetered LVOT area was 4.61±1.20 cm2 before TAVI. LVOT areas were underestimated by 2D TEE circular (3.41±0.89 cm2, P<0.001), 3D TEE circular (3.89±0.94 cm2, P<0.001), and 3D TEE planimetered LVOT areas (4.31±1.15 cm2, P<0.001). Three-dimensional TEE planimetered annular and LVOT areas had the best agreement with respective MSCT planimetered areas. After TAVI, MSCT planimetered (4.65±0.82 versus 4.20±0.46 cm2, P<0.001) and 3D TEE planimetered (4.22±0.77 versus 3.62±0.43 cm2, P<0.001) annular areas decreased, whereas MSCT planimetered (4.61±1.20 versus 4.84±1.17 cm2, P=0.002) and 3D TEE planimetered (4.31±1.15 versus 4.55±1.21 cm2, P<0.001) LVOT areas increased. Aortic annulus and LVOT became less elliptical after TAVI. Conclusions—Before TAVI, 2D and 3D TEE aortic annular/LVOT circular geometric assumption underestimated the respective MSCT planimetered areas. After TAVI, 3D TEE and MSCT planimetered annular areas decreased as it assumes the internal dimensions of the prosthetic valve. However, planimetered LVOT areas increased due to a more circular geometry.

Prognostic implications of left artial spontaneous echo contrast in nonvalvular atrial fibrillation

OBJECTIVES This study examined the influence of left atrial spontaneous echo contrast on the subsequent stroke or embolic event rate and on survival in patients with nonvalvular atrial fibrillation. BACKGROUND Left atrial spontaneous echo contrast is associated with atrial fibrillation and a history of previous stroke or other embolic events. However, the prognostic implications of spontaneous contrast in patients with nonvalvular atrial fibrillation are unknown. METHOD The study group comprised 272 consecutive patients with nonvalvular atrial fibrillation undergoing transesophageal echocardiography. Clinical and echocardiographic data were collected at baseline, and patients were prospectively followed up, and all strokes, other embolic events and deaths were documented. The relation between spontaneous contrast at baseline and subsequent stroke, other embolic events and survival was analyzed. RESULTS Left atrial spontaneous echo contrast was detected at baseline in 161 patients (59%). The mean follow-up was 17.5 months. The stroke or other embolic event rate was 12%/year (15 strokes, 3 transient ischemic attacks, 2 peripheral embolisms) in patients with, compared with 3%/year (5 strokes) in patients without, baseline spontaneous contrast (p = 0.002). In 149 patients without previous thromboembolism, the event rate was 9.5%/year in patients with and 2.2%/year in patients without spontaneous contrast (p = 0.003). There were 25 deaths in patients with and 11 deaths in patients without spontaneous contrast. Patients with spontaneous contrast had significantly reduced survival (p = 0.025). On multivariate analysis, spontaneous contrast was the only positive predictor (odds ratio 3.5, p = 0.03) and warfarin therapy on follow-up the only negative predictor (odds ratio 0.23, p = 0.02) of subsequent stroke or other embolic events. CONCLUSIONS Transesophageal echocardiography can risk stratify patients with nonvalvular atrial fibrillation by identifying left atrial spontaneous echo contrast. These patients have both a significantly higher risk of developing stroke or other embolic events and a reduced survival, and they may represent a subgroup in whom the risk/benefit ratio of anticoagulation may be most favorable.

Exclusion of atrial thrombus by transesophageal echocardiography does not preclude embolism after cardioversion of atrial fibrillation. A multicenter study.

BACKGROUND Transesophageal echocardiography (TEE) has been used recently to detect atrial thrombi before cardioversion of atrial arrhythmias. It has been assumed that embolic events after cardioversion result from embolism of preexisting atrial thrombi that are accurately detected by TEE. This study examined the clinical and echocardiographic findings in patients with embolism after cardioversion of atrial fibrillation despite exclusion of atrial thrombi by TEE. METHODS AND RESULTS Clinical and echocardiographic data in 17 patients with embolic events after TEE-guided electrical (n = 16) or pharmacological (n = 1) cardioversion were analyzed. All 17 patients had nonvalvular atrial fibrillation, including four patients with lone atrial fibrillation. TEE before cardioversion showed left atrial spontaneous echo contrast in five patients and did not show atrial thrombus in any patient. Cardioversion resulted in return to sinus rhythm without immediate complication in all patients. Thirteen patients had cerebral embolic events and four patients had peripheral embolism occurring 2 hours to 7 days after cardioversion. None of the patients were therapeutically anticoagulated at the time of embolism. New or increased left atrial spontaneous echo contrast was detected in four of the five patients undergoing repeat TEE after cardioversion including one patient with a new left atrial appendage thrombus. CONCLUSIONS Embolism may occur after cardioversion of atrial fibrillation in inadequately anticoagulated patients despite apparent exclusion of preexisting atrial thrombus by TEE. These findings suggest de novo atrial thrombosis after cardioversion or imperfect sensitivity of TEE for atrial thrombi and suggest that screening by TEE does not obviate the requirement for anticoagulant therapy at the time of and after cardioversion. A randomized clinical trial is needed to compare conventional anticoagulant management with a TEE-guided strategy including anticoagulation after cardioversion.

Findings from left ventricular strain and strain rate imaging in asymptomatic patients with type 2 diabetes mellitus

Regional left ventricular (LV) myocardial functional changes in early diabetic cardiomyopathy have not been well documented. LV multidirectional strain and strain rate analyses by 2-dimensional speckle tracking were used to detect subtle myocardial dysfunction in 47 asymptomatic, male patients (age 57 +/- 6 years) with type 2 diabetes mellitus. The results were compared to those from 53 male controls matched by age, body mass index, and body surface area. No differences were found in the LV end-diastolic volume index (40.7 +/- 8.9 vs 44.1 +/- 7.8 ml/m(2), p = NS), end-systolic volume index (16.0 +/- 4.8 vs 17.8 +/- 4.3 ml/m(2), p = NS), ejection fraction (61.0 +/- 5.5% vs 59.8 +/- 5.3%, p = NS). The transmitral E/A (0.95 +/- 0.21 vs 1.12 +/- 0.32, p = 0.007) and pulmonary S/D (1.45 +/- 0.28 vs 1.25 +/- 0.27, p = 0.001) ratios were more impaired in the patients with diabetes mellitus. Importantly, the diabetic patients had impaired longitudinal, but preserved circumferential and radial systolic and diastolic, function. Diabetes mellitus was an independent predictor for longitudinal strain, systolic strain rate and early diastolic strain rate on multiple linear regression analysis (all p <0.001). In conclusion, the LV longitudinal systolic and diastolic function were impaired, but the circumferential and radial functions were preserved in patients with uncomplicated type 2 diabetes mellitus.

Cardioversion guided by transesophageal echocardiography: The ACUTE Pilot Study : A Randomized, controlled trial

A trial fibrillation is characterized by a lack of organized electrical and mechanical atrial activity that results in an irregular heartbeat and increased risks for congestive heart failure, thromboembolism, and death [1-3]. Since 1962, direct-current cardioversion has been used to restore sinus rhythm in patients with atrial fibrillation [4]. However, successful cardioversion, with the sudden resumption of sinus rhythm, is itself associated with an increased risk for embolic stroke, which can result when thrombi in the left atrial appendage are dislodged [5-12]. Transesophageal echocardiography (TEE) is an excellent method with which to detect thrombi in the left atrial appendage [13-19]. Its use has therefore been proposed as a way to allow cardioversion to be done earlier and more safely than would be possible with conventional therapy, which consists of a total of 7 weeks of treatment with warfarin [14-23]. Recent studies [15-19] indicate that TEE-guided cardioversion with short-term anticoagulation therapy may have several advantages over the conventional approach. These advantages include a decreased risk for embolism, which results from the avoidance of cardioversion in patients who have thrombi in the left atrial appendage [15]; a decreased risk for bleeding, which occurs because anticoagulation therapy can be briefer [19]; greater initial conversion to and long-term maintenance of sinus rhythm, which result from doing cardioversion earlier [18, 19]; and greater cost-effectiveness, which results from the decreased incidence of embolic stroke [17]. The ACUTE (Assessment of Cardioversion Using Transesophageal Echocardiography) Pilot Study was a multicenter, randomized clinical trial designed to compare TEE-guided cardioversion with conventional management of cardioversion in patients with atrial fibrillation who have cardioversion [19]. The study had two objectives: to assess the general feasibility of a TEE-guided approach to cardioversion and to determine the general safety of the TEE-guided approach by comparing its clinical outcome with those of conventional management. Methods Patient Selection Patients who were candidates for electrical cardioversion were eligible for inclusion if they had atrial fibrillation, or atrial flutter with a history of atrial fibrillation, lasting longer than 2 days. Patients were excluded if they had received anticoagulant therapy for more than 7 days, had required urgent cardioversion as a result of hemodynamic instability, had had a cardioembolic event within the previous month, had contraindications to TEE or warfarin, were women with childbearing potential in whom pregnancy could not be excluded, were unable to give informed consent, or were unable to return for a follow-up visit. Our study protocol was approved by the institutional review boards at all clinical sites, and all patients provided written informed consent in advance. Study Protocol Patients who met the inclusion criteria were randomly assigned to receive either a conventional or a TEE-guided approach to cardioversion. Randomization was done using presealed, opaque envelopes that were computer generated and distributed to each clinical site (Figure 1). Random assignments were stratified by site and were generated in blocks of six. Figure 1. The ACUTE (Assessment of Cardioversion Using Transesophageal Echocardiography) study protocol. The conventional approach to cardioversion was that recommended by the American College of Chest Physicians: 3 weeks of therapeutic warfarin therapy, then cardioversion, then 4 weeks of warfarin therapy, and then a follow-up examination at the end of the 4 weeks [23]. Prothrombin times were monitored regularly, and the target international normalized ratio (INR) was 2 to 3. If assigned to the TEE group, patients began receiving anticoagulation therapy at their initial visit. The goal was to have patients therapeutically anticoagulated (therapeutic anticoagulation was defined as a partial thromboplastin time 1.5 to 2.5 times control values or an INR of 2.0 to 3.0) at the time of and after the planned cardioversion, for a total of 4 weeks of therapy. The initial choice of antithrombotic agent was determined by whether the patient was an inpatient or an outpatient at the time of randomization: Heparin was used for inpatients; warfarin was administered to outpatients. Transesophageal echocardiography, with subsequent cardioversion within 24 hours, was then scheduled as soon as stable therapeutic anticoagulation was assured. For example, if a patient was hospitalized and intravenous heparin therapy was administered, TEE was done as soon as a stable therapeutic partial thromboplastin time could be documented (for 24 to 36 hours); subsequent cardioversion was done if the presence of a thrombus was excluded. A 4- to 5-day overlap of warfarin therapy and intravenous heparin therapy was often necessary to maintain adequate anticoagulation after cardioversion. If the patient was to be managed as an outpatient, warfarin therapy was initiated on the day of study enrollment, and TEE and subsequent possible cardioversion were scheduled for at least 5 to 7 days later. Again, cardioversion was done when the patient was therapeutically anticoagulated, and all patients received maintenance therapy with warfarin for 4 weeks after cardioversion [15]. In the TEE group, cardioversion was done immediately after or within 24 hours of TEE because of the potential for thrombus formation in the period between TEE and cardioversion. If thrombi were detected in the left or right atrial appendages or atrial cavities, cardioversion was postponed and the patient received warfarin therapy for 4 weeks. After 4 weeks, TEE was repeated and, if no thrombus was detected, cardioversion was done. If a thrombus was still present, another 4-week course of warfarin therapy was administered and cardioversion was not done [15]. Clinical Outcomes Our feasibility outcomes were frequency of cardioversion, frequency of cardioversion occurring as scheduled, time to cardioversion, and time to sinus rhythm. Our clinical safety outcomes were clinically apparent ischemic stroke, transient ischemic attack, systemic embolization, deaths related to cardioversion or episodes of bleeding, and detected episodes of clinical hemodynamic instability (worsening congestive heart failure or hypotension) that rendered the patient unable to complete the protocol. Other outcome variables were the prevalence of thrombi, the number of patients without thrombi who had early cardioversion, and the immediate and follow-up rhythms after cardioversion. These outcomes were assessed for as long as 4 weeks after cardioversion but for no longer than 8 weeks after randomization. In the patients who did not have cardioversion and who spontaneously reverted to sinus rhythm, the variables were assessed at 4 weeks after spontaneous reversion. Study Organization and Procedures The administrative organization of the pilot study is described in the Appendix. Echocardiographic Examination Conventional transthoracic echocardiography was done in both study groups using commercially available equipment. In the TEE group, TEE was done according to standard techniques using phased-array biplane or multiplane transducers [24-26]. Complete transesophageal echocardiographic examination was done, and special attention was paid to imaging the left and right atria and left and right atrial appendages to assess the presence or absence of thrombi and spontaneous echo contrast. Echocardiographic Data Analysis Two-dimensional directed M-mode transthoracic echocardiography was used to derive the left ventricular septal and posterior wall thicknesses and the end-diastolic, end-systolic, and left atrial dimensions. Ejection fraction was calculated using standard techniques [27, 28]. The maximal left atrial and right atrial areas were planimetered on-line, and the severity of mitral regurgitation was qualitatively graded from 0 to 4+ by using color-flow mapping [29]. A thrombus was considered to be present if a mass detected in the appendage or body of the atrium appeared to be distinct from the underlying endocardium, was not caused by pectinate muscles, and was detected in more than one imaging plane. The presence or absence of spontaneous echo contrast was analyzed and defined as dynamic intracavitary echoes with a characteristic swirling pattern distinct from artifact. The degree of spontaneous echo contrast was categorized independently as absent, mild, or severe [30, 31]. Quality Control Measures Standard definitions of echocardiographic measurements were available to all of the clinical centers as part of a pilot operations manual. Echocardiograms at each clinical center were interpreted locally by a single physician who was highly experienced in echocardiography. Videotapes that showed the results of the first five echocardiographic examinations and all videotapes that showed thrombi were forwarded from the clinical centers to a central laboratory and overread by three experienced reviewers for consensus [19]. Electrical Cardioversion Cardioversion was done by using the standard method of Lown and associates [4] with an initial energy of at least 40 J for atrial flutter and 200 J for atrial fibrillation. Statistical Analysis Summaries of clinical, echocardiographic, and outcome data are expressed as means or frequencies with 95% CIs. Data that were not normally distributed were log-transformed and presented as geometric means. Outcomes were compared for the TEE and conventional therapy groups, for patients with and without thrombus (in the TEE group only), and for patients in the TEE and conventional therapy groups who had cardioversion. These analyses were done using the t-test for independent groups for continuous variables and the Fisher exact test for categorical variables. StatXact (Cytel Software, Cambridge, Massachusetts) was used to compute binary CIs; SAS softwar

Echocardiographic evaluation of left atrial size and function: Current understanding, pathophysiologic correlates, and prognostic implications

Left atrial (LA) volume has recently been identified as a potential biomarker for cardiac and cerebrovascular disease. However, evidence regarding the prognostic implications of LA volume still remains unclear. Evaluation of LA size and function using traditional and more recent echocardiographic parameters is potentially feasible in the routine clinical setting. This review article discusses the conventional and newer echocardiographic parameters used to evaluate LA size and function. Conventional parameters include the assessment of phasic atrial activity using atrial volume measurements, transmitral Doppler peak A velocity, atrial fraction, and the atrial ejection force. Newer parameters include Doppler tissue imaging (DTI) including segmental atrial function assessment using color DTI, strain, and strain rate. In addition, an overview of the implications and clinical relevance of the findings of an enlarged left atrium, from currently available literature, is presented.

Left ventricular function after valve repair for chronic mitral regurgitation: Predictive value of preoperative assessment of contractile reserve by exercise echocardiography

OBJECTIVES We evaluated the value of preoperative assessment of left ventricular contractile reserve in predicting ventricular function after valve repair for minimally symptomatic mitral regurgitation. BACKGROUND The optimal timing for operation in minimally symptomatic patients with significant mitral regurgitation is controversial. Accurate preoperative assessment of left ventricular function is difficult, and the ability to predict postoperative function is limited. Previous studies in patients undergoing mitral valve replacement may not be applicable in the present era of valve repair. METHODS We performed exercise echocardiography in 139 patients with isolated mitral regurgitation and no coronary disease, 74 of whom subsequently underwent uncomplicated valve repair. We measured rest left ventricular end-systolic dimension, end-systolic wall stress and positive first derivative of left ventricular pressure (dP/dt). End-diastolic and end-systolic volumes and ejection fraction were measured preoperatively at rest, immediately after exercise and postoperatively. RESULTS Ejection fraction decreased postoperatively to 55 +/- 10% from a rest preoperative value of 64 +/- 9% (p < 0.001). Compared with patients with a postoperative ejection fraction > or = (n = 56), patients with postoperative ejection fraction < 50% (n = 18) had a significantly lower preoperative exercise ejection fraction (57 +/- 11% vs. 73 +/- 9%, p < 0.0005), a larger exercise end-systolic volume index (32 +/- 8 vs. 18 +/- 7 cm3/m2, p < 0.0005) and a lower change in ejection fraction with exercise (-4 +/- 8% vs. 9 +/- 10%, p < 0.005). Preoperative rest indexes, including dP/dt, end-systolic wall stress and end-systolic volume index were less predictive, whereas exercise capacity, rest ejection fraction and end-systolic dimension were not predictive of post-repair ejection fraction. An exercise end-systolic volume index > 25 cm3/m2 was the best predictor of postoperative dysfunction, with a sensitivity and specificity of 83%. CONCLUSIONS In minimally symptomatic patients with mitral regurgitation, latent ventricular dysfunction may be indicated by a limited contractile reserve, manifest at exercise as an inadequate increase in ejection fraction and a larger end-systolic volume. These variables may also be used to predict left ventricular function after repair.

Compensatory changes in atrial volumes with normal aging: is atrial enlargement inevitable?

OBJECTIVES The aim of this study was to evaluate left atrial volume and its changes with the phases (active and passive) of atrial filling, and to examine the effect of normal aging on these parameters and pulmonary vein (PV) flow patterns. BACKGROUND Atrial volume change with normal aging has not been adequately described. Pulmonary vein flow patterns have not been volumetrically evaluated in normal aging. Combining atrial volumes and PV flow patterns obtained using transthoracic echocardiography could estimate shifts in left atrial mechanical function with normal aging. METHODS A total of 92 healthy subjects, divided into two groups: Group Y (young <50 years) and Group O (old > or =50 years), were prospectively studied. Maximal (Vol(max)) and minimal (Vol(min)) left atrial volumes were measured using the biplane method of discs and by three-dimensional echocardiographic reconstruction using the cubic spline interpolation algorithm. The passive filling, conduit, and active emptying volumes were also estimated. Traditional measures of atrial function, mitral peak A-wave velocity, velocity time integral (VTI), atrial emptying fraction, and atrial ejection force were measured. RESULTS As age increased, Vol(max), Vol(min), and total atrial contribution to left ventricle (LV) stroke volume were not significantly altered. However, the passive emptying volume was significantly higher (14.2 +/- 6.4 ml vs. 11.6 +/- 5.7 ml; p = 0.03) whereas the active emptying volume was lower (8.6 +/- 3.7 ml vs. 10.2 +/- 3.8 ml; p = 0.04) in Group Y versus Group O. Pulmonary vein flow demonstrated an increase in peak diastolic velocity (Group Y vs. Group O) with no corresponding change in diastolic VTI or systolic fraction. CONCLUSIONS Normal aging does not increase maximum (end-systolic) atrial size. The atrium compensates for changes in LV diastolic properties by augmenting active atrial contraction. Pulmonary vein flow patterns, although diastolic dominant using peak velocity, demonstrated no volumetric change with aging.

Functional and prognostic implications of left ventricular contractile reserve in patients with asymptomatic severe mitral regurgitation

Objective: To evaluate contractile reserve (CR) determined by exercise echocardiography in predicting clinical outcome and left ventricular (LV) function in asymptomatic severe mitral regurgitation (MR). Design: Cohort study. Setting: Regional cardiac centre. Patients and outcome measures: LV volumes and ejection fraction (EF) were measured at rest and after stress in 71 patients with isolated MR. During follow up (mean (SD) 3 (1) years), EF and functional capacity were serially assessed and cardiac events (cardiac death, heart failure, and new atrial fibrillation) were documented. Results: CR was present in 45 patients (CR+) and absent in 26 patients (CR−). Age, resting LV dimensions, EF, and MR severity were similar in both groups. Mitral surgery was performed in 19 of 45 (42%) CR+ patients and 22 of 26 (85%) CR− patients. In patients undergoing surgery, CR was an independent predictor of follow up EF (p  =  0.006) and postoperative LV dysfunction (EF < 50%) persisted in five patients, all in the CR− group. Event-free survival was lower in surgically treated patients without CR (p  =  0.03). In medically treated patients, follow up EF was preserved in those with intact CR but progressively deteriorated in patients without CR, in whom functional capacity also deteriorated. Conclusions: Evaluation of CR by exercise echocardiography may be useful for risk stratification and may help to optimise the timing of surgery in asymptomatic severe MR.

Alterations in multidirectional myocardial functions in patients with aortic stenosis and preserved ejection fraction: a two-dimensional speckle tracking analysis

AIMS To identify changes in multidirectional strain and strain rate (SR) in patients with aortic stenosis (AS). METHODS AND RESULTS A total of 420 patients (age 66.1 ± 14.5 years, 60.7% men) with aortic sclerosis, mild, moderate, and severe AS with preserved left ventricular (LV) ejection fraction [(EF), ≥50%] were included. Multidirectional strain and SR imaging were performed by two-dimensional speckle tracking. Patients were more likely to be older (P < 0.001) and at a worse New York Heart Association functional class (P < 0.001) with increasing AS severity. There was a progressive stepwise impairment in longitudinal, circumferential, and radial strain and SR with increasing AS severity (all P < 0.001). The myocardial dysfunction appeared to start in the subendocardium with mild AS, to mid-wall dysfunction with moderate AS, and eventually transmural dysfunction with severe AS. Aortic valve area, as a measure of AS severity, was an independent determinant of multidirectional strain and SR on multiple linear regressions. CONCLUSIONS Patients with AS have evidence of subclinical myocardial dysfunction early in the disease process despite normal LVEF. The myocardial dysfunction appeared to start in the subendocardium and progressed to transmural dysfunction with increasing AS severity. Symptomatic moderate and severe AS patients had more impaired multidirectional myocardial functions compared with asymptomatic patients.