Quantification of mitral regurgitation in the cardiac catheterization laboratory with contrast echocardiography.

BACKGROUND: There is no method of quantifying the severity of mitral regurgitation (MR) from injection of tracer directly into the left ventricular (LV) cavity, a method commonly used in the cardiac catheterization laboratory. METHODS AND RESULTS: We used a previously validated mathematical model that derives regurgitant fraction (RF) from the relative tracer washout from the left atrial (LA) and LV cavities. Thirty-nine patients referred for diagnostic cardiac catheterization with clinical evidence of possible MR were included in the study. Five milliliters of a microbubble mixture was power-injected into the LV during simultaneously performed contrast echocardiography. Relative changes in background-subtracted video intensity were measured from the LV and LA, and the resultant model-derived RF was correlated with the severity of MR on cineangiography. The severity of MR ranged from 0 to 4+ on cineangiography with corresponding model-derived RF of 0 to 0.69 on contrast echocardiography. A close linear relation was noted between angiographic severity of MR and model-derived RF on contrast echocardiography (y = 0.1x + 0.03, r = 0.89, P <.001). Contrast echocardiography was more sensitive than cineangiography for detecting mild MR. CONCLUSIONS: We describe a new method of measuring the severity of MR in the cardiac catheterization laboratory. Apart from being quantitative, this method can be safely used during cardiac catheterization in patients in whom iodinated contrast agents may be potentially harmful.

Ordering an echocardiogram for evaluation of left ventricular function: level of expertise necessary for efficient use.

This prospective study was performed to test the hypothesis that the yield of 2-dimensional echocardiography (2DE) would be higher when it is ordered by a cardiologist than by a noncardiologist. Patients referred for transthoracic 2DE for the evaluation of left ventricular systolic function for the 11-month period between July 10, 1995, and June 10, 1996, were included in the study. Demographic, historical, and clinical findings were recorded. Whether the patient was referred by a cardiologist versus a noncardiologist was used as the predictor variable in a binary logistic regression analysis. To address the possibility that the yield of 2DE may be higher for cardiologists because the prevalence of disease in patients referred to them may be higher (selection bias), the analysis was subjected to a propensity score adjustment. Of 2176 patients referred for 2DE during the study, 1033 were referred for the evaluation of left ventricular function. The test had a positive yield in 52% of patients for cardiologists versus 31% for noncardiologists (chi(2) = 45.5, P <.0001, odds ratio 2.4 [CI = 1. 9-3.1]). This difference remained highly significant even when propensity score risk adjustment was made (chi(2) = 54.2, P <.0001, odds ratio 2.0 [CI = 1.5-2.8]). We conclude that the yield of 2DE is higher for cardiologists compared with noncardiologists and that this result was not related to differences in patient populations examined by the two groups. Thus, more efficient use of 2DE may be achieved if patients are referred to cardiologists rather than directly sent for 2DE.

Assessment of resting perfusion with myocardial contrast echocardiography: theoretical and practical considerations.

BACKGROUND: The aim of this study was to perform a quantitative comparison between myocardial contrast echocardiography (MCE) and single-photon emission computed tomography (SPECT) in patients with prior myocardial infarction (MI). We also wanted to determine the optimal method for the intravenous administration of an ultrasound contrast agent in the clinical setting. METHODS AND RESULTS: Seventeen patients with resting perfusion defects in a single vascular territory on SPECT were studied. MCE was performed with intermittent harmonic imaging during continuous infusions of a second-generation ultrasound contrast agent (Sonovue, Bracco Diagnostics) in all 17 patients and after bolus injection in 8 of them. During continuous infusions, the video intensity (VI) ratio between the abnormal and normal myocardium at a pulsing interval (PI) of 8 cardiac cycles correlated well with the activity ratio between these segments on SPECT (r = 0.73, P <.01). When information regarding microbubble velocity (MV) denoted as change in VI with increasing PIs was added, the correlation with SPECT activity ratio improved (P <.05) significantly (r = 0.87, P <.0001). Higher microbubble doses resulted in higher VI during continuous infusions with good myocardial opacification and no far-field attenuation until the highest dose was reached. With bolus injections, the VI ratio between the abnormal and normal myocardium at PI of 1 and 5 cardiac cycles showed a modest correlation (r = 0.46 and r = 0.48, respectively, P <.05) with activity ratios between these regions on SPECT. When a dose of microbubbles administered as a bolus produced adequate myocardial opacification, it invariably resulted in far-field attenuation. CONCLUSIONS: In patients with prior MI, quantitative assessment of resting perfusion defects on MCE correlates well with regional activity on SPECT. Continuous infusions offer an advantage over bolus injections because they can provide an assessment of both relative VI and MV. Adjustment of the microbubble infusion rate produces adequate myocardial opacification without attenuation.

Enhancement of left ventricular cavity opacification by harmonic imaging after venous injection of Albunex.

Venous injection of Albunex does not consistently produce left ventricular (LV) cavity opacification during conventional echocardiography. We postulated that by increasing the signal-to-noise ratio, harmonic imaging will result in more successful LV cavity opacification and provide a better assessment of regional LV systolic function. Forty-two patients with poor baseline endocardial delineation were given 10 ml intravenous injections of Albunex during continuous fundamental and harmonic imaging. Change in segmental wall-thickening scores and the confidence levels for these scores were assessed for 3 observers with various levels of experience. Compared with fundamental imaging, harmonic imaging significantly improved the success of LV cavity opacification (83% vs 62%, p <0.05). The background-subtracted video intensity within the central two thirds of the LV cavity increased threefold (from 10 +/- 15 to 31 +/- 29, p <0.05) with harmonic imaging. The spatial extent of opacification increased from 40% of the LV cavity during fundamental imaging to 65% with harmonic imaging (p <0.001). The confidence level for assessing regional LV systolic function improved (p <0.05) after contrast administration, particularly when observer experience was limited. We conclude that in patients with poor endocardial definition, injection of intravenous Albunex should be combined with harmonic imaging to improve LV cavity opacification.

Role of echocardiography in the evaluation and management of atrial fibrillation.

This article reviews the utility of transthoracic echocardiography and transesophageal echocardiography for patients with atrial fibrillation and focuses on evidence that these diagnostic techniques can aid in the achievement of these goals. Following a brief review of common findings from each of these techniques, the relevance of specific results to the management of atrial fibrillation is assessed.

Aortocaval fistula complicating abdominal aortic aneurysm: case report and literature review.

Aortocaval fistula is a rare complication of abdominal aortic aneurysm involving less than 1% of all abdominal aortic aneurysms. The diagnosis is difficult, and preoperative identification can be challenging. We describe an interesting case of a 72-year-old man presenting with acute-onset dyspnea who was found to have an aortocaval fistula secondary to a large abdominal aortic aneurysm. The clinical features that exemplify aortocaval fistula are discussed and the literature reviewed.

Diagnostic value of echocardiography in suspected endocarditis. An evaluation based on the pretest probability of disease.

BACKGROUND: We hypothesized that for the diagnosis of endocarditis, (1) transthoracic echocardiography (TTE) would be most valuable in patients with an intermediate clinical probability of the disease and (2) transesophageal echocardiography (TEE) would be most useful in patients with an intermediate probability when TTE either does not yield an adequate study or indicates an intermediate probability of endocarditis. We also sought to investigate the influence of echocardiographic results on antibiotic usage and its duration. METHODS AND RESULTS: TTE and TEE were performed in 105 consecutive patients with suspected endocarditis. Patients were classified as having either low, intermediate, or high probability of endocarditis on the basis of clinical criteria and separately on the basis of both TTE and TEE findings. TTE and TEE classified the majority (82% and 85%, respectively) of the 67 patients with a low clinical probability of endocarditis as having a low likelihood of the disease. Of the 14 patients with intermediate clinical probability, 12 had technically adequate TTE studies; 10 of these (83%) were classified as either high or low probability. All patients with intermediate clinical probability were classified as high or low probability by TEE. The majority of the 24 patients with high clinical probability were placed in the low-likelihood category by echocardiography (15 by TTE and 12 by TEE). There was concordance between TTE and TEE in 83% of all cases. TEE was useful for the diagnosis of endocarditis in patients with prosthetic valves and in those in whom TTE indicated an intermediate probability; these constituted < 20% of patients in our study. The course of antibiotic therapy was influenced only by the clinical profile and not by the echocardiographic results. CONCLUSIONS: Echocardiography should not be used to make a diagnosis of endocarditis in those with a low clinical probability of the disease. In those with an intermediate or high clinical probability, TTE should be the diagnostic procedure of choice. TEE for the diagnosis of endocarditis should be reserved only for patients who have prosthetic valves and in whom TTE is either technically inadequate or indicates an intermediate probability of endocarditis.

Mechanism of mitral leaflet excursion.

The factors that influence the extent of mitral leaflet opening (MLO) and closure (MLC) have not been defined. We hypothesized that left ventricular (LV) systolic function determines the rate of increase of the early diastolic left atrial (LA)-LV pressure gradient, which is responsible for the extent of MLO, and also the rate of change of the early systolic LV-LA pressure gradient, which determines the degree of MLC. Accordingly, global LV function was changed by altering left main coronary artery flow with LA pressure held relatively constant. LV end-systolic dimension and peak positive LV rate of pressure development (dP/dt) correlated best with the degrees of MLO and MLC, with average correlation coefficients of 0.88 and 0.68, and 0.86 and 0.72, respectively. Although transsecting the submitral apparatus resulted in flailing of the mitral leaflets during normal LV systolic function, the extents of MLO and MLC during LV systolic dysfunction were still influenced by LV systolic function. It is concluded that LV systolic function determines the extent (both opening and closure) of mitral leaflet excursion.

Removal of an infected right atrial mass in a patient with sickle cell disease.

The use of indwelling central catheters for hyperalimentation, chemotherapy, and long-term venous access is increasing. We report the successful removal of an infected right atrial mass associated with the use of a central catheter in an adult with sickle cell disease. The clinical options for the treatment of infected atrial thrombus as well as the challenge of performing cardiopulmonary bypass in patients with sickle cell disease are briefly discussed.

The effect of epidural anesthesia on safety and success of external cephalic version at term.

The purpose of this study was to assess the effect of epidural anesthesia on the success and safety of external cephalic version (ECV) performed at term. A retrospective record review of all pregnant women > 36 wk gestation who had attempts at ECV at Arnold Palmer Hospital for Children and Women between April 2, 1992, and April 30, 1993, was performed. The standard contraindications to ECVs were observed, and the use of tocolytics and lumbar epidural anesthesia was based on personal preference of the patient's physician. Sixty-one patients underwent 69 attempts, with eight patients having two attempts. There were 37 attempts without epidural and 32 with epidural. Four (10%) and 11 (34%) of the no epidural and epidural groups, respectively, were either in labor or had a cervical dilation > 3 cm at the time of the attempt. The other major patient variables likely to affect the success of ECV were not different between the groups, with the exception of a higher percentage of attempts by the housestaff in the epidural group. The success rate was 59% and 24% for the epidural group and no epidural group, respectively (P < 0.05). The incidence of abruptio placentae, fetal bradycardia, low Apgar scores, and low umbilical artery pH was similar. In our patient population, regional anesthesia increased the success rate of ECV and decreased the cesarean delivery rate with no apparent ill effect on perinatal or maternal morbidity or mortality.

Starr-Edwards valve thrombosis detected preoperatively by transesophageal echocardiography.

A 31-year-old woman developed increasing signs of congestive heart failure 15 years following placement of a mitral Starr-Edwards mechanical valve. A preoperative transesophageal echocardiogram (TEE) demonstrated a large, obstructive valvular thrombus and the patient underwent successful reoperative valve replacement.

A mathematical model for the quantification of mitral regurgitation. Experimental validation in the canine model using contrast echocardiography.

BACKGROUND: Because the clearance of contrast from the left atrium (LA) relative to the left ventricle (LV) depends on the degree of mitral regurgitation (MR), we hypothesized that a mathematical model can be developed that would provide a quantitative estimation of MR from the washout of contrast from these chambers. METHODS AND RESULTS: After mathematically developing the model, we performed experiments in two groups of dogs with the use of contrast echocardiography. Group 1 consisted of nine dogs in which different degrees of MR were produced by creating ischemic LV dysfunction. Contrast was injected into the LV, and MR was graded visually on a scale of from 0 to 4+. Videointensity plots generated from the LA and LV were provided to the model. There was excellent correlation between visual assessment of MR and model-derived regurgitant fraction in the 33 stages: y = 0.16x + 0.002 (r = 0.97, p less than 0.001, SEE = 0.06). To obtain a more quantitative validation, we placed electromagnetic flow probes on the aorta and just cephalad to the mitral annulus in six dogs (group 2) during cardiopulmonary bypass. Different degrees of MR were produced by chordal traction and/or myocardial ischemia. Regurgitant fraction was calculated at each stage from the flow probe and videointensity data. There was excellent correlation between flow probe and model-derived regurgitant fraction (y = 0.90x + 0.03; r = 0.96, p less than 0.001, SEE = 0.06), and close interobserver and intraobserver correlations were noted using flow probe and contrast echocardiographic data. CONCLUSIONS: A mathematical model that uses the clearance of contrast from the LA relative to the LV can be used to accurately measure the severity of MR. These findings may have important practical implications for the quantification of MR.