Beat C. Aeschbacher

Quantitation of mitral regurgitation using the systolic/diastolic pulmonary venous flow velocity ratio.

OBJECTIVES The purpose of this study was to test the hypothesis that pulmonary venous flow velocity ratios during systole and diastole in patients with mitral regurgitation (MR) correctly predict the quantitative degree of MR. BACKGROUND Pulmonary venous flow velocity measurements have thus far been used only for the qualitative assessment of MR. Recent studies have evaluated this method using transesophageal echocardiography against semiquantitative references. METHODS In 100 patients without aortic regurgitation or atrial fibrillation and with left ventricular (LV) ejection fraction >45%, MR was assessed by quantitative echocardiographic Doppler and color Doppler, providing forward and total LV stroke volume for the calculation of the mitral regurgitant fraction (RFstandard), the reference parameter, and also supplying mitral regurgitant orifice area (ROA) values and the RF by the flow convergence method (RFPISA [proximal isovelocity surface area]). Measurements of pulmonary venous flow velocity time integral values during systole to diastole (VTIs/VTId) were obtained and tested for their predictibility of ROA, RFstandard and RFPISA. RESULTS There was an inverse and significant correlation between VTIs/VTId and ROA, RFPISA and RFstandard, respectively: RFstandard=49 - 20 VTIs/VTId, r=0.77, p=0.0001. A principal source of variability in the relation between VTIs/VTId and RFstandard was the presence of mitral valve prolapse as the cause of MR. Pulmonary venous flow reversal (VTIs/VTId <0) correctly identified severe MR with 52% sensitivity, 96% specificity and 80% positive and 87% negative predictive accuracy. CONCLUSIONS The VTIs/VTId ratio allows a moderately accurate assessment of the severity of MR.

Midazolam Premedication Improves Tolerance of Transesophageal Echocardiography

Patient premedication for transesophageal echocardiography (TEE) is still under debate, especially the use of sedatives. We performed a double-blind, placebo-controlled study to clarify the efficacy of low-dose intravenous midazolam as premedication for TEE. Placebo or midazolam (< or =50 kg, 2.0 mg intravenously; 50 to 80 kg, 2.5 mg; and > or =80 kg, 3.0 mg intravenously) was given in addition to topical anesthesia to 200 consecutive in- and outpatients. Blood pressure, heart rate, and oxygen saturation were monitored. Patients were interviewed immediately, and 2 to 10 days after TEE. Sixteen patients received an additional dose of midazolam, and in 12 follow-up was incomplete. Patients taking midazolam reported less gag reflex at probe introduction and during TEE, as did the examiners (p < 0.05 to 0.0001). Probe manipulations were found to produce less discomfort after midazolam administration (p < 0.005). Midazolam patients experienced less dyspnea (p < 0.01) despite a minimal decrease in oxygen saturation of 2% (p < 0.0001). The following day patients taking midazolam reported less sore throats, and painful swallowing was less frequent (p < 0.01 to 0.001). Systolic blood pressure decreased slightly in the midazolam group (132 +/- 24 to 121 +/- 20 mm Hg, p < 0.0001). The rate of minor complications showed no difference. Thus, TEE probe introduction and manipulation was tolerated better after low-dose midazolam premedication, and patients experienced less pharyngeal discomfort the day after. Midazolam was well tolerated and the complication rate did not increase. Thus low-dose, short-acting benzodiazepine premedication improves patient comfort during and after TEE and generous use can be recommended.

Transesophageal Echocardiography to Evaluate Success of Transcatheter Closure of Large Secundum Atrial Septal Defects in Adults Using the Buttoned Device

OBJECTIVES To determine the success rate of transcatheter closure of secundum atrial septal defects (ASDs) in adults and to characterize anatomical structures predisposing to unsatisfactory results. PATIENTS AND METHODS Preinterventional and follow-up transesophageal echocardiography of 17 consecutive patients treated with a Sideris buttoned device was reviewed. Residual jet size of 5 mm or smaller was considered an adequate result; jet size larger than 5 mm was inadequate. Maximal ASD diameter, ASD area, and anterior, posterior, superior, and inferior septal rims were measured. RESULTS The 7 patients with adequate results (41%) had smaller defects before implantation of a buttoned device (mean +/- SD maximal ASD diameter, 12 +/- 4 vs 19 +/- 5 mm; P<.005). Total rim length (mean +/- SD) was longer in patients with an adequate result (71 +/- 8 vs 46 +/- 11 mm; P<.001). The ASD size and length of the superior septal rim were independent predictors for an adequate result. Only 3 patients, all with ASD diameter less than 13 mm, had completely closed defects. All patients with ASD diameter greater than 20 mm had inadequate results and an unsatisfactory device position. The defect size (mean +/- SD) was similarly reduced in patients with adequate and inadequate results (9 +/- 3 vs 8 +/- 4 mm). CONCLUSION Adults with a small ASD are more likely to have an adequate result after treatment with the buttoned device. A sufficiently large superior septal rim is particularly important for an adequate result. Most patients with a large ASD have inadequate results, although their ASD size is reduced by a similar absolute area as in patients with an adequate result.

901–49 Second Harmonic Imaging of Echocardiographic Contrast Agents: Unique Features and Promising Characteristics

Echocardiographic contrast microbubbles expand and contract rhythmically when ultrasound energy is applied to them. These oscillations generate sound waves not only at the primary or input frequency, but also at higher harmonic frequencies. Solid tissues do not generally produce strong harmonic signals, thus the detection of higher harmonic frequencies is relatively specific for echocardiographic contrast agents. We therefore examined the imaging characteristics of various contrast agents using a novel echocardiographic system producing images from second harmonic signals (Contrast Specific Imaging, Acuson). As anticipated, unenhanced tissues were poorly seen in this imaging mode, while contrast containing structures were clearly visualized. Agent-specific differences in image appearance and signal strength following contrast administration were identified. Second harmonic imaging improved detection of small concentrations of contrast. Small contrast containing structures were more clearly resolved than with conventional imaging. Intracavitary blood flow patterns were observed. Time intensity curves generated during administration of contrast media were similar for conventional and second harmonic imaging. Cardiac cycle-dependent changes in second harmonic signal intensity were noted. Conclusions Second harmonic imaging provides excellent visualization of structures containing ultrasonic contrast agents. The intensity and appearance of the contrast effect observed with the Contrast Specific Imaging system is dependent upon the size and composition of the microbubbles. Tuning of the second harmonic imaging system to the specific contrast agent may be useful to optimize contrast detection.