Systematic Assessment of the Impact of Ultrasound-Enhancing Agents upon Measurements of Cardiac Size and Function by Echocardiography.

BACKGROUND: Echocardiography with an ultrasound-enhancing contrast agent (CON) is a powerful tool for identifying the endocardial border. However, the precise relationship of measurements obtained from CON to the reference values of two-dimensional unenhanced echocardiography (BASL) remains undefined, especially regarding wall thickness. The aim of this study was to systematically determine the differences between unenhanced and enhanced images for a broad range of left ventricular (LV) measurements and to define reference values for the relationship between the two methods. METHODS: We examined the echocardiograms of 624 consecutive patients in whom CON was performed for clinical indications. We excluded 192 patients in whom studies were technically difficult for measurement by either or both methods. Echocardiograms were from standard parasternal and apical views according to American Society of Echocardiography guidelines. Recordings were measured for wall thickness and chamber dimension in 343 patients and for LV volumes and ejection fraction in 212 patients. RESULTS: LV wall thickness measurements were systematically reduced with a bias of 0.2 cm with limits of agreement (LOA) from -0.5 to 0.16 cm in interventricular septal thickness, and from -0.46 to 0.13 cm in posterior wall thickness in CON. LV dimensions and volumes systematically increased with a bias of 0.2 cm (LOA, -0.19 to 0.58 cm) and 14 to 16 mL (LOA, -11.9 to 42.8 mL), respectively. LV ejection fraction systematically decreased with a bias of 3.4% (LOA, -13.5% to 6.8%) in CON compared to BASL. All differences showed normal distribution in the Kolmogorov-Smirnov test. CONCLUSION: CON yields significantly different measurements of cardiac size and function compared to unenhanced imaging. These data define the systematic differences in measurements between CON and BASL images; the range of differences is narrow. These differences may influence management when the measurement value is a borderline.

Assessment of left atrial volume before and after pulmonary thromboendarterectomy in chronic thromboembolic pulmonary hypertension.

BACKGROUND: Impaired left ventricular diastolic filling is common in chronic thromboembolic pulmonary hypertension (CTEPH), and recent studies support left ventricular underfilling as a cause. To investigate this further, we assessed left atrial volume index (LAVI) in patients with CTEPH before and after pulmonary thromboendarterectomy (PTE). METHODS: Forty-eight consecutive CTEPH patients had pre- & post-PTE echocardiograms and right heart catheterizations. Parameters included mean pulmonary artery pressure (mPAP), pulmonary vascular resistance (PVR), cardiac index, LAVI, & mitral E/A ratio. Echocardiograms were performed 6 ± 3 days pre-PTE and 10 ± 4 days post-PTE. Regression analyses compared pre- and post-PTE LAVI with other parameters. RESULTS: Pre-op LAVI (mean 19.0 ± 7 mL/m2) correlated significantly with pre-op PVR (R = -0.45, p = 0.001), mPAP (R = -0.28, p = 0.05) and cardiac index (R = 0.38, p = 0.006). Post-PTE, LAVI increased by 18% to 22.4 ± 7 mL/m2 (p = 0.003). This change correlated with change in PVR (765 to 311 dyne-s/cm5, p = 0.01), cardiac index (2.6 to 3.2 L/min/m2, p = 0.02), and E/A (.95 to 1.44, p = 0.002). CONCLUSION: In CTEPH, smaller LAVI is associated with lower cardiac output, higher mPAP, and higher PVR. LAVI increases by ~20% after PTE, and this change correlates with changes in PVR and mitral E/A. The rapid increase in LAVI supports the concept that left ventricular diastolic impairment and low E/A pre-PTE are due to left heart underfilling rather than inherent left ventricular diastolic dysfunction.

Echocardiographic assessment of the accuracy of computed tomography in the diagnosis of hemodynamically significant pericardial effusions.

BACKGROUND: Although Doppler echocardiography is the noninvasive test of choice for the diagnosis of hemodynamically significant pericardial effusion (HSPE), pericardial effusion is often first detected by computed tomography (CT). Few data are available, however, regarding the accuracy of CT in the diagnosis of cardiac tamponade. METHODS: We retrospectively identified 28 consecutive hospitalized patients with pericardial effusion who underwent both chest CT and echocardiography within 48 hours between 2001 and 2005. CT images were analyzed by experienced radiologists without knowledge of the echo results. Radiologic findings were evaluated with Doppler echocardiography. RESULTS: Of the 28 patients, 15 had HSPE by echo criteria. Right ventricular wall flattening and pericardial thickening on CT correlated with HSPE with a positive predictive value of 79% and 67%, respectively. Inferior vena cava diameter by CT was not a useful predictor of HSPE. CT was most accurate in diagnosing HSPE when the effusions were large (n = 6) and was 100% sensitive and specific in this group. Of the small- to moderate-sized effusions (n = 22), the sensitivity and specificity were 80% and 75%, respectively. CONCLUSIONS: CT findings of right ventricular wall flattening, pericardial thickening, and a large pericardial effusion significantly increase the likelihood of tamponade. In this study, the majority of patients diagnosed with HSPE by CT did indeed have tamponade by standard echo criteria. Although not a useful screening tool in the diagnosis of HSPE, CT is of some help, and abnormal results warrant more urgent clinical evaluation.

Noninvasive assessment of pulmonary vascular resistance using Doppler tissue imaging of the tricuspid annulus.

BACKGROUND: Pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR) are important hemodynamic parameters in patients with advanced cardiopulmonary disease. We undertook this study to determine whether Doppler tissue imaging of the tricuspid annulus could be used to assess PAP and PVR noninvasively. METHODS: We studied 50 consecutive patients with suspected chronic thromboembolic pulmonary hypertension referred to our center for evaluation. We performed preoperative transthoracic echocardiography with Doppler tissue imaging of the tricuspid annulus. All patients then underwent cardiac catheterization with invasive determination of cardiac output, PAP, and PVR. RESULTS: The systolic velocity of the tricuspid annulus (tS(m)) had an inverse relationship with catheterization-derived mean PAP, with a correlation coefficient of -0.493 (P = .0003). The inverse correlation of tS(m) with catheterization-derived PVR was more striking, with a correlation coefficient of -0.710 (P < .0001). Based on the data, we derived the following logarithmic regression equation: PVR = 3698 - 1227 x ln(tS(m)). CONCLUSIONS: Doppler tissue imaging of the lateral tricuspid annulus is a useful clinical tool that can provide a noninvasive estimate of PVR in patients with chronic thromboembolic pulmonary hypertension. In this population, decreasing values of tS(m) predicted progressively higher measurements of PVR.

Assessment of diastolic function with Doppler tissue imaging after cardiac surgery: effect of the "postoperative septum" in on-pump and off-pump procedures.

Doppler tissue imaging (DTI) of mitral annular velocity is useful in assessing diastolic function. Most centers record at the septal or lateral segments of the annulus. Cardiopulmonary bypass produces changes in the motion of the interventricular septum. We evaluated the use of DTI after operation with and without cardiopulmonary bypass. 18 patients scheduled for cardiac surgery were prospectively examined. Nine underwent cardiopulmonary bypass. Nine had operation without bypass. DTI was performed 4 +/- 3 days before operation and again 31+/- 7 days afterwards. Early diastolic velocities of the lateral and septal segments of the mitral annulus were measured. Ejection fraction and transmitral diastolic early-to-late filling (E/A) ratios were also assessed. Early diastolic septal mitral annular velocity decreased (7.9 +/- 1.2 to 5.9 +/- 1.1 cm/s [P= .001]) after on-pump operation whereas lateral segment velocity remained unchanged (8.5 +/- 2.9 to 8.2 +/- 3.7 cm/s [P = .30]). E/A ratio did not change after operation (1.28 +/- 0.25 to 1.21 +/- 0.47 [P = .45]). In contrast, septal segment velocity in the off-pump group trended higher after operation (5.3 +/- 1.9 to 6.0 +/- 1.5 cm/s [P = .20]). Lateral segment velocity and E/A ratio also increased somewhat, but changes were not significant (6.2 +/- 1.7 to 6.7 +/- 2.9 cm/s [P = .15] and 1.1 +/- 0.5 to 1.2 +/- 0.4 [P = .13], respectively). Ejection fraction increased in both groups. Early diastolic velocity of the septal mitral annulus decreases after operation with cardiopulmonary bypass, but does not change after off-pump operation. In contrast, early diastolic velocity of the lateral segment is not affected by either on-pump or off-pump operation. Measuring lateral segment velocity is recommended for diastolic DTI after cardiopulmonary bypass, as septal DTI may incorrectly suggest diastolic dysfunction.

Limited cardiac ultrasound examination for cost-effective echocardiographic referral.

BACKGROUND: Although a standard echocardiogram is frequently requested and requires significant resources, few data exist on methods to improve referral for this examination. Therefore, we sought to determine the diagnostic value of a limited echocardiographic examination and to predict the cost-effectiveness of a limited imaging strategy on echocardiographic referral. METHODS: A limited echocardiographic examination was reviewed for abnormalities and compared with standard echocardiographic findings. Assuming an imaging strategy in which a normal limited echocardiographic examination would negate the need for standard echocardiography, we calculated the diagnostic yields, the number of full echocardiographic studies eliminated, and the number of abnormal cases missed. We also stratified data by patient age (< or > or = 65 years), inpatient versus outpatient status, gender, referral diagnosis, and referring physician subspecialty. RESULTS: In 151 outpatients, overall diagnostic yield was 47% (95% CI [39%, 55%]), and was lower in those younger than 65 years, in women, and in noncardiologist referral. In 155 inpatients, yields were 75% (95% CI [67%, 83%]) and were also related to age, but not to gender, diagnosis, and physician subspecialty. Sensitivity, specificity, negative and positive predictive values, and accuracy for the limited echocardiographic examination was 77%, 72%, 67%, 81%, and 75%, respectively. The limited imaging strategy negated 70% of studies in the outpatient group younger than 65 years, with a less than 5% chance of missing a clinically significant finding. CONCLUSION: A limited echocardiographic imaging strategy is most cost-effective when used in young outpatients, where it can result in a substantial reduction in referral for standard echocardiography while rarely missing findings.