Echocardiographic assessment of the cardio-renal connection: is left ventricular hypertrophy or diastolic function more closely correlated with estimated glomerular filtration rate in patients with cardiovascular risk factors?

Although left ventricular (LV) hypertrophy and diastolic function assessed by echocardiography and chronic kidney disease (CKD) have been established as predictors of cardiovascular events in hypertensive patients, the relationships between the echocardiographic parameters and renal function have not been fully examined. We examined which echocardiographic parameter correlates best with estimated glomerular filtration rate (eGFR) in patients with cardiovascular risk factors. Enrolled in the study were 309 patients (mean age 67 +/- 13 y) with cardiovascular risk factors. Echocardiography was performed to measure left ventricular mass index (LVMI) as an index of LV hypertrophy. Transmitral early to atrial velocity (E/A) ratio and peak early diastolic mitral annular velocity (E') were measured as indexes of LV diastolic function. E/E' was calculated as a parameter of LV preload. eGFR was measured using the equation proposed by the Japanese Society of Nephrology. The correlations of LVMI (r = -0.333, p < 0.001) and hypertension (r = -0.326, p < 0.001) to eGFR were closer than those of E' (r = 0.276, p < 0.001) and E/A (r = 0.224, p < 0.001) to eGFR. Stepwise regression analysis showed that hypertension (beta coefficient = -0.211, p < 0.001) and LVMI (beta coefficient = -0.206, p < 0.001) were independently associated with eGFR. The E/E' increased with a decrease in eGFR, and E/E' in CKD stage 5 (16.0 +/- 6.8) was significantly higher than that in patients in whom eGFR > or = 90 mL/min/1.73 m(2) (10.5 +/- 4.5) (p < 0.001). Left ventricular diastolic function may be influenced by the increase in LV preload due to progression of CKD stage. Therefore, LV hypertrophy may be superior to LV diastolic dysfunction in predicting low eGFR in patients with CKD using echocardiography.

A comparison of video and digital data in the assessment of myocardial perfusion abnormalities by myocardial contrast echocardiography.

OBJECTIVE: The objective of the present study was to compare the digital and video data of myocardial contrast echocardiography (MCE) to assess altered myocardial blood flow produced by graded coronary stenoses. METHODS: Three grades of left anterior descending (LAD) coronary artery stenosis and occlusion were created in eight open-chest canine models. MCE was performed with BR1 infusion by harmonic power Doppler with ECG gated intermittent triggered imaging at pulsing intervals ranging from 1:1 to 1:10. For images that were recorded simultaneously on both a videotape (video data) and an optical disk (digital data), myocardial signal intensity in the LAD region was plotted vs. pulsing intervals and was fitted to an exponential function: y = A(1 - e(-bt)), where A is the peak plateau signal intensity, and b is the rate of signal intensity rise for quantification of myocardial blood flow. RESULTS: Both values for A and b progressively decreased with a greater level of stenosis. The correlation of A with myocardial blood flow (determined by use of fluorescent microspheres) was weak with digital data (r = 0.38, p = 0.037), and was insignificant with video data (r = 0.16, p = 0.38). The correlation of b with microsphere-derived myocardial blood flow was better than that of A with both video and digital data, and was similar between the two kinds of data (video: r = 0.69, p < 0.0001; digital: r = 0.68, p < 0.0001). CONCLUSIONS: Video and digital MCE data are equivalent in their ability to quantify altered myocardial blood flow produced by graded coronary stenoses.

Latent abnormal fatty acid metabolism in apparently normal perfusion during stress in patients with restenosis after coronary angioplasty: assessment by exercise stress thallium-201 and iodine-123-labeled 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid-dual myocardial single-photon emission computed tomography.

Restenosis is a major problem in patients undergoing coronary angioplasty. Reduced uptake of iodine-123-labeled 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (I-BMIPP-123) relatively to thallium-201 (Tl-201) has been attributed to the metabolic damage in the myocardium in patients with coronary artery disease. Therefore, we performed exercise stress Tl-201 and I-BMIPP-123 dual myocardial single-photon emission computed tomography (SPECT) to detect coronary restenosis in 48 patients (35 men and 13 women, mean age 66 +/- 8 years), followed by coronary angiography at follow-up. Patients were divided into 2 groups: those with (n = 24) and without (n = 24) restenosis. Redistribution of Tl-201 was seen more frequently in the restenosis group than in no-restenosis group (58% [14 of 24] vs 8% [2 of 24], p <0.05). Five of 10 patients (50%) with restenosis but without Tl-201 redistribution had Tl-201/I-BMIPP-123 discrepancy during stress. In patients without restenosis, only 1 patient had this discrepancy during stress. Incorporation of Tl-201/I-BMIPP-123 uptake discrepancy during stress significantly improved the sensitivity (58% [14 of 24] to 79% [19 of 24]) with preserved specificity (92% [22 of 24] to 88% [21 of 24]). Exercise stress Tl-201 and I-BMIPP-123 dual myocardial SPECT revealed that latent abnormal fatty acid metabolism may exist in apparently normal perfusion during stress in patients with restenosis after coronary angioplasty. Use of I-BMIPP-123 together with Tl-201 during stress SPECT substantially improved the diagnostic accuracy of restenosis based on Tl-201 redistribution (from 75% to 83%).

Assessment of adenosine-induced coronary steal in the setting of coronary occlusion based on the extent of opacification defects by myocardial contrast echocardiography.

The authors examined the ability of real-time myocardial contrast echocardiography (MCE) to assess adenosine-induced coronary steal in the setting of coronary artery occlusion. The left anterior descending (LAD) coronary artery was occluded in 8 open-chest dogs. Real-time MCE was performed during LAD occlusion, and the extent of opacification defects from MCE was measured without and with adenosine infusion. Microsphere-derived myocardial blood flow (MBF) was measured in the LAD and left circumflex (LCx) coronary artery beds, and the LAD/LCx ratio of MBF was calculated. The LAD/LCx ratio of MBF decreased in response to adenosine administration (without adenosine: 0.66, with adenosine: 0.43, p < 0.01). The extent of opacification defects from MCE increased in response to adenosine administration (without adenosine: 18%, with adenosine: 22%, p < 0.01). Thus, real-time MCE allows for the detection of adenosine-induced coronary steal as changes in the extent of opacification defects in the setting of occlusion of 1 coronary artery accompanying another normally patent coronary artery.

Quantitative assessment of coronary stenosis by harmonic power Doppler with a simple pulsing sequence and vasodilator stress in patients.

OBJECTIVES: We examined whether myocardial contrast echocardiography (MCE) with harmonic power Doppler (HPD) employing a simple ultrasound pulsing sequence enables estimation of the severity of coronary artery stenosis in patients. BACKGROUND: Contrast intensity (CI) during MCE with intravenous microbubble infusion is dependent on the myocardial blood flow velocity (MBFV) and pulsing interval (PI). METHODS: Based on an in vitro experiment, we devised the MBFV index calculated as the reciprocal of the magnitude of CI decay produced by abrupt PI shortening during intermittent imaging. In 68 coronary artery territories from 49 patients, myocardial HPD images were acquired during intravenous infusion of Levovist, while the long PI with 1:10 electrocardiographic gating was shortened to 1:1, both at baseline and during adenosine triphosphate infusion. The MBFV index in each coronary territory and MBFV reserve as the ratio between hyperemia and baseline were compared with the severity of corresponding coronary artery stenosis assessed by quantitative coronary angiography (QCA) or by pressure guide wire as the fractional flow reserve (FFR). RESULTS: Both the MCE-derived MBFV index during hyperemia and MBFV reserve exhibited significant negative correlations with the QCA-derived stenosis severity (r = -0.56 and r = -0.64, respectively). The MBFV reserve positively correlated with FFR (r = 0.89). By combining the cutoff values of the MBFV index during hyperemia and MBFV reserve, > or =75% of stenoses defined by QCA were determined, with a sensitivity of 77.3%, specificity of 93.4%, and accuracy of 88.3%. CONCLUSIONS: Shortening of PI during intravenous MCE with intermittent HPD imaging under vasodilator stress enables assessment of coronary artery stenoses in patients.

Assessment of right ventricular perfusion after right coronary artery occlusion by myocardial contrast echocardiography.

OBJECTIVES: The purpose of this study was to examine the ability of myocardial contrast echocardiography (MCE) to assess right ventricular (RV) perfusion. BACKGROUND: Although MCE can readily assess left ventricular perfusion abnormalities, there are no data regarding the ability to assess RV perfusion abnormalities. METHODS: The right coronary artery (RCA) was occluded in 10 open-chest dogs. Myocardial contrast echocardiography was performed with 0.27 g/min Levovist infusion by harmonic power Doppler with electrocardiographically gated intermittent triggered imaging at pulsing intervals ranging from 1:1 to 1:20 at baseline and 90 min after RCA occlusion. Video-intensity of the RV wall was plotted against pulsing intervals and was fitted to an exponential function: y = A(1-exp(-bt)), where A is the plateau video-intensity and b is the rate of video-intensity rise. Myocardial contrast echocardiography and microsphere-derived myocardial blood flow (MBF) measurements were performed at baseline and 90 min after RCA occlusion. RESULTS: Because the severity of RV perfusion abnormalities assessed by MBF varied during RCA occlusion, diverse grades of patchy opacification defects were observed by MCE. The RV wall thickness decreased, and the RV dimension increased, after RCA occlusion in each dog. The correlation of occlusion to baseline MBF ratios in the RV wall was closer to the ratio of b (r = 0.897, p = 0.0004) than A (r = 0.767, p = 0.0097) and was the closest to the ratio of Axb (r = 0.935, p < 0.0001). CONCLUSIONS: The RCA occlusion is manifested by RV wall thinning and dilation as well as by perfusion abnormalities consisting of patchy opacification defects by MCE. Myocardial contrast echocardiography-derived refilling parameters can be applied to assess RV perfusion abnormalities produced by RCA occlusion.

Assessment of myocardial viability in prior myocardial infarction by intravenous bolus microbubble injection: a new time domain index to estimate regional relative myocardial blood volume.

We tested whether the duration of myocardial opacification by harmonic power Doppler imaging after intravenous bolus microbubble injection (with a definition of "the end of opacification") would reflect the remaining vascular bed in infarcted segments. In 28 patients with previous myocardial infarction and 20 control patients, we performed harmonic power Doppler imaging after intravenous bolus injection of 1.5 g of Levovist. Using multiframe trigger mode in which 4 consecutive frames were imaged at every sixth end systole, which formed 1 "burst," we recorded anterior/septal and inferior/posterior walls separately on the center of each apical view with individual boluses. The duration of segmental opacification was measured as the number of "bursts" in which color signals persisted until the fourth frame. The duration was similar between the anterior/septal and inferior/posterior walls (13 +/- 3 vs 13 +/- 3 bursts, not significant) in the control group. In myocardial infarction patients, the duration was significantly shorter in the infarcted than in the control segments (6 +/- 6 vs 14 +/- 3 bursts, P < .001) and their ratio and difference exhibited significant correlations (r = 0.82, P < .001 and r = 0.91, P < .001, respectively) with the activity ratio on thallium Tl 201 single-photon emission computed tomography at rest. Thus, the duration of opacification by harmonic power Doppler imaging after intravenous bolus microbubble injection, the measurement of which was standardized by using multiframe trigger mode, may be useful in assessing regional myocardial viability in patients with previous myocardial infarction.