Three-dimensional Evaluation of Dobutamine-induced Changes in Regional Myocardial Deformation in Ischemic Myocardium Using Ultrasonic Strain Measurements: The Role of Circumferential Myocardial Shortening

Early identification of myocardial ischemia during high-dose dobutamine stress (DOB) has important clinical implications. Myocardial strain imaging can evaluate regional myocardial contractility in the radial, longitudinal, and circumferential directions. The aim of this study was to assess precisely the differences in deterioration of myocardial deformation among the 3 directions in patients with newly developed myocardial ischemia during high-dose (40 microg/kg/min) DOB infusion. Color Doppler tissue 2-dimensional images were recorded during DOB infusion in 20 patients without myocardial ischemia and 25 patients with scintigraphically diagnosed myocardial ischemia caused by left anterior descending coronary artery stenosis. In the offline analysis, systolic radial strain (Sr), longitudinal strain (Sl), and circumferential strain (Sc) were determined in the anteroseptal and anterolateral left ventricular walls. In 20 patients without myocardial ischemia, the peak systolic strains significantly increased in all 3 directions during DOB infusion at rates between 5 and 10 microg/kg/min (Sr 50%-69%, Sl 27%-36%, Sc 29%-38%, all P < .01) with a greater rate of change in the Sr (1.8 and 1.9 times, respectively, P < .001) than in the Sl and Sc. However, the peak systolic strains decreased significantly during DOB infusion at rates between 5 and 10 microg/kg/min in all 3 directions (Sr 56%-35%, Sl 27%-13%, both P < .01; Sc 29%-7%, P < .001) with the greatest rate of change in the Sc in 25 patients with newly developed myocardial ischemia. In conclusion, circumferential myocardial shortening deteriorated to a greater extent during DOB infusion in patients with coronary artery stenosis, and its measurement is a promising tool for detecting newly developed myocardial ischemia.

Frame rate requirement for tissue Doppler imaging in different phases of cardiac cycle: radial and longitudinal functions

Tissue Doppler imaging (TDI) has been suggested for quantitative analysis of regional myocardial function. Myocardial movement included different mechanical phases with different duration and tissue velocity profiles need to high sampling rate in the acquisition of tissue velocity imaging for phases with shorter duration. The aim of this study is determining of frame rate requirement for myocardial tissue velocity imaging for longitudinal and radial functions separately. Tissue velocity imaging recorded from 29 healthy volunteers by use of the apical and para-sternal views. Off-line analysis performed for extracting tissue velocity profiles of the myocardial longitudinal and radial functions. The frequency and subsequently the frame rate calculated separately for all LV segments during two consequent cardiac cycles. Segmental distribution of the time intervals measured in all cardiac phases and the minimum frame rate requirement calculated for each segment. We found significant differences between radial and longitudinal functions (P < 0.001) except early diastolic phases. The presented normal frame rate values for LV segments may useful for accurate studies of myocardial longitudinal and radial functions in different cardiac phases. We conclude that data sampling at a rate of at least 105 and 118 frames per second need for longitudinal and radial functions respectively.

Quantitative assessment of microcollateral recruitment during coronary occlusion using real-time intravenous myocardial contrast echocardiography

BACKGROUND

Residual collateral-derived myocardial blood flow (MBF) (A x beta) is important to protect against myocardial ischemia after acute coronary occlusion.

METHODS

Recruitment of microcollateral was assessed in 22 dogs with left circumflex coronary artery occlusion by analysis of MBF and regional wall thickening (WT) using real-time myocardial contrast echocardiography.

RESULTS

Video intensity and WT at the center of risk area were significantly lower than those at the border of risk area. The video intensity, A value, beta value, and MBF correlated well with WT after left circumflex coronary artery occlusion. The WT of the area with above 25% of normal MBF was preserved and was higher than that at below 25%. However, the deterioration of WT was not distinguished according to A value.

CONCLUSION

Real-time myocardial contrast echocardiography is a useful noninvasive method to evaluate collateral-derived MBF, which can be a reliable index of protection against myocardial ischemia.

Impact of the Coronary Flow Reduction at Rest on Myocardial Perfusion and Functional Indices Derived from Myocardial Contrast and Strain Echocardiography

BACKGROUND

The severity of the coronary flow reduction that corresponds to myocardial perfusion and functional abnormalities remains unclear. We estimated the impact of various severities of flow-limiting coronary stenosis at rest on myocardial perfusion and functional indices from myocardial contrast echocardiography and tissue strain imaging and characterized the relationship between both the indices.

METHODS

Four levels of flow-limiting stenoses (slight, mild, moderate, severe) of the left circumflex coronary artery were examined in 10 open-chest dogs. In the left circumflex coronary artery area, plateau videointensity and time to plateau (TP) of the replenishment curve from myocardial contrast echocardiography were calculated for perfusion analysis, and peak systolic strain and postsystolic strain index (PSI) from tissue strain imaging were measured for functional analysis.

RESULTS

Plateau videointensity and peak systolic strain tended to decrease with increased severity of stenosis, although these differences did not reach the level of statistical significance. TP and PSI were significantly increased in the context of moderate (>or=30-<50%) and severe (>or=50%) flow reduction when compared to baseline values (TP, moderate 1.69 +/- 0.20 and severe 1.77 +/- 0.25 vs baseline 0.93 +/- 0.17, P < .01, respectively; PSI, moderate 0.96 +/- 0.15 and severe 1.28 +/- 0.32 vs baseline 0.59 +/- 0.18, P < .05 and P < .01, respectively). Further, TP and PSI were positively correlated with flow reduction (r = 0.81 and r = 0.84, P < .0001, respectively), and PSI was positively correlated with TP (r = 0.72, P < .0001).

CONCLUSIONS

In contrast to conventional indices, such as plateau videointensity and peak systolic strain, novel indices, such as TP and PSI, were both able to detect 30% or greater coronary flow reduction at rest.

Increased Tei index suggests absence of adequate coronary reperfusion in patients with first anteroseptal acute myocardial infarction

BACKGROUND

The estimation of coronary reperfusion in acute myocardial infarction (AMI) is important. The left ventricular (LV) Tei index is a noninvasive and sensitive parameter expressing overall LV function. We hypothesized that patients without good coronary reperfusion have worse LV function with a higher or worse Tei index compared to those with good reperfusion.

METHODS AND RESULTS

In 85 patients with first anteroseptal AMI, without other cardiac lesions such as prior myocardial infarction, LV hypertrophy or valvular disease, the Tei index was measured using Doppler echocardiography immediately after patients' arrival to the hospital, and the Thrombolysis in Myocardial Infarction (TIMI) grade was evaluated through subsequent coronary angiography. The Tei index was significantly greater in patients who did not have TIMI score of 3 compared to those with a TIMI of 3 (0.60+/-0.13 vs 0.46+/-0.06, p<0.0001). A Tei index >0.50 as the criteria for the absence of TIMI 3 had the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 75, 86, 94, 54 and 78%, respectively.

CONCLUSION

An increased Tei index suggests the absence of adequate coronary reperfusion in patients with first anterior AMI without other lesion.

Geometric Differences of the Mitral Valve Tenting Between Anterior and Inferior Myocardial Infarction with Significant Ischemic Mitral Regurgitation: Quantitation by Novel Software System with Transthoracic Real-time Three-dimensional Echocardiography

We sought to investigate the 3-dimensional geometric differences of mitral leaflet tenting in ischemic mitral regurgitation, comparing inferior and anterior myocardial infarction (MI). Using real-time 3-dimensional echocardiography, we obtained transthoracic volumetric images for patients with significant ischemic mitral regurgitation (9 inferior and 7 anterior). With our novel software system, 3-dimensional images of the leaflets were reconstructed for quantitation. Mitral leaflet configuration was then represented in contour in which the degree of the tenting could be observed. Calculated percent of tethered leaflet area (>5-mm tenting from the annular level) was compared in inferior and anterior MI. Percent of tethered leaflet area was significantly smaller in inferior than anterior MI, reflecting the localized leaflet tenting in inferior MI (16.7 +/- 18.8% vs 38.9 +/- 9.7%, P = .01). In anterior MI, mitral valve leaflets were widely tethered toward the left ventricle, in contrast with inferior MI showing localized tenting of the leaflet.

Different Effects of Propranolol, Phenylephrine, and Saline Volume Loading on Catecholamine-Induced Left Ventricular Outflow Tract Obstruction in Acute Coronary Syndrome

Hemodynamic deterioration due to left ventricular outflow tract (LVOT) obstruction can occur during catecholamine infusion in patients with acute coronary syndrome (ACS). The purpose of the present study was to compare the utility of propranolol, phenylephrine infusion, and rapid saline loading for reversal of dobutamine-induced LVOT obstruction in a canine model of ACS. ACS was induced via left anterior descending artery ligation in 21 open-chest anesthetized dogs, and LVOT obstruction, defined as an LVOT gradient > 30 mmHg, was induced by dobutamine infusion (20 to 40 microg/kg/min). Subsequently, the effects of propranolol infusion (0.7 to 1.0 microg/kg/min, n = 8), phenylephrine infusion (10 to 200 microg/kg/min, n = 7), and saline loading (200 to 400 mL/hr, n = 6) were assessed by serial hemodynamic measurements. All interventions produced significant and comparable improvements in the LVOT pressure gradient (propranolol: 60 +/- 16 to 15 +/- 12; phenylephrine: 68 +/- 15 to 12 +/- 10; saline loading: 58 +/- 18 to 22 +/- 10 mmHg; P < 0.001 for baseline versus postintervention; P = NS for comparison between interventions). Phenylephrine produced the greatest elevation in aortic pressure (propranolol: +15 +/- 13; phenylephrine: +51 +/- 36; saline loading: +15 +/- 15 mmHg; P < 0.05), while saline loading produced the greatest increase in cardiac output (propranolol: +0.05 +/- 0.12; phenylephrine: +0.28 +/- 0.37; saline loading: +0.73 +/- 0.48 L/min; P < 0.05). Propranolol was the only intervention that produced a significant decrease in diastolic pulmonary artery pressure (16 +/- 5 to 11 +/- 3 mmHg, P < 0.05). Propranolol, phenylephrine infusion, and saline volume loading were similarly effective in reversing dobutamine-induced LVOT obstruction in this canine model of ACS. However, each intervention produced different hemodynamic effects with potentially different clinical indications.

Mitral Annulus Flattens in Ischemic Mitral Regurgitation: Geometric Differences Between Inferior and Anterior Myocardial Infarction

Background— New surgical strategies to restore the saddle shape of the mitral annulus are expected to increase annuloplasty effectiveness. Preoperative and postoperative configuration of the curved annulus, however, is difficult to quantify with 2-dimensional echocardiography. We sought to investigate the geometric deformity in the mitral annulus in ischemic mitral regurgitation (MR), comparing inferior and anterior myocardial infarction (MI) with the use of a custom quantitation software system with transthoracic 3-dimensional echocardiography.

Methods and Results— We performed real-time 3-dimensional echocardiography in 23 patients with ischemic MR attributable to inferior MI or anterior MI and in 10 controls. Three-dimensional data were cropped into 18 radial planes, and we manually marked the annulus in mid systole. Three-dimensional annular images were reconstructed, and annular circumferences, areas, and heights were quantified. Annulus was significantly more dilated and flattened in ischemic MR than in controls and was further deformed in anterior MI as compared with inferior MI (control: circumference 9.9±0.7 cm, area 9.6±0.5 cm 2 , height 5.0±0.7 mm; inferior MI: circumference 11.5±1.2 cm [ P <0.01 compared with control], area 11.4±2.0 cm 2 [ P <0.05 compared with control], height 3.5±1.6 mm [ P <0.05 compared with control]; anterior MI: circumference 14.2±2.4 cm [ P <0.0001 compared with control, P <0.05 compared with inferior MI], area 13.7±2.8 cm 2 ] P <0.01 compared with control, P <0.05 compared with inferior MI], height 1.7±1.5 mm [ P <0.0001 compared with control, P <0.05 compared with inferior MI]).

Conclusions— Mitral annulus flattens in ischemic MR. Deformity of the mitral annulus was greater in anterior MI group than in the inferior MI group.