New applications of intracardiac echocardiography: assessment of coronary blood flow by colour and pulsed Doppler imaging in dogs

OBJECTIVE

To explore the application of a new 10 French intracardiac echocardiography (ICE) catheter with phased array and Doppler capable transducer for the assessment of epicardial and intramyocardial coronary blood flow.

METHODS

The coronary arteries were detected by cross sectional imaging in seven closed chest dogs, and coronary blood flow visualised by colour Doppler. Blood flow velocities were recorded by pulsed Doppler at baseline for reproducibility of repeated measurements, and during hyperaemia for coronary flow reserve measurements. Comparisons were made with Doppler guide wire data obtained simultaneously. Intramyocardial coronary artery blood flow was assessed by colour flow mapping, and the blood flow velocities recorded using pulsed Doppler at baseline and during hyperaemia.

RESULTS

Seven left main, six left anterior descending, seven left circumflex, and five right coronary arteries were visualised in the seven animals by cross sectional or colour Doppler imaging. Repeated measurements of coronary flow velocity showed a good correlation (mean diastolic velocity, r = 0.93, n = 22, p < 0.0001; peak diastolic velocity, r = 0.96, n = 22, p < 0.0001, respectively). Intraobserver/interobserver variability was satisfactorily low. Coronary flow reserve from ICE correlated highly with the value obtained from the Doppler guide wire (r = 0.90, n = 26, p < 0.0001). Intramyocardial coronary blood flow was identified in all seven dogs, and flow velocities were recorded at baseline and during hyperaemia in four animals.

CONCLUSIONS

This new ICE catheter provides high quality diagnostic resolution. It is useful for coronary blood flow assessment.

Novel method for assessing myocardial perfusion: visualization and measurement of intramyocardial coronary blood flow in the entire left ventricular wall using contrast enhanced, high frequency Doppler echocardiography

Using a high frequency ultrasonic transducer, intramyocardial coronary blood flow (IM-CBF) can be visualized and evaluated during hemodynamic changes in the anterior wall and septum of the left ventricle (LV). We tested the hypothesis that detection and quantitative measurement of IM-CBF of entire LV segments are feasible using a high frequency ultrasonic transducer in conjunction with intravenous contrast injection in vivo. A 3 - 8 MHz transducer was used to image and measure IM-CBF in 10 anesthetized dogs. We obtained a color Doppler image of IM-CBF in the LV short-axis view after intravenous Levovist injection (25 mg/ml). The IM-CBF velocity was recorded using spectral Doppler in the antero-septal and infero-posterior wall of closed chest dogs and in the entire LV after opening the chest. A significant increase in IM-CBF velocity was observed in all LV regions after adenosine 5'- triphosphate (ATP) administration. After Levovist(TM) injection, the visualization of IM-CBF was improved and the spectral Doppler pattern of coronary flow velocity was clarified compared to baseline. IM-CBF was assessed in the antero-septal region of the LV before and after left anterior descending coronary artery occlusion. A high frequency ultrasonic transducer in conjunction with intravenous contrast injection improved IM-CBF visualization, enabling quantitative evaluation of the intramyocardial coronary circulation in the entire LV after coronary occlusion and hyperemia. This study may represent a step towards noninvasive assessment of myocardial perfusion before and after coronary reperfusion.

Long-acting calcium channel antagonist pranidipine prevents ventricular remodeling after myocardial infarction in rats

The purpose of this study was to examine the effects of the long-acting calcium channel antagonist pranidipine on ventricular remodeling, systolic and diastolic cardiac function, circulating humoral factors, and cardiac mRNA expression in myocardial infarcted rats. Myocardial infarction (MI) was produced by ligation of the coronary artery in Wistar rats. Three mg/kg per day of pranidipine was randomly administered to the infarcted rats. Hemodynamic measurements, Doppler echocardiographic examinations, analyses of the plasma levels of humoral factors, and myocardial mRNA expression were performed at 4 weeks after myocardial infarction. Left ventricular end-diastolic pressure (LVEDP) and central venous pressure (CVP) increased to 24.2 +/- 1.2mmHg and 5.4 +/- 0.6 mmHg. Pranidipine reduced LVEDP and CVP to 13.6 +/- 1.4mmHg (P < 0.01) and 2.5 +/- 0.4mmHg (P < 0.01). The weight of the left and right ventricles in MI was significantly higher than in the sham-operated rats (sham, 2.02 +/- 0.04 and 0.47 +/- 0.02g/kg; MI, 2.18 +/- 0.05 and 0.79 +/- 0.04g/ kg; P < 0.01). Left ventricular end-diastolic dimension (LVDd) in MI increased to 10.3 +/- 0.3mm (P < 0.01) (sham, 6.4 +/- 0.3mm). Pranidipine prevented an increase in the weight of the left and right ventricles (2.02 +/- 0.04 and 0.6 +/- 0.03g/kg, P < 0.01) and LVDd (7.9 +/-0.2mm, P < 0.01 to MI). Plasma renin activity (PRA), and plasma epinephrine, norepinephrine, and dopamine concentrations in MI were higher than those of the sham-operated rats. Pranidipine decreased the PRA and plasma cathecolamine levels of the myocardial infarcted rats to the level of the sham-operated rats. Moreover, the rats in MI showed systolic dysfunction, shown by decreased fractional shortening (sham, 31 +/- 2% vs MI, 15 +/- 1%; P < 0.01) and diastolic dysfunction shown by the E-wave deceleration rate (sham, 12.8 +/- 1.1 m/s2; MI, 32.6 +/- 2.1 m/s2; P < 0.01). Pranidipine significantly prevented systolic and diastolic dysfunction. The increases in beta-myosin heavy chain (MHC), alpha-skeletal actin, and atrial natriuretic polypeptide mRNAs in the noninfarcted left ventricle and right ventricle at 4 weeks after the myocardial infarction were significantly suppressed by the treatment with pranidipine. On the other hand, depressed alpha-MHC was restored to normal levels by pranidipine in both regions. In conclusion, pranidipine prevents the left ventricular remodeling process accompanied by systolic and diastolic dysfunction, and inhibits abnormal cardiac gene expression after myocardial infarction.