Search PubMed⌕ Search

Biomedical subjects

T Masuyama

Publications and source records attributed to T Masuyama.

At least 91 records · Page 5Linked to original sources
PubMed1994

Dobutamine stress echocardiography predicts reversible dysfunction and quantitates the extent of irreversibly damaged myocardium after reperfusion of anterior myocardial infarction.

OBJECTIVES: This study was designed to evaluate dobutamine stress echocardiography in identifying reversible dysfunction and assessing the extent of irreversibly damaged myocardium early in acute myocardial infarction. BACKGROUND: Several experimental and clinical studies have suggested that dobutamine enhances contractile function of stunned or hibernating, or both, myocardium. It is important for clinical strategy to predict the magnitude of improvement in myocardial function early in acute myocardial infarction. METHODS: We studied 21 patients with a reperfused first anterior myocardial infarction. Two-dimensional echocardiography was performed before and during dobutamine infusion (10 micrograms/kg body weight per min) at a mean of 3 days after the infarction. Follow-up echocardiography was performed at a mean of 25 days later. To assess segmental wall motion, we divided the left ventricle into 17 segments and assigned a wall motion abnormality score: 3 = dyskinesia or akinesia; 0 = normal. Improvement in wall motion was indicated by a decrease of at least one grade in segmental score. For quantitative assessment, the ratio of endocardial length showing dyskinesia or akinesia to a left ventricular endocardial length (akinetic length ratio) was determined in the apical long-axis view at each stage. RESULTS: Sensitivity and specificity of dobutamine infusion in detecting improvement in wall motion at follow-up echocardiography were 83% (55 of 66 segments) and 86% (43 of 50 segments), respectively. Excellent correlation was found (r = 0.93, p < 0.001; absolute difference [mean +/- SD] 0.03 +/- 0.05) between the akinetic length ratios measured during dobutamine infusion and in the late convalescent stage. CONCLUSIONS: In the early stage of acute myocardial infarction, low dose dobutamine stress echocardiography provides a useful method for predicting reversible dysfunction with excellent sensitivity and specificity and can also be used to quantitate the extent of irreversibly damaged myocardium.

Adult↗
PubMed1994

Abnormal coronary flow dynamics at rest and during tachycardia associated with impaired left ventricular relaxation in humans: implication for tachycardia-induced myocardial ischemia.

OBJECTIVES: This study attempted to clarify the effect of ventricular relaxation abnormalities on coronary flow dynamics at rest and during tachycardia in humans. BACKGROUND: Ventricular relaxation abnormality has been demonstrated in animals to have an adverse impact on early diastolic coronary flow dynamics. However, this relation has not been established in humans. Even if the adverse effect were latent at rest, it might become evident during tachycardia because tachycardia reduces coronary flow reserve and facilitates the production of myocardial ischemia. METHODS: Doppler phasic left coronary flow velocity pattern was obtained at rest and during tachycardia in 23 patients without coronary stenosis. The time constant of left ventricular isovolumic pressure (tau) was used to assess ventricular relaxation. RESULTS: The time to peak flow velocity of the diastolic coronary flow wave was longer, and the fraction of the first third of diastolic coronary flow was smaller, in patients with a longer tau (r = 0.58, p < 0.01; r = -0.44, p < 0.05), indicating a close relation between early diastolic coronary flow dynamics and ventricular relaxation. Although rapid atrial pacing yielded an increase in the coronary flow velocity integral per minute in all patients, diastolic coronary flow velocity integral per minute increased in 9 patients with a normal (< or = 40 ms) tau at rest but decreased in 14 patients with a longer (> 40 ms) tau at rest. CONCLUSIONS: Impaired left ventricular relaxation was associated with decreased coronary flow in early diastole at rest and decreased coronary flow throughout diastole during tachycardia in patients without coronary stenosis. These findings may provide more insight into the mechanism of tachycardia-induced subendocardial ischemia in patients with impaired ventricular relaxation but without concomitant coronary stenosis.

Adult↗
PubMed1994

Analysis of transmural trend of myocardial integrated ultrasound backscatter for differentiation of hypertrophic cardiomyopathy and ventricular hypertrophy due to hypertension.

OBJECTIVES: This study was undertaken to differentiate hypertrophic cardiomyopathy from hypertensive hypertrophy using a newly developed M-mode format integrated backscatter imaging system capable of calibrating myocardial integrated backscatter with the power of Doppler signals from the blood. BACKGROUND: Myocardial integrated ultrasound backscatter changes in patients with hypertrophic cardiomyopathy; however, it is unknown whether ultrasound myocardial tissue characterization may be useful in differentiating hypertrophic cardiomyopathy from hypertensive hypertrophy. METHODS: Calibrated myocardial integrated backscatter and its transmural gradient were measured in the septum and posterior wall in 31 normal subjects, 13 patients with hypertensive hypertrophy and 22 patients with hypertrophic cardiomyopathy. The gradient in integrated backscatter was determined as the ratio of calibrated integrated backscatter in the endocardial half to that in the epicardial half of the myocardium. RESULTS: Cyclic variation of integrated backscatter was smaller and calibrated myocardial integrated backscatter higher in patients with hypertrophied hearts than in normal subjects, but there were no significant differences in either integrated backscatter measure between patients with hypertensive hypertrophy and those with hypertrophic cardiomyopathy. Transmural gradient in myocardial integrated backscatter was present only in patients with hypertrophic cardiomyopathy (5.0 +/- 1.8 dB [mean +/- SD] for the septum; 1.2 +/- 1.6 dB for the posterior wall). CONCLUSIONS: Hypertrophic cardiomyopathy and ventricular hypertrophy due to hypertension can be differentiated on the basis of quantitative analysis of the transmural gradient in integrated backscatter.

Acoustics↗
PubMed1994

New method for quantitatively determining aortic regurgitant volume using Doppler color flow imaging: experimental validation study.

We have developed a method to provide the two-dimensional distribution of blood flow velocity and the blood flow volume rate in the ascending aorta from the cross-sectional Doppler color flow image. Regional blood flow velocities were determined by converting color intensities of the cross-sectional Doppler color flow image into the corresponding flow velocities with the correction with the spatial ultrasound beam incident angle. The spatial ultrasound beam incident angle was estimated from the geometric characteristics of the color flow image contour. The method was validated in a steady flow model circuit comparing the calculated flow volume rates by the method with those simultaneously measured by an electromagnetic flowmeter. We performed an open chest dog experiment and calculated the blood flow volume rate at the ascending aorta before and after the aortic regurgitation was made. The calculated ejection flow volume rate and regurgitant volume were validated by the comparison with those simultaneously measured by an electromagnetic flowmeter. Based on these data, we can conclude that the current method provides accurate measurements of regurgitant volume as well as ejection flow volume rate in the ascending aorta.

Animals↗
PubMed1994

Contribution of chamber compliance and left ventricular minimum pressure to abnormal left ventricular filling dynamics.

This study was designed to clarify whether changes in transmitral flow velocity patterns in left ventricular (LV) dysfunction are determined primarily by changes in left atrial (LA) pressure and LV relaxation, and, if not, to determine the contribution of changes in other parameters. Two levels of acute LV dysfunction were produced in 11 dogs by coronary microembolization, and pulsed Doppler transmitral flow velocity patterns and hemodynamic parameters were recorded. The mean ratio of peak early diastolic filling velocity (E) to peak late diastolic filling velocity decreased with mild LV dysfunction (LV end-diastolic pressure of between 12 and 17 mmHg), and redistribution of diastolic filling to early diastole was observed with severe LV dysfunction (LV end-diastolic pressure of > or = 18 mmHg). Changes in E correlated best with those in the LA-LV pressure gradient integral. Multiple linear regression analysis of the changes in possible determinants of the pressure gradient integral, i.e., LA to LV crossover pressure, LV time constant, LV minimum pressure, and LA and LV chamber compliance, yielded a highly significant correlation with the changes in E. However, analysis of only the changes in the crossover pressure and the time constant showed a very poor correlation. Thus, changes in chamber compliance and LV minimum pressure, in addition to the changes in LA pressure and LV relaxation, may significantly affect the changes in E that are associated with LV dysfunction.

Animals↗
PubMed1994

[Usefulness of Dornier MPL9000 lithotriptor with new optional fluoroscopic guiding system (electrode X 155: depth 15.5cm) in treatment of urinary tract stone].

The Dornier MPL9000 lithotriptor was originally equipped with an ultrasound guiding system. Recently an optional fluoroscopic guiding system was developed to overcome the known disadvantages of the ultrasound system and to exploit the merits of both systems by using them in combination. Herein, we examined the effectiveness and safety of this new optional system. From December 1990 to February 1991, we treated 41 patients with upper urinary tract stones with MPL9000 using the optional fluoroscopic system. Treatments were judged as effective if the patients were stone-free or the residual fragments were smaller than 4mm in diameter. The overall effectiveness rates at one month after the treatment were 54.5% for renal stones and 76.9% for ureter stones respectively. At three months after the treatment the effectiveness rate for renal stones was 83.3%, and that for ureter stones 95.5%. The changes in the laboratory data after the treatment were alight and caused no clinical problems. Complications during and after the treatment were also minor and tolerable. MPL9000 was sufficiently effective and safe in the treatment of upper urinary tract stones when it was used the new optional fluoroscopic system instead of the original ultrasonic guiding system.

Adult↗
PubMed1993

Importance of left ventricular minimal pressure as a determinant of transmitral flow velocity pattern in the presence of left ventricular systolic dysfunction.

OBJECTIVES: This study was designed to assess whether the transmitral flow velocity pattern provides an estimation of left atrial pressure irrespective of the presence of left ventricular systolic dysfunction and, if not, to clarify the mechanism. BACKGROUND: The pulsed Doppler transmitral flow velocity pattern, particularly peak early diastolic filling velocity, has been shown to change in parallel with left atrial pressure. However, extremely elevated left atrial pressure in association with heart failure does not necessarily cause an increase in peak early diastolic filling velocity in patients. METHODS: Left atrial pressure was elevated with intravenous saline infusion in 11 dogs (normal left ventricular function group) and hemodynamic, transesophageal Doppler echocardiographic and M-mode echocardiographic variables were recorded at three different loading levels. In another 12 dogs, left atrial pressure was elevated by production of left ventricular systolic dysfunction with the stepwise injection of microspheres into the left coronary artery (left ventricular dysfunction group) and the same set of recordings was obtained at three different levels of dysfunction. RESULTS: Peak early diastolic filling velocity increased with left atrial pressure in the normal left ventricular function group and correlated with mean left atrial pressure (r = 0.61, p < 0.01) and early diastolic left atrial to left ventricular crossover pressure (r = 0.71, p < 0.01). In contrast, peak early diastolic filling velocity did not increase with left atrial pressure in the left ventricular dysfunction group and did not correlate with mean left atrial pressure (r = -0.05) or the crossover pressure (r = 0.06). Peak early diastolic filling velocity correlated well with the difference between the crossover pressure and left ventricular minimal pressure in the left ventricular dysfunction group (r = 0.64, p < 0.01). In contrast to peak early diastolic filling velocity, deceleration time of the early diastolic filling wave correlated with mean left atrial pressure and the crossover pressure irrespective of the primary cause of preload alteration (r = -0.54, r = -0.59, p < 0.01 respectively, n = 69 for all data). CONCLUSIONS: Preload dependency of the Doppler transmitral flow velocity pattern is hampered if an increase in left atrial pressure is due to left ventricular systolic dysfunction. In this setting, the increase in left ventricular minimal pressure due to left ventricular systolic dysfunction cancels the effect of the increase in left atrial pressure on the flow velocity pattern.

Animals↗
PubMed1993

Myocardial hibernation in the infarcted region cannot be assessed from the presence of stress-induced ischemia: usefulness of delayed image of exercise thallium-201 scintigraphy.

To examine the relationship between the improvement of wall motion in infarcted regions after percutaneous transluminal coronary angioplasty (PTCA) and thallium-201 uptake in the delayed image of exercise thallium-201 scintigraphy before PTCA, 14 patients with anterior old myocardial infarction were studied. Exercise thallium-201 scintigraphy was performed before PTCA of left anterior descending artery, and mean percent thallium-201 uptake of abnormal segments was calculated in the initial and 4-hour delayed images. Left ventricular angiography was performed during catheterization, before, and 4 to 13 months after PTCA; and regional ejection fraction of anterior wall was calculated. Atrial pacing stress test with the measurement of lactate concentration of aorta and great cardiac vein was performed during catheterization before PTCA. In five patients with mean percent thallium-201 uptake in the delayed image < or = 50% (group I), regional ejection fraction did not increase after PTCA (23% +/- 9% to 24% +/- 12%). In the other nine patients with mean percent thallium-201 uptake > 50% (group II), regional ejection fraction increased significantly after PTCA (39% +/- 18% to 47% +/- 14%; p < 0.05). There was no significant difference in regional ejection fraction, lactate extraction ratio during maximal pacing, and the redistribution of exercise thallium-201 scintigraphy between the two groups before PTCA. Thus the delayed image before PTCA is useful to detect reversible nonfunctioning viable myocardium (hibernating myocardium) in the infarcted region. However, the wall-motion abnormality and the degree of stress-induced ischemia in the infarcted region before PTCA may not be necessarily useful for the detection of hibernating myocardium.

Aged↗
PubMed1993

Effects of heart rate on left ventricular filling dynamics: assessment from simultaneous recordings of pulsed Doppler transmitral flow velocity pattern and haemodynamic variables.

OBJECTIVE: The effects of heart rate on transmitral flow velocity pattern are still controversial. The aim of this study was to examine the relations between the changes in Doppler echocardiographic variables and those in haemodynamic variables in association with altering heart rate. METHODS: Pulsed Doppler transmitral flow velocity pattern and left atrial and left ventricular pressures were simultaneously recorded at various heart rates (from 80 to 120 beats.min-1) in 14 dogs. RESULTS: As heart rate increased, peak late diastolic filling velocity increased, the time-velocity integral of the early diastolic filling wave decreased, and the deceleration time of early diastolic flow shortened without significant changes in mean values of peak early diastolic filling velocity and acceleration time of early diastolic flow. Peak early diastolic filling velocity increased with heart rate, however, in five dogs and decreased in the other nine dogs. The shortening of the time constant of left ventricular isovolumic relaxation was greater in the five dogs in which peak early diastolic filling velocity increased with heart rate than in the other nine dogs. Results of multiple stepwise linear regression analysis showed that the changes in peak early diastolic filling velocity correlated with the changes in the crossover pressure and peak+dP/dt in addition to the time constant, and that diastolic filling period was not selected as an affecting factor. Changes in the other Doppler echocardiographic variables did not correlate solely with changes in heart rate, or diastolic filling period, but correlated in a complex fashion with the combined changes in haemodynamic variables associated with altering heart rate. CONCLUSIONS: Although transmitral flow velocity pattern changes with altering heart rate, this change is not considered to be a direct effect of alteration in heart rate, but an indirect one through the associated haemodynamic changes including left atrial pressure and left ventricular relaxation and contractility.

Animals↗
PubMed1993

Time course of functional improvement in stunned myocardium in risk area in patients with reperfused anterior infarction.

BACKGROUND: The beneficial effect of coronary reflow on myocardial salvage may be assessed more accurately than in previous studies if the size of risk area is taken into account, particularly because the size of risk area varies significantly among patients. In this study, the risk area was determined with myocardial contrast echocardiography to investigate the time course of functional recovery of postischemic myocardium within the risk area in patients with reperfused anterior myocardial infarction. METHODS AND RESULTS: The study population consisted of 21 patients with anterior myocardial infarction who achieved coronary reflow within 6 hours of onset by means of thrombolysis or coronary angioplasty. Myocardial contrast echocardiography was performed with the injection of hand-agitated Haemaccel (5 ml) into the right and left coronary arteries before coronary reflow, and the risk area was defined as the area of contrast perfusion defect in the apical long-axis view. The ratio of the endocardial length of abnormal contraction (dyskinesis/akinesis) segment to that of contrast defect segment (AS/CD) was determined at days 1, 2, 3, 7, 14, and 28 of reflow. Before reflow, the length of contrast defect correlated well with the segment length of dyskinesis/akinesis. The values for AS/CD in patients with successful reperfusion significantly and progressively decreased until day 14; 1.00 +/- 0.02 at day 1, 0.93 +/- 0.11 at day 2 (p < 0.05 versus day 1), 0.84 +/- 0.16 at day 3 (p < 0.05 versus day 2), 0.80 +/- 0.13 at day 7 (p < 0.01 versus day 2), 0.73 +/- 0.10 at day 14, and 0.72 +/- 0.10 at day 28. Greater improvement in function was obtained in patients reperfused within 4 hours than in those reperfused at > or = 4 hours (AS/CD at day 28, 0.64 +/- 0.12 versus 0.75 +/- 0.09, p < 0.05). CONCLUSIONS: Thus, a significant amount of myocardium, an average of 28% in segment length of the risk area, is salvaged in patients with reperfused anterior myocardial infarction. Major functional improvement seems to be achieved within 14 days of reflow.

Adult↗
PubMed1993

Demonstration of functional border zone with myocardial contrast echocardiography in human hearts. Simultaneous analysis of myocardial perfusion and wall motion abnormalities.

BACKGROUND: Although the presence of a functional border zone (FBZ), defined as the nonischemic but asynergic myocardium adjacent to the ischemic area, has been demonstrated in animal hearts, it is not known whether this zone exists in humans. METHODS AND RESULTS: Myocardial contrast echocardiography (MCE) was performed before and during balloon inflation in the area of coronary stenosis by injecting contrast medium through the guiding catheter in 13 patients with effort angina who underwent successful coronary angioplasty. The area showing MCE defect during balloon inflation was determined with reference to the preangioplasty MCE and was regarded as an ischemic area. The size of the FBZ was assessed by measuring the length of the endocardium that showed asynergy in the echo-enhanced (nonischemic) area. The FBZ measured was 13 +/- 4 mm in the short-axis view (n = 5) and 16 +/- 9 mm in the long-axis view (n = 8). CONCLUSIONS: Nonischemic contractile dysfunction exists even in human hearts. The presence of an FBZ may limit the use of wall motion analysis in assessing the risk or ischemic area in patients with myocardial infarction. MCE appears to be a unique technique for assessing the risk or ischemic area.

Adult↗
PubMed1993

Effects of vasodilators on pulmonary venous and mitral flow velocity patterns in patients with congestive heart failure.

To characterize abnormalities in pulmonary venous flow velocity patterns and to explore the changes in these patterns following short-term (3 to 14 days) administration of vasodilators, pulmonary venous and mitral flow velocity patterns were serially studied at congestive heart failure and after vasodilator administration in 18 patients. Peak mitral early diastolic filling velocity (E) and the ratio of E to peak filling velocity at atrial contraction (E/A) consistently decreased after vasodilator administration by 30 +/- 4 cm/s and 0.74 +/- 0.13 (mean +/- SD), respectively. Peak pulmonary venous diastolic forward flow velocity also decreased by 29 +/- 4 cm/s. However, changes in peak pulmonary venous systolic forward flow velocity (S, cm/s) did not correlate with changes in E, the E/A ratio, or D (peak pulmonary venous diastolic forward flow velocity). Thus, when patients were divided into two groups on the basis of changes in S, indices of left ventricular systolic performance, such as end-systolic dimension and fractional shortening, improved more in the group which showed an increase in S after vasodilator administration than in the group which showed a decrease in S (-7 +/- 6 vs -1 +/- 4 mm, p < 0.05; 8 +/- 6 vs -1 +/- 4%, p < 0.05). Although the mitral flow velocity pattern changed uniformly with vasodilator administration in patients with mild to moderate congestive heart failure, the changes in pulmonary venous flow velocity patterns were not uniform among patients. Pulmonary venous flow velocity patterns appear to reflect changes in left ventricular systolic performance in addition to those in left ventricular diastolic performance.

Adult↗
PubMed1993

[Changes in renal blood flow after treatment with ESWL in patients with renal stones. Studies using ultrasound color Doppler method].

Recently several authors have observed tissue damages in ESWL treated kidneys, such as interstitial hemorrhage and edema, cavitation of renal tubular cells and vascular spasms. Examination using renal scintigraphy suggested that these damages could cause a decrease of renal blood flow in the treated kidney. Trying to confirm and further investigate this possibility, we studied on changes of renal blood flow velocity using ultrasound color doppler method in 23 consecutive patients with renal stones who underwent ESWL. The studies were conducted before, immediately after and 1 week after an ESWL treatment. Results were as follows; renal blood flow velocity decreased significantly in the area exposed to shock were immediately after the treatment and returned to the pretreatment levels after 1 week. The changes were not significant in the non-exposed area. In parallel with this decrease of renal blood flow velocity, significant increases of resistive index, pulsatility index and significant decreases of ratio were observed. These parameters calculated by measuring of renal blood flow velocity are known to well correlate with parenchymal vascular resistance. We speculate that these changes in renal parenchymal blood flow velocity are triggered by the tissue damages caused by the exposure to shock wave. The recovery of renal blood flow velocity may depend on the recovery of the tissue damages. Ultrasound color doppler method may make it possible to monitor the recovery of tissue damages induced by shock wave and may provide us with an useful information to determine when to repeat ESWL if needed.

Adult↗
PubMed1992

Analysis of pulmonary venous flow velocity patterns in hypertensive hearts: its complementary value in the interpretation of mitral flow velocity patterns.

Although the Doppler mitral flow velocity pattern changes in accordance with the degree of left ventricular diastolic dysfunction, it is "normalized" in the presence of heart failure. In this study the pulmonary venous flow velocity pattern was characterized in 43 hypertensive patients with and without heart failure to clarify whether analysis of the pulmonary venous flow velocity pattern provides complementary information in the interpretation of the mitral flow velocity pattern. The mitral flow velocity pattern in 32 hypertensive patients without heart failure was characterized by decreases in the peak early diastolic filling velocity (E) and the ratio of E to peak filling velocity at atrial contraction. The mitral flow velocity pattern was "normalized" in 11 patients with heart failure, with no differences in any mitral flow velocity pattern indexes as compared with 24 normal subjects. The pulmonary venous flow velocity pattern in hypertensive patients without heart failure was characterized by a decreased peak diastolic forward flow velocity (D) and an increased ratio of peak systolic forward flow velocity (S) to D (S/D ratio). In patients with heart failure, D was higher and the S/D ratio was lower compared with hypertensive patients without heart failure (p less than 0.01, p less than 0.01) and normal subjects (p less than 0.01, p less than 0.01). Thus the pulmonary venous flow velocity pattern appeared to be more reliable than the mitral flow velocity pattern in differentiating subgroups of patients with hypertension. Analysis of the pulmonary venous flow velocity pattern in conjunction with the mitral flow velocity pattern provides important and complementary information in the interpretation of the mitral flow velocity pattern in hypertensive patients with and without heart failure.

Blood Flow Velocity↗
PubMed1992

Adverse effects of epinephrine in patients with advanced left ventricular dysfunction: analysis of ventriculo-arterial coupling.

We examined the response of ventriculo-arterial coupling to epinephrine in 19 patients with normal left ventricular function and with left ventricular dysfunction of various degrees using a conductance catheter. They were divided into three groups: group I, seven patients without left ventricular wall motion abnormality; group II, six patients with ejection fraction of 45-60%; group III, six patients with ejection fraction of 28-40%. Changes in the slope of the end-systolic pressure-volume relationship (end-systolic elastance), the effective arterial elastance, the ratio of effective arterial elastance to end-systolic elastance and the ventricular work efficiency during administration of two different doses of epinephrine (0.05 and 0.1 micrograms/kg/min) were compared among the three groups. At baseline there were no significant differences among the three groups in the ratio of effective arterial elastance to end-systolic elastance, or ventricular work efficiency. At the lower dose of epinephrine, the mean ratio of effective arterial elastance to end-systolic elastance decreased and the mean ventricular work efficiency increased in any groups. At the higher dose of epinephrine the mean ratio of effective arterial elastance to end-systolic elastance further decreased and the mean ventricular work efficiency further increased in groups I and II. However, the mean ratio of effective arterial elastance to end-systolic elastance did not decrease but the mean ventricular work efficiency even decreased in group III. Thus, in patients with advanced left ventricular dysfunction, even a high dose of epinephrine does not modulate the ventriculo-arterial coupling to increase ventricular work efficiency.

Aged↗
PubMed1992

Role of atrial contraction and synchrony of ventricular contraction in the optimisation of ventriculoarterial coupling in humans.

OBJECTIVE: To examine the effects of pacing modes on the interaction between the left ventricle and arterial system in humans. DESIGN: The slope of the end systolic pressure-volume relation (end systolic elastance), effective arterial elastance, the ratio of effective arterial elastance to end systolic elastance, and mechanical energy efficiency were compared under different pacing modes (atrial, atrioventricular, and ventricular). PATIENTS: Nine male patients with sick sinus syndrome who had cardiac catheterisation for diagnosis and to see whether they needed a pacemaker. INTERVENTIONS: A conductance catheter with tip-manometer was inserted into the left ventricle to obtain pressure-volume loops, and two pacing catheters were inserted into the right atrium and into the right ventricle respectively. RESULTS: End systolic elastance was lower in atrioventricular pacing than in atrial pacing, but effective arterial elastance was not significantly different. End systolic elastance was lower in ventricular pacing than in atrioventricular pacing, and effective arterial elastance was higher in ventricular pacing than in atrioventricular pacing. Consequently the ratio of effective arterial elastance to end systolic elastance was lowest in atrial pacing and highest in ventricular pacing, and mechanical energy efficiency was highest in atrial pacing and lowest in ventricular pacing. CONCLUSIONS: Atrial contraction and synchronous ventricular contraction independently optimise ventriculoarterial coupling in terms of a transfer of energy. Thus atrial pacing gives the best ventriculo-arterial coupling among these pacing modes.

Adult↗
PubMed1992

Lack of myocardial perfusion immediately after successful thrombolysis. A predictor of poor recovery of left ventricular function in anterior myocardial infarction.

BACKGROUND: We investigated myocardial perfusion dynamics after thrombolysis and its clinical implications. METHODS AND RESULTS: We studied 39 patients with acute anterior myocardial infarction (AMI). Myocardial contrast echocardiography (MCE) was performed before and immediately after successful reflow with intracoronary injection of sonicated Ioxaglate. The average segmental score by two-dimensional echocardiography (graded 0, normal, to 3, akinetic/dyskinetic) and global ejection fraction (left ventricular ejection fraction, LVEF%) by left ventriculography were measured at 1 day and at 4 weeks after reflow. Hypokinesis in the infarct region was assessed by the centerline method and expressed in terms of standard deviations (regional wall motion [RWM]: SD/chord) of normal. Immediately after reflow, 30 of 39 patients (group A) showed significant contrast enhancement within the risk area. The other nine patients (23%, group B), however, showed the residual contrast defect in the risk area (myocardial no reflow). There were no significant differences in the elapsed time, angiographic collateral grade, and degree of residual stenosis between group A and group B. Before reflow, both groups exhibited similar levels of global and regional left ventricular function. Improvement in global (LVEF, average segmental score) and regional left ventricular function was greater in group A than in group B (average segmental score, 0.44 +/- 0.41 versus 0.97 +/- 0.36, p less than 0.01; LVEF, 56.4 +/- 13.4 versus 42.7 +/- 8.9, p less than 0.05; RWM, -1.87 +/- 0.85 versus -3.18 +/- 0.52, p less than 0.005). CONCLUSIONS: MCE demonstrates that angiographically successful reflow cannot be used as an indicator of successful myocardial reperfusion in AMI patients. The residual contrast defect in the risk area demonstrated immediately after reflow is a predictor of poor functional recovery of the postischemic myocardium.

Coronary Circulation↗