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Biomedical subjects

T Masuyama

Publications and source records attributed to T Masuyama.

At least 127 records · Page 7Linked to original sources
PubMed1989

Effects of atrioventricular interval on left ventricular diastolic filling assessed with pulsed Doppler echocardiography.

Effects of changes in atrioventricular interval on left ventricular diastolic filling were studied using pulsed Doppler echocardiography in 14 patients with programmable dual chamber pacemakers. Peak early diastolic filling velocity (E) and peak atrial filling velocity (A) were measured from the transmitral flow velocity pattern at three different atrioventricular intervals under the same pacing rate of 80 beats.min-1 in each patient. When the atrioventricular interval was switched from intermediate [148(SD10) ms] to short [68(11) ms], stroke volume did not change significantly [60(14) to 58(13) ml], but E increased from 39(12) to 44(11) cm.s-1 (p less than 0.05), and A decreased from 48(8) to 38(9) cm.s-1 (p less than 0.05). At the short atrioventricular interval, incomplete atrial emptying by the atrial contraction seemed to cause a reciprocal increase in the early diastolic filling. When the atrioventricular interval was switched from intermediate to long [234(16) ms], stroke volume, E and A did not change significantly [57(14) ml, 37(13) cm.s-1, 51(8) cm.s-1 respectively]. At the short and long atrioventricular intervals, atrial filling always changed in the direction opposite to that of early diastolic filling. Changes in stroke volume as well as peak early diastolic filling velocity caused by altering atrioventricular interval were pronounced in aged patients and patients with decreased early diastolic filling. In conclusion, left ventricular diastolic filling patterns can be affected by atrioventricular interval even without any concomitant pathological changes in the left atrial or ventricular function. These effects should not be taken lightly, especially in patients with decreased left ventricular early diastolic filling.

Adolescent↗
PubMed1989

Visualization of subendocardial myocardial ischemia with myocardial contrast echocardiography in humans.

Previous studies indicate the degree of myocardial echo contrast enhancement may be related to regional myocardial perfusion. In this study, myocardial contrast echocardiography was used to characterize changes in the transmural myocardial blood flow distribution that were provoked by rapid atrial pacing in 11 patients with one-vessel coronary artery disease. Ten patients without coronary artery disease served as controls. Myocardial contrast echocardiography was performed by intracoronary injection of 2 ml hand-agitated amidotrizoate sodium meglumine (Urografin-76) and by imaging a short-axis view of the left ventricle with two-dimensional echocardiography before and during injection of the contrast agent. The two-dimensional echocardiographic images at end diastole, before and after injection of the contrast agent, were digitized off-line into a 512 x 512 pixel matrix with 256 gray levels/pixel to quantify the degree of the enhancement of the peak gray level after injection. Transmural myocardial blood flow distribution was evaluated by measuring the ratio of the enhanced gray level in the endocardial half (endo) to that in the epicardial half (epi) (endo:epi gray level ratio) in the anteroseptal, posterolateral, and inferior segments before and just after rapid atrial pacing in each patient. In patients without coronary artery disease, there were no differences in the endo:epi gray level ratio between any of the three segments both before and after pacing. Mean values of the three segments were 0.95 +/- 0.08 before pacing and 0.90 +/- 0.13 after pacing, respectively. In contrast, in patients with coronary artery disease, the endo:epi gray level ratio for the segment supplied with stenotic coronary artery decreased after pacing (0.40 +/- 0.21 vs. 0.93 +/- 0.18, p less than 0.01), probably reflecting subendocardial myocardial ischemia, whereas that for the segment supplied with nonstenotic coronary artery remained unchanged (0.88 +/- 0.20 vs. 0.99 +/- 0.23, NS). Thus, changes in transmural myocardial blood flow distribution with rapid pacing, which may be due to transient subendocardial ischemia, are visualized with myocardial contrast echocardiography.

Adult↗
PubMed1989

Mitral prosthesis malfunction. Comparative Doppler echocardiographic studies of mitral prostheses before and after replacement.

To assess the influence of mitral prosthesis malfunction on various Doppler echocardiographic indexes, we studied the changes in the peak mitral flow velocity during early diastolic filling phase (Vmax), the mean transprosthesis pressure drop from the simplified Bernoulli equation, the mitral valve area by the pressure half-time method, and the left ventricular isovolumic relaxation time in 15 patients before and after replacement of the malfunctioning mitral prosthesis using continuous wave Doppler echocardiography. Examination of the 15 replaced prostheses revealed a torn or perforated leaflet in 12 valves and a sewing ring dehiscence in one valve. Additional restricted leaflet motion (classified as mild obstruction) was seen in three of these 13 valves. In the remaining two valves, severe prosthesis obstruction was noted. Changes in the Doppler indexes between the preoperative and postoperative study were present in all patients regarding Vmax (mean, 2.2 +/- 0.3 versus 1.6 +/- 0.2 m/sec; p less than 0.001), mean gradient (mean, 9 +/- 5 versus 5 +/- 0.8 mm Hg; p less than 0.001), and isovolumic relaxation time (mean, 47 +/- 12 msec versus 80 +/- 13 msec; p less than 0.001). The mean mitral valve area remained virtually unchanged (2.3 +/- 0.9 versus 2.6 +/- 0.3 cm2; p = NS) but increased postoperatively in each patient with preoperative mild or severe prosthesis obstruction without concomitant aortic regurgitation. Our conclusion is that the peak mitral flow velocity, the mean gradient, and the isovolumic relaxation time are useful parameters in the differentiation of normal and abnormal mitral prosthesis function but may not define the underlying lesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Ultrasonic tissue characterization of human hypertrophied hearts in vivo with cardiac cycle-dependent variation in integrated backscatter.

Integrated ultrasonic backscatter (IB) is a noninvasive measure of the acoustic properties of myocardium. Previous experimental studies have indicated that altered acoustic properties of the myocardium are reflected by the magnitude of variation of IB during the cardiac cycle. In our study, cardiac cycle-dependent variation of IB was noninvasively measured using a quantitative IB imaging system in 12 patients with uncomplicated pressure-overload hypertrophy and 13 patients with hypertrophic cardiomyopathy. Sixteen normal subjects served as a control. The magnitude of cardiac cycle-dependent variation of IB for the posterior wall was 6.0 +/- 0.9 dB in normal subjects, 5.7 +/- 0.8 dB in the patients with uncomplicated pressure-overload hypertrophy, and 6.7 +/- 2.1 dB in the patients with hypertrophic cardiomyopathy. There were no significant differences among any of these groups. In contrast, the magnitude of cardiac cycle-dependent variation of IB for the septum was significantly smaller in the patients with uncomplicated pressure-overload hypertrophy (2.8 +/- 1.3 dB) and in the patients with hypertrophic cardiomyopathy (3.1 +/- 2.3 dB) than in normal subjects (4.9 +/- 1.0 dB). The magnitude of cardiac cycle-dependent variation of IB was smaller as the wall-thickness index increased (r = -0.53, p less than 0.01, n = 82 for all data). This IB measure also correlated with percent-systolic thickening of the myocardium (r = 0.67, p less than 0.01, n = 82). Thus, alteration in the magnitude of cardiac cycle-dependent variation of IB was observed in hypertrophic hearts and showed apparent regional myocardial differences.

Adult↗
PubMed1989

[Evaluation of function of human collateral coronary arteries using myocardial contrast echocardiography].

The morphology of collateral vessels can be imaged by coronary angiography, but no method has been available for evaluating their function. This is a report of the use of regional myocardial perfusion to visualize collateral flow by means of myocardial contrast echocardiography in 28 patients with old myocardial infarction. Myocardial contrast echocardiography was accomplished by the intracoronary injection of two ml agitated amidotrizoate sodium meglumine. Short-axis images of the left ventricle were recorded on video tape. Those images were digitized off-line into a 512 x 512 pixel matrix. Using coronary angiography, the morphology and function of the collateral vessels were evaluated, then classified as poor, moderate or good. Myocardial perfusion was evaluated using the enhanced gray level after contrast injection, and the level was compared with the morphology and degree of collateral development. The enhanced gray level was evaluated arbitrarily as 3 +/- 2 U (mean +/- S.D.) in the "poor" group; 13 +/- 6 U in the "moderate" group; and 20 +/- 11 U in the "good" group (p less than 0.01 vs the "poor" group; NS vs the "moderate" group). Regional myocardial perfusion via the collateral vessels was generally proportional to the morphology. However, there were a few discrepancies between these two parameters.

Aged↗
PubMed1989

[Noninvasive evaluation of changes in stroke volume and left ventricular filling dynamics. Produced by atrioventricular interval manipulation].

To evaluate the effects of atrioventricular pacing interval on hemodynamics, we studied the changes in stroke volume and left ventricular filling dynamics in fourteen consecutive patients with implanted atrioventricular pacemakers using a Doppler echocardiographic technique. Twelve patients had sick sinus syndrome and 2 had complete atrioventricular block. Stroke volume was determined as the time-velocity integral of the pulsed Doppler recordings at the aortic annulus multiplied by the area of the aortic annulus obtained by 2-dimensional echocardiography. Left ventricular filling velocity was measured at the mitral annulus by the pulsed Doppler technique to provide the time-velocity integral of rapid filling (TVI-R) and that of atrial filling (TVI-A). No significant change in stroke volume was noted during the atrioventricular interval manipulation. TVI-R was greater with short atrioventricular intervals than that with the long atrioventricular intervals. On the contrary, TVI-A was greater with long atrioventricular intervals than that with short atrioventricular intervals. These results suggested that there is a compensatory mechanism in the left ventricular filling dynamics to keep the stroke volume constant despite the change in the atrioventricular interval. However, in patients with high atrial filling to rapid filling ratio (A/R), the stroke volume varied with change of atrioventricular interval, suggesting that the compensatory mechanism was not sufficient in such patients. We conclude that Doppler echocardiography is a useful, noninvasive technique to assess the changes in the hemodynamics produced by atrioventricular interval manipulation in patients with implanted atrioventricular pacemakers.

Adult↗
PubMed1989

[Discrepancies between wall motion abnormalities and regional myocardial perfusion in patients with myocardial infarction: evaluation by myocardial contrast echocardiography].

Regional myocardial perfusions obtained by myocardial contrast echocardiography were compared with wall motion abnormalities evaluated by two-dimensional echocardiography in 26 patients with old myocardial infarction (12 with a QS pattern and 14 with a non-QS pattern on electrocardiograms). Myocardial contrast echocardiography was performed by the intracoronary injection of 2 ml of hand-agitated Urografin-76, and short-axis views of the left ventricle were recorded on VTR. Regional myocardial perfusion was categorized using a three-point scale based on the gray levels, and was compared with wall motion abnormalities of the corresponding region as assessed by two-dimensional echocardiography.

Adult↗
PubMed1988

Effects of acetylcholine on epicardial coronary arteries after cardiac transplantation without angiographic evidence of fixed graft narrowing.

The coronary response to acetylcholine was evaluated in 10 patients who had had cardiac transplantation 1 to 8 years earlier and in 4 patients who did not undergo transplantation. All 14 patients had no angiographic evidence of fixed coronary arterial narrowing. Acetylcholine was infused in 10-fold increasing concentrations (10(-6) to 10(-2) M) into the midpoint of the left anterior descending coronary artery by an infusion catheter. Administration was terminated when either vasoconstriction was noted at fluoroscopy or when the maximal acetylcholine concentration was reached. Vascular responses were evaluated by quantitative angiography. All 14 patients had a decrease in coronary lumen size in response to acetylcholine. The mean percentage of vasoconstriction was 37 +/- 24% (p less than 0.001). Combined infusion of nifedipine and the maximal vasoconstricting dose of acetylcholine did not result in a significant reversal of coronary vasoconstriction in all 10 cardiac transplantation patients. It was concluded that acetylcholine is a potent coronary vasoconstrictor in patients who had cardiac transplantation and possibly lacks vasodilating effects in most normal patients without angiographic evidence of coronary artery disease, thus suggesting that acetylcholine might not be a suitable pharmacologic agent for testing endothelial cell integrity.

Acetylcholine↗
PubMed1988

Effects of changes in coronary stenosis on left ventricular diastolic filling assessed with pulsed Doppler echocardiography.

To determine the effects of changes in coronary stenosis on left ventricular diastolic filling, diastolic filling was serially examined before and after percutaneous transluminal coronary angioplasty using pulsed Doppler echocardiography in 50 patients with stable exertional angina pectoris. Peak rapid filling velocity and the ratio of peak atrial filling to peak rapid filling velocities were measured from the transmitral flow velocity pattern before and 2 and 9 days after coronary angioplasty. Peak rapid filling velocity increased and the ratio of peak atrial filling to peak rapid filling velocities decreased gradually after coronary angioplasty. The improvement in left ventricular diastolic filling was greater in patients with severe (greater than 90%) coronary stenosis than in patients with mild (less than or equal to 90%) coronary stenosis. In the long-term follow-up period, the improved left ventricular diastolic filling worsened in only 11 patients with marked progression to greater than 90% coronary stenosis. Thus, left ventricular diastolic filling improved gradually after coronary angioplasty, possibly reflecting post-ischemic "stunned" myocardium. Serial examinations of left ventricular diastolic filling with pulsed Doppler echocardiography may be a means of noninvasively assessing the temporal changes in the coronary stenosis and predicting the occurrence of coronary restenosis after coronary angioplasty.

Adult↗
PubMed1988

Value and limitations of Doppler echocardiography in the quantification of stenotic mitral valve area: comparison of the pressure half-time and the continuity equation methods.

Two Doppler methods, the pressure half-time method proposed by Hatle and the method based on the equation of continuity, were used to estimate stenotic mitral valve area noninvasively, and the accuracy of these methods was examined in patients with and without associated aortic regurgitation. Mitral valve area determined at catheterization by the Gorlin formula was used as a standard of reference. The study population consisted of 41 patients with mitral stenosis, and 20 of the 41 patients had associated aortic regurgitation. According to the equation of continuity, mitral valve area was determined as a product of aortic or pulmonic annular cross-sectional area and the ratio of time velocity integral of aortic or pulmonic flow to that of the mitral stenotic jet. Mitral valve area was determined by the pressure half-time method as 220/pressure half-time, the time from the peak transmitral velocity to one-half the square root of the peak velocity on the continuous-wave Doppler-determined transmitral flow velocity pattern. The pressure half-time method tended to overestimate catheterization measurements, and the correlation coefficient for this relation was .69 (SEE = 0.44 cm2). The correlation coefficient improved to .90 when the patients with associated aortic regurgitation were excluded. Mitral valve areas determined by the continuity equation method correlated well with catheterization measurements at a correlation coefficient of .91 (SEE = 0.24 cm2), irrespective of the presence of aortic regurgitation. The ratio of the time-velocity integral or aortic or pulmonic flow to the time-velocity integral of mitral stenotic jet also correlated well with mitral valve area determined by catheterization at a correlation coefficient of .84 (SEE = 0.10).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Transesophageal two-dimensional echocardiography and color Doppler flow velocity mapping in the evaluation of cardiac valve prostheses.

To determine the value of transesophageal ultrasound in the assessment of cardiac valve prostheses, 14 patients with clinically suspected mitral prosthesis malfunction were studied by transthoracic and transesophageal two-dimensional imaging as well as by color Doppler flow velocity mapping (color Doppler). Patients underwent left ventricular angiography (n = 13), surgery (n = 11), or both angiography and surgery (n = 10). Nine patients had only mitral valve replacement, four patients had both mitral and aortic valve replacement, and one patient had mitral, aortic, and tricuspid valve replacement. There were 16 biological and four mechanical prostheses. The degree of mitral regurgitation was graded by both transthoracic and transesophageal color Doppler according to the area of the regurgitant jet visualized and was compared with a three-point classification of mitral regurgitation by left ventricular angiography judged by observers blinded to the echocardiographic results. All transesophageal studies were performed without complication and were well tolerated. The pathological morphology of the mitral prosthesis was additionally or more clearly visualized by transesophageal two-dimensional imaging and subsequently proven at surgery in three patients with flail leaflets and one patient with a vegetation compared with images obtained by the transthoracic approach. Valvular regurgitation was graded by the transthoracic approach as absent in four patients, mild in two patients, moderate in five patients, and severe in only three patients. The transesophageal assessment showed absence of mitral regurgitation in two patients, moderate regurgitation in two patients, and severe regurgitation in 10 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Effect of OPC-8212 (2(1H)-quinolinone), a new inotropic agent, on myocardial energy metabolism in patients with coronary heart disease.

We examined the effects of a new inotrope, OPC-8212 (OPC: 2(1H)-quinolinone), on coronary sinus flow (CSF), myocardial oxygen consumption, myocardial lactate extraction ratio (LER), cardiac index (CI) and pulmonary arterial diastolic pressure (PADP) in eleven patients with prior myocardial infarction. Measurements were taken before (control) and 8 hours after administration of OPC (480 mg, p.o.). A cardiac function curve was obtained in each stage with rapid intravenous administration of 500 ml of saline (loaded state) after baseline measurements. There was a significant increase in the cardiac index and decrease in the pulmonary arterial diastolic pressure in the loaded state after OPC. Thus the ventricular function curve was shifted to the left and showed a steep incline, indicating an increased inotropic state. On the other hand, myocardial oxygen consumption and myocardial lactate extraction ratio were unchanged. Thus we concluded that OPC improved cardiac performance without increasing myocardial oxygen consumption.

Adult↗
PubMed1988

[Regional myocardial perfusion in ischemic heart disease assessed by myocardial contrast echocardiography].

Myocardial contrast echocardiography is a new cardiovascular imaging technique that can be used to evaluate regional myocardial perfusion. Regional myocardial perfusion was studied in 12 patients with normal coronary arteries, 14 patients with old myocardial infarction, four patients with acute myocardial infarction, and 15 patients with effort angina. Conventional two-dimensional echo imaging was obtained during intracoronary injections of relatively small volumes (2 ml) of agitated Urografin-76. The echo intensities were measured before and after injecting contrast agents and the subtraction images were composed by a high-speed image processor (NEXUS 6400). Clear myocardial images were obtained in 10 of 12 the patients with normal coronary arteries, and they reflected well the epicardial arterial architecture by coronary angiography. In cases of old myocardial infarction, the infarcted areas appeared as contrast defects in seven and as slightly enhanced areas in three of the 10 patients. In cases of acute myocardial infarction, contrast defect areas in the myocardial images were less in two cases of successful early coronary thrombolysis or percutaneous transluminal coronary angioplasty (PTCA). However, contrast defects remained unchanged despite good recanalization in one case of delayed PTCA. In cases of effort angina, anginal attacks were successfully induced by rapid atrial pacing in six of the 15 patients. In four of the six patients, contrast enhancement in myocardial imaging during anginal attack decreased more in the endocardial than in the epicardial myocardium, possibly reflecting subendocardial ischemia. It is concluded that this technique can identify regional myocardial perfusion, which is not revealed by coronary angiography, and it is therefore useful for the clinical analysis of ischemic heart disease.

Angina Pectoris↗
PubMed1987

Acute electrocardiographic changes associated with successful coronary thrombolysis in acute myocardial infarction.

In this study ECG changes were analyzed to assess the acute effects of antegrade blood flow on the ECG in patients with AMI. The study population consisted of 22 patients with MI in whom the totally occluded left anterior descending artery (LAD) or right coronary artery (RCA) was recanalized by intracoronary urokinase infusion (recanalized group) and 14 patients in whom the occluded coronary artery was not successfully recanalized (control group). No significant difference was found in the sum of ST segment elevation (V2-V4 leads for the LAD-occluded group, II, III and aVF leads for the RCA-occluded group) before urokinase infusion. In the recanalized group sigma ST abruptly increased in 5 min after recanalization in 13 of 16 LAD-occluded patients from 1.49 +/- 0.89 mV to 2.44 +/- 1.67 mV (p less than 0.005), and in 4 of 6 RCA-occluded patients from 0.66 +/- 0.12 mV to 1.42 +/- 0.52 mV (p less than 0.01). However increased sigma ST in the recanalized group was reduced to the control value existing before recanalization within 30 min after recanalization and continued to decline more rapidly than in the control group. These transient ST segment elevations were not correlated with long-term angiographic determinants of left ventricular function. We conclude that ST segment shows abrupt augmentation after successful thrombolysis and that continuous ST segment monitoring is useful for assessing thrombolysis in AMI.

Adult↗
PubMed1986

Noninvasive evaluation of aortic regurgitation by continuous-wave Doppler echocardiography.

Continuous-wave Doppler echocardiography was used to examine the aortic regurgitant flow velocity pattern in 32 patients with aortic regurgitation (AR) and 10 patients without AR. The aortic regurgitant flow velocity patterns, characterized by a rapid rise in flow velocity immediately after closure of the aortic valve, high peak flow velocity, and a gradual deceleration until the next aortic valve opening, were successfully obtained in 30 of the 32 patients with AR (sensitivity 94%, specificity 100%). The velocity decline was greater in patients with severe AR; thus, the slope of the velocity decline (deceleration) and the time to decline to half the peak velocity (half-time index) were measured from the flow velocity pattern. The deceleration became greater and the half-time index shortened in accordance with angiographic grading of AR (p less than .01). The deceleration and the half-time index also correlated well with the aortic regurgitant fraction (r = .79, p less than .01; r = -.89, p less than .01). Because the half-time index could be measured easily and independently of Doppler incident angle, it seemed a simple and accurate index of assessing the severity of AR. Thus continuous-wave Doppler echocardiography permitted the noninvasive evaluation of AR.

Adult↗
PubMed1986

Continuous-wave Doppler echocardiographic detection of pulmonary regurgitation and its application to noninvasive estimation of pulmonary artery pressure.

Continuous-wave Doppler echocardiography was used to estimate pulmonary artery pressures by measuring pulmonary regurgitant flow velocity in 21 patients with pulmonary hypertension (mean pulmonary artery pressure greater than or equal to 20 mm Hg) and 24 patients without pulmonary hypertension. The pulmonary regurgitant flow velocity patterns, characterized by a rapid rise in flow velocity immediately after closure of the pulmonary valve and a gradual deceleration until the next pulmonary valve opening, were successfully obtained in 18 of the 21 patients with pulmonary hypertension and in 13 of the 24 patients without pulmonary hypertension. As pulmonary artery pressure increased, pulmonary regurgitant flow velocity became higher; the pulmonary artery-to-right ventricular pressure gradient in diastole (PG) was estimated from the pulmonary regurgitant flow velocity (V) by means of the simplified Bernoulli equation (PG = 4V2). The Doppler-determined pressure gradient at end-diastole correlated well with the catheter measurement of the pressure gradient at end-diastole (r = .94, SEE = 3 mm Hg) and with pulmonary artery end-diastolic pressure (r = .92, SEE = 4 mm Hg). The peak of Doppler-determined pressure gradient during diastole correlated well with mean pulmonary artery pressure (r = .92, SEE = 5 mm Hg). Thus continuous-wave Doppler echocardiography was useful for noninvasive estimation of pulmonary artery pressures.

Adolescent↗
PubMed1986

Beneficial effects of atrioventricular sequential pacing on cardiac output and left ventricular filling assessed with pulsed Doppler echocardiography.

There has been increased interest in the beneficial effects of atrio-ventricular (AV) pacing over ventricular (V) pacing. This study attempted to evaluate the changes in cardiac output and left ventricular filling dynamics when the pacing mode was switched from V pacing to AV pacing. Study population consisted of 26 patients with multiprogrammable AV pacemakers. Cardiac output was determined as a product of echocardiographically determined cross sectional area of the aortic annulus and Doppler-determined velocity integral of left ventricular outflow over systole. Left ventricular peak rapid filling rate (PFR) and peak atrial filling velocity to peak rapid filling velocity ratio (A/R) were determined from measurements at the mitral annulus. Cardiac output showed a significant improvement when the pacing mode was switched from V to AV pacing, and the percent change ranged from 3 to 73% (average 26%). The improvement in cardiac output brought about by AV synchrony was greater in patients with smaller PFR (r = -0.71, p less than 0.01) and larger A/R ratio (r = 0.77, p less than 0.01). On the other hand, PFR was greater with V pacing than with AV pacing. Greater increment of the PFR was produced by the loss of atrial contraction in patients with smaller PFR (r = -0.82, p less than 0.01) and larger A/R ratio (r = 0.76, p less than 0.01). Thus, AV pacing provides a great improvement in left ventricular filling, i.e., cardiac output, which cannot be obtained with V pacing even with the compensatory enhancement of left ventricular rapid filling. These beneficial effects of AV pacing seemed to be greater in patients with impaired left ventricular rapid filling.

Adolescent↗