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Using digital subtraction coronary angiography (DSA), we evaluated the regional myocardial coronary blood flow reserve (rMFR) in 18 patients with hypertrophic cardiomyopathy (HCM). There were 13 patients with asymmetrical septal hypertrophy (ASH), and 5 with asymmetrical apical hypertrophy (AAH). Eight subjects without apparent cardiac abnormality served as controls. Relations between the rMFR and regional wall thickness as determined by echocardiography were also investigated. Peak contrast density (Cm) and time to Cm (Tm) were measured from digital angiograms at the middle and distal ventricular septum (VS) and at the apical and left ventricular posterior wall (PW). The rMFR of each region of interest was expressed as the ratio of Cm/Tm at the baseline and at peak hyperemic response induced by intracoronary administration of papaverine. The rMFR was significantly lower at the VS and apex in HCM than in controls: middle VS, 1.9 +/- 0.5 vs 3.9 +/- 0.5, p < 0.001; distal VS, 2.0 +/- 0.5 vs 4.4 +/- 0.9, p < 0.001; and the apex, 2.0 +/- 0.7 vs 4.5 +/- 1.6, p < 0.01. However, it did not differ at the PW; 2.6 +/- 0.9 vs 3.0 +/- 0.9 between the 3 groups. The middle VS and apex, where the wall was the thickest, had the lowest rMFR in ASH and AAH. Furthermore, at the VS and apex, a curvilinear relationship was observed between the rMFR and wall thickness (rMFR = -0.88 in WT + 2.39, r = -0.57, p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

The anaerobic threshold (AT) is regarded an objective parameter for evaluating exercise tolerance, but its relationship to the improvement of myocardial ischemia remains uncertain. To investigate this relationship, submaximal treadmill exercise tests were performed for 15 consecutive patients with angina pectoris who had undergone successful percutaneous transluminal coronary angioplasty (PTCA). Before and after PTCA, the AT was determined using cardiorespiratory monitoring, while the patients were receiving their usual vasodilator medications. 1) Before PTCA, the minute oxygen uptake (VO2) at the AT correlated well with the peak VO2 (r = 0.92, p < 0.002). The VO2 at the AT, however, showed less correlation (r = 0.71, p < 0.002) with the VO2 at ST segment depression, while the latter parameter correlated closely with the peak VO2 (r = 0.91, p < 0.002). 2) After PTCA, exercise time, peak VO2, and the double product at peak exercise increased significantly (from 640.1 +/- 212.2 to 772.9 +/- 230.0 sec, p < 0.001, from 19.1 +/- 5.2 to 22.4 +/- 4.9 ml/min/kg, p < 0.05, and from 19.7 +/- 5.0 x 10(3) to 23.7 +/- 4.5 x 10(3), p < 0.001, respectively). However, the VO2 at the AT did not increase significantly (from 15.8 +/- 4.1 to 16.6 +/- 3.5 ml/min/kg, p = NS). The heart rate, systolic blood pressure, and double product at the AT did not change significantly. In conclusion, in patients with angina pectoris, the AT is apparently related to the onset of myocardial ischemia. However, the AT does not necessarily reflect acute improvement of myocardial ischemia immediately after PTCA.

Patients with hypertrophic cardiomyopathy (HCM) are known to have ischemic events and decreased coronary flow reserve, but the variabilities in the site and degree of fall between patients with this disease have not been clarified. To elucidate these variabilities, we performed exercise myocardial single photon emission computed tomography (SPECT) using double dose method in 30 patients with HCM (6 with obstruction, 17 with non-obstruction, 7 with apical hypertrophy) and 10 normals. Then, the delta Fract (coronary flow reserve index) map was obtained for each subject. Exercise and then rest Tl-201 myocardial scintigraphy were performed after administration of Tl-201. The data were reconstructed, making the circumferential curves from the same level of short-axis imaging during exercise and at rest. By subtracting the values at rest from the values during exercise, which were divided by the values at rest, delta Fract in each frame was obtained, and described on the unfolded map. The extent and degree of coronary flow reserve were visually estimated by this delta Fract map. Patients were categorized into 5 groups: diffuse fall of coronary flow reserve (D-type), 6 cases; localized fall of the septum or lateral wall (L-type), 5 cases; fall of apical region (A-type), 5 cases; mild fall (M-type), 6 cases; and normal pattern (N-type), 8 cases. We concluded that delta Fract map is useful for evaluating the extent and degree of coronary flow reserve in HCM.

The clinical and pathophysiological significance of apical sequestration, in which an apical cavity was sequestered from the remainder of the left ventricle by cavity obliteration was investigated in patients with hypertrophic cardiomyopathy (HCM). Among 196 consecutive patients, 24 with apical sequestration and 70 control subjects proven to have no sequestration with left ventriculography were selected for this study using echocardiography combined with Doppler color flow imaging. Various cardiac disorders occurred significantly more frequently in patients with apical sequestration than in the 70 controls: NYHA > or = II, 83% vs 51%; thromboembolism, 17% vs 3%; ventricular tachycardia, 47% vs 11%; and apical asynergy, 75% vs 4%. Continuous Doppler ultrasound revealed that all 24 patients with sequestration had a high systolic blood flow velocity across the obliterated cavity (2.7 +/- 0.9 m/s). During isovolumic relaxation or early diastolic filling or both, 21 of them had paradoxical jet flow directed toward the basal cavity away from the apex, with the peak flow velocity ranging from 1.0 m/s to 3.5 m/s (mean 1.9 +/- 0.7). The maximal diastolic pressure gradient across the obliterated cavity ranged between 4 mmHg and 49 mmHg using the simple Bernoulli's equation, which suggested a significantly higher pressure in the sequestered apical chamber during early diastole. Patients with sequestration were classified into 2 groups; 17 with (group A) and 7 without (group B) apical hypertrophy. The time interval from the closing of the aortic valve to the onset of filling into the sequestered cavity was longer in group A than in group B (401 +/- 191 vs 131 +/- 145 ms, p < 0.01) as assessed by the pulsed Doppler technique. Angiographic asynergy of the apex was more frequent in group A than in group B (100 vs 29%, p < 0.01). In group B, the midventricular cavity was incompletely obliterated throughout the cardiac cycle; whereas, in group A, it was obliterated completely in systole and partially in diastole. Apical sequestration is not uncommon in HCM; it is accompanied by abnormal segmental wall motion, which may be related to ventricular arrhythmias and thromboembolism. Prolonged cavity obliteration with a higher systolic apical pressure and a persistent diastolic intraventricular gradient may play a pathogenic role in apical aneurysmal formation in the absence of fixed coronary artery disease, particularly in patients with apical hypertrophy.

To determine the optimal balloon-to-artery ratio in percutaneous transluminal coronary angioplasty (PTCA), the effects of balloon size on the extent of residual stenosis, the incidence of coronary dissection, and the percentage of cases requiring repeat PTCA for restenosis were examined retrospectively. Fifty consecutive patients who underwent elective PTCA for simple and discrete lesion localized in the left anterior descending coronary artery were selected for this study. To measure the absolute cross-sectional area of the adjacent control segment of the artery, we developed a new method of quantitative coronary angiography, a hybrid of cinevideodensitometry and the edge detection method. The balloon-to-artery ratio was calculated as the cross-sectional area ratio between the control segment adjacent to the stenosis and the balloon which was visually selected by the operator during PTCA. Residual stenosis was determined as the percent area of stenosis by our hybrid method using cinevideodensitometry. The balloon-to-artery ratio ranged from 0.4 to 2.4, and a weak but significant inverse correlation (r = -0.51) was observed between the balloon-to-artery ratio and the extent of residual stenosis. In 23 patients whose balloon-to-artery ratios were less than 1.0, residual stenosis was greater (59.9 +/- 11.9% vs 46.0 +/- 19.6%, p < 0.05), and the percentage of repeat PTCA was higher (26% vs 4%, p < 0.05) than in the group of 27 patients whose balloon-to-artery ratios were higher than 1.0. The incidence of coronary dissection was similar in the 2 groups (9% vs 15%, ns). The percent area of stenosis before PTCA, the number of inflations, the inflation pressures, and the inflation times were also similar between these 2 groups. We concluded that the optimal balloon size is slightly more than the control segment dimensions of simple and discrete isolated stenoses of the left anterior descending artery treated at lower inflation pressures, and that an accurate measurement method of the coronary arterial dimensions is necessary to determine this optimal balloon size.

The serial electrocardiographic (ECG) changes of 20 patients with asymmetric apical hypertrophy (AAH) were retrospectively reviewed relative to their clinical symptoms, echocardiography and Doppler echocardiography, and thallium-201 perfusion scintigraphy. These patients were followed 4-18 years (mean 8 years). Patterns of the serial ECG changes were as follows: Seven patients (group Ia) had an increase of 10 mm or greater in the highest R wave amplitude in the precordial leads, with newly-developed giant T wave inversion. Five patients (group Ib) had relatively stable ECGs and the changes in the R wave amplitudes of less than 10 mm. Six patients (group IIa) had a decrease of 10 mm or greater in the highest R wave amplitude with mild decreases of negative T wave amplitudes. In the remaining two patients (group IIb) right bundle branch block developed. At the last follow-up study, group IIa had lower R wave amplitudes and longer QTc than did those in group I. The follow-up periods and their mean age did not differ among the groups. At the initial evaluation, exercise limitation was rare in group I; whereas, most of the patients in group II presented symptoms such as palpitation, chest pain or exertional dyspnea. These cardiac symptoms developed slowly but progressively during the follow-up period, and their incidence increased both in groups I and II at the final observation. Left ventricular (LV) wall thickness at the chordal level showed normal values and did not differ between the two groups, but apical wall thickness was greater in group II than in group I. Two-dimensional echocardiography showed a spade-like deformity of the LV in group II. In group I, the LV deformity was less marked and was not noted at the initial examination. Color Doppler echocardiography frequently revealed "paradoxical flow" expelled from the obliterated apex to the base in the early diastolic filling period in group II. Left ventriculography confirmed asynchronous contraction, hyperkinesis in the basal segment and dyskinesis at the apical segment, resulting in this abnormal intraventricular blood flow profiles. Serial studies by thallium-201 (TL) perfusion scintigraphy disclosed that four of the eight patients in group II developed localized hypoperfusion at the apex where a high and homogeneous uptake of TL was previously noted.(ABSTRACT TRUNCATED AT 400 WORDS)

For simple, non-invasive evaluations of coronary flow reserve during exercise, we investigated the coronary flow reserve index using the ratio of change of fractional distribution in the regional myocardium to oxygen demand. The subjects included 24 patients with effort angina pectoris and 11 normal volunteers. PTCA was performed for 11 patients. Using the biological properties of Tl-201, single photon emission computed tomography (SPECT) was performed at submaximal exercise and at rest by two successive injections of Tl-201 within a short time interval (double dose method). The correlation between the fractional distribution in the myocardium (delta-Fract) and the oxygen demand during exercise and at rest were evaluated. delta-Fract correlated well with the rate of change of the pressure rate product (delta-PRP), and delta-Fract/delta-PRP (CRI) was a good indicator of the coronary flow reserve index. CRI in the ischemic region correlated well with the percent area stenosis of the supplying coronary artery and improved with resolution of percent area stenosis of the target coronary artery after PTCA, but in some cases they were not above the normal range. CRI as obtained by exercise SPECT using the double dose method is useful for non-invasively estimating the coronary flow reserve during exercise, and it can be used for evaluating the effect before and after PTCA.

The aim of this study was to evaluate the value and limitations of stress thallium-201 scintigraphy in evaluating the viability of infarcted myocardial segments following percutaneous transluminal coronary angioplasty (PTCA) and aortocoronary bypass surgery. The relative thallium activity (RTA: the ratio of the count rate in the infarcted segment to that in the intact segment) obtained from delayed images of stress myocardial scintigraphy was used as an index of myocardial viability and was compared with the following parameters. 1) Thallium-201 myocardial perfusion images were made during transient coronary arterial occlusion (PTCA) in eight patients with old myocardial infarction. The RTA of delayed images after successful PTCA was compared with those of stress thallium-201 scintigraphy. There were no significant differences of the RTA between delayed images following PTCA and those of stress myocardial scintigraphy. We therefore, presumed that incomplete redistribution of the delayed images of stress thallium-201 scintigraphy did not truly reflect the degree of coronary stenosis. 2. Regional ejection fraction of the left ventricle after postextrasystolic potentiation (PESP) using equilibrium radionuclide ventriculography was studied in 18 patients with old myocardial infarction, and was compared with the RTA of delayed images of stress myocardial scintigraphy. A significant correlation was observed between the changes in regional ejection fraction by PESP and the RTA three hours after exercise. 3. The RTAs of early and delayed thallium-201 scintigrams were measured at rest in 30 patients with old myocardial infarction, and were compared with the RTA of delayed thallium 201 scintigrams after exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

To evaluate left ventricular diastolic properties during acute myocardial ischemia, transmitral flow patterns were analyzed by two-dimensional pulsed Doppler echocardiography. In a preliminary study of transient coronary artery occlusion in anesthetized open-chest dogs, the following results were obtained: decreased peak velocity of rapid filling, prolonged rapid filling period, and compensatory increase in the peak velocity of atrial filling. These changes occurred nearly concomitantly with decreased cardiac output, elevated left atrial and left ventricular end-diastolic pressures, and decreased left ventricular systolic pressures. With reperfusion of the coronary artery, these parameters rapidly returned to the base line values. In acute and transient myocardial ischemia induced by intracoronary balloon inflation during therapeutic percutaneous transluminal coronary angioplasty (PTCA) in man, similar changes in these parameters were observed, and the changes were more marked in PTCA for the left anterior descending artery as compared with that of the right coronary artery. In conclusion, noninvasive two-dimensional pulsed Doppler echocardiography is of practical use in evaluating deterioration of the diastolic function of the left ventricle during acute and transient myocardial ischemia.

To evaluate the influences of transient myocardial ischemia on transmitral blood flow velocity patterns, pulsed Doppler echocardiography was performed during coronary artery occlusion in 10 anesthetized open-chest dogs, and also during esophageal pacing or the administration of dipyridamole in 79 patients with coronary artery disease (CAD), and in 19 control subjects. During occlusion of the coronary artery, an abrupt decrease in the peak velocity of the rapid filling wave (R) was noted within one min simultaneously with rapid decrease of % wall thickening in the ischemic regions. The peak velocity of atrial filling was augmented compensatorily. Although the transmitral blood flow velocity pattern did not change in the controls with esophageal pacing, changes similar to those which were obtained during experimental studies were demonstrated in CAD patients. There were no significant differences between transmitral blood flow velocity patterns of patients with multivessel disease and those with single vessel disease. Ischemic changes in transmitral blood flow velocity patterns were not demonstrated in patients with mitral regurgitation. Sublingual nitroglycerin normalized post-pacing abnormal blood flow velocity patterns. In contrast, after the intravenous administration of 0.56 mg/kg of dipyridamole, R and A were increased and the A/R ratio was unchanged both in CAD patients and the control groups. Deceleration time, or the half time, was prolonged during both provocation tests in CAD patients, and these changes were transient and were restored within several min. Furthermore, they were noted more frequently than was the development of ST depression on ECG, or chest pain. These findings indicate that the transmitral blood flow velocity patterns obtained by pulsed Doppler echocardiography are useful for detecting transient myocardial ischemia, though they have limitations in diagnosing the extent of coronary artery disease.

To evaluate right ventricular (RV) function in severe left ventricular (LV) failure, we measured RV and LV ejection fractions (EF) in 18 patients with old myocardial infarction (OMI) and in 18 with dilated cardiomyopathy (DCM) using cardiac blood pool scintigraphy. In patients with OMI, RVEF was significantly greater in stage II LV failure than in stage III (functional class of the New York Heart Association, 47 +/- 8% and 28 +/- 12%, respectively: p less than 0.01), and this correlated well with exercise tolerance by bicycle ergometer and mean pulmonary artery pressure (r = 0.83 and r = -0.71, respectively). In patients with DCM, however, there was no correlation between RVEF and these indexes. After the oral administration of denopamine (beta 1 effector), both RVEF and LVEF increased in patients with OMI (35 +/- 13% to 45 +/- 12%, and 27 +/- 9% to 30 +/- 10%: p less than 0.01), but they did not change significantly in patients with DCM. These results indicate that RVEF in patients with OMI correlates well with subjective symptoms, exercise tolerance and RV afterload, but these correlations were not apparent in patients with DCM. We concluded that RV function in cases of severe LV failure has a different meaning between OMI and DCM.

Based on the fact that ultrasonic myocardial textural patterns are more irregular in the pathological myocardium than in the normal, evaluation of the myocardial tissue character was attempted in vivo using spectral analysis. Parasternal left ventricular long-axis echocardiograms were obtained from five patients with old myocardial infarction diagnosed by history, electrocardiography and coronary angiography. These echocardiograms were transferred to an image analyzer and digitized (256 x 256 x 8). The waveforms of the gray-scale-changes from the normal myocardium showed periodicity in each 8-pixel cycle, but those from the infarcted myocardium did not. To quantify pattern changes in gray-scale values in the ultrasound beam direction, spectral analysis was performed by the maximum entropy method (MEM). There were four peaks in the MEM spectra both in the normal and infarcted myocardia, but there was a great significance in these patterns: with high, steep peaks in normal MEM spectra, and low, blunt peaks in infarcted ones. By discriminatory analysis of these four peak values, normalized by the whole spatial frequencies as multivariate, the misclassification rate was 4.8-22.7% in anteroseptal infarctions and 5.0-20.0% in posterior infarctions. Thus, spectral analysis of the myocardial textural pattern has advantages for analyzing routine echocardiograms without corrections by any absolute ultrasonic references. Furthermore, the misclassification rate is so low that we are able to characterize myocardial tissue.

Right ventricular (RV) systolic and diastolic functions were assessed in patients with previous anteroseptal myocardial infarction to ascertain the influence of interventricular septal ischemia on RV function. Gated right ventriculography with continuous infusion of krypton-81 m was performed in 12 normal subjects and 28 patients with infarction but without significant stenosis of the right coronary artery. Furthermore, RV contractile reserve by postextrasystolic potentiation was evaluated by gated radionuclide ventriculography with 99mTc-HSA. The patients with anteroseptal infarction were divided into two groups by the presence or absence of three hours' redistribution in the septal region on exercise thallium-201 myocardial scintigraphy. Two indices of systolic function (ejection fraction and the peak ejection rate) and three indices of diastolic function (1/3 diastolic filling rate, the peak filling rate and time to the peak filling rate) were derived from the right ventricular time-activity curve and its derivative curve. There was no difference in systolic function among normal subjects and patients with or without redistribution. However, diastolic function was impaired only in the patients without redistribution. The RV contractile reserve in the patients without redistribution was less than in those with it. Thus, RV systolic function was maintained in the patients with anteroseptal infarction, but contractile reserve deteriorated only in severe septal ischemia. Similarly, diastolic function was maintained in mild septal ischemia, but impaired in severe septal ischemia. We concluded that RV systolic and diastolic functions are closely related to interventricular septal ischemia.

A case of a 59-year-old Asian male with several episodes of syncope and palpitation is reported. Electrophysiologic study disclosed that sustained ventricular tachycardia was induced by programmed electrical stimulation at the right ventricular apex. The electrogram in the left ventricular aneurysm showed delayed activities and the fastest depolarization. Entrainment was observed by faster pacing. Left ventriculography showed a large aneurysm and normal coronary arteries. Congenital left ventricular aneurysm is the most likely clinical diagnosis given the lack of past history of chest pain, myocarditis, cardiomyopathy, etc. Congenital aneurysm which presents as ventricular tachycardia is very rare, and has never been reported in an Asian. Medical management has thus far been successful.

A rare case of cough-induced tachyarrhythmia is described. The effectiveness of atropine sulfate, and worsening of the arrhythmia resulting from administration of digitalis, suggests that vagal reflex might be the mechanism responsible for the tachyarrhythmia.

A 54-year-old woman with the Noonan syndrome was admitted with congestive heart failure and a giant right atrial thrombus with atrial septal defect detected by two-dimensional echocardiography. The thrombus vanished on oral anticoagulant therapy with warfarin. The thrombus is considered to result from hemostasis in the right atrium due to congestive heart failure and to her specific skeletal characteristics. This report describes the first case of Noonan syndrome with right atrial thrombus.

A patient with click and late systolic murmur syndrome originating in the right side of the heart is described. Prolapse of the anterior tricuspid leaflet was demonstrated by subxiphoid two-dimensional echocardiography alone. Neither of the mitral leaflets showed any evidence of prolapse on the echocardiogram. The prolapsed anterior tricuspid leaflet and mild regurgitation were confirmed by right heart cineangiogram.

The feasibility of spatial color mapping vectorcardiography in diagnosing the site and extent of the old myocardial infarct was evaluated in comparison with 201T1 scintigraphy. Vectorcardiographic data made by Frank's technique were entered in the personal computer and the QRS complexes were plotted over 112 points crossing the latitude of each 20 (from 20N to 80S) degrees and longitude of each 20 degrees from 20W to 20E on the spherical body. Eight colors were assigned according to the direction of the QRS vector. To construct a territorial map, the apical, then, the septal, anterior, lateral, inferior and posterior portions were determined from the normal 201Tl scintigrams. Myocardial images obtained in the anterior, left anterior oblique and lateral projections were analyzed by the circumferential profile curve. Diagnostic specificity for infarction was greater than 60%, and especially high (90%) in the anterior, apical and lateral regions, but relatively low (50%) in the septal, inferior and posterior regions. Accuracies exceeded 64%. The infarcted areas assessed by spatial color vectorcardiography agreed with those assessed by 201T1 myocardial scintigraphy. Thus, spatial color vectorcardiography was simple and useful for diagnosing the site and extent of myocardial infarction.

A case of traumatic tricuspid insufficiency is presented. In the diagnosis of ruptured chordae tendineae of the tricuspid valve, two-dimensional echocardiography was an essential diagnostic procedure, while M-mode echocardiography showed no specific findings. Ruptured chordae tendineae of the tricuspid valve were confirmed at operation.

As an alternative to visual interpretations of subjects' angiograms, coronary arteries dilated by percutaneous transluminal coronary angioplasty (PTCA) were evaluated using cinevideodensitometry, and the results were compared with those obtained by the edge detection method. Coronary arteriograms were obtained in various projections and suitable frames were selected for analysis. The frames were transformed to digitized images (512 X 512 X 8 bits) with an image analyzer (MIPRON 1), and cinevideodensitometric and edge detection analyses were performed. Phantom models of various shapes were opacified with contrast medium and were used to test our system. The cineangiograms of 58 patients with ischemic heart disease, 28 of whom had underwent PTCA, were analyzed. A highly linear correlation was observed between the cross-sectional areas of the phantoms and the summed gray levels measured using cinevideodensitometry. Percent area stenosis evaluated by the two methods was accurate and reproducible in measuring the symmetrical stenosis models. However, for the model of asymmetrical stenosis, the measurement by the edge detection method differed according to various projections. Similar results were obtained measuring asymmetrical stenosis in the right coronary artery in vivo in various projections. Based on these experimental results, coronary stenoses dilated by PTCA were evaluated. Prior to PTCA, coronary arterial stenosis measured using the two methods closely approximated each other. However, following PTCA, there were discrepancies between the measurements by the two methods in six cases. This can be accounted for by asymmetrical changes in a luminal cross-section, which cannot be accurately assessed using the edge detection method in single plane projection. In conclusion, cinevideodensitometric measurements of relative coronary arterial stenosis were objective, accurate, and reproducible. According to cinevideodensitometric analysis, eccentric lesions can be measured using a single projection, and tracing arterial borders is unnecessary. It is a useful means in measuring quantitatively the degree of dilatation of coronary arterial stenosis accomplished by PTCA.

Seven patients with hypertrophic cardiomyopathy having midventricular obstruction (MVO) were examined using two-dimensional, conventional Doppler and color Doppler echocardiography to investigate intraventricular flow conditions. The controls were 35 patients with hypertrophic cardiomyopathy without MVO. All MVO patients had "hour-glass" LV cavities during systole, resulting from either hypertrophy at the midventricular level or hypertrophied papillary muscles, where systolic mosaic signals originated. Systolic peak flow velocities at the midventricle ranged from 2.5 to 4.2 m/s, proving the presence of a pressure gradient between the apex and the base of the LV. In fact, a pressure drop of 15-30 mmHg was demonstrated in four patients who underwent cardiac catheterization. These high velocity jet flows were not detectable at the midventricle in the control subjects. Peak ejection velocities in the outflow tracts were significantly lower in patients with MVO compared to those with hypertrophic cardiomyopathy and subaortic stenosis (129 +/- 29 vs 384 +/- 111 cm/s; p less than 0.001). As midventricular obliteration became severe, systolic jets at the midventricle increased in velocity. Waveforms changed from single- to double-peaked, and lasted until the isovolumic relaxation or the rapid filling phase beyond the second heart sound. Consequently, isovolumic relaxation waveforms at the midventricle using the apical approach changed the direction; from "the base to apex" to "the apex to base". An isovolumic signal away from the transducer was only observed in two patients without MVO. Diastolic color reversal and mosaic signals at the midventricle were also seen in five of the seven patients with MVO. Peak flow velocities in the rapid filling phase were significantly higher at the papillary muscle level than at the mitral valve level, indicating that MVO continues up to early diastole. It was suggested that MVO disturbs intraventricular flow dynamics during both systole and diastole. Color Doppler echocardiography is particularly useful in determining the site of obstruction and allows further evaluation by pulsed and continuous wave Doppler techniques to precisely measure pressure gradients. With routine, careful use of Doppler echocardiography, MVO may prove to be a more common entity than was previously believed.